From Breast to Prostate Cancer:
Learning More About Genetic Links
by Gina Shaw
If you’re a woman whose mother, grandmother or sister was diagnosed with breast cancer at a relatively early age, you probably are all too aware that you may be at an increased risk of breast and ovarian cancer yourself. But what if you’re a man with a strong family history of breast cancer? Does it affect you? It might, if that family history is linked to a genetic mutation.
Scientists are learning more about the connection between the genetic mutations that lead to an increased risk of breast and ovarian cancer (the most significant being mutations on the BRCA1 and BRCA2 genes) as well as cancers that affect men.
In early September, researchers at the Netherlands Cancer Institute published the results of a study showing that a mutation in the BRCA2 gene that increases the risk of breast and ovarian cancer in women may also increase the odds of prostate, pancreatic, bone and throat cancer in men.
In the Dutch study, which examined 139 families with 66 different mutations of the BRCA2 gene, men with a BRCA2 mutation were more than twice as likely to have prostate cancer, a
lmost seven times more likely to have pharyngeal cancer and eight times as likely to have pancreatic cancer. The researchers found that most of the increases were significant for men only, and particularly for those under age 65.
This isn’t exactly news, said Dr. Patrick Walsh, professor of urology at Johns Hopkins Brady Urological Institute and one of the world’s leading experts on prostate cancer. “We’ve known for some time that BRCA2 mutations are associated with prostate cancer,” he said. “I have a prostate cancer patient in the hospital now who is 50 years old; his mother died of BRCA-linked breast cancer when she was 46 years old. The data do indicate that there’s an increased risk of prostate cancer for men who have a first-degree female relative who developed breast cancer at a very young age.”
But when a woman is diagnosed with breast cancer at such a young age, families and doctors still tend to think about genetic testing and increased vigilance for her sisters and her daughters—not her brothers and her sons. “I don’t think people do” focus on the potential increased risk of prostate and other cancers for a man whose mother or sister has had BRCA2-linked breast cancer, said Walsh.
Part of the problem is that there’s still not a lot of consensus as to what these men should do. The Dutch scientists, led by Netherlands Cancer Institute head of epidemiology Flora E. van Leeuwen, suggest that since 11 of the 24 men in the study who had prostate cancer had died, doctors should consider early, radical treatment for men carrying the mutated gene.
“The observed risks for prostate cancer may warrant consideration of male carriers as candidates for inclusion in high-risk prostate screening studies,” the researchers wrote. “However, screening for prostate cancer is controversial.”
That’s an understatement. Experts have pointed out that we still don’t know whether prostate cancer screening actually reduces the risk of death from the disease. The PSA (prostate-specific antigen) test, still the standard screening tool for detecting prostate cancer, has many limitations. It may miss faster-growing cancers that can be deadly, while uncovering slower-growing cancers that pose little danger.
Because prostate cancer is so common, and so many cases are “indolent”—sitting quietly in the body and doing little damage—for so long, doctors worry that the quadrupling of men diagnosed with the disease since the PSA test was developed could simply mean that more men are going through biopsies and surgeries when they don’t need to.
On the other hand, a study done in 2004 at the University of Texas Health Science Center in San Antonio found that 15 percent of the men who had “normal” PSA levels still had prostate cancer—2.3 percent of them a high-grade cancer. Studies have also found that PSA results can fluctuate over time. (Doctors are moving away from the idea that there is a “magic number” on the PSA test that indicates cancer, and instead focusing on how fast PSA levels are rising.)
So if a young man, worried because his sister developed breast cancer at an early age, gets tested for the BRCA2 mutation and finds that he is indeed a carrier, there’s not a lot of evidence yet to tell him what to do next. And if he does develop prostate cancer, do the relatively high mortality figures in the Dutch study indicate that he should indeed think about more aggressive treatment than the next guy who has the same cancer but without the genetic mutation? Experts say we’re a long way from being able to make that determination.
“I think the study tells us something we knew, but you need a clinical study before you can use this,” Debbie Saslow, director of breast and gynecologic cancer at the American Cancer Society, told Forbes magazine. “We now have to see if it makes clinical sense to do anything with this information.”
Still, the growing body of evidence documenting increased risk of prostate and other cancers in men with a family history of BRCA2-linked breast and ovarian cancer should remind us that it’s not just women who need to be particularly vigilant when these cancers seem to run in the family.
Gina Shaw is the medical writer for The Washington Diplomat.
