Ovarian Cancer Series 02: What Causes Ovarian Cancer? Understanding the Risk Factors
You may wonder whether it was related to lifestyle, family history, pregnancy, hormones, or something you could have done differently.
For most ovarian cancers, however, there is no single identifiable cause. Cancer develops through a complex combination of genetic, biological, reproductive, and other factors, and it is often impossible to determine exactly why ovarian cancer developed in one particular person.
This is why it is important to distinguish between a cause and a risk factor.
It is also important to recognize that much of what we know about ovarian cancer risk factors comes from research on epithelial ovarian cancer, the most common type of ovarian cancer. Ovarian cancer includes several different tumor types, and not every risk factor applies equally to all of them.
A Risk Factor Is Not the Same as a Cause
A risk factor is something associated with a greater or lower likelihood of developing a disease.
Having a risk factor does not mean that you will develop ovarian cancer. At the same time, ovarian cancer can occur in people who have few or no recognized risk factors.
For example, older age or a family history of ovarian cancer may increase risk, but neither can predict whether an individual will actually develop the disease.
The purpose of understanding risk factors is not to identify something a person did “wrong.” Instead, risk factors can help put individual risk into context and identify situations in which additional medical or genetic evaluation may be appropriate.
Does Ovarian Cancer Risk Increase With Age?
Age is one of the important risk factors for ovarian cancer.
Ovarian cancer can occur in younger women, but overall risk increases with age, and the disease is more common after menopause. According to the American Cancer Society, about half of women diagnosed with ovarian cancer are 63 or older.
This does not mean that menopause itself causes ovarian cancer.
As we age, genetic changes can accumulate in cells, while other age-related biological changes may also influence cancer development.
A more accurate way to understand the relationship is therefore not “menopause causes ovarian cancer,” but rather “ovarian cancer risk generally increases with age.”
Does a Family History of Ovarian Cancer Increase Risk?
Family history is another important part of ovarian cancer risk assessment.
Having a close relative such as a mother, sister, or daughter who has had ovarian cancer can be associated with a higher risk.
Some of this familial risk can be related to inherited genetic variants. The best-known examples involve the BRCA1 and BRCA2 genes, while genetic changes associated with Lynch syndrome can also increase ovarian cancer risk.
However, having a family history of ovarian cancer does not automatically mean that the cancer is hereditary.
Doctors may consider which relatives developed cancer, what types of cancer occurred, the ages at diagnosis, and whether cancers such as ovarian, breast, or colorectal cancer appear repeatedly within the family.
The opposite is also important: having no obvious family history does not completely rule out inherited genetic risk.
We will look more closely at BRCA1, BRCA2, hereditary ovarian cancer risk, genetic counseling, and genetic testing in the next article.
Are Reproductive Factors Related to Ovarian Cancer Risk?
Several reproductive factors have been associated with ovarian cancer risk.
Research has found associations between ovarian cancer risk and factors such as pregnancy and childbirth history. Breastfeeding and oral contraceptive use have also been associated with a lower risk, while never having given birth has been associated with a higher risk.
One hypothesis proposed to explain some of these patterns involves the number of ovulations a person experiences over a lifetime. However, this should not be simplified into the idea that “more ovulation causes ovarian cancer.”
Ovarian cancer develops through multiple interacting factors. Pregnancy, childbirth, breastfeeding, or contraceptive use alone cannot determine whether someone will develop the disease.
These associations are useful for understanding ovarian cancer risk, but they should not be used to calculate personal risk in isolation.
We will discuss factors associated with lowering ovarian cancer risk—and what prevention can and cannot accomplish—in a later article in this series.
Does Endometriosis Cause Ovarian Cancer?
People with endometriosis may be particularly concerned when they hear that the condition has been associated with ovarian cancer.
Research has found an association between endometriosis and an increased risk of ovarian cancer. However, this relationship requires careful interpretation.
Ovarian cancer is not a single disease. It includes several histologic subtypes, and the association with endometriosis appears to be stronger for certain types, particularly clear cell carcinoma and endometrioid carcinoma.
This does not mean that having endometriosis is a sign that ovarian cancer is developing.
