Mutant Pts Research Articles

Outcome of Myelodysplastic Syndrome Patients with TP53 Mutation Treated with Hypomethylating Agents

▪IntroductionMyelodysplastic syndrome (MDS) patients (pts) with TP53 gene mutation (MT) have poor outcome. Recent studies suggested higher response rates to hypomethylating agents (HMA) among TP53 MT MDS pts. Those studies were limited by small number of TP53 MT. We compared the outcomes in a large cohort of TP53 MT MDS patients to those with wild type TP53 (WT) treated with HMA.MethodsWe identified MDS patients who underwent next generation sequencing (NGS) for TP53 MT who received hypomethylating agents in our MDS database. NGS included a panel of up to 54 genes with VAF threshold of 5% and minimum depth of coverage was 500X. We compared baseline characteristics between pts with TP53 MT and WT; chi square was used for categorical variables and t-test for continuous variables. Patients with low or intermediate-1 risk International prognostic scoring system (IPSS) were categorized as lower risk MDS (LR-MDS) and those with intermediate-2 or high risk IPSS as higher risk MDS (HR-MDS). The best response rate to HMA treatment was reported utilizing international working group criteria (IWG 2006); overall response was reported as HI+ which included complete response (CR), marrow CR, partial response and hematological improvement. Kaplan Meier estimates were used for overall survival (OS) where median OS was calculated from time of diagnosis, log rank test was used for comparison and cox regression analysis for multivariable analysis.ResultsWe identified 508 pts who underwent testing for TP53 MT and were treated with azacitidine or decitabine, 102 pts had TP53 MT. Table-1 summarizes baseline characteristics between the two groups. Among TP53 MT pts, 97 (95%) received azacitidine and 5 (5%) pts had decitabine as the first line HMA compared to 374(92%) treated with azacitidine and 32 (8%) with decitabine in TP53 WT pts as the first HMA (p= .3).Best response to HMA (HI+) was 41% (CR 18%) and 32% (CR 9%) among pts with TP53 MT and WT, respectively (p =.06). Among pts with LR-MDS the best response rates were 32% vs 25% (p=0.4) and in pts with HR-MDS the best response rates were 44% and 41% respectively in TP53 MT and WT (p=0.7). Median OS was 14 mo for TP53 MT MDS pts compared to 41 mo for TP53 WT pts (p<.005). The median OS was 45 and 65 mo. respectively in LR-MDS TP 53 MT and WT pts (p= 0.3). Among HR-MDS pts the median OS was 12 and 21 mo, respectively (p< .005).The median OS was 15 mo and 41 mo among pts with TP53 MT and WT who achieved CR, respectively (p <.005).For pts who underwent allogeneic hematopoietic stem cell transplant (AHSCT) the median OS was 16 mo for TP53 MT and 74 mo for TP53 WT (p=.008).After adjusting for age, R-IPSS, complex karyotype TP53 MT was independently associated with worse overall survival in HMA treated patients, HR 1.4 (p = .048).ConclusionsWe observed a trend for higher response rates among MDS pts with TP53 MT treated with HMA compared to TP53 WT. The median OS was inferior among TP53 MT MDS patients. The benefit of AHSCT among TP53 MT pts is not clear. The value of TP53 allele burden reduction and clearance with treatment and prior to AHSCT should be further investigated. [Display omitted] DisclosuresKomrokji:Novartis: Honoraria, Speakers Bureau; Celgene: Honoraria. Sallman:Celgene: Research Funding. Padron:Incyte: Honoraria, Research Funding. Sweet:Ariad: Consultancy, Speakers Bureau; Otsuka: Consultancy; Novartis Pharmaceuticals: Consultancy, Speakers Bureau; Karyopharm: Consultancy, Research Funding; Pfizer: Consultancy; Incyte: Research Funding. Lancet:Boehringer Ingelheim: Consultancy; Jazz Pharmaceuticals: Consultancy; Janssen: Consultancy; Erytech: Consultancy; Celgene: Consultancy; BioSight: Consultancy; Pfizer: Other: Institutional research funding, Research Funding; Bio-Path Holdings: Consultancy; Novartis: Consultancy.

Real World Data on Decitabine Treatment in 296 Patients with Acute Myeloid Leukemia: Outcome and Impact of TP53 Mutations

Real World Data on Decitabine Treatment in 296 Patients with Acute Myeloid Leukemia: Outcome and Impact of TP53 Mutations

Changing Patterns, and Clinical Correlates, of Mutations in Patients with Myelofibrosis over Treatment with Ruxolitinib or Hydroxyurea

Background. About half of patients (pts) with primary (PMF) and post-polycythemia vera/essential thrombocythemia MF (PPV/PET-MF) lose clinical response over prolonged treatment (3y+) with ruxolitinib. Both driver (JAK2, MPL, CALR) and non-driver mutations lack predictive power for the short-term (1y) response (Guglielmelli P, Blood 2015) although pts with >3 mutations are less likely to respond to ruxolitinib (Patel K, Blood 2016). Despite some reductions of Variant Allele Frequency (VAF) of driver mutations, molecular remissions induced by ruxolitinib are exceptional.Aims. To describe modifications of VAF of driver and non-driver mutations and changing patterns of mutation profile, and to correlate with response, in pts with MF receiving ruxolitinib or hydroxyurea.Methods. Sixty-three pts (38 PMF, 25 PPV/PET-MF) in active follow-up (FU) at CRIMM, Florence, were included; 17pts (15 PMF, 2 PPV/PET-MF) received hydroxyurea (HU) and 46 (23 PMF, 23 PPV/PET-MF) ruxolitinib. All pts were annotated for driver mutations and an additional panel of 24 “myeloid” genes by NGS. Paired samples of blood granulocytes were analyzed before starting HU/ruxolitinib therapy (baseline) and at the last FU available while on therapy. For the analysis, we recorded any modification of VAF, either decreasing or increasing, of at least 20% compared to baseline. Mutations were defined “acquired” in case of de novo detection (>2% VAF) and “loss” in case of disappearance of pre-exiting mutation at baseline.Results. The median follow-up from start of therapy was 2.9y for HU-pts and 3.4y Ruxo-pts. At last FU, among Ruxo-pts, 11 (23.9%%) had discontinued for failure, 1 progressed to AML and 16 (34.8%) died; in the HU group, all pts were still on treatment. JAK2 V617F mutation was found in 49 pts (77.8%; 22% HU, 76% Ruxo), CALR mut in 10 (15.9%; 40% HU, 60% ruxo), MPL mut in 1pt in each group; 3 pts were triple negative (2 HU, 1 Ruxo). The most frequent non-driver mutations were ASXL1 (33%), TET2 (20%), NFE2 (15%), ZRSR2 (12%), SRSF2 (8%).HU-pts: During treatment period, JAK2 V617F VAF increased in 2 pts (18%; +43% and +60% vs baseline) and decreased in 1 pt (-63%). No VAF changes were observed in CALR mut pts while MPL VAF increased by 47%. As regards non-driver mutation, VAF increased in 4 pts (31%; median +112%, range +22% to +168%) and remained stable in 13; acquisition of new mutation occurred in 5 pts (29%; 1 each for TET2, TP53 and NRAS and 2 CBL); no pts displayed mutation loss.Ruxo-pts: During treatment period, JAK2 V617F VAF increased in 6 pts (15%; median +27%, range +20% to +50%) and decreased in 9 (23%; median -38%, -21 to -62%). CALR VAF increased of 32% in 1 pt and was unchanged in 5 pts. In the MPL mut pt VAF decreased from 37% to 14%. As regards non-driver mutation, VAF increased in 26% of cases (median +103%) and decreased in 9 pts (23%; median -31%); in 3 pts, loss of 4 mutations was observed. Acquisition of new mutation was observed in 8 pts (17%; 1 each for EZH2, SF3B1, ASXL1, PTPN11, 2 NRAS and 3 KRAS).Response of symptoms or splenomegaly by the IWG-MRT criteria (Tefferi et al, Blood 2013) was achieved in 86% and 57% of pts after a median of 2.9mo and 13.1mo; of these, 13 (34%) and 12 (48%) pts lost clinical response after a median of 3.3y for symptoms and 2.8y for spleen volume reduction. ASXL1 mut at baseline was associated with a significantly lower likelihood of IWG-MRT-defined spleen response over prolonged treatment (32% vs 63% in the absence of ASXL1 mut; P=.040) . The probability of maintaining a spleen response at 2y in ASXL1 mut pts was 33% compared with 87% of unmutated pts. No mutation individually predicted for symptoms response or therapy-discontinuation. Acquisition of at least one mutation was associated with higher rate of discontinuation (36% vs 11% in those pts without clonal evolution, P=.048). Acquisition of 1 and >2 mutations correlated with higher rate of death (63% vs 29% and 45% vs 7%, respectively, compared to pts without clonal evolution).Conclusions. VAF changes of driver and non-driver mutations, as well as loss/acquisition of new non-driver mutations, occurred at comparable rate and with similar patterns in HU- and ruxolitinib-treated pts. Acquisition of new mutations while on ruxolitinib correlated with higher rate of discontinuation and death. DisclosuresVannucchi:Novartis: Honoraria, Speakers Bureau; Shire: Speakers Bureau. Bosi:Janssen: Honoraria; Celgene: Honoraria; Amgen: Honoraria; Takeda: Membership on an entity's Board of Directors or advisory committees.

