Breast cancer subtype approximated by estrogen receptor, progesterone receptor, and HER-2 is associated with local and distant recurrence after breast-conserving therapy

Purpose To determine whether breast cancer subtype is associated with outcome after breast-conserving therapy (BCT) consisting of lumpectomy and radiation therapy. Patients and Methods We studied 793 consecutive patients with invasive breast cancer who received BCT from July 1998 to December 2001. Among them, 97% had pathologically negative margins of resection, and 90% received adjuvant systemic therapy. No patient received adjuvant trastuzumab. Receptor status was used to approximate subtype: estrogen receptor (ER) or progesterone receptor (PR) positive and human epidermal growth factor receptor 2 negative = luminal A; ER + or PR + and HER-2 + = luminal B; ER- and PR- and HER-2 + = HER-2; and ER- and PR- and HER-2- = basal. Competing risks methodology was used to analyze time to local recurrence and distant metastases. Results Median follow-up was 70 months. The overall 5-year cumulative incidence of local recurrence was 1.8% (95% CI, 1.0 to 3.1); 0.8% (0.3, 2.2) for luminal A, 1.5% (0.2, 10) for luminal B, 8.4% (2.2, 30) for HER-2, and 7.1% (3.0, 16) for basal. On multivariable analysis (MVA) with luminal A as baseline, HER-2 (adjusted hazard ratio [AHR] = 9.2; 95% CI, 1.6 to 51; P = .012) and basal (AHR = 7.1; 95% CI, 1.6 to 31; P = .009) subtypes were associated with increased local recurrence. On MVA, luminal B (AHR = 2.9; 95% CI, 1.3 to 6.5; P = .007) and basal (AHR = 2.3; 95% CI, 1.1 to 5.2; P = .035) were associated with increased distant metastases. Conclusion Overall, the 5-year local recurrence rate after BCT was low, but varied by subtype as approximated using ER, PR, and HER-2 status. Local recurrence was particularly low for the luminal A subtype, but was less than 10% at 5 years for all subtypes. Although further follow-up is needed, these results may be useful in counseling patients about their anticipated outcome after BCT.