Patients who undergo radiation treatment for localized prostate cancer (PCa) are more likely to have procedural interventions for late gastrointestinal (GI) toxicities than men whose PCa is managed conservatively, according to a study.

Researchers found that proton therapy was associated with the highest rate of late GI complications and brachytherapy alone was associated with the lowest rate, according to a report in European Urology (published online ahead of print).

The study, by Grace L. Lu-Yao, MD, of the Cancer Institute of New Jersey in New Brunswick, and colleagues, included 28,088 PCa patients treated with radiotherapy and 13,649 who were managed conservatively (no surgery, radiotherapy, or hormone therapy for at least a year after the PCa diagnosis).

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GI bleeding or ulceration were the most common GI toxicities. GI toxicity rates were 9.3 per 1,000 person-years after three-dimensional conformal radiotherapy, 8.9 per 1,000 person-years after intensity-modulated radiotherapy, 5.3 per 1,000 person-years after brachytherapy alone, 20.1 per 1,000 person-years after proton therapy, and 2.1 per 1,000 person-years for conservative management. Radiation therapy was associated with 4.7 times increased risk of GI toxicity compared with conservative management. Even after five years, the radiation group had a threefold increased risk of GI toxicity.

The researchers cautioned that their study population ranged in age from 66 to 85 years, so results may not be applicable to younger patients.

Of the various radiation modalities, the authors observed, IMRT in more recent years and brachytherapy by itself are associated with relatively low rates of late grade 3/4 GI toxicities “and may be excellent choices in terms of optimizing the risk-benefit ratio.”

The investigators pointed out that although proton therapy had the highest GI toxicity, “it was very time dependent, and by 2004-2005 GI toxicity associated with protons had declined significantly.”

“These data show the latest technology may not necessarily be superior to existing ones and that a substantial learning curve often exists with new interventions,” Dr. Lu-Yao’s group concluded.