Effect of modern, high‑quality prostate intensity‑modulated radiation therapy on outcome: Evidence from a community radiation oncology program

Abstract

Abstract.Radiation technique for prostate cancer has continuously evolved over the past several decades. The aim of the present study was to describe the effects of implementing modern prostate intensity-modulated radiation therapy (M-IMRT) on dosimetry and outcome. Between January 2010 and April 2012, 48 consecutive patients were treated with conventional prostate IMRT (C-IMRT) to a dose of 81 Gy. Between May 2012 and April 2015, 50 consecutive patients were treated with M-IMRT to the entire prostate to a dose of 75.6-79.2 Gy, while using prostate magnetic resonance imaging fusion, dose-volume constraints prioritizing normal tissue avoidance above planning target volume coverage, and boosting any dominant intraprostatic masses to 79.2-81 Gy. Rectal Dmax, V75, V60, V65 and V50, bladder Dmax, V75, V70 and V65, and acute and late toxicities were compared between the C-IMRT and M-IMRT groups. The median follow-up for the C-IMRT and M-IMRT groups was 61 vs. 26 months, respectively (P<0.001). M-IMRT resulted in a significant reduction in median rectal Dmax, rectal V75, rectal V70, rectal V65, bladder Dmax, bladder V75, bladder V70 and bladder V65 (P<0.01 for all). There was no significant difference in rectal V50. The 2-year rate of late grade ≥2 rectal bleeding was 13% with C-IMRT vs. 3% with M-IMRT (P=0.03). The 2-year rate of late grade ≥2 genitourinary toxicity was 11% for C-IMRT vs. 5% for M-IMRT (P= 0.21). There were no significant differences in acute toxicity, biochemical control or overall survival.Therefore, compared with C-IMRT, M-IMRT was associated with reduced rectal toxicity without compromising disease control.

Multiparametric prostate MRI-based intensity-modulated radiation therapy guided by prostatic calcifications

“…15 Prostate IGRT would become an even more convenient, comfortable and cost-effective treatment option if fiducial marker placement can be safely eliminated and by reducing number of visits through hypofractionation. 8,16 In the current study, the dose distributions and late toxicity rates compare favorably to the control arm of the recently published SpaceOAR System Pivotal Study. 8,17 reducing dose to the normal appearing prostate to 76 to 77.4 Gy using a simultaneously integrated boost technique.…”

“…IGRT remains a remarkably well-tolerated, effective and versatile non-invasive treatment for localized or locoregional prostate cancer. 8 Despite decades of research, the optimal technique to deliver IGRT for prostate cancer remains poorly defined and current NCCN guidelines allow for a variety of dose schedules and methods of image guidance. While daily CBCT for prostate cancer has been assessed in multiple randomized trials, fiducial markers were adopted without randomization.…”

“…Contemporary treatment techniques employed were previously described. 8 Briefly, prostate radiotherapy was performed on a Varian True Beam linear accelerator equipped with kilovoltage CBCT with instructions to maintain an empty rectum and a comfortably full bladder. Automatic image registration was performed at the treatment console by setting the prostate as the region of interest with manual adjustment informed by prostatic calculi.…”

“…Planning directives were previously described and were scaled accordingly when hypofractionation was prescribed. 8 When available, multiparametric prostate MRI were fused to the CT simulations using Eclipse using a volume of interest limited to the prostate and anterior rectal interface to assist with accurate target delineation. The mean radiation dose was 78 Gy (range 60 to 81 Gy).…”

“…6 An adaptive CBCT-based IGRT strategy without fiducial markers improved biochemical control in patients with rectal distension on CT simulation and was associated with decreased grade ≥2 rectal toxicity compared to IMRT without image guidance. 7,8 Some authors now argue that implanted fiducial markers are no longer needed for prostate radiotherapy. 9 Safely eliminating fiducial marker placement would obviate the risks of transient pain, bleeding, inflammation and a symptomatic infection rate of up to 7.7%.…”