Challenges to HBOC Research Enrollment: Competing Cancer Treatment Studies

Posted on March 24, 2014

Research is the key to better medical options. In prior blogs, I outlined some of the barriers to completing hereditary cancer research. This is the next blog in our series about addressing the barriers to hereditary cancer research.

Hereditary cancers make up a small subset of a larger disease state. About 7% of all breast cancer cases and about 18% of ovarian cancer cases are caused by a BRCA mutation. Research has shown that cancers caused by BRCA mutations may behave differently and respond to different treatments than cancers that are not caused by a mutation. So HBOC-specific treatment research is critical. After years of advocacy, new studies are looking at agents that may preferentially benefit people with BRCA mutations. Recruiting enough patients to complete these studies is a significant challenge. Open HBOC-specific clinical trials that desperately need participants must compete with more numerous, larger studies that are not limited to people with mutations.

Clinical trials are important for improving cancer treatment, and it’s important that all studies are completed. However, we need to balance the recruitment of BRCA mutation carriers into more general clinical trials so we don’t deplete the potential pool of participants for BRCA-specific studies. To maximize all clinical trial enrollment, it makes sense to better match patients to clinical trials that are specific and most relevant to their situation.

Breast Cancer Subtypes. The challenge of competing studies is apparent in breast cancer treatment research. Breast cancer is categorized into several different subtypes based on features of the tumor. Some clinical trials are open to one or more subtypes of breast cancer. The main subtypes include:

Breast cancers known as “Her2neu positive” make too much of a protein called Her2/neu which promotes cancer cell growth. These cancers respond to drugs like Herceptin, designed to target the Her2/neu protein. Most BRCA mutation carriers do not develop Her2neu positive breast cancer, so clinical trials focused on Her2neu are less likely to draw from the BRCA positive population.
The most common type of breast cancer are “ER/PR positive.” These cancers have receptors that bind the hormones estrogen and progesterone. These cancers tend to respond to hormonal treatments such as tamoxifen and aromatase inhibitors. About 80% of breast cancer patients with BRCA2 mutations will have ER/PR positive tumors.
“Triple Negative Breast Cancers” (TNBC) do not express estrogen or progesterone receptors and do not overexpress a protein called “Her2neu.” TNBC are usually treated with chemotherapy, and not with hormonal medications or drugs like Herceptin that target the HER2 protein. TNBC are common in women with BRCA1 mutations. About 85% of breast cancer patients with BRCA1 mutations will have TNBC.

Although people with BRCA mutations can develop breast cancer in any of these subtypes, people with mutations tend to develop specific subtypes of breast cancer. As most cancer is not hereditary, mutation carriers make up a minority of the patients in each of these subtypes.

Breast cancer clinical trials. A simplified way to illustrate the issue is to view clinical trials like puzzles that need to be completed…

As potential participants, we make up the puzzle pieces.

A majority of breast cancer clinical trials are open to people with any type of breast cancer, but others enroll only people with specific subtypes. Clinicaltrials.gov, a searchable database run by the National Institutes of Health, lists all clinical trials enrolling patients. A recent search of this database identified 262 U.S. treatment clinical trials for any type of advanced breast cancer.

These trials are open to all breast cancer subtypes, so most women with any type of advanced breast cancer – including mutation carriers – would be eligible.

ER/PR-positive clinical trials. A search on clinicaltrials.gov showed 38 U.S. studies for advanced breast cancer treatment that are open to women with ER/PR-positive breast cancer.

Although these studies will draw from the pool of ER/PR-positive patients, mutation carriers are also eligible to participate, since many BRCA2 and some BRCA1 mutation carriers also have ER/PR-positive tumors.

Triple negative clinical trials. A search of clinicaltrials.gov showed 31 U.S. studies for treatment of advanced breast cancer specifically for women with triple negative breast cancer.