Comparison of three different mediastinal radiotherapy techniques in female patients: Impact on heart sparing and dose to the breasts.
BACKGROUND AND PURPOSE: To study different radiotherapy techniques for female patients with mediastinal target volumes. Especially in highly curable diseases such as lymphoma, long-term survivors might develop late cardiac damage and radiation-induced second cancer. PATIENTS AND METHODS: Planning CT scans were obtained in eight cases. We contoured the clinical target volume (three different scenarios with or without lower mediastinum and hili) and organs at risk and compared standard 6MV ap-pa opposed fields to a 3D conformal 4-field technique and a 7-field step-and-shoot IMRT technique and evaluated DVHs for each structure. The planning system was BrainSCAN 5.21 (BrainLAB, Heimstetten, Germany). RESULTS: Target volume coverage did not improve significantly with 4-field or IMRT techniques. However, IMRT resulted in better dose reduction to the heart than the other techniques. The median heart dose (intermediately sized target volume) was 98% (95-100) with ap-pa fields, 56% (52-79) with the 4-field technique, and 39% (36-65) with IMRT, for example (p<0.05). Better heart sparing was achieved at all dose levels down to the 15% isodose. The median maximum dose to the breasts was lowest with IMRT. The breast volume receiving low doses (15% or less), however, was highest with IMRT. There was also a disadvantage in mean lung dose. CONCLUSIONS: IMRT might result in a reduced cardiac complication risk. In younger females, however, this advantage might be offset by the risk of breast cancer. The best technique for a given patient depends on age, comorbidity, and the individual risk estimates for breast cancer and cardiac morbidity, respectively.