SP142 Assay Research Articles

Avelumab first-line (1L) maintenance for advanced urothelial carcinoma (UC): Analysis of clinical and genomic subgroups from the JAVELIN Bladder 100 trial.

4520 Background: In the phase 3 JAVELIN Bladder 100 trial, avelumab 1L maintenance + best supportive care (BSC) significantly prolonged overall survival (OS) vs BSC alone in patients (pts) with advanced UC that had not progressed on 1L platinum-based chemotherapy (HR, 0.69 [95% CI: 0.56, 0.86; 1-sided P= 0.0005]). We report post hoc analyses in previously unreported clinical and genomic subgroups. Methods: In JAVELIN Bladder 100 (NCT02603432), eligible pts had unresectable locally advanced or metastatic UC without progression after 4-6 cycles of 1L gemcitabine + cisplatin or carboplatin, and were randomized to receive avelumab + BSC (n = 350) or BSC alone (n = 350). The primary endpoint was OS, in all randomized pts and pts with PD-L1+ tumors (Ventana SP263 assay). In this exploratory analysis, we analyzed OS in disease stage and site subgroups, in pts with PD-L1+ tumors who received 1L gemcitabine + carboplatin, and in genomic subtypes (RNAseq whole-transcriptome profiling of tumor tissue) defined using data from The Cancer Genome Atlas (TCGA 2017). Interaction tests were not performed. Results: Prolonged OS was observed in the avelumab + BSC arm vs the BSC alone arm in pts with upper or lower tract tumors, metastatic or locally advanced (LA) and unresectable disease (prior to chemotherapy), and lymph node-only disease post-chemotherapy (Table). OS was also prolonged with avelumab + BSC in pts in PD-L1+ tumors who had received 1L gemcitabine + carboplatin, consistent with findings in the overall population. In genomic subtypes, the OS benefit for avelumab + BSC was apparent across TCGA subtypes except luminal. Conclusions: An OS benefit was seen for avelumab 1L maintenance + BSC vs BSC alone across subgroups of interest. Results are consistent with previously reported findings, further supporting avelumab 1L maintenance as a standard of care for pts with advanced UC that has not progressed with 1L platinum-containing chemotherapy. Clinical trial information: NCT02603432. [Table: see text]

Clinical safety and activity of cabozantinib (CABO) plus durvalumab (DURVA) in patients (pts) with advanced urothelial carcinoma (UC) after platinum chemotherapy (ARCADIA): Preliminary results from a nonrandomized, open-label, phase 2 trial.

e16529 Background: Combining anti-VEGFR drugs with checkpoint inhibitors have shown synergistic effect in pts with UC. ARCADIA is a phase 2 trial evaluating the safety and efficacy of combination of CABO, a multikinase inhibitor, with the anti-PDL1 DURVA in pts with platinum-refractory advanced UC or variant histology (NCT03824691). Herein we report the preliminary results. Methods: Pts received CABO 40 mg daily, orally, in combination with DURVA 1500 mg, intravenously, every 28 days, until disease progression or unacceptable toxicity. Key inclusion criteria were: ECOG-PS 0-1, UC or variant histology, failure of 1 or 2 platinum-based regimen for metastatic disease, non-measurable disease was permitted. Response was evaluated by RECIST criteria v.1.1 every 2 cycles by CT and 18FDG PET/CT scans. The primary endpoint of the study was overall survival (OS). Other endpoints included safety, objective response-rate (ORR), duration of response, progression-free survival (PFS). PD-L1 expression was assessed by Ventana SP142 assay. Next-generation sequencing tests (FoundationOne) on pre-therapy tumor samples were performed. Results: From September 2019 to February 2021, 26 pts were enrolled with a median follow-up of 5 mo. Median age was 64 yrs (range 44-74), 69% were male, and 23% had ECOG PS 1. 8 pts presented variant histology. Five pts (19%) had received 2 prior systemic anticancer therapies. In pts evaluable for efficacy analyses, 3 (11.5%) complete responses (CR) and 6 (23.1%) partial responses (PR) were observed. The ORR and DCR were 34.6% and 57.7% respectively. Treatment-related AEs (TRAEs) occurred in 17 pts (65%), including 2 (8%) grade 3 TRAEs, within the first 2 cycles. 7 pts (27%) discontinued CABO due to toxicity, no interruption of DURVA was observed. The most common AEs by any grade were transaminase increase (35.7%), asthenia (27%), diarrhea (27%), and hypertension (15%). Conclusions: Combination of CABO and DURVA demonstrated promising preliminary activity and a manageable safety profile in pts with advanced UC and variant histology. More mature results according to biomarkers and histology will be presented. Clinical trial information: NCT03824691.

Tumor infiltrating lymphocytes and programmed death ligand-1 can identify different prognostic profiles in breast cancer.

e12622 Background: Immunologic biomarkers such as tumor infiltrating lymphocytes (TILs) and programmed death ligand-1 (PD-L1) can provide prognostic information in breast cancer (BC) patients. Specifically, a high TILs level has been associated with pathologic complete response and enhanced disease-free survival (DFS). Furthermore, PD-L1 positivity has been associated with worse DFS and overall survival (OS). However, the interaction of both biomarkers as well as its association with survival outcomes in specific BC subtypes is still a subject of ongoing research. Methods: Medical records of women diagnosed with primary BC between 2013 and 2015 in a center in Monterrey, Mexico were reviewed. Eligible patients had at least 1 year of follow-up, stages I-III at diagnosis, and available tissue for TILs and PD-L1 assessment. PD-L1 positivity was defined as the presence of PD-L1 in ≥1% of tumor-infiltrating immune cells using the VENTANA SP142 assay. Classification of TILs into low ( < 30%) and high (≥30%) levels was performed for analytical purposes. Clinicopathological features were compared with Fisher’s exact tests and logistic regression models, as appropriate. The Kaplan-Meier method was used to calculate recurrence-free survival (RFS), and associations between variables were explored with log-rank or Cox regressions. Results: A total of 195 patients were included. Overall, 12.3% of BC biopsy specimens showed positivity to PD-L1 (8.3% [11/132] in HR+/HER2-, 5.9% [2/34] in HER2+, and 38% [11/29] in TNBC; p < 0.001). PD-L1 positivity was significantly associated with ER-negative status (OR 3.1; p = 0.013), high TILs (OR 5.7; p < 0.001), and high Ki67 expression (HR 12.5; p < 0.001). The median follow-up for the entire cohort was 61 months (95%CI 58-63). RFS in the PD-L1- group was significantly superior to the PD-L1+ group (85% vs. 66% at 5 years; p = 0.021). In a multivariate Cox model, PD-L1 positivity (HR 3.3), low TILs (HR 3.4), advanced stage (HR 2.8), and high histological grade (HR 2.5) were all independent prognostic factors for worse RFS. Based on these results, we further classified our cohort into four prognostic profiles based on PD-L1 and TILs status. The low TILs/PD-L1+ group experienced an inferior RFS than low TILs/PD-L1- patients (45% vs. 85% at 5-years; p-value < 0.001), while no difference was observed in the high TILs groups. Notably, when analyzing HR+/HER2- patients only, a similar statistical difference was observed between low TILs/PD-L1+ and low TILs/PD-L1- groups (HR 5.4, p = 0.009). Conclusions: In our cohort, PD-L1 positivity together with low TILs identified a subset of BC patients with a worse RFS. Interestingly, patients with HR+/HER2- BC fared worse in the low TILs/PD-L1+ subcategory than in the low TILs/PD-L1- group. Future studies are warranted to explore the prognostic value of categorizing patients based on TILs and PD-L1 status in different BC subtypes.

