How does Prostate-Specific Antigen (PSA) affect patients taking Duodart (Dutasteride and Tamsulosin)?

From the Guidelines

Duodart, a combination medication containing dutasteride and tamsulosin, significantly reduces PSA levels, with a median decrease of 59.5% after 2 years of treatment, as reported in a study published in The Journal of Urology 1. When taking Duodart, PSA levels generally decrease by approximately 50% after 6-12 months of treatment. This reduction occurs primarily due to dutasteride, which inhibits the enzyme 5-alpha-reductase, reducing dihydrotestosterone (DHT) production and subsequently shrinking prostate tissue that produces PSA. The PSA-lowering effect of Duodart is important for healthcare providers to understand when monitoring for prostate cancer, as it may affect the interpretation of PSA test results. To accurately interpret PSA results while on Duodart, doctors typically double the measured PSA value to compare with pre-treatment baselines or standard reference ranges, although this method may not be reliable for all patients, as noted in a study published in the Journal of the National Comprehensive Cancer Network 1. Patients should inform all healthcare providers about Duodart use before PSA testing and should continue regular prostate examinations as recommended by their doctor, as the medication affects the PSA biomarker but not the actual risk of prostate cancer. Some studies suggest that a PSA increase from nadir of 0.3 ng/ml or greater should be used as an additional biopsy trigger in men receiving a 5ARI for BPH, rather than relying solely on the doubling rule 1. Key points to consider when interpreting PSA results in patients taking Duodart include:

• The median decrease in PSA levels after 2 years of treatment is 59.5% 1
• The PSA-lowering effect of Duodart may affect the interpretation of PSA test results 1
• Patients should inform all healthcare providers about Duodart use before PSA testing 1
• Regular prostate examinations should continue as recommended by the doctor, despite the medication's effect on PSA levels 1

From the FDA Drug Label

In clinical trials, dutasteride reduced serum PSA concentration by approximately 50% within 3 to 6 months of treatment. To interpret serial PSAs in men taking dutasteride, a new PSA baseline should be established at least 3 months after starting treatment and PSA monitored periodically thereafter Any confirmed increase from the lowest PSA value while on dutasteride may signal the presence of prostate cancer and should be evaluated, even if PSA levels are still within the normal range for men not taking a 5 alpha-reductase inhibitor. To interpret an isolated PSA value in a man treated with dutasteride for 3 months or more, the PSA value should be doubled for comparison with normal values in untreated men.

Dutasteride affects PSA levels by reducing serum PSA concentration by approximately 50% within 3 to 6 months of treatment 22. Key points to consider:

• A new PSA baseline should be established at least 3 months after starting treatment with dutasteride.
• PSA should be monitored periodically thereafter.
• Any confirmed increase from the lowest PSA value while on dutasteride may signal the presence of prostate cancer.
• To interpret an isolated PSA value in a man treated with dutasteride for 3 months or more, the PSA value should be doubled for comparison with normal values in untreated men.

From the Research

Effect of Duodart on PSA Levels

• The effect of Duodart (a combination of dutasteride and tamsulosin) on PSA levels is not directly stated in the provided studies, but it can be inferred from the studies that dutasteride, a component of Duodart, affects PSA levels 3, 4, 5.
• A study found that dutasteride reduced the relative risk of prostate cancer diagnosis by 40% compared to tamsulosin monotherapy, and men receiving dutasteride had a numerically lower biopsy rate and higher yield of prostate cancer on biopsy 3.
• Another study found that combined therapy with dutasteride and tamsulosin reduced the relative risk of clinical progression of benign prostatic hyperplasia (BPH) compared to tamsulosin monotherapy, and men with a baseline prostate volume of ≥40 mL and any baseline PSA level of ≥1.5 ng/mL had greater reductions in the risk of acute urinary retention or BPH-related surgery and clinical progression on combined therapy or dutasteride monotherapy than on tamsulosin monotherapy 4.
• A meta-analysis found that dutasteride was better than finasteride in improving the maximum urinary flow rate (Qmax) of patients with BPH, but there was no significant difference in reducing International Prostate Symptom Score (IPSS), improving prostate volume, reducing quality of life, or reducing serum PSA level 5.

Safety Profile of Duodart

• The safety profile of Duodart is consistent with the established profiles of dutasteride and tamsulosin, with no significant differences in adverse reactions compared to finasteride 5.
• However, long-term dutasteride therapy has been associated with undesirable metabolic and sexual adverse side effects, including increased blood glucose, glycated hemoglobin, total cholesterol, and low-density lipoprotein cholesterol, as well as reduced testosterone levels and worsened erectile dysfunction 6.