Influence of delayed initiation of adjuvant chemotherapy on breast cancer survival is subtype-dependent

PURPOSE: The optimal time from surgery to initiation of adjuvant chemotherapy of breast cancer is still controversial. We investigated the influence of time to adjuvant chemotherapy on survival outcomes according to breast cancer subtype. RESULTS: Longer delay of initiation of adjuvant chemotherapy (≤4 weeks versus >8 weeks)) significantly decreased the DFS (adjusted hazard ratio [HR] of 1.86; 95% confidence interval [CI], 1.19-2.90) and OS (adjusted HR of 2.02; 95% CI, 1.10-3.71). However, a moderate delay (≤4 weeks versus 4-8 weeks) did not significantly influence the survival. We further investigated the effect of time to adjuvant chemotherapy (≤8 versus >8 weeks) on survival according to subtypes. Patients with luminal-A tumors who received delayed chemotherapy had no increased risk of recurrence (HR of 1.15; 95% CI, 0.54-2.43). In contrast, patients with luminal-B, triple-negative, or trastuzumab-untreated HER2-positive tumors would have decreased DFS because of delayed chemotherapy, with HR of 1.93 (95% CI, 1.10-3.34), 2.55 (95% CI, 1.25-5.18), and 2.41 (95% CI, 1.36-4.26), respectively. METHODS: Operable women with stage I-IIIa breast cancer between 2003 and 2006 in our institution were included. 1,408 patients were divided into 3 groups according to the time to adjuvant chemotherapy: ≤4 weeks, 4-8 weeks, and >8 weeks. Disease-free survival (DFS) and overall survival (OS) were calculated. CONCLUSION: Longer delay of adjuvant chemotherapy was associated with worse survival and early initiation of adjuvant chemotherapy should be performed for patients with aggressive tumor subtypes.