Association of pathological clinical characteristics, PD L 1 receptor expression (sp 142), with tumor lymphocytic infiltration cells (TILs) in patients (pts) with triple negative breast cancer (TNBC) in Tucumán, Argentina.

e13049 Background: Breast cancer (BC) is the most prevalent tumor in women and the leading cause of cancer death in women. TNBC has the worst prognosis among BC subtypes and limited treatment options, mainly including chemotherapy. The efficacy of immunotherapy is clear for immunogenic tumors, such as melanoma, kidney cancer, non-lung cancer small cell, among others. BC seems to be less immunogenic. Basal-type TNBC present a prominent infiltration of inflammatory cells, suggesting that an immune pathway plays a role in tumorogenesis. The development of immunotherapy (IO)has reached an important turning point in the history of cancer treatment based on the use of the immune system itself to fight tumor cells. PD-L1 overexpression is the only predictive response biomarker for anti-PD-1 / PD-L1 therapy that is accepted in TNBM. Methods: Retrospectively, 68 cases of TNBC from the Pathological Anatomy Service of the Ntra. Sra. De las Mercedes Maternity Institute, of Tucumán, between 2010 and 2016 were analyzed. VENTANA anti PDL1 sp142 assay platform was used. Tumor-infiltrating immune cells (IC) are scored as the proportion of tumor area that is occupied by PD-L1 staining IC of any intensity. A specimen should be considered to have PD-L1 expression if the specimen exhibits ≥ 1% IC. In addition, carcinomas with a proportion greater than 50% of lymphocytic infiltration and its association with the expression of PD L1 were studied according to the recommendations of the International TILs Working group. Results: The median age of the patients was 56 years (21-80). The predominant histological type was non-specific type ductal carcinoma, reported in 45/68 cases (66%), following the medullar 9 / 68 (13%) lobular in 8/68 (11%), metaplastic 3/68 (4%) and other 4%. The tumor grade (G), half of the cases were G 3 with 34/68 (50%), G 2 with 42%. The largest proportion of pts, 42%, had no lymph node (LN) involvement, 33% had between 1 to 3 positive LN and 25% showed 4 or more LN. Stage II 39/68 patients (58%) in stage III 20/68 (30%), I (9%, 6) and IV (3%, 2). 16% (11/68) of the patients were PD-L1 positive. Tumors with lymphocytic infiltration between 0% and 10% expressed 24% (2/37), no expression was observed in tumors with TIls between 10 and 50% and in cases with lymphocytic infiltration greater than 50% expression of PD L was observed 1 in 9/18 cases (50%) (Fisher's exact test, p < 0.0001). Conclusions: It was demonstrated that there is an association between the stromal lymphocytic infiltrate (TILs) and the expression of PD-L1 in tumor cells, in this population of women from Tucumán, which would help to select patients as candidates for anti PD L1 therapies.

Clinical and genomic assessment of PD-L1 SP142 expression in triple-negative breast cancer

PurposeThe SP142 PD-L1 assay is a companion diagnostic for atezolizumab in metastatic triple-negative breast cancer (TNBC). We strove to understand the biological, genomic, and clinical characteristics associated with SP142 PD-L1 positivity in TNBC patients.MethodsUsing 149 TNBC formalin-fixed paraffin-embedded tumor samples, tissue microarray (TMA) and gene expression microarrays were performed in parallel. The VENTANA SP142 assay was used to identify PD-L1 expression from TMA slides. We next generated a gene signature reflective of SP142 status and evaluated signature distribution according to TNBCtype and PAM50 subtypes. A SP142 gene expression signature was identified and was biologically and clinically evaluated on the TNBCs of TCGA, other cohorts, and on other malignancies treated with immune checkpoint inhibitors (ICI).ResultsUsing SP142, 28.9% of samples were PD-L1 protein positive. The SP142 PD-L1-positive TNBC had higher CD8+ T cell percentage, stromal tumor-infiltrating lymphocyte levels, and higher rate of the immunomodulatory TNBCtype compared to PD-L1-negative samples. The recurrence-free survival was prolonged in PD-L1-positive TNBC. The SP142-guided gene expression signature consisted of 94 immune-related genes. The SP142 signature was associated with a higher pathologic complete response rate and better survival in multiple TNBC cohorts. In the TNBC of TCGA, this signature was correlated with lymphocyte-infiltrating signature scores, but not with tumor mutational burden or total neoantigen count. In other malignancies treated with ICIs, the SP142 genomic signature was associated with improved response and survival.ConclusionsWe provide multi-faceted evidence that SP142 PDL1-positive TNBC have immuno-genomic features characterized as highly lymphocyte-infiltrated and a relatively favorable survival.

P37.26 Comprehensive Comparison of 22C3 and SP263 PD-L1 Expression using Routine Clinical and Conditioned Archives of Non-Small-Cell Lung Cancer

Harmonization studies for PD-L1 revealed high correlation of 22C3 and SP263 antibodies in non-small cell lung cancer (NSCLC). However, characteristics of those antibodies in various clinical and analytical setting has yet to be validated. The results of simultaneously performed PD-L1 22C3 and SP263 assays on 431 routine clinical NSCLC samples were reviewed and both assays were performed on 314 archives of surgically resected NSCLCs and assessed the PD-L1 expression according to FFPE block age, and the storage duration and the temperature of FFPE sections. In routine clinical samples, 22C3 showed highest concordance rate with 94.5% of SP263 tumor proportion score (TPS) ≥50% and 98.9% 78.8% of SP263 TPS 1-49%, while SP263 showed concordance rate with 79.6% of 22C3 TPS ≥50% and 82.4% of 22C3 TPS 1-49%. In archives, both 22C3 and SP263 high TPS (versus TPS <1%) were significantly associated with more recent block (<3 years versus ≥3 years) (p = 0007 and p = 0.009, respectively). When FFPE sections were stored at room temperature, only 22C3 TPS was more decreased in longer stored sections. However, the expression was not affected by the section storage duration in both assays when stored at 4°C. For 22C3 TPS 1-49% and ≥50%, there was a significantly higher probability of preserved 22C3 expression in resent section in room temperature (OR = 1.73, p = 0.006 and OR = 1.98, p = 0.002, respectively) but SP263 showed preserved expression in longer section duration in room temperature. Our results showed the high correlation between PD-L1 22C3 and SP263 in routine clinical samples but FFPE block older than 3 years and sections stored at room temperature more than 1 week may lead to underestimation of PD-L1 status especially with 22C3 assay.

