Trastuzumab-based Treatment Research Articles

Adjuvant regimens with trastuzumab administered for small HER2-positive breast cancer in routine clinical practice.

Trastuzumab has proven to improve the prognosis of HER2-positive breast cancer, but the information available about its administration for small tumors is still limited. Therefore, we assessed the use of adjuvant regimens with trastuzumab for the treatment of small HER2-positive breast cancer in routine clinical practice. This observational study was conducted in patients with HER2-positive breast adenocarcinoma ≤1.5cm who received trastuzumab-based adjuvant treatment in clinical practice. Clinical/histopathological data were retrieved from patients' medical charts. A total of 101 evaluable patients were enrolled (median age [range], 56.7 [49.0-64.8] years; ECOG 0, 98.0%; ductal carcinoma, 88.1%; lymph nodes N0, 79.2%). Only five (5.0%) patients received neoadjuvant treatment, while all patients underwent tumor surgery. Adjuvant trastuzumab was administered at a mean (±SD) dose of 5.9±1.5mg/kg/cycle, and mostly in a three-weekly schedule (89 [89.0%] patients). The most frequent adjuvant therapy used with trastuzumab was chemotherapy (87 [86.1%] patients), followed by radiotherapy (63 [62.4%] patients) and hormone therapy (52 [51.5%] patients). Chemotherapy regimens mainly included doxorubicin, cyclophosphamide and paclitaxel/docetaxel (n=30), docetaxel and cyclophosphamide (n=15), docetaxel and carboplatin (n=13). Hormone therapy mainly included letrozole (n=17) and tamoxifen (n=17). Nine (8.9%) patients reported trastuzumab-related adverse events; only one allergic reaction reached grade 3 toxicity. This study shows that trastuzumab-based adjuvant treatment of small HER2-positive breast cancer is mostly based on chemotherapy-mainly paclitaxel/docetaxel. Adjuvant administration of trastuzumab for small HER2-positive breast cancer seems to be similar to that used for larger tumors.

Optimal Patient Selection for Trastuzumab Treatment in HER2-Positive Advanced Gastric Cancer.

Chemotherapy plus trastuzumab is standard of care for HER2-positive advanced gastric cancer (AGC). However, not all patients with HER2-positive AGC seem to benefit from trastuzumab. We evaluated the association between treatment outcomes with trastuzumab and HER2 status in patients with HER2-positive AGC. We enrolled 126 patients with HER2-positive AGC treated with trastuzumab plus chemotherapy in a training cohort. HER2 IHC (N = 126), HER2/CEP17 ratio (N = 66), and HER2 gene copy number (GCN; N = 59) were analyzed, and the optimal values for discriminating overall survival (OS) were determined using receiver operating characteristic (ROC) curve analysis. We validated the findings from the training cohort using an independent validation cohort (N = 72). Patients with HER2 IHC 3+ showed significantly longer OS (29 vs. 15.3 months; P = 0.025) than patients with IHC ≤ 2+. An HER2/CEP17 ratio of 4.48 was the optimal cutoff for predicting longer OS (26.9 vs. 14.7 months; P = 0.027). In subgroup analysis, treatment outcomes of patients with IHC 3+ were not influenced by the level of HER2 gene amplification. However, in patients with IHC ≤ 2+, an HER2/CEP17 ratio more than 3.69 and HER2 GCN more than 7.75 were positive predictive factors for better outcomes with trastuzumab-based chemotherapy. These findings were confirmed in both the validation cohort and the combined cohort. HER2 IHC status, HER2/CEP17 ratio, and HER2 GCN were correlated with clinical outcomes of trastuzumab-based treatment in HER2-positive AGC. Clinical outcomes of patients with IHC ≤ 2+ were strongly dependent on the HER2/CEP17 ratio and HER2 GCN.

Relationship between levels of HER-2 amplification and pathologic complete response to trastuzumab-based neoadjuvant treatment.

e11605 Background: Fluorescence in situ hybridization (FISH) is used to determine human epidermal growth factor receptor-2 (HER-2) status and patients (pts) eligibility for trastuzumab therapy. Usi...

Abstract PD5-7: PTEN and PIK3CA but not p4EBP1 are associated with low rates of pathological complete response (pCR) to trastuzumab based chemotherapy in primary HER2-overexpressing breast cancer

