PAM50 breast cancer intrinsic subtypes and effect of gemcitabine in advanced breast cancer patients.

BACKGROUND: In vitro studies suggest basal breast cancers are more sensitive to gemcitabine relative to other intrinsic subtypes. The main objective of this study was to use specimens from a randomized clinical trial to evaluate whether the basal-like subtype identifies patients with advanced breast cancer who benefit from gemcitabine plus docetaxel (GD) compared to single agent docetaxel (D). MATERIAL AND METHODS: From patients randomly assigned to GD or D, RNA was isolated from archival formalin-fixed, paraffin-embedded primary breast tumor tissue and used for PAM50 intrinsic subtyping by NanoString nCounter. Statistical analyses were prespecified as a formal prospective-retrospective clinical trial correlative study. Using time to progression (TTP) as primary endpoint, overall survival (OS) and response rate as secondary endpoints, relationships between subtypes and outcome after chemotherapy were analyzed by the Kaplan-Meier method, and Cox proportional hazards regression models. Data analysis was performed independently by the Danish Breast Cancer Cooperative Group (DBCG) statistical core and all statistical tests were two-sided. RESULTS: RNA from 270 patients was evaluable; 84 patients (31%) were classified as luminal A, 97 (36%) luminal B, 43 (16%) basal-like, and 46 (17%) as HER2-enriched. PAM50 intrinsic subtype was a significant independent prognostic factor for both TTP (p=0.014) and OS (p=0.0003). Response rate was not different by subtype, and PAM50 was not a predictor of TTP by treatment arm. PAM50 was however a highly significant predictor of OS following GD compared to D (pinteraction=0.0016). Patients with a basal-like subtype had a significant reduction in OS events [hazard ratio (HR)=0.29, 95% confidence interval (CI)=0.15-0.57; pinteraction=0.0006]. CONCLUSION: A significantly improved and clinically important prolongation of survival was seen from the addition of gemcitabine to docetaxel in advanced basal-like breast cancer patients.

Gene aberrations of RRM1 and RRM2B and outcome of advanced breast cancer after treatment with docetaxel with or without gemcitabine.

BACKGROUND: The purpose of the present study was to retrospectively evaluate whether copy number changes of the genes encoding the ribonucleotide reductase subunit M1 (RRM1) and/or subunit M2B (RRM2B) predict sensitivity to gemcitabine administered in combination with docetaxel compared to single agent docetaxel in advanced breast cancer patients. METHODS: Primary tumor samples from patients randomly assigned to gemcitabine plus docetaxel or docetaxel alone were analyzed for RRM1 and RRM2B copy number changes using Fluorescence In Situ Hybridization (FISH) technology with probes covering respectively RRM1 at 11p15.5 and a reference probe covering the centromere of chromosome 11 (CEN-11), and RRM2B at 8q22.3 and a reference probe covering the centromere of chromosome 8 (CEN-8). The assays were validated in a material of 60 normal breast samples. Time to progression (TTP) was the primary endpoint. Overall survival (OS) and response rate (RR) were secondary endpoints. Associations between RRM1/CEN-11 and/or RRM2B/CEN-8 ratios and time-to-event endpoints were analyzed by unadjusted and adjusted Cox proportional hazards regression models. Heterogeneity of treatment effects on TTP and OS according to gene status were investigated by subgroup analyses, and the Wald test was applied. All statistical tests were two-sided. RESULTS: FISH analysis for both RRM1 and RRM2B was successful in 251 patients. RRM1 and RRM2B aberrations (deletions and amplifications) were observed in 15.9% and 13.6% of patients, respectively. RRM1 aberrations were associated with a decreased OS in the time interval 1.5-7.4 years (hazard ratio = 1.72, 95% confidence interval = 1.05-2.79, P = 0.03). RRM2B aberrations alone or in combination with RRM1 aberrations had no prognostic impact in terms of TTP or OS. RR was not different by gene status. No significant differences were detected in TTP or OS within subgroups according to gene status and chemotherapy regimen. CONCLUSIONS: This study demonstrated the presence of RRM1 and RRM2B copy number changes in primary breast tumor specimens. Nevertheless, we found no support of the hypothesis that aberrations of RRM1 or RRM2B, neither individually nor in combination, are associated with an altered clinical outcome following chemotherapy with gemcitabine in combination with docetaxel compared to docetaxel alone in advanced breast cancer patients.

Gemcitabine plus docetaxel versus docetaxel in patients with predominantly human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer: a randomized, phase III study by the Danish Breast Cancer Cooperative Group.

PURPOSE: The objective of this phase III study was to compare the efficacy of gemcitabine plus docetaxel (GD) versus docetaxel in patients with advanced breast cancer. PATIENTS AND METHODS: Predominantly human epidermal growth factor receptor 2 (HER2) -negative patients were randomly assigned to gemcitabine (1,000 mg/m(2)) on days 1 and 8 plus docetaxel (75 mg/m(2)) on day 8 or to docetaxel (100 mg/m(2)) on day 1, every 21 days. Patients were untreated or had prior (neo)adjuvant chemotherapy or a single anthracycline-based chemotherapy regimen for metastatic breast cancer. The primary end point was time to progression (TTP), and secondary end points were overall survival (OS), response rate (RR), and toxicity. RESULTS: A total of 170 patients were allocated to GD, and 167 were allocated to docetaxel. Median TTP on GD was 10.3 months versus 8.3 months on docetaxel (hazard ratio [HR], 0.77; 95% CI, 0.59 to 1.01; log-rank P = .06). The adjusted Cox proportional model for TTP showed a significant difference favoring the combination (HR, 0.68; 95% CI, 0.51 to 0.90; P = .007). However, RR was similar (GD, 36%; docetaxel, 34%), and OS was not different (P = .57). Grades 3 to 4 neutropenia was common (GD, 75%; docetaxel, 69%); infection was reported in 26% and 21% of patients in the GD and docetaxel groups, respectively. Grades 3 to 4 thrombocytopenia was more frequent with GD (GD, 16%; docetaxel, 0.6%), and peripheral neuropathy was higher with docetaxel (GD, 5%; docetaxel, 16%). CONCLUSION: GD compared with docetaxel demonstrated increased TTP in metastatic breast cancer. However, RR and OS were similar. Thus, the addition of gemcitabine failed to demonstrate any clinically meaningful benefit when combined with docetaxel.