P33.14 STK11/LKB1, KRAS Mutations and Immune-Related Adverse Events as Predictors of Response to Immunotherapy in Lung Cancer

Programmed death-ligand 1 (PD-L1) and tumor mutational burden (TMB) might help us predict responses to check point inhibitors (CPI), but we don’t have biomarkers that can predict resistance. Preliminary reports of mutations (mut) in STK11/LKB1 have suggested that they can confer CPI resistance. We investigated the role of STK1/LKB11, KRAS mut as markers of poor response to CPI in patients (pts) with non-small cell lung cancer (NSCLC). Additionally, we previously reported evidence that immune-related adverse events (irAEs) and its utility in identifying potential responders to CPIs. We investigated the role of STK11/LKB1 mut, KRAS mut and irAEs as predictors of response to CPIs in patients (pts) with non-small cell lung cancer (NSCLC). Pts with stage IIIB-IV NSCLC who were treated with CPI were prospectively tested (NGS) for KRAS and STK11/LKB1 mut were evaluated for progression free survival (PFS) and overall survival (OS). Log-rank tests were used to compare OS and PFS, chi-squared tests were used to compare 1-year survivals and proportions among different variables, and Kaplan-Meier survival curves were used to report OS and PFS. Furthermore, since Hispanics (H) are often not stratified in clinical trials, we sought to evaluate if incidence of irAEs and STK11 mut were similar between H and non-Hispanic (NH) pts. Of the 127 pts: 31 pts had an STK11 mut and 14 had an STK11+KRAS mut. Median age was 65y (27-88y). Males comprised 54% of the total pts and 24% of pts were H. STK11 mut pts had an inferior median PFS (5.6 vs 6.28 months; p-value 0.35) and significant difference in median OS (8.6 vs 12.1months; p-value 0.035) compared with STK11 wt pts. OS at 12 months was significantly higher in the STK11 wt group versus the STK11 mut group (73% vs 55%; p-value 0.03). Pts with STK11+KRAS mut had shorter OS and PFS than patients with wt (5m vs 11m and 3m vs 5m) but the differences were not significant, however the 1-year survival was better for wt pts compare with pts with both mutations (70% vs 40%) p-0.03. 48 pts experienced an irAE and 77 did not. The irAEs positive group had increased median PFS (9.5 vs 4.4 months; p-value 0.0047) and OS (14.2 vs 7.3 months; p-value < 0.001) compared to the irAEs negative group. OS at 12 months was 85% in the irAEs positive group compared to 60% in the irAEs negative group (p-value 0.001). There were no significant differences in incidence of irAEs and STK11/LKB1 mut status for H vs. NH pts. STK11/LKB1 mut pts and pts carrying KRAS mut concomitantly had shorter OS, PFS and 1-year survival compared with similarly treated pts with wt, however some numbers are not significant. CPIs treated NSCLC pts that experienced irAE had improved survival outcomes compared to those without irAEs. These findings are consistent with other studies that have reported STK11/LKB1 muts as a major genomic driver of primary resistance to CPI, and validate our previous report that described the utility of irAEs in predicting response to CPIs.

Results of Venetoclax and Azacitidine Combination in Chemotherapy Ineligible Untreated Patients with Acute Myeloid Leukemia with IDH 1/2 Mutations

Results of Venetoclax and Azacitidine Combination in Chemotherapy Ineligible Untreated Patients with Acute Myeloid Leukemia with IDH 1/2 Mutations

Quizartinib with Decitabine +/- Venetoclax Is Highly Active in Patients (Pts) with FLT3-ITD Mutated (mut) Acute Myeloid Leukemia (AML): Clinical Report and Signaling Cytof Profiling from a Phase IB/II Trial

Quizartinib with Decitabine +/- Venetoclax Is Highly Active in Patients (Pts) with FLT3-ITD Mutated (mut) Acute Myeloid Leukemia (AML): Clinical Report and Signaling Cytof Profiling from a Phase IB/II Trial

Comparison Of Adjuvant Versus Salvage Therapy Among IDH Mutant Low-Grade Glioma

Timing of postoperative management in low grade glioma (LGG) is controversial. We sought to evaluate the clinical outcomes among molecularly classified LGG patients (pts) treated with adjuvant (adj) versus (v) salvage treatment (salv). We included pts ≥ 18 yrs old at diagnosis of LGG (WHO grade II) from 1980-2018 with an IDH mutation (mut) and 1p19q data allowing for molecular classification. Pts in the adj group received immediate postoperative treatment (temozolomide [TMZ] and/or radiotherapy [RT]) prior to progression. Salv pts were initially observed then received TMZ and/or RT at disease progression. Endpoints were calculated from date of first surgical resection or biopsy, and included overall survival (OS) and next intervention free survival (NIFS), defined as the date of either surgery or treatment subsequent to adj or salv, or death. 296 IDH mut pts were included. Among the 168 pts with 1p19q codel, median follow up was 8.3 yrs (range, .03 – 26), median age was 43 yrs (range, 20-78), 57% were male, and 29% had GTR (gross total resection). 100 pts (60%) received adj (TMZ, 22%; RT, 65%; TMZ+RT, 13%), which was more likely in pts who were older, had larger tumors, or underwent biopsy alone (p<.05 for each). On univariable analysis (UVA), 5 yr NIFS for adj v salv was 70% (95% CI, 61-80%) v 83% (74-93%; p = 0.06), and 5 yr OS was 90% (84-97%) v 97% (93-100%; p<0.01), respectively. However, when adjusting for high risk factors associated with selection bias on multivariable analysis (MVA, Table), adj was not associated with either NIFS or OS as compared to salv. Among the 128 pts with 1p19q intact, median follow up was 6 yrs (range, 0.04 – 19), median age was 35 yrs (range, 19-66), 52% were male, and 41% had GTR. 49 pts (38%) received adj (TMZ, 29%; RT, 26%; TMZ+RT, 45%), which was more likely in pts who were older, had larger tumors, or underwent biopsy alone (p<.05 for each). On UVA, 5-year NIFS for adj v salv was 69% (95% CI, 56-85%) v 41% (31-56%; p<0.01), and 5-year OS was 85% (75-97%) v 91% (84-98%; p = 0.7), respectively. On MVA (Table), adj remained associated with improved NIFS compared to salv, but had no association with OS. Among IDH mut 1p19q codel pts, adj was not associated with improved NIFS or OS, suggesting initial observation followed by salv at progression is appropriate for this population. In contrast, among IDH mut 1p19q intact pts, adj was associated with improved NIFS, but not OS, supporting a more individualized postoperative management approach.Abstract 3689; TableMVAIDH mut 1p19q codelIDH mut 1p19q intactNIFSOSNIFSOSHR (95% CI)pHR (95% CI)pHR (95% CI)pHR (95% CI)pAdj v salv1.2 (0.8-1.9).421.3 (0.7-2.4).380.4 (0.2-0.7)<.010.9 (0.5-1.6).69Age ≥40 v <401.5 (1.0-2.3).072.1 (1.2-3.8).011.1 (0.7-1.9).631.3 (0.7-2.5).37Biopsy.16.02.09.18GTR0.7 (0.4-1.1).130.4 (0.2-0.8).011.0 (0.5-2.3).910.6 (0.2-1.6).34STR0.7 (0.4-1.1).090.6 (0.3-1.0).051.7 (0.8-3.6).131.3 (0.6-2.7).57Female v male0.8 (0.5-1.2).340.7 (0.4-1.2).230.5 (0.3-0.9).010.5 (0.3-0.9).04 Open table in a new tab

Ipilimumab (IPI) alone or in combination with anti-PD-1 (IPI+PD1) in patients (pts) with metastatic melanoma (MM) resistant to PD1 monotherapy.

10005 Background: PD1 induces long-term responses in approximately 30% of MM pts, however 2/3 are resistant (innate or acquired) and will require further treatment. A subset of these pts will benefit from IPI or IPI+PD1, but these pts are yet to be identified. We sought to determine; i) response rate (RR) and survival to IPI+/-PD1 after PD1 progression, and ii) clinical predictors of response and survival to IPI+/-PD1. Methods: MM pts resistant to PD1 and then treated with IPI+/-PD1 were studied. Demographics, disease characteristics and baseline blood parameters were examined. Univariate, multivariate and backward elimination technique analyses were performed to create predictive models of response and overall survival (OS). Results: Of 330 MM pts resistant to PD1 (median time to prog 2.9 months [0.5 – 42.3], 12% adjuvant, 88% metastatic; 70% innate, 30% acquired), 161 (49%) had subsequent IPI and 169 (51%) had IPI+PD1. Characteristics at start of IPI+/-PD1 were similar in IPI vs IPI+PD1 groups (stage M1D 27% vs 34%; elevated LDH 38% vs 40%), except IPI group had more ECOG ≥1 (60% vs 34%) and less BRAF mutation (mut) (21% vs 37%). Median follow-up from start of IPI+/-PD1 was 22.3 months (19.8 - 25.8); RR was 22%, higher in IPI+PD1 (31%) vs IPI (12%) (p &lt; 0.01). PFS and OS at 1 year were 20% and 48%, respectively; better with IPI+PD1 (27%/57%) vs IPI (13%/38%) (p &lt; 0.01). PD1 setting (adjuvant/metastatic) and response did not impact response to IPI+/-PD1. Most pts progressing on adjuvant PD1 had IPI+PD1 (88%) and RR was 33%. Neither the interval between PD1 and IPI+/-PD1 nor use of other drugs affected response to IPI+/-PD1. RR was similar in BRAF WT (23%) vs BRAF mut (RR 21%) pts. In BRAF WT pts, RR was higher with IPI+PD1 vs IPI (38% vs 9%, p &lt; 0.01), while RR was similar with IPI (24%) or IPI+PD1 (19%) in BRAF mut pts. One third of BRAF mut pts had BRAF inhibitors (BRAFi) prior to IPI+/-PD1 and lower RR (13%) vs those without BRAFi (RR = 25%, p &gt; 0.05). High grade (≥G3) toxicity (tox) was similar with IPI+PD1 (30%) or IPI (34%, p = 0.48), and was not associated with response. Stage III/M1A/M1B, normal LDH and treatment with IPI+PD1 were the best predictors of response (AUC = 0.69). These factors, in addition to sex (male), ECOG PS = 0, BRAF mut, progressed/recurred &gt; 3 months on PD1, and absence of bone mets were the best predictors of longer OS (AUC = 0.74). Conclusions: In pts resistant to PD1, IPI+PD1 has higher RR, longer survival, yet similar high grade tox than IPI alone. Predictive models of response &amp; survival will help select pts for IPI+/-PD1 after progressing on PD1.

Variation in genetic polymorphisms and gene expression of HLA-E to predict outcomes in metastatic colorectal cancer (mCRC) patients (pts) treated with first-line FOLFIRI/cetuximab: Data from the phase III FIRE-3 trial.

245 Background: HLA-E is an MHC Class I antigen which inhibits NK cell activity by binding to CD94 receptor. Overexpression of HLA-E on crc cells is associated with poor prognostic outcomes and has recently been associated with microsatellite instability. As cet enhances NK cell activity which is dependent on HLAE, this study aims to assess whether differences in HLAE gene expression and polymorphisms lead to different outcomes. Methods: Genomic DNA from blood samples of pts treated with first-line FOLFIRI-cetuximab (cet, n = 129) and FOLFIRI-bevacizumab (bev, n = 107) was genotyped through the OncoArray, a custom array manufactured by Illumina. Gene expression levels were measured from 102 tumor samples of pts in the cet arm by HTG EdgeSeq Oncology Biomarker Panel. PFS and OS outcomes were investigated for an HLAE genetic polymorphism, rs1264457, where G &gt; A leads to glycine &gt; arginine, where glycine has stronger affinity for NK cell receptor. Results: FOLFIRI/cet and FOLFIRI/bev cohort characteristics: median FU (29.1/26.7mo); PFS (12.8/11.5mo); OS (49.8/31.4mo); RAS WT (64%/62%) and RAS mut (15%/16%). Overexpression of HLAE was associated with poor OS (log2 &gt; 13, 30 vs 34 mo) in cet arm (P &lt; .05). No significant association was observed with PFS. Multivariable analysis showed that HLAErs1264457 carriers with any A allele (n = 65) had better PFS than pts with G/G genotype (n = 18) in RAS WT pts treated with FOLFIRI/cet (12.9 vs 12.3 mo; HR = 2.36; 95%CI = 1.14-4.88; p = 0.021). A non-significant trend of improved OS was seen among carriers of A allele than G/G genotype (56.2 vs 40 mo). These effects were not observed in Ras mut pts. No significance was observed in FOLFIRI/bev overall or FOLFIRI/bev RAS WT pts. Conclusions: Overexpression of HLAE leads to poor OS among pts treated with FOLFIRI/cet. Poor PFS was seen among pts treated with cet who are RAS wt carrying polymorphisms allowing for increased binding to NK cell receptor, which in turn enhances HLAE inhibitory function of NK cell lysis. Addition of mAb against HLAE, which have been shown to restore NK cell mediated cell lysis, needs investigation in this pt population.

Avelumab and cetuximab in combination with FOLFOX in patients with previously untreated metastatic colorectal cancer (MCRC): Final results of the phase II AVETUX trial (AIO-KRK-0216).

