A91: An investigation of the use and outcomes of Abiraterone and Enzalutamide in patients with metastatic prostate cancer in Cornwall.

Stuart Walter1,Anthony Williams1,Richard Ellis1,Alastair Thomson1,Duncan Wheatley1,James Henderson1,John McGrane1

1Oncology Department, Royal Cornwall Hospital, Truro, UK

Presenting date: Monday 2 November
Presenting time: 12.20-13.10

Background

Enzalutamide and Abiraterone have been shown to have significant clinical and biochemical benefits in the treatment of metastatic prostate cancer (MPC). There have been no head to head studies comparing the efficacy and toxicity of both drugs. We aim to look at our cohort of patients as regards efficacy and toxicity.

Method

A retrospective study of patients treated in the Royal Cornwall Hospital with either Abiraterone or Enzalutamide between September 2011 and March 2015 (Abiraterone n=45, Enzalutamide n=25, Crossover n=6)was performed. Data was collected for age, previous prostate cancer treatment, PSA, clinical response, PSA response and toxicity. This data was then analysed for response rates, duration of treatment and overall toxicity for each treatment group.

Results

70 patients with MPC received either Abiraterone or Enzalutamide between September 2011 and March 2015. The percentage of patients with both clinical and a PSA response was 49% in the Abiraterone and 76% in the Enzalutamide group. Patients with a clinical response and a PSA response >50% from starting PSA was 27% in the Abiraterone group and 40% in the Enzalutamide group. Median duration of PSA response was 16.8 weeks in the Abiraterone and 14.8 weeks in the Enzalutamide group. Toxicity due to treatment was 15% in the Abiraterone group and 12% in the Enzalutamide group. At the end of study follow up 18% of the Abiraterone group and 20% of the Enzalutamide group were still on treatment. The median follow-up period was 96 weeks in the Abiraterone and 52 weeks in the Enzalutamide group.

Conclusion

In our study more patient in the Enzalutamide group had both a clinical and PSA response when compared to Abiraterone. The duration of PSA response was longer in the Abiraterone group albeit this group had longer follow-up. Further studies may help in choosing between these two treatments in the context of MPC.