In the updated guideline,1 we mentioned the data from the European Organization for Research and Treatment of Cancer trial, in which survival was worse for patients for whom mastectomy was originally planned but in whom preoperative chemotherapy downstaged the tumour, allowing for breast-conserving surgery (BCS).2 We also indicated that in the National Surgical Adjuvant Breast Project B-18 trial, there was a trend (among patients who underwent preoperative chemotherapy) toward a higher rate of local breast cancer recurrence in those for whom mastectomy was planned but who instead underwent BCS.3 Both of these subgroup analyses were post hoc (i.e., not specified a priori), and they did not involve comparisons between randomized groups; hence, the results should be considered hypothesis-generating in nature, although they do represent food for thought. The tone of our recommendation was therefore rather tentative (as it should be).
There are some situations (e.g., a large breast or a large primary tumour that is not fixed) in which preoperative chemotherapy may shrink the tumour and allow for BCS. Conversely, when mastectomy is planned for a large tumour, it is often in the context of locally advanced breast cancer, and we do not recommend BCS in this situation. This topic will be the subject of a future guideline of the Steering Committee on Clinical Practice Guidelines for the Care and Treatment of Breast Cancer.
Mark Levine Professor Department of Clinical Epidemiology and Biostatistics McMaster University Hamilton, Ont.