Comparative genomic analysis of PIK3R1-mutated and wild-type breast cancers

PURPOSE

The PIK3R1 gene encodes the regulatory subunit-p85a-of the PI3K signaling complex. Prior studies have found that pathogenic somatic alterations in PIK3R1 are enriched in human breast cancers but the genomic landscape of breast cancer patients harboring PIK3R1 mutations has not been extensively characterized.

METHODS

We retrospectively analyzed 6,009 patient records that underwent next-generation sequencing (NGS) using the Tempus xT solid tumor assay. All patients had breast cancer with known HER2 (+/-) and hormone receptor (HR; +/-) status and were classified according to the presence of PIK3R1 mutations including short variants and copy number alterations.

RESULTS

The frequency of PIK3R1 mutations varied according to subtype: 6% in triple negative (TNBC, 89/1,475), 2% in HER2-/HR+ (80/3,893) and 2.3% in HER2+ (15/641) (p < 0.001). Co-mutations in PTEN, TP53 and NF1 were significantly enriched, co-mutations in PIK3CA were significantly less prevalent, and tumor mutational burden was significantly higher in PIK3R1-mutated HER2- samples relative to PIK3R1 wild-type. At the transcriptional-level, PIK3R1 RNA expression in HER2- disease was significantly higher in PIK3R1-mutated (excluding copy number loss) samples, regardless of subtype.

CONCLUSION

This is the largest investigation of the PIK3R1 mutational landscape in breast cancer patients (n = 6,009). PIK3R1 mutations were more common in triple-negative breast cancer (~ 6%) than in HER2 + or HER2-/HR + disease (approximately 2%). While alterations in the PI3K/AKT pathway are often actionable in HER2-/HR + breast cancer, our study suggests that PIK3R1 could be an important target in TNBC as well.

Efficacy and Safety of Trastuzumab as a Single Agent in First-Line Treatment of HER2-Overexpressing Metastatic Breast Cancer

PURPOSE

To evaluate the efficacy and safety of first-line, single-agent trastuzumab in women with HER2-overexpressing metastatic breast cancer.

PATIENTS AND METHODS

One hundred fourteen women with HER2-overexpressing metastatic breast cancer were randomized to receive first-line treatment with trastuzumab 4 mg/kg loading dose, followed by 2 mg/kg weekly, or a higher 8 mg/kg loading dose, followed by 4 mg/kg weekly.

RESULTS

The objective response rate was 26% (95% confidence interval [CI], 18.2% to 34.4%), with seven complete and 23 partial responses. Response rates in 111 assessable patients with 3+ and 2+ HER2 overexpression by immunohistochemistry (IHC) were 35% (95% CI, 24.4% to 44.7%) and none (95% CI, 0% to 15.5%), respectively. The clinical benefit rates in assessable patients with 3+ and 2+ HER2 overexpression were 48% and 7%, respectively. The response rates in 108 assessable patients with and without HER2 gene amplification by fluorescence in situ hybridization (FISH) analysis were 34% (95% CI, 23.9% to 45.7%) and 7% (95% CI, 0.8% to 22.8%), respectively. Seventeen (57%) of 30 patients with an objective response and 22 (51%) of 43 patients with clinical benefit had not experienced disease progression at follow-up at 12 months or later. The most common treatment-related adverse events were chills (25% of patients), asthenia (23%), fever (22%), pain (18%), and nausea (14%). Cardiac dysfunction occurred in two patients (2%); both had histories of cardiac disease and did not require additional intervention after discontinuation of trastuzumab. There was no clear evidence of a dose-response relationship for response, survival, or adverse events.

CONCLUSION

Single-agent trastuzumab is active and well tolerated as first-line treatment of women with metastatic breast cancer with HER2 3+ overexpression by IHC or gene amplification by FISH.

Multinational Study of the Efficacy and Safety of Humanized Anti-HER2 Monoclonal Antibody in Women Who Have HER2-Overexpressing Metastatic Breast Cancer That Has Progressed After Chemotherapy for Metastatic Disease

PURPOSE

Overexpression of the HER2 protein occurs in 25% to 30% of human breast cancers and leads to a particularly aggressive form of the disease. Efficacy and safety of recombinant humanized anti-HER2 monoclonal antibody as a single agent was evaluated in women with HER2-overexpressing metastatic breast cancer that had progressed after chemotherapy for metastatic disease.

PATIENTS AND METHODS

Two hundred twenty-two women, with HER2-overexpressing metastatic breast cancer that had progressed after one or two chemotherapy regimens, were enrolled. Patients received a loading dose of 4 mg/kg intravenously, followed by a 2-mg/kg maintenance dose at weekly intervals.

RESULTS

Study patients had advanced metastatic disease and had received extensive prior therapy. A blinded, independent response evaluation committee identified eight complete and 26 partial responses, for an objective response rate of 15% in the intent-to-treat population (95% confidence interval, 11% to 21%). The median duration of response was 9.1 months; the median duration of survival was 13 months. The most common adverse events, which occurred in approximately 40% of patients, were infusion-associated fever and/or chills that usually occurred only during the first infusion, and were of mild to moderate severity. These symptoms were treated successfully with acetaminophen and/or diphenhydramine. The most clinically significant adverse event was cardiac dysfunction, which occurred in 4.7% of patients. Only 1% of patients discontinued the study because of treatment-related adverse events.

CONCLUSION

Recombinant humanized anti-HER2 monoclonal antibody, administered as a single agent, produces durable objective responses and is well tolerated by women with HER2-overexpressing metastatic breast cancer that has progressed after chemotherapy for metastatic disease. Side effects that are commonly observed with chemotherapy, such as alopecia, mucositis, and neutropenia, are rarely seen.

Multiomic approach to examining gut microbiome sampling methods in breast cancer and control subjects

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Background: It is well known that estrogen exposure is a major risk factor for breast cancer (BC). Estrogen levels can be affected by the gut microbiome through enterohepatic circulation. No studies regarding gut microbiome changes in BC have examined the colonic mucosal microbiome; and there is no data on which types of gut microbiome studies would be most relevant to the study of the microbiome in BC. Methods: We examined differences in the gut microbiome composition in BC and control subjects using the following sample types: Home-collected stool, endoscopically collected stool, and colonic biopsy samples (for all groups, n=48 total, n=24 BC, n=24 controls). Here, we used both operational taxonomic unit (OTU) and amplicon sequence variant (ASV) based approaches in QIIME2 for 16S rDNA sequencing analysis. Alpha diversity metrics (Chao1, Pielou’s Evenness, Faith PD, Shannon, and Simpson) and beta diversity metrics (Bray-Curtis, Weighted and Unweighted Unifrac) were calculated. LefSe was used to analyze differences in the abundance of various taxa between sample types. Results: Alpha and beta diversity metrics were different between the three sample types when using both OTU or ASV-based analysis, however there were some minor differences between analysis types in these samples. Comparing the 3 sample types, Actinobacteria and Firmicutes (Log10 LDA score >4) were the predominant phyla in home stool samples, while Bacteroidetes and Proteobacteria (Log10 LDA score >4) were higher in abundance in the colonic biopsy samples. Conclusions: Our data shows that alpha and beta diversity metrics differ between sampling methods (home-collected stool, endoscopically collected stool, and colonic biopsies) when looking at the composition of the gut microbiome in BC. Results remained the same regardless of ASV or OTU-based analysis. [Table: see text]

Comparison of Radiation With or Without Concurrent Trastuzumab for HER2-Positive Ductal Carcinoma In Situ Resected by Lumpectomy: A Phase III Clinical Trial

PURPOSE

Preclinical studies report that trastuzumab (T) can boost radiotherapy (RT) effectiveness. The primary aim of the B-43 trial was to assess the efficacy of RT alone vs concurrent RT plus T in preventing recurrence of ipsilateral breast cancer (IBTR) in women with ductal carcinoma in situ (DCIS).

PATIENTS AND METHODS

Eligibility: Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, DCIS resected by lumpectomy, known estrogen receptor (ER) and/or progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2) status by centralized testing. Whole-breast RT was given concurrently with T. Stratification was by menopausal status, adjuvant endocrine therapy plan, and nuclear grade. Definitive intent-to-treat primary analysis was to be conducted when either 163 IBTR events occurred or all accrued patients were on study ≥ 5 years.

RESULTS

There were 2,014 participants who were randomly assigned. Median follow-up time as of December 31, 2019, was 79.2 months. At primary definitive analysis, 114 IBTR events occurred: RT arm, 63 and RT plus T arm, 51 (hazard ratio [HR], 0.81; 95% CI, 0.56 to 1.17; P value = .26). There were 34 who were invasive: RT arm, 18 and RT plus T arm, 20 (HR, 1.11; 95% CI, 0.59 to 2.10; P value = .71). Seventy-six were DCIS: RT arm, 45 and RT plus T arm, 31 (HR, 0.68; 95% CI, 0.43 to 1.08; P value = .11). Annual IBTR event rates were: RT arm, 0.99%/y and RT plus T arm, 0.79%/y. The study did not reach the 163 protocol-specified events, so the definitive analysis was triggered by all patients having been on study for ≥ 5 years.

CONCLUSION

Addition of T to RT did not achieve the objective of 36% reduction in IBTR rate but did achieve a modest but statistically nonsignificant reduction of 19%. Nonetheless, this trial had negative results. Further exploration of RT plus T is needed in HER2-positive DCIS before its routine delivery in patients with DCIS resected by lumpectomy.

