The treatment, called ultrahypofractionated radiotherapy, calls for patients to receive treatment every other weekday for two-and-a-half weeks, instead of every weekday for eight weeks, as required in conventional fractionated radiation therapy.
In addition to using a lower total dose, the treatment was found to be as safe and effective as the standard approach, according to researchers.
The findings were presented at the European Society for Radiotherapy and Oncology (ESTRO) 37 Congress, held April 20-24 in Barcelona, Spain.
The study, “Ultrahypofractionation for prostate cancer: outcome from the Scandinavian phase 3 HYPO-RT-PC trial,” was presented by Prof. Anders Widmark, a senior consultant at Umeå University in Sweden.
“We already know that radiotherapy can destroy cancer cells in the prostate and that it has advantages over surgery and hormone therapy because it is less likely to cause impotence or incontinence. However, radiotherapy requires expensive specialist equipment and patients can end up on a waiting list for treatment,” Widmark said in a press release.
“Ultrahypofractionated radiotherapy offers a number of practical benefits to patients as well as time and cost-savings for hospitals, so we wanted to test if it is as safe and effective as standard radiotherapy,” he added.
The trial, called HYPO-RT-PC, enrolled 1,200 patients diagnosed with medium- or high-risk prostate cancer who were treated at 10 hospitals in Sweden and two in Denmark from July 2005 to November 2015. None had received treatment to block the male hormone testosterone, which induces prostate tumors to grow.
Patients were randomly assigned to standard radiotherapy or ultrahypofractionated radiation therapy. Those in the standard treatment arm received a total of 78 Gy (a measure of radiation), given over 39 sessions of 2 Gy each. This was administered every weekday for eight weeks.
Those in the ultrahypofractionated arm received a total dose of 42.7 Gy, divided in seven sessions of 6.1 Gy each. The treatment was given every other weekday for two-and-a-half weeks.
The trial’s main goal was to show that the hypofractioned radiation treatment was as good at keeping cancer at bay as the standard treatment.
Patients were followed for an average of five years to determine if the cancer had returned, measured by rising levels of prostate specific antigen (PSA), a protein present in high levels in prostate cancer.
In addition to efficacy, researchers also wanted to determine the treatment’s safety, and its effects on quality of life.
While patients receiving the hypofractionated radiation approach experienced somewhat worse side effects at the end of treatment, long-term side effects were similar in both treatment arms.
At four years, the rates of urinary and bowel toxicity — 4.1% and 1.6% — were similar in both groups. Interestingly, at six years, there was a trend toward higher toxicity rates in the standard treatment arm: 3.5% and 2.5% for urinary toxicity and 2.3% and 1.2% for bowel toxicity.
Also, at five years, 83.8% of patients receiving standard radiotherapy showed no signs of cancer recurrence; the figure was 83.7% for those on the ultrahypofractionated arm.
“Previous research has already shown that it’s possible to increase individual doses and give them over five weeks. Now we have shown that we can condense the therapy further, raising the dose at each hospital visit so that the whole schedule lasts only two and half weeks,” Widmark said.
“This is the first large patient trial of this kind and it shows that ultrahypofractionated radiotherapy is just as effective as standard radiotherapy at stopping prostate cancer from returning,” he said. “Importantly, it also shows that patients treated this way do not suffer any more side-effects than those treated with conventional radiotherapy.”
Researchers will continue to follow the patients included in the trial to examine differences in survival rates and long-term side effects for each treatment approach.
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