Avelumab (Ave) first-line (1L) maintenance plus best supportive care (BSC) versus BSC alone for advanced urothelial carcinoma (UC): JAVELIN Bladder 100 Japanese subgroup analysis.

425 Background: A randomized phase III trial (JAVELIN Bladder 100; NCT02603432) to investigate avelumab (anti–PD-L1) as 1L maintenance therapy in patients with advanced UC met its primary objective, demonstrating significantly prolonged overall survival (OS) with Ave + BSC vs BSC alone in all randomized patients and in patients with PD-L1+ tumors. We report efficacy and safety in Japanese patients enrolled in this study. Methods: Eligible patients with unresectable locally advanced or metastatic UC that had not progressed with 4-6 cycles of gemcitabine with either cisplatin or carboplatin were randomized 1:1 to receive maintenance Ave (10 mg/kg IV every 2 weeks) + BSC or BSC alone, stratified by best response to 1L chemotherapy (complete/partial response vs stable disease) and by visceral vs nonvisceral disease when initiating 1L chemotherapy. The primary endpoint was OS, assessed from randomization in all randomized patients and in patients with PD-L1+ tumors (Ventana SP263 assay). Secondary endpoints included progression-free survival (PFS) per blinded independent central review and safety. Results: Japanese patients (n=73) were randomized to receive Ave + BSC (n=36) or BSC alone (n=37); 52.8% vs 62.2% had PD-L1+ tumors, respectively. Median OS (95% CI) was 24.7 months (18.2-not estimable [NE]) with Ave + BSC vs 18.7 months (12.8-33.0) with BSC alone (HR, 0.81 [95% CI; 0.409-1.585]) in all randomized patients and 18.6 months (9.4-NE) with Ave + BSC vs 19.4 months (11.7-33.0) with BSC alone (HR, 1.00 [95% CI, 0.413-2.412]) in patients with PD-L1+ tumors. Median PFS (95% CI) was 5.6 months (1.9-9.4) with Ave + BSC vs 1.9 months (1.9-3.8) with BSC alone (HR, 0.63 [95% CI, 0.358-1.113]) in all randomized patients and 5.6 months (1.8-11.2) with Ave + BSC vs 1.9 months (1.9-3.8) with BSC alone (HR, 0.62 [95% CI, 0.298-1.301]) in patients with PD-L1+ tumors. The most common treatment-emergent adverse events (all grade; grade ≥3) in the Ave + BSC arm were pyrexia (10 [27.8%]; 0), nasopharyngitis (7 [19.4%]; 0), and anemia (7 [19.4%]; 4 [11.1%]). Conclusions: Ave 1L maintenance + BSC was efficacious and tolerable in Japanese patients with advanced UC, and results were generally consistent with those in the overall population. Clinical trial information: NCT02603432.

Abstract PS4-18: Real-world PD-L1 test utilization and analytical concordance of the PD-L1 IHC 28-8 and 22C3 assays in patients with breast cancer

Abstract Background: Programmed death-1/programmed death ligand 1 (PD-[L]1) inhibitors are approved for use in a range of cancers. PD-L1 expression in the tumor microenvironment, assessed with an FDA-approved PD-L1 immunohistochemistry (IHC) diagnostic assay such as the Dako PD-L1 IHC 28-8 and 22C3 pharmDx or Ventana PD-L1 SP142 and SP263 assays, is associated with improved PD-(L)1 inhibitor treatment outcomes in some tumor types, including breast cancer (BC). In March 2019, the FDA approved atezolizumab + nab-paclitaxel for the treatment of patients with advanced triple-negative BC and immune cell (IC) PD-L1 expression ≥ 1% using the SP142 assay. Here, we investigated test utilization, test turnaround time (TAT), PD-L1 expression prevalence by assay and biopsy location, and analytical concordance between assays in real-world BC samples. Design: The study included samples from patients with BC that were tested for PD-L1 expression between Oct 2015 and Sep 2019 at NeoGenomics Laboratories, a US national reference laboratory. Patient characteristics from Symphony Healthcare Solutions were matched to PD-L1 test results using unique identifiers. Test volume and TAT were assessed for the 28-8, 22C3, SP142, and SP263 assays. PD-L1 expression was determined by trained pathologists using the 28-8, 22C3, or SP142 assays. Results for the 28-8 assay for the entire study period and for the 22C3 assay until Dec 2018 were reported as the percentage of tumor cells (% TC) with PD-L1 expression. From Jan 2019 onwards, 22C3 assay results were reported as a combined positive score (CPS). All SP142 assay results were reported as the percentage of ICs (% IC) with PD-L1 expression. Analytical concordance between assays was assessed in patients with matched samples (biopsies from the same site and collected on the same date). BioStat Solutions performed statistical analyses. Results: 2955 PD-L1 tests were performed on samples from 2508 patients with BC. The volume of PD-L1 tests on BC samples increased &amp;gt; 100-fold over the study period. Mean TAT was &amp;lt; 5 days for all 4 assays pooled. Table 1 shows PD-L1 expression prevalence in patients with a 28-8, 22C3, or SP142 test result. Median PD-L1 expression did not differ between primary tumors and metastatic sites. In matched samples, overall percentage agreement (OPA) between the 28-8 (TC ≥ 1%) and 22C3 (CPS ≥ 1) assays was 94%, and OPA between the 22C3 (CPS ≥ 1) and SP142 (IC ≥ 1%) assays was 64% (Table 2). Analytical concordance between the 28-8 and 22C3 assays for % TC scoring in matched samples from 27 patients was high (Kendall’s tau = 0.997 [95% CI, 0.883-1.000]). Conclusion: Mean PD-L1 test TAT for BC samples remained &amp;lt; 5 days across all tests despite a large increase in test volume over the study period. Prevalence of PD-L1 expression ≥ 1(%) was higher with the CPS and % IC algorithms than the % TC algorithm, although differences could be due to multiple confounding factors. Despite a small sample size, analytical concordance between the 28-8 and 22C3 assays in matched samples was high. These data provide real-world context for the PD-L1 testing landscape in BC. Table 1. Prevalence of PD-L1 expression in patients with BCPD-L1 expressiona28-8 and 22C3b22C3cSP142% TC, n (%)CPS, n (%)% IC, n (%)(N = 608)(N = 609)(N = 1080)&amp;lt;1(%)390 (64)253 (42)367 (34)≥1(%)218 (36)356 (58)713 (66)All patients had a single test result or ≥ 2 identical results. aThe CPS algorithm is reported on a scale of 0-100, not as a percentage; bSamples tested with the 22C3 assay between Q4 2015 and Q4 2018 were scored using the % TC algorithm; cSamples tested with the 22C3 assay between Q1 2019 and Q4 2019 were scored using the CPS algorithm. Table 2. Agreement between assays on matched samples from patients with BCAgreement between 28-8 (TC ≥ 1%) and 22C3 (CPS ≥ 1) (N = 18)a28-8 as reference22C3 as referenceOPA (n/N)94 (17/18)PPA (n/N)100 (6/6)86 (6/7)NPA (n/N)92 (11/12)100 (11/11)Agreement between 22C3 (CPS ≥ 1) and SP142 (IC ≥ 1%) (N = 33)b22C3 as referenceSP142 as referenceOPA (n/N)64 (21/33)PPA (n/N)86 (12/14)55 (12/22)NPA (n/N)47 (9/19)82 (9/11)aData are presented for 28-8 and 22C3 tests on matched samples with 22C3 tests performed between Q1 2019 and Q4 2019; bData are presented for 22C3 and SP142 tests on matched samples with 22C3 tests performed between Q1 2019 and Q4 2019. N, total number of samples; n, number of samples with the same results with the 2 tests; NPA, negative percentage agreement; PPA, positive percentage agreement. Citation Format: Shreya Mitra, Emily A. Prince, James Pratt, James Novotny, Jr, Vladislav Chizhevsky, Josette William Ragheb, David Huron. Real-world PD-L1 test utilization and analytical concordance of the PD-L1 IHC 28-8 and 22C3 assays in patients with breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-18.

