Postmastectomy Chest Wall Reirradiation With Proton Therapy for Breast Cancer


      To assess toxicity outcomes in postmastectomy breast cancer patients receiving chest wall (CW) reirradiation (reRT) with proton therapy (PT).


      From 2012-2016, 22 breast cancer patients received postmastectomy (CW) reRT with PT at a single institution. Patients were included if they had a history of prior thoracic radiotherapy (RT) and had indications for reRT for a primary or recurrent breast cancer diagnosis. 21 patients received treatment to the CW plus comprehensive lymph nodes (LN) and 1 patient received PT to the CW and internal mammary LN only. Indications for inclusion of LN included LN positive disease (N=10), inflammatory breast cancer at time of recurrence (N=2) or lack of pathological assessment of the axilla (N=10). 10 patients had reconstruction prior to initiation of PT reRT. Initial RT characteristics include the following: 40 Gy to a mantle field for Hodgkin Lymphoma (N=1), RT to the intact breast for initial early stage breast cancer diagnosis (N=18), RT to the breast or CW plus the supraclavicular fossa for LN positive disease at initial diagnosis (N=2) and partial breast RT (N=1). Median initial RT dose was 60 Gy (10-70 Gy). Median time interval between courses of RT was 12 years (3-36 years). ReRT was performed with PT using a uniform scanning (N=19) or pencil beam scanning (N=3) technique. Median PT dose was 50.51 (45.1-76.31) GyE. 2 patients had gross disease due to dermal lymphatic progression at PT initiation. Toxicity was assessed prospectively per CTCAE v. 4.0 at baseline, weekly during PT, 2 weeks and 4 weeks following PT and then every 6 months. Cosmesis at last follow-up was retrospectively assessed and graded according to the Harvard/NSABP/RTOG grading scale.


      Median follow-up was 15 months (3-39 months). At the time of last follow-up, all patients had locoregional control. One patient developed distant metastases 17 months following PT. Acute skin toxicity occurred in all patients; grade 1 (N=5), grade 2 (N=15) and grade 3 (N=2). Acute grade 2 esophagitis occurred in 7 patients. Acute grade 2 CW pain occurred in 10 patients; grade 3 occurred in 1 patient. At the time of last follow-up, 3 patients had experienced rib fracture. Pneumonitis requiring steroid treatment occurred in 1 woman 7 months post-PT. 3 women had grade 2 lymphedema at last follow-up. 3 women experienced delayed wound healing following surgical intervention in the reRT treatment field; one of which was treated with hyperbaric oxygen. Cosmetic outcomes at the time of last follow-up were grade 1 (N=1), grade 2 (N=9) grade 3 (N=11) and grade 4 (N=1). All patients experienced CW fibrosis; grade 1 (N=14), grade 2 (N=6) and grade 3 (N=2). At the time of last follow-up, Grade 1 CW pain was experienced in 13 patients.


      ReRT with PT in breast cancer patients appears to have acceptable toxicity. Following reRT to the CW surgical intervention in the treatment field should be avoided. Longer follow-up is needed.


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