Background: Comparative real-world outcomes for patients with HER2-positive (HER2+) breast cancer receiving adjuvant trastuzumab outside of clinical trials are lacking. This study sought to retrospectively characterize outcomes for patients with node-negative and node-positive breast cancer receiving adjuvant trastuzumab in combination with docetaxel/cyclophosphamide (DCH), docetaxel/carboplatin/trastuzumab (TCH), or fluorouracil/epirubicin/cyclophosphamide followed by docetaxel/trastuzumab (FEC-DH) chemotherapy in Alberta, Canada, from 2007 through 2014. Methods: Disease-free survival and overall survival (OS) analyses for node-negative cohorts receiving DCH (n=111) or TCH (n=371) and node-positive cohorts receiving FEC-DH (n=146) or TCH (n=315) were compared using chi-square, Kaplan-Meier, or Cox multivariable analysis where appropriate. Results: Median follow-up was similar in node-negative (63.9 months) and node-positive (69.0 months) cohorts. The 5-year OS rates in patients with node-negative disease receiving DCH or TCH were similar (95.2% vs 96.9%; P=.268), whereas 5-year OS rates were higher but nonsignificant for patients with node-positive disease treated with FEC-DH compared with TCH (95.2% vs 91.4%; P=.160). Subgroup analysis of node-positive cohorts showed significantly improved OS with FEC-DH versus TCH in patients with estrogen receptor (ER)/progesterone receptor (PR)–positive breast cancer (98.3% vs 91.6%, respectively; P=.014). Conversely, patients with ER/PR-negative disease showed a nonsignificant trend toward higher OS rates with TCH versus FEC-DH (91.6% vs 83.3%, respectively; P=.298). Given the retrospective design, we were unable to capture all potential covariates that may have impacted treatment assignment and/or outcomes. Furthermore, cardiac toxicity data were unavailable. Conclusions: Survival rates of patients with HER2+ breast cancer in our study are comparable to those seen in clinical trials. Our findings support chemotherapy de-escalation in patients with node-negative disease and validate the efficacy of FEC-DH in those with node-positive disease.
Real-World Outcomes of Adjuvant Chemotherapy for Node-Negative and Node-Positive HER2-Positive Breast Cancer
Zachary Veitch, Omar F. Khan, Derek Tilley, Domen Ribnikar, Xanthoula Kostaras, Karen King, Patricia Tang, and Sasha Lupichuk
Impact of Cumulative Chemotherapy Dose on Survival With Adjuvant FEC-D Chemotherapy for Breast Cancer
Zachary Veitch, Omar F. Khan, Derek Tilley, Patricia A. Tang, Domen Ribnikar, Douglas A. Stewart, Xanthoula Kostaras, Karen King, and Sasha Lupichuk
Background: Reductions in adjuvant chemotherapy dose <85% for historical regimens (ie, cyclophosphamide/methotrexate/fluorouracil) are known to affect breast cancer survival. This threshold, in addition to early versus late dose reductions, are poorly defined for third-generation anthracycline/taxane-based chemotherapy. In patients with breast cancer receiving adjuvant 5-fluorouracil/epirubicin/cyclophosphamide followed by docetaxel (FEC-D), we evaluated the impact of chemotherapy total cumulative dose (TCD), and early (FEC) versus late (D only) dose reductions, on survival outcomes. Patients and Methods: Women with stage I–III, hormone receptor–positive/negative, HER2-negative breast cancer treated with adjuvant FEC-D chemotherapy from 2007 through 2014 in Alberta, Canada, were included. TCD for cycles 1 to 6 of <85% or ≥85% was calculated. Average cumulative dose was also calculated for early (cycles 1–3) and late (cycles 4–6) chemotherapy. Survival outcomes (disease-free survival [DFS] and overall survival [OS]) were estimated using Kaplan-Meier and multivariate analysis. Cohorts were evaluated for uniformity. Results: Characteristics were reasonably balanced for all cohorts. Overall, 1,302 patients were evaluated for dose reductions, with 16% being reduced <85% (n=202) relative to ≥85% (n=1,100; 84%). Patients who received TCD ≥85% relative to <85% had superior 5-year DFS (P=.025) and OS (P<.001) according to Kaplan-Meier analysis, which remained significant on univariate and multivariate analyses. In stratified late and early dose reduction cohorts, DFS and OS showed a significant inferior survival trend for dose reduction early in treatment administration in 5-year Kaplan-Meier (P=.002 and P<.001, respectively) and multivariate analyses (hazard ratio [HR], 1.46; P=.073, and HR, 1.77; P=.011, respectively). Dose delays of <14 or ≥14 days and granulocyte colony-stimulating factor use did not affect outcomes. Conclusions: Chemotherapy TCD <85% for adjuvant FEC-D affects breast cancer survival. Late reductions (D only) were not shown to adversely affect DFS or OS. Conversely, early reductions (FEC±D) negatively affected patient outcomes.