Use of high dose and very high dose radiation therapy (RT) after radical prostatectomy (RP) for prostate cancer is increasing despite an absence of randomized studies supporting this postoperative treatment, according to a new study.
From 2003 to 2012, the use of high dose RT (greater than 6660 cGy) after RP increased from 29.9% to 63.5%, a team led by John Christodouleas, MD, of the University of Pennsylvania in Philadelphia, reported online ahead of print in Prostate Cancer and Prostatic Diseases. The use of very high dose radiotherapy (greater than 7020 cGy) increased from 4.5% to 10.8%.
“This change in practice may be exposing patients to excess toxicity without cancer control benefits,” Dr Christodouleas and his colleagues concluded.
Patients diagnosed at community centers were less likely to be treated with high dose radiation therapy compared with those at academic or comprehensive centers.
By 2012, approximately 2 out of 3 post-RP patients were treated with radiation doses greater than 6660 cGy and 1 out of 9 were treated with doses above 7020 cGy. “This observation is consistent with our hypothesis that radiation dose creep occurred in the absence of level I evidence,” the authors noted.
Dr Christodouleas’ team explained that in postoperative RT for prostate cancer, dose escalation cannot be achieved without increasing dose to normal tissues because most cells within the clinical target volume are part of normal/uninvolved nearby organs. “As such, dose escalation in this setting invariably increases risks of toxicities. The clinical benefits of dose escalation, however, are not clear.”
Although some retrospective studies suggest dose-escalated postoperative radiation therapy may improve biochemical control, there have been no randomized trials to support it, the authors pointed out.
For the study, the investigators analyzed data from 13,195 men (mean age 64 years (range 25 to 89 years) in the National Cancer Data Base (NCDB) who had pT2–3, N0, M0 prostate cancer and received radiation therapy following RP.
With regard to study limitations, the authors noted that the NCDB only captures cases in which postoperative radiation therapy was used as part of the first course of therapy. Patients treated with postoperative RT because of late postoperative biochemical recurrences may have different patterns of care, they explained. In addition, the investigators said they could not distinguish between patients receiving adjuvant therapy and salvage therapy as part of the first course of therapy. “If these patients are treated differently and their relative proportions are changing over time, changes in dosing may be obscured or magnified.”
Alexidis P, Guo W, Bekelman JE, et al. Use of high and very high dose radiotherapy after radical prostatectomy for prostate cancer in the United States. Prostate Cancer Prostatic Dis. 2018; published online ahead of print.