Hypofractionated IMRT outcomes comparable to standard regimen

“We showed that we can safely compress radiation into a shorter time frame, into fewer treatments, at higher dose per fraction, with similar clinical outcomes and similar toxicity profiles,” said researcher Michael Wang, MD.

Condensing radiotherapy for high-risk prostate cancer patients into 25 sessions by increasing the radiation dose of each treatment offers similar overall survival, progression-free survival, biochemical control rates, and toxicity profiles as the standard treatment of 39 fractions, according to a study presented at the Genitourinary Cancers Symposium in Orlando, FL.

Lead author Michael Wang, MD, of the Cross Cancer Institute and the University of Alberta, Edmonton, Alberta, said he and colleagues studied 100 high-risk prostate cancer patients, who had hypofractionated intensity-modulated radiotherapy from 2005 to 2012 and followed them for a median 5.4 years. In this condensed radiotherapy regimen, patients received a total of 68 Gy in 25 treatment sessions, versus the standard regimen where patients received a total of 78 Gy in 39 treatment sessions.

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“Overall survival at the 5-year mark was 88.7%. Progression-free survival at 5 years was 92.8%. Biochemical control rate at 5 years was 91.8%. So, with 25 treatments, at higher dose per fraction, the clinical outcomes are comparable to the standard regimen of 39 fractions,” said Dr. Wang, who worked on the study with Nawaid Usmani, MD, and colleagues.

Radiotherapy hypofractionation isn’t a viable option for all cancers, according to Dr. Wang. Prostate cancer is amenable because it is slow-growing and extremely sensitive to radiation treatment. An already-published study by Dr. Wang’s team shows acceptable acute toxicity profiles in patients who get hypofractionated radiation treatment for high-risk prostate cancer (Int J Radiat Oncol Bio Phys 2010; 76:57-64).

Next: Long-term side effects reviewed

The authors then looked at long-term side effects, or late toxicities, which are a concern when condensing radiotherapy. The two most worrisome areas of long-term concern for patients who get prostate cancer radiotherapy are gastrointestinal, such as diarrhea and bleeding, and genitourinary complications, such as urinary frequency and urgency.

They found that throughout the 5 years, the cumulative incidence of grade 3 or higher gastrointestinal toxicity was 16.7%, and the cumulative incidence of grade 3 or higher genitourinary toxicity was 13%. But at the end of 5 years, the incidences of these toxicities dropped dramatically to 0% of men with severe gastrointestinal toxicities and 1.9% of men with severe genitourinary toxicities.

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“These rates are very acceptable, as well. When you look at all of our results, we showed that we can safely compress radiation into a shorter time frame, into fewer treatments, at higher dose per fraction, with similar clinical outcomes and similar toxicity profiles,” Dr. Wang said.

While there are ongoing phase III trials looking at hypofractionation for high-risk prostate cancer, the treatment approach is considered to be on par with the standard 39 radiotherapy treatments. And preliminary findings on quality of life in work that has not yet been published are equally as promising, suggesting quality of life is comparable in patients getting the condensed 25-treatment approach, according to Dr. Wang.

When high-risk prostate cancer patients are eligible for hypofractionated intensity-modulated radiotherapy, there are clear benefits in patient convenience, health care utilization, and health care costs, according to Dr. Wang.

Dr. Usmani is a consultant/adviser for Amgen, Bayer, and Janssen.