Binimetinib activity in PIK3R1-mutant patient-derived xenografts (PDX) implanted into immunodeficient mice

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Background: The PIK3R1 gene is genetically altered in ̃3% of breast cancers in the Western and ̃17% in the Eastern worlds. We recently reported that breast cancer cells lacking protein expression of PIK3R1 had elevated levels of activated MEK, sensitizing them to the MEK inhibitor trametinib. To better understand whether MEK inhibition is a therapeutic option for breast cancer patients with mutated PIK3R1, we tested the newer generation MEK inhibitor, binimetinib, in a PDX mouse model. Methods: Two PDx models (table) were tested in athymic nude-foxn1nu (immune-compromised) mice. Both patients had had metastatic, grade 3 breast cancer and expressed moderate RNA levels of PIK3R1. Results: Body weights of treatment arms were unchanged throughout the experiment. The TNBC PDx study was halted early at 13 days because tumors reached the predefined maximum size of 1500 mm2. The binimetinib treated mice experienced slowed tumor growth (522.8 +/- 172.8%) compared to the vehicle control (720.7 +/- 229.1%), (p=0.0693). In the HR+ PDx model, the combination of binimetinib plus tamoxifen resulted in a statistically significant decrease (371.5 +/- 108.1%) in tumor volume compared to tamoxifen alone (525.0 +/- 154.1%; p = 0.0302). Conclusions: Our previous and current results suggest that mutation in PIK3R1 sensitizes cells to MEK inhibitors. Binimetinib inhibited growth in both models. This inhibition was of borderline significance in the TNBC model and was statistically significant in the ER+, HER2- model. To the best of our knowledge, these results provide the first evidence of binimetinib efficacy in PIK3R1-mutant, HR+, HER2- PDX immunodeficient mice. Plans for a phase II trial in patients with PIK3R1-mutant, HR+, HER2- breast cancer are underway.[Table: see text]

Abstract PS18-30: Loss of NF1 leads to rho GTPase activation and sensitivity to multiple agents in breast cancer

Background: The Ras signaling pathway is a key oncogenic growth signaling pathway. The neurofibromatosis gene (NF1) is a tumor suppressor gene and negative regulator of Ras. Approximately 20% of breast cancers experience loss of active NF1 protein, leading to unabated Ras activity. Germline inactivation of NF1 leads to neurofibromatosis, which can be treated with MEK inhibitors. The functional consequences of NF1 loss have not been thoroughly explored in breast cancer. Therefore, we created a cellular model for the loss of NF1 in breast cells in order to identify novel therapies that would target NF1 null breast cells.

Methods: We used CRISPR CAS9 to knock out (KO) NF1 through targeted disruption of both NF1 alleles in the human non-tumorigenic breast cell line MCF-10A. Immunoblotting confirmed loss of the protein and this cell line was used to identify changes in cellular signaling that resulted from the loss of NF1. We then used a rational approach to select drugs that may target the cellular changes in NF1 null cells. Finally, the candidate drugs were tested in a tumor xenograft model in mice.

Results: Loss of NF1 endowed cells with a more transformed phenotype, including EGF growth independence and anchorage-independent growth. We observed increased activation of MAPK and activated Rho GTPase. The MEK inhibitors trametinib and PD0325901 (IC50=0.25 nM and 0.16 nM, respectively) inhibited growth of NF1-null, but not parent cells. We explored inhibitors of other proteins in the MAPK signaling pathway, including the Raf inhibitors sorafenib and vemurafenib and the dual MAP3K1/MAP2K4 inhibitor LY2228820. However, these compounds did not selectively inhibit growth of NF1-null cells, suggesting that Raf and MAP3K1/MAP2K4 are not vulnerable targets in NF1-null cells.

Vincristine and zoledronic acid can indirectly affect Rho GTPase function. NF1-null cells were more sensitive to both as single agents (IC50=1.1 nM and 6.9 μM, respectively) than parental cells. We also tested multiple combinations of these drugs and observed benefits from several combinations that exceeded single agent use. Similar sensitivity was not observed to docetaxel or ixabepilone.

We then tested the drugs as single agents and in combination against mouse tumor xenograft models with the human breast cancer cell lines Hs578T (NF1 null) or MCF-7 (wild type NF1). Treatment with single agent vincristine or zoledronic acid for 19 days resulted in statistically-significant decreases of 37.3% and 38.9%, respectively (p&lt;0.05) in Hs578T tumor xenografts. The combination treatment resulted in an enhanced reduction in tumor size of 48.8% with a higher level of significance (p&lt;0.01). Treatment of mice with MCF-7 bearing tumors with single agent vincristine resulted in a statistically significant decrease of 35.2% (p&lt;0.05); however, this effect was not observed using the combination treatment, as the change in growth compared to saline treatment was not statistically significant.

Conclusions: Our results suggest that loss of NF1 results in a transformed phenotype. Our results provide the first evidence that vincristine in combination with zoledronic acid may be efficacious in treating breast cancers. Additionally, we provide evidence that other drugs and drug combinations may be more effective at treating breast cancers with NF1 loss than MEK inhibitors, warranting further exploration.

Citation Format: Melody A. Cobleigh, Matthew Najor, Satnam Brar, Sanja Turturro, Liam Portt, Timothy Yung, Abde M Abukhdeir. Loss of NF1 leads to rho GTPase activation and sensitivity to multiple agents in 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 PS18-30.

Loss of STAT6 leads to anchorage-independent growth and trastuzumab resistance in HER2+ breast cancer cells

Approximately 20% of breast cancers are HER2-positive. Trastuzumab has improved patient outcomes significantly for these cancers. However, acquired resistance remains a major hurdle in the clinical management of these patients. Therefore, identifying molecular changes that cause trastuzumab resistance is worthwhile. STAT6 is a transcription factor that regulates a variety of genes involved in cell cycle regulation, growth inhibition, and apoptosis. STAT6 expression is lost in approximately 3% of breast cancers, but little work has been done in the context of trastuzumab resistance in breast cancer. In isogenic cell line pairs, we observed that trastuzumab-resistant cells expressed significantly lower levels of STAT6 compared to trastuzumab-sensitive cells. Therefore, in order to study the consequences of STAT6 loss in HER2+ breast cancer, we knocked out both alleles of the STAT6 gene using somatic cell gene targeting. Interestingly, loss of STAT6 resulted in anchorage-independent growth and changes in several genes involved in epithelial to mesenchymal transition. This study suggests that STAT6 may play a role in the pathophysiology of HER2+ human breast cancer.

STAT6 expression and trastuzumab resistance in HER2+ breast cancer

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Background: Approximately 20% of breast cancers are HER2-positive. Trastuzumab has improved patient outcomes significantly for these cancers. However, acquired resistance occurs in almost all patients with metastatic breast cancer. Therefore, identifying molecular changes that are associated with trastuzumab resistance is worthwhile. STAT6 is a transcription factor that regulates a variety of genes involved in cell cycle regulation, growth inhibition, and apoptosis. STAT6 expression is lost in approximately 3% of breast cancers, but little work has been done in the context of trastuzumab resistance in breast cancer. Methods: In isogenic cell line pairs, we observed that trastuzumab-resistant cells expressed significantly lower levels of STAT6 compared to trastuzumab-sensitive cells. Therefore, in order to study the consequences of STAT6 loss in HER2+ breast cancer, we knocked out both alleles of the STAT6 gene using somatic cell gene targeting. Results: We observed that loss of STAT6 resulted in resistance to trastuzumab treatment in HER2-over-expressing cells. Additionally, loss of STAT6 resulted in anchorage-independent growth and changed expression of several genes involved in epithelial to mesenchymal transition. Functional studies revealed that STAT6 loss caused a non-tumorigenic human breast cell line to form tumors in mice. Conclusions: Loss of STAT6 in breast cells results in enhanced growth properties and resistance to trastuzumab. This study suggests that STAT6 may play a role in the pathophysiology of HER2+ human breast cancer. Disclaimer: The work herein was completed while AMA was a faculty member at Rush University. AMA is currently an employee with the U.S. Food and Drug Administration. The views and data in this publication do not reflect the opinions of the U.S. Government or The U.S. Food and Drug Administration.

Primary results of NRG Oncology / NSABP B-43: Phase III trial comparing concurrent trastuzumab (T) and radiation therapy (RT) with RT alone for women with HER2-positive ductal carcinoma in situ (DCIS) after lumpectomy

