Endometriosis and Ovarian Cancer: Understanding the Connection

June 6, 2024

Endometriosis and Ovarian Cancer: Understanding the Connection

Endometriosis and ovarian cancer are two distinct gynecological conditions that can cause significant concerns for women’s health. While endometriosis is a benign disorder, it shares some similarities with ovarian cancer, leading many women to question the potential link between the two. 

In this article, we’ll explore the connection between endometriosis and ovarian cancer, examining the latest research, similarities and differences, as well as what you can do to stay informed and proactive about your health.

What is Endometriosis?

Endometriosis is a chronic condition in which tissue similar to the lining of the uterus (endometrium) grows outside the uterus, often on the ovaries, fallopian tubes, and other pelvic structures. This misplaced tissue responds to hormonal changes throughout the menstrual cycle, causing inflammation, scarring, and pain.

According to WHO, endometriosis affects an estimated 10% of women of reproductive age worldwide, or approximately 176 million women. Despite its prevalence, endometriosis remains an often misunderstood and underdiagnosed condition.

Endometriosis Causes and Risk Factors

While the exact cause of endometriosis remains unknown, several theories attempt to explain its development:

  • Retrograde menstruation: Menstrual blood containing endometrial cells flows back through the fallopian tubes and into the pelvic cavity, where the cells implant and grow.
  • Immune system dysfunction: Alterations in the immune response may allow endometrial tissue to grow outside the uterus.
  • Genetic factors: Endometriosis tends to run in families, suggesting a potential genetic predisposition.

Risk factors for endometriosis include:

  • Never giving birth
  • Starting menstruation at an early age
  • Going through menopause at an older age
  • Short menstrual cycles (less than 27 days)
  • Heavy menstrual periods lasting more than 7 days
  • Higher levels of estrogen in the body
  • Low body mass index
  • Alcohol consumption
  • Family history of endometriosis

Common Endometriosis Symptoms

The most common symptoms of endometriosis include:

  • Painful periods (dysmenorrhea)
  • Pelvic pain and cramping, which may be chronic
  • Pain during or after sexual intercourse
  • Pain with bowel movements or urination
  • Excessive bleeding during or between periods
  • Infertility

It’s important to note that the severity of symptoms does not necessarily correlate with the extent of endometriosis. Some women with mild endometriosis may experience severe pain, while others with advanced endometriosis may have minimal symptoms.

Overview of Ovarian Cancer

Ovarian cancer is a malignant growth that starts in the ovaries, the reproductive glands that produce eggs and female hormones. It is the fifth leading cause of cancer-related deaths among women in the United States; projections indicate nearly 12 million women will be diagnosed and 8 million will die from ovarian cancer by 2050.

Several factors can increase a woman’s risk of developing ovarian cancer: 

  • Older age (majority of cases occur after menopause)
  • Family history of ovarian, breast, or colorectal cancer
  • Inherited genetic ovarian cancer mutations (e.g., BRCA1 and BRCA2)
  • Never having been pregnant
  • Fertility treatment
  • Hormone therapy after menopause
  • Obesity
  • Endometriosis (which we will discuss in more detail)

Symptoms of Ovarian Cancer

Early-stage ovarian cancer rarely causes noticeable symptoms, making it challenging to detect. As the disease progresses, women may experience: 

  • Bloating or swelling of the abdomen
  • Pelvic pressure or abdominal pain
  • Difficulty eating or feeling full quickly
  • Urinary urgency or frequency
  • Change in bowel habits, such as constipation
  • Unintentional weight loss

Is There a Link Between Endometriosis and Ovarian Cancer? 

The potential link between endometriosis and ovarian cancer has been a topic of interest for researchers and a concern for many women living with endometriosis. While the two conditions are distinct, there are some compelling reasons to investigate their relationship further. In the following sections, we’ll take a closer look at the current research on the connection between endometriosis and ovarian cancer, exploring the evidence, proposed mechanisms, and implications for women’s health.

