Collaborative work has shown that approximately 12% of men with advanced prostate cancer have inherited, or germline, DNA-repair mutations that disrupt the normal function of the genes involved in repairing damaged DNA. Somatic alterations in DNA-repair pathways are also common in prostate cancer, particularly in late-stage disease. Somatic alterations affect only tumor cells, but are not inherited or passed on. Inherited mutations in DNA-repair genes – such as BRCA2, ATM, and CHEK2 – are associated with an increased risk of several other cancers as well as prostate cancer, including breast, ovarian, and pancreatic cancer. In particular, mutations in BRCA2, associated with 1.8% of overall prostate cancer cases, have been associated with more aggressive prostate cancer characteristics and worse outcomes, including increased risk of recurrence and poorer overall survival rates.
As a result of the increasing number of men with these types of mutations, the National Comprehensive Cancer Network (NCCN) guidelines have recently changed, now recommending genetic testing for all men with metastatic prostate cancer.
“Genetic testing for inherited mutations may provide some men with prognostic information about their prostate cancer risk,” says Dr. Scott Tagawa, Director of the Weill Cornell Medicine and NewYork-Presbyterian Genitourinary (GU) Oncology Program. “Even more importantly, genetic testing can also be used to inform screening of family members and may increasingly inform precision-medicine based approaches to manage the disease using specific molecular features such as DNA-repair genes,” says Dr. Tagawa.
How do Inherited Mutations Impact Treatment?
Clinical research studies are continually being conducted to investigate new ways to treat advanced prostate cancer patients with germline DNA-repair mutations since these patients comprise a unique subset of patients. Currently, little has been known about whether DNA-repair mutation status impacts benefit from standard therapies for the disease and this is just one area that needs to be researched in order to specifically tailor treatment options for this subset of patients.
Weill Cornell Medicine and NewYork-Presbyterian’s Drs. Himisha Beltran, Scott Tagawa and David Nanus, along with collaborators from around the globe, address this in research published today in the high impact factor journal European Urology and simultaneously presented at the American Society of Oncology (ASCO) 2018 Genitourinary (GU) Cancers Symposium by Dr. Misha Beltran. The researchers reviewed 390 medical records of patients who previously participated in a New England Journal of Medicine (NEJM) study examining men with advanced prostate cancer with known germline DNA-repair mutations and those without these mutations. The goal of the research was to determine whether germline mutations in DNA-repair genes impact the benefit of standard therapies for metastatic prostate cancer, such as docetaxel chemotherapy and androgen receptor signaling inhibitors abiraterone acetate and enzalutamide. Results showed that all patients appeared to benefit from standard therapies similarly to other metastatic prostate cancer patients, regardless of germline mutation status.
“The data suggest that metastatic prostate cancer patients with inherited mutations in DNA damage repair genes, including those with BRCA2 mutation, derive similar benefit from standard of care therapies in terms of both response rate and progression-free survival,” says Dr. Scott Tagawa. “While we continue to investigate additional agents thought to preferentially benefit those with DNA repair alterations, current evidence indicates that detection of any of these mutations should not prevent metastatic prostate cancer patients from receiving standard therapies including taxanes, abiraterone and enzalutamide, as standard of care treatment.”
Additionally, sophisticated genetic analysis and testing may be performed by genetic counselors and widely-available commercial testing is also available to physicians and patients. Dr. Panagiotis Vlachostergios, fellow and medical oncologist at Weill Cornell Medicine and NewYork-Presbyterian, presented research at ASCO Genitourinary (GU) Cancers Symposium focused on using a commercial 30-gene panel to test men with localized prostate cancer and advanced prostate cancer for the presence of inherited gene mutations. Out of the 17 men with localized disease and 35 men with metastatic prostate cancer, eight of 52 (15%) were found to have a germline alteration. A higher percentage of men with an inherited mutation had localized (23.5%) versus advanced disease (11.4%), though testing might have been biased towards those with family history of cancer or those diagnosed with high-grade cancer at earlier age.
Both the results published in European Urology and research presented at the 2018 ASCO GU Cancer Symposium underscore the importance of genetic testing to determine what, if any, mutations may be present in prostate cancer in order to determine the best possible treatment options. While the published data supports the use of standard therapies in those with metastatic prostate cancer who have germline DNA-repair mutations, not all patients respond to these types of treatment, demonstrating the need for alternate treatment options for this patient population. Weill Cornell Medicine and NewYork-Presbyterian are in the process of opening several clinical trials to include men with prostate cancer in need of different lines of therapy. Clinical trials testing PARP inhibitors, a drug target for cancer therapy that appears to be more effective in prostate cancer patients with DNA-repair mutations, are ongoing and may offer additional therapy options for this group of patients in the near future.