The lateral decubitus breast boost: description, rationale, and efficacy.
OBJECTIVE
To describe and evaluate the modified lateral decubitus boost, a breast irradiation technique. Patients are repositioned and resimulated for electron boost to minimize the necessary depth for the electron beam and optimize target volume coverage.


METHODS
A total of 2,606 patients were treated with post-lumpectomy radiation at our institution between January 1, 2000, and February 1, 2008. Of these, 231 patients underwent resimulation in the lateral decubitus position with electron boost. Distance from skin to the maximal depth of target volume was measured in both the original and boost plans. Age, body mass index (BMI), boost electron energy, and skin reaction were evaluated.


RESULTS
Resimulation in the lateral decubitus position reduced the distance from skin to maximal target volume depth in all patients. Average depth reduction by repositioning was 2.12 cm, allowing for an average electron energy reduction of approximately 7 MeV. Mean skin entrance dose was reduced from about 90% to about 85% (p < 0.001). Only 14 patients (6%) experienced moist desquamation in the boost field at the end of treatment. Average BMI of these patients was 30.4 (range, 17.8-50.7). BMI greater than 30 was associated with more depth reduction by repositioning and increased risk of moist desquamation.


CONCLUSIONS
The lateral decubitus position allows for a decrease in the distance from the skin to the target volume depth, improving electron coverage of the tumor bed while reducing skin entrance dose. This is a well-tolerated regimen for a patient population with a high BMI or deep tumor location.
Ludwig
Michelle S
MS
Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA. mludwig@mdanderson.org
McNeese
Marsha D
MD
Buchholz
Thomas A
TA
Perkins
George H
GH
Strom
Eric A
EA
D000367:Age Factors; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D004583:Electrons / Q000627:therapeutic use; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D056888:Patient Positioning / Q000379:methods*; D011832:Radiation Injuries / Q000473:pathology* / Q000517:prevention & control; D011859:Radiography; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012867:Skin / Q000528:radiation effects*