96 Background: Single agent PD-1/L1 inhibition is efficacious in MCRC patients (pts) with high microsatellite instability (MSI-H). For the vast majority of MCRC pts with MS stable (MSS) phenotype the role of immunotherapy remains undetermined. Methods: The single arm phase II AVETUX trial combined mFOLFOX6 and cetuximab with avelumab (10mg/kg day 1 from cycle 2 onwards) in RAS/BRAF wildtype (local lab) MCRC pts. Primary endpoint was 12 month progression-free survival rate. Secondary endpoints included overall response rate (ORR), tolerability, overall survival and translational research evaluating tissue including PD-L1 expression (tumour/immune cells) and serial ctDNA. Efficacy analyses were done by intention to treat (ITT). Results: Overall 43 pts were enrolled. Median age was 61 (range 29-82), 14 pts (33%) were female and 39 (91%) left sided. 30 pts (70%) had liver mets and 17 (40%) liver mets only. 2 pts were MSI-H, one MSI-low and 40 MSS. Besides immediate and otherwise unexplained fever in 4 pts treatment was well tolerated and avelumab was not associated with unexpected adverse events to standard FOLFOX/cetuximab. Central tissue review found 4 pts to be ineligible due to low frequent KRAS or BRAF mutation (15-31%). Thus, ITT included 39 pts. The ORR was 79.5%, including 6 complete (CR) and 25 partial responses (PR). Further 5 stable diseases were noted, thus disease control rate was 92.3%; 2 pts had progression and 1 was not evaluable. Early tumor shrinkage (ETS) rate (≥20% after 8 weeks) was 79.5% (1 CR, 27 PR and 3 SD with ≥20% - &lt; 30%). In MSI-H pts 1 PR and 1 SD and in the 3 low RAS mut pts 2 PR were noted. Panel sequencing was feasible with 153 mutations detected, showing an immediate ctDNA drop within 4 weeks of treatment, mirroring the high rate of early tumor response. Notably, the 4 pts with fever had a high T cell infiltration in the tumor. Final data including the primary endpoint and translational data will be presented at the meeting. Conclusions: The AVETUX regimen was feasible producing a high rate of responses in MSS pts mainly occurring within the first 8 weeks. The noted ORR/ETS of 79.5% warrants further evaluation in a randomized trial. Clinical trial information: NCT03174405.

MA13.03 Retrospective Study of Intrathecal Therapy for Non-Small Cell Lung Cancer (NSCLC) Patients with Leptomeningeal Carcinomatosis

Leptomeningeal carcinomatosis (LMC) is a devastating cancer-related neurological complication with poor prognosis. In EGFR-mutant (mut) NSCLC patients (pts), osimertinib achieves high penetration into cerebral-spinal fluid (CSF) and promising efficacy. However, for EGFR-mut T790M-negative pts treated with prior 1st- and 2nd-generation tyrosine kinase inhibitors (TKI) and for driver negative NSCLC pts, a combination of intrathecal therapy (IT) and systemic therapy (ST) seems to be an appropriate approach. Our purpose is to explore the clinical outcome of IT combined with ST among NSCLC with LMC depending on EGFR status. NSCLC pts with LMC treated with IT in our institution between 2010 and 2018 were retrospectively studied. After LMC diagnosis, intrathecal methotrexate (scheduled: 12mg twice weekly for 4 weeks, then 12mg weekly for 4 weeks) was given in combination with ST. A Kaplan-Meier survival analysis was performed for overall survival (OS) and progression free survival (PFS). A total of 39 pts were included. Patient’s clinical characteristics are summarized in table 1. EGFR status was 17 mut (del19: 11pts); 11 wild-type (wt) and 11 unknown (unk). LMC and NSCLC diagnosis were more likely to be synchronous in EGFR wt compared with EGFR mut. The median follow-up from LCM diagnosis was 10.2 months. At the time of this analysis, only 6 pts were alive. Thirty-two pts received ST in combination with IT, 18 (46%) pts chemotherapy (6wt/ 3mut/ 9unk), while 14 (36%) pts an EGFR TKI (1wt/ 13mut). Clinical response (improvement of neurological symptoms and/or KPS) was seen in 11 (65%) EGFR mut pts vs 2 (18%) wt pts (p=0.033). Median OS and PFS for the whole cohort were 23 weeks (95%CI, 8.1 to 37.9) and 10 weeks (95%CI, 7.1 to 12.8) respectively. Median OS was higher for EGFR mut pts compared to wt pts, 38 weeks (95%IC 13.6-62.4) and 19 weeks (95%IC, 4.06-33.9) respectively, however this difference was not statistically significant (p=0.36) probably due to lack of statistical power. Methotrexate-based IT given concurrently with systemic TKI may confer a higher clinical benefit and a trend toward OS benefit in NSCLC patients with LCM and EGFR activating mutations.

572P - Early tumour shrinkage (ETS), depth of response (DpR) and associated survival outcomes in patients (pts) with RAS wild type (WT) metastatic colorectal cancer (mCRC) classified according to Köhne prognostic category: Retrospective analysis of the panitumumab (Pmab) PRIME study

BackgroundKöhne prognostic category classifies mCRC pts as high, medium or low risk. Retrospective analysis of phase 3 trials found that Köhne category predicts survival, pts with BRAF mutant (MT) mCRC represent a separate (higher risk) category, and Pmab-based therapy improves survival vs chemotherapy alone in all four risk groups. We evaluated whether higher Köhne category and BRAF status predicts worse ETS and DpR, and assessed outcomes by ETS ≥30% vs<30% and DpR category. MethodsRetrospective analysis of RAS WT mCRC pts from the phase 3 PRIME study. ETS (% reduction in the sum of the longest diameters of measurable lesions at week 8) and DpR (maximum % change from baseline to nadir [shrinkage]; % change at progressive disease [no shrinkage]) were analysed according to Köhne category. DpR groups: <0%; 0–30%; 31–52%; 53–70%; 71–100%. BRAF MT pts were considered separately. Treatment arms were pooled and analysed separately.Table572P Median PFS and OS by ETS ≥30% vs<30% and by DpR category for each Köhne prognostic category and in pts with BRAF MT mCRC. P+F=Pmab+FOLFOX, F=FOLFOX aloneTableETS1,2High (n=74)Medium (n=236)Low (n=80)BRAF MT (n=46)Median PFS, months≥30%13.912.815.45.6<30%6.18.99.25.8Median OS, months≥30%24.632.540.79.6<30%11.719.323.610.4DpR3High (n=80)Medium (n=242)Low (n=86)BRAF MT (n=48)Median PFS, months<0%2.42.04.02.10–30%5.05.45.46.031–52%10.210.68.55.653–70%13.711.59.914.971–100%22.417.317.710.4Median OS, months<0%5.57.510.76.40–30%9.414.313.610.931–52%13.823.620.09.453–70%23.130.928.439.571–100%33.262.147.421.41Number of patients evaluable for ETS and DpR differ as patients with disease progression or death before week 8 did not have ETS data available;.2For ETS ≥30%: n=128 (P+F), n=83 (F); ETS <30%: n=88 (P+F), n=137 (F);.3For DpR <0%: n=17 (P+F), n=26 (F); 0–30%: n=42 (P+F), n=47 (F); 31–52%: n=52 (P+F), n=54 (F); 53–70%: n=57 (P+F), n=53 (F); 71–100%: n=65 (P+F), n=43 (F). Results436 pts receiving treatment (FOLFOX±Pmab) were analysed for ETS, 456 for DpR. The % pts in low-, medium-, high-risk and BRAF MT groups, respectively, achieving ETS ≥30% was 63.8%, 50.4%, 41.9% and 21.7%, and DpR 71–100% was 47.7%, 23.6%, 10.0% and 4.2%. Pts with ETS ≥30% vs<30% achieved longer PFS and OS, irrespective of Köhne category; this effect was not seen in BRAF MT pts (Table). In all Köhne groups, deeper DpR was generally associated with longer PFS and OS; this trend was noted in the BRAF MT group, but to a lesser extent. For all analyses, similar trends were seen in individual treatment arms (data not shown). ConclusionsHigher-risk categories predict worse ETS and DpR in pts with RAS WT mCRC. Irrespective of risk category, pts achieving ETS ≥30% vs<30% survived longer. Although patient numbers were small, prognosis in BRAF MT group was poor irrespective of ETS, but OS/PFS were longer with deeper DpR. Clinical trial identificationNCT00364013. Editorial acknowledgementDavid Cutler, PhD, CMPP of Aspire Scientific (Bollington, UK) and funded by Amgen (Europe) GmbH (Rotkreuz, Switzerland). Legal entity responsible for the studyAmgen (Europe) GmbH. FundingAmgen (Europe) GmbH. DisclosureA. Sartore-Bianchi: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Bayer; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Sanofi. M. Peeters: Honoraria (self), Research grant / Funding (self), Research grant / Funding (institution): Amgen; Honoraria (self), Research grant / Funding (self), Research grant / Funding (institution): Roche; Honoraria (self): Lilly; Honoraria (self): Merck Serono; Honoraria (self): Remedus; Honoraria (self): Sanofi-Aventis; Honoraria (self): Servier; Honoraria (self): Sirtex; Honoraria (self): Terumo. M. Geissler: Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Amgen; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Merck; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Roche; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Sanofi. J. Taieb: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Celgene; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self), Advisory / Consultancy: MSD; Honoraria (self), Advisory / Consultancy: Roche; Honoraria (self), Advisory / Consultancy: Sanofi; Honoraria (self), Advisory / Consultancy: Servier; Honoraria (self), Advisory / Consultancy: Sirtex. P. García-Alfonso: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self), Advisory / Consultancy: Roche; Honoraria (self), Advisory / Consultancy: Sanofi; Honoraria (self), Advisory / Consultancy: Servier. T. Price: Advisory / Consultancy, Travel / Accommodation / Expenses: Amgen; Advisory / Consultancy: Merck Serono; Advisory / Consultancy: Roche. P. Burdon: Shareholder / Stockholder / Stock options, Full / Part-time employment: Amgen (Europe) GmbH. Y. Zhang: Shareholder / Stockholder / Stock options, Full / Part-time employment: Amgen Inc. C. Koehne: Honoraria (self): Amgen; Honoraria (self): Bayer; Honoraria (self): Merck; Honoraria (self): Pfizer; Honoraria (self): Servier.

