TOPLINE:

In men with hormone-sensitive metachronous oligometastatic prostate cancer, the use of stereotactic body radiotherapy (SBRT) commonly delayed the need for long-term ADT and provided durable disease control for some. At 5 years, 22.9% of patients were free of radiologic recurrence, and 42.3% remained free of long-term ADT.

METHODOLOGY:

• Long-term ADT has been the standard care for oligometastatic prostate cancer but is linked to unpleasant side effects, as well as cardiac and bone health risks. SBRT can delay the use of long-term ADT and may cure select patients, but the optimal approach to managing oligometastatic disease remains under debate. The study looked at long-term outcomes after SBRT and aimed to identify factors associated with better response.
• Researchers analyzed data on 234 patients (median age, 70 years) with three or fewer hormone-sensitive prostate cancer oligometastases who received SBRT between 2011 and 2023. Overall, 75.2% of patients had a single metachronous oligometastasis, and 58.5% (n = 137) presented with nodal oligometastatic disease.
• The primary endpoint was radiologic progression-free survival (rPFS). Secondary endpoints were ADT-free survival (time from SBRT completion to start of long-term ADT), prostate cancer-specific survival, and overall survival. The median follow-up was 56.5 months.
• A total of 308 lesions were treated, and 59.8% (n = 140) of patients received concurrent ADT (with use and duration determined by the treating clinician). The median radiation dose was 30 Gy in three fractions, with a median biologically effective dose of 230 based on an alpha/beta ratio of 1.5 Gy.

TAKEAWAY:

• Overall, median rPFS was 22 months, while the 5-year rate of rPFS was 22.9%. Median rPFS was 30 months when SBRT was delivered with concurrent ADT compared with 15 months with SBRT alone. That difference was no longer statistically significant after adjustment for time to testosterone recovery — with no difference between the groups in terms of eugonadal rPFS.
• The median long-term ADT-free survival was 42 months, with a 5-year survival rate of 42.3%; median ADT-free survival was longer among patients who received SBRT with concurrent ADT than among those treated with SBRT alone (54 vs 23 months; P < .001).
• In multivariate analyses, prostate-specific antigen doubling time of 3 months or less predicted shorter rPFS (hazard ratio [HR], 1.52; P = .019). Concurrent ADT was associated with improved rPFS (HR, 0.52; P < .001) and improved ADT-free survival (HR, 0.40; P < .001).
• For ADT-free survival, multiple oligometastases (HR, 1.88; P = .002) and baseline nodal disease (HR, 2.08; P = .023) were associated with worse outcomes. Similarly, having more than one metastasis (HR, 6.08; P = .029) or baseline nodal disease (HR, 6.48; P = .033) was associated with worse prostate cancer-specific survival.

IN PRACTICE:

“To our knowledge, this is one of largest published series on SBRT for oligometastases focused solely on prostate cancer,” the authors of the study wrote. The analysis provides “a unique and up-to-date report of outcomes following SBRT,” they added, and it identifies “potential prognostic factors that can inform patient counselling.”

SOURCE:

The study, led by Binnaz Yasar, Royal Marsden NHS Foundation Trust, London, England, was published online in the International Journal of Radiation Oncology, Biology, Physics.

LIMITATIONS:

Because the study was retrospective, many patients lacked recorded testosterone recovery dates, which limited interpretation of eugonadal outcomes. Variation in concurrent ADT duration made it difficult to determine whether the 15-month benefit in rPFS reflects true disease control or prolonged hormone suppression.

DISCLOSURES:

The study received no external funding. Several authors reported receiving grants or personal fees or having other ties with various sources. Full disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.