NEW YORK--The vinca alkaloid vinorelbine tartrate (Navelbine)
has demonstrated clinical efficacy in hormone refractory prostate
cancer as measured by time to disease progression, performance
status, and pain indices, as well as bone scans and PSA analysis,
Howard A. Burris, III, MD, told Oncology News International.
"One of the problems in dealing with prostate cancer is that
we traditionally evaluate drugs by looking at an objective response
rate. But in prostate cancer, the paucity of patients with measurable
disease has prevented this as an endpoint," said Dr. Burris,
director of clinical research at the Cancer Therapy and Research
Center and director of drug development at Brooke Army Medical
Center, San Antonio.
With chemotherapy producing a steady 10% to 20% response rate,
the focus tends to shift to palliative advantages. Though these
endpoints need to be validated, they do appear to be useful for
evaluating new drugs for hormone refractory prostate cancer, Dr.
In the San Antonio trial, the vinorelbine schedule was 22 mg/m²
IV, weekly for 8 weeks, and then repeated every other week. The
20 patients enrolled averaged more than five cycles or 5 months
of therapy--"a good prognostic sign," Dr. Burris said.
Patients experienced only mild toxicities and brief neutropenia.
A positive response was defined as a greater than 25% change from
baseline in one endpoint. By this measure, six of the 20 patients
were positive responders, producing a clinical benefit rate of
30%--33%, if two patients who discontinued for personal reasons
were not included. Dr. Burris earlier reported these findings
at the Chemotherapy Foundation Symposium XII, sponsored by Mount
Sinai School of Medicine.
The Texas researchers were also encouraged by the fact that nine
other patients experienced stable disease while only three had
truly progressive disease.
All six responders had improvement in Karnofsky status and pain
indices, and three were able to discontinue analgesics entirely.
The range of PSA reductions was wide, between 3 and 80 ng/mL,
probably because some patients enrolled with relatively low PSA
scores, he said.