Breast-conserving therapy for macroscopically multiple cancers.

Of 586 unilateral stage I-II breast cancers treated with conservative surgery and radiotherapy, 61 patients were found to have two or more macroscopic tumor nodules, diagnosed either clinically (n = 20), mammographically (n = 2), or on gross pathologic examination (n = 39). After a median follow-up of 71 months, 15 of 61 (25%) of the patients with multiple tumors developed recurrence in the treated breast, compared to 56 of 525 (11%) of patients with single cancers (p less than 0.005). Local failure occurred in 6 of 37 (16%) of bifocal tumors and in 9 of 24 (35%) of patients with 3 or more tumor foci. Recurrence was more frequent for multiplicity diagnosed clinically or mammographically (8 of 22 patients, 36%) than when it was apparent only to the pathologist (7 of 39 patients, 18%). Only 1 of 21 bifocal tumors diagnosed on gross examination recurred. Local failure occurred in only 1 of 22 cases with clearly negative resection margins; the remaining recurrences were associated with positive (n = 3) or indeterminate margins (n = 11). In contrast with recurrences of unifocal breast cancers, local failures in these patients tended to be located at a distance from the original foci, to be multifocal, or to be diffuse, including skin involvement. Only four recurrences presented as a single focus in the vicinity of the original primary tumors. This study indicates that macroscopically multiple breast cancers are at higher local failure risk, especially if multiplicity is clinically apparent, or if three or more gross nodules are seen on pathologic examination. Negative resection margins appear to be essential for satisfactory results.