Author(s): Lawrence JA, Forrest LJ, Turek MM, Miller PE, Mackie TR, Jaradat HA, Vail DM, Dubielzig RR, Chappell R, Mehta MP. Proof of principle of ocular sparing in dogs with sinonasal tumors treated with intensity-modulated radiation therapy. Vet Radiol Ultrasound. 2010 Sep-Oct;51(5):561-70. PMID 20973393
Journal: Veterinary Radiology & Ultrasound : The Official Journal Of The American College Of Veterinary Radiology And The International Veterinary Radiology Association, Volume 51, Issue 5, 2010
Intensity-modulated radiation therapy (IMRT) allows optimization of radiation dose delivery to complex tumor volumes with rapid dose drop-off to surrounding normal tissues. A prospective study was performed to evaluate the concept of conformal avoidance using IMRT in canine sinonasal cancer. The potential of IMRT to improve clinical outcome with respect to acute and late ocular toxicity was evaluated. Thirty-one dogs with sinonasal cancer were treated definitively with IMRT using helical tomotherapy and/or dynamic multileaf collimator (DMLC) delivery. Ocular toxicity was evaluated prospectively and compared with a comparable group of historical controls treated with conventional two-dimensional radiotherapy (2D-RT) techniques. Treatment plans were devised for each dog using helical tomotherapy and DMLC that achieved the target dose to the planning treatment volume and limited critical normal tissues to the prescribed dose-volume constraints. Overall acute and late toxicities were limited and minor, detectable by an experienced observer. This was in contrast to the profound ocular morbidity observed in the historical control group treated with 2D-RT. Overall median survival for IMRT-treated and 2D-treated dogs was 420 and 411 days, respectively. Compared with conventional techniques, IMRT reduced dose delivered to eyes and resulted in bilateral ocular sparing in the dogs reported herein. These data provide proof-of-principle that conformal avoidance radiotherapy can be delivered through high conformity IMRT, resulting in decreased normal tissue toxicity as compared with historical controls treated with 2D-RT.