Oncotype DX, PAM50, and MammaPrint are multigene tests that are being used clinically for early-stage breast cancer to predict recurrence risk and guide adjuvant chemotherapy decisions. These tests have been validated in multiple retrospective studies, and prospective clinical trials are in progress. The TAILORx trial uses the Oncotype DX recurrence score to assign estrogen receptor–positive (ER+), node-negative patients to chemotherapy plus hormonal therapy versus hormonal therapy alone. The RxPONDER (SWOG S1007) trial uses Oncotype DX in a similar approach but on node-positive patients, and it includes the PAM50 test as a secondary analysis. The MINDACT trial uses Mamma-Print and Adjuvant! Online for treatment arm assignments. MINDACT has very broad eligibility criteria and 2 secondary randomizations for selecting chemotherapy and hormonal therapy regimens. This article discusses how the latest results on cancer genome sequencing apply to early-stage breast cancer. Several hundred breast cancers have already undergone genome sequencing, and the somatic DNA changes found in the tumor, compared with the patient's normal DNA, have been identified. Higher rates of point mutations and chromosomal translocations are found in aromatase inhibitor–resistant ER+ cancers and in the basal-like and HER2-enriched breast cancer subtypes. Correlations of somatic mutations with neoadjuvant aromatase inhibitor response are discussed. Genome sequencing can potentially identify the molecular abnormalities that underlie the poor risk identified by multigene tests and provide potential new targets for therapy, but more clinical trials correlating clinical outcome and somatic DNA changes are needed.
Rodrigo Goncalves and Ron Bose
Noa Efrat Ben-Baruch, Ron Bose, Shyam M. Kavuri, Cynthia X. Ma, and Matthew J. Ellis
Activating mutations in the HER2 tyrosine kinase have been identified in human breast cancers that lack HER2 gene amplification. These patients are not candidates for HER2-targeted drugs under current standards of care, but preclinical data strongly suggest that these patients will benefit from anti-HER2 drugs. This case report describes a young woman with metastatic breast cancer whose tumor was found to carry a HER2 L755S mutation, which is in the kinase domain of HER2. Treatment with the second-generation HER2/EGFR tyrosine kinase inhibitor neratinib resulted in partial response and dramatic improvement in the patient's functional status. This partial response lasted 11 months, and when the patient's cancer progressed, she was treated with neratinib plus capecitabine and her cancer again responded. This second response parallels the benefit seen with continuing trastuzumab in HER2-amplified breast cancer after disease progression. This case represents the first report, to our knowledge, of successful single-agent treatment of HER2-mutated breast cancer. Two clinical trials of neratinib for HER2-mutated metastatic breast cancer are currently enrolling patients. Further, data from The Cancer Genome Atlas project have identified HER2 mutations in a wide range of solid tumors, including bladder, colorectal, and non–small cell lung cancers, suggesting that clinical trials of neratinib or neratinib-based combinations for HER2-mutated solid tumors is warranted.
Jing Xi, Aabha Oza, Shana Thomas, Foluso Ademuyiwa, Katherine Weilbaecher, Rama Suresh, Ron Bose, Mathew Cherian, Leonel Hernandez-Aya, Ashley Frith, Lindsay Peterson, Jingqin Luo, Jairam Krishnamurthy, and Cynthia X. Ma
Background: Cyclin-dependent kinase (CDK) 4/6 inhibitors are now the standard of care for hormone receptor–positive (HR+), HER2-negative (HER–) metastatic breast cancer (MBC). However, guidelines are lacking regarding their optimal sequencing with other available agents. This study examines physician practice patterns and treatment outcomes of palbociclib and subsequent therapies in a real-world setting. Methods: A retrospective chart review was conducted for consecutive patients with MBC who received palbociclib between February 2015 and August 2017 at the Alvin J. Siteman Cancer Center. Kaplan-Meier method was used to generate time-to-event curves and estimate median progression-free survival (mPFS). Log-rank test was used to compare differences. Results: A total of 200 patients, with a median age of 59.4 years and a follow-up of 19.5 months, were included. Palbociclib was most frequently combined with letrozole (73.5%), followed by fulvestrant (25%), anastrozole (1%), and tamoxifen (0.5%). Most patients received palbociclib in the endocrine-resistant setting (n=42, n=50, and n=108 in the first-, second-, and subsequent-line settings, respectively), and the fraction of patients receiving palbociclib as first- or second-line therapy increased in recent months (P=.0428). mPFS was 20.7, 12.8, and 4.0 months with palbociclib administered in the first-, second-, and subsequent-line settings, respectively (P<.0001). Incidences of grade 3/4 neutropenia (41.5%) and dose reductions (29%) were comparable to reports in the literature. Among patients whose disease progressed on palbociclib (n=104), the most frequent next-line treatment was capecitabine (n=21), followed by eribulin (n=16), nab-paclitaxel (n=15), and exemestane + everolimus (n=12). mPFS with hormone therapy alone or in combination with targeted agents (n=32) after first-, second-, and subsequent-line palbociclib was 17.0, 9.3, and 4.2 months, respectively (P=.04). mPFS with chemotherapy (n=70) was not reached, 4.7, and 4.1 months after first-, second-, and subsequent-line palbociclib, respectively (P=.56). Conclusions: Palbociclib is effective for HR+/HER2– MBC in real-world practice. Hormone therapy alone or in combination with targeted agents remains an effective option after palbociclib progression.