Abstract PS2-03: Comparison of pathologist reads of sp142 and sp263 with quantitative measurement of protein and mRNA in triple negative breast cancer

Abstract Background: PD-L1 SP142 immunohistochemistry (IHC) assay has been approved as a companion test by the US Food and Drug Administration (FDA) to identify eligibility for atezolizumab therapy in patients with advanced triple negative breast cancer (TNBC) but a number of studies suggest the assay suffers from poor reproducibility. Using readings of 70 TNBC chromogenic FDA approved assays from 19 pathologists in a previous study as a baseline, we compared pathologist reads to quantitatively measured mRNA and protein expression Methods: Formalin-fixed paraffin-embedded (FFPE) slides representing primary invasive triple negative breast cancer (stage I-III) from 100 patients between 2012-16 were selected from the Yale Pathology archives. Slides were macrodissected to tumor enrichment for quantitative assessment of CD274 (PD-L1 mRNA) measured using a closed-system, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) research use only (RUO)* prototype assay on the GeneXpert® instrument. We also measured protein expression levels using the AQUA method of quantitative immunofluorescence (QIF) in both the tumor and non-tumor compartments on full sections by QIF stained using SP142 in a lab derived test (LDT). The IHC stained slides were prepared using SP142 and SP263 assays prepared exactly according the FDA approved label followed by reading by 19 pathologists. This study was approved by Yale Human Investigation IRB protocol ID 9505008219.Results: Previous work from our group showed overall percent agreement for both the SP142 and SP263 IHC assays read by pathologists was in the 40-50% range. We used the median CD274 score to compare positive (IC≥1) vs negative (IC&amp;lt;1) and found that the levels of mRNA were not statistically significantly different between the two categorical scores. However, quantitative measurement of protein expression (including both tumor and non-tumor regions) showed statistically significant differences between pathologist read PD-L1 positive/negative scoring for SP142 (p=0.0004) and SP263 (p=0.0185). Concordance of quantitative PD-L1 measurement between protein QIF scores and transcript RT-qPCR levels was modest, with a Spearman coefficient r = 0.18. Conclusions: By chromogenic IHC, using the FDA approved assays, pathologist read scoring shows no difference to mRNA for CD274. Quantitative continuous scoring of protein expression show that, on average, when pathologists score IC≥1, there is more protein present than when they score IC&amp;lt;1. Further studies are needed to determine if RNA and protein for PD-L1 are concordant and to determine which assay(s) and cutoff values are best correlated with clinical outcomes on atezolizumab therapy. *For Research Use Only - Not for use in diagnostic procedures. Not approved or reviewed by any regulatory body Citation Format: Swati Gupta, Vesal Yaghoobi, Aileen Fernandez, Leena McCann, Jodi Weidler, Michael Bates, Emily Reisenbichler, David Rimm. Comparison of pathologist reads of sp142 and sp263 with quantitative measurement of protein and mRNA in triple negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-03.

Abstract PS17-27: Molecular evaluation of immunogenicity and genomic alterations in invasive lobular breast cancer

