Clinicopathological characteristics of androgen receptor splicing variant 7 (AR-V7) expression in patients with castration resistant prostate cancer: A systematic review and meta-analysis

Background: Studies have shown that AR-V7 may be correlated with the poor prognosis of castration resistant prostate cancer (CRPC), however, clinicopathological characteristics of AR-V7 have not been fully elucidated. Objective: This study aimed at evaluating the clinicopathological features of AR-V7 in CRPC patients. Materials and methods: To evaluate the clinicopathological features of AR-V7 in CRPC patients. A search of PubMed, Embase, and Web of Science was performed using the keywords prostate cancer, prostate tumor, prostate neoplasm, prostate carcinoma, AR-V7, AR3, androgen receptor splicing variant-7, or androgen receptor3. Twenty-four trials published by February 2020 were included in this study. Results: The proportion of Gleason score >= 8 was found to be significantly higher in AR-V7-positive CRPC (69.5%) than negative (54.9%) (OR 1.68, 95% CI 1.25-2.25, p < 0.001), while the rates of T3/T4 stage (OR 1.16, 95% CI 0.60-2.24, p = 0.65) and N1 stage (OR 0.99, 95% CI 0.65-1.51, p = 0.96) were not statistically correlated with AR-V7 status. The AR-V7-positive patients exhibited a significantly higher proportion of any site metastasis (61.3% versus 35.0%; OR 2.19, 95% CI 1.57-3.05, p < 0.001) and bone metastasis (81.7% versus 69.0%; OR 1.97, 95% CI 1.44-2.69, p < 0.001), and a trend close to significance was expected in visceral metastasis (28.8% versus 22.1%; OR 1.29, 95% CI 0.96-1.74, p = 0.09). Incidences of pain in AR-V7-positive CRPC (54.6%) were significantly higher than in negative CRPC (28.1%; OR 4.23, 95% CI 2.52-7.10, p < 0.001), line with worse ECOG performance status (56.7% versus 35.0%, OR 2.18, 95% CI 1.51-3.16, P < 0.001). Limitations of the study include differences in sample sizes and designs, AR-V7 detection assays, as well as disease characteristics of the included studies. Conclusions: AR-V7 positivity is associated with a higher Gleason score, bone or any site metastasis, pain and worse ECOG performance scores in CRPC. However, it is not correlated with tumor stage or lymph node metastasis. More studies are needed to confirm these findings.