Association of HSD3B1 Genotype With Response to Androgen-Deprivation Therapy for Biochemical Recurrence After Radiotherapy for Localized Prostate Cancer

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Abstract

Importance

The variant HSD3B1 (1245C) allele enhances dihydrotestosterone synthesis and predicts resistance to androgen-deprivation therapy (ADT) for biochemically recurrent prostate cancer after prostatectomy and for metastatic disease. Whether this is true after radiotherapy is unknown.

Objective

To determine whether the HSD3B1 (1245C) allele predicts worse clinical outcomes from ADT for biochemical recurrence after radiotherapy.

Design, Setting, and Participants

The Prostate Clinical Research Information System at Dana-Farber Cancer Institute was used to identify the study cohort, which included men treated with ADT for biochemical recurrence after primary radiotherapy between 1996 and 2013. We retrospectively determined HSD3B1 genotype.

Main Outcomes and Measures

Time to progression, time to metastasis, and overall survival according to genotype. Demographic and treatment characteristics were evaluated for confounders. Multivariable analyses were performed to adjust for known prognostic factors.

Results

A total of 218 eligible men were identified, of whom 213 (98%) were successfully genotyped. Of these, 97 of 213 (46%), 96 of 213 (45%) and 20 of 213 (9%) carried 0, 1, and 2 variant alleles. Overall variant allele frequency was 136 of 426 alleles (32%). Median patient age (interquartile range) was 69 (63-74), 72 (65-78), and 69 (65-77) years for 0, 1, and 2 variant alleles (P = .03). Demographic and treatment factors were otherwise similar. During a median follow-up of 7.9 years, median time to progression was 2.3 years (95% CI, 1.6-3.1 years) with 0 variant alleles, 2.3 years (95% CI, 1.5-3.3 years) with 1 variant allele, and 1.4 years (95% CI, 0.7-3.3 years) with 2 variant alleles (P = .68). Median time to metastasis diminished with the number of variant alleles inherited: 7.4 (95% CI, 6.7-9.7), 5.8 (95% CI, 4.9-6.5), and 4.4 (95% CI, 3.0-5.7) years, with inheritance of 0, 1, and 2 variant alleles, respectively (P = .03). Median OS was 7.7 (95% CI, 6.7-10.3), 6.9 (95% CI, 5.8-8.4), and 7.2 (95% CI, 3.8-7.9) years with inheritance of 0, 1, and 2 variant alleles, respectively (P = .31). On multivariable analysis with 0 variant alleles as the reference, the adjusted hazard ratio for metastasis was 1.19 (95% CI, 0.74-1.92) (P = .48) for 1 variant allele and 2.01 (95% CI, 1.02-3.97) (P = .045) for 2 variant alleles. Multivariable analysis did not demonstrate significant differences in TTP or OS.

Conclusions and Relevance

In this study, the HSD3B1 (1245C) allele was associated with more rapid development of metastases in men treated with ADT for biochemical recurrence after primary radiation therapy for prostate cancer. Notably, 105 of 213 men (49%) had received prior ADT, and 119 of 213 (56%) received an androgen receptor antagonist during salvage treatment, both of which may attenuate the effect of the variant allele.

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