Abstract Background: Phosphatidylinositol 3-kinase (PI3K)/AKT pathway and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) aberrations are common in breast cancer (BC). PIK3CA mutation is associated with lower pCR rates especially in patients treated with double anti-HER2 therapy (Loibl et al. JCO accepted). Another mechanism of resistance for trastuzumab-based treatment could be loss of PTEN, resulting also in downstream activation of the pathway. We investigated the correlation between PIK3CA, PTEN, p4EBP1 (phosphorylated E4 binding protein 1) and pCR in pts receiving neoadjuvant therapy. Methods: In addition to PIK3CA we retrospectively evaluated PTEN and p4EBP1 by immunohistochemistry in HER2+ patients who received EC followed by docetaxel within the G4 study (Untch et al. 2011). The G4 study demonstrated a higher pCR rate by adding trastuzumab to chemotherapy. HER2 and hormone receptors (HR) were centrally assessed. PTEN was assessed using the automated quantitative immunofluorescence analysis (Aqua) using an antibody (Cell Signalling Technology). p4EBP1 assessed by immunohistochemistry with an immunreactive score ranging from 0-12. PTEN was categorized by an optimized cut-off determined by the cut-off finder software (http://molpath.charite.de/cutoff/) and p4EBP1 was measured as a continuous variable and correlated with PIK3CA genotype and pCR (ypT0, ypN0). Central HER2+ve cases with a tumor cell content of ≥20% were selected (n=181). Results: Median age was 48years (22-77); HR+ve 51%; Grade 3, 47.4%; pCR rate 32%. p4EBP1 analysis was available from 137 and PTEN from 108 patients. PIK3CA genotype was available in 83 of these patients. 58 pts had PIK3CA and PTEN assessable, 14/58 had a PIK3CA mutation (mut) (25%). Overall, pCR rate in PTEN low tumors was 27.6% vs 57.1% in PTEN high (p=0.010). Within the PIK3CA mut cohort 13/14 (92.9%) tumors were PTEN low. Within the PIK3CA wild-type (wt) cohort 30/44 (68.2%) were PTEN low (p=0.066). The tumours were grouped into 4 subsets using PIK3CA (mut vs wt) and PTEN (low vs. high). pCR rate was 57.1% (8/14) in PTEN high/PIK3CA wt cohort and decreased to 15.4% in the PTEN low/PIK3CA mut cohort. The group with either PTEN low and PIK3CA wt or PTEN high and PIK3CA mut had a pCR rate of 32.2% (p=0.015). In multivariable analysis after adjustment for baseline parameters PTEN was an independent predictor for pCR in the complete cohort (OR 12.3 [95% 1.82-82.9] p=0.010) and in PIK3CA wt cohort (OR 10.3 [95% CI 1.31-81.62] p=0.027). Within the HR+ve group PTEN low tumors had a pCR rate of 22.2% vs 61.5% in the PTEN high group (p=0.007). In multivariable analysis PTEN was independently predictive for pCR in the HR+ve group (OR 49.5 [95% 3.4-707] p=0.004). p4EBP1 correlated weakly with PIK3CA (p=0.049) but not with PTEN. There was no association of p4EBP1 with pCR. Conclusion: Low PTEN was significantly associated with lower pCR and added independent predictive information not only in the overall HER2+ve cohort but also in the PIK3CA wt and HR+ve cohort. It will be confirmed in a larger sample size if PTEN assessment adds information to PIK3CA genotype to select patients with low pCR rates after trastuzumab therapy. Citation Format: Sibylle Loibl, Silvia Darb-Esfahani, Alexander Klimowicz, Gunter von Minckwitz, Bianca Lederer, Jens Huober, Arndt Hartmann, Holger Eidtmann, Berit Maria Pfitzner, Peter A Fasching, Katharina Tiemann, Christian Jackisch, Keyur Mehta, Michael Untch, Carsten Denkert. PTEN and PIK3CA but not p4EBP1 are associated with low rates of pathological complete response (pCR) to trastuzumab based chemotherapy in primary HER2-overexpressing breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr PD5-7.

Abstract P6-14-01: A class I histone deacetylase inhibitor, entinostat, enhances lapatinib efficacy in both HER2-overexpressing inflammatory and non-inflammatory breast cancer cells through FOXO3-mediated Bim1 expression

Abstract Background: Human epidermal growth factor receptor 2 (HER2) overexpression has been reported in 15%-20% of breast cancers and is associated with shorter survival and worse clinical outcome. Inflammatory breast cancer (IBC), a very aggressive subtype of advanced breast cancer, accounts for approximately 2% of all breast cancers and 8%-10% of all breast cancer-related deaths in the United States. Recent study represented that about 60% of IBCs overexpress HER2. Although there are effective HER2-targeted agents, patients with HER2+ breast cancer often have intrinsic and acquired resistance to the anti-HER2 agents that are currently approved by the U.S. Food and Drug Administration. Therefore, novel combination strategies are needed to treat HER2+ breast cancers that develop drug resistance. To this end, we investigated the combinational effect of entinostat, an oral isoform-selective histone deacetylase type I inhibitor, and lapatinib, a HER2/epidermal growth factor receptor dual tyrosine kinase inhibitor, in HER2+ inflammatory breast cancer (IBC) and non-IBC breast cancer cells. Methods: We assessed the combinational synergistic effect and its mechanism via CellTiter Blue assay, flow cytometry, anchorage-independent growth, quantitative real-time polymerase chain reaction, small interfering RNA, Western blotting, and mammary fat pad xenograft mouse models. Results: We found that compared with entinostat or lapatinib alone, the two drugs in combination synergistically inhibited tumor cell proliferation (P < 0.001), reduced in vitro colony formation (P < 0.05), and resulted in significant in vivo tumor shrinkage or growth inhibition in both IBC and non-IBC xenograft mouse models (SUM190 and BT474, P < 0.001). The synergistic antitumor activity of the entinostat-lapatinib combination was due to downregulation of phosphorylated Akt, which induced the transcriptional activity of FOXO3, resulting in the induction of Bim1 (a BH3 domain-containing pro-apoptotic protein). Furthermore, entinostat sensitized trastuzumab/lapatinib-resistant HER2+ cells to the trastuzumab-lapatinib combination and enhanced the anti-proliferation effect compared with single-agent with lapatinib or combination treatment with lapatinib and trastuzumab. Conclusion: Taken together, our data provide evidence that entinostat has enhanced antitumor effect in combination with the HER2-targeted reagent lapatinib and results in the induction of apoptosis by FOXO3-mediated Bim1 expression. Our findings justify conducting a clinical trial (clinicaltrial.gov, NCT01434303) of combinational treatment with entinostat, lapatinib, and trastuzumab in patients with HER2+ IBC or non-IBC that is resistant to trastuzumab-based treatment. Citation Format: Jangsoon Lee, Chandra Bartholomeusz, Gabriel N Hortobagyi, Peter Ordentlich, Naoto T Ueno. A class I histone deacetylase inhibitor, entinostat, enhances lapatinib efficacy in both HER2-overexpressing inflammatory and non-inflammatory breast cancer cells through FOXO3-mediated Bim1 expression [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-14-01.

