medwireNews: A single dose of high-dose rate (HDR) brachytherapy prevents biochemical recurrence for at least 3 years in patients with low-risk prostate cancer, but is less effective among those with higher-risk disease, researchers report.
The study, presented at the ESTRO 38 conference in Milan, Italy, included 441 patients with D’Amico classified low- (n=44), intermediate- (n=285), or high-risk (n=112) prostate cancer recruited from seven centers across the UK between 2013 and 2018.
All of the men were treated with HDR monotherapy at a dose of 19 Gy and were then followed-up for a median of 26 months. Just over a third (37.6%) of men overall also received androgen deprivation therapy for a median of 24 months, including 90.2% of those with high-risk disease, but none underwent surgery or chemotherapy.
Hannah Tharmalingam, from the Mount Vernon Cancer Center in Northwood, UK, defined biochemical failure as an increase in prostate-specific antigen levels of at least 2 ng/mL above the post-brachytherapy nadir.
She reported that, at 2 years, the biochemical progression-free survival (bPFS) rate was 94% for all patients, and was 100% in the low-risk group, 95% in the intermediate-risk group, and 92% in the high-risk group.
At 3 years, the bPFS rates were 88% overall, and 100%, 86%, and 75% in the low-, intermediate-, and high-risk groups, respectively.
There were 40 biochemical failures in total, for which 25 had the relapse site radiologically identified. Of these, 15 had a local prostate recurrence, including 11 cases of local relapse only, one locoregional recurrence, and three cases of local in conjunction with distant recurrence.
Commenting on this finding, Tharmalingam and co-investigators say: “Where biochemical failure occurred in intermediate and high-risk patients, isolated local relapse predominated supporting the rationale for further focal dose escalation to the dominant nodule which should be feasible given the low toxicity of the regime.”
There were no cases of acute (<90 days) grade 3 or 4 toxicity reported, but 12% of patients experienced acute grade 2 genitourinary toxicity and 3% had acute grade 2 gastrointestinal toxicity.
In addition, there were four cases of late (≥90 days) grade 3 toxicity: two patients developed urethral strictures that were surgically managed, and two had rectal fistulae requiring colostomy.
In a statement to the press, Tharmalingam said: “These results indicate that high dose-rate brachytherapy is a safe and effective treatment for men with low risk prostate cancer but further research is needed in medium and high risk patients to see if the results can be improved with a higher dose.”
She added: “This type of treatment offers an attractive alternative to surgery or other forms of radiotherapy as it has a comparatively low risk of side effects. It is also a patient-friendly option because the treatment can be given quickly at a single hospital visit.”
Commenting on the findings, chair of ESTRO’s brachytherapy committee Bradley Pieters, from the Academic University Medical Center in Amsterdam, the Netherlands, said: “The technology and expertise needed to deliver this treatment is not yet available in all cancer centres.
“However, given that it may offer time and money savings for hospitals as well as benefits to patients, there is a good argument for investing in this type of radiotherapy.”
By Laura Cowen
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