After three years, 88% of the men, overall, remained free of cancer. Specifically, it was 100% of the men with low-risk cancer, 86% of the men with medium-risk cancer, and 75% of those with high-risk cancer who remained cancer-free.
Among 27 men whose PSA levels rose, 25 had their cancer return. In 15, the cancer returned in the prostate, and in the others it had spread to other areas of the body, the researchers found.
When the men were treated, no serious side effects occurred. Later on, however, two men had urethral strictures, which can prevent urination and required surgery, and two patients developed rectal fistulae that required an operation called a colostomy.
Tharmalingam said that to improve the results of single high-dose radiation among men with medium- and high-risk cancer, other groups are experimenting with radiation doses as high as 23 Gy.
But for these patients, it might be better to go back to giving smaller doses of radiation over a longer time, Tharmalingam said.
Dr. Anthony D’Amico, a professor of radiation oncology at Harvard Medical School in Boston, doesn’t think high-dose radiation is safe. D’Amico was not involved with the new study but was familiar with the findings.
“This single dose of radiation is very convenient and very well thought out in terms of killing the cancer,” he said. “But there is no way to get around the one stumbling block, which is the follow-up of only three years.”
A follow-up of three years in prostate cancer has very little meaning because it doesn’t indicate what will happen over the long term, D’Amico said.
Even more troubling were the side effects seen in some patients, namely urethral strictures and rectal fistulae, he said.
“These are unheard of complications in the radiotherapy world in this day and age,” D’Amico said. “You don’t see those anymore because those things are the result of doses being way too high.”
These side effects can take years to appear, so seeing even a few patients developing them so soon is very concerning, he explained.