Abstract P5-19-25: Multi-institutional retrospective analysis of clinical and pathological factors predicting resistance to lapatinib-based therapy in HER2 positive metastatic breast cancer (HER2+ MBC)

Abstract Background The combination of the dual HER1/HER2 inhibitor lapatinib (L) and capecitabine (C) is a therapeutic option for patients (pts) with HER2+MBC whose disease progresses after treatment with the monoclonal antibody trastuzumab. At present time, no clinical or pathological factors except HER2 status are clearly recognized as predictors of the activity of LC. We conducted a retrospective analysis of pts with HER2-positive metastatic breast cancer receiving LC after trastuzumab failure to identify factors associated with resistance to LC. Materials and methods We collected clinical and pathological data from 151 pts with HER2+ MBC receiving LC after failing a prior trastuzumab-based treatment (either adjuvant or for metastatic disease) treated at 13 Italian Institutions between March 2007 and December 2013. Time to progression (TTP) and overall survival (OS), calculated by the Kaplan Meier (KM) method, were from LC treatment beginning to disease progression or to death in the absence of progression (TTP), and to the date of death or to the date of last follow-up (OS), respectively. LC resistance was defined as TTP from treatment initiation lower or equal to the median TTP for the overall population. KM curves were compared by the Log-rank test. Logistic regression analysis was used to study predictors of TTP below the median value for patients receiving LC. Analyses were performed using SPSS version 17.0 (SPSS Inc., Chicago, IL). Results At a median follow-up of 41 months (IQR 23-62), median TTP to LC therapy was 7 months (IQR 5.5-8.5) and median OS was 18 months (IQR 10-28). Fifteen pts were excluded because of short follow-up (i.e. on LC treatment and <7 months of fu). Of the remaining 136, a total of 74 pts with a PFS≤7 months were defined LC-resistant (LC-R) and a total of 62 pts were defined LC-sensitive (LC-S). All clinical and pathological variables analyzed resulted evenly distributed between the two groups, except best tumor response (CR+PR) to LC, which was higher in patients with LC-S disease (72% vs 29%, p<0.001). Conversely, best tumor response in LC-R patients showed higher rates of PD (43% vs 2%, p<0.001). Median OS was 14 months (IC 95% 11.4-22.6) and 26 months (IC 95% 22.5-29.5) in LC-R and LC-S pts, respectively (p<0.001). Although we could not find independent predictors of LC-R, factors indicating failure of the first-line trastuzumab based therapy, as PD as best tumor response and short duration of first-line trastuzumab, were associated to LC-R. Conclusions A short time to progression during capecitabine and lapatinib (LC-R) is associated with reduced OS in patients failing prior trastuzumab based therapy for HER2+ MBC. Patients who had modest clinical benefit from previous trastuzumab-based therapy could experience LC-R indicating the possibility of primary resistance to anti HER2-treatment. For these patients, alternative targeting strategies are urgently needed. Citation Format: Stefania Gori, Valentina Rossi, Monica Turazza, Elena Fiorio, Alessandra Fabi, Giancarlo Bisagni, Jennifer Foglietta, Daniele Santini, Ida Pavese, Alberto Zambelli, Patrizia Vici, Vita Leonardi, Sandro Barni, Silvana Saracchini, Giuseppe Bogina, Simona Duranti, Alessandro Inno, Gianluigi Lunardi, Filippo Montemurro. Multi-institutional retrospective analysis of clinical and pathological factors predicting resistance to lapatinib-based therapy in HER2 positive metastatic breast cancer (HER2+ MBC) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-19-25.

Abstract PD3-1: Evaluation and clinical impact of intra-tumor heterogeneity (ITH) in primary HER2-overexpressing breast cancers (HER2+BC) treated with adjuvant trastuzumab and chemotherapy (CT)

