To evaluate whole breast 3D-conformal radiotherapy (RT) delivered in the lateral decubitus position (isocentric lateral decubitus [ILD]) and to report the acute toxicity of a series of consecutive patients treated with ILD.
Materials and methods
From January to December 2010, 56 consecutive patients with large breasts and early-stage breast cancer treated by breast conserving surgery underwent 3D-conformal whole breast RT in the lateral decubitus position. A dose of 50 Gy in 25 fractions via two opposed isocentric beams was prescribed to whole breast, with or without a 16 Gy photon tumor bed boost. Dosimetry of all patients was reviewed, and the acute toxicity of treatment, evaluated weekly using the NCI CTC v3.0 scale, was analyzed.
Results
Median age was 57 years (range: 33–71). 85% of patients had a breast circumference of at least 95 cm and 80% had at least a C cup size. Average breast volume was 991 cm3 (range: 225–2791 cm3). Median dose to the breast was 50 Gy, while median dose to the tumor bed was 16 Gy. Grade 1, 2 and 3 dermatitis developed in 37.5%, 58.9% and 1.8% of patients, respectively. From a dosimetric point of view, doses to the ipsilateral lung were extremely low: average V1Gy, V2Gy and V5Gy were 26.6%, 9.3% and 0.7%, respectively. Average mean lung dose was 0.96 Gy. For the 26 patients with left-sided tumors, heart doses were also extremely low: average V1Gy, V2Gy and V5Gy were 58.8%, 14.2% and 0.7%, respectively. Average mean heart dose was 1.35 Gy.
Conclusion
Whole breast radiotherapy in the lateral decubitus position for patients with large breasts and early-stage breast cancer provides an excellent dosimetric profile, with low doses to the heart and ipsilateral lung. It is also very well tolerated, with a good acute toxicity profile.
