Abstract 3476: Intermittent anti-androgen monotherapy: a possible treatment for androgen receptor-overexpressing prostate cancer

Abstract

Abstract A case report of a Gleason 4+4 patient who self-medicated on intermittent flutamide with 14 cycles of 3 months on 3 months off, surviving at 14 years.cast doubt on conventional wisdom that intermittently androgen blockade should include an LHRH blocking agent. Anti-androgen(aa) monotherapy was thought to be dangerous as on treatment testosterone rises. It was speculated that he had been Testosterone(T) deficient at diagnosis as in many patients with high grade tumours and had benefited from the blocking action of the aa to control tumour expansion while allowing the off period to allow T to differentiate the tumour possibly by suppressing an over expressed androgen receptor. Following this case others already on AA continuously were recruited to our then ongoing phase 1/2 study of intermittent hormone therapy(Lane 2004). This abstract records their outcome and compares it with those treated with conventional GNRH monotherapy or maximum androgen blockade Results: Between 1997 and 2007 111 patients sort advice about intermittent hormone therapy having started on some form of endocrine treatment. 46 MO patients received GNRH regime and 33 receive aa monotherapy (M0 = 31). Provided PSA was below 4 they were eligible for entry. Median pre-treatment PSA was 22 (range 0.4-237) compared to 22 (range 3.7-402) in MO GNRH groups. Over all survival was 87% ,at 5 year and 78% at 8 years and continuing to respond on protocol 66% at 5 yrs, 57% at 8 compared to 77/56% at 5 and 54/41% at 8 years in M0 GNRH treated group Conclusion: Non-randomised selection in this cohort makes it difficult to draw strong conclusions. As overall survival is significantly better than with GNRH regimens, an exploratory randomised phase 2 trial comparing GNRH against aa monotherapy in patients presenting with over expression of androgen receptor and below normal age-corrected serum testosterone is under consideration Citation Format: Tim Oliver, Dan Berney, Greg Shaw. Intermittent anti-androgen monotherapy: a possible treatment for androgen receptor-overexpressing prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3476. doi:10.1158/1538-7445.AM2015-3476