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Background: Preclinical studies report that T can boost RT effectiveness. The primary aim of this trial assessed the efficacy of concurrent T + RT vs RT alone in preventing recurrence of ipsilateral breast cancer, ipsilateral skin cancer, or ipsilateral DCIS (IBTR) in women with DCIS. Methods: Eligibility: Women ≥18 yrs, ECOG performance status 0 or 1, DCIS resected by lumpectomy, and clear margins. Whole-breast RT after randomization was with 25+ fractions or accelerated with 16-17 fractions. RT boost was allowed. Centralized HER2 testing and ER and/or PR were required before entry. Stratification was by menopausal status, adjuvant endocrine therapy plan, and nuclear grade. T was given at 8 mg/kg IV within 1 wk before and 5 days after RT began (Dose 1) and at 6 mg/kg IV 3 wks after Dose 1 (Dose 2). Definitive intent-to-treat primary analysis was to be conducted when either 163 IBTR events were recorded or when all accrued pts were on study for ≥5 yrs. Results: 2014 pts were randomized (11/9/08 to 12/8/14);1998 (99.2%) had follow-up information. Median follow-up time on 12/31/19 was 79.2 mos. 2001 pts had RT information, 1965 (98.2%) completed RT: 988 (98.3%) in the RT arm and 977 (98.1%) in the RT+T arm. 996 pts had T compliance information in the RT+T arm, 939 (94.3%) completed two doses of T, 25 (2.5%) had one dose of T, and 32 (3.2%) did not receive T. At primary definitive analysis, 114 IBTR events occurred: 63 in the RT arm and 51 in the RT+T arm (HR = 0.81 [95% CI: 0.56-1.17], p-value = 0.26). 38 were invasive: 18 in the RT arm and 20 in the RT+T arm (HR = 1.11 [95% CI: 0.59-2.10], p-value = 0.74). 76 were DCIS: 45 in the RT arm and 31 in the RT+T arm (HR = 0.68 [95% CI: 0.43-1.08], p-value = 0.10). Annual IBTR event rates were 0.99%/yr in the RT group and 0.80%/yr in the RT+T group. There were 288 events of any kind [iDFS-DCIS] (DFS): 155 in the RT arm and 133 in the RT+T arm (HR = 0.84 [95% CI: 0.66-1.05], p-value = 0.13) and 48 deaths: 26 in the RT arm and 22 in the RT+T arm (OS HR = 0.85 [95% CI: 0.48-1.51], p = 0.59). The study did not reach the 163 protocol-specified events, so the definitive analysis was triggered by all pts having been on study for ≥5 years. Conclusions: The addition of T to RT did not achieve the protocol objective of 36% reduction in the IBTR rate but did achieve a modest, statistically non-significant reduction of 19%. Support: U10-180868, -180822, UG1-189867; Genentech. The authors thank Elaina Harper and Marlon Jones for data management. Clinical trial information: NCT00769379 .

Somatic loss of PIK3R1 may sensitize breast cancer to inhibitors of the MAPK pathway

PURPOSE

The PI3K pathway, which includes the PI3K catalytic subunits p110α (PIK3CA) and the PI3K regulatory subunit p85α (PIK3R1), is the most frequently altered pathway in cancer. We encountered a breast cancer patient whose tumor contained a somatic alteration in PIK3R1. Some commercial sequencing platforms suggest that somatic mutations in PIK3R1 may sensitize cancers to drugs that inhibit the mammalian target of rapamycin (mTOR). However, a review of the preclinical and clinical literature did not find evidence substantiating that hypothesis. The purpose of this study was to knock out PIK3R1 in order to determine the optimal therapeutic approach for breast cancers lacking p85α.

METHODS

We created an isogenic cellular system by knocking out both alleles of the PIK3R1 gene in the non-tumorigenic human breast cell line MCF-10A. Knockout cells were compared with wild-type cells by measuring growth, cellular signaling, and response to drugs.

RESULTS

We observed hyperphosphorylation of MEK in these knockouts, which sensitized PIK3R1-null cells to a MEK inhibitor, trametinib. However, they were not sensitized to the mTOR inhibitor, everolimus.

CONCLUSIONS

Our findings suggest that breast cancers with loss of p85α may not respond to mTOR inhibition, but may be sensitive to MEK inhibition.

Abemaciclib with or without fulvestrant for the treatment of hormone receptor-positive and HER2-negative metastatic breast cancer with disease progression following prior treatment with palbociclib

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Background: Abemaciclib is a selective inhibitor of CDK4 and CDK6 kinase activity. It is approved for patients with hormone receptor (HR) positive, human epidermal growth factor receptor 2 (HER2) negative, advanced or metastatic breast cancer (MBC) previously treated: in combination with fulvestrant for patients with disease progression following endocrine therapy (MONARCH 2) and as monotherapy for patients with disease progression after endocrine therapy and chemotherapy for MBC (MONARCH 1). The patients in these trials were CDK 4/6 inhibitor-naïve. It has not yet been studied in patients who previously received a CDK 4/6 inhibitor. Methods: We performed a chart review of patients with HR positive, HER2-negative MBC treated at Rush University Medical Center who progressed on palbociclib, either with an aromatase inhibitor (AI) or fulvestrant, and were subsequently treated with abemaciclib with or without fulvestrant. We documented patient demographics, prior treatment, and response to abemaciclib therapy. Results: 21 female patients, mean age 57.8 (+/- 13.2y), were included. Patients had received 1-5 prior lines of endocrine therapy and 0 – 4 prior lines of chemotherapy for MBC. All patients received prior palbociclib: 14 patients with an AI, 6 patients with fulvestrant, and 1 patient received palbociclib with an AI and then with fulvestrant. Of the 21 patients, 17 were treated with abemaciclib monotherapy and 4 received abemaciclib with fulvestrant. SD was seen in 19% of patients (4/21) and 62% had PD (13/21). The CBR was 29% (6/21) and all of these patients received abemaciclib monotherapy. Due to expected toxicities of the drug (diarrhea, neutropenia, and thrombocytopenia), 19% (4/21) of patients discontinued treatment. 4 patients continued abemaciclib monotherapy for greater than 8.3M. 3 patients were on treatment for less than 35 days; 2 stopped due to expected toxicities and one had progression of disease on physical exam. Median treatment duration was 3.1M. Conclusions: This retrospective chart review of 21 patients demonstrates that abemaciclib has limited activity as a single agent in patients previously treated with palbociclib.

Safety and Efficacy of Palbociclib and Radiation Therapy in Patients With Metastatic Breast Cancer: Initial Results of a Novel Combination

Purpose

Palbociclib is a selective cyclin-dependent kinase 4/6 inhibitor approved for metastatic ER+/HER2- breast cancer. Preclinical evidence suggests a possible synergistic effect of palbociclib when combined with radiation therapy (RT); however, the toxicity of this pairing is unknown. We report preliminary results on the use of this combination.

Methods and Materials

Records of patients treated with palbociclib at our institution from 2015 to 2018 were retrospectively reviewed. Patients who received RT for symptomatic metastases concurrently or within 14 days of palbociclib were included. Local treatment effect was assessed by clinical examination and subsequent computed tomography/magnetic resonance imaging. Toxicity was graded based on Common Terminology Criteria for Adverse Events version 5.0.

Results

A total of 16 women received palliative RT in close temporal proximity to palbociclib administration. Four patients received palbociclib before RT (25.0%), 5 concurrently (31.3%), and 7 after RT (43.8%). The median interval from closest palbociclib use to RT was 5 days (range, 0-14). The following sites were irradiated in decreasing order of frequency: bone (11 axial skeleton [9 vertebra and 2 other]; 4 pelvis; 3 extremity), brain (4: 3 whole brain RT and 1 stereotactic radiosurgery), and mediastinum (1). The median and mean follow-up time is 14.7 and 17.6 months (range, 1.7-38.2). Pain relief was achieved in all patients. No radiographic local failure was noted in the 13 patients with evaluable follow-up imaging. Leukopenia, neutropenia, and thrombocytopenia were seen in 4 (25.0%), 5 (31.3%), and 1 (6.3%) patient before RT. After RT, 5 (31.3%), 1 (6.3%), and 3 (18.8%) patients were leukopenic, neutropenic, and thrombocytopenic, respectively. All but 2 (grade 2) hematologic toxicities were grade 1. No acute or late grade 2+ cutaneous, neurologic, or gastrointestinal toxicities were noted. Toxicity results did not differ based on disease site, palbociclib-RT temporal association, or irradiated site.

Conclusions

The use of RT in patients receiving palbociclib resulted in minimal grade 2 and no grade 3+ toxicities. This preliminary work suggests that symptomatic patients receiving palbociclib may be safely irradiated.

Abstract P2-09-30: A gene expression signature that predicts for trastuzumab response in HER2+ breast cancer

Background: Approximately 15-20% of breast cancers overexpress HER2. These patients are eligible for trastuzumab in combination with chemotherapy. However, some patients are extreme responders to single agent trastuzumab and we wanted to identify differences in cancer gene expression that could predict response to single agent trastuzumab.

Methods: We performed paired-end RNAseq on an isogenic cellular model of trastuzumab sensitivity and resistance. We reasoned that the isogenic nature of the cellular clones used in this study would enrich for differentially-expressed genes (DEGs) that were associated with response to single-agent trastuzumab. DEGs where chosen based upon either i) large fold changes in resistant vs. sensitive clones, ii) high frequency in human HER2+ breast cancers, or iii) were found to be enriched with other DEGs in signaling pathways selected by Ingenuity Pathway Analysis (IPA). DEGs were further scrutinized based upon associations with overall survival (OS) in HER2+ human breast cancers. The resulting genes were validated using qPCR and in several independent sample sets containing gene expression profiles of human breast cancers.

Results: Discovery: RNAseq yielded 3,241 statistically-significant DEGs. We used two independent filtering pipelines to obtain 175 DEGs. Ingenuity Pathway Analysis found signaling pathways associated with eukaryotic initiation factor, lysine specific demethylase 5B, and estrogen receptor alpha to be enriched in DEGs associated with trastuzumab resistance. Of these DEGs, six genes correlated with a statistically significant change in OS in the training dataset, and were validated by qPCR in the cell lines used for the analysis. We further determined that the six-gene signature was a negative predictor of overall survival in HER2+ breast cancer patients whose cancers carried at least one DEG. Validation: Using independent cohorts from TCGA and the website KMplot.com, we validated the predictive power of the six-gene signature. Of the 47 HER2+ patients from TCGA, eight patients carried two more DEGs, while 39 carried ≤ 1 DEG. Although the numbers are small, of the 8 patients followed for four or more years, only one patient was alive as compared with 7 out of 39 patients without the signature. Similarly, Kaplan Meier analysis of gene expression data from KMplot.com revealed that only 1 out of 23 patients (4.3%) who carried high mean expression of the six-gene signature were free of distant metastases after 87 months, compared to 4 out of 43 patients (9.3%) from the cohort carrying low mean expression of the six-gene signature. In both validation cohorts, the six DEG signature was not predictive in HER2-negative breast cancers.