631P - PIK3CA mutation in metastatic colorectal cancer (mCRC): Association with clinico-pathological features and outcome

BackgroundMutations in PIK3CA, an EGFR downstream effector, and the subsequent activation of AKT pathway plays an important role in colorectal carcinogenesis. Considering the frequent co-occurrence of PIK3CA and RAS mutations, conflicting data exist about its impact on prognosis of mCRC patients (pts) and its predictive role to anti-EGFR therapy. However, PI3K inhibitors have been developed and are currently under investigation in mCRC. MethodsData from mCRC pts treated at Azienda Ospedaliero-Universitaria Pisana from 1 Jan 2005 to 31 Dec 2017, whose tumours had been analysed per clinical practice by MALDI-TOF MassArray were retrieved. Association between PIK3CA mutation and clinico-pathological features was analysed by χ2 test; OS curves were estimated with Kaplan-Meier method and compared by log-rank test. ResultsTumours from 90 (17%) out of 542 pts included in this analysis were PIK3CA mutated (mut), most of them in exon 9 (58.9%) or 20 (21.1%). Compared to PIK3CA wild-type (wt) tumours, mut ones were more often RAS mut (P=0.006), MSI high (P=0.008), and right-sided (P=0.0004). Among 53 pts for whom PIK3CA status was available on both primary tumours (PT) and metastasis, the concordance was 92.4%. PIK3CA mutations were not associated with OS (36.4 vs 35.9 mos, HR 1.17, 95%CI 0.85-1.62, p=0.3), with no difference among those affecting exon 9 and 20 (36.4 vs 27.5 mos, HR 0.77, 95%CI 0.39-1.54, p=0.44). In RAS/BRAF wt (N 188) and in RAS mut (N 299) subgroup, no difference in terms of OS was found between PIK3CA mut and wt pts (38.1 vs 44.4 mos, HR 1.22, 95%CI 0.60-2.48, p=0.55 and 27.5 vs 34.4 mos, HR 1.26, 95%CI 0.85-1.86, p=0.22, respectively), though PIK3CA mut had shorter OS. In BRAF mut subgroup (N 54), PIK3CA mut pts had longer OS compared to PIK3CA wt (not reached vs 14.4 mos, HR 0.37, 95%CI 0.16-0.85, p=0.09). Among 39 chemorefractory RAS/BRAF wt pts evaluable for response to an anti-EGFR agent, only 2 were exon 9 PIK3CA mut and achieved stable disease. ConclusionsPIK3CA mut tumours displayed specific clinico-pathological features and a strong concordance was found between PT and paired metastases. Interestingly, a different impact on prognosis of PIK3CA mutation in RAS/BRAF wt, RAS mut or BRAF mut mCRC pts was observed and deserves validation. Legal entity responsible for the studyThe authors. FundingSupported by ARCO (Associazione Ricerca e Cure in Oncologia) Foundation. DisclosureAll authors have declared no conflicts of interest.

1055P - Clinical impact of molecular profiling of cervical cancer (CC) patients (pts) in a dedicated phase I (P1) unit

BackgroundMetastatic CC prognosis remains poor. Molecular characterisation (MC) allows better understanding of the mutations (mut) driving carcinogenesis or treatment resistance. We report the cervical tumour MC of pts in a P1 unit and its clinical implications. MethodsCC pts referred to the P1 unit of The Royal Marsden Hospital from 2011-18 underwent tumour molecular profiling using OncoCartaTM (Sequenom), TruSeq® Cancer Amplicon (Illumina), GeneReadTM custom DNA damage (Qiagen) or FoundationOne® panel. Retrospective data was extracted from electronic medical records. ResultsOf the 37 pts (median age: 34.7 years) analysed, 45.9% had squamous histology, and 37.8% were FIGO stage 2 at diagnosis; 34 different pathogenic mut were identified with 70.3% of pts having mut. PIK3CA mut were the most common (32.4%), followed by KRAS (13.5%), APC (8.1%), TP53 (8.1%), PTEN (5.4%), KDR (5.4%), ATM (5.4%), STK11 (5.4%) and BRCA1 (5.4%). 40.5% (15/37) patients had a potentially actionable mutation. Median overall survival (mOS) was 36 months (mo) in study population, 33mo in KRAS mut, 40mo in PIK3CA mut, 52mo in APC mut and 40mo in the mut-negative group; however, this difference was not statistically significant. In the KRAS mut group, 60% were adenocarcinoma and 40% adenosquamous. All KRAS mut pts had FIGO stage 2/3 at diagnosis. 80% had visceral metastasis when referred to the P1 unit; whereas in the PIK3CA mut group, tumour histologies were 33.3% squamous, 25% adenocarcinoma, 25% adenosquamous, 8.3% mucinous, 8.3% uncommon histologies. In the PIK3CA mut group, 75% were stage 1/2 at diagnosis, and 41.6% had visceral metastasis when referred. 5.4% (2/37) of pts were allocated to a P1 trial based on the finding of a PIK3CA mut with a mOS of 40mo compared to 36mo for the total population (p=0.6). One pt received an AKT inhibitor (i) but developed progressive disease (PD) after 3 cycles; the other received a PI3K i with PD after 4 cycles. ConclusionsOur study corroborates existing knowledge of the association between KRAS mut and adenocarcinoma histology in CC which confers worse prognosis. The high rate of potentially actionable mut indicates the increasing scope for targeted treatment trials in CC, thus prompting early MC which may improve pt allocation to P1 trials. Legal entity responsible for the studyThe Institute of Cancer Research and The Royal Marsden Foundation Trust. FundingThe Institute of Cancer Research and The Royal Marsden Foundation Trust. DisclosureS. Banerjee: Honoraria (self), Research grant / Funding (institution): AstraZeneca; Honoraria (self), Honoraria/reimbursement: Tesaro; Honoraria (self), Honoraria/reimbursement: Clovis; Honoraria (self), Honoraria/reimbursement: Merck Serono; Honoraria (self), Honoraria/reimbursement: Nucana; Honoraria (self), Honoraria/reimbursement: Immunogen; Honoraria (self), Honoraria/reimbursement: Seattle Genetics; Honoraria (self), Honoraria/reimbursement: Roche; Honoraria (self), Honoraria/reimbursement: Gamamabs. J.S. de Bono: Honoraria (self), Non-remunerated activity/ies: Astellas Pharma; Honoraria (self), Research grant / Funding (institution), Non-remunerated activity/ies: AstraZeneca; Honoraria (self): Genentech/Roche; Honoraria (self): Pfizer; Honoraria (self), Non-remunerated activity/ies: Sanofi; Honoraria (self): Bayer; Honoraria (self): Boehringer Ingelheim; Honoraria (self): Merck Serono; Honoraria (self): Merck Sharp & Dohme; Non-remunerated activity/ies: Genmab; Non-remunerated activity/ies: GlaxoSmithKline; Non-remunerated activity/ies: Orion Pharma GmbH; Non-remunerated activity/ies: Qiagen; Non-remunerated activity/ies: Taiho Pharmaceutical; Non-remunerated activity/ies: Vertex; Licensing / Royalties, Royalties paid to Institution, no personal income: Abiraterone Rewards to Inventors; Licensing / Royalties, Royalties paid to Institution, no personal income: PARP inhibitors and DNA repair defects. U. Banerji: Honoraria (self), Precision Medicine - Advanced Prostate Cancer Meeting, London UK -30/11/2018: Astellas; Honoraria (self), Advisory / Consultancy, Translational Clinical Oncology Advisory Board, London, 24/07/2018; FIH Precision Oncology SAB, Frankfurt, 10-11/11/2015: Novartis; Advisory / Consultancy, Clinical Advisory Board, London, 19/03/2018 and 12/02/2015: Karus Therapeutics; Advisory / Consultancy, GI Advisory Board, London, 2/12/2017: Phoenix ACT; Honoraria (self), European Digestive Oncology Research Forum, London, 27-28/11/2017: Eli Lilly; Honoraria (self), KOL ERK Workshop, New Orleans, 17/04/2016; HSP90 Workshop, Washington DC,8/03/2014: Astex; Honoraria (self), AUY922 meeting, New Jersey, USA,12/02/2015: Vernalis; Research grant / Funding (institution), ONX-0801:Funding for investigator-initiated Phase I trial: Onyx Pharmaceuticals; Research grant / Funding (institution), ONX-0801:top-up funding for investigator-initiated phase I trial: BTG International; Research grant / Funding (institution), RAF/MEK: funding for investigator-initiated phase I trial: Chugai; Research grant / Funding (institution), TAX-TORC: funding for investigator-initiated phase I trial: AstraZeneca; Research grant / Funding (institution), FRAME: funding for investigator-initiated phase I trial: Verastem. A. Minchom: Travel / Accommodation / Expenses: Loxo; Advisory / Consultancy: Janssen; Honoraria (self): Faron; Speaker Bureau / Expert testimony: Bayer Media Event. J. Lopez: Advisory / Consultancy: Genmab; Advisory / Consultancy: Novartis; Research grant / Funding (institution), Travel / Accommodation / Expenses: Roche/Genentech; Research grant / Funding (institution), Travel / Accommodation / Expenses: Basilea. All other authors have declared no conflicts of interest.

