ThP1.8 - Margin re-excision after Wise pattern or Vertical scar therapeutic mammoplasty for early breast cancer - a single institution 4-year review

Abstract Introduction Therapeutic mammoplasty is a technique which facilitates large volume cancer excisions whilst maintaining breast cosmesis in patients with breast cancer. The aim of this audit was to evaluate the rates of positive margins and cancer recurrence in this cohort and determine any risk factors for requiring margin re-excision. Methods All patients undergoing therapeutic mammoplasty using a Wise-pattern or vertical scar technique for the treatment of breast cancer over a 4-year period (November 2019- October 2023) were included. Data was collected on patient demographics, tumour characteristics, re-excision rates and cancer recurrence. Results Of a total of 61 patients who underwent therapeutic mammoplasty, 10 (16.4%) required margin re-excision. DCIS alone was present at the margin in the majority (70%). Re-excision specimens contained further cancer in 4/10, of which 2 had clear new margins, one required further re-excision and one underwent completion mastectomy. Half of those who required re-excision had a cancer that was either mammographically occult or was non-concordant with the pre-operative imaging on final histology in terms of extent and/or focality. There was one case only of in-breast recurrence, in a patient who had not previously required margin re-excision. Conclusions Therapeutic mammoplasty is an oncologically safe technique and in the vast majority of patients the breast can continue to be preserved even when margins are close or involved. Patients undergoing therapeutic mammoplasty who have mammographically occult tumours may be at higher risk of margin re-excision even with the addition of MRI imaging.