Initial clinical experience using respiratory gated radiation therapy
for left breast cancer treatment
Zhang S, Salehpour MR, Balter P, Buchholz TA, Strom EA, Woodward WA, Gillin M
University of Texas MD Anderson Cancer Center
USA
Purpose: To evaluate the heart and lung sparing with deep inspiration breath-hold respiratory gating radiation treatment for left breast cancer.
Method and Materials: Patients were selected for breath-hold (BH) gating study after heart protrusion into the treatment field during the free-breath (FB) CT scan. The Varian Real-time Position Management (RPM) system was used to monitor the patient respiratory motion during the BH CT scan and the gating treatment. Both the FB and BH CT dataset were co-registered into the treatment planning system. The treatment plans were optimized with tangent fields using field-in-filed technique. The On-Board-Imaging (OBI) system was used to assure the same lung volume in the gating treatment as in the BH CT simulation.
Results: The lung volume was significantly increased due to deep inspiration, up to 2 times volume as in the normal free-breath. However the BH lung volume in the treatment fields was comparable to the FB lung volume, and the relative lung volume received more than 50% of the prescribed target dose in the BH gating treatment was reduced to the order of 10-20%. For all patients deep inspiration BH was able to move the heart completely out of the treatment fields. The heart volume received more than 10 Gy dose was reduced from 5-10% in the FB plan to less than 1% in the BH gating treatment.
Conclusions: Remarkable potential is shown for deep inspiration breath-hold gating radiotherapy to reduce the risk of both cardiac and pulmonary toxicity for the left breast irradiation.