Image-guided adaptive prostate radiation therapy reduces risk for short-term toxicities
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Key takeaways:
- A meta-analysis of 29 prospective studies showed a 44% reduction in risk for short-term urinary adverse events.
- Researchers also reported a 60% reduction in risk for short-term bowel adverse events.
Magnetic resonance-guided daily adaptive stereotactic body radiotherapy appeared associated with a reduction in acute toxicity compared with a more common technique for men with prostate cancer, according to data published in Cancer.
Researchers observed significantly lower risk for acute grade 2 or higher genitourinary and gastrointestinal toxicities with the guided approach compared with CT-guided nonadaptive prostate SBRT.
“Advanced technological tools for providing precise radiotherapy can substantially reduce the impact of side effects on patients receiving radiotherapy for prostate cancer, and [magnetic resonance-guided daily adaptive SBRT] is an important example of this,” Jonathan E. Leeman, MD, assistant professor of radiation oncology at Harvard Medical School, told Healio. “In particular, the role of adaptive radiotherapy, which involves personalizing each individual radiation treatment for the patient’s anatomy in the moment of treatment and accounting for day-to-day changes in the positions of critical organs such as the prostate, bladder, rectum and urethra, may be responsible for the observed difference in side-effect profile.”
Background and methodology
Use of SBRT for prostate cancer management has become more common, according to researchers, but toxicity remains a concern when administering daily adaptive SBRT with standard techniques.
Leeman and colleagues conducted a meta-analysis to compare acute toxicity rates associated with magnetic resonance-guided daily adaptive SBRT [MRg-A-SBRT] vs. fiducial or CT-guided nonadaptive prostate stereotactic body radiotherapy [CT-SBRT] among men with prostate cancer.
The investigators used random and fixed effects models to pool toxicity rates among prospective studies published between Jan. 1, 2018, and Aug. 31, 2022. They also performed meta-regression to compare toxicity between MRg-A-SBRT and CT-SBRT cohorts.
In total, 29 prospective studies that included 2,547 patients met the inclusion criteria.
Results
MRg-A-SBRT had lower pooled estimates for acute grade 2 or higher genitourinary toxicity (16%; 95% CI, 10-24) and gastrointestinal toxicity (4%; 95% CI, 2-7), than CT-SBRT (genitourinary, 28%; 95% CI, 23-33; gastrointestinal, 9%; 95% CI, 6-12).
Meta-regression analysis showed a 44% reduction in risk for genitourinary toxicity (OR = 0.56; 95% CI, 0.33-0.97) and 60% reduction in risk for gastrointestinal toxicity (OR = 0.4; 95% CI, 0.17-0.96) with MRg-A-SBRT compared with CT-SBRT.
“We were surprised at the degree of reduction in urinary and bowel side effects found with MRg-A-SBRT ... and the consistency of this finding across several clinical trials that we studied,” Leeman told Healio. “Furthermore, most of the other important variables — such as the dosage of radiation and the area of tissue that was targeted surrounding and including the prostate — were similar across these studies, suggesting that it likely is the technology that is making a difference for patients.
Next steps
Further research will be needed to understand the long-term safety and efficacy of MRg-A-SBRT, according to Leeman.
“Because this is a relatively new technology, we were only able to study short-term side effects that occurred during treatment and within a few months following treatment,” he said. “It will be important to see what the long-term impact is on urinary and bowel side effects years following MRg-A-SBRT once the data are more mature. In addition, studying the efficacy of MRg-A-SBRT treatment for eradicating prostate cancer compared with more standard treatments will be crucial, but this too will take several years of data collection before more conclusive evidence is available.”
In an accompanying editorial, Peter A.S. Johnstone, MD, a radiation oncologist at Moffitt Cancer Center, commended the researchers for their work while suggesting the adapted approach be used only for men with prostate cancer who will truly benefit from it.
“The issue not widely discussed is the lost opportunity costs of treating [men with prostate cancer] with MRg-A-SBRT: if treating prostates removes the opportunity to treat other patients who could benefit more from the technique and the technology,” Johnstone wrote. “For now, for appropriate [patients with prostate cancer], we simply use [magnetic resonance-guided SBRT] and are delighted with our outcomes,” he added.
References:
- Leeman JE, et al. Cancer. 2023;doi:10.1002/cncr.34836.
- Johnstone PAS. Cancer. 2023;doi:10.1002/cncr.34835.
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Leeman JE, et al. Cancer.2023;doi:10.1002/cncr.34836.
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