The rationale for post-mastectomy radiation(PMRT) is to decrease the chance that cells left behind will regrow in the remaining skin or tissue after mastectomy. Although this is not a common complication, when it ocurrs, it can be devastating. Although the concern is understandable, post-mastectomy radiation tends to be overused in theUSA. For example, women who have stage I or II disease with spread to no more than three lymph nodes and who did not undergo radiation therapy, have the overall growth rate in the same general area rate of just 2.3% at 10 years. A 2005 meta-analysis looked at randomized trials conducted between 1964 and 1984. The analysis determined that post-mastectomy radiation in these women resulted not only in about a 66% reduction in locoregional recurrence compared with no radiation, but also about a 5% survival advantage. However, the overall recurrence rate in those studies ranged from 20% to 25%, much higher than observed in the present.
Certainly, locoregional PMRT is recommended for women with an advanced primary tumour (tumour size 5 cm or greater, or tumor invasion of the skin, pectoral muscle or chest wall) or with 4 or more positive axillary lymph nodes, because the risk of regrwth is significant. However, the role of PMRT in women with 1 to 3 positive axillary lymph nodes is unclear. Locoregional PMRT is generally not recommended for women who have tumors that are less than 5 cm in diameter and who have negative axillary nodes. Other patient, tumor and treatment characteristics, including age, histologic grade, iinvasion of lymph and neural stands, hormone receptor status, number of axillary nodes removed, extension of cancer out of the capsule of lymph nodes in the armpit extension and surgical margin status, may affect loco-regional control, but their use in specifying additional indications for PMRT is currently unclear.
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