Residual disease after re-excision for tumour-positive surgical margins in both ductal carcinoma in situ and invasive carcinoma of the breast: The effect of time

Background and Objectives: To assess the effect of time on finding residual breast cancer in re-excision specimens after non-radical breast-conserving surgery for both DCIS and invasive breast carcinoma. Methods: 315 breast-conserving surgical procedures with tumour-positive margins were retrospectively reviewed. The significance of association between the presence of finding residual tumour in the re-excision specimen and mean time interval was calculated with Student's t-test. A multivariate logistic regression model was used to assess the independent relative risk of time on presence of residual tumour. Results: Residual tumour was found in 240 (76.2%) of the re-excision specimens. For primary invasive carcinomas time was a risk-reducing factor for finding residual disease (OR 0.89, 95% CI 0.82-0.98, P = 0.01). If invasive carcinoma was transected, the absence of residual disease was significantly related with a longer mean time interval (OR 0.98, 95% CI 0.95-0.99, P = 0.04). Conclusions: An increased time interval between primary surgery and re-excision for turnour-positive surgical margins for invasive carcinoma is associated with a decreased incidence of finding residual tumour. This could be explained by inflammatory responses after surgical trauma. For DCIS there was no influence of time on finding residual tumour, which could be explained by a more protective microenvironment of DCIS or re-growth of surviving malignant cells.