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Can locoregional treatment of the primary tumor improve outcomes for women with stage IV breast cancer at diagnosis?

89 Background: To determine whether locoregional treatment (LRT) of the primary tumor improves outcomes in patients with stage IV breast cancer at diagnosis.


METHODS
The study cohort comprised 733 women referred from 1996 to 2005 to a population-based cancer institution with clinical or pathologic M1 breast cancer at diagnosis. Patient, tumor, and treatment characteristics were compared between women who were treated with (n=378) and without LRT (n=355) of the primary tumor. Five-year Kaplan-Meier overall survival (OS) and locoregional progression-free survival (LRPFS) were compared between groups. Multivariable analysis to control for potential confounding factors was performed using Cox regression modeling.


RESULTS
LRT consisted of surgery alone in 67%, radiotherapy alone in 22%, and both in 11% of patients. LRT use was significantly associated with age <50 years, ECOG performance status 0-1, T1-2 tumors, and N0-1 disease, (all p<0.05). Subjects with less metastatic disease burden and those asymptomatic from the M1 disease were more likely to undergo LRT (p<0.001). Systemic therapy was used in 92% and 85% of patients treated with vs. without LRT, respectively. Five-year OS rates in the LRT and no LRT cohorts were 21% vs 14% (p<0.001). The 5-year LRPFS rates were 72% vs 46% (p<0.001). Among 378 patients who underwent LRT, 5-year OS rates were higher in patients with age <50, ECOG 0-1, ER positive disease, clear surgical margins, single M1 subsite, bone only metastases, and 1-3 metastatic lesions (all p<0.003). Type of LRT (surgery vs radiotherapy vs both) and type of surgery (lumpectomy vs mastectomy) were not associated with 5-year OS (all p>0.05). On multivariable analysis, LRT was associated with improved OS (hazard ratio 0.78, 95% confidence interval 0.64-0.94, p=0.009).


CONCLUSIONS
LRT of the primary disease was associated with improved survival in women with stage IV breast cancer at diagnosis. Among subjects treated with LRT, the most favorable survival rates were observed in patients with young age, good performance status, ER-positive disease, clear resection margins and in those with distant disease limited to one subsite, bone only, or fewer than 4 metastatic lesions.