Abstract Background: Invasive lobular carcinoma (ILC) is the second most common type of invasive breast cancer and accounts for 10-15% of all cases. Though ILC has distinct clinical, prognostic and molecular features, studies are limited and include few patients. ILCs show a decreased response to neoadjuvant chemotherapy and an increased resistance to endocrine therapy. Thus, there is a great need to identify alternative therapies, such as immunotherapy, that could improve overall survival. Success of immunotherapy largely depends on tumor immunogenicity which varies with histologic type. Determination of predictive and prognostic biomarkers for ILC will help determine who can benefit the most. Our study investigates canonical markers of immunogenicity - PD-L1 expression and Tumor Mutational Burden (TMB) - in patients with ILC compared to invasive ductal carcinoma (IDC). We further correlate these markers in different subtypes i.e. hormone receptor positive (HR+), HER2 positive (HER2+), and in triple negative breast cancers (TNBC). We also analyze differences in immune cell profiles constituting the tumor microenvironment (TME) and differences in genomic alterations between ILC and IDC. Methods: A retrospective data analysis was performed to identify breast cancer tumors with ILC or IDC histology profiled at Caris Life Sciences (Phoenix, AZ) that were tested for PD-L1 by SP142 assay and had whole transcriptome sequencing data available. ILC and IDC cases were further subtyped as HR+ and HER2+ and TNBC. PD-L1 expression in immune cell was assessed using Ventana PD-L1 (SP142) histochemical assay and PD-L1 expression in tumor cell was assessed by laboratory developed test using SP142 clone with staining higher than 2+ considered positive. TMB was measured by counting somatic non-synonymous missense mutations on the 592 gene panel (Nextseq) next generation sequencing (NGS) assay, and ≥ 10 mutations/megabase (mut/Mb) was considered high. Using the whole transcriptome RNA sequencing (NovaSeq) data we analyzed the difference in immune cell profiles constituting the TME using a computational RNA deconvolution approach. NGS was used to identify significant differences in genomic alterations between ILC and IDC. Results: We identified 1,359 breast cancer patients (ILC: 194 vs IDC: 1,165). Among ILC, 79% were HR +, 11% TNBC, &amp;lt;2% HER2+ and the rest were of unclear subtype, compared to 55% HR +, 31% TNBC, 10% HER2+ in the IDC group. PD-L1 expression in immune cells was lower in ILC (PD-L1≥ 1% ILC: 13% vs. IDC: 35% p &amp;lt;0.0001; PD-L1&amp;gt;10% ILC: 1% vs. IDC: 5% p=0.017). PD-L1 expression in tumor cells was also lower in ILC (ILC 1% vs IDC 5%; p =0.0136). All subtypes of ILC had lower PD-L1 expression in immune and tumor cells when compared to IDC. TMB was similar and comparable in IDC and ILC (median TMB 7 mut/Mb). Assessment of TME showed a significantly increased abundance of cytotoxic lymphocytes and monocytic cells in IDC, and stromal endothelial cells in ILC. Androgen receptor (AR) expression, and mutations in CDH1 (ILC 76% vs IDC 2%) and PIK3CA (ILC 44% vs IDC 30%) were more common in ILC. CDH1 mutation was significantly higher in both TN ILC (ILC 60% vs IDC 1%; p&amp;lt;0.05) and HR+ ILC (77% vs IDC 2%; p&amp;lt;0.05) subtypes of ILC. TP53 mutation was lower in ILC (ILC 26% vs IDC 65%) irrespective of subtype. Conclusion: In summary, PD-L1 expression in immune cells and tumor cells was lower in ILC, however TMB was comparable between ILC and IDC. Immune cell profiling supports a cold or less immunogenic TME for ILC. A composite immune biomarker may be able to better characterize immunogenicity of ILC. Citation Format: Upama Giri, Joanne Xiu, Tatiana Karadimitriou, Sofi Castanon, Foluso Ademuyiwa, Paula Pohlmann, Elias Obeid, Jasgit Sachdev, Elisa Krill-Jackson, Michael Simon, Antoinette Tan, Neelima Denduluri, Lee Schwartzberg, Michael Korn, Evanthia T Roussos Torres. Molecular evaluation of immunogenicity and genomic alterations in invasive lobular breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-27.

Abstract PD14-05: Genomic profiling and clinical outcomes with first-line atezolizumab and nab-paclitaxel in triple-negative breast cancer: An exploratory analysis from the phase 3 IMpassion130 trial

Abstract Background: The clinical implications of genomic alterations in metastatic triple-negative breast cancer (mTNBC) have not been clearly addressed. In IMpassion130, atezolizumab (A) + nab-paclitaxel (nP) showed improved progression-free survival (PFS) and clinically meaningful overall survival (OS) benefit vs placebo (P) + nP in PD-L1+ mTNBC (Schmid, NEJM 2018). The goal of this exploratory study was to evaluate the prevalence of genomic alterations and their relationship with PD-L1 status and to determine whether a prognostic or predictive role for these factors exists for A + nP in a randomized dataset. Methods: Primary or metastatic tumor samples from patients in the IMpassion130 biomarker-evaluable population (BEP) were centrally evaluated for short variants (SV), copy number alteration (CNA) and rearrangements by using a targeted next-generation sequencing (NGS) panel (FoundationOne). PD-L1 status was evaluated using the VENTANA SP142 assay, with PD-L1 positivity defined by PD-L1-expressing immune cells on ≥1% of tumor area. Prognostic effects of genomic alterations were evaluated in the pooled population from both treatment arms. PFS and OS (co-primary endpoints) were analyzed by Cox proportional hazards models. ClinicalTrials.gov identifier: NCT02425891. Results: The BEP comprised 614 patients (68% of intent-to-treat population), 605 of whom received treatment. The most common pathogenic alterations were found in the following genes: TP53 (SV, 85%), MYC (CNA, 21%), PIK3CA (SV, 18%), PTEN (SV/CNA, 18%), RB1 (SV, 7%) and BRCA1 (SV, 9%). Primary tumors (n = 419), compared with metastatic tumors (n = 195), were more likely to bear alterations in BRCA1 (11.9% vs 5.6%) and less likely to have PIK3R1 alterations (4.8% vs 9.2%). TP53 loss-of-function mutations were associated with PD-L1+ status, whereas amplifications in VEGFA and CCND3 genes were significantly less associated; none of these alterations were linked with clinical outcomes favoring A + nP. Loss of RB1 (frequency 5%) was linked with reduced PFS and OS prognosis independent of treatment (hazard ratio [HR], 2.09 [95% CI: 1.42, 3.07] and HR, 1.98 [1.26, 3.11]), respectively), and CNA in CDKN2A (12%) and CDKN2B (11%) were associated with improved PFS and OS clinical activity in the A + nP arm vs the P + nP arm (HR PFS, 0.43-0.44 and HR OS, 0.47, respectively). Three of 584 microsatellite-evaluable samples (0.5%) had MSI-H status, which was not associated with PD-L1 status; all 3 MSI-H patients were from the P + nP arm. A total of 220 of 514 evaluable samples (42.8%) had PIK3CA/AKT1/PTEN-altered status, which was not significantly associated with PD-L1 status or A + nP clinical outcome. Conclusions: In this exploratory analysis using a targeted NGS panel, we show that tumors from patients with previously untreated mTNBC had similar genomic profiles at baseline as those published for early TNBC tumors. The few alterations that were linked to PD-L1 status were not linked to clinical outcome. CNA in cell cycle genes (e.g., RB1) had potential prognostic value, whereas CDKN2A and CDKN2B were potentially predictive of A + nP clinical benefit favoring A + nP. These data are hypothesis generating and require validation in an independent data set. Citation Format: Leisha Emens, Luciana Molinero, Sylvia Adams, Hope S. Rugo, Andreas Schneeweiss, Véronique Diéras, Hiroji Iwata, Carlos Barrios, Eric P. Winer, Ching-Wei Chang, Stephen Y. Chui, Peter Schmid, Sherene Loi. Genomic profiling and clinical outcomes with first-line atezolizumab and nab-paclitaxel in triple-negative breast cancer: An exploratory analysis from the phase 3 IMpassion130 trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD14-05.

