medwireNews: Treatment with lutetium-177-prostate-specific membrane antigen-617 (LuPSMA) does not significantly prolong overall survival (OS) relative to cabazitaxel, suggest data from the TheraP study of patients with metastatic castration-resistant prostate cancer (mCRPC).
The trial was not powered to assess OS, however, presenting author Michael Hofman (Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia) told the attendees of the 2022 ASCO Annual Meeting in Chicago, Illinois, USA.
And in light of the similar survival outcomes alongside the previously reported significant improvements in endpoints such as prostate-specific antigen (PSA) response and progression-free survival (PFS), as well as the favorable safety profile and dosing schedule, “the TheraP data support the choice of [LuPSMA] over cabazitaxel for patients with PSMA-positive, progressive mCRPC after docetaxel and androgen receptor pathway inhibitors,” said Hofman.
The trial included 200 men who were randomly assigned to receive either up to six cycles of LuPSMA administered at a dose of 6.0–8.5 GBq every 6 weeks or a maximum of 10 cycles of cabazitaxel 20 mg/m2 every 3 weeks.
After a median follow-up of 36 months, there was no significant difference between the LuPSMA and cabazitaxel groups in the intention-to-treat analysis, with restricted mean survival times of 19.1 and 19.6 months, respectively.
This was also the case for the per-protocol analysis, noted the presenter.
He explained that they also applied the restricted mean survival time analysis to PFS (radiographic and PSA) in order to account for nonproportional hazards. The analysis showed that the median duration remained significantly longer among LuPSMA- than cabazitaxel-treated patients, at 7.1 versus 5.0 months, and equated to a hazard ratio for progression or death of 0.62.
Hofman also presented the OS data for the 61 so-called “screen-fail” patients who met all the inclusion and exclusion criteria but were excluded from the trial as a result of low PSMA levels or FDG discordance. Just under half (48%) of these patients received treatment with cabazitaxel.
The median OS by restricted mean survival time analysis for these patients was significantly shorter than that for the randomized patients, at 11.0 and 18.8 months, respectively.
In conclusion, the presenter drew attention to some of the other limitations of the trial, such as the post-protocol crossover, which “limit our ability to see any overall survival difference,” as well as the high rate of withdrawal after randomization in the cabazitaxel arm by men “seeking to have lutetium therapy.”
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