Prostate Cancer Patients Got the Same Result in Fewer Visits

Salvage radiation given over 26 sessions kept prostate cancer in check as well as the conventional schedule did, according to four-year results from the phase 3 SHARE trial published in Journal of Clinical Oncology. The conventional schedule delivers a total dose of 66 Gy across 33 sessions. Gy, short for gray, is the unit used to measure how much radiation the body absorbs. The shorter course packs a similar total dose, 65 Gy, into 26 sessions by giving more radiation at each visit.

The trial enrolled patients with intermediate- to high-risk prostate cancer at two medical centers in the Republic of Korea. All of them had already had surgery to remove the prostate, and all had seen their prostate-specific antigen (PSA) level start to climb again afterward. A rising PSA level is usually the first sign that prostate cancer has come back, and radiation given at that point is the last treatment still aimed at a cure. Researchers wanted to know whether a shorter, more concentrated course of radiation would control the cancer better than the standard course.

What did the phase 3 SHARE trial find about shorter salvage radiation?

The main measure of success, called the primary end point, was how long patients went before their PSA level rose again.

At four years, 80.1% of patients on the shorter course and 78.1% on the longer course still had no rise in PSA. The two rates sit close enough that the edge for the shorter course falls within the range chance alone can produce in groups this size. Researchers had designed the trial expecting the shorter course to come out well ahead. It did not, and it did not fall behind either. PSA began rising again in 29 patients on the shorter schedule and 31 on the longer one, and the shorter course reached that result in fewer visits.

Every other measure came out the same way. PSA fell low enough to be undetectable in 76.6% of patients on the shorter course and 76.7% on the longer one. Four years in, 91.7% of the shorter-course group and 91.0% of the longer-course group had no sign the cancer had spread to other parts of the body. No patient in either group died of prostate cancer during the study. Scans caught cancer that had returned in 14 patients (9.7%) on the shorter schedule and 20 patients (13.3%) on the longer one.

How was radiation given in the SHARE trial?

Between August 2019 and November 2021, 316 patients were randomly assigned to one of the two schedules, and 295 were included in the final analysis. Median follow-up was 52.6 months.

To join the trial, patients needed a PSA level of 1.0 ng/mL or lower after surgery, and the median level going into radiation was 0.36 ng/mL. Radiation was aimed at the prostate bed, meaning the area where the prostate used to sit. Nearby pelvic lymph nodes were also treated in 202 patients (68.5%), and 151 patients (51.2%) received androgen deprivation therapy, a hormone treatment that lowers testosterone to slow prostate cancer.

Doctors also had the option of using an endorectal balloon, a device placed in the rectum to hold it still and shift it away from the radiation beam. It was used in 186 patients (63.1%).

What side effects came with the shorter radiation course?

Late bowel side effects rated grade 2 or higher, meaning moderate or worse and needing treatment, were more common on the shorter schedule. The four-year rate was 7.9%, compared with 0.7% on the standard schedule, a difference too large to be explained by chance. Rectal bleeding accounted for most of the reports. All of the side effects had cleared up by the last follow-up, and neither group had any life-threatening or fatal late side effects.

The gap showed up mostly in patients treated without an endorectal balloon. Within the shorter-course group, the four-year rate of late bowel side effects was 15.3% without the device and 3.5% with it.

Urinary side effects were similar in both groups, with four-year rates of 12.0% and 10.4%. The most common complaints were worsening of incontinence patients already had, blood in the urine and getting up at night to urinate. Grade 3 late side effects, the kind that usually require added treatment, occurred only on the shorter schedule. Three patients had rectal bleeding, one had blood in the urine and one had abdominal pain.

Patients' own reports of how they felt came out the same in both groups. Scores covering urinary function, bowel function and overall health matched up at every point measured.

Hypofractionated radiation "may be considered a potential alternative to conventional fractionation in the salvage setting," the study authors concluded.

They cautioned that the results are an interim look and that prostate cancer moves slowly enough to need longer follow-up. The trial also began before PSMA PET/CT scanning came into use in the Republic of Korea, and decisions about hormone therapy were left to each treating physician rather than set by the trial's rules.

Reference

1. Song Y, Park W, Pyo H, et al. "Salvage Hypofractionated Accelerated Versus Standard Radiotherapy for Biochemical Recurrence After Radical Prostatectomy: A Phase III Randomized Clinical Trial." Journal of Clinical Oncology. Published August 25, 2026.

For more news on cancer updates, research and education, don't forget to subscribe to CURE®'s newsletters here.