Examining the Connection: What the Research Shows

While endometriosis is a benign condition, research has shown that women with endometriosis have a slightly increased risk of developing certain types of ovarian cancer, particularly endometrioid and clear cell carcinomas. 

A meta-analysis of 20 case-control studies and 15 cohort studies found that women with endometriosis had a 1.42 times higher risk of ovarian cancer compared to women without endometriosis. This translates to a lifetime risk of ovarian cancer of 1.8% for women with endometriosis, compared to 1.3% for the general female population. 

Proposed Mechanisms Linking the Two Conditions

Several theories attempt to explain the potential link between endometriosis and ovarian cancer:

  • Genetic mutations: Studies have identified common genetic alterations in both endometriosis and endometriosis-associated ovarian cancers, such as mutations in the ARID1A, PIK3CA, and PTEN genes.
  • Hormonal factors: The estrogen-dependent nature of endometriosis may create an environment that promotes the growth of certain types of ovarian cancer.
  • Inflammation: Chronic inflammation associated with endometriosis may contribute to the development of ovarian cancer by causing DNA damage and promoting cell proliferation. 

Endometriosis vs. Ovarian Cancer

While endometriosis and ovarian cancer share some similarities, such as the potential for causing pelvic pain and the presence of tissue growths, they are ultimately distinct conditions with important differences. 

Understanding these differences is crucial for accurate diagnosis, appropriate treatment, and patient education. In the following section, we’ll explore the key distinctions between endometriosis and ovarian cancer, focusing on their unique symptoms, disease characteristics, and diagnostic challenges.

Key Differences in Symptoms and Disease Characteristics

While endometriosis and ovarian cancer share some symptoms, there are notable differences between the two conditions:

  • Endometriosis symptoms are typically cyclical and related to menstrual periods, while ovarian cancer symptoms are generally persistent and unrelated to the menstrual cycle.
  • Endometriosis is a benign condition, while ovarian cancer is a malignant growth that can metastasize (spread) to other parts of the body.
  • Endometriosis is more common in women of reproductive age, while ovarian cancer is more frequently diagnosed in postmenopausal women.

Diagnostic Challenges: Is it Endometriosis or Ovarian cancer?

Distinguishing between endometriosis and ovarian cancer can be challenging, as both conditions can cause similar symptoms and appear as cysts or masses on imaging tests. Definitive diagnosis often requires surgical biopsy and histopathological examination.

Can Endometriosis Cause Ovarian Cancer?

While studies have shown an increased risk of ovarian cancer in women with endometriosis, the overall lifetime risk remains low, with an estimated 1.8% lifetime risk for women with endometriosis compared to 1.3% for the general female population. 

Endometriosis as a Risk Factor vs. Cause

Current evidence suggests that endometriosis is a risk factor for ovarian cancer rather than a direct cause. Other ovarian cancer risk factors, such as genetic predisposition and environmental influences, likely play a role in the development of ovarian cancer in women with endometriosis.

The Role of Genetics, Inflammation, and Hormones

As mentioned earlier, genetic mutations, chronic inflammation, and hormonal factors may contribute to the link between endometriosis and ovarian cancer. However, more research is needed to fully understand the complex interplay of these factors and their role in the development of ovarian cancer in women with endometriosis.

Comparing the Epidemiology and Risk Factors

Endometriosis and ovarian cancer share some risk factors, such as nulliparity (having never given birth to a child) and early menarche (the onset of menstrual periods at a young age, typically before the age of 12). However, there are also notable differences in their epidemiology:

  • Endometriosis affects approximately 10% of women of reproductive age, while ovarian cancer is relatively rare, with a lifetime risk of about 1.3%.
  • Endometriosis is typically diagnosed in women aged 25-35 years, while ovarian cancer is more commonly detected in postmenopausal women, with a median age at diagnosis of 63. 

