The importance of the resection margin in conservative surgery for breast cancer

Eradication of breast cancer by wide local excision alone is not possible unless the clinical margins of excision exceeds 5 cm or a segmental mastectomy is performed, though recurrences may still occur after a segmental mastectomy. With inadequate excision radiotherapy to the breast is essential, but will not prevent local recurrence. In a prospective trial (1981 to 1990) to assess the value of radiotherapy to the breast when adjuvant therapy was administered, 418 patients treated by wide local excision and adjuvant chemotherapy (tamoxifen if oestrogen receptor-positive and CMF chemotherapy if oestrogen receptor-negative) were randomized to have loco-regional radiotherapy to the breast or not. At a minimum 5-year follow-up, the local recurrence rate in patients receiving radiotherapy was 13% compared to 35% in those not so treated. Local recurrence was strictly related to microscopic clearance in millimetres irrespective of clinical wide local excision, nodal, or menopausal status. Where, histologically, local excision was incomplete and patients received radiotherapy, the local recurrence rate was 17%. The criteria for wide local excision need to be strictly defined and histologically proven if post-operative radiotherapy is to achieve its effective function, that is the prevention of local recurrence. Radiotherapy cannot compensate for inadequate surgery.