Do Drugs for Benign Prostate Enlargement Increase Cancer Risk?

Commonly known as benign enlargement of the prostate , the condition benign prostatic hyperplasia (BPH) is a common problem among middle-aged and older men and can seriously reduce quality of life. Thanks to easy access to diagnostic tests such as ultrasound and the availability of effective drugs, BPH has become an easily manageable disease, even treated by family physicians in some countries (BPH treatment in detail).

Prostate cancer is among the most common cancers in men worldwide, causing an estimated 1 million 600 thousand new cases and 366 thousand deaths each year. In the United States, for example, 11 percent of men are diagnosed with prostate cancer during their lifetime, and this rate generally increases with age.

The five-year survival rate for prostate cancer is around 98 percent. When such an important disease affects millions, naturally people also wonder about its causes and factors that increase its risk . Some known risk factors for prostate cancer include a family history, carrying a BRCA2 mutation , older age and a Western diet. One controversial issue concerning prostate cancer risk involves finasteride and dutasteride, drugs for benign prostate enlargement, which is common in men.

Finasteride and dutasteride reduce symptoms caused by benign prostate enlargement by blocking the conversion of testosterone into dihydrotestosterone, a more potent androgen (male hormone). They are 5a-reductase inhibitors (5-ARI). Androgens have been known for decades as the main driving force of prostate carcinogenesis (cancer formation). Two previous large randomized controlled clinical trials investigated the effects of finasteride (PCPT) and dutasteride (REDUCE) use on prostate cancer risk.

Both studies showed that, in men treated with 5-ARI, the risk of prostate cancer on biopsy, compared with those receiving placebo , decreased by % 25 and % 23, respectively . However, these studies found increased rates of high-grade prostate cancer (Gleason score 8 to 10) with finasteride and dutasteride, by % 0.7 and % 0.5, respectively. In light of these findings, the United States Food and Drug Administration (FDA) warned about the potential for 5-ARI use to increase the risk of high-grade prostate cancer, issuing a safety warning in 2011. This advice led some physicians to prescribe finasteride and dutasteride less often to patients who might benefit. However, subsequent analyses of the PCPT study found that finasteride increased the detection rate of high-grade prostate cancer by shrinking the prostate, thus introducing potential overdiagnosis bias. Moreover, in the 18-year follow-up of PCPT, there was no statistically significant difference in survival rates between the groups.

In current clinical practice, many men are treated with finasteride and dutasteride for benign prostate enlargement. Given the drugs’ widespread use and the FDA safety warning, further studies were needed to clarify the conflicting findings described above. The study discussed in this article, published in November 2018 in the Journal of the National Cancer Institute , was conducted for this purpose. This analysis is the largest population-based prospective (forward-looking) study representing contemporary clinical practice to evaluate prostate cancer risk in men who regularly use 5-ARI.

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Details of the Study

• All men participating in the study were aged 40 or older.
• At the start of the study, all participants had at least one known serum prostate-specific antigen (PSA) value.
• The study was conducted in Stockholm, Sweden’s capital and largest city, between 2007 and 2015.

Study Results

• Of the 333 thousand men evaluated, 23442 (%7), at some point during the 8-year study period, had taken 5-ARI, drugs for benign prostate enlargement.
• 5-ARI treatment was found to reduce prostate cancer risk overall. Longer use of drugs for benign prostate enlargement reduced the risk further: for 0.1-2 years of use, the risk reduction was %19; for 2-4 years, %61; for 4-6 years, %60; and for 6-8 years, %69.
• A subgroup analysis found that 5-ARI use in those with Gleason scores of 6 and 7 substantially reduced the risk, whereas it did not affect risk in those with high Gleason scores (8-10).

Conclusion

Treatment with finasteride and dutasteride, drugs for benign prostate enlargement, both effectively reduces urinary symptoms and is safe in terms of prostate cancer risk.

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