Discussion: Patients whose tumors lack this gene expression signature are more likely to experience a favorable response to trastuzumab therapy. This signature requires validation in a clinical cohort treated with trastuzumab monotherapy.

Citation Format: Abukhdeir AM, Najor MS, Turturro SB, Armstrong AR, McDonald A, Fogg L, Cobleigh MA. A gene expression signature that predicts for trastuzumab response in HER2+ breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-30.

Hereditary diffuse gastric cancer and lynch syndromes in a BRCA1/2 negative breast cancer patient

INTRODUCTION

Genetic counseling and testing is recommended for women with a personal and/or family history of breast and other cancers (ovarian, pancreatic, male breast and others). Mutations in the BRCA1 and BRCA2 genes (BRCA1/2) are the most common causes of hereditary breast and ovarian cancer. Additional genetic counseling and testing with a multi-gene panel may be considered in breast cancer patients who tested negative for mutations in these two genes. In about 11% of BRCA1/2-negative patients, further genetic testing reveals pathogenic mutations in other high or moderate cancer risk genes. In 0.2% of cases, an individual may carry pathogenic mutations in more than one high penetrance gene (a double heterozygote). Finding one or more pathogenic mutations is important for cancer prevention in patients and/or their families.

CASE PRESENTATION

Here we present a case of a breast cancer patient who did not have a pathogenic mutation in BRCA1/2 and had a family history of breast and stomach cancers. On an additional multi-gene panel testing, she was found to carry pathogenic mutations in the CDH1 and PMS2 genes, which cause Hereditary Diffuse Gastric Cancer and Lynch syndromes, respectively. To our knowledge, this is the first description of such a double heterozygote.

DISCUSSION

Clinical manifestations, genetics, and management of both syndromes are reviewed, including prophylactic surgery and screening for unaffected family members. Management challenges for a mutation carrier with advanced breast cancer are discussed. Our case supports the clinical utility of additional multi-gene panel testing for breast cancer patients who do not have a pathogenic mutation in BRCA1/2 genes.

Experience and impact of alopecia in patients (pts) with HER2+ metastatic breast cancer (MBC) in the SystHERs registry

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Background: Although alopecia is common with systemic chemotherapy, its psychological impact is often overlooked in treatment (tx) decisions. We sought to better understand the impact of alopecia using data from SystHERs, an observational registry of pts with HER2+ MBC. Methods: SystHERs enrolled pts ≥ 18 years within 6 mos of an MBC diagnosis. Pt-reported outcomes are assessed quarterly. The Alopecia Patient Assessment (APA, Genentech) is a validated instrument measuring the incidence of hair loss in the prior 3 mos and the impact of hair loss in the prior 7 days. The APA includes 5 items scored on a 5-point scale (total range: 1–25). Higher scores indicate greater impact. Pts completed the APA within 30–90 days of initial MBC tx. Subgroups with no hair loss, hair loss without impact, or impactful hair loss were compared descriptively. Results: As of June 3, 2016, 591 of 976 pts were eligible for this analysis. Of these, 175 (30%) reported no hair loss, 123 (21%) reported hair loss without impact, and 293 (50%) reported impactful hair loss within 30–90 days of initial MBC tx. Respectively, 23% (41/175), 82% (101/123), and 79% (231/293) were on active chemotherapy, most commonly docetaxel (39% [16/41], 66% [67/101], and 62% [144/231]) and paclitaxel (5% [2/41], 27% [27/101], and 23% [54/231]). Median time from initial chemotherapy tx to APA was 55, 70, and 64 days. Of all pts with no hair loss, 39% had de novo MBC vs 56% of pts with hair loss but no impact and 55% with impactful hair loss. Relative to the no-hair-loss and hair-loss-but-no-impact subgroups, the subgroup with impactful hair loss was younger (median 57 and 59 vs 54 years, respectively) and had more pts with ≥ 2 metastatic sites (51% and 54% vs 63%) and visceral metastases (59% and 63% vs 69%). The median total APA score for pts with impactful hair loss was 8.8 (IQR 7.0–12.5). Conclusions: Of pts reporting hair loss, 79–82% were receiving systemic chemotherapy. Pts with impactful hair loss may have had greater disease burden. Alopecia impacted self-image and embarrassment more than work or social functioning. Clinical trial information: NCT01615068. [Table: see text]

Abstract P6-11-17: Mutations in PIK3R1 activate multiple pathways in breast cancer

It has been estimated that by the end of this year, 270,000 American women will be newly diagnosed with breast cancer, while 40,000 women that already have breast cancer will succumb to the disease. Considerable attention has been given to the PI3K signaling cascade following the discovery that PIK3CA is the most frequently mutated oncogene in breast cancer.However, few studies have explored the function of PIK3R1, which is the regulatory domain of the PI3K complex, despite being mutated in ~3% of all breast cancers.

Several studies have demonstrated that expression of PIK3R1 is downregulated in human cancers. Decreased expression of the PIK3R1 protein leads to tumor formation, suggesting its role as a tumor suppressor gene and a potential prognostic marker in breast cancer. However, PIK3R1 is a gene with little pre-clinical evidence to recommend experimental therapies. Despite this lack of evidence, commercial services that perform molecular analyses of tumors suggest the use of an mTOR inhibitor for patients whose breast cancers carry mutant PIK3R1.

In order to determine if mTOR inhibitors were indeed effective in mutant PIK3R1 tumors, we created and characterized a model for mutant PIK3R1 in the non-tumorigenic, human breast epithelial cell line, MCF-10A. Surprisingly, we observed that mTOR inhibitors were ineffective in these cells. However, in searching for other classes of small molecule inhibitors that were effective, we observed that mutations in PIK3R1 sensitized cells to MAPK inhibitors.

Herein, we present the first evidence for the use of targeted therapies in breast cancers carrying mutant PIK3R1. We provide evidence against the use of mTOR inhibitors and provide a rationale for the use of MAPK inhibitors.

Citation Format: Abukhdeir AM, Turturro SB, Najor MS, Brar SS, Cobleigh MA. Mutations in PIK3R1 activate multiple pathways in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-11-17.

Mutations in PIK3CA sensitize breast cancer cells to physiologic levels of aspirin

A review of the literature finds that women diagnosed with breast cancer, who were on an aspirin regimen, experienced a decreased risk of distant metastases and death. Several recent studies have reported an improvement in overall survival in colorectal cancer patients who harbored mutations in the oncogene PIK3CA and received a daily aspirin regimen. Breast cancer patients on a daily aspirin regimen experienced decreased risk of distant metastases and death. PIK3CA is the most frequently mutated oncogene in breast cancer, occurring in up to 45 % of all breast cancers. In order to determine if mutations in PIK3CA sensitized breast cancers to aspirin treatment, we employed the use of isogenic cellular clones of the non-tumorigenic, breast epithelial cell line MCF-10A that harbored mutations in either PIK3CA or KRAS or both. We report that mutations in both PIK3CA and KRAS are required for the greatest aspirin sensitivity in breast cancer, and that the GSK3β protein was hyperphosphorylated in aspirin-treated double knockin cells, but not in other clones/treatments. A more modest effect was observed with single mutant PIK3CA, but not KRAS alone. These observations were further confirmed in a panel of breast cancer cell lines. Our findings provide the first evidence that mutations in PIK3CA sensitize breast cancer cells to aspirin.

Patient-reported outcomes (PROs) from the systemic therapies for HER2-positive metastatic breast cancer (MBC) registry study (SystHERs): Eliciting the patient experience

286

Background: Patients with HER2-positive MBC are, on average, living longer. Data are limited on patient-reported quality of life (QoL) and economic burden during these extended survival periods. In accordance with guidelines for comparative effectiveness research in oncology (Basch et al, 2012), SystHERs, initiated in 2012, includes PROs to capture the patient experience. Here we report baseline (at enrollment) PRO results from SystHERs. Methods: SystHERs is a US-based prospective observational cohort study that aims to enroll 1000 patients with HER2-positive MBC within 6 months of metastatic diagnosis. Patients will be followed for 5–8 years.PROs, including QoL, economic burden, and symptoms related to neuropathy, alopecia, and cognition, are collected at baseline and ~90-day intervals during clinic visits, including after disease progression. Results: As of Feb 17, 2014, 319 patients were enrolled, and baseline data from 306 eligible patients are reported. Median time to enrollment since MBC diagnosis was 2.4 months. At least 1 PRO item was completed by 90% of eligible patients. Scale reference ranges (higher scores indicate better status) and median scores at baseline were: overall HRQoL (0–100)=80.0; FACT-B Trial Outcome Index (0–96)=58.0, and the Rotterdam Activities of Daily Living Scale (0–100)=85.7. One hundred patients (40.3%) were employed. These patients reported on average 36% work time missed (absenteeism) and 30% decreased on-the-job effectiveness (presenteeism) due to MBC. Patients reported a median out-of-pocket MBC-related expenditure of $735 in the past 3 months (range $0–11,700). Of this, the median deductible and copay-related cost was $350. Conclusions: To our knowledge, this is the only HER2-positive MBC patient registry that includes comprehensive PROs to supplement clinical data. To date, participation in PROs is high at baseline (90%).QoL and economic burden were consistent with other studies (Cortés et al, 2013; Zafar et al, 2013). Baseline results for ~500 patients are expected by the time of the congress presentation and will include data on symptoms related to neuropathy, alopecia, and cognition. Clinical trial information: NCT01615068.