Abstract Background: Despite the success of trastuzumab, when added to CT, for the treatment of women with primary HER2+ BC, diversity in clinical responses and survival are still observed. ITH or the presence of subclonal populations is theorized to be a cause of drug resistance. In this study, we investigated if ITH that could be estimated from a single sample taken at primary surgery from patients with newly-diagnosed HER2+ disease and if ITH was associated with poorer clinical outcomes despite adjuvant trastuzumab-based treatment. Methods: Fifty-two frozen tumor and matched germline samples were taken from patients diagnosed with primary HER2+BC and treated with adjuvant trastuzumab and CT with a median follow-up of 6.3yrs (range 1.5-13). There were 10 (19%) invasive relapses, 7 (13%) distant relapses and 5 (9.6%) deaths. We performed tumor and germline whole exome sequencing (WES), tumor and germline copy number (CN) data profiling (Affymetrix SNP6.0), tumor gene expression (Affymetrix U133 2.0Plus). Variants were called with MuTect, CNs were called using GISTIC. We developed a novel bioinformatics method that integrated WES variant allele fractions, purity estimates and SNP data to delineate the presence of single or multiple genetically distinct subclones. We confirmed our estimated tumor ploidy using flow cytometry on 9 samples. We investigated the association between the presence of ITH and survival using multivariate Cox regression analyses. Results: We observed in HER2+ BCs the presence of substantial chromosomal instability, numerous CN alterations and aneuploidy. With regards to their genomic architecture, 76.9% (40/52) displayed the presence of at least one aneuploid subclone, where the median ploidy was 3.3 (range:1.7-6.3) copies. Multiple distinct subclones or the presence of ITH could be clearly detected in 35/52 (67.3%) samples, 8/52 (15.4%) had evidence of only a single clone, whilst in 9/52 (17.3%) samples their genomic structure could not be definitively determined. The existence of ITH was significantly associated with invasive relapse after adjustment (HR:4.38;95%CI:1.61-7.14;p=0.002) with estrogen receptor and nodal status also remaining significant in the Cox model–in contrast, the absence of ITH was associated with excellent outcomes (no distant relapses). Other surrogates of genomic instability (gene expression signature [CIN70] and SNP signature [Genomic Instability Index]) were not significantly associated with survival in this dataset. As exploratory analyses, potential genetic drivers of ITH were investigated. PIK3CA (n=13,p=0.008), MED1 (n=3,p=0.03) and IKZF1 (n=3,p=0.03) mutations, amplifications in 8q22.2 (n=7,p=0.008) as well as deletion in 1q24.2 (n=5, p=0.006) were associated with the presence of a single clone, whereas we did not find any genetic drivers with significant associations with ITH. Conclusions: We show for the first time that the presence of ITH in primary HER2+ tumors is associated with worse outcomes despite adjuvant trastuzumab and CT. These findings should be evaluated in larger cohorts. Citation Format: Sherene Loi, Peter Savas, Ingrid Lonnstedt, Debora Fumagalli, Franco Caramia, Jason Li, Roberto Salgado, Andrew Rowan, Fabrice Andre, Carsten Denkert, Patrick Neven, Sibylle Loibl, Christos Sotiriou, Charles Swanton, Terence P Speed. Evaluation and clinical impact of intra-tumor heterogeneity (ITH) in primary HER2-overexpressing breast cancers (HER2+BC) treated with adjuvant trastuzumab and chemotherapy (CT) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr PD3-1.

Predictive and prognostic significance of p27, Akt, PTEN and PI3K expression in HER2-positive metastatic breast cancer.

The phosphatidylinositol 3'-kinase/Akt (PI3K/Akt) pathway is a key regulator for HER2- overexpressing breast cancer, but data about whether activation of PI3K/Akt is associated with poor prognosis and resistance to trastuzumab therapy is controversial. In this study we investigated predictive and prognostic significance of expression of p27, Akt, PTEN and PI3K, which are components of the PI3K/Akt signaling pathway, in HER2-positive metastatic breast cancer (MBC), retrospectively. Fifty-four HER2- positive MBC patients who had received first-line trastuzumab-based therapy were recruited for the study group. All of the patient's breast tissue samples were examined for p27 and Akt expression. In addition, twenty-five patients with sufficient amount of tumor tissue were also examined for PTEN and PI3K expression. p27, Akt, PTEN and PI3K were evaluated by immunohistochemistry and their relationship with patient demographic features, tumor characteristics, response to trastuzumab-based treatment and survival outcomes were analyzed. p27, Akt, PTEN and PI3K were positive in 25.9%, 70.4%, 24% and 96% of the cases, respectively. Nomne were significantly associated with response to trastuzumab and time to progression (TTP). A trend toward statistical significance for longer overall survival (OS) was found for PTEN-positive patients (p=0.058); there was no significant relationship between the other immunohistochemical variables and OS. When we analyzed groups regarding co-expression, the PTEN-negative/Akt-negative group had a significantly lower objective response rate (ORR) (20% vs 80%, p=0.023) and the PTEN-negative/p27-negative and PTEN-negative/Akt-negative groups had significantly lower median OS compared to other patients (26.4 months vs 76.1 months, p=0.005 and 25.6 months vs 52.0 months, p=0.007, respectively). p27, Akt, PTEN and PI3K expression is not statistically significantly associated with ORR, TTP and OS, individually. However, the combined evaluation of p27, Akt and PTEN could be helpful to predict the response to trastuzumab-based therapy and prognosis in HER2-positive MBC.

Mucolytic Agents Can Enhance HER2 Receptor Accessibility for [(89)Zr]Trastuzumab, Improving HER2 Imaging in a Mucin-Overexpressing Breast Cancer Xenograft Mouse Model.

Binding of trastuzumab to HER2 receptors can be impaired by steric hindrance caused by mucin MUC4. As mucolytic drugs can breakdown disulfide bonds of mucoproteins, we checked if this approach could positively affect zirconium-89-labeled trastuzumab ([(89)Zr]T) binding/uptake. The effect of N-acetylcysteine (NAC) and MUC4 knockdown/stimulation on [(89)Zr]T binding/uptake were evaluated in MCF7(HER2-), BT474 and SKBr3(HER2+/MUC4-), and JIMT1(HER2+/MUC4+) cell lines. The results were then validated in SKBR3 and JIMT1 tumor-bearing nude mice with a microPET-CT and ex vivo analysis. Significant increases in [(89)Zr]T binding/uptake were observed in JIMT1 cells following MUC4 knockdown (62.4 ± 6.5%) and exposure to NAC (62.8 ± 19.4%). Compared to controls, mice treated with NAC showed a significant increase in [(89)Zr]T uptake in MUC4 tumors on microPET-CT (SUVmean (18.3 ± 4.7%), SUVmax (41.7 ± 8.4%)) and individual organ counting (37.3 ± 18.3%). In contrast, no significant differences were observed in SKBr3. NAC can enhance [(89)Zr]T accumulation and improve the HER2 imaging of MUC4-overexpressing tumors. The potential positive impact on trastuzumab-based treatment deserves further investigation.

