Beyond the Abstract - Comparative Toxicity and Dosimetric Profile of Whole-Pelvis Versus Prostate Bed-Only Intensity-Modulated Radiation Therapy after Prostatectomy, by Curtiland Deville, MD

BERKELEY, CA (UroToday.com) - Whether to electively irradiate the pelvic lymph nodes in patients with high risk prostate cancer due to the risk of micrometasttic disease remains controversial with conflicting results in prospective randomized trials in the radical setting for patients with an intact prostate treated with radiotherapy (RT). In the post-prostatectomy setting there is no level I evidence to guide decision making, yet elective pelvic nodal irradiation continues with proponents largely extrapolating from the potential biochemical benefit in the radical RT setting. This potential benefit is mitigated by concerns of increased toxicity particularly in the post-prostatectomy setting.

An ongoing cooperative group trial (RTOG 0534) does seek to address this question and currently randomizes select patients in the salvage setting to prostate bed RT with or without elective pelvic nodal RT. While we await the accrual and maturation of that trial, it is worth investigating the morbidity of such treatment, particularly in the era of intensity modulated radiation therapy (IMRT) where improved targeting and reduced doses to surrounding tissues have demonstrated reduced toxicity rates compared to historical 2D conventional and 3D conformal techniques.

Our study, "Comparative Toxicity and Dosimetric Profile of Whole-Pelvis Versus Prostate Bed-Only Intensity-Modulated Radiation Therapy after Prostatectomy," sought to report the rates of genitourinary (GU) and gastrointestinal (GI) toxicities of patients treated post-prostatectomy out our institution with high dose IMRT to 70.2 Gy in the adjuvant or salvage setting to either the prostate-bed only, or additionally to the pelvic lymph nodes, classically termed the “whole pelvis” (WP). In this cohort of 67 patients, pretreatment patient characteristics, such as age and comorbidities were similar between groups. As expected, patients in the WP group had higher Gleason scores, tumor stages, and preoperative prostate-specific antigen (PSA) levels, and were more likely to receive androgen deprivation therapy (ADT). Despite treatment-planning dosimetric differences in irradiated bowel, bladder, and rectum between the treatment groups, we found that elective treatment of the pelvic lymph nodes resulted in only mild (grade 2), transient increases in GI toxicity (primarily treatable enteritis), no differences in acute GU toxicity, which may be of particular concern in these post-prostatectomy patient. With a median 25-month and minimum 12-month follow-up, we found no differences in late GI or GU toxicity.

These findings suggest that it is indeed safe to treat these high-risk patients post-prostatectomy – often with adverse risk features such as Gleason ≥ 8 disease or pathologic seminal vesicle invasion – with elective pelvic nodal irradiation, and that treatment is very well-tolerated.

Written by:
Curtiland Deville, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

Comparative Toxicity and Dosimetric Profile of Whole-Pelvis Versus Prostate Bed-Only Intensity-Modulated Radiation Therapy after Prostatectomy - Abstract

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