Abstract OT2-3-02: NSABP B-43: A phase III clinical trial to compare trastuzumab (T) given concurrently with radiation therapy (RT) to RT alone for women with HER2+ DCIS resected by lumpectomy (Lx)

Background: A significant amount of DCIS is ER negative and/or overexpresses HER2. This provides an opportunity to test targeted therapy in DCIS. In xenograft models and cell lines, T boosts RT effectiveness. In T-treated HER2+ patients, apoptosis occurs within 1 wk of single agent T use, with T found in ductal aspirates. Ample safety evidence for T exists. T given during whole breast irradiation (WBI) may improve results for lumpectomy (Lx) resected HER2+ DCIS. A trial to examine this question will enhance the understanding of breast tumor biology and the prevention of such tumors and could possibly extend breast-conserving surgery benefits for women with DCIS.

Method: After Lx for pure DCIS, each patient's DCIS lesion is centrally tested for HER2 by IHC analysis. HER2 2+ tumors undergo FISH analysis. HER2 3+ or FISH+ patients can be randomly assigned to 2 doses of T, 3 weeks apart during WBI or to WBI alone.

Women ≥18 yrs. with a margin-clear Lx for pure DCIS, with ECOG status 0/1 who are clinically or pathologically node negative are eligible. Centrally tested DCIS must be HER2 +. ER and/or PR status must be known before randomization.

Primary aims are to determine if T decreases ipsilateral breast cancer recurrence, ipsilateral skin cancer recurrence, or ipsilateral DCIS. Secondary aims are to determine the benefit of T in preventing regional or distant recurrence and contralateral invasive breast cancer or DCIS. NSABP B-43 will determine if DFS, recurrence-free interval, and OS can be improved with the use of T. 2000 patients will be accrued over 7.9 yrs, with a definitive analysis of primary endpoints performed at 163 ipsilateral breast cancer events (7.5 - 8 yrs. after protocol initiation) with an 80% power to detect a hazard reduction of 36%, from 1.73 ipsilateral breast cancer events per 100 pt-yrs to 1.11 events per 100 pt-yrs. The 36% observed reduction in the hazard of IIBCR-SCR-DCIS on the T arm is based on a projection of 40% hazard reduction if the compliance were perfect, with a 10% noncompliance rate. As of 5-31-13, 1,349 patients have been randomized.

NCT00769379

Support: PHS NCI-U10-CA-69651, -12027; NCI P30-CA-14599; Genentech, Inc.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT2-3-02.

Progression-free survival (PFS) as surrogate endpoint for overall survival (OS) in clinical trials of HER2-targeted agents in HER2-positive metastatic breast cancer (MBC): An individual patient data (IPD) analysis

610

Background: The gold standard endpoint in randomized clinical trials (RCTs) in MBC is OS, which has the disadvantage of requiring extended follow-up and being confounded by subsequent anti-cancer therapies. Although therapeutics have been approved based on PFS, its use as a primary endpoint is controversial. This study, the first IPD meta-analysis of targeted agents in MBC, aimed to collect data from RCTs of HER2-targeted agents in HER2+ MBC, assessing to what extent PFS correlates with, and may be used as, a surrogate for OS. Methods: A search was conducted in April 2011. Eligible RCTs accrued HER2+ MBC patients (pts) in 1992-2008. Collaboration was obtained from industrial partners (Roche, GSK) for industry-led studies. Investigator-assessed PFS was defined as the time from randomization to clinical or radiological progression, or death. A correlation approach was used: at the individual level, to estimate the association between PFS and OS using a bivariate survival model and at the trial level, to estimate the association between treatment effects on PFS and OS. Squared correlation values close to 1.0 would indicate strong surrogacy. Results: The search strategy resulted in 2137 eligible pts in 13 RCTs testing trastuzumab or lapatinib. We collected IPD data from 1963 pts in 9 RCTs. One phase II RCT did not have sufficient follow-up data so that 1839 pts in 8 RCTs were retained (5 evaluating trastuzumab, 3 lapatinib); 6 out of 8 RCTs were first-line. At the individual level, the Spearman rank correlation using Hougaard copula was equal to r=0.66 (95% CI 0.65 to 0.66) corresponding to an r2 of 0.42. At the trial level, the squared correlation between treatment effects on PFS and OS was provided by R2=0.33 (95% CI -0.22 to 0.86) using Hougaard copula and R2=0.53 (95% CI 0.22 to 0.83) using log hazard ratios from Cox models. Conclusions: In RCTs of HER2-targeted agents in HER2+ MBC, PFS is moderately correlated with OS and treatment effects on PFS are modestly correlated with treatment effects on OS, similarly to first-line chemotherapy in MBC (Burzykowski et al JCO 2008). PFS does not completely substitute for OS.

NSABP B-43: A phase III clinical trial to compare trastuzumab (T) given concurrently with radiation therapy (RT) to RT alone for women with HER2+ DCIS resected by lumpectomy (Lx)

TPS666

Background: A significant amount of DCIS is ER-negative and/or overexpresses HER2. This study will test HER2-targeted therapy in DCIS. Among T-treated HER2+ patients (pts) with DCIS treated with a single dose of T, T is found in ductal aspirates and antibody-dependent cell-mediated cytotoxicity activity for HER2 is increased. T boosts the effectiveness of RT in breast cancer xenograft models and cell lines. T given during whole breast irradiation (WBI) may improve results for HER2+ DCIS treated with lumpectomy (Lx). A trial to examine this question will enhance the understanding of breast tumor biology, the prevention of such tumors, and could possibly extend breast-conserving surgery benefits for women with DCIS. Methods: After Lx for pure DCIS, each pt’s DCIS lesion is centrally tested for HER2 using ASCO/CAP guidelines. HER2+ pts are randomly assigned to receive 2 doses of T, 3 weeks apart during WBI or to WBI alone. Women ≥18 yrs with a margin-clear Lx for pure DCIS, with ECOG status 0/1 who are clinically or pathologically node negative are eligible. ER and/or PR status must be known before random assignment. Primary aims are to determine if T decreases ipsilateral breast cancer (IBC) recurrence, ipsilateral skin cancer recurrence, or ipsilateral DCIS. Secondary aims are to determine the benefit of T in preventing regional or distant recurrence and contralateral invasive breast cancer or DCIS. B-43 will determine if DFS, recurrence-free interval, and/or overall survival can be improved with the use of T. 2000 pts will be accrued over 7.9 yrs, with a definitive analysis of primary endpoints performed at163 IBC events (7.5 - 8 yrs after protocol initiation) with an 80% power to detect a hazard reduction of 36%, from 1.73 IBC events per 100 pt-yrs to 1.11 events per 100 pt-yrs. The 36% observed reduction in the hazard of IIBCR-SCR-DCIS on the T arm is based on a projection of 40% hazard reduction if the compliance were perfect, with a 10% noncompliance rate. As of 1-1-13, 1,127 pts have been randomized into the study. Support: PHS NCI-U10-CA-69651, -12027, and -P30-CA-14599 from the US NCI, and Genentech, Inc. Clinical trial information: NCT00769379.

Prognostic and predictive value of tumor vascular endothelial growth factor gene amplification in metastatic breast cancer treated with paclitaxel with and without bevacizumab; results from ECOG 2100 trial

PURPOSE

Clinically validated biomarkers for anti-angiogenesis agents are not available. We have previously reported associations between candidate VEGFA single-nucleotide polymorphisms (SNP) and overall survival (OS) in E2100. The associations between tumor VEGFA amplification and outcome are evaluated here.

EXPERIMENTAL DESIGN

E2100 was a phase III trial comparing paclitaxel with or without bevacizumab for patients with metastatic breast cancer. FISH to assess gene amplification status for VEGFA was conducted on paraffin-embedded tumors from 363 patients in E2100. Evaluation for association between amplification status and outcomes was conducted.

RESULTS

Estrogen receptor (ER)+ or progesterone receptor (PR)+ tumors were less likely to have VEGFA amplification than ER/PR- tumors (P = 0.020). VEGFA amplification was associated with worse OS (20.2 vs. 25.3 months; P = 0.013) in univariate analysis with a trend for worse OS in multivariate analysis (P = 0.08). There was a significant interaction between VEGFA amplification, hormone receptor status, and study arm. Patients with VEGFA amplification and triple-negative breast cancers (TNBC) or HER2 amplification had inferior OS (P = 0.047); amplification did not affect OS for those who were ER+ or PR+ and HER2-. Those who received bevacizumab with VEGFA amplification had inferior progression-free survival (PFS; P = 0.010) and OS (P = 0.042); no association was seen in the control arm. Test for interaction between study arm and VEGFA amplification with OS was not significant.

CONCLUSION

VEGFA amplification in univariate analysis was associated with poor outcomes; this was particularly prominent in HER2+ or TNBCs. Additional studies are necessary to confirm the trend for poor OS seen on multivariate analysis for patients treated with bevacizumab.

Adjuvant endocrine therapy for breast cancer

Endocrine therapy is a critical part of adjuvant therapy in women with hormone receptor-positive breast cancer, and has been shown to reduce the risk of recurrence and death from breast cancer. For decades, 5 years of tamoxifen has been the standard treatment. For premenopausal women, it remains so, and we await the results of ongoing trials to define the role of ovarian suppression or ablation with endocrine therapy. If a woman becomes postmenopausal during treatment, consideration should be given to extended adjuvant therapy with an aromatase inhibitor (AI) for another 5 years. In postmenopausal women, trials have shown that AIs are more beneficial than tamoxifen in preventing disease recurrence.They have been compared as upfront treatment for 5 years, as sequential therapy after 2 to 3 years of tamoxifen, and as extended treatment for 5 years after 5 years of tamoxifen. Among the questions still being studied are the optimal duration of extended adjuvant therapy with AIs, how one AI performs compared to another, and whether there is a benefit to intermittent extended adjuvant treatment.

