Of the 76 patients screened for the LuPSMA trial, 16 (21%) were ineligible because of insufficient PSMA uptake on a PSMA–FDG PET scan. “The majority of patients with this disease are suitable. Probably somewhere in the range of 20% to 30%, depending on how you measure it, may not be suitable,” Dr. Hofman said.
The 50 patients ultimately enrolled had aggressive disease, as indicated by a median PSA doubling time of 2.6 months. Most had previously received abiraterone (Zytiga), enzalutamide (Xtandi), or both (90%), as well as docetaxel (84%) or cabazitaxel (48%). “Many of these men had no further treatment options, and without this study open, they probably would have received end-of-life palliative care,” he said.
The median number of LuPSMA cycles administered was four, according to data reported in the presscast leading up to the symposium. Eight patients received fewer than four cycles because they had an exceptional response, while 10 patients did not complete all planned cycles because of disease progression.
Main results showed that PSA levels fell by at least 30% in 74% of patients, at least 50% in 64% of patients, and at least 80% in 44% of patients. Only two patients did not see any reduction. “We think this is probably a feature of our careful selection of patients with the PET scanning up front to really enrich the study for patients who are likely to benefit from the treatment,” Dr. Hofman said. The reductions in PSA were accompanied by reductions in positive lesions on PSMA–FDG PET.
For the entire cohort, median overall survival was 13.3 months. But it was significantly longer for those with versus without at least a 50% PSA decline (18.0 vs. 8.7 months; P = .001).
Fourteen patients who experienced progression on LuPSMA were given additional doses after the trial ended, as part of an off-trial expanded-access program. Fully 64% of these patients achieved a PSA reduction of at least 50%, and median overall survival in all of the retreated patients was 33 months.
Dr. Hofman disclosed that he has a consulting or advisory role with Endocyte; receives research funding (institutional) from Endocyte; and receives travel, accommodations, and/or expenses from Ipsen and Sanofi. The trial received research funding from the Peter MacCallum Cancer Centre.
SOURCE: Hofman M et al. GUCS 2019, .