Long-term outcomes by lobular vs ductal histology in 4 National Surgical Adjuvant Breast and Bowel Project adjuvant breast cancer trials

Abstract

Abstract We evaluated differences in long-term outcomes of invasive lobular carcinoma vs breast cancers of no special type treated with anthracycline-based adjuvant chemotherapy using 4 National Surgical Adjuvant Breast and Bowel Project randomized phase III trials (B-22, B-25, B-28, and B-30). Our cohort included 11 251 patients with no special type and 1231 with invasive lobular carcinoma. Patients with invasive lobular carcinoma were older, had larger and more frequently estrogen receptor–positive tumors, and more positive lymph nodes. During early follow-up (0-5 years), patients with invasive lobular carcinoma had fewer recurrences (hazard ratio [HR] = 0.797, 95% confidence interval [CI] = 0.685 to 0.929) and deaths (HR = 0.756, 95% CI = 0.623 to 0.917). After 5 years, patients with invasive lobular carcinoma had more recurrences (HR = 1.30, 95% CI = 1.085 to 1.558) and deaths (HR = 1.044, 95% CI = 0.898 to 1.214). Conditional probability analysis showed statistically significant interactions between time-period and histologic type for recurrences (P < .001) and deaths (P < .001). Patients with invasive lobular carcinoma have elevated risk of late recurrence and death compared with patients with no special type cancers.