medwireNews: A one-off post-hoc analysis of the GETUG-AFU 16 study has confirmed the long-term benefit of adding short-term androgen suppression to radiotherapy for salvage treatment in patients with increasing prostate-specific antigen (PSA) concentration after radical prostatectomy.
The study originally found that, at 5 years, significantly more patients who received radiotherapy plus the luteinizing hormone-releasing hormone agonist (LHRHa) goserelin (10.8 mg on day 1 of irradiation and again 3 months later; n=369) were free of biochemical or clinical progression compared with those who received radiotherapy alone (n=374), at 80% versus 62%.
All of the men included in the phase III trial had an ECOG performance status of 0 or 1, stage pT2, T3, or T4a (bladder neck involvement only) and pN0 or pNx prostate cancer, and a PSA concentration that increased from 0.1 ng/mL to between 0.2 ng/mL and 2.0 ng/mL after radical prostatectomy, without evidence of clinical disease.
The median follow-up duration at the time of the current post-hoc analysis was 9.3 years from randomization. During this time, 41% of patients had experienced disease progression or died, Christian Carrie (Centre Léon Bérard, Lyon, France) and co-authors report in The Lancet Oncology.
At 10 years, the risk for disease progression and death was a significant 46% lower for the patients who received radiotherapy plus goserelin relative to those who received radiotherapy alone, with progression-free survival (PFS) rates of 64% and 49%, respectively.
The corresponding 10-year PFS rates for individuals at low- and high-risk for biologic recurrence were 74% versus 61% and 60% versus 43%, respectively.
During the follow-up period, 21% and 28% of patients who did and did not receive androgen deprivation therapy, respectively, developed metastases. The researchers note that these events were not adequately captured in the previous analysis because only the first progression event was recorded, and this may have been local progression.
The current analysis showed that the 10-year metastasis-free survival rate was significantly higher among patients who received radiotherapy plus goserelin compared with those who received radiotherapy alone, at 75% versus 69%.
In line with the earlier findings, there was no significant difference between the two groups in 10-year overall survival, at 86% and 85%, respectively.
However, Carrie and co-investigators point out that “a longer follow-up would be necessary to achieve the required number of events and high enough power to obtain significant results in subgroup and overall survival analyses.”
They add: “Hence, in this specific context, metastasis-free survival appears to be [a] particularly appropriate outcome and has been described as a strong surrogate of overall survival in patients with localised prostate cancer.”
The researchers calculated that, at 10 years, 14 patients would need to be treated to prevent one event (metastasis or death) when adding androgen deprivation therapy to radiotherapy.
In an accompanying comment, Anthony D’Amico, from Harvard Medical School in Boston, Massachusetts, USA, says that until “results of studies that will enable health-care providers who care for men with prostate cancer to personalise the use of androgen deprivation therapy in the salvage setting” become available, the updated GETUG-AFU 16 trial data suggest “it would be prudent to consider adding [an] LHRHa to salvage radiotherapy in men with no or minimal comorbidity given the near halving of progression and the possible reduction in mortality due to prostate cancer.”
By Laura Cowen
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Lancet Oncol 2019; doi:10.1016/S1470-2045(19)30486-3
Lancet Oncol 2019; doi:10.1016/S1470-2045(19)30488-7