Postmastectomy chest wall irradiation with electron beam technique – 10-year single-center retrospective analysis

Abstract

BACKGROUND: Postmastectomy radiation therapy (PMRT) is delivered routinely with photon techniques, chest wall radiation with electron techniques have the advantage of reduced deeper tissue doses and can be tried in suitably selected cases. This study is to retrospectively evaluate the locoregional control, toxicity, disease-free survival (DFS), and overall survival of patients treated with postmastectomy chest wall electron radiation at a single center. MATERIALS AND METHODS: The data of 450 patients who received PMRT with electron therapy from 2004 to 2014 were analyzed. Patients were treated with three-dimensional (3D) conformal radiation therapy with 6–8 MeV electrons to chest wall and 6 MV photons to supraclavicular fossa and medial axilla. Data collection was done from hospital medical records and analyzed with IBM SPSS 20.0. The results are given in mean ± standard deviation for continuous variables or as percentage for categorical variables. Kaplan–Meier survival analysis and log-rank tests were used. P < 0.05 was considered as statistically significant. RESULTS: Patients' median age was 64 years (range: 24–74 years). Early stage accounted for 108 (24%) patients, 306 (68%) were advanced stage, and for 36 (8%) patients, stage was unknown. Of these, 174 (38.7%) patients were offered hypofractionated schedule and 276 (61.3%) with conventional fractionation. No Grade 3–4 skin reactions were reported over the irradiated area on treatment completion. Twenty-three (5.1%) patients had chest wall recurrence and 33 (7.3%) patients developed locoregional recurrence. Overall recurrence including systemic metastasis was 127 (28.2%). Long-term data did not show any cardiac or pulmonary mortality documented as radiation related. The median follow-up of our group was 67 months (6–173 months). DFS at 5 and 10 years was 81.4% and 79.5%, respectively. OS at 5 and 10 years was 85.2% and 79.7%, respectively. CONCLUSION: PMRT with chest wall enface electron is feasible, and the advantage of electron field is better sparing of deeper structures, especially cardia in left-sided postmastectomy irradiation, thus more complex techniques such as Intensity Modulated Radiation Treatment (IMRT) and respiratory gating can be reserved for patients with more complicated anatomy where routine 3DCRT technique is unacceptable in terms target coverage and critical normal tissue sparing.

Keywords

• chest wall
• electron technique
• postmastectomy radiation therapy