PS968 GENETIC LANDSCAPE OF FLT3‐MUTATED ACUTE MYELOID LEUKEMIA (AML) PATIENTS TREATED WITHIN THE RATIFY TRIAL: CALGB 10603 (ALLIANCE)

Background:Recently, the oral multi‐targeted FLT3 inhibitor midostaurin (M) was approved in combination with standard chemotherapy for treatment of FLT3 mutated (FLT3 mut) AML. In the international RATIFY (NCT00651261) trial, M significantly improved overall (OS) and event‐free survival (EFS) compared to placebo, thus defining a new standard of care in this AML subset (Stone RM et al. NEJM 2017).Aims:To comprehensively delineate the mutational profile of FLT3 mut AML patients (pts) treated within the RATIFY trial and to correlate genetic findings with clinical outcome.Methods:Targeted sequencing was performed of 262 candidate genes including 20 kinases targeted by M (M kinome, MK) using SureSelectXT (Agilent). Diagnostic specimens were available from 475 (66%) of 717 FLT3 mut pts. Sequencing was carried out on a HiSeq (Illumina). FLT3 mutation (mut) status was available for all 475 pts [tyrosine kinase domain (TKD: 24%); internal tandem duplication (ITD: 76%)]; cytogenetic data were present for 371 pts (78%).Results:Overall, 1813 mut were identified (median coverage: 978x) with an average of 3.8 mut per pt (FLT3 strata; TKD: 3.9; ITD: 3.8). Mut ≥5% were found for NPM1 (61%), DNMT3A (39%), WT1 (21%), TET2 (12%), RUNX1 (11%), NRAS (11%), PTPN11 (9%), ASXL1 (8%), IDH1 (8%), IDH2 (7%; #R140 only), and SMC1A (6%). In contrast, MK mut were rare events (7% in total) with KIT (2%), MAP3K11 (1%), and NTRK3 (1%) being most frequently mutated. First, we categorized all pts to the recently defined 11 genomic AML classes (Papaemmanuil E et al. NEJM 2016). The majority of cases fell into two classes, namely the NPM1 (N; 60%), and the chromatin‐spliceosome (C‐S; 15%) classes. Core‐binding factor (CBF) AML [t(8;21) and inv(16)] accounted for 4% only; in 13% no class‐defining lesion was identified (no class, NC). In terms of clinical outcome, CBF and N classes showed better response to induction therapy than C‐S and NC (Complete remission (CR) rate: 83%, 70%, 60%, 38%; p = .0005), which translated into significantly superior OS (p &lt; .0001) and EFS (p &lt; .0001) for CBF and N compared to C‐S and NC. When stratified according to treatment arm, addition of M resulted in improved OS in N, C‐S, as well as NC, irrespective of the genetic background. Next, we categorized pts according to the 2017 European LeukemiaNet (ELN) genetic risk groups (Döhner H et al. Blood 2017). CR rate was inferior within the adverse (ADV) and intermediate (INT) as compared to the favorable (FAV) risk group (52%, 62%, 74%; p = .002) translating into significantly shorter EFS (p &lt; .0001) and OS (p &lt; .0001) in INT and ADV than FAV. Of note, M showed consistent beneficial effects across all ELN risk groups. When comparing pts with MK gene mut vs. pts with wildtype MK, no differences in outcome were observed. Within the group of MK mut pts there was no benefit for M; however, the results have to be interpreted cautiously due to the small sample size.Summary/Conclusion:In this comprehensive targeted sequencing approach of 475 FLT3 mut AML pts treated within the RATIFY trial, remarkable differences in the underlying AML genomic classes were found. Predominant classes were N, C‐S, CBF, showing significant differences with regard to response to treatment and survival. Of note, treatment with M showed beneficial effects across all genomic AML classes. In addition, M was associated with a better outcome in all 2017 ELN risk categories, demonstrating a consistent benefit of M across various genetic AML subgroups.Support:U10CA180821, ‐ U10CA180882, U24CA196171; Novartis; https://acknowledgments.alliancefound.org

Association of PIK3CA mutations (mut) with immune engagement and clinical benefit from immunotherapy in microsatellite stable (MSS) colorectal cancer (CRC) patients (pts).

