Detection of Androgen Receptor (AR) Splice Variants Across Diverse Prostatic and Non-Prostatic Tumor Types Using the TruSight Oncology 500 (TSO500) Assay.

BACKGROUND: Androgen Receptor splice variants (AR-Vs) are known biomarkers of resistance to hormone therapy in prostate (CaP) and breast cancer (BC). However, pancancer interrogations of AR-Vs are lacking. METHODS: The MayoComplete Solid Tumor Panel, with DNA and RNA subpanels targeting 515 and 55 genes, respectively, was used to profile 5,573 solid tumors. Relevant clinicopathologic and molecular features were summarized for tumors with detectable AR-Vs. RESULTS: AR-Vs were identified in 46 of 5,573 (0.8%) tumors from 28 males and 18 females with a mean age of 68 years (range, 11 to 98). AR-Vs were enriched in CaP (24/132, 18.2%), BC (17/208, 8.2%), and salivary duct carcinomas (2/38, 5.3%), with rare occurrences in a lacrimal gland carcinoma and juvenile granulosa cell tumor. While AR-V7 was observed in all 46 tumors (100%), AR-V7 in the absence of other AR-Vs was seen in only 2 (of 46, 4.3%) tumors. Associated AR alterations in CaP included AR amplification (n=3) and AR ligand binding domain (LBD) mutations (n=2), while associated ESR1 variants in BC included ESR1 LBD mutations (n=2) and ESR1 rearrangements (n=2). Of patients with accessible medical records, 2/8 (25%) CaP patients had AR-Vs post-therapy with AR signaling inhibitors. Similarly, 5/6 (83.3%) BC patients had AR-Vs post-hormonal therapy. Notably, all 14 patients had multiple AR-V species. CONCLUSIONS: Our results demonstrate enrichment of AR-Vs in prostate, breast, and salivary duct carcinomas, with rare occurrences in a lacrimal gland carcinoma and juvenile granulosa cell tumor. Multiple AR-Vs were frequently seen in the same tumor. Detection of AR-Vs may be clinically significant in prostate cancer and additional data is needed for other tumor types.