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Shorter course of higher-dose radiotherapy does not increase toxicity in localized prostate cancer
Ultra-hypofractionated stereotactic body radiotherapy did not appear to increase acute toxicity compared with conventionally fractionated therapy among men with localized prostate cancer, according to results of a randomized phase 3 noninferiority trial published in The Lancet Oncology.
The findings — also presented at American Society of Radiation Oncology Annual Meeting — could lead to a significant decrease in treatment time, from 1 to 2 months to 1 to 2 weeks, researchers noted.
“The new results from our clinical trial have shown that a much shorter course of higher-dose radiotherapy does not increase short-term side effects compared with the current standard of care,” Douglas H. Brand, MD, research fellow in clinical oncology at The Institute of Cancer Research in London and Royal Marsden NHS Foundation Trust, said in a press release. “If the data on longer-term side effects and efficacy are also positive, we expect our trial could be practice changing. This would enable us to deliver curative treatment over fewer days — meaning that men would get the same benefit from their radiotherapy while having to spend less time in the hospital.”
The open-label, randomized PACE trial is evaluating noninferiority of SBRT vs. conventionally fractionated or moderately hypofractionated radiotherapy for clinical or biochemical failure at 37 centers in the U.K., Ireland and Canada.
In the PACE-B portion of the trial, Brand and colleagues randomly assigned 847 men with low- or intermediate-risk prostate cancer to conventionally fractioned or moderately hypofractionated radiotherapy (n = 432; median age, 69.7 years; 89% white) or ultra-hypofractionated SBRT (n = 415; median age, 69.6 years; 85% white) to compare acute gastrointestinal and genitourinary toxicity in both groups.
Patients in the standard-of-care group received conventionally fractioned or moderately hypofractionated radiotherapy at 78 Gy in 39 fractions over 7 to 8 weeks or at 62 Gy in 20 fractions over 4 weeks. The other group received SBRT at 36.25 Gy in five fractions over 1 to 2 weeks with an additional secondary clinical target volume dose target of 40 Gy.
Coprimary outcomes of the acute toxicity substudy included worst grade 2 or higher Radiation Therapy Oncology Group (RTOG) gastrointestinal or genitourinary toxic effects up to 12 weeks after radiotherapy.
Results showed grade 2 or worse acute RTOG gastrointestinal toxic events occurred among 53 patients (12%) who completed at least one fraction of conventionally fractioned or moderately hypofractionated radiotherapy compared with 43 patients (10%) who completed at least one fraction of SBRT (difference, –1.9%; 95% CI, –6.2 to 2.4).
Grade 2 or worse acute RTOG genitourinary toxic events occurred among 118 patients (27%) in the control group compared with 96 patients (23%) in the SBRT group (difference, –4.2%; 95% CI, –10 to –1.7).
No patients died during treatment.
“It is reassuring to see from this trial that SBRT does not significantly impact patients’ quality of life in the short term compared with the standard of care,” study author Nicholas van As, MD, consultant clinical oncologist at Royal Marsden NHS Foundation Trust, said in a press release. “Using SBRT to deliver this treatment would mean that patients could be spared numerous visits to the hospital, allowing them to get back to their lives sooner.” – by John DeRosier
Disclosures: Brand reports honoraria from Cancer Research UK. Van As reports research funding from Accuray. Please see the study for all other authors’ relevant financial disclosures.