ASCO GU 2018: Abiraterone Acetate in Patients Aged 75 or More with mCRPC in Both Pre-chemotherapy or Post-chemotherapy Settings

San Francisco, CA (UroToday.com) Prostate cancer (PC) affects a significant proportion of elderly patients, harboring a substantial burden of additional comorbidities. Abiraterone acetate (AA) is a selective androgen synthesis inhibitor that showed efficacy in both chemotherapy (CT) naive pts and those pretreated with docetaxel. The overall good tolerability of this treatment make it an attractive choice for elderly metastatic castrate resistant prostate cancer (Mcrpc) patients. The authors assessed and reported the utilization of this treatment among elderly PC patients, older than 75.

Methods:
The authors retrospectively collected data regarding mCRPC patients aged ≥75 years treated with AA in 13 Italian Centers from April 2013. The median age was 79 years (range 75-90) with 48% of patients being octogenarians. Post CT pts had more extensive disease, higher baseline PSA and ECOG PS. Nearly all the pts had comorbidities, the most frequent being hypertension present in 146 pts (58%), and the second ost frequent being diabetes type 2, present in 43 pts (17%). The authors evaluated duration of the AA treatment, overall response rate (ORR), 50% PSA decline, time to progression (TTP) and overall survival (OS). Furthermore, the all toxicities observed were reported.

Results:
A total of 252 pts ,147 pre treated with docetaxel and 105 chemo naive, were included in this analysis. Median duration of treatment with AA was 8.6 months in post CT and 11.5 in CT naive pts. ORR was 35,3% in pre-docetaxel and 27,4% in post docetaxel group. 64 pts (65%) and 51 pts (46%) obtained 50% PSA reduction in pre and post docetaxel group, respectively. Median TTP was 8.6 in post docetaxel and 11.9 in CT naive pts. A median OS of 13.8 months in post CT group was observed, while for CT naive pts, data were not yet mature. AA was well tolerated with only 8 pts (3.2%) who discontinued treatment due to toxicity, while in 4 pts (1.6%) temporary dose reductions were performed. The most frequent grade 3 toxicities noted were hypertension and liver toxicity with 4 pts (1.6%) and 5 pts (2%), respectively. After progressing on AA, 85 pts (34%) received at least one subsequent treatment. At the end off the study follow-up, 40 pts (15,9%) were still on treatment with AA.

Conclusions:
Despite the high comorbidity rate, only a small proportion of elderly patients had discontinued AA treatment due to toxicity, validating that AA is a well-tolerated and efficient treatment for elderly patients.

Presented by: Zuzana Sirotova

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA
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