Can Locoregional Treatment of the Primary Tumor Improve Outcomes for Women With Stage IV Breast Cancer at Diagnosis?

Purpose: To examine the effect of locoregional treatment (LRT) of the primary tumor on survival in patients with Stage IV breast cancer at diagnosis. Methods and Materials: The study cohort comprised 733 women referred to the British Columbia Cancer Agency between 1996 and 2005 with newly diagnosed clinical or pathologic M1 breast cancer. Tumor and treatment characteristics, overall survival (OS), and locoregional progression-free survival were compared between patients treated with (n = 378) and without (n = 355) LRT of the primary disease. Multivariable analysis was performed with Cox regression modeling. Results: The median follow-up time was 1.9 years. LRT consisted of surgery alone in 67% of patients, radiotherapy alone in 22%, and both in 11%. LRT was used more commonly in women with age <50 years, Eastern Cooperative Oncology Group (ECOG) performance status 0–1, Stage T1–2 tumors, N0–1 disease, limited M1 burden, and asymptomatic M1 disease (all p < 0.05). Systemic therapy was used in 92% of patients who underwent LRT and 85% of patients who did not. In patients treated with LRT compared with those without LRT, the 5-year OS rates were 21% vs. 14% (p < 0.001), and the rates of locoregional progression-free survival were 72% vs. 46% (p < 0.001). Among 378 patients treated with LRT, the rates of 5-year OS were higher in patients with age <50, ECOG performance status 0–1, estrogen receptor–positive disease, clear surgical margins, single subsite, bone-only metastasis, and one to four metastatic lesions (all p < 0.003). On multivariable analysis, LRT was associated with improved OS (hazard ratio, 0.78; 95% confidence interval, 0.64–0.94, p = 0.009). Conclusion: Locoregional treatment of the primary disease is associated with improved survival in some women with Stage IV breast cancer at diagnosis. Among those treated with LRT, the most favorable rates of survival were observed in subsets with young age, good performance status, estrogen receptor–positive disease, clear margins, and distant disease limited to one subsite, bone-only involvement, or fewer than five metastatic lesions.