The AJCC staging criteria consider
tumor size to be the largest dimension of largest
tumor. Some case series suggest using summation of all
tumor dimensions in patients with multicentric/multifocal (MC/MF) disease. We used data from NCIC CTG MA.5 and
MA.12 clinical trials to examine alternative methods of assessing
tumor size on
breast-cancer-free-interval (BCFI). The 710 MA.5 pre-/peri-menopausal node positive and 672
MA.12 pre-menopausal node-negative/-positive patients have 10-year median follow-up. All patients received
adjuvant chemotherapy.
Tumors were centrally reviewed for grade,
hormone receptor, and HER2 status. Continuous pathologic
tumor size was: (1) largest dimension of largest
tumor (cm); (2)
tumor area (
cm(2)); (3) volume of
tumor (cm(3)); (4) with MC/MF disease, summation of (1)-(3) for up to 3 foci. We examined univariate and multivariate effects of
tumor size on BCFI utilizing (un)stratified Cox regression and the Wald test statistic. In univariate analysis, larger
tumor dimension was significantly associated with worse BFCI in node positive patients: p < 0.0001 for MA.5; p = 0.01 for
MA.12. In MA.5 multivariate analysis, larger summation of largest
tumor dimensions was associated with worse BCFI (p = 0.0003), while larger single dimension was associated with worse BCFI (p = 0.02) for
MA.12. Presence of MC/MF and other
tumor size measurements were not associated (p > 0.05) with BFCI. While physicians could consider the largest diameter of the largest focus of disease or the sum of the largest diameters of all foci in their T-stage determination, it appears that the current method of T-staging offers equivalent determinations of prognosis.