NEW YORKThe final report of a phase II study suggests that the early addition of 13-cis-retinoic acid (isotretinoin, Acutane) to hormone therapy may enhance PSA responses in advanced androgen-dependent prostate cancer. Anna C. Ferrari, MD, of Mt. Sinai School of Medicine, New York, presented the results at the Chemotherapy Foundation Symposium XIX (abstract 58).
A total of 34 hormone-naive patients with stage D1/D2 prostate cancer were given hormone therapy for 1 year. Patients randomized to arm 1 also received isotretinoin(Drug information on isotretinoin) for the first 12 weeks. From weeks 14 to 25, isotretinoin was added to the regimen of arm 2.
After 12 weeks, the median PSA in the early isotretinoin arm had dropped to 0.5 ng/mL and that in the second cohort to 0.7 ng/mL, a difference that was not significant. By week 25, the median nadirs were 0.1 and 0.4 ng/mL, respectively. It remained at 0.1 ng/mL at 36 weeks and 1 year in the early isotretinoin group vs 0.4 ng/mL at 36 weeks and 0.3 ng/mL at the end of the year in the other group.
Complete biochemical responses were achieved by 7 of the 15 patients who received isotretinoin early vs 3 of the 15 given it after crossover. The study was not powered "to determine if this effect was truly due to potentiation of hormone therapy," Dr. Ferrari noted. At all time points, the early isotretinoin patients achieved an undetectable PSA level sooner than controls. By 1 year, more than double the number of patients in arm 1 had achieved an undetectable PSA, and it was sustained for a longer period of time.