Clinical trial confirms safety and effectiveness of shortened radiation therapy for high-risk prostate cancer patients

Clinical trial confirms safety and effectiveness of shortened radiation therapy for high-risk prostate cancer patients

A new randomized trial confirms that men with high-risk prostate cancer can be treated with five weeks of radiotherapy instead of eight. The phase III clinical study confirms for the first time the safety and effectiveness of a moderately shortened radiation duration exclusively for patients with high-risk diseases. Results from the Prostate Cancer Study 5 (PCS5; NCT01444820) will be presented today at the American Society for Radiation Oncology (ASTRO) Annual Meeting.

I think this study will pave the way for patients with high-risk prostate cancer to be treated in five weeks instead of eight. Many of these patients are still offered eight weeks of radiation therapy, but our study found no benefit for the three additional weeks. Survival rates and side effects, both short-term and long-term, were similar with moderately shortened radiotherapy.”

Tamim M. Niazi, MD, lead author, assistant professor of oncology, McGill University and radiation oncologist at the Jewish General Hospital in Montreal

Large, randomized trials have confirmed the safety and effectiveness of moderately shortened or hypofractionated radiotherapy in patients with low-, intermediate-, and mixed-risk prostate cancer. The PCS5 study is the first to show the same results specifically for men with high-risk diseases.

“We asked: Can we deliver radiation safely and effectively in a shorter amount of time so that our high-risk patients can complete their treatment more quickly?” said Dr. Niazi. "Hypofractionated treatment for prostate cancer reduces the financial burden on patients and is completed in 25 days instead of the usual 38 to 40 days. That's three weeks without having to come to the clinic - transportation, parking costs and just time." it affects a person’s everyday life.”

Approximately 15% of men diagnosed with prostate cancer have a high-risk condition. These men are at higher risk than the lower risk groups of the cancer coming back and/or spreading, and in these cases they are more likely to die from their disease. The radiobiological properties of prostate cancer cells make them particularly sensitive to changes in radiation therapy fraction size, explained Dr. Niazi. "The whole idea behind this study - administering moderately higher doses of radiation therapy per day in conjunction with long-term androgen deprivation therapy (ADT) - is that we may be able to maintain the same prostate cancer control rates as with standard fractionation, but in a shorter period of time."

In this multicenter Canadian study, 329 patients were randomized to receive either standard/conventionally fractionated prostate irradiation (76 Gy in 38 daily sessions) or moderately hypofractionated radiation (68 Gy in 25 daily sessions). To participate in the study, patients had to have a high-risk disease indicated by a higher Gleason score (8-10), stage T3a or higher, or a PSA level above 20. All patients also received pelvic lymph node irradiation and long-term ADT before, during, and after irradiation (median duration was 24 months).

Seven years after completing radiation therapy, the men who received hypofractionated or standard treatment had similar recurrence and survival rates. When comparing patients who received accelerated treatment with standard treatment, researchers found no differences in overall survival (81.7% vs. 82%, p = 0.76), prostate cancer-specific mortality (94.9% vs. 96.4%, p = 0.61) and biochemical recurrence (87.4). % vs. 85.1%, p=0.69), distant metastatic recurrence (91.5% vs. 91.8%, p=0.76) or disease-free survival (86.5% vs. 83.4%, p=0.50).

Side effects were also similar between treatment arms. There were no grade 4 toxicities in either arm, and there were no significant differences in severe short-term or long-term genitourinary (GU) and gastrointestinal (GI) toxicities. Dr. Niazi said the team was pleasantly surprised that side effects were not significantly more pronounced with accelerated treatment.

While most patients with high-risk prostate cancer can benefit from shorter radiation therapy, Dr. Niazi noted that some patients - for example, those who had previously received prostate treatment (focal therapy) - received remote pelvic radiation therapy for other reasons or those patients with active inflammatory bowel disease, among other things, were excluded from the study and should still be treated with eight weeks of radiation.

Dr. Niazi outlined several next steps for this research. One way is to further reduce the number of fractions for patients with favorable high-risk disease, using an approach known as “ultra-hypofractionation,” which could potentially include as few as five treatments. Another approach is to intensify hormone therapy in patients with very high-risk diseases. “We know that the reason patients unfortunately die from their cancer is metastasis, and the only way to reduce the rate of metastasis is to intensify systemic therapy,” said Dr. Niazi. A final option is to look at biomarkers/gene changes to determine which patients should be treated more or less aggressively.

Source:

American Society for Radiation Oncology

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