Protons linked to lower urinary AEs, higher costs than with IMRT for prostate cancer


Among men younger than 65 with prostate cancer, proton beam radiotherapy (PBT) was associated with significantly lower rates of urinary toxicities than was intensity-modulated radiotherapy (IMRT), but this safety advantage came at the cost of nearly $60,000 extra per patient, results of an insurance claims study show.

The rate of a composite of urinary toxicities at 2 years among 693 men treated with PBT was 33%, compared with 42% for 3,465 men matched by propensity score who were treated with IMRT. Respective rates of erectile dysfunction were 21% vs. 28%. The mean cost for PBT, however, was nearly double that for IMRT, reported Benjamin D. Smith, MD, of the University of Texas MD Anderson Cancer Center in Houston, and his colleagues.

Although PBT was better at sparing patients from urinary toxicities, it was associated with increased bowel toxicities, and a second comparison of IMRT with stereotactic body radiotherapy (SBRT) showed that SBRT, while slightly cheaper than IMRT, was associated with modest increases in some urinary toxicities, the researchers reported in a study published online in the Journal of Clinical Oncology .

“These key findings, coupled with the real-world private insurance cost reported herein, will be useful for patients selecting the most appropriate treatment and for researchers designing cost-effectiveness models to guide treatment decisions in prostate cancer,” they wrote.

The investigators combed through the MarketScan Commercial Claims and Encounters database to identify men who underwent radiation therapy for prostate cancer between 2008 and 2015. They used propensity-score matching, a technique designed to even out potential confounding factors, to compare those treated with IMRT with others treated with PBT or SBRT.

As noted, PBT was associated with significantly lower urinary toxicities and erectile dysfunction compared with IMRT (P less than .001 for each comparison), but with a higher rate of bowel toxicities at 2 years (20% vs. 15%, P = .02).

The mean cost per patient in 2015 dollars for PBT was $115,501, compared with $59,012 for IMRT.

In a comparison of outcomes and costs for 310 patients who underwent SBRT matched with 3,100 who underwent IMRT, the investigators found no significant differences in composite urinary, erectile dysfunction, or bowel toxicities. However, the risk of urinary fistula, while low, was significantly higher with SBRT compared with IMRT, with rates of 1% vs. 0.1%, respectively (P = .009).

The mean cost of SBRT in this analysis was $49,504, compared with $57,244 for IMRT (P less than .001).

The investigators acknowledged that by using claims data they were unable to plug information about potential confounding factors such as Gleason score, prostate-specific antigen level, clinical stage, or radiation field and dose into their propensity-score models. They also noted that follow-up was relatively short because of the vicissitudes of the U.S. insurance market, which causes many patients to change insurers frequently.

The study was supported by grants from the National Cancer Institute and by Varian Medical Systems. Dr. Smith, lead author Hubert Y. Pan, MD, and others disclosed research support, consulting, and/or travel support from Varian.

SOURCE: Smith BD et al. J Clin Oncol. 2018 Mar 21. doi: 10.1200/JCO.2017.75.5371.