3604 Background: PI3K pathway alterations, PIK3CA mut or PTEN loss, are known to modulate anti-tumor immune microenvironment. MSS CRC pts respond infrequently to immunotherapy, suggesting the presence of a rare MSS immunogenic subset. We investigated the immune repertoire and outcomes on immunotherapy trials in PIK3CA mut MSS CRC pts. Methods: Immune infiltrates and checkpoints were evaluated using quantitative immuno-histochemistry (IHC) on primary CRC. Mutations were assessed by next generation sequencing. PIK3CA mut neoepitopes and HLA allele affinities were predicted using NetMHC 4.0 Server. Outcomes of MSS CRC pts enrolled in 7 immunotherapy trials were assessed. Clinical benefit (CB) was defined as CR, PR or SD of 24 weeks. Time to progression (TTP) was calculated using Kaplan-Meier Method. PIK3CA mut vs wild type (wt) groups were compared using Mann-Whitney U, Fisher’s exact, or Log-Rank tests as appropriate. Results: PI3K alterations were present in 14/40 MSS CRC pts in IHC cohort (7 PIK3CA mut, 33 wt; 7 PTEN loss, 33 intact). The center of PIK3CA mut MSS CRC had higher median densities of CD3+ cells [1112 (IQ range 865-1421) vs 435 (300-744) cells/mm3; P=0.037] and CD8+ cells [554 (331-1200) vs 185 (60-473) cells/mm3; P=0.037] as compared to PIK3CA wt tumors. Intratumoral immune infiltrates did not differ by PTEN IHC staining in MSS CRC. PD-L1 H-scores were also higher in PIK3CA mut MSS CRC [85 (34-114) vs 29 (11-60); P=0.01]. Several activating PIK3CA mut (E542K, E545K, H1047R) were predicted to generate true neoepitopes with high binding affinity to common HLA types. Indeed, among MSS CRC pts enrolled in 7 immunotherapy trials, half (4/8) of PIK3CA mut pts derived CB as compared to 3/35 (8.6%) PIK3CA wt pts (P=0.015). PIK3CA mut pts had trend towards longer TTP (3.8 months in mut vs 2.1 months in wt; P=0.08). CB or TTP did not differ by colon sidedness, monotherapy / combination therapy, number of mut, or mut in other key genes ( APC, SMAD4, TP53, KRAS, NRAS or BRAF). Conclusions: PIK3CA mut MSS CRC are associated with increased cytotoxic T cell infiltration, higher PD-L1 expression, and greater clinical benefit from immunotherapy. Further investigation of immunotherapy outcomes in the context of neoepitope-HLA allele interaction may help identify a subset of PIK3CA mut MSS CRC pts who are likely to benefit from immunotherapy.

Impact of KRAS allele subtypes and concurrent genomic alterations on clinical outcomes to programmed death 1 axis blockade in non-small cell lung cancer.

9082 Background: Immune checkpoint inhibitors (ICI) treatment can result in durable responses for KRAS-mutant (mut) non-small cell lung cancer (NSCLC). The impact of KRAS allele subtypes and concurrent genomic alterations on ICIs efficacy is unknown. Methods: We collected clinicopathologic and genomic data from patients (pts) with advanced NSCLC treated with programmed death (PD)-1 axis inhibition at the Dana-Farber Cancer Institute. We evaluated outcomes to ICIs according to KRAS mut alleles and concurrent STK11 and KEAP1 mut. Results: Of 617 ICI-treated NSCLCs, 181 (29.3%) had KRAS mut. Median TMB (mTMB) and median PD-L1 tumor proportion score (TPS) were similar between KRAS mut and KRAS wild type (wt) tumors. Among tumors with KRAS codon 12 mut, mTMB was higher in G12V (n = 37, 12.2 mut/Mb) compared to G12C (n = 84, 11.4 mut/Mb), G12D (n = 20, 9.4 mut/Mb) and G12A (n = 13, 10.1 mut/Mb), P = 0.05. Tumors with KRAS transversions (Tv) (n = 156) had higher mTMB compared to those with KRAS transitions (Ti) (n = 25) (10.9 vs 7.6 mut/Mb, P = 0.03). Median PD-L1 TPS was similar across KRAS mut alleles. Pts with KRAS G12V had longer median progression-free survival (mPFS) (5.5 vs 2.7 months, HR:0.62 [95%CI:0.40-0.96], P = 0.03) and overall survival (mOS) (17.5 vs 9.7 months, HR:0.62 [95%CI:0.36-0.99], P = 0.05), compared to non-G12V. Pts with KRAS Tv had longer mPFS and mOS compared to pts with Ti (mPFS: 3.4 vs 2.0 months, HR: 0.58 [95%CI:0.37-0.92], P = 0.02; mOS: 10.9 vs 5.4 months, HR:0.59 [95%CI:0.35-0.99], P = 0.048). Clinicopathologic features and STK11/KEAP1 mut were balanced across all KRAS mut alleles. Among KRAS mut pts, those with KEAP1 (n:52) and STK11 (n:50) concurrent mut had shorter mPFS (KEAP1 mut 1.8 vs. KEAP1 wt 4.1 months, HR: 0.55 [95%CI:0.38-0.80], P = 0.002; STK11 mut 1.8 vs STK11 wt 4.6 months, HR:0.46 [95%CI:0.32-0.67], P &lt; 0.0001) and mOS (KEAP1 mut 4.8 vs KEAP1 wt 15.1 months, HR: 0.51 [95%CI:0.34-0.76], P = 0.001; STK11 mut 4.8 vs STK11 wt 13.6 months, HR:0.51 [95%CI:0.34-0.76], P = 0.001). KEAP1 and STK11 mut did not impact outcome in KRAS wt pts. Conclusions: KRAS allele subtypes and concurrent genomic alterations impact ICI efficacy in NSCLC.

Comparative Genomic and Expression Analysis of Chronic and Blast-Phase Cells in Patients with Myeloproliferative Neoplasms

Background. Progression to acute myeloid leukemia (sAML) occurs in 20% of myelofibrosis (MF) and 10% of polycythemia vera (PV) or essential thrombocythemia (ET). sAML has dismal outcome with median survival of <6 months. We recently reported that a restricted set of mutations predict for leukemic transformation in MPN (Vannucchi AM, Leukemia 2013; Tefferi A, Blood Adv. 2016). However, the molecular mechanisms underlying transformation to sAML are poorly characterized, in particular the relationships between the clones establishing the chronic phase and the one dominating the leukemic phase.Aim. To study clonal heterogeneity and clonal progression in the leukemic transformation of MPN we performed whole exome (WES) and trascriptome (RNAseq) sequencing of paired samples (chronic (CP)/blast phase(BP).Patients and Methods. WES and RNAseq was done on CD34+ or blast cells of 12 paired samples from 5 PMF, 3 PET-MF, 1 PPV-MF, 3 ET pts who transformed to sAML. In addition, a myeloid neoplasm-relevant 34-gene panel was used for target NGS sequencing of paired samples plus an additional 23 samples collected from MPN pts at leukemic phase (15 PMF, 3 PET-MF, 3 ET, 2 PV).Results. In the entire series, 20 pts (57%) were JAK2 V617F mutated at CP, 8 CALR (23%; 6 type-1 and 2 type-2) and 7 (8.6%) MPL mut, while 4 (11.4%) were triple-negative. JAK2 variant allele frequency (VAF) declined by ≥50% (n=3; 15%) or became undetectable (n=4; 20%) whereas 3 heterozygous pts (15%) became homozygous at the time of BP. One of the 8 CALR mut cases halved its VAF, whereas no meaningful VAF changes were observed in MPL mut pts. The most frequent mutated genes detected by NGS at BP, other than driver mutations, were ASXL1 (51.4%), RUNX1 (37.1%), TET2 (17%), SRSF2 (16%), IDH1 (14%), TP53 (14%), NRAS (14%), FLT3 (14%), U2AF1 (11%) and KRAS (11%); three (8%) cases were mutated for EZH2DNMT3A, CBL and PTPN11, 2 cases for IDH2, SH2B3, SF3B1 IKZF1, SETBP1 and ZRSR2, and 1 case for ABL1, ATV6, BRAF and ARID1A. There were also 5 CEBPA-mutated pts, 3 of which, unlike none of 27 CEBPA-mutated de novo AML, showed an in-frame 6-bp duplication polymorphism (p. P196_197insHP) reported in 20-40% of all de novo AML and <1% of healthy population (rs762459325). Compared to the CP of the 12 paired samples, 10 pts (83%) acquired novel mutations, 3 of which acquired ≥3 variants. RUNX1 and ASXL1 were those with the highest number of acquisition (n=7 and 5, respectively). Conversely, loss of variants was observed only in ASXL1 (n=3).By WES analysis, on average 60.000 variants per paired sample unique to the BP compared with CP were identified. However, no recurrent abnormalities were found in the 12 paired samples outside the above listed mutations found by target sequencing. For RNAseq analysis, transcripts were annotated according to UCSC hg19 for a total of 25,369 genes. We found large transcriptional differences between CP and BP with 129 transcripts differentially expressed (23 up- and 106 down-regulated) and 4,155 isoforms (2,120 up- and 2,035 down-regulated). Among the most abnormally expressed transcripts we selected 8 genes (5 down-regulated: LCN2, PDGFB, PRTG, CRISP3, PF4; 3 up-regulated CDKN2, SH2D1A and LIN28) for validation by QRT-PCR based on the extent of differential expression. PF4 and CDKN2 were confirmed to be down-regulated and over-expressed in BP, respectively (P<0.0001). Analysis of RNA-seq data for fusion genes revealed 10 fusion genes acquired during BP; however, only 3 of them were confirmed by Sanger sequencing (2 cases of BCR-ABL, 1 case of KMT2A- MLLT3 and 1 case of CBFB-MYH11). Pathway analysis included Gene Set Enrichment Analysis and Signaling Pathway Impact Analysis. Six pathways were significantly deregulated in BP compared with CP: Mitotic Spindle (P<0.0001); Androgen response (P=0.004); TGF-beta signaling (P=0.04); Apoptosis (P=0.03); PI3K-AKT-MTOR signaling (P=0.04); Reactive Oxygen Species- Pathway (P=0.03).Conclusions. Comprehensive comparative analysis of genomic and RNA abnormalities acquired in the transition from CP to BP in MPN has not been previously reported. Our data indicate that BP is associated with significant changes in mutation complexity and RNA expression, overall affecting different intracellular pathways whose further characterization might help to identifying potential targets for therapy. DisclosuresNo relevant conflicts of interest to declare.