A phase III clinical trial to compare trastuzumab (T) given concurrently with radiation therapy (RT) to RT alone for women with HER2+ DCIS resected by lumpectomy (Lx): NSABP B-43

TPS657

Background: Asignificant amount of DCIS is ER negative and/or overexpresses HER2. This provides an opportunity to test molecular therapy in DCIS. In xenograft models and cell lines, T boosts RT effectiveness. In T-treated HER2+ patients, apoptosis occurs within 1 wk of single agent T use, with T found in ductal aspirates. Ample safety evidence for T exists. T given during whole breast irradiation (WBI) may improve results for Lx-resected HER2+ DCIS. A trial to examine this question will enhance the understanding of breast tumor biology and the prevention of such tumors and could possibly extend breast-conserving surgery benefits for women with DCIS. Methods: After Lx for pure DCIS, each patient’s DCIS lesion is centrally tested for HER2 by IHC analysis. HER2 2+ tumors undergo FISH analysis. HER2 3+ or FISH+ patients can be randomly assigned to 2 doses of T, 3 weeks apart during WBI or to WBI alone. Women ≥18 yrs. with a margin-clear Lx for pure DCIS, with ECOG status 0/1 who are and clinically or pathologically node negative are eligible. Centrally tested DCIS must be HER2 +. ER and/or PR status must be known before randomization. Primary aims are to determine if T decreases ipsilateral breast cancer recurrence, ipsilateral skin cancer recurrence, or ipsilateral DCIS. Secondary aims are to determine the benefit of T in preventing regional or distant recurrence and contralateral invasive breast cancer or DCIS. B-43 will determine if DFS, recurrence-free interval, and OS can be improved with the use of T. 2000 patients will be accrued over 7.9 yrs, with a definitive analysis of primary endpoints performed at163 ipsilateral breast cancer events (7.5 - 8 yrs. after protocol initiation) with an 80% power to detect a hazard reduction of 36%, from 1.73 ipsilateral breast cancer events per 100 pt-yrs to 1.11 events per 100 pt-yrs. The 36% observed reduction in the hazard of IIBCR-SCR-DCIS on the T arm is based on a projection of 40% hazard reduction if the compliance were perfect, with a 10% noncompliance rate. As of 12-31-11, 763 patients have been randomized. NCT00769379 Grant support: PHS NCI-U10-CA-69651, -12027, and NCI P30-CA-14599 from the US NCI and Genentech, Inc.

Synchronous bilateral breast cancer (SBBC): Concordance of receptor status between right and left breast

572

Background: This analysis was prompted by a patient who presented with SBBC who had and ER+, HER2- cancer in one breast and an ER-, HER2+ cancer in the other. Since both breasts have the same genetic background and environmental exposures, concordance should be virtually identical unless other factors are at play. Methods: SBBC was defined as bilateral cancer diagnosed concurrently or within 6 months of each other. Cases were identified retrospectively from patients seen at Rush University Medical Center. This analysis was limited to invasive SBCC (ISBBC). Estrogen receptor (ER) and Her2/neu (HER2) status were assessed according current ASCO/CAP guidelines. Correlation between ER and HER2 status was determined using κ statistic. Results: From January 1998 to December 2012, 33 cases of ISBBC were diagnosed. In 65% of cases synchronous disease was diagnosed concurrently. The average age at diagnosis was 56. The majority were multiparous and 79% post menopausal. About half of the patients (55%) had at least one first degree relative with a history of breast or ovarian cancer and 9% of the cohort had a deleterious mutation in BRCA1 or BRCA2. Infiltrating ductal was most common (74%) followed by infiltrating lobular (21%). 53% of breasts specimens also contained ductal carcinoma in situ. 68% of tumors were ER positive and 8% were HER2 positive. Concordance in ER status was seen in 73% of cases (kappa coefficient 0.14) and in HER2 status was 64% (Kappa coefficient 0.35). Conclusions: Despite identical hereditary and environmental exposure, some patients develop ISBBC cancers with discordant receptor status. While this is the exception, it suggests that other factors influence important tumor characteristics. [Table: see text]

OT1-02-05: A Phase III Clinical Trial Comparing Trastuzumab Given Concurrently with Radiation Therapy to Radiation Therapy (RT) Alone for Women with HER2−Positive DCIS Resected by Lumpectomy: NSABP B-43

Background

Because a substantial portion of DCIS is ER negative and overexpresses HER2, therapy targeting this protein is a promising strategy for HER2−overexpressing DCIS.

Preclinical studies have shown that trastuzumab (T) boosts the effectiveness of RT in xenograft models and in cell lines with no detrimental effect on irradiated HER2−normal cells. Studies correlating clinical response with molecular markers in T-treated patients show that apoptosis occurs within 1 wk of starting singleagent T, with little effect on proliferation. Shorter duration treatments with this agent require investigation. Adjuvant trials using T during breast irradiation have already provided ample safety evidence. Will T administered during WBI improve lumpectomy + WBI results in women with HER2−positive DCIS? This trial will allow us to better understand the biology of breast cancer and its prevention and will extend the benefits of breast-conserving surgery for women with DCIS.

Trial Design: Post lumpectomy for DCIS without evidence of an invasive component, a central review of each patient's pure DCIS lesion is carried out for HER2 by IHC analysis. If the HER2 is 2+, FISH analysis is done, and patients whose tumors are HER2 3+ or FISH positive can be randomly assigned to receive 2 doses of T 3 wk apart during WBI or to receive WBI alone.

Eligibility criteria: Women 18 years or older with an ECOG status of 0 or 1 who have undergone a margin-clear lumpectomy for DCIS and whose tumors are clinically or pathologically node negative are eligible. DCIS must be HER2 positive by central testing. ER and/or PR status must be known before random assignment.

Specific aims: The primary aim is to determine if T given concurrently with WBI is more beneficial in preventing IBC recurrence, ipsilateral skin cancer recurrence, or ipsilateral DCIS compared with WBI alone for HER2−positive DCIS resected by lumpectomy. Secondary aims are to compare the possible benefit of T given during WBI to that of WBI alone in preventing regional or distant recurrence and contralateral invasive or DCIS breast cancer. B-43 will determine if invasive or DCIS DFS, recurrence-free interval, and OS can be improved with the addition of T to WBI. The effects of T on ovarian function in premenopausal women will also be assessed.

Statistical methods and accrual: Our design calls for accrual of 2000 patients during a 7.9-year period. As of May 31, 2011, 578 patients have been entered. A definitive analysis of primary endpoints will be performed when 163 ipsilateral breast cancer events occur (7.5 and 8 years after protocol initiation). This number of events affords 80% power to detect a hazard reduction of 36%, from 1.73 ipsilateral breast cancer events per 100 patient-years to 1.11 events per 100 patient-years. The 36% observed reduction in the hazard of IIBCR-SCR-DCIS on the T arm is based on a projection of 40% hazard reduction if the compliance were perfect, with a 10% noncompliance rate.

Supported by PHS grants NCI-U10-CA-69651, NCI-U10-CA-12027, and NCI P30-CA-14599 from the US NCI and Genentech, Inc.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT1-02-05.

Other options in the treatment of advanced breast cancer

Many cytotoxic therapies are available for patients with metastatic breast cancer, but response rates are low and acquired or de novo resistance is virtually universal. Among the agents that are used in the treatment of pretreated metastatic breast cancer are vinorelbine, gemcitabine, nab-paclitaxel, pemetrexed, platinum salts (eg, cisplatin, carboplatin), pegylated liposomal doxorubicin, etoposide, and irinotecan. Therapies that improve overall survival in patients with anthracycline- and taxane-resistant metastatic breast cancer are needed.

Impact of exploratory biomarkers on the treatment effect of bevacizumab in metastatic breast cancer

PURPOSE

The addition of bevacizumab to cytotoxic chemotherapy has demonstrated a progression-free survival (PFS) benefit in the first-line and second-line treatment of advanced or metastatic breast cancer (MBC). However, the addition of bevacizumab to capecitabine in heavily pretreated MBC patients did not show a PFS benefit (AVF2119g phase III trial). The aim of this study was to evaluate the expression of novel putative biomarkers as predictors of benefit from bevacizumab in retrospective subset analyses of the AVF2119g trial.

EXPERIMENTAL DESIGN

In the AVF2119g trial, 462 patients with MBC were randomly assigned to receive capecitabine or capecitabine plus bevacizumab. Primary tumor tissue and outcome data were available for 223 patients. Biomarker expression was assessed by in situ hybridization (VEGF-A, VEGF-B, thrombospondin-2 and Flt4) or immunohistochemistry (VEGF-C, PDGF-C, neuropilin-1, delta-like ligand (Dll) 4, Bv8, p53 and thymidine phosphorylase) on formalin-fixed, paraffin-embedded tissue. PFS was associated with these variables in retrospective subset analyses.

RESULTS

Patients with low scores for Dll4, VEGF-C, and neuropilin-1 showed trends toward improvement in PFS associated with the addition of bevacizumab to capecitabine (P values = 0.01, 0.05, and 0.07, respectively). These observations were not statistically significant following correction for multiple hypothesis testing.

