Homologous recombination deficiency (HRD) positive advanced ovarian cancer is a specific type of ovarian cancer where the body’s natural DNA repair system cannot fix damaged genetic material properly, making these tumors more vulnerable to certain targeted treatments.
Understanding the Disease
When cells in our body grow and divide, their DNA can sometimes break. Normally, our body has several repair systems to fix these breaks and keep our genetic information healthy. One of the most important repair systems is called homologous recombination repair, which fixes a particular type of DNA damage known as double-strand breaks. This repair system works by using a second, undamaged copy of the gene as a template to restore the DNA correctly.
In some ovarian cancers, this repair system doesn’t work properly. This failure to repair DNA damage efficiently is called homologous recombination deficiency, or HRD. When the body cannot repair these breaks in DNA, other less accurate repair systems take over. Over time, these less precise repairs lead to an accumulation of genetic errors and mutations throughout the cell’s DNA. These mounting errors eventually cause cells to grow uncontrollably and become cancerous.[1][4]
The inability to repair DNA might seem like a purely negative thing, but it actually creates a unique vulnerability in these cancer cells. This weakness can be exploited by specific treatments, particularly a class of drugs called PARP inhibitors and platinum-based chemotherapy. Understanding whether an ovarian cancer has HRD is therefore crucial for treatment planning.[1][12]
How Common is HRD-Positive Advanced Ovarian Cancer?
Ovarian cancer is the eighth most common cancer among women worldwide, with over 295,000 women diagnosed each year. The disease carries significant risks, as approximately 75% of patients are diagnosed when the cancer has already reached an advanced stage, meaning it has spread beyond the ovary.[6]
Among patients with high-grade serous ovarian cancer—which is the most common and aggressive subtype of ovarian cancer—HRD is surprisingly common. Research shows that approximately 50% of women with advanced ovarian cancer have tumors that test positive for HRD. This means that nearly half of all advanced ovarian cancer patients could potentially benefit from HRD-targeted treatments.[2][3][6]
In China specifically, ovarian cancer is the third most common gynecologic cancer, with more than 55,000 new cases diagnosed in 2020. The five-year survival rate is approximately 39%, with more than 70% of women diagnosed with advanced disease. Among Chinese patients with high-grade serous ovarian carcinoma, the prevalence of HRD appears similar to other populations worldwide.[8][11]
What Causes HRD-Positive Ovarian Cancer?
HRD develops when there are problems with genes that control the homologous recombination repair system. The most well-known causes are mutations in the BRCA1 and BRCA2 genes. These genes normally produce proteins that help repair damaged DNA. When BRCA genes have mutations, they cannot produce functional repair proteins, leading to HRD.[4]
However, BRCA mutations tell only part of the story. While these mutations are critical, they account for only about half of all HRD-positive cases. The other half of HRD-positive tumors arise from different causes. Several other genes beyond BRCA1 and BRCA2 are also associated with HRD, including ATM, CHEK2, RAD51B, RAD51C, RAD51D, PALB2, BRIP1, BARD1, FANCL, CDK12, and RAD54L. Mutations or problems with any of these genes can disrupt the DNA repair process.[2]
In addition to genetic mutations, epigenetic factors—changes that affect how genes work without altering the DNA sequence itself—can also cause HRD. For example, some cancers silence the BRCA1 gene through a process called methylation, preventing it from being read and used by the cell even though the gene itself isn’t mutated.[2]
This complexity means that even if a patient tests negative for BRCA mutations, their tumor could still be HRD-positive due to other genetic alterations or epigenetic changes. This is why comprehensive HRD testing that looks beyond just BRCA mutations is so important.[2][3]
Risk Factors
The risk factors for developing HRD-positive ovarian cancer overlap significantly with general ovarian cancer risk factors, but certain elements specifically increase the likelihood of having HRD.
Family history plays a major role. If you have close family members—including mothers, sisters, daughters, or even fathers and brothers—who have had ovarian or breast cancer, your risk increases. This is because BRCA mutations and other genetic changes that cause HRD can be inherited from either parent. Even though ovarian cancer affects only people assigned female at birth, both parents can carry and pass on the genes that increase risk.[3]
Genetic mutations in the BRCA1 and BRCA2 genes are recognized to cause approximately 10% of all ovarian cancers. Women who inherit these mutations have significantly elevated risks not only for ovarian cancer but also for breast cancer. However, having a BRCA mutation doesn’t guarantee that someone will develop cancer—it means the risk is substantially higher than in the general population.[4]
Age is another important factor, as ovarian cancer generally occurs more frequently in older women. Most cases are diagnosed in women who are postmenopausal. The advanced stage at diagnosis—which affects three-quarters of patients—is partly because early ovarian cancer often causes few or no symptoms, making early detection challenging.[6]
Symptoms
The symptoms of HRD-positive advanced ovarian cancer are generally the same as other types of advanced ovarian cancer. Unfortunately, these symptoms tend to be vague and can easily be mistaken for less serious conditions, which is one reason why so many cases are diagnosed at advanced stages.
