Hypofractionated radiation therapy ‘new standard of care’ for high-risk prostate cancer
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Men with high-risk prostate cancer who received a shorter course of radiation therapy had similar survival and recurrence rates as those who received a longer, standard radiation therapy course, phase 3 trial results showed.
Final data from the randomized Prostate Cancer Study 5 — presented at American Society for Radiation Oncology Annual Meeting — revealed the two regimens had similar safety profiles, with no grade 4 or higher treatment-related adverse events in the study.
The results suggest that a 5-week hypofractionated radiation therapy regimen should be considered a new standard of care for men high-risk prostate cancer eligible for external beam radiation and long-term androgen deprivation therapy, the investigators noted.
Background
Moderate hypofractionated radiation therapy has evolved into standard practice for most low- and intermediate-risk localized prostate cancer, according to Tamim M. Niazi, MD, associate professor in the department of oncology at McGill University.
His group conducted the phase 3 study to see if this success could be replicated in men with high-risk prostate cancer without compromising the effectiveness of outcomes.
“If we treat patients with high-risk prostate cancer using conventional radiation therapy, it takes about 8 weeks,” he told the audience. “The idea was to decrease the number of days our patients needed to come to the hospital.”
Methodology
The multicenter, Canada-based PCS5 enrolled 329 patients with high-risk prostate cancer randomly assigned in a 1:1 ratio to receive either conventionally fractionated radiation therapy (n = 165) or hypofractionated radiation therapy (n = 164).
The final survival analyses included 159 men in the hypofractionation group and 160 in the conventional radiation therapy group.
Study participants received 28 months of neoadjuvant, concurrent and adjuvant ADT.
Conventional fractionated therapy took place over 8 weeks at a dose of 76 Gy in 38 fractions. Hypofractionated radiation therapy lasted 5 weeks at a dose of 68 Gy in 25 fractions.
Key findings
Seven-year follow-up results showed no significant differences in OS between the hypofractionated and conventional radiation therapy groups (81.7% vs. 82%; HR = 0.92; 95% CI, 0.56-1.53).
This trend remained consistent for other variables explored in the study, including prostate cancer-specific mortality (94.9% vs. 96.4%; HR = 1.31; 95% CI, 0.46-3.78); biochemical recurrence (87.4% vs. 85.1%; HR = 0.89; 95% CI, 0.49-1.6); distant metastatic recurrence (91.5% vs. 91.8%; HR = 0.89; 95% CI, 0.41-1.9); and disease-free survival (86.5% vs. 83.4%; HR = 0.82; 95% CI, 0.47-1.46).
Investigators reported relative risk ratios close to 1 for all outcomes at 3, 5 and 7 years after treatment.
Safety results showed no significant differences in grade 3 or higher acute or long-term genitourinary or gastrointestinal toxicities up to 2 years after treatment.
Researchers noted no grade 4 or higher treatment-related toxicities in either treatment group.
Clinical implications
“Hypofractionated radiation therapy using 68 Gy in 25 fractions is as effective as conventional fractionation using 76 Gy in 38 fractions, with similar and acceptable toxicity,” Niazi told the audience. “Moderately hypofractionated radiation therapy using 68 Gy and in 25 fractions should be considered as a new standard of care for [patients with] high-risk [prostate cancer] considered for primary external beam radiation therapy and long-term androgen deprivation therapy.”
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Niazi TM, et al. Abstract 4. Presented at: American Society for Radiation Oncology Annual Meeting; Oct. 23-26, 2022; San Antonio.
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