ASSESSMENT OF TUMOR SIZE FOR MULTIFOCAL PRIMARY BREAST-CANCER

Background: Tumor size affects the choice of surgical procedure and pa tient prognosis. It is standardly assessed as the largest unidimension al measurement and, for multifocal disease, as the largest size of the largest focus. We examine some different methods of assessing tumor s ize: the standard method; the sum of the largest sizes for all foci; s urface area; and volume. Methods: Data for a cohort of 678 primary inv asive breast cancer patients accrued from 1971 to 1990 were updated to 1996; there were 571 patients with unifocal disease and 107 patients with multifocal disease. We used step-wise Cox regression to investiga te the effects on time to death of the prognostic factors tumor size ( estimated in one of the four ways), age, nodal status, ER, PgR, adjuva nt radiotherapy, adjuvant hormonal therapy, and adjuvant chemotherapy, We also examined the association between tumor focality and nodal sta tus. Results: For all patients, tumor size was included in the multiva riate model, regardless of estimation method. For patients with multif ocal disease, tumor size was included in the final model only when it was estimated as the total surface area (P =.03) or volume (P =.01) of the foci, More multifocal patients were N+ (P =.056). Conclusions: Fo r patients with multifocal disease, the significance association with mortality for total surface area or volume may imply a biologic releva nce or mode of tumor activity for the foci.