We’re learning more and more about how mutations in our DNA influences diseases and about how we treat certain types of cancer.
For some types of cancer, the role of genetics is pretty clear cut: For example, a genetic screening for BRCA 1 and 2 mutations could increase the risk of getting breast cancer from 7% to an average of 55-65%. These kinds of tests look at your “germline” DNA, or the genes that have been with you from the beginning, as opposed to the ones that have been manipulated because of cancer.
For other types of cancer, including prostate cancer, the association between the cancer and genetic mutations is a bit more complicated.
To get a clearer picture, a new study published Wednesday in the New England Journal of Medicine looked at the genetic sequences of about 700 men with advanced stages of prostate cancer to see if there was any way to figure out if genetic mutations could impact the way doctors treat people with advanced metastatic prostate cancer.
They found that at least one of 20 DNA repair mutations that fall in the homologous recombination category, among them BRCA 1 and 2, were present in about 12% of the men sequenced with advanced prostate cancer, compared to those with prostate cancer that had less advanced forms of prostate cancer.
That was a higher percentage than expected, said Dr. Peter Nelson, one of the study’s authors who’s a professor of oncology at the University of Washington School of Medicine and member of the Fred Hutchinson Cancer Research Center.
The takeaways from the study, according to Nelson, were:
- That this should guide what treatments the prostate cancer patients get. Drugs like PARP inhibitors and platinum-based chemotherapy tend to work better in patients with these DNA repair mutations. The PARP inhibitors are a new type of medicine that block a particular enzyme that’s used by our cells to repair DNA so that tumours can’t survive. In certain kinds of cancer, the repair system is broken, which allows cancer cells to thrive. The drugs seem to work particularly well in people with other DNA repair gene mutations like the BRCA mutations, which disable other DNA repair tools.
- It provides some guidance as whether families should get their genes tested to see if their risks were increased for developing cancer.
“The frequency in the general population right now is too low right now to warrant checking everyone,” Nelson said. And even within those with prostate cancer, this is really just for people with advanced forms of the cancer, not for those with sporadic or localised prostate cancer.
But, Nelson said, the hope is to get the genetic screening recommendations changed so that it becomes easier for advanced prostate cancer patients to have that information.
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