Abstract PD1-06: Trilaciclib improves overall survival when given with gemcitabine/carboplatin in patients with metastatic triple-negative breast cancer: Final analysis of a randomized phase 2 trial

Abstract Background Trilaciclib is an intravenous (IV) cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. Preliminary data showed that adding trilaciclib prior to gemcitabine plus carboplatin (GCb) significantly increased overall survival (OS) compared with GCb alone among patients with metastatic triple-negative breast cancer (mTNBC) (Tan et al., Lancet Oncol. 2019;20:1587-1601). Here, final antitumor efficacy results (objective response rate [ORR], progression-free survival [PFS], and OS) are reported for the whole study population, and in cohorts according to CDK4/6 dependence and level of programmed death ligand-1 (PD-L1) expression. Methods This was a randomized, open-label, phase 2 study of patients with mTNBC who had received ≤2 previous lines of chemotherapy in the recurrent/metastatic setting (NCT02978716). Patients were randomized (1:1:1) to receive GCb on days 1 and 8 (group 1, n=34), trilaciclib prior to GCb on days 1 and 8 (group 2, n=33), or trilaciclib alone on days 1 and 8 and prior to GCb on days 2 and 9 (group 3, n=35), in 21-day cycles. PFS and OS (prespecified secondary endpoints) were assessed in the intention-to-treat (ITT) population, and ORR in response-evaluable patients. Patient tumors were characterized as CDK4/6 independent (basal-like) or indeterminate (HER2-enriched, normal-like, luminal A/B) according to the established PAM50 signature, or CDK4/6 dependent (luminal androgen receptor) or indeterminate (basal-like 1/2, mesenchymal) according to the established Lehmann signature. PD-L1 expression was scored as negative or positive if &amp;lt;1% or ≥1% of the total tumor area contained PD-L1-labelled immune cells, respectively, using the Ventana SP142 assay. Association of CDK4/6 dependence and PD-L1 expression with antitumor efficacy was assessed using proportional hazards regression. Results Median follow-up was 8.4 months (range: 0.1-25.7) for group 1, 14.0 months (1.3-33.6) for group 2, and 15.3 months (3.5-33.7) for group 3. The ORR among response-evaluable patients was 7/24 (29.2%) in group 1, 15/30 (50.0%) in group 2, and 12/31 (38.7%) in group 3. Median PFS (95% confidence interval [CI]) in the ITT population was 5.7 (3.3, 9.9) months in group 1, 9.4 (6.1, 11.9) months in group 2, and 7.3 (6.2, 13.9) months in group 3, with hazard ratios (HRs) of 0.62 (P = 0.2099) and 0.63 (P = 0.1816), for groups 2 and 3 versus group 1, respectively. Overall, 73.5%, 39.4%, and 57.1% of patients in groups 1, 2, and 3 had died. Median OS (95% CI) was 12.6 (6.3, 15.6) months in group 1, not reached (NR) (10.2, NR) in group 2 (HR = 0.31, P = 0.0016), and 17.8 (12.9, 32.7) months in group 3 (HR = 0.40, P = 0.0004). For groups 2 and 3 combined, median OS was 19.8 (14.0, NR) months (HR = 0.37, P &amp;lt;0.0001 vs group 1). ORR, PFS, and OS were comparable in tumors categorized as CDK4/6 dependent, independent, or indeterminate. Antitumor efficacy by PD-L1 status is provided in the Table. Conclusions Mature data from this study confirm that administering trilaciclib prior to GCb enhances antitumor efficacy compared with GCb alone, with statistically significant improvements in OS. Subgroup analyses suggest that adding trilaciclib prior to GCb benefits patients regardless of CDK4/6 dependence status and PD-L1 expression. Additional immune subtyping analyses are ongoing and will be presented. Group 1Group 2Group 3PD-L1 +vePD-L1 –vePD-L1 +vePD-L1 –vePD-L1 +vePD-L1 –vePatients, n171016101616ORR, n (%)4 (23.5)3 (30.0)8 (50.0)4 (40.0)7 (43.8)4 (25.0)Median PFS, months (95% CI)3.5 (2.2, NR)9.5 (5.2, NR)7.9 (4.3, NR)11.9 (8.8, NR)9.0 (6.2, NR)6.9 (6.4, NR)P value (Wald Test)––0.3470.6040.0690.766HR (95% CI)––0.70 (0.3, 1.5)0.76 (0.3, 2.2)0.46 (0.2, 1.1)1.16 (0.4, 3.1)Median OS, months (95% CI)10.5 (6.3, 18.8)13.9 (12.6, NR)20.1 (10.2, NR)NR (9.4, NR)32.7 (15.3, NR)17.8 (12.9, NR)P value (Wald Test)––0.0280.0830.020.239HR (95% CI)––0.35 (0.1, 0.9)0.34 (0.1, 1.2)0.33 (0.1, 0.8)0.57 (0.2, 1.5)HR and P values are for comparisons between group 2 versus group 1, and group 3 versus group 1.+ve, positive; –ve, negative; CI, confidence interval; HR, hazard ratio; NR, not reached; ORR, objective response rate; OS, overall survival; PD-L1, programmed death ligand-1; PFS, progression-free survival. Citation Format: Joyce O'Shaughnessy, Gail S Wright, Anu R Thummala, Michael A Danso, Lazar Popovic, Timothy J Pluard, Hyo S Han, Željko Vojnović, Nikola Vasev, Ling Ma, Donald A Richards, Sharon T Wilks, Dušan Milenković, Jie Xiao, Jessica A Sorrentino, Janet Horton, Antoinette R Tan. Trilaciclib improves overall survival when given with gemcitabine/carboplatin in patients with metastatic triple-negative breast cancer: Final analysis of a randomized phase 2 trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD1-06.