Factors predicting lapatinib efficacy in HER-2+ metastatic breast carcinoma: Does it work better in different histologic subtypes?

Introduction of trastuzumab, a recombinant monoclonal antibody against the extracellular domain of HER-2, is a cornerstone in the treatment of HER-2+ breast carcinoma. However, many cancers that have an initial response to trastuzumab will progress some time later. After progression on trastuzumab-based first-line treatment, there are several options. Although TDM-1 (Trastuzumab emtansine) has prolonged progression-free survival (PFS) and overall survival in patients previously treated with trastuzumab and taxane, it is still not available in Turkey. Patients may be switched to lapatinib (an oral tyrosine kinase inhibitor targeting both HER-1 and HER-2), or they may re-challenge with trastuzumab. There is no clear definition of the patients who should be switched to lapatinib. In this study, we investigated the factors predicting the efficacy of lapatinib. Totally, 94 patients treated with lapatinib for metastatic breast carcinoma was included in our study. Retrospective data including pathology, treatments and treatment results, metastatic sites, and laboratory tests were collected. Progression-free survival was 9.1 months. Histologic subtypes other than invasive ductal carcinoma and liver metastasis were inversely related with PFS. Overall survival was 22.1 months, and patients with histologic subtypes other than invasive ductal carcinoma and who progress with brain metastasis had a worse prognosis. Clinicians should give attention to histologic subtype and metastatic sites when choosing patients for lapatinib treatment.

An integrative analysis of PIK3CA mutation, PTEN, and INPP4B expression in terms of trastuzumab efficacy in HER2-positive breast cancer.

The phosphoinositide-3-kinase (PI3K) pathway is commonly deregulated in breast cancer through several mechanisms, including PIK3CA mutation and loss of phosphatase and tensin homolog (PTEN) and inositol polyphosphate 4-phosphatase-II (INPP4B). We aimed to evaluate the predictive relevance of these biomarkers to trastuzumab efficacy in HER2-positive disease. We evaluated the effect of trastuzumab in 43 breast cancer patients with HER2-overexpression who received neoadjuvant treatment. PIK3CA mutation was examined by direct sequencing and digital PCR assay, and PIK3CA copy number was assessed by digital PCR assay of pretreatment tissues. PTEN, pAkt, and INPP4B were assessed by immunohistochemistry. Direct sequencing detected mutant DNA in 21% of all patients, but the incidence increased to 49% using digital PCR. The pathological complete response (pCR) rate in patients with PIK3CA mutations was 29% compared with 67% for those without PIK3CA mutations (P = 0.093), when the mutation was defined as positive if the mutant proportion was more than 10% of total genetic content by digital PCR. Low PTEN expression was associated with less pCR compared to high expression (33% versus 72%, P = 0.034). There were no significant associations of PIK3CA copy number, pAKt, or INPP4B with trastuzumab efficacy. In multivariate analysis, activation of the PI3K pathway due to either PIK3CA mutation or low PTEN were related to poorer response to trastuzumab (OR of predictive pCR was 0.11, 95%CI; 0.03–0.48). In conclusion, activating the PI3K pathway is associated with low pCR to trastuzumab-based treatment in HER2-positive breast cancer. Combined analysis of PIK3CA mutation and PTEN expression may serve as critical indicators to identify patients unlikely to respond to trastuzumab.

A class I histone deacetylase inhibitor, entinostat, enhances lapatinib efficacy in HER2-overexpressing breast cancer cells through FOXO3-mediated Bim1 expression.

Although there are effective HER2-targeted agents, novel combination strategies in HER2-overexpressing breast cancers are needed for patients whose tumors develop drug resistance. To develop new therapeutic strategy, we investigated the combinational effect of entinostat, an oral isoform-selective histone deacetylase type I inhibitor, and lapatinib, a HER2/EGFR dual tyrosine kinase inhibitor, in HER2+ breast cancer cells. We assessed the combinational synergistic effect and its mechanism by CellTiter Blue assay, flow cytometry, anchorage-independent growth, quantitative real-time PCR, small interfering RNA, Western blotting, and mammary fat pad xenograft mouse models. We found that compared with entinostat or lapatinib alone, the two drugs in combination synergistically inhibited proliferation (P < 0.001), reduced in vitro colony formation (P < 0.05), and resulted in significant in vivo tumor shrinkage or growth inhibition in two xenograft mouse models (BT474 and SUM190, P < 0.001). The synergistic anti-tumor activity of the entinostat/lapatinib combination was due to downregulation of phosphorylated Akt, which activated transcriptional activity of FOXO3, resulting in induction of Bim1 (a BH3 domain-containing pro-apoptotic protein). Furthermore, entinostat sensitized trastuzumab/lapatinib-resistance-HER2-overexpressing cells to the trastuzumab/lapatinib combination and enhanced the anti-proliferation effect compare with single or double combination treatment. This study provides evidence that entinostat has enhanced anti-tumor effect in combination with HER2-targeted reagent, lapatinib, and resulting in induction of apoptosis by FOXO3-mediated Bim1 expression. Our finding justifies for conducting a clinical trial of combinational treatment with entinostat, lapatinib, and trastuzumab in patients with HER2-overexpressing breast cancer resistant to trastuzumab-based treatment.