CONCLUSION

These retrospective subset analyses suggest that expression of Dll4, VEGF-C, and neuropilin-1 may predict benefit from bevacizumab. Such observations are not conclusive but warrant additional testing.

Phase III double-blind, placebo-controlled, prospective randomized trial of adjuvant tamoxifen vs. tamoxifen and fenretinide in postmenopausal women with positive receptors (EB193): an intergroup trial coordinated by the Eastern Cooperative Oncology Group

Fenretinide and tamoxifen have additive antitumor effects preclinically. We performed a randomized, placebo-controlled, double-blind adjuvant trial in breast cancer patients treated for 5 years with tamoxifen, with or without fenretinide. Between October 1995 and October 1999, 426 postmenopausal women with hormone receptor-positive breast cancer were randomized. Patients were monitored for efficacy and toxicity. Four hundred and nineteen patients were evaluable. The study was terminated early due to slow accrual. There were no significant differences between treatment groups in DFS, TTR or survival. More patients stopped treatment early on the fenretinide arm than on placebo (P = 0.02). Grade 3/4 toxicities, including visual problems and musculoskeletal complaints were more common in patients receiving fenretinide (P = 0.007). A Night Blindness Questionnaire was used to monitor nyctalopia, which was slightly, but not significantly, more common on fenretinide. In this underpowered study, no significant difference was observed in efficacy between treatment groups. This trial provides important toxicity information about fenretinide, a retinoid that has been used in the prevention setting, because it is the only placebo-controlled, double-blind randomized study ever performed.

ACR appropriateness criteria on postmastectomy radiotherapy expert panel on radiation oncology-breast

This summary focuses on the role of postoperative radiation therapy in patients treated with modified radical mastectomy for invasive breast cancer, particularly in patients receiving systemic therapy.

Phase II Study of Sunitinib Malate, an Oral Multitargeted Tyrosine Kinase Inhibitor, in Patients With Metastatic Breast Cancer Previously Treated With an Anthracycline and a Taxane

Purpose

Sunitinib is an oral, multitargeted tyrosine kinase inhibitor that inhibits vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor, stem cell factor receptor (KIT), and colony-stimulating factor-1 receptor. This phase II, open-label, multicenter study evaluated sunitinib monotherapy in patients with metastatic breast cancer (MBC).

Patients and Methods

Sixty-four patients previously treated with an anthracycline and a taxane received sunitinib 50 mg/d in 6-week cycles (4 weeks on, then 2 weeks off treatment). The primary end point was objective response rate. Plasma samples were obtained for pharmacokinetic and biomarker analysis.

Results

Seven patients achieved a partial response (median duration, 19 weeks), giving an overall response rate of 11%. Three additional patients (5%) maintained stable disease for ≥ 6 months. Median time to progression and overall survival were 10 and 38 weeks, respectively. Notably, responses occurred in triple negative tumors and HER2-positive, trastuzumab-treated patients. Thirty-three patients (52%) required dose interruption during ≥ 1 cycle, and 25 patients required dose reduction (39%). Thirty-six patients (56%) had dose modifications due to adverse events (AEs). Treatment was associated with increases in plasma VEGF and decreases in soluble VEGFRs and KIT. The most common AEs were fatigue, nausea, diarrhea, mucosal inflammation, and anorexia. Most AEs were mild to moderate (grade 1 to 2) in severity and were effectively managed with dose delays or reductions.

Conclusion

Sunitinib is active in patients with heavily pretreated MBC. Most AEs were of mild-to-moderate severity and manageable with supportive treatment and/or dose modification. Further studies in breast cancer are warranted.

Targeting metastatic and advanced breast cancer

OBJECTIVES

To review the chemotherapy and targeted biologic options for treatment of advanced and metastatic breast cancer.

DATA SOURCES

Clinical and research articles and textbook chapters.

CONCLUSION

Recent clinical research has led to the use of novel targeted therapies in the management of locally advanced and metastatic breast cancer. Although metastatic breast cancer remains incurable, increases in disease-free and overall survival has been achieved.

IMPLICATIONS FOR NURSING PRACTICE

Recent advances in the biological targeted therapies against Her2/neu, VEGF, and EGFR are now either approved therapies or are in the final stages of clinical testing. Oncology nurses can help decrease toxicities and maintain better QOL by fully understanding the mechanism of action of the drugs, expected side effects, and anticipated response to the novel regimen.

Are Tri-Ethnic Low-Income Women with Breast Cancer Effective Teachers of the Importance of Breast Cancer Screening to Their First-Degree Relatives? Results from a Randomized Clinical Trial

The purpose of this study was to determine the efficacy of women with breast cancer as teachers of the importance of breast cancer screening to their first-degree female relatives. The sample was restricted to low-income working age women recruited from four hospitals. The study design was a randomized clinical trial. At each hospital, breast cancer patients (probands) were randomized into one of two study groups: (i) intensive, individual educational training on breast cancer screening or (ii) standard clinic education on breast cancer screening. The probands were instructed to teach at least one of their first-degree female relatives (21+ years of age) about breast cancer screening techniques. Three to six months after the enrollment of the probands, their relatives were contacted by telephone to determine breast cancer screening practices. A total of 79 probands and 96 relatives participated in the study. Relatives in the education group when compared with the control group were: 1.25 times more likely to have clinical breast examination (p = 0.005), 2.83 times more likely to have scheduled a clinical breast examination (p = 0.046), and, 1.36 times more likely to have been told about performing breast self-examination (p = 0.05). Additionally, relatives in the education group were more likely to have received a pamphlet on breast cancer screening (RR = 1.58, p = 0.009) and have discussed the importance of breast cancer screening (RR = 1.33, p = 0.020) from the proband. Special education training did not impact mammography utilization of the relatives. From these findings, a tri-ethnic group of low-income women with breast cancer can be effective teachers of breast cancer screening practices, at least for promoting clinical breast examination and transmitting messaging for performance of breast self-examination if given the adequate training.

Tumor Gene Expression and Prognosis in Breast Cancer Patients with 10 or More Positive Lymph Nodes

PURPOSE

This study, along with two others, was done to develop the 21-gene Recurrence Score assay (Oncotype DX) that was validated in a subsequent independent study and is used to aid decision making about chemotherapy in estrogen receptor (ER)-positive, node-negative breast cancer patients.

EXPERIMENTAL DESIGN

Patients with >or=10 nodes diagnosed from 1979 to 1999 were identified. RNA was extracted from paraffin blocks, and expression of 203 candidate genes was quantified using reverse transcription-PCR (RT-PCR).

RESULTS

Seventy-eight patients were studied. As of August 2002, 77% of patients had distant recurrence or breast cancer death. Univariate Cox analysis of clinical and immunohistochemistry variables indicated that HER2/immunohistochemistry, number of involved nodes, progesterone receptor (PR)/immunohistochemistry (% cells), and ER/immunohistochemistry (% cells) were significantly associated with distant recurrence-free survival (DRFS). Univariate Cox analysis identified 22 genes associated with DRFS. Higher expression correlated with shorter DRFS for the HER2 adaptor GRB7 and the macrophage marker CD68. Higher expression correlated with longer DRFS for tumor protein p53-binding protein 2 (TP53BP2) and the ER axis genes PR and Bcl2. Multivariate methods, including stepwise variable selection and bootstrap resampling of the Cox proportional hazards regression model, identified several genes, including TP53BP2 and Bcl2, as significant predictors of DRFS.

CONCLUSION

Tumor gene expression profiles of archival tissues, some more than 20 years old, provide significant information about risk of distant recurrence even among patients with 10 or more nodes.

Evaluation of Clinical Outcomes According to HER2 Detection by Fluorescence In Situ Hybridization in Women with Metastatic Breast Cancer Treated with Trastuzumab

BACKGROUND

We evaluated the influence of HER2 gene amplification, as determined by fluorescence in situ hybridization (FISH), on clinical outcomes (objective response rates, time to disease progression, and overall survival time) in women with metastatic breast cancer treated with trastuzumab in 3 clinical trials. Breast cancer tissue specimens were evaluated using a direct labeled, dual-probe FISH assay.

MATERIALS AND METHODS

Specimens with a HER2:CEP17 ratio of > or = 2:0 were considered positive for gene amplification. All specimens had previously demonstrated overexpression of HER2 protein at the 2+ or 3+ level by immunohistochemistry using the Clinical Trials Assay. Response rate, time to disease progression, and survival times were then compared between the FISH-positive and FISH-negative cohorts in each of the 3 clinical trials.

RESULTS

Informative FISH results were obtained in 765 (96%) of the 799 patients enrolled in the 3 clinical trials. Overall, 596 (78%) were FISH-positive and 169 (22%) were FISH-negative. The proportion of FISH-positive patients was comparable in all 3 trials. Clinical benefit from trastuzumab therapy appeared to be restricted to patients with FISH-positive metastatic breast cancer. In each clinical trial, the cohort of FISH-positive patients had higher overall response rates and longer durations of survival compared with FISH-negative patients.

CONCLUSION

These data indicate that assessment of HER2 amplification by FISH is the preferred method to select patients for trastuzumab therapy.

Randomized phase III trial of capecitabine compared with bevacizumab plus capecitabine in patients with previously treated metastatic breast cancer

PURPOSE

This randomized phase III trial compared the efficacy and safety of capecitabine with or without bevacizumab, a monoclonal antibody to vascular endothelial growth factor, in patients with metastatic breast cancer previously treated with an anthracycline and a taxane.

PATIENTS AND METHODS

Patients were randomly assigned to receive capecitabine (2,500 mg/m2/d) twice daily on day 1 through 14 every 3 weeks, alone or in combination with bevacizumab (15 mg/kg) on day 1. The primary end point was progression-free survival (PFS), as determined by an independent review facility.

