A Reappraisal of the Comparative Effectiveness of Lumpectomy Versus Mastectomy on Breast Cancer Survival: A Propensity Score-Matched Update From the National Cancer Data Base (NCDB).

Background: Recent observational studies are concerning because they document rising mastectomy rates coinciding with more than a dozen reports that lumpectomy has better overall survival (OS) than mastectomy. Our aim was to determine if there were differences in OS of matched breast cancer patients undergoing lumpectomy versus mastectomy in the National Cancer Database (NCDB).

Patients And Methods: A retrospective cohort of patients with stage I-III breast cancer in the NCDB (2004-2013) was identified. Propensity score matching (PSM), Kaplan-Meier, and multivariate Cox proportional hazards models were used to examine OS by type of surgery.

Results: Of 845,136 patients, 464,052 (54.9%) underwent lumpectomy and 381,084 (45.1%) underwent mastectomy. After PSM, the hazard ratio (HR) and confidence interval (CI) for OS in all patients comparing lumpectomy with mastectomy was 1.02 (CI, 1.00-1.04; P = .002). In patients with stage I, II, and III, they were HR 1.27 (CI, 1.23-1.36; P < .001), HR 0.98 (CI, 0.95-1.01; P = .21), and HR 0.83 (CI, 0.80-0.86; P < .001), respectively. In subgroup analyses of all patients by estrogen receptor (ER) status, they were HR 1.05 (CI, 1.03-1.07; P < .001) and HR 1.00 (CI, 0.96-1.03; P = .65) in ER+ and ER- patients.

Conclusion: In our primary model of all stage I-III matched patients, using the most recent NCDB data and the largest observational sample size to date, the OS after mastectomy was not inferior to lumpectomy. This finding can be reassuring to patients and providers. In subgroup analyses, the association between type of surgery and OS differed by cancer stage and hormone receptor status.