For patients with hormone receptor–positive, HER2-negative metastatic breast cancer, response rates for platinum-based chemotherapy were lower than historically observed in patients with triple-negative breast cancer, associated with poor outcomes.
It is known that platinum-based chemotherapy regimens have activity in triple-negative breast cancer, with response rates of approximately 50%. However, there is scarce evidence for activity of these regimens for hormone receptor–positive breast cancer. The effectiveness of platinum-based chemotherapy for hormone receptor–positive, HER2-negative metastatic breast cancer was therefore evaluated by Lucas Fernando Uratani, MD, and colleagues at the Instituto do Câncer do Estado de São Paulo, Brazil.
In this study, the investigators retrospectively evaluated the electronic medical records of patients with hormone receptor–positive, HER2-negative metastatic breast cancer who received ≥1 doses of platinum-based chemotherapy in the metastatic setting in the time frame between January 2015 and May 2020. In this single cancer center trial, clinical and demographic features, treatment, and outcomes data were collected. Clinical benefit rate at 3 months was the primary study end point. Overall response rate, progression-free survival (PFS), overall survival (OS), and prognostic factors were considered secondary end points.
Overall, 244 women were included in the study, with a median age of 51.5 years. Of these, 59% were premenopausal, 32.8% had metastatic disease at the time of diagnosis, 63.5% had an Eastern Cooperative Oncology Group (ECOG) performance status 0-1 by the time platinum-based chemotherapy was initiated, and 41% of patients met criteria for hereditary cancer testing, although tests for hereditary breast and ovarian cancer were not available. The majority (92.2%) of patients had estrogen receptor–positive (>10%) disease, 90.2% had invasive ductal carcinoma disease, and 69.7% had progesterone receptor–positive (>10%) disease.
The major sites of metastases were bone (76.2%), lymph nodes (59.4%), lung (52.9%), and liver (62.7%). Previous palliative systemic therapy before platinum-based chemotherapy had been received by most patients; however, previous palliative endocrine therapy had not been administered to 36.5% of patients, and previous palliative chemotherapy had not been administered to 30.7% of patients.
Cisplatin plus gemcitabine was the preferred platinum-based chemotherapy regimen (68.8%); however, a small number of patients (14.3%) received single-agent platinum-based chemotherapy.
Platinum-based chemotherapy was initiated during hospitalization in 43 (17.7%) patients. Toxicities related to grade 3/4 treatment occurred in 40.9% of the patients. At 3 months, the clinical benefit rate was 41.2% in the overall population, 46.7% when platinum-based chemotherapy was used as first-line, and 38.6% when platinum-based chemotherapy was used as a subsequent line of chemotherapy. Overall response rate was 26.7% in first-line platinum-based chemotherapy and 18.1% in a subsequent line of chemotherapy. Respectively, the reported median PFS and OS were 3.2 months (95% confidence interval [CI], 2.8-3.8) and 8.6 months (95% CI, 6.8-9.9). The OS rate at 1 year was 37.1% (95% CI, 30.5%-43.7%). Variables associated with worse OS were presence of liver metastases (hazard ratio [HR], 1.61; 95% CI, 1.16-2.23; P = .004), ECOG performance score 3-4 (HR, 1.85; 95% CI, 1.21-2.82; P = .004), and initiating platinum-based chemotherapy during hospitalization (HR, 1.74; 95% CI, 1.18-2.56; P = .005).
The investigators concluded that while platinum-based chemotherapy for hormone receptor–positive, HER2-negative metastatic breast cancer showed some activity especially as first-line therapy, the response rates were lower than historically observed in triple-negative breast cancer. Furthermore, platinum-based chemotherapy was associated with poor PFS and OS outcomes. Prognostic factors that negatively impacted OS were ECOG performance score 3-4, presence of liver metastases, and initiation of platinum-based chemotherapy during hospitalization.
Source: Uratani LF, Sansone Bermejo F, Henrique P, et al. Effectiveness of platinum-based chemotherapy for hormone receptor-positive HER2-negative metastatic breast cancer. Presented at: 2020 San Antonio Breast Cancer Symposium, December 8-11, 2020. Abstract PS13-49.