Active breathing control (ABC) for Hodgkin's disease: reduction in normal tissue irradiation with deep inspiration and implications for treatment.

PURPOSE: Active breathing control (ABC) temporarily immobilizes breathing. This may allow a reduction in treatment margins. This planning study assesses normal tissue irradiation and reproducibility using ABC for Hodgkin's disease. METHODS AND MATERIALS: Five patients underwent CT scans using ABC obtained at the end of normal inspiration (NI), normal expiration (NE), and deep inspiration (DI). DI scans were repeated within the same session and 1-2 weeks later. To simulate mantle radiotherapy, a CTV1 was contoured encompassing the supraclavicular region, mediastinum, hila, and part of the heart. CTV2 was the same as CTV1 but included the whole heart. CTV3 encompassed the spleen and para-aortic lymph nodes. The planning target volume (PTV) was defined as CTV + 9 mm. PTVs were determined at NI, NE, and DI. A composite PTV (comp-PTV) based on the range of NI and NE PTVs was determined to represent the margin necessary for free breathing. Lung dose-mass histograms (DMH) for PTV1 and PTV2 and cardiac dose-volume histograms (DVH) for PTV3 were compared at the three different respiratory phases.
RESULTS: ABC was well-tolerated by all patients. DI breath-holds ranged from 34 to 45 s. DMHs determined for PTV1 revealed a median reduction in lung mass irradiated at DI of 12% (range, 9-24%; n = 5) compared with simulated free-breathing. PTV2 comparisons also showed a median reduction of 12% lung mass irradiated (range, 8-28%; n = 5). PTV3 analyses revealed the mean volume of heart irradiated decreased from 26% to 5% with deep inspiration (n = 5). Lung volume comparisons between intrasession and intersession DI studies revealed mean variations of 4%.
CONCLUSION: ABC is well tolerated and reproducible. Radiotherapy delivered at deep inspiration with ABC may decrease normal tissue irradiation in Hodgkin's disease patients.