It is also inaccurate to assume that “endometriosis will eventually turn into ovarian cancer.” Most people with endometriosis do not develop ovarian cancer.
An increased risk seen in studies does not mean that most people with endometriosis will develop the disease. Endometriosis should therefore be considered alongside other information such as age, family history, symptoms, and, when appropriate, imaging findings.
Is Menopausal Hormone Therapy Related to Ovarian Cancer Risk?
Some women use hormone therapy to manage symptoms associated with menopause.
Research has found an association between some forms of menopausal hormone therapy and an increased risk of ovarian cancer. The increase in risk reported in studies is relatively small.
This does not mean that hormone therapy will cause ovarian cancer in an individual.
Hormone therapy can also provide meaningful benefits by relieving menopausal symptoms and improving quality of life. Whether it is appropriate depends on the individual's medical history, symptoms, treatment goals, and overall balance of benefits and risks.
For this reason, someone who is concerned about ovarian cancer should not stop prescribed hormone therapy on their own. The decision should be discussed with a healthcare professional who can consider the individual's circumstances.
Are Overweight and Obesity Related to Ovarian Cancer Risk?
Higher body weight and obesity have been associated with a modest increase in ovarian cancer risk in research.
However, body weight alone does not determine whether ovarian cancer will develop.
Ovarian cancer is influenced by multiple factors, including genetics, age, reproductive history, and other biological factors.
Many other possible influences—including diet, specific foods, alcohol use, and fertility treatment—have also been investigated, but the evidence is not equally strong or consistent for all of them.
For that reason, it is important not to treat every reported association as a proven cause or to blame a single lifestyle factor for why ovarian cancer developed.
What If I Have Several Risk Factors?
Reading a list of risk factors can make it tempting to compare each one with your own history.
But individual ovarian cancer risk cannot be calculated simply by adding risk factors together.
Different factors have different levels of influence, and their importance may also vary among ovarian cancer subtypes. A strong inherited genetic risk, such as certain BRCA1 or BRCA2 variants, should not be interpreted in the same way as more common risk factors.
Most importantly, having risk factors is not the same as having ovarian cancer.
Risk factors help us understand the likelihood of developing a disease; they are not diagnostic criteria.
Personal risk assessment may take into account age, medical history, family history, and, when appropriate, genetic information.
Family history deserves particular attention. If ovarian, breast, colorectal, or certain other cancers have occurred repeatedly within a family—or if a close relative has had ovarian cancer—it may be appropriate to discuss whether hereditary cancer risk assessment or genetic counseling is needed.
Final Takeaway
For most people, ovarian cancer cannot be traced to a single cause.
Factors associated with ovarian cancer risk include older age, family history and inherited genetic factors, certain reproductive factors, endometriosis, some forms of menopausal hormone therapy, and overweight or obesity.
But having one or more risk factors does not mean that ovarian cancer will develop. Likewise, ovarian cancer can occur even when no obvious risk factor is present.
The purpose of understanding risk factors is not to find something to blame for why cancer developed, but to understand risk more accurately.
Among these factors, family history can provide an important clue to hereditary ovarian cancer risk.
So how much does ovarian cancer risk change when a BRCA1 or BRCA2 variant is present, and who should consider genetic counseling or testing?
In the next article, we will look more closely at BRCA1 and BRCA2 variants, hereditary ovarian cancer risk, and when genetic counseling and genetic testing may be considered.
References
American Cancer Society. Ovarian Cancer Risk Factors.
American Cancer Society – Ovarian Cancer Risk Factors
National Cancer Institute. Ovarian, Fallopian Tube, and Primary Peritoneal Cancer Prevention (PDQ®) – Patient Version.
National Cancer Institute – Ovarian Cancer Prevention
National Cancer Institute. Ovarian, Fallopian Tube, and Primary Peritoneal Cancer Prevention (PDQ®) – Health Professional Version.
National Cancer Institute – Ovarian Cancer Prevention, Health Professional Version
American College of Obstetricians and Gynecologists. Ovarian Cancer.
ACOG – Ovarian Cancer
American College of Obstetricians and Gynecologists. Hereditary Cancer Syndromes and Risk Assessment.
ACOG – Hereditary Cancer Syndromes and Risk Assessment
Comments
Post a Comment