Diminished survival in patients with inner versus outer quadrant breast cancers

To evaluate the role of breast tumor location on survival in patients with breast cancer.

We evaluated tumor location within the breast on breast cancer-specific survival (BCSS) and overall survival (OS) in patients with invasive breast cancer using the Surveillance, Epidemiology, and End-Results (SEER) registries in the United States. Effects on survival were evaluated according to age, stage, tumor site, tumor size, grade, axillary lymph node status, extent of surgery, and radiotherapy (RT). A multivariate model was used with complete data on 45,880 patients. The median follow-up was 59 months.

Patients with outer tumor location demonstrated superior BCSS on Kaplan-Meier analysis for both local stage (node-negative, P <.001) and regional stage disease (node-positive, P =.0002). For BCSS, the hazard ratio (HR) for inner quadrant location compared with outer quadrant was 1.31 (95% confidence interval [CI], 1.19 to 1.37; P <.001); and for OS, the HR was 1.12 (95% CI, 1.05 to 1.17; P <.001). When ER and PR status were included in the model, the HR for inner quadrant location compared with outer quadrant was 1.27 for BCSS (95% CI, 1.16 to 1.40; P <.001) and 1.11 for OS (95% CI, 1.03 to 1.19; P =.004). Patients treated by lumpectomy that received RT had a superior OS compared with patients that did not receive RT in both local (HR, 0.52; 95% CI, 0.48 to 0.61; P <.001) and regional (HR, 0.63; 95% CI, 0.56 to 0.72; P <.001) stage disease. Mastectomy patients with local stage disease that received RT had a diminished OS (HR, 1.24; 95% CI, 1.02 to 1.50; P =.033).

On multivariate analysis, incorporating data on age, stage, tumor site, tumor size, grade, ER and PR status, axillary lymph node status, extent of surgery, and RT, this SEER registry-based study demonstrates that medial tumor location adversely impacts BCSS and OS.