Abstract 656: Distinct pattern of alterations in TP53 mutated/deleted and wild-type high risk acute myeloid leukemia (AML) patients: Identification of new "targetable" genes/pathways

Abstract Background: The reported TP53 mutation rate in AML is relatively low (7.5-9%, TCGA) and predict a poor prognosis. In 2017 European LeukemiaNet recommended for AML to add TP53 mutations (muts) in the risk stratification. Specific chromosomal aneuploidies are closely correlated with each other and with presence of TP53 muts. Aims: Considering that TP53 mut AML pts have HRisk and no target therapy, we would identify genes/pathways that are mainly CNA-affected (Copy Number Alteration) in the mut TP53 group compared to the wt one. Patients and Methods: 358 adult AML pts were screened for TP53 muts. 219/358 samples were genotyped with SNP arrays. CNA analyses were performed using two software to confirm or integrate karyotype data. Fisher's exact test and pathway enrichment analyses were performed. Results: We detected TP53 muts in 52/358 (14.5%) pts. Mostly (34/52) of the TP53 mut pts (65.4%) had complex karyotype. TP53 alterations were significantly associated with poor outcome (OS and EFS p&amp;lt;0.0001). On TP53 locus, we matched CNA and cytogenetic analyses results. We identify 23 mutated pts that were also deleted (alt) and 7 pts that presented only a TP53 deletion. Therefore 44.2% of mut pts present a concomitant deletion. OS of TP53 alt pts is not statistically inferior respect to mut pts (p=0.77). Comparing 52 TP53 alt and 167 TP53 wt pts CNAs results that: a) chrs significantly altered are 5q and 17p but there are also highly significant »Spot» losses (7q, 20p, 21q, 22q, 19q); b) TP53 CNAs are present in the 44% of TP53 alt vs 0.63% of wt pts; c) over 9013 genes are differentially involved (mainly in Loss, 93.1%); d) that pathway categories mainly enriched are Immune System, Metabolism, Signal Transduction; e) TP53 deletion seems less deleterious (in terms of OS) than TP53 mutation or TP53 alt; f) some TP53 protein-protein interacting genes like SKP1, CDK5, PPP2CA, CSNK1G3 and STAT5B are highly altered and drug target. Conclusions: TP53 muts with or without deletion were predicted to be deleterious and significantly correlated with worse prognosis. For these reasons, TP53 mutation/deletion screening should be recommended. Different alterations groups have been identified in terms of genes, pathway enrichment and protein-protein interaction between ALT and Wt; needed a deeper investigation to better focus on few targetable nodes of this complex network. Three groups comparison (Wt,TP53 Mut,TP53 MutDel pts) analyses would give us the opportunity to select a more appropriate target therapy in these pts. Different pattern of alterations in alt and wt groups have to be deeper investigated to discover targetable nodes of this complex network. ELN, AIL, AIRC, PRIN, Regione-Università 2010-12 (L. Bolondi), FP7 NGS-PTL; HARMONY. Citation Format: Anna Ferrari, Eugenio Fonzi, Andrea Ghelli Luserna Di Rorà, Maria Chiara Fontana, Marco Manfrini, Carmen Baldazzi, Cristina Papayannidis, Vincenza Solli, Antonella Padella, Giovanni Marconi, Stefania Paolini, Valentina Robustelli, Enrica Imbrogno, Eugenia Franchini, Perricone Margherita, Maria Chiara Abbenante, Giorgia Simonetti, Nicoletta Testoni, Emanuela Ottaviani, Michele Cavo, Giovanni Martinelli. Distinct pattern of alterations in TP53 mutated/deleted and wild-type high risk acute myeloid leukemia (AML) patients: Identification of new "targetable" genes/pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 656.

Somatic DNA mutations, MSI status, mutational load (ML): Association with overall survival (OS) in patients (pts) with metastatic colorectal cancer (mCRC) of CALGB/SWOG 80405 (Alliance).

3504 Background: CALGB 80405 was a randomized phase III trial that found no difference in OS in first-line mCRC pts treated with either bevacizumab (Bev) or cetuximab (Cet). Primary tumor DNA from 361 pts, including KRAS mutant (mut) pts, has been profiled for somatic gene mutations/ML/MSI to discover molecular markers of OS. Methods: Mutations in 11 genes were determined by PCR, MSI by microsatellite analysis, and ML by next-generation sequencing (FoundationOne). Cox proportional hazard models are used, stratified by prior XRT and +/- adjuvant chemotherapy; adjusted by age, race, gender, synchronous vs. metachronous, liver metastases, sidedness, all RAS. Results: BRAF: Mut pts had shorter OS than wild-type (wt) pts (HR 1.92, 95% CI 1.34,2.75; p&lt;0.001); HR 1.65 (1.09,2.50) after adjusting for sidedness (p 0.022). In mut pts longer OS is observed in Bev arm vs. Cet arm (p 0.041); in wt pts no arm difference is observed (p 0.291, table). MSI: OS does not differ between MSI-H and MSI-S pts (HR 0.78 [0.40, 1.52], p 0.450). In MSI-H pts longer OS is observed in Bev arm vs. Cet arm (p 0.002); in MSI-S pts no difference is observed (p 0.305, table). ML: Hypermutated MSI-H pts are excluded. In a subset of 205 pts, pts with ML&gt;5 (N=93) have longer OS than pts with ML≤5 (N=112) (HR 0.65 [0.42,1.00], p 0.048). In Bev arm higher ML confers longer OS than lower ML (HR 0.85 [0.80,0.96], p 0.004); in Cet arm no difference is observed (HR 0.99 [0.90,1.09], p 0.862). Conclusions: BRAF is a strong negative prognostic factor in mCRC, even when sidedness is taken into account. ML is a novel marker for further evaluation. The effect of Bev and Cet in either BRAF mut or MSI-H pts should be tested in larger datasets. Updated results from more screened samples will be presented. [Table: see text]