Postmastectomy CT-based electron beam radiotherapy: dosimetry, efficacy, and toxicity in 118 patients.
OBJECTIVE
To evaluate the technique, dosimetry, acute and late toxicity, local control (LC), and overall survival (OS) with the use of computed tomography (CT)-based postmastectomy electron beam therapy (PMEBT) in high-risk patients.


METHODS
From 1990 to 2000, 118 patients with pathologic stage I-IIIB breast cancer underwent PMEBT of the chest wall (CW) (n = 3), CW and supraclavicular fossa (SCV) (n = 63), CW, SCV, and internal mammary lymph nodes (IMN) (n = 51), and SCV+IMN (n = 1). Radiation therapy was delivered with an en face electron beam with a custom cutout. Treatment plans were all CT-based. The plans of 16 patients were retrospectively reviewed to analyze dosimetry data. A retrospective chart review was conducted to assess acute and late complications, LC, and OS.


RESULTS
At a median follow-up of 43 months, 5-year LC and OS were 91% and 61%, respectively. Sixty-one patients developed acute grade 3-4 skin toxicity, necessitating treatment breaks in 33 patients. Fifteen patients experienced a worsening of lymphedema, and 2 patients developed cardiac injury thought to be unrelated to radiotherapy. No patients developed symptomatic pneumonitis. Dosimetric analysis revealed heart and lung normal tissue complication probabilities of zero. Analysis of other clinically relevant dosimetric parameters revealed PMEBT to be comparable to previously reported techniques.


CONCLUSIONS
Postmastectomy electron beam therapy is an effective way to deliver radiation to the postmastectomy chest wall and adjacent nodal sites. It offers acceptable acute and late toxicities and a high degree of local control given the high-risk population to which it is offered.
Spierer
Marnee M
MM
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA. spiererm@mskcc.org
Hong
Linda X
LX
Wagman
Raquel T
RT
Katz
Matthew S
MS
Spierer
Rebecca L
RL
McCormick
Beryl
B
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery*; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D015182:Lymphatic Irradiation; D008408:Mastectomy; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology; D011879:Radiotherapy Dosage; D012867:Skin / Q000528:radiation effects; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed