STOMP 5-year results confirm potential of metastasis-directed therapy in prostate cancer
medwireNews: Metastasis-directed therapy (MDT) for oligometastatic recurrent prostate cancer continues to be associated with better androgen deprivation therapy (ADT)-free survival relative to surveillance at 5 years, show follow-up findings from the STOMP trial.
These updated data are in line with the previously reported 3-year results that similarly favored MDT over surveillance, presenting author Piet Ost (Ghent University Hospital, Belgium) told delegates of the 2020 Genitourinary Cancers Symposium in San Francisco, California, USA.
He pointed out, however, that the trial was designed as a phase 2 screening trial and although the results are promising, they are not definitive and cannot be considered practice changing.
The study recruited 62 men with rising prostate-specific antigen (PSA) levels and no more than three extracranial metastatic sites after primary curative treatment, and randomly assigned them to undergo MDT – either surgery or stereotactic body radiotherapy – or surveillance.
ASCO expert Robert Dreicer discusses the STOMP trial, as well as other important prostate cancer trials presented at ASCO GU 2020 (3:07).
At the 5-year mark, the primary endpoint of ADT-free survival was achieved by 34% of the MDT group and 8% of the surveillance group, a significant difference that correlated to a hazard ratio (HR) of 0.57 in favor of active treatment.
MDT was associated with an ADT-free survival benefit regardless of the PSA doubling time (≤3 vs >3 months) or location of metastases (nodal vs non-nodal).
Men who received MDT had a reduced likelihood of developing castration-resistant prostate cancer (CRPC), with a 5-year CRPC-free survival rate of 76% versus 53% for men who underwent surveillance (HR=0.62), but the difference did not reach statistical significance in the intention-to-treat analysis.
However, the per-protocol analysis did demonstrate a statistically significant improvement in this endpoint favoring the MDT group, with an HR of 0.51.
Ost reported 5-year overall survival (OS) rates of between 80% and 90%, with just six of the 14 deaths attributed to prostate cancer. Given the generally good outcomes of this patient population, he noted that future trials with OS as an endpoint would need a follow-up period of at least 10 years.
In conclusion, Ost highlighted some of the remaining questions and issues, such as identifying the correct standard of care for patients with oligorecurrent prostate cancer to use as a control in future studies and the ideal endpoints for such trials.
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