Efficacy of trastuzumab-based therapy after disease progression on lapatinib based therapy in heavily pretreated HER2-positive metastatic breast cancer patients.

e11586 Background: We retrospectively analyzed efficacy of trastuzumab-based chemotherapy in patients whose disease progressed after lapatinib. Methods: Between October 2010 and May 2013, 54 patients whose disease progressed after lapatinib received trastuzumab-based treatment. Survival and toxicity results were evaluated retrospectively. Results: Median age of patients were 46 (27-67), 53 were female and 1 was male. 24 patients (44,4%) were ER-positive and 20 (37%) were PR-positive. 14 patients (25,9%) had metastasis at the time diagnosis. 36 of the patients (66,6%) had received adjuvant/neoadjuvant anthracycline and taxane therapy, while 24 (44,4%) had received adjuvant/neoadjuvant anthracycline and 14 (25,9%) adjuvant trastuzumab therapy. 47 patients had received trastuzumab in metastatic setting and all patients received lapatinib plus capecitabine. Median chemotherapy line for metastatic setting was 2 (1-7), 26 patients (48%) had received at least 3 lines of treatments. 39 patients (72,2%) had at lea...

High‐level ERBB2 gene amplification is associated with a particularly short time‐to‐metastasis, but results in a high rate of complete response once trastuzumab‐based therapy is offered in the metastatic setting

Despite patient selection based on ERBB2 overexpression, not all patients benefit from trastuzumab therapy. We have investigated whether a ERBB2 gene dosage effect might provoke increased biological aggressiveness and altered trastuzumab sensitivity. Absolute ERBB2 copy numbers ("CN") and ERBB2/centromer 17 ratios ("R") were measured by FISH analysis in tumors of 127 patients receiving trastuzumab-based treatment for Her-2/neu overexpressing metastatic breast cancer. CN and R were both significantly associated with shorter time to first metastasis (TTM) (CN: OR: 1.099, 95% CI: 1.042-1.159; R: OR: 1.211, 95% CI: 1.080-1.357) and longer PFS (CN: OR: 0.917, 95% CI: 0.867-0.969; R: OR: 0.840, 95% CI: 0.743-0.949) in a continuous variable Cox's regression model. Tumors with ERBB2/centromer 17 ratios of <2.2 had a significantly shorter TTM (p = 0.002) and significantly longer PFS (p = 0.003) than tumors with low-level (R: 2.2-6) and high-level amplification (R: >6). Interestingly, when ERBB2 copy numbers were analyzed, a significantly shorter TTM (p = 0.001) and longer PFS (p = 0.026) were observed in the group with high-level amplified CN (CN: >13), while no difference was observed between non- and low-level amplified CN. R, but not CN, was an independent predictor of complete (CR; OR: 1.685; 95% CI: 1.122-2.532) and partial (PR; OR: 1.704; 95% CI: 1.136-2.556) response in logistic regression analysis. CR (p = 0.016) rates were significantly higher in the high-level amplification group (R > 6), but no difference existed in response rates between non- and low-level amplified tumors in Chi-square tests. High-level ERBB2 amplification is associated with shorter TTM, but improved response to trastuzumab in metastatic breast cancer.

Abstract P3-14-01: Features of neoadjuvant and adjuvant chemotherapy in breast cancer – A population-based study on 39404 patients

Abstract Background: Neoadjuvant chemotherapy (NACT) is increasingly used globally in clinical trials for breast cancer patients. In Germany, NACT has been implemented as a standard option of care for almost a decade. In a population-based benchmark cohort study, the West German Breast Center (WBC) recorded approximately 50% of all breast cancer cases diagnosed in Germany between 2007 and 2010. We compare baseline and treatment pattern of patients treated either with adjuvant (ACT) or NACT. Methods: Approx. 200 accredited breast centers treated 115169 primary breast cancer patients of whom 32609 received ACT and 6795 NACT. Pathological complete response (pCR) was stated if no invasive and no non-invasive tumor residues (ypT0 ypN0) were detected. Follow up information was available for 55% of patients. Results: Use of NACT increased from 16.4% in 2007 to 19.1% in 2010 (p&amp;lt;.0001). Patients treated with NACT were younger, had higher clinical nodal involvement, fewer lobular-invasive cancers, more undifferentiated, hormone-receptor-negative, and HER2-positive cancers, and more multicentric tumors compared to patients treated with ACT (all p&amp;lt;0.002). 34% of patients in the NACT group had cT3/4 tumors compared to 7.7% of pT3/4 tumors in the ACT group. cN0 status was twice as frequent (70.6% vs 37.7%, p&amp;lt;.0001) whereas pN0 status was reported less frequently (47.4% vs 51.4%, p&amp;lt;0.0001) in the ACT and NACT group, respectively. Time between diagnosis and start of systemic treatment or surgery was in median 12 (range 1-902) and 22 (range 1-721) days in the ACT and NACT group, respectively (p&amp;lt;.0001). 66.2% and 91.4% of patients received ACT and NACT with a taxane, respectively (p&amp;lt;.0001). 9.7% and 37.5% of patients receiving treatment for &amp;gt; = 18 weeks, respectively. 35.2% and 69.9% of patients with HER2-positive tumors received adjuvant or neoadjuvant trastuzumab, respectively (p&amp;lt;.0001). 21.7% and 31.4% of patients were treated in ACT or NACT clinical trials, respectively (p&amp;lt;.0001). Breast conservation was possible in 69.4% and 55.2% in the ACT and NACT group, respectively (p&amp;lt;.0001). 30.5% and 37.5% needed two or more surgical interventions in the ACT and NACT group, respectively (p&amp;lt;.0001). Multivariable logistic regression analysis confirmed taxane- and trastuzumab-based treatment, study participation, age, histologic type, grading, and hormone-receptor status as independent predictors of pCR. pCR rate was not dependent on the time between diagnosis and start of treatment or the time between end of chemotherapy and surgery. In univariate analysis patients receiving NACT showed a 4-year overall survival rate of 78%, compared to 92% in patients receiving ACT (p&amp;lt;.0001). However, patients with a pCR after NACT showed a comparable survival to patients in the ACT group, whereas patients without a pCR showed a 4-year overall survival rate of 76%. In the hormone-receptor-positive/HER2-positive and even more in the triple-negative subgroup, survival of patients with a pCR appeared better than in patients with ACT. Conclusion: In this population-based study, NACT was used in patients with unfavorable risk factors and was more intense than ACT. Outcome of patients with pCR after NACT was similar and in aggressive tumor subtypes even better than after ACT. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-14-01.

