SU-E-T-428: Class Solution for Prostate High Dose Rate Brachytherapy with Inverse Planning Simulated Annealing

To develop and validate a class solution for inverse planning simulated annealing (IPSA) with CT based prostate high dose rate brachytherapy (HDR).

Between November 2008 and November 2011, our institution treated 40 prostate cancer patients with HDR in 7 Gy fractions followed by external beam radiotherapy. The HDR treatments were planned with Nucletron Oncentra using manual graphical optimization (GO). Plans were optimized to the following clinical goals: = 95% of prostate volume received 7 Gy, < 1 cc of rectum received 5.6 Gy, < 0.1 cc of rectum received 6.3 Gy, and < 0.01 cc of urethra received 8.75 Gy. New plans were manually customized using IPSA (MC-IPSA) for each patient to match prostate coverage by the prescription dose to within ± 1% of the GO plans while meeting the rectal and urethral dose constraints. An IPSA class solution (CS-IPSA) was created from the mean MC-IPSA parameters. New plans were developed for each of these 40 patients using only CS-IPSA with no further optimization. Additionally, plans were created on an independent dataset of 30 different patients using only CS-IPSA with no further optimization.

Plans were optimized in about 30 minutes using GO, MC-IPSA took an average of 14.1 ± 6.5 minutes, and CS-IPSA optimizationwas < 1 minute. There was no significant difference (p > 0.05) among the optimization methods for all clinical goals over the 40 CS-IPSA source patients. There was no significant difference (p > 0.05) between the source and the independent datasets for all clinical goals when using CS-IPSA with no further optimization.

A prostate HDR IPSA class solution was developed and validated on a source and an independent dataset. The IPSA class solution yields plans comparable to custom manual IPSA and graphical optimization while saving considerable time.