Finasteride reduces the risk of getting prostate cancer by 25 per cent and can shrink an enlarged prostate. It has now been found that it could also shrink prostate tumours, making the prostate smaller and helping to reveal cancer.
The study appeared online Wednesday ahead of print publication in the Journal of the National Cancer Institute. It was conducted by the Southwest Oncology Group headquartered at the University of Michigan.
"It appears that a man concerned about prostate-cancer risk, who is having a PSA (prostate-specific antigen) test on a regular basis, will not only reduce his risk of prostate cancer if he takes finasteride, but will help find the cancers that pose the highest risk," Ian Thompson, the study's senior author and a urologist at the University of Texas Health Science Center in San Antonio, said in a release.
In the past, some studies have linked finasteride to an increase in fast-growing, aggressive prostate cancers.
In 2003, the Southwest Oncology Group closed a seven-year trial and released contradictory findings.
On the one hand, the drug cut a man's risk of developing the disease by one-fourth.
But the study also found that the men who took the drug but still developed cancer by the end of the study had higher rates of detected high-grade tumours that were difficult to treat.
Concerned about whether finasteride was leading to biological changes that became cancer, researchers devised a follow-up study to determine what was leading to the aggressive cancers in some men taking the medication.
Researchers analyzed tissue from 528 prostatectomy specimens of participants 222 taking 5 mg/day of finasteride and 306 on placebo. They compared biopsies in men in the finasteride and placebo groups to compare hormonal levels and the spread of the disease.
They also compared prostate size at the time of biopsy in the two groups, then examined tumour grade and spread in men in the study who went on to have their prostates removed.
They found no significant differences in degenerative hormone changes when they examined high-grade tumour biopsies in men in both groups.
However, researchers found that the men taking finasteride had smaller prostates and their biopsies correctly identified a higher proportion of high-grade tumours found later when their prostates were removed, compared to men in the placebo group (69.7 per cent versus 50.5 per cent).
The new study found that finasteride improves the effectiveness of the screening tests and biopsies.
"Finasteride makes the PSA test perform better, so we can find the cancer earlier," Thompson said. "Our current study also shows that by shrinking the prostate gland, finasteride makes a biopsy more sensitive for any cancers that are present."