Separate cavity margins excision as a complement to conservative breast cancer surgery

Positive lumpectomy margins (LM) usually mandate re-excision. However, approximately half of these patients have no residual tumour in the re-excision specimen. The aim of this study was to investigate if separate cavity margin (CM) excision can safely reduce the need of re-operation.

Rate of re-operation for margin involvement and incidence of residual tumour in the re-excision specimen were retrospectively evaluated in 237 patients (group A) who underwent lumpectomy alone, and in 271 patients (group B) treated by lumpectomy and CM excision. Patients with positive LM (group A) or CM (group B) underwent re-excision.

In the group A, 50/237 patients (21.1%) had LM+ and underwent re-excision. In the group B, 74/271 patients (27.3%) had LM+, but tumour was found within the CM specimen in 46 patients (17.0%), 24 LM+ and 22 LM-, and reached the CM cut edge in only 15 (5.5%), who finally underwent re-excision. Residual tumour was found in the re-excision specimen in 28/50 patients (56.0%) of the group A and in 7/15 patients (46.7%) of the group B.

Separate CM excision strongly decreases the rate of re-operation for involved margin. However, the finding of various combinations of LM and CM status and the evidence that CM excision does not improve the positive predictive value of margin involvement suggest prudent conclusions. Only long term follow up of patients treated according to the CM status can exclude that the reduced rate of re-operations allowed by this procedure would expose to an increased risk of local recurrence.