BRCA1 is a gene that helps repair damaged DNA inside your cells. When it works normally, it acts as a tumor suppressor, catching and fixing the kind of DNA damage that could otherwise lead to cancer. When someone inherits a harmful change (mutation) in this gene, that repair system is compromised, and lifetime breast cancer risk rises to between 45% and 85% by age 70.
What BRCA1 Does in Healthy Cells
Every cell in your body sustains DNA damage on a regular basis. Radiation from the sun, environmental chemicals, and even the normal process of cell division can snap both strands of the DNA double helix. These double-strand breaks are among the most dangerous types of damage a cell can experience, because if they’re not repaired correctly, genetic information gets lost or rearranged.
The BRCA1 protein works inside the cell nucleus as part of a team. It coordinates with other tumor-suppressor proteins and cell-division regulators to locate double-strand breaks and guide a high-fidelity repair process. Think of it as a quality-control supervisor: it doesn’t do all the repair work alone, but without it, the repair crew can’t organize properly. When BRCA1 is functioning, damaged cells either get fixed or are flagged for destruction. When it’s not, damaged cells survive and accumulate more errors with each division, moving them closer to becoming cancerous.
What a BRCA1 Mutation Means
A “BRCA1 mutation” refers to an inherited change in the gene’s DNA sequence that prevents it from producing a working protein. Everyone carries two copies of BRCA1, one from each parent. A single faulty copy is enough to significantly raise cancer risk, because if the remaining good copy gets damaged through normal wear and tear over a lifetime, the cell loses its repair ability entirely.
The mutation follows an autosomal dominant inheritance pattern. If one of your parents carries a harmful BRCA1 variant, you have a 50% chance of inheriting it. This applies equally regardless of whether the carrier parent is your mother or your father, and it affects people of all sexes. Certain populations have higher rates of BRCA1 mutations, including people of Ashkenazi Jewish, Norwegian, Dutch, and Icelandic descent.
Cancer Risks for Women
The cancers most strongly linked to BRCA1 mutations are breast cancer and ovarian cancer. More than 60% of women who inherit a harmful change in BRCA1 will develop breast cancer during their lifetime, according to the National Cancer Institute. Estimates from the American College of Obstetricians and Gynecologists place that range at 45% to 85% by age 70, depending on the specific mutation and family history. For context, the average woman’s lifetime breast cancer risk is about 13%.
Ovarian cancer risk is also substantially elevated. Women in the general population face roughly a 1.2% lifetime risk of ovarian cancer. For BRCA1 carriers, that figure rises to an estimated 39% to 44%. BRCA1-related breast cancers also tend to be diagnosed at younger ages and are more likely to be triple-negative, a subtype that doesn’t respond to hormone-based therapies and is generally harder to treat.
Cancer Risks for Men
BRCA1 mutations affect men too, though the conversation often focuses on women. Male carriers face an increased risk of breast cancer (yes, men have breast tissue and can develop breast cancer), prostate cancer, and pancreatic cancer. The absolute numbers are lower than for women, but they’re still meaningfully higher than for men without the mutation. Male carriers also pass the gene variant to their children at the same 50% rate, so genetic counseling matters for the entire family, not just women.
How BRCA1 Differs From BRCA2
BRCA1 and BRCA2 are often mentioned together, but they’re separate genes on different chromosomes with distinct risk profiles. Both are involved in DNA repair, and mutations in either one raise breast cancer risk to similar overall levels. The key differences show up in the types of cancer and their timing. BRCA1 mutations carry a higher ovarian cancer risk than BRCA2 mutations. BRCA1-associated breast cancers also tend to appear earlier in life and are more likely to be triple-negative. BRCA2 mutations, by comparison, are more strongly associated with male breast cancer, pancreatic cancer, and melanoma.
How Genetic Testing Works
Testing for BRCA1 mutations typically starts with a blood or saliva sample. The lab sequences the gene looking for known harmful variants as well as large deletions or rearrangements that would knock out the protein. Results usually come back as one of three categories: positive (a known harmful mutation was found), negative (no mutation detected), or variant of uncertain significance, meaning a change was found but scientists don’t yet know whether it affects the protein’s function.
Testing is most informative when it starts with a family member who has already been diagnosed with cancer, because finding their specific mutation makes it straightforward to test relatives for the same variant. If no mutation is found in an affected family member, a negative result in a relative is more reassuring. If no affected relative has been tested first, a negative result is harder to interpret, since the family could carry a variant the test didn’t look for.
Risk Reduction Options
Carriers who test positive have several options to reduce their risk, and the choices depend on age, cancer type, and personal priorities.
- Enhanced screening: Breast MRIs and mammograms, often alternating every six months so you’re screened roughly every six months starting in your mid-20s. This doesn’t prevent cancer but catches it earlier, when it’s most treatable.
- Preventive surgery: Bilateral mastectomy reduces breast cancer risk by at least 95% in BRCA1 carriers, according to the National Cancer Institute. Removal of the ovaries and fallopian tubes significantly lowers ovarian cancer risk and also reduces breast cancer risk by cutting off the body’s main source of estrogen.
- Medication: Certain hormone-blocking drugs can lower breast cancer risk in some carriers, though their effectiveness varies depending on the cancer subtype associated with BRCA1.
The timing of these decisions matters. Preventive removal of the ovaries is typically considered after childbearing is complete, often between ages 35 and 40 for BRCA1 carriers, because ovarian cancer associated with BRCA1 can develop earlier than average.
Targeted Treatment if Cancer Develops
The same DNA-repair flaw that makes BRCA1 carriers vulnerable to cancer also creates a treatment opportunity. Cells need multiple repair pathways to survive. When BRCA1 is already broken, blocking a second repair pathway pushes cancer cells past the point of no return.
This is the principle behind a class of drugs called PARP inhibitors. PARP is a protein that fixes single-strand DNA breaks. In normal cells, that’s a backup system. In cancer cells that have already lost BRCA1 function, it’s the only system keeping them alive. When a PARP inhibitor blocks that remaining pathway, the cancer cell accumulates so much DNA damage that it dies. Healthy cells with at least one working copy of BRCA1 can still repair themselves through the other pathway, so they’re largely spared. This selective killing is why PARP inhibitors have become a standard treatment for BRCA1-related breast and ovarian cancers, often after initial chemotherapy or as a maintenance therapy to keep cancer from returning.