RESULTS

From November 2000 to March 2002, 462 patients were enrolled. Treatment arms were balanced. No significant differences were found in the incidence of diarrhea, hand-foot syndrome, thromboembolic events, or serious bleeding episodes between treatment groups. Of other grade 3 or 4 adverse events, only hypertension requiring treatment (17.9% v 0.5%) was more frequent in patients receiving bevacizumab. Combination therapy significantly increased the response rates (19.8% v 9.1%; P = .001); however, this did not result in a longer PFS (4.86 v 4.17 months; hazard ratio = 0.98). Overall survival (15.1 v 14.5 months) and time to deterioration in quality of life as measured by the Functional Assessment Of Cancer Treatment--Breast were comparable in both treatment groups.

CONCLUSION

Bevacizumab was well tolerated in this heavily pretreated patient population. Although the addition of bevacizumab to capecitabine produced a significant increase in response rates, this did not translate into improved PFS or overall survival.

A randomized phase II feasibility trial of BMS-275291 in patients with early stage breast cancer

PURPOSE

This pilot trial was performed to evaluate the safety, pharmacokinetics and feasibility of incorporating BMS-275291, a matrix metalloproteinase inhibitor (MMPI), into adjuvant breast cancer therapy.

EXPERIMENTAL DESIGN

Patients with stage I (T1c)-IIIA breast cancer were eligible if planned adjuvant therapy consisted of either tamoxifen alone, doxorubicin + cyclophosphamide every 21 days for four cycles (AC), or AC followed by paclitaxel every 21 days for 4 cycles (AC>T). Patients were stratified by planned adjuvant therapy and randomized (2:1 ratio) to BMS-275291 (1200 mg/day) or matched placebo for 1 year.

RESULTS

Seventy-two patients were recruited from March 2001 to July 2002. Grade >or=2 musculoskeletal toxicity, generally reversible arthralgia, was reported by 36.2% of patients receiving BMS-275291 compared with 16.7% of patients receiving placebo; difference = 19.5% (95% confidence interval: -0.06, 0.44; P = NS). Two patients receiving BMS-275291 developed palpable nodules along tendons. Grade >or=3 rash was reported by 8.5% of patients receiving BMS-275291 compared with 4.2% of patients receiving placebo; difference = 4.3% (95% confidence interval: -0.18, 0.3; P = NS). Overall, 33% of BMS-275291 patients and 21% of placebo patients discontinued treatment due to adverse events. BMS-275291 trough levels tended to decrease over time; 9 of 47 (19%) had >or=50% of trough concentrations > 124 ng/ml (IC(90) for matrix metalloproteinase-9).

CONCLUSIONS

The pattern of arthralgia in BMS-275291-treated patients was consistent with matrix metalloproteinase inhibitor toxicity. Although the differential incidence of arthralgia did not reach statistical significance, the trial was terminated. An adjuvant trial in this patient population is not feasible.

American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer: status report 2004

PURPOSE

To update the 2003 American Society of Clinical Oncology technology assessment on adjuvant use of aromatase inhibitors.

RECOMMENDATIONS

Based on results from multiple large randomized trials, adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer should include an aromatase inhibitor in order to lower the risk of tumor recurrence. Neither the optimal timing nor duration of aromatase inhibitor therapy is established. Aromatase inhibitors are appropriate as initial treatment for women with contraindications to tamoxifen. For all other postmenopausal women, treatment options include 5 years of aromatase inhibitors treatment or sequential therapy consisting of tamoxifen (for either 2 to 3 years or 5 years) followed by aromatase inhibitors for 2 to 3, or 5 years. Patients intolerant of aromatase inhibitors should receive tamoxifen. There are no data on the use of tamoxifen after an aromatase inhibitor in the adjuvant setting. Women with hormone receptor-negative tumors should not receive adjuvant endocrine therapy. The role of other biomarkers such as progesterone receptor and HER2 status in selecting optimal endocrine therapy remains controversial. Aromatase inhibitors are contraindicated in premenopausal women; there are limited data concerning their role in women with treatment-related amenorrhea. The side effect profiles of tamoxifen and aromatase inhibitors differ. The late consequences of aromatase inhibitor therapy, including osteoporosis, are not well characterized.

CONCLUSION

The Panel believes that optimal adjuvant hormonal therapy for a postmenopausal woman with receptor-positive breast cancer includes an aromatase inhibitor as initial therapy or after treatment with tamoxifen. Women with breast cancer and their physicians must weigh the risks and benefits of all therapeutic options.

A phase I/II dose-escalation trial of bevacizumab in previously treated metastatic breast cancer

Vascular endothelial growth factor promotes angiogenesis, an important mediator of growth and metastasis in human breast cancer. Bevacizumab, a monoclonal antibody to vascular endothelial growth factor, is under investigation as an anti-angiogenic agent. This phase I/II trial evaluated the safety and efficacy of bevacizumab in patients with previously treated metastatic breast cancer. Seventy-five patients were treated with escalating doses of bevacizumab ranging from 3 mg/kg to 20 mg/kg administered intravenously every other week. Tumor response was assessed before the sixth (70 days) and 12th (154 days) doses. Safety was evaluated during every cycle. Eighteen patients were treated at 3 mg/kg, 41 at 10 mg/kg, and 16 at 20 mg/kg. Four patients discontinued study treatment because of an adverse event. Hypertension was reported as an adverse event in 17 patients (22%). The overall response rate was 9.3% (confirmed response rate, 6.7%). The median duration of confirmed response was 5.5 months (range, 2.3 to 13.7 months). At the final tumor assessment on day 154, 12 of 75 patients (16%) had stable disease or an ongoing response. The optimal dose of bevacizumab in this trial was 10 mg/kg every other week and toxicity was acceptable. These data support the initiation of trials in metastatic breast cancer combining bevacizumab with chemotherapy.

American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for women with hormone receptor-positive breast cancer: status report 2002

OBJECTIVE

To conduct an evidence-based technology assessment to determine whether the routine use of anastrozole or any of the aromatase inhibitors in the adjuvant breast cancer setting is appropriate for broad-based conventional use in clinical practice. POTENTIAL INTERVENTIONS: Anastrozole, letrozole, and exemestane.

OUTCOMES

Outcomes of interest include breast cancer incidence, breast cancer-specific survival, overall survival, and net health benefit.

EVIDENCE

A comprehensive, formal literature review was conducted for relevant topics and is detailed in the text. Testimony was collected from invited experts and interested parties. The American Society of Clinical Oncology (ASCO)-prescribed technology assessment procedure was followed. BENEFITS/HARMS: The ASCO panel recognizes that a woman and her physician's decision regarding adjuvant hormonal therapy is complex and will depend on the importance and weight attributed to information regarding both cancer and non-cancer-related risks and benefits.

CONCLUSION

The panel was influenced by the compelling, extensive, and long-term data available on tamoxifen. Overall, the panel considers the results of the Arimidex (anastrozole) or Tamoxifen Alone or in Combination (ATAC) trial and the extensive supporting data to be very promising but insufficient to change the standard practice at this time (May 2002). A 5-year course of adjuvant tamoxifen remains the standard therapy for women with hormone receptor-positive breast cancer. The panel recommends that physicians discuss the available information with patients, and, in making a decision, acknowledge that treatment approaches can change over time. Individual health care providers and their patients will need to come to their own conclusions, with careful consideration of all of the available data. (Specific questions addressed by the panel are summarized in Appendix 3.)

VALIDATION

The conclusions of the panel were endorsed by the ASCO Health Services Research Committee and the ASCO Board of Directors.

Efficacy and safety of trastuzumab as a single agent in first-line treatment of HER2-overexpressing metastatic breast cancer

PURPOSE

To evaluate the efficacy and safety of first-line, single-agent trastuzumab in women with HER2-overexpressing metastatic breast cancer.

PATIENTS AND METHODS

One hundred fourteen women with HER2-overexpressing metastatic breast cancer were randomized to receive first-line treatment with trastuzumab 4 mg/kg loading dose, followed by 2 mg/kg weekly, or a higher 8 mg/kg loading dose, followed by 4 mg/kg weekly.

RESULTS

The objective response rate was 26% (95% confidence interval [CI], 18.2% to 34.4%), with seven complete and 23 partial responses. Response rates in 111 assessable patients with 3+ and 2+ HER2 overexpression by immunohistochemistry (IHC) were 35% (95% CI, 24.4% to 44.7%) and none (95% CI, 0% to 15.5%), respectively. The clinical benefit rates in assessable patients with 3+ and 2+ HER2 overexpression were 48% and 7%, respectively. The response rates in 108 assessable patients with and without HER2 gene amplification by fluorescence in situ hybridization (FISH) analysis were 34% (95% CI, 23.9% to 45.7%) and 7% (95% CI, 0.8% to 22.8%), respectively. Seventeen (57%) of 30 patients with an objective response and 22 (51%) of 43 patients with clinical benefit had not experienced disease progression at follow-up at 12 months or later. The most common treatment-related adverse events were chills (25% of patients), asthenia (23%), fever (22%), pain (18%), and nausea (14%). Cardiac dysfunction occurred in two patients (2%); both had histories of cardiac disease and did not require additional intervention after discontinuation of trastuzumab. There was no clear evidence of a dose-response relationship for response, survival, or adverse events.

CONCLUSION

Single-agent trastuzumab is active and well tolerated as first-line treatment of women with metastatic breast cancer with HER2 3+ overexpression by IHC or gene amplification by FISH.