ASCO PROSTATE: Satraplatin Plus Prednisone Slows Progression of Hormone Refractory Cancer

KISSIMMEE, Fla., Feb. 23- The investigational drug satraplatin, the first oral platinum-based agent, given with prednisone, significantly slowed the progression of hormone-refractory prostate cancer, albeit briefly, investigators said here.

In absolute terms the benefit of satraplatin plus prednisone in preventing disease progression was only about 10 days. said Daniel Petrylak, M.D., director of the genitourinary oncology program at New York-Presbyterian Hospital at a prostate cancer symposium here.

"Satraplatin prolongs progression-free survival of patients with hormone refractory prostate cancer who have failed either docetaxel or non-docetaxel containing chemotherapy regimens," he said.

The median time to progression in the phase III SPARC (Satraplatin and Prednisone Against Refractory Cancer) trial, with patients randomized to satraplatin-prednisone or placebo-prednisone, was 11.1 weeks in the satraplatin arm versus 9.7 weeks in the placebo arm, (P=0.000003), he reported.

Dr. Petrylak said that progression-free survival was a composite of several endpoints including systemic progression, which was measured by increased pain measured by analgesic consumption or decreased performance status; tumor progression based x-ray, computerized tomography, or magnetic imaging criteria (Response Evaluation Criteria in Solid Tumors [RECIST]); skeletal events including bone fractures; initiation of bisphosphonates, or death.

Dr. Petrylak said that most of the drugs' benefit appeared to come from its ability to prevent recurrence of pain, which was one of the markers of symptomatic progression. He added that even the modest benefits demonstrated in this trial were welcome because "there is currently no standard second-line therapy for these patients."

There were more deaths (9.1% for satraplatin versus 4.7% for placebo) and more skeletal events (4.7% versus 1.8%), but the numbers were too small for meaningful analysis at this point, he said.

Nonetheless, he said that "about a third of the patients who are treated with this drug will get a significant benefit from taking it."

Dr. Petrylak said more detailed results would be reported in June at the annual meeting of the American Society of Clinical Oncology.

The placebo-controlled trial, randomized 635 patients to satraplatin and 315 to placebo. All patients had failed at least two courses of first line chemotherapy. Patients were permitted to continue on prior bisphosphonate therapy.

"Our findings suggest that satraplatin plus prednisone could be a valuable second-line treatment option for men with hormone-refractory prostate cancer," he said.

In the study, symptomatic pain was the cause of progression of disease in 32.4% of patients taking satraplatin compared with 42.7% of men on placebo, (P<0.05), he said.

Dr. Petrylak said the drug was well tolerated with no significant dose limiting toxicities.

"The way I would look at this study is that that a good deal of benefit will be achieved by about one third of the patients," said Tomasz Beer, M.D., of Oregon Health & Science University in Portland. Dr. Beer was not involved in the study.

Dean Bajorin, M.D., of the Memorial Sloan-Kettering Cancer Center in New York, who moderated a press conference briefing during which Dr. Petrylak's study was discussed, said, "At any given point in this study, patients who were taking satraplatin were one-third less likely to progress. That time without progression is clinically meaningful."

Docetaxel (Taxotere) is the only FDA-approved first line therapy for hormone-resistant prostate cancer and there is no approved second-line treatment. A spokesperson for GPC Biotech, which developed satraplatin, said a clinical trial of docetaxel plus satraplatin as first-line therapy was under way.

GPC Biotech has submitted an NDA to the FDA for satraplatin in combination with prednisone as second-line chemotherapy.