Abstract
Background: Several Phase III randomized trials have demonstrated improved local control and survival for post-mastectomy radiotherapy in patients with high-risk pathologic features. Close or involved surgical margins were not included as high-risk in these protocols, but have been associated with increased risk of local failure; however, the impact of a boost dose following chestwall radiotherapy in this setting remains to be determined. Methods: Retrospective single-institution outcomes analysis for patients with close or involved surgical margins treated with post-operative radiotherapy is followed by a boost. Results: Between 2003 and 2011, 34 patients were identified for inclusion in the present study. The median chestwall dose was 5040 cGy (range 5000 - 5040) and median boost dose was 1080 cGy (900 - 1620). At a median follow-up of 38.4 months (10.2 - 115.6; with 29% more than 5 years), 28 patients were alive without evidence of recurrence, 3 were alive with recurrent disease (1 chestwall), and 3 had died (none with recurrent disease). The 3-year local control, disease-free survival, and overall survivals were 96.9%, 93.9%, and 93.1%, respectively. Conclusion: Chestwall radiotherapy plus boost results in low risk of early locoregional recurrence for women with close or involved surgical margin(s) at mastectomy. Further investigation of PMRT with or without boost in this setting is warranted.
Highlights
Randomized trials have demonstrated that post-mastectomy radiation therapy (PMRT) reduces the risk of loco-regional recurrence (LRR) by 50% - 65% for women with high-risk features at mastectomy [1,2,3,4]
No boost was employed in the setting of close or involved surgical margins, and for the overall study populations, the LRR was 5% - 10% for irradiated patients
No cases of isolated in situ carcinoma were identified; all had invasive carcinoma, and lymphovascular invasion was identified in 23 patients
Summary
Randomized trials have demonstrated that post-mastectomy radiation therapy (PMRT) reduces the risk of loco-regional recurrence (LRR) by 50% - 65% for women with high-risk features at mastectomy [1,2,3,4] These highrisk pathologic features included invasion of the skin or pectoralis fascia, tumor size >5 cm, and/or lymph node involvement [2,3,4]. While surgical margin status was not recorded, analysis of patients with skin and/ or deep fascia invasion (subsets with anticipated high likelihood of margin involvement) demonstrated significant reduction of LRR at 10 years (40% vs 7%) [3,4] These trials employed standardized regimens (48 - 50 Gy over 4 - 5 weeks via electrons or 37.5 Gy over 3 - 4 weeks via tangents in the European and Canadian protocols, respectively), with mandatory comprehensive nodal irradiation (including both axillary and internal mammary nodal targets) [2,4]. Further investigation of PMRT with or without boost in this setting is warranted
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