Women with advanced ovarian cancer may experience persistent bloating or a feeling of fullness in the abdomen, even after eating small amounts of food. This occurs because the tumor can grow large or because fluid accumulates in the abdominal cavity. Abdominal or pelvic pain is also common, ranging from a dull ache to sharp discomfort.
Changes in eating patterns often occur, with many women finding they feel full quickly during meals or experience a loss of appetite. Urinary symptoms can develop, including needing to urinate more frequently or feeling an urgent need to urinate. Some women notice changes in their bowel habits, such as constipation or diarrhea that persists beyond normal digestive upsets.
Fatigue is another frequent symptom, as the body works to cope with the cancer. Some women experience unexplained weight loss, while others may notice their abdomen increasing in size due to tumor growth or fluid accumulation. Back pain can also be a symptom, particularly if the cancer has spread.
These symptoms are troublingly nonspecific, meaning they could be caused by many different conditions. However, if symptoms persist for more than a few weeks or worsen over time, medical evaluation is important. While these symptoms don’t necessarily mean cancer is present, persistent symptoms warrant thorough investigation.
Prevention
Preventing HRD-positive ovarian cancer entirely is challenging because many cases are linked to inherited genetic factors that cannot be changed. However, certain strategies can help reduce risk or detect cancer earlier when it may be more treatable.
For women with a strong family history of ovarian or breast cancer, genetic counseling and testing can be valuable. Genetic testing examines specific inherited genes in your DNA, such as BRCA1 and BRCA2, to identify potential risks. This testing is typically done using a blood or saliva sample. If you carry high-risk mutations, your healthcare team can discuss enhanced surveillance strategies or preventive measures.[3]
Some women with known BRCA mutations and high cancer risk choose to undergo preventive surgery to remove their ovaries and fallopian tubes (called a prophylactic salpingo-oophorectomy) after they have completed their families. This significantly reduces the risk of developing ovarian cancer, though it doesn’t eliminate the risk entirely since a type of cancer called primary peritoneal cancer can still develop.
Oral contraceptives (birth control pills) have been shown to reduce ovarian cancer risk in the general population. Women who use oral contraceptives for several years have a lower risk compared to those who never used them. However, oral contraceptives carry their own risks and benefits that need to be carefully discussed with a healthcare provider.
Maintaining a healthy lifestyle may contribute to overall cancer prevention. This includes maintaining a healthy weight, staying physically active, eating a balanced diet rich in fruits and vegetables, and avoiding tobacco products. While these measures cannot prevent all ovarian cancers, they support overall health and may reduce some cancer risks.
Regular check-ups with your healthcare provider are important. While there is no reliable screening test for ovarian cancer in the general population, women should discuss any persistent or concerning symptoms with their doctor. For women at high risk due to family history or genetic mutations, more intensive monitoring might be recommended.
How HRD Affects the Body
Understanding how HRD affects the body requires looking at what happens at the cellular level when DNA repair systems fail. Every day, our cells face numerous challenges that can damage DNA. These challenges include natural metabolic processes, exposure to environmental factors, and errors during cell division. Healthy cells have multiple backup systems to detect and repair this damage.
The homologous recombination repair system is specifically designed to fix double-strand breaks—situations where both strands of the DNA double helix are severed. This is one of the most dangerous types of DNA damage because if left unrepaired, it can lead to cell death or cancer. The system works by finding a matching, undamaged section of DNA to use as a template for accurate repair, much like using a backup copy of a document to restore a corrupted file.[4]
When the homologous recombination system is deficient—as it is in HRD-positive cancers—cells must rely on alternative, less accurate repair mechanisms. One such system is called non-homologous end joining (NHEJ), which simply joins broken DNA ends together without using a template. While this prevents immediate cell death, it often introduces errors because the repair isn’t precise. Another backup system involves enzymes called PARP (poly ADP-ribose polymerase), which help repair single-strand breaks in DNA.[2]
Over time, the accumulation of imperfectly repaired DNA leads to genomic instability—a state where the cell’s genetic material becomes increasingly chaotic. This instability creates characteristic patterns called genomic scars, which leave permanent footprints in the DNA that can be measured. These scars reflect the history of faulty DNA repair and include patterns such as loss of heterozygosity (where one copy of a gene is lost) and large-scale state transitions (where large segments of chromosomes show altered patterns).[2][4]
This genomic chaos eventually enables cancer cells to grow uncontrollably, evade normal growth controls, and spread to other parts of the body. However, the same deficiency that allows cancer to develop also creates a specific vulnerability. Cells with HRD become extremely dependent on their remaining DNA repair pathways, particularly PARP enzymes. If these remaining repair systems are also blocked—for example, by PARP inhibitor drugs—the cancer cells accumulate so much DNA damage that they die. Normal cells, which have intact homologous recombination repair, can survive without PARP because they have other effective repair options.[2][12]
