Use of a correlation analysis model in the optimization of intensity-modulated radiotherapy of prostate cancer.

The aim of the present study was to develop a statistical model-based method for the optimization of intensity-modulated radiotherapy (IMRT). A prostate cancer IMRT plan was redesigned while retaining the same beam orientation and prescribed dose as the regular plan. A series of dosimetric parameters were generated, and a 4-step protocol was performed to analyze the data: i) The tumor control probability of the target was ensured by setting a number of strict constraint parameters so that much of the target was covered by the 95% isodose line; ii) the parameters for optimization [weight ratio, equivalent characteristic parameter a and maximum equivalent uniform dose of the organ at risk (OAR)] were adjusted; iii) the overall optimization space (OOS) was determined via analysis of the dose-parameter tables based on the correlation factor (CF) and optimization efficiency factor analysis; iv) the OOS in the Pinnacle V7.6 treatment planning system with IMRT function was transposed. A selected optimization phenomenon existed when different optimization methods were used to optimize dose distribution to the targets and OARs, which demonstrates a wide variation in the CFs between the percentage of planning target volume receiving 95% of the prescribed dose and the maximum dose of the bladder, rectum and femur. The OOS used to optimize the randomly selected plan exhibited relatively high efficiency, with benefits for the optimization of IMRT plans. For patients with prostate cancer who require complex IMRT plan optimization, the obtained OOS from the two core analysis techniques is likely to have relatively high efficiency in achieving an optimized plan. These results suggest that the correlation analysis model is a novel method for the optimization of IMRT for prostate cancer.