Comparison of PD-L1 immunohistochemical assays in advanced gastric adenocarcinomas using endoscopic biopsy and paired resected specimens

Immunohistochemical (IHC) assays for programmed death ligand 1 (PD-L1) expression are crucial for guiding immune checkpoint inhibitor therapies in advanced gastric adenocarcinoma (AGC). The results from clinical trials of various PD-L1 antibody clones are variable and the exchangeability of these assays is a highly sought goal. The aim of this study was to determine whether three different PD-L1 assays (SP263 and 22C3 on the Dako and Ventana platforms) are interchangeable through analysis of their concordance rate within samples between biopsy and paired resected specimens. One hundred pairs of biopsied and resected AGC specimens were collected and stained for PD-L1. The combined positive score (CPS) was used for the IHC analysis and a four tiered system was applied, i.e., <1, 1 to < 5, 5 to 50, and >50. The agreement for the different IHC assays was low across all cut-offs with the biopsied or resected specimens (biopsy, κ=0.17-0.453; resection, κ=0.02-0.311). The overall positive agreement (OPA) for the PD-L1 results from the biopsy and resection tissues was 100% (SP263, κ=1), 86% (22C3 on the Dako platform, κ=0.693) and 93% (22C3 on the Ventana platform, κ=0.82) at the CPS1 cut-off. The low concordances among the three PD-L1 IHC assays indicated that they cannot be used interchangeably in clinical practice. The results of the SP263 assay using CPS1 showed the highest agreement between the biopsy and resection specimens, suggesting SP263 may provide the most representative approach for the evaluation of PD-L1 status in gastric cancer.

Real-world outcomes of anti-PD1 antibodies in platinum-refractory, PD-L1-positive recurrent and/or metastatic non-small cell lung cancer, and its potential practical predictors: first report from Korean Cancer Study Group LU19-05.

Although immune-checkpoint inhibitors have become a new therapeutic option for recurrent/metastatic non-small cell lung cancers (R/M-NSCLC), its clinical benefit in the real-world is still unclear. We investigated 1181 Korean patients with programmed death-1 ligand 1 (PD-L1)-positive [tumor proportion score (TPS) ≥ 10% by the SP263 assay or ≥ 50% by the 22C3 assay] R/M-NSCLC treated with pembrolizumab or nivolumab after failure of platinum-based chemotherapy. The median age was 67years, 13% of patients had ECOG-PS ≥ 2, and 27% were never-smokers. Adenocarcinoma was predominant (61%) and 18.1% harbored an EGFR activating mutation or ALK rearrangement. Pembrolizumab and nivolumab were administered to 51.3% and 48.7, respectively, and 42% received them beyond the third-line chemotherapy. Objective response rate (ORR) was 28.6%. Pembrolizumab group showed numerically higher ORR (30.7%) than the nivolumab group (26.4%), but it was comparable with that of the nivolumab group having PD-L1 TPS ≥ 50% (32.4%). Median progression-free survival (PFS) and overall survival (OS) were 2.9 (95% CI 0-27.9) and 10.7months (95% CI 0-28.2), respectively. In multivariable analysis, concordance of TPS ≥ 50% in both PD-L1 assays and the development of immune-related adverse events (irAEs) were two significant predictors of better ORR, PFS, and OS. EGFR mutation could also predict significantly worse OS outcomes. The real-world benefit of later-line anti-PD1 antibodies was comparable to clinical trials in patients with R/M-NSCLC, although patients generally were more heavily pretreated and had poorer ECOG-PS. Concordantly high PD-L1 TPS ≥ 50% and development of irAE could independently predict better treatment outcomes, while EGFR mutation negatively affected OS.

Programmed Death Ligand 1 Immunohistochemistry in Triple-Negative Breast Cancer: Evaluation of Inter-Pathologist Concordance and Inter-Assay Variability.

PurposeThe programmed death ligand 1 (PD-L1) SP142 assay with a 1% immune cell (IC) cutoff is approved for the selection of advanced triple-negative breast cancer (TNBC) patients for atezolizumab treatment. We aimed to evaluate the interobserver concordance of PD-L1 scoring and inter-assay variability of various PD-L1 assays in TNBC.MethodsThirty patients with primary TNBC were selected, and SP142, SP263, 22C3, and E1L3N assays were performed. PD-L1 staining in ICs and tumor cells (TCs) was scored by 10 pathologists who were blinded to the assay. The interobserver concordance among pathologists and the inter-assay variability of the four PD-L1 assays were analyzed. For SP142, the intraobserver concordance among the six pathologists was analyzed after training.ResultsThe adjusted means of PD-L1 IC scoring ranged from 6.2% to 12.9% for the four assays; the intraclass correlations showed moderate (0.584–0.649) reader concordance. The PD-L1 IC scoring with a 1% cutoff resulted in identical scoring in 40.0%–66.7% of cases and a poor to moderate agreement (Fleiss κ statistic [FKS] = 0.345–0.534) for the four assays. The SP142 assay had the widest range of positive rate (56.5%–100.0%), lowest number of cases with identical scoring, and lowest FKS at 1% cutoff. Pairwise comparison of adjusted means showed significantly decreased PD-L1 staining in SP142 compared with the other assays in both ICs and TCs. As for the intraobserver concordance in the SP142 assay, the overall percent agreement was 87.8% with a 1% IC cutoff. After training, the proportion of cases with identical scoring at a 1% IC cutoff increased to 70.0%; the FKS also increased to 0.610.ConclusionThe concordance of PD-L1 IC scoring among pathologists was low, at the 1% cutoff for the SP142 assay without training. SP142 showed the lowest PD-L1 expression in both IC and TC.

Predictive Biomarkers for Immune Checkpoint Inhibitors in Metastatic Breast Cancer.

We examined a large dataset of female metastatic breast cancers (MBCs) profiled with comprehensive genomic profiling (CGP) to identify the prevalence and distribution of immunotherapy responsiveness‐associated biomarkers. DNA was extracted from 3831 consecutive MBCs: 1237 (ERpos/HER2 neg), 1953 ERneg/HER2 amp, and 641 triple‐negative breast cancer (TNBC). CGP was performed using the FoundationOne® or FoundationOne®CDx NGS assay. Tumor mutational burden (TMB) and microsatellite instability (MSI) were determined in a subset of cases. PD‐L1 expression in immunocytes in a subset of cases was determined by immunohistochemistry using the companion diagnostic VENTANA PD‐L1 SP142 Assay. The median age of the cohort was 54 years (range 20–89). Genomic alterations (GAs)/tumor were similar (range: 5.9–7.3). Markers of potential immune checkpoint inhibitor (ICPI) benefit included: CD274 (PD‐L1) amplification (1%–3%), BRAF GA (1%–4%), TMB of ≥10 mutations/Mb (8%–12%), MSI‐high (0.1%–0.4%), PBRM1 GA (1%), and positive PD‐L1 staining of immunocytes ranging from 13% in ERpos/HER2 neg and 33% in ERneg/HER2 amp to 47% in the TNBC group. Potential markers of ICPI resistance included inactivating STK11 GA (1%–2%) and MDM2 amplification (3%–6%). MTOR pathway targets were common with lowest frequency in TNBC. ERBB2 short variant mutations were most frequent ERpos/HER2 neg and absent in TNBC. BRCA1/2 GA were least frequent in ERneg/HER2 amp. The demonstrations of clinical benefit of immunotherapy in MBC support the need for development and utilization of biomarkers to guide the use of ICPIs for these patients. In addition to guiding therapy selection, CGP shows potential to identify GA linked to response and resistance to ICPI in MBC.

