NSABP B-13
In ER-negative, node-negative breast cancer after surgery, does adjuvant methotrexate plus fluorouracil improve disease control compared with surgery alone?
Absolute Effect
At 8 years, overall DFS was 74% vs 59%, an absolute improvement of 15 percentage points (approximate NNT 7).
At 16 years, RFS remained improved: HR 0.59 (95% CI 0.44–0.78), with an OS benefit (HR 0.75, 95% CI 0.58–0.98).
Clinical interpretation
B-13 established that node-negative ER-negative disease was not uniformly low-risk and could derive substantial benefit from adjuvant chemotherapy. The 15-point 8-year DFS gain is an unusually large absolute treatment effect for an adjuvant breast trial.
Toxicity
Sequential MF was less toxic than CMF in the related B-19 comparison; no single fixed-time toxicity endpoint from B-13 supports a defensible NNH.
Primary sources
Fisher B, et al. J Clin Oncol. 1996;14:1982–1992. DOI 10.1200/JCO.1996.14.7.1982.