Diagnosis and Testing
Determining whether an ovarian cancer is HRD-positive requires specialized testing that goes beyond standard diagnostic procedures. Once ovarian cancer has been confirmed through pathologic analysis of a biopsy or surgical specimen, additional testing can reveal the tumor’s HRD status.[6]
HRD testing is performed on tumor tissue samples, which can be obtained during surgery or through a biopsy procedure. In many cases, healthcare teams can use tissue from the original biopsy or surgery that confirmed the cancer diagnosis, meaning patients may not need an additional procedure specifically for HRD testing. The test examines the DNA in the tumor cells to look for specific characteristics.[3][13]
Modern HRD tests typically assess three main components. First, they check for mutations in BRCA1 and BRCA2 genes within the tumor. Second, they measure genomic scarring patterns that indicate long-term DNA repair problems. These patterns include genomic loss of heterozygosity (gLOH) and large-scale state transitions (LST). Some tests also measure a third pattern called telomeric allelic imbalance (TAI). Together, these measurements create a comprehensive picture of the tumor’s repair capabilities.[2][4]
The test results classify tumors as either HRD-positive or HRD-negative. A tumor is typically classified as HRD-positive if it has either a BRCA mutation detected or if it shows high levels of genomic scarring based on a composite score. Conversely, a tumor is classified as HRD-negative if no BRCA mutation is found and genomic scarring scores are low.[2]
Several diagnostic platforms are currently available for HRD testing, each using slightly different approaches but generally measuring similar characteristics. These FDA-approved companion diagnostic tests help determine eligibility for specific PARP inhibitor treatments. The testing methods employ advanced sequencing technologies that can detect both specific genetic mutations and broader patterns of genomic instability.[1][12]
It’s important to understand that HRD testing is different from genetic testing for inherited cancer risk. Germline genetic testing looks at genes inherited from parents and is performed on blood or saliva samples. It helps identify people at increased risk of developing cancer and can inform family members about potential inherited risks. In contrast, HRD testing examines the tumor itself and reveals characteristics that inform treatment decisions for the existing cancer.[3][13]
Treatment Implications
The discovery of HRD status has transformed treatment approaches for advanced ovarian cancer. Research has shown that HRD-positive tumors demonstrate increased sensitivity to certain therapies, particularly PARP inhibitors and platinum-based chemotherapy.[1][12]
Studies in Chinese patients with high-grade serous ovarian carcinoma showed that those with HRD-positive status had significantly improved progression-free survival compared to those with HRD-negative tumors. Patients with HRD-positive status showed a median progression-free survival of 30.5 months compared to 16.8 months for HRD-negative patients when treated with platinum-based chemotherapy. Even among patients without BRCA mutations, HRD-positive status was associated with better outcomes, with median progression-free survival of 27.5 months versus 16.8 months for HRD-negative patients.[8]
Platinum-based chemotherapy has long been a cornerstone of ovarian cancer treatment. The response to platinum-based treatment varies significantly based on HRD status. Research demonstrated that platinum-sensitive rates were higher in both BRCA-mutated HRD-positive tumors (97%) and non-BRCA HRD-positive tumors (90%) compared to 74% in HRD-negative tumors. Patients with BRCA mutations showed platinum sensitivity of 93.6% versus 75.4% in those without mutations.[8]
PARP inhibitors represent a newer class of targeted therapy that specifically exploits the vulnerabilities created by HRD. These drugs work by blocking PARP enzymes, which are involved in repairing single-strand DNA breaks. When PARP is inhibited in cells that already have deficient homologous recombination repair, the cells cannot repair DNA damage through either system, leading to cell death. Normal cells with intact repair systems can survive this treatment, making PARP inhibitors a form of targeted therapy.[1][12]
Clinical trials have demonstrated improved progression-free survival in HRD-positive patients treated with PARP inhibitors compared to those with homologous recombination proficiency. In China, regulatory approval was granted for PARP inhibitor treatment in combination with bevacizumab as first-line maintenance treatment for adult patients with advanced epithelial ovarian cancer who are HRD-positive.[11]
Treatment decisions for HRD-positive advanced ovarian cancer typically involve a combination approach. This may include surgery to remove as much tumor as possible, platinum-based chemotherapy, and maintenance therapy with PARP inhibitors for HRD-positive patients. The specific treatment plan depends on many factors including the extent of disease, overall health status, prior treatments, and HRD test results.[13][14]
Importantly, HRD testing helps identify not only patients most likely to benefit from PARP inhibitors but also helps avoid unnecessary treatment and side effects in patients whose tumors are unlikely to respond. This personalized medicine approach represents a significant advance in cancer care, allowing treatments to be tailored to the specific characteristics of each patient’s tumor.[1]