However, it is important to note that ovarian cancer can be challenging to detect, particularly in its early stages, due to the lack of specific symptoms and effective screening methods. While ovarian cancer is more prevalent in older women, it can also affect younger women, underscoring the importance of awareness and prompt evaluation of persistent symptoms, regardless of age.

Histological Subtypes of Ovarian Cancer Linked to Endometriosis

Endometriosis is most strongly associated with two subtypes of epithelial ovarian cancer: endometrioid and clear cell carcinomas. These subtypes are less common than high-grade serous ovarian cancer but tend to be diagnosed at an earlier stage.

Studies have shown that endometriosis-associated ovarian cancers may have a better prognosis than non-endometriosis-associated ovarian cancers. This may be due to the earlier stage at diagnosis and the favorable histological subtypes associated with endometriosis.

Latest Research on the Endometriosis and Ovarian Cancer Link

As researchers continue to unravel the complex relationship between endometriosis and ovarian cancer, there is hope for new breakthroughs in prevention, early detection, and targeted therapies. Ongoing studies aim to identify biomarkers and genetic factors that can help predict and manage the risk of ovarian cancer in women with endometriosis.

Recent studies have provided further insights into the relationship between endometriosis and ovarian cancer:

  • A 2020 study found that endometriosis was associated with a 2.5-fold increased risk of clear cell ovarian cancer and a 1.5-fold increased risk of endometrioid ovarian cancer.
  • Another study discussed the genetic epidemiology of endometriosis and endometriosis-associated cancers, including shared genetic risk factors and potential causal relationships.  
  • In 2024, Dr. Holly Harris, an epidemiologist from the Fred Hutchinson Cancer Research Center, received a grant to investigate whether endometriosis is a risk factor for clear cell ovarian cancer. The study aims to compare risk factors between people with and without endometriosis and explore the potential role of inflammation in the development of ovarian cancer.

Ongoing Efforts to Unravel the Relationship

Researchers continue to investigate the complex relationship between endometriosis and ovarian cancer, focusing on:

  • Identifying biomarkers that can help distinguish between benign endometriosis and endometriosis-associated ovarian cancer.
  • Exploring targeted therapies for endometriosis-associated ovarian cancers based on their unique molecular profiles. 

The Importance of Early Detection and Prevention

Given the potential link between endometriosis and ovarian cancer, early detection and prevention strategies are crucial. Regular gynecologic exams and awareness of ovarian cancer symptoms can help detect the disease at an earlier, more treatable stage.

Currently, there is no recommended screening test for ovarian cancer in women with endometriosis. However, women with endometriosis should discuss their individual risk factors with their healthcare provider and develop a personalized monitoring plan.

Meanwhile, women with endometriosis who experience persistent or worsening symptoms should consult their healthcare provider promptly. Warning signs that may indicate ovarian cancer include: 

  • Persistent bloating or abdominal distension
  • Pelvic or abdominal pain
  • Feeling full quickly or difficulty eating
  • Urinary changes, such as urgency or frequency

The Bottom Line on Endometriosis and Ovarian Cancer

While research has shown an association between endometriosis and ovarian cancer, it is essential to understand that the overall risk remains low. The majority of women with endometriosis will not develop ovarian cancer, and having endometriosis does not necessarily mean that a woman will develop ovarian cancer. 

Increased awareness and early intervention are crucial for both endometriosis and ovarian cancer. Women should be proactive about their gynecologic health, reporting any unusual symptoms to their healthcare provider and undergoing regular check-ups.

Non-profit organizations like Not These Ovaries are working tirelessly to fund research and clinical trials to support ovarian cancer patients and improve outcomes. By raising awareness and supporting ongoing research efforts, we can work towards better prevention, early detection, and treatment strategies for both endometriosis and ovarian cancer.

In conclusion, while the link between endometriosis and ovarian cancer is a cause for concern, it is essential to approach the topic with a balanced perspective. By staying informed, engaging in open communication with healthcare providers, and supporting research efforts, women with endometriosis can take proactive steps to manage their health and well-being.