Abstract P2-16-08: LORHA: Efficacy and safety of 1st-line trastuzumab based treatment, administered for at least 3 years, in patients with HER2-positive metastatic or locally advanced breast cancer - Final results

Abstract Background: A subset of patients with HER2-positive metastatic (mBC) or locally advanced breast cancer (aBC) respond to 1st line trastuzumab-based regimen and have no disease progression for several years. These long-term responders were evaluated in daily practice in the LORHA study. Patients and disease characteristics were presented earlier (ESMO 2012). Material and Methods: Lorha is an ambispective, multicenter, non-interventional study conducted in 57 centers in France. Eligible patients were women aged more than 18 years with HER2-positive mBC or aBC treated with 1st line trastuzumab and progression-free for at least 3 years after starting trastuzumab. The primary objective was to describe clinical and tumor characteristics. Secondary objectives included Progression Free Survival (PFS), Overall Survival (OS), treatment administration and safety. Patients were followed-up for 12 months. Final results are presented here. Results: Overall 160 patients were enrolled; 128 were eligible for efficacy analysis and 154 for safety analysis. Median age was 61 years [34-95]. Tumor characteristics were: invasive ductal carcinoma for 112 patients (88%), positive hormonal receptors in 72 patients (58%). At initial diagnosis, 91 patients (71%) had stage I - II tumors and 37 patients (29%) had de novo mBC or aBC. The main metastatic localizations were bone, liver, lymph nodes and lung in 54 (43%), 44 (35%), 25 (20%) and 24 (19%) patients, respectively. Median 1st line trastuzumab treatment duration was 4.5 years [0.8 - 12.1]. Trastuzumab 1st line was associated with a taxane-based chemotherapy in 104/128 patients (81%). Median PFS was 6.4 years [5.7; - Not reached] and median overall survival was not reached. At 1-year follow-up, 23 deaths (15% of patients) were reported, mainly due to disease progression (21 patients - 91%). No toxic death related to trastuzumab was observed. Grade 3-4 adverse events reported prospectively occurred in 14 patients (10%) and included two patients (1.2%) with grade 3-4 cardiac events related to trastuzumab (congestive cardiac failure and left ventricular dysfunction), both events resolved, one with sequelae. Conclusions: Final results of the LORHA study show that long responding patients receiving first-line trastuzumab-based treatment for aBC or mBC in daily practice, can reach a median PFS of more than 6 years, combined with an acceptable safety profile. Median overall survival is still not reached. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-16-08.

Abstract P3-14-13: eIF4E/4EBP1 axis and response to neoadjuvant trastuzumab-based treatment in HER2+ breast cancer – Results of a multicentre French retrospective cohort

Abstract Background Despite a growing number of studies exploring the underlying mechanisms, resistance to trastuzumab (TTZ) in HER2+ breast cancer (BC) remains elusive and an important issue in clinical practice. Among the proposed mechanisms, involvement of the PI3K/Akt/mTOR pathway is one of the best characterized. In a previous preclinical and clinical study (n = 54) (Bergé Y et al, SABCS 2009 and [1]), we have shown a significant correlation between eIF4E (a downstream effector of the PI3K/Akt/mTOR pathway) expression level as determined by immunohistochemistry (IHC) on initial tumor biopsy and pathological complete response (pCR) in patients with HER2+ BC treated with a neoadjuvant TTZ-containing regimen. The aim of this study was to validate these findings on an independent and larger cohort of HER2+ BC treated in neoadjuvant setting. Method In this multicenter (n = 9) study, 274 patients (pts) with HER2+ BC treated were included. All pts received neoadjuvant chemotherapy regimen containing TTZ, consisting mostly of 3-4 cycles of FEC (5FU, Epirubicin, Cyclophosphamid) followed by 3-4 cycles of TTZ–Docetaxel (n = 116). 74 pts received 6 cycles of TTZ–Docetaxel, 18 received 6 cycles of TTZ–Docetaxel-Cyclophosphamid, 12 received 6 cycles of TTZ–Docetaxel-carbolpatine, and the remaining 54 pts received other regimens. Pathological response was assessed according to Sataloff and Chevallier criteria. Unstained slides from the initial tumor biopsy were centrally collected for biomarkers analysis. Expression levels of eIF4E, p-4EBP1 and pS6 were determined by IHC. An immunoreactive score (IRS) combining the percentage of stained tumor cells and staining intensity was assessed by two pathologists. Results Median age at diagnosis was 50 years [range 22–84]. Most pts presented with T2 (52.6%), N1 (53.9%) stage, with a median tumor size of 40mm [range 0-150mm] as determined on clinical examination. Tumors were mainly invasive ductal of no special type (93.8%), of histological grade III (50%) and II (45%), ER+ (54.4%). Breast conserving surgery with free margins was achieved in 50.9% of pts. pCR (breast Sataloff TA) was observed in 53% of pts, and in 47.6% when considering both breast and lymph node response. Out of the 274 pts, 257 had sufficient tumor on the initial biopsy for biomarker analysis. Preliminary results showed a median eIF4E IRS of 6 [range 1-12], with 52.1% of cases displaying a low eIF4E expression level (IRS£6). The agreement for inter-observer assessment of eIF4E status was good (k = 0.618, 95% CI [0.523-0.713]). Scoring of p-4EBP1 and pS6 are ongoing and correlations of pCR with eIF4E/4EBP1 axis will be presented. Conclusion In this large multicentre retrospective study, the rate of pCR obtained in neoadjuvant setting of HER2+ BC is similar to those described in the literature. Thorough tumor collection allows biomarkers analysis, which has been specifically focused on downstream effectors of the PI3K/Akt/mTOR pathway. Reference[1] Zindy P, Bergé Y, Allal B et al. Formation of the eIF4F translation-initiation complex determines sensitivity to anticancer drugs targeting the EGFR and HER2 receptors. Cancer Res. 2011;71(12):4068-73. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-14-13.

