Impact of postmastectomy radiotherapy in T3N0 invasive carcinoma of the breast: a Surveillance, Epidemiology, and End Results database analysis.

Background: Randomized trials provide evidence for improved outcomes with postmastectomy radiotherapy (PMRT) in high-risk patients. It has been suggested that patients with T3N0 breast cancer represent a favorable subgroup for which PMRT renders little benefit. In the current study, the authors used a United States population database to evaluate PMRT in this subgroup.

Methods: The cause-specific survival (CSS) and overall survival (OS) of women with T3N0M0 breast cancer in the Surveillance, Epidemiology, and End Results database after mastectomy and axillary staging from 1988 to 2002 were analyzed. Univariate analysis was performed to relate CSS with PMRT (yes vs no), tumor size (< or =7 cm vs >7 cm), grade (1 vs 2 or 3), patient age (< or =50 years vs >50 years), the number of lymph nodes dissected (< or =13 vs >13), and the era treated (1988-1997 vs 1998-2002). Multivariate analyses for CSS and OS were also performed.

Results: In total, 1865 women met the analysis criteria for OS; CSS data were available for 98.8% of those women. Of the women who were diagnosed during the era from 1988 to 1997, 22% received PMRT, and that rate increased to 41% during the era from 1998 to 2002. The actuarial 10-year CSS for those who received PMRT versus those who did not receive PMRT was 81.6% versus 79.8%, respectively (P = .38). PMRT was not associated with a CSS benefit in any subgroup, a finding that persisted in multivariate analyses. Women who received PMRT had an increased 10-year OS rate (70.7% vs 58.4%; P < .001) that was confined to women aged >50 years in a subgroup analysis.

Conclusions: This retrospective, population-based analysis demonstrated no increase in CSS with PMRT for women with T3N0 breast cancer, lending further support to the hypothesis that T3N0 disease postmastectomy represents a favorable subset of locally advanced breast cancer. The increased OS associated with PMRT in the absence of improved CSS likely reflects patient selection in this nonrandomized dataset. Prospective evaluation of PMRT in this population subset is warranted.