Ovarian cancer arises when abnormal cells within the ovaries, fallopian tubes, or the lining of the abdomen begin to grow uncontrollably, forming a tumor. This disease can affect women, transgender men, and non-binary individuals assigned female at birth. While various factors contribute to the likelihood of developing ovarian cancer, age stands out as a significant element influencing risk.
The Common Age for Ovarian Cancer Diagnosis
Ovarian cancer is most frequently diagnosed in older women, particularly after menopause. The median age at diagnosis is 63 years, with about half of all cases occurring in women aged 63 or older. The risk generally increases with advancing age, showing a noticeable rise after age 50 or 55.
The most prevalent form, epithelial ovarian cancer, accounts for approximately 90% to 95% of all cases. The highest percentage of new diagnoses occurs in women between 55 and 64 years old.
Ovarian Cancer in Younger Women
While less common, ovarian cancer can also affect younger, pre-menopausal individuals. In these cases, the types of ovarian cancer diagnosed often differ from those typically seen in older women. Younger women are more likely to develop rarer forms, such as germ cell tumors or stromal tumors.
Germ cell tumors, originating from egg-producing cells, represent about 5% of all ovarian cancers. Approximately 80% of these tumors are identified in women under the age of 30.
Stromal tumors, arising from ovarian connective tissue, also account for about 5% of cases. While many stromal tumors are found in older women, some subtypes can occur in adolescents and young adults, with a median diagnosis age of around 50 years for malignant forms. Certain epithelial subtypes, such as low-grade serous carcinoma or clear cell carcinoma, may also be diagnosed in younger women.
Genetic Links to Early Onset
Inherited genetic factors play a role in early-onset ovarian cancer. Specific gene mutations can increase an individual’s susceptibility, leading to diagnosis at a younger age than the general population average. The BRCA1 and BRCA2 genes are well-known, with mutations raising the lifetime risk of ovarian cancer substantially. For example, BRCA1 mutations can lead to a lifetime risk of 35% to 70% by age 70, and BRCA2 mutations to 10% to 30%.
BRCA1 mutations are associated with an earlier age of ovarian cancer onset compared to BRCA2 mutations. Lynch syndrome, caused by mutations in mismatch repair genes, also increases ovarian cancer risk. Individuals with Lynch syndrome often develop ovarian cancer between 42 and 49 years, contrasting with the 60 to 65 years typical for sporadic cases. Other genetic conditions, such as Peutz-Jeghers syndrome, linked to STK11 gene mutations, can also elevate ovarian cancer risk.
Reproductive History and Other Risk Factors
Beyond genetics, reproductive history and other personal factors influence ovarian cancer risk. The number of ovulatory cycles experienced over a lifetime impacts risk. For example, having a first full-term pregnancy after age 35 or never having a full-term pregnancy can increase risk.
Conversely, multiple full-term pregnancies are associated with a decreased risk. The use of oral contraceptives is a protective factor, reducing ovarian cancer risk by 30% to 50%. This protective effect can persist for many years after discontinuing use, due to ovulation inhibition.
Certain medical conditions also contribute to risk.
Endometriosis
Endometriosis, where uterine-like tissue grows outside the uterus, is linked to an increased risk for specific ovarian cancer types, such as endometrioid and clear cell carcinomas. Studies suggest women with endometriosis have a risk four to ten times higher than those without the condition, depending on severity.
Other Medical Conditions
Obesity, defined as a body mass index (BMI) of 30 kg/m2 or higher, is associated with an increased ovarian cancer risk, particularly for certain less common subtypes. A personal history of breast, uterine, or colorectal cancer can also elevate ovarian cancer risk.