The real-world experience of adjuvant docetaxel and cyclophosphamide (TC) chemotherapy in HER-2 negative breast cancer.

Abstract

538 Background: Adjuvant chemotherapy in breast cancer (BC) substantially improves overall survival (OS) and the risk of recurrence. The short and long-term side effects of anthracycline, and its modest benefits in the adjuvant setting, led to controversy about its role in comparison with TC. We aim to compare the OS of TC with anthracycline-based regimens in Ontario, the most populous province in Canada. Methods: We conducted a retrospective population-based cohort study using the Institute for Clinical Evaluative Sciences (ICES) database, involving females with stage I-III BC HER2-negative. Patients were treated with adjuvant chemotherapy between January 2009 to December 2017. The anthracycline regimens for comparison were as follows, FEC-D: Fluorouracil, Epirubicin, Cyclophosphamide, followed by Docetaxel; and ACT: Doxorubicin, Cyclophosphamide, followed by Docetaxel or Paclitaxel. Exclusion criteria included missing baseline characteristics, a prior history of malignancy or chemotherapy starting more than 120 days from breast surgery. The end of follow-up was March 31st, 2018. Adjusted analyses to compare OS by positive axillary lymph nodes (LN) and chemotherapy regimens were conducted with Cox proportional hazards models. Results: Of a total 10634 female patients with BC, 60% were ≥ 50 years-old, with 19.6% stage I, 61.1% stage II, and 19.3% stage III and 7130 (67%) women were classified as ER+ and 2379 (22.4%) as ER-. Among 5764 (54.2%) patients with positive LN, 4300 (40.4%) had LN 1-3 and 1464 (13.8%) had LN ≥ 4. There were 4945 (46.5%) high-grade cases. There were 2487 (23.5%) patients treated with TC, 2981 (28%) with ACT, and 5166 (48.5%) with FEC-D. With a median follow-up of 5.5 years, the OS comparison for the entire study population showed hazard ratio (HR) of TC vs ACT was 1.47 (95% CI 1.14 – 1.90), p = 0.0027 and TC vs FEC-D HR was 1.48 (95% CI 1.18 – 1.86), p = 0.0007. For ER+ patients treated with TC, the OS comparison of LN 1-3 and LN ≥ 4 vs. LN 0 showed HR 1.34 (95% CI 0.81 – 2.21), p = 0.26, and HR 4.29 (95% CI 2.09 – 8.79), p < 0.0001, respectively. For ER+ LN 0 patients, the OS HR of TC vs. ACT was 1.15 (95% CI 0.58 – 2.35), p = 0.67, and TC vs. FEC-D HR was 1.38 (95% CI 0.81 – 2.33), p = 0.23. For ER- patients treated with TC, the OS comparison of LN 1-3 and LN ≥ 4 vs. LN 0 showed HR 1.12 (95% CI 0.42 – 3.01), p = 0.82 and HR 4.41 (95% CI 1.33 – 14.59), p = 0.015, respectively. For ER- LN 0 patients, the OS HR for TC vs. ACT was 2.04 (95% CI 1.09 – 3.81), p = 0.025, and TC vs. FEC-D HR was 2.05 (95% CI 1.08 – 3.90), p = 0.028. Conclusions: Patients treated with adjuvant TC who had four or more axillary LN had significantly lower OS when compared to patients with LN 0. For women with ER- disease, TC demonstrated a significant unfavourable survival outcome when compared to anthracycline-based treatments.