Clinical outcome in women with HER2-positive de novo or recurring stage IV breast cancer receiving trastuzumab-based therapy

BackgroundFive to 10% of women with newly diagnosed breast cancer have synchronous metastases (de novo stage IV). A further 20% will develop metastases during follow-up (recurring stage IV). We compared the clinical outcomes of women with HER2-positive metastatic breast cancer (MBC) receiving first-line trastuzumab-based therapy according to type of metastatic presentation. Patients and methodsRetrospective analysis of 331 MBC patients receiving first-line trastuzumab-based treatment. Response rates (RR) were compared by the chi-square test. Time-to progression (TTP) and overall survival (OS) curves were compared by the log-rank test. Cox-proportional hazards models were used to study predictors of PFS and OS, including the type of metastatic presentation. ResultsSeventy-seven patients (23%) had de novo stage IV disease. Forty-six of these patients underwent surgery of the primary (“de novo/surgery”). Response rates to first-line trastuzumab-based therapy and median progression-free survival did not differ in patients with “recurring”, “de novo/surgery” and “de novo” without surgery (“de novo/no surgery) stage IV breast cancer. However, women with “de novo/surgery” stage IV breast cancer had the longest median OS (60 months), and those with “de novo/no surgery” stage IV breast cancer the shortest (26 months). For women with recurring metastatic breast cancer median OS was 40 months (overall log-rank test, p < 0.01). Multivariate analysis confirmed these findings. ConclusionOur analysis shows that response rates and PFS to first-line trastuzumab-based therapy do not differ significantly between de novo and recurring stage IV, HER2 positive breast cancer. The observed difference in OS favoring women with de novo stage IV disease submitted to surgery of the primary tumor could be the result of a selection bias.

Do pharmaceutical claims accurately reflect oncology prescribing practice? Evidence from an Australian HER2+ early breast cancer cohort (HER2EBC).

100 Background: Pharmaceutical claims are used increasingly to investigate the real-world use and impact of prescribed medicines. Claims databases are established for payment purposes, lack clinical data and only capture prescriptions for which insurers pay a contribution. We compare Pharmaceutical Benefits Scheme (PBS) dispensing claims of HER2EBC patients, with prescriptions written in oncology clinics to determine the accuracy of dispensing data to identify treatment protocols and estimate treatment cycles and durations of therapy. Methods: Our cohort comprised 110 female HER2EBC patients commencing treatment at 4 Sydney cancer centres between 2008 and 2011. Patients consented to medical chart audit and linkage to PBS claims. We constructed protocols from prescribing and dispensing records independently, based on the timing of trastuzumab and cytotoxic treatments; estimated the median number of treatment cycles and duration of therapy by protocol; and compared prescription and dispensing data. Results: Patients’ median age was 53 years (range 21.1-86.2). Based on prescribing data, 67 patients received anthracycline-containing protocols, 43 received taxane only protocols. ACTH and TCH accounted for 90% of all protocols. 75 patients (68.2%) were assigned the same protocols based on prescribing and claims data; 26 did not match as cyclophosphamide falls below the patient copayment for general PBS beneficiaries and is not captured in the claims data. Compared with prescription data, number of treatment cycles was underestimated in dispensing data (ACTH: median 30 vs 44; TCH 26 vs 29); trastuzumab-based treatment is administered weekly in ACTH but only dispensed 3-weekly. Durations of therapy differed by ≤5% in dispensing versus prescription data (ACTH 422 days vs 466; TCH 368 vs 367). Conclusions: PBS dispensing data is reliable for establishing treatment protocols in concessional beneficiaries and duration of therapy in all patients. Claims data underestimates treatment cycles as administration occurs more frequently than dispensing. These limitations must be considered when undertaking population-based studies using claims data in HER2EBC.

Over 17-month complete clinical brain response with a well-tolerated lapatinib plus capecitabine combination in a very young patient afflicted by HER2-positive metastatic breast cancer

This report describes a case of ab initio metastatic HER2-positive breast cancer in a very young patient. The onset of breast cancer at such a young age is uncommon and could delay the diagnosis with unquestionable impact on the prognosis. Unfortunately, the patient experienced cerebral progression during first-line treatment. Indeed, brain metastases occur in about one-third of HER2-positive metastatic breast cancer patients during trastuzumab-based treatment. The small molecule lapatinib is active in established cerebral disease, and we report a complete brain response longer than expected, thanks to a well-tolerated, orally administered combination of lapatinib and capecitabine.