Dutasteride, who is it more effective for? Second to fourth digit ratio and the relationship with prostate volume reduction by dutasteride treatment

UNLABELLED: Study Type--Prognosis (cohort) Level of Evidence 2b. What's known on the subject? and What does the study add? The second to fourth digit ratio (hereafter the digit ratio) of the right hand is related to the activity of the androgen receptor. Five α-reductase inhibitor (5ARI) reduces the prostate volume of patients with BPH. In terms of prostate volume reduction, large-scale placebo-controlled studies show that patients with BPH do not always respond well to 5ARI treatment. Patients with a higher digit ratio respond well to dutasteride treatment compared to those with a lower digit ratio. These results suggest that the digit ratio might be a predictor of the response to dutasteride treatment. OBJECTIVE: • To investigate the relationship between second to fourth digit ratio (hereafter the digit ratio) and prostate volume reduction by dutasteride treatment. PATIENTS AND METHODS: • A total of 142 men aged ≥ 40 years with a clinical diagnosis of benign prostatic hyperplasia and an enlarged prostate (prostate volume ≥ 30 mL) were prospectively enrolled. • Before prostate-specific antigen (PSA) level determination and transrectal ultrasonography (TRUS), the lengths of the second and fourth digits of the right hand were measured by an investigator using a digital vernier calliper. • Using TRUS, pre- and post-treatment prostate volume (PV1 and PV2) were measured by an uroradiologist who was unaware of finger lengths. We investigated the change in prostate volume and PSA level at least 6 months after the initiation of dutasteride therapy. RESULTS: • When the patients were divided into two groups according to digit ratio (A: digit ratio <0.95, n = 71; B: digit ratio ≥ 0.95, n = 71), there was a greater reduction in prostate volume in group B compared to group A (PV2-PV1: -9.4 mL vs -13.2 mL, P = 0.042; [PV2-PV1]/PV1: -17.5% vs -24.5%, P = 0.027; [PV2-PV1]/duration: -1.1 mL/month vs -1.6 mL/month, P = 0.041; [PV2-PV1]/PV1/duration: -2.0%/month vs -3.0%/month, P= 0.016). • Significant negative correlations were found between the digit ratio and reduction rate ([PV2-PV1]/duration: r = -0.165, P = 0.049; [PV2-PV1]/PV1/duration: r = -0.191, P = 0.023). CONCLUSIONS: • Patients with higher digit ratios respond well to dutasteride treatment. • The results obtained in the present study suggest that the digit ratio is a predictor of the response to dutasteride treatment.