Helical Tomotherapy (HT) for Postmastectomy Radiation Therapy (PMRT) Treatment after Implant Breast Reconstruction

Abstract

To report our experience of using Helical Tomotherapy (HT) for postmastectomy radiation therapy (PMRT) treatment after immediate breast reconstruction (IBR) with implant. A total of 173 patients who underwent modified radical mastectomy for invasive breast cancer with or without IBR with retropectoral implants, received PMRT with HT at our institution between 2013 and 2015. PMRT with chest wall, supraclavicular and internal mammary lymph nodes irradiation was delivered to a dose of 50 Gy/25 fx. In the IBR group (n=87), the Planning Target Volume of chest wall (PTVcw) included subcutaneous tissue and pectoralis muscle plus margin, excluding the posterior side of the implant and the ribs, considering this volume as the main site of local recurrence of breast cancer. The treatment plans and outcomes were compared with those of 86 patients treated for PMRT by HT without IBR (control group). CW and Internal Mammary Nodes (IMN) coverage and doses to the organs at risk were compared between groups. Clinical outcomes were also assessed, including rate of reconstruction failure and prosthesis exchange. Coverage of chest wall was significantly improved in the IBR group in comparison with the group without reconstruction (V95% = 95.1 % versus 92.0 %; p<0.0001). There was no significant difference in the IMN coverage between the two groups (V95% = 93.1 % versus 92.4 %; p=0.3467). Irradiated volume of the ipsilateral lung was significantly decreased in the IBR group with a median V20Gy of 11.6 % compared with 15.2 % in the control group (p<0.0001). Similarly, the median V15Gy of the heart was significantly lower in the IBR group than in the control group (1.7 vs 2.5 %; p=0.0280). All neighboring organs received doses that remained well below tolerance levels. The treatment tolerance was acceptable without any definitive interruption and no grade 3 or 4 toxicity. The rate of reconstruction failure was 13,8% (n=12) and 33,3% of patient had implant replacement. After a median follow-up of 39.8 months, the locoregional recurrence rate was low in both groups (only 1 local and 3 regional relapses among the 87 patients in IBR group). Adequate and safe PMRT with Helical Tomotherapy can be offered to patients treated by mastectomy and IBR with retropectoral implants, with excellent dosimetric results and acceptable clinical outcomes.