Slightly fewer (severe) complications after IMRT compared to CRT


According to a media release from the University of Pennsylvania Health System, (and another from the American Society of Radiation Oncology [ASTRO]), intensity-modulated radiation therapy (IMRT) is associated with fewer complications than traditional, three-dimensional conformal radiation therapy (3D-CRT) in the treatment of non-metastatic prostate cancer.

The media releases refer to data to be presented on Monday next week at the annual meeting of ASTRO.

Bekelman et al. conducted a  retrospective analysis of patient data from the the Surveillance, Epidemiology and End Results (SEER)-Medicare database. From that database, they identified men age 65 years or older diagnosed with non-metastatic prostate cancer between 2002 and 2004, treated with IMRT or 3D-CRT, and followed through December 31, 2006.

The basic results of their study showed that:

  • 5,845 patients were treated with IMRT.
  • 6,753 patients were treated with 3D-CRT.
  • The cumulative incidence of composite bowel complications at 24 months follow-up was 18.8 percent in the IMRT group and 22.5 percent in the 3D-CRT group.
  • The cumulative incidence of proctitis/hemorrhage at 24 months follow-up was 3.5 percent in the IMRT group and 4.5 percent in the 3D-CRT group.
  • IMRT was associated with a statistically significant reduction in composite bowel complications (hazard ratio [HR] = 0.86) and proctitis/hemorrhage (HR = 0.78) compared to 3D-CRT.
  • IMRT was not associated with any statistically significant reduction in composite urinary complications (HR = 0.93) or cystitis/hematuria (HR = 0.94) compared to 3D-CRT.
  • The incidence of erectile complications involving invasive procedures was very low and did not differ significantly between groups.

The study makes no mention about the relative doses of radiation delivered to these patients, but it would be reasonable to assume that patients receiving treatment with IMRT would have tended to receive a significantly higher dose of radiation than patients being treated with 3D-CRT. It is also likely that a significant number of these patients received either neoadjuvant or adjuvant hormone therapy in combination with their radiation.

These reductions in risk for complications of radiation therapy are less than might have been hoped for by many clinicians and patients. Clearly any reduction in side effects of radiation therapy is helpful, but this paper still suggests that the bowel complications of radiation therapy — even using a highly targetable type of radiation — occur in more like 20 percent of patients than 10 percent. And the absolute reduction in risk for bowel complications in this study was only 3.7 percent.

It should also be noted that the methodology of this study is severely limiting; it is really restricted to analysis of risk for the type of serious complication that needed surgical intervention to identify, monitor, or correct the problem (e.g., a colonoscopy), and this is only a small subset of the known spectrum of side effects following radiation therapy. It is also possible that some of the problems identified were not, in fact, a consequence of the radiation therapy at all. Many of the patients in this cohort are likely, for example, to have been receiving radiation therapy as an adjuvant to surgery or as salvage therapy for prostate cancer progression after a prior radical prostatectomy. It may be difficult to appreciate some of the nuances of a paper like this until we can see a published and peer-reviewed article.

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