Commenting on this study, formal discussant D. Andrew Loblaw, MD, a radiation oncologist at the Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Canada, said: “The trial showed that after a median follow-up of 7.0 years, there were no differences in overall survival between the two groups. This, however, is not surprising given the follow-up; one wouldn’t expect to see a difference in survival until at least a median of 13 years of follow-up. There was a clinically significant difference in biochemical disease-free survival, local tumor control, and a trend toward improvement in time to metastatic disease, all favoring the higher-dose group.”

Dr. Loblaw acknowledged the higher risk of moderate gastrointestinal and genitourinary toxicities associated with the higher-dose group. “The chance of serious side effects in the high-dose group was only nominally higher in the gastrointestinal realm,” he said.

“Overall, this study is consistent with the five other randomized dose-escalated external-beam studies—data that have already changed practice. Although very well conducted, we’ll have to wait another 7 years to see whether this study can address the question of whether five additional external-beam treatments improve overall survival,” Dr. Loblaw stated.

Dose escalation has already entered the realm of clinical practice. According to Dr. Loblaw, in both Canada and Europe, doses higher than 74 Gy are standard, as per guidelines. “In the United States, the National Comprehensive Cancer Network Guidelines don’t specify dose, but all of the physicians I have interacted with offer dose escalation,” he said. ■

Disclosure: Dr. Loblaw reported no potential conflicts of interest.