Study supports shorter radiation regimen in high-risk prostate cancer

Stereotactic body radiotherapy produced similar efficacy without added toxicity compared with standard radiation in men with advanced prostate cancer.

Reducing a standard 45-day radiation treatment course to a 5-day course administered in higher doses results in comparable efficacy and safety in patients with advanced prostate cancer, according to a study published online in the International Journal of Radiation Oncology, Biology, Physics.1,2

The study was a consortium analysis of patients with high-risk prostate cancer who received stereotactic body radiotherapy (SBRT), a hypofractionated radiotherapy technique consisting of 5 or fewer high-dose treatments. The findings showed an estimated 4-year biochemical recurrence-free survival (BCRFS) rate of 81.7%, and an estimated 4-year distant metastasis–free survival (DMFS) rate of 89.1% with SBRT.

“The estimated 4-year BCRFS rate of 81.7% for patients receiving SBRT in this consortium is similar to the 5-year BCRFS rates for [high-risk prostate cancer] patients enrolled on ASCENDE-RT who received a brachytherapy boost (85.5%) or dose-escalated conventionally fractionated radiotherapy alone cohort (83.6%) along with 12 months of androgen-deprivation therapy (ADT), despite the inclusion of patients in the present consortium who either received no ADT or received shorter durations of ADT,” the authors wrote.

For the study, researchers at UCLA Jonsson Comprehensive Cancer Center set up a consortium comprising 7 institutions that had phase 2 studies with prospective databases. Overall, efficacy and safety data were evaluated from 344 patients with high-risk prostate cancer. The minimum follow-up was 24 months. Statistical models, including Kaplan-Meier methods, were used to evaluate outcomes in these patients.

The median follow-up was 49.5 months (interquartile range [IQR], 35.8-61.9 months). The median PSA at baseline was 11 (range, 7-21.3) and almost 90% of patients had a disease stage of T1 or T2. About half (45%) of patients were Gleason grade group 4 and about one-fourth (24%) were Gleason grade group 5.

About three-fourths (72%) of patients received ADT for a median duration of 9 months (IQR, 9-18 months). Nineteen percent of patients had received nodal radiotherapy. Overall, BCR occurred in 59 patients (17%) and 26 patients (8%) had a DM.

There was a significant association between a 1-year increase in age at treatment and a higher BCR risk (HR, 1.04; P = .035). Receiving ADT was linked to significantly greater BCRFS (P = .009); however, there was not a similar association between ADT and DMFS (P = .097).

Regarding toxicity, 18% of patients experienced acute grade ≥2 genitourinary (GU) toxicity and 5% of patients experienced acute grade ≥2 gastrointestinal (GI) toxicity. There were no observed cases of acute grade ≥3 GU or GI adverse events.

The 4-year cumulative incidence estimates were 17.6% and 6.4% for late grade ≥2 GU and GI toxicity, respectively. The crude incidence of late grade 3 GU and GI toxicity was 2.3% and 0.9%, respectively. The median time to onset of late grade 3 GU and GI toxicity was 21 and 22 months, respectively.

“Conventional radiation, which requires daily visits for treatment, can be burdensome for many. Shortening radiation therapy from 6.5 weeks to 5 days is a significant advancement that can help improve the overall quality of life for men with prostate cancer,” the authors wrote.

“These data support a favorable toxicity and efficacy profile for SBRT for high-risk prostate cancer. Further prospective studies are needed to evaluate the optimal dose and target volume in the context of SBRT for high-risk prostate cancer,” added the authors.

References

1. Study finds shorter radiation regimen safe, effective for men with advanced prostate cancer. Published online January 25, 2021. Accessed January 27, 2021. https://bit.ly/36is8rc

2. Van Dams R, Jiang NY, Fuller DB, et al. Stereotactic Body Radiotherapy for High-Risk Localized CARcinoma of the Prostate (SHARP) consortium: analysis of 344 prospectively treated patients [published online ahead of print January 22, 2021]. Int J Radiat Oncol Biol Phys. doi: 10.1016/j.ijrobp.2021.01.016