EL ADIOTHERAPY & ONCOLOGY ELSEVIER Radiotherapy and Oncology 42 (1997) 17-24 Electron arc irradiation of the postmastectomy chest wall: clinical results’ David K. Gaffney”‘“, Janalyn Prowsb, Dennis D. LeavitP, Marlene J. Egger”, John G. Morgan”, J. Robert Stewart” ‘Department of Radiation Oncology, University of Utah Health Sciences Center, 50 N. Medical Dr., Salt Lake City, Utah 84132, USA bMidwest Radiation Oncology Clinic, Methodist Hospital, Omaha, Nebraska, USA ‘Department of Family and Preventive Medicine, University of Utah Health Sciences Center, 50 N. Medical Dr., Salt Lake City, Utah 84132, USA Received 21 March 1996; revised 6 September 1996;accepted 21 October 1996 Abstract Background and purpose: Since 1980 electron arc irradiation of the postmastectomy chest wall has been the preferred technique for patients with advanced breast cancer at our institution. Here we report the results of this technique in 140 consecutive patients treated from 1980 to 1993. Materials and Methods: Thoracic computerized tomography was used to determine internal mammary lymph node depth and chest wall thickness, and for computerized dosimehy calculations. Total doses of 45-50 Gy in 5 to 5 l/2 weeks were delivered to the chest wall and internal mammary lymph nodes via electron arc and, in most cases, supraclavicular and axillary nodes were treated with a matching photon field. Patients were assessed for acute and late radiation changes, local and distant control of disease, and survival. Patients had a minimum follow-up of 1 year after completion of radiation treatment, and a mean follow up interval of 49 months and a median of 33 months. All patients had advanced disease: T stages 1, 2, 3, and 4 represented 21%, 39%, 21% and 19% of the study population, with a mean number of positive axillary lymph nodes of 6.5 (range, O-29). Analysis was performed according to adjuvant status (no residual disease, n=90), residual disease (positive margin, n= 15, and primary radiation, n=2), or recurrent disease (n=33). Results: Acute radiation reactions weregenerally mild and selflimiting. A total of 26%of patients developed moistdesquamation, and 32% hadbriskerythema. Actuarial 5 yearlocal-regional control, freedom from distant failure, andcause-specific survival was 91%, 64%, and 75% in the adjuvantgroup; 84%, 50%, and 53% in the residual disease group; and 63%, 34%, and 32% in the recurrent disease group, respectively. In univariateCox regressions, the number of positive lymph nodes was predictivefor local failure in the adjuvant group (P=O.O37). Chronic complications were minimal with 11% of patients having arm edema, 17% hyperpigmentation, and 13% telangectasia formation. Conclusion: Thesedata demonstrate that local-regional control with electron arc therapy of the postmastectomy chest wall is comparable to photontechniques. Acute radiation reactions arewell tolerated and mostly of minorextent.A previous reportdemonstrated a significantreduction in the dose-volume relationship of the lung using the electron arc compared with two photon techniques. Consequently, with careful attention to treatment planning anddosimetry, electronarc therapyof the postmastectomy chest wall is safe andeffective. The radiation dose to heartandlung is minimized without compromise on local control. 0 1997, ElsevierScience Ireland Ltd. All rights reserved Keywords: Breast cancer; Postmastectomy; Chest wall; Electronarc; Rotational therapy 1. Introduction Irradiation of the post-mastectomy chest wall and re- gional lymphatics in breast cancer patients is an important component for local control in multidisciplinary manage- *Corresponding author. ‘This report was presented at ASTRO October,1995 in Miami, Florida. 0167-8140/97/$17.00 0 1997 Elsevier Science Ireland Ltd. All rights resen PII SO167-8140~96~01860-9 ment, although the impact on overall survival is contenti- ous. Two modern trials suggest a survival benefit for post-operative irradiation to the chest wall and regional lymphatics [29,31]. A recent meta-analysis has demon- strated a trend toward an increase in survival for those patients who underwent post-operative irradiation, along with a trend toward increasing benefit with more recent trials examining post-operative radiation [7]. In node positive patients, one report suggests that post-operative led