PD-L1 Expression in Muscle-Invasive Urinary Bladder Urothelial Carcinoma According to Basal/Squamous-Like Phenotype.

Urothelial carcinoma (UC) is the most common histologic type of urinary bladder cancer, and muscle-invasive UC shows aggressive behaviors. Programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) blockades have been approved as standard treatments for patients with advanced stage UC. A total of 166 muscle-invasive urinary bladder cancer (MIBC) patients, who underwent transurethral resection of the bladder or cystectomy from 2004 to 2010 were included. We evaluated PD-L1 expression by the SP142 and SP263 assays and classified the cases “positive” or “negative” according to the manufacturer’s recommendations. We performed immunohistochemistry (IHC) for cytokeratin (CK) 5/6, CK14, GATA3, FOXA1, and CK20 and classified samples as Basal-Squamous-like (BASQ) or non-BASQ subtype. The overall concordance rate for PD-L1 expression is 91.6% (152/166) (kappa = 0.732). The SP142 assay showed 15.1% positivity; the SP263 assay showed 23.5%. The high positivity in the SP142 and SP263 assay was significantly correlated with positive CK5/6, CK14 expression, negative GATA3, FOXA1, and CK20 expression. Classification according to IHC expression resulted in 12.0% (20/166) of samples being classified as BASQ subtype and 88.0% (146/166) of samples being classified as non-BASQ subtype. High positivity in the SP142 and SP263 assay was significantly correlated with the BASQ subtype (p < 0.001, both). Our study is the first to analyze the association of immunohistochemically defined BASQ and non-BASQ subtypes with two PD-L1 assays in MIBC. In conclusion, we revealed that a high PD-L1 positive rate in all PD-L1 assays was significantly associated with the BASQ-subtype, and these results suggest that the BASQ classification may be important to apply the PD-1/PD-L1 blockades in MIBC.

Cabozantinib (CABO) plus durvalumab (DURVA) in patients (pts) with advanced urothelial carcinoma (UC) after platinum chemotherapy: safety and preliminary activity of the open-label, single-arm, phase 2 ARCADIA trial

Both DURVA and CABO, an inhibitor of MET, AXL, and VEGFR, have shown single-agent activity in pts with UC. ARCADIA is a phase 2 study evaluating the combination of CABO with DURVA in pts with advanced UC or non-UC histology (NCT03824691). Herein we report the results of the interim safety analysis and the preliminary activity. Pts receive CABO 40 mg daily, orally, and are administered DURVA 1500 mg, intravenously, q28 days, until disease progression (PD, by RECIST 1.1) or onset of unacceptable toxicity. Key inclusion criteria are: ECOG-PS 0-1, UC and non-UC histology, failure of 1 or 2 platinum-based regimen for metastatic disease. Response is evaluated by RECIST criteria v.1.1 q2 cycles by CT and PET/CT scans. The primary endpoint of the study is OS. Other endpoints include safety (CTCAE v.4.03), objective response-rate (ORR), duration of response, progression-free survival. PD-L1 expression is assessed using with the Ventana SP142 assay. Next-generation sequencing tests (FoundationOne) on pre-therapy tumor samples is also performed As of May 20, 2020, 14 pts were enrolled with a median follow-up of 5 mo (range 1-8). Median age was 66 yrs (range 44, 74), 21% were male, and 60% had ECOG PS 1. 2 pts had pure neuroendocrine (NE) histology. Four pts (28%) had received 2 prior systemic anticancer therapies. Median tumor mutational burden (TMB) was 6 mut/Mb. Treatment-related AEs (TRAEs) occurred in 9 pts (64.3%), including 2 (14.3%) Grade 3 TRAEs, within the first 2 cycles. 3 pts (21.4%) discontinued CABO due to toxicity, none DURVA. The most common of any grade AEs were increased transaminases (35.7%) asthenia and diarrhea (28.6%), and hypertension (21.4%). In 10 response-evaluable pts, partial response (PR) was obtained in 2 (20%), ongoing at 6+ mo in one case harboring a driver RET (F116L) mutation. 0/2 NE tumors responded. CABO in combination with DURVA demonstrated encouraging clinical activity in pts with advanced UC with an acceptable safety profile. More mature results according to CABO-response biomarkers and histology will be presented.

PCN148 The Clinical and Economic IMPACT of PD-L1 SP142 ASSAY Using Atezolizumab + Npaclitaxel in the Pathway of Patients with Metastatic or Advanced Triple Negative Breast Cancer

PCN148 The Clinical and Economic IMPACT of PD-L1 SP142 ASSAY Using Atezolizumab + Npaclitaxel in the Pathway of Patients with Metastatic or Advanced Triple Negative Breast Cancer

Comparison of three FDA-approved diagnostic immunohistochemistry assays of PD-L1 in triple-negative breast carcinoma

The Dako 28-8, Dako 22C3, and Ventana SP142 assays are among the approved programmed death ligand 1 (PD-L1) immunohistochemical companion/complementary diagnostics associated with cancer treatment. To address the concordance of these assays in triple-negative breast cancer (TNBC), we examined PD-L1 expression in 98 TNBC tumors and compared the positive rates using the three assays and three scoring methods: immune cell (IC), tumor cell (TC), and combined tumor cell and immune cell (TCIC) (an equivalent to combined positive score, or CPS). The positive rate for PD-L1 expression with a 1% cutoff was highest with 28-8, followed by the 22C3. These two assays demonstrated almost perfect or substantial agreement in all three scores. There was less agreement between SP142 and the other assays. Using the IC score or the TCIC score at a 1% cutoff (CPS 1), 4% of tumors were positive for PD-L1 with SP142 but negative with the other assays. Using SP142 with a 1% cutoff as a reference, the optimal cutoff for best agreement was at 1% for IC, 30% for TC, and 2% for TCIC (CPS 2) with the other two assays. A 2% cutoff for the 22C3 TCIC (CPS 2) yielded the best agreement with SP142 1% IC cutoff (kappa 0.65). Our study showed the lowest positive rate with SP142 among the three assays. However, the other two assays were not able to identify all tumors that would test positive with SP142 using IC or TCIC/CPS. It is unlikely to achieve high agreement between SP142 and the other two assays by changing the analytical cutoffs.