Purpose: To evaluate the impact of wide-tangent fields including the internal mammary chain during deep inspiration breath-hold (DIBH) radiotherapy in patients with left-sided breast cancer on cardiac exposure.
Patients and methods: Eleven patients with left-sided breast cancer were irradiated postoperatively and underwent CT scans during free breathing and DIBH. For scientific interest only, treatment plans were calculated consisting of wide tangents including the ipsilateral mammary lymph nodes using both, the free breathing and respiratory-controlled CT scan. The resulting dose-volume histograms were compared for irradiated volumes and doses to organs at risk.
Results: The mean patient age was 51 years (range: 37-65 years). Radiotherapy using wide tangents with DIBH as compared to free breathing led to a significantly lower cardiac exposure. Mean irradiated heart volumes (> or = 20 Gy) were 14 cm(3) (range: 0-51.3 cm(3)) versus 35 cm(3) (range: 2.1-78.7 cm(3); p = 0.01). For eight patients, DIBH reduced irradiated relative lung volume, while in three patients, the lung volume slightly increased.
Conclusion: Radiation exposure of organs at risk can significantly be reduced for breast cancer patients using the DIBH technique. If radiotherapy of the internal mammary lymph nodes is considered necessary, DIBH may be the preferable technique.