Study confirms safety and efficacy of higher-dose-per-day radiation for early-stage prostate cancer

The shorter approach, known as isodose moderately hypofractionated radiotherapy (MHFRT), delivers slightly higher doses of radiation per session, allowing the total treatment duration to be over four to five weeks instead of seven to eight weeks.

According to the study, patients who received this type of MHFRT had the same cancer control rates as those who received conventional radiotherapy. Additionally, the risk of long-term side effects affecting the bladder and intestines was no higher with MHFRT, confirming its safety.

The findings were published in The Lancet Oncology.

"We believe these data strongly support that isodose MHFRT should become the preferred standard of care MHFRT regimen for prostate cancer," said Dr. Amar Kishan, executive vice chair of radiation oncology at the David Geffen School of Medicine at UCLA and co-first author of the study. "More broadly, there appears to be little reason to consider conventional radiotherapy over MHFRT for the types of patients enrolled in these trials given these results."

While MHFRT is now the most commonly used radiotherapy regimen for prostate cancer, concerns remain about whether delivering a higher daily dose increases the risk of urinary and bowel issues, such urinary incontinence, chronic diarrhea and rectal bleeding.

To better understand whether there might be an increased risk of toxicity with the delivery of a higher dose per day of radiation, Kishan and the team of researchers examined data from more than 5,800 patients across seven randomized clinical trials comparing standard therapy with two different MHFRT approaches: isodose MHFRT, which maintains the total radiation dose at a level similar to standard therapy, and dose-escalated MHFRT, which increases the total dose in hopes of enhancing tumor control.

The analysis found patients who received isodose MHFRT (60 Gy in 20 fractions) had similar cancer control and side effects compared to those receiving conventional radiation therapy, with no significant difference in the five-year progression-free survival (77.0% for MHFRT vs. 75.6% for conventional).

Patients who received higher dose-escalated MHFRT did not improve cancer control when compared to those receiving standard doses, with five-year progression-free survival rates being identical to conventional therapy (82.7% in both groups). Patient-reported outcomes also showed significantly higher gastrointestinal side effects (7.2% vs. 4.9%), particularly bowel issues.

While dose-escalated MHFRT was expected to improve outcomes, the data showed no additional benefit in cancer control and a higher risk of gastrointestinal side effects, noted Kishan. This underscores the advantage of isodose MHFRT, which provides the same effectiveness as conventional therapy without increasing toxicity.

"These findings reinforce isodose MHFRT as the standard of care, offering the same cancer control as conventional treatment but with fewer side effects than dose-escalated MHFRT," said Kishan, who is also a researcher in the UCLA Health Jonsson Comprehensive Cancer Center. "Patients can safely opt for a shorter treatment schedule without compromising their outcomes, ensuring they receive effective care with fewer visits and minimal added risk. Less time in treatment can still mean the best possible results."

The study's other co-first author is Yilun Sun from case Western Reserve University School of Medicine. Other UCLA authors are Dr. Michael Steinberg, Dr. Luca Valle, Dr. John Nikitas, and Dr. Tahmineh Romero Kalbasi. A full list of authors can be found in the study.

The study was supported in part by grants from the Department of Defense and the National Institutes of Health.