What Is Ovarian Cancer?

Ovarian cancer is the fifth leading cause of cancer-related death in Canadian women and is the deadliest cancer of the female reproductive system.

In 2013 there were 2,600 new cases diagnosed and 1,750 deaths from ovarian cancer in Canadian women. Of these, 1,150 new cases and 670 deaths occurred in Ontario alone. An estimated 17,000 women are living with ovarian cancer in Canada right now. 


The majority of ovarian cancers are diagnosed at an advanced stage, resulting in a poor overall survival rate.

An important reason why a large number of women die from ovarian cancer is because most women do not experience symptoms until the cancer has grown and spread to other organs. Women with ovarian cancer usually go to see a doctor with vague symptoms such as bloating, discomfort in the pelvic area, frequent urination and/or changes in bowel movements. At this advanced stage (stage III-IV described below) the mortality rate is high, with only 30% of patients surviving more than 5 years after diagnosis.  Advanced stage ovarian cancer is treated with a combination of surgery and chemotherapy. Although most tumours (especially high-grade serous carcinoma) respond very well at first, they usually come back within 2 years in a resistant form that can no longer be treated with standard anti-cancer drugs. In contrast, cancers diagnosed at an early stage (stage I below) can sometimes be treated by surgery alone and have a good prognosis, with up to 90% of patients surviving more than 5 years.


Ovarian cancer stages are based on how far the cancer has spread:

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Stage I – The cancer is in the ovaries only. It has not spread to other organs, tissues or lymph nodes in the pelvis area enclosed by your hip bones or to other areas of the body.

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Stage II – The cancer is in one or both of the ovaries and has spread to pelvic organs and tissues, such as the uterus, fallopian tubes, bladder, rectum or part of the large bowel called the sigmoid colon. The cancer has not spread outside the pelvis or to the lymph nodes.

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Stage III – The cancer is in one or both of the ovaries and has spread outside the pelvis to the membrane lining of the abdomen called the peritoneum and/or has spread to the lymph nodes at the back of the abdomen called the retroperitoneal lymph nodes.

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Stage IV – The cancer is in one or both of the ovaries and has spread to distant organs in the body, such as the lungs, liver, spleen or others outside the peritoneum, membrane lining the abdomen and part of pelvis and covering most of organs in these regions.

Ovarian cancer” is not one disease

There are 5 main types of (epithelial) ovarian cancer. Each type is associated with different clinical behaviours (stage at diagnosis, response to treatment, survival), genetic mutations and risk factors.


The 5 types of epithelial ovarian cancer are:

1. High-grade serous cancer

2. Low-grade serous cancer

3. Endometrioid cancer

4. Clear cell cancer

5. Mucinous cancer

HGSC is the most common and deadliest type of ovarian cancer. It is also the focus of our program.

Research findings over the past 10 years suggest that most cases of HGSC start developing in the fallopian tube rather than in the ovary. It is an aggressive cancer that spreads to the ovary and surrounding tissue very quickly. Because of this, 90% of women are diagnosed with HGSC at an advanced stage. As the most lethal type of ovarian cancer, 80-90% of women diagnosed with HGSC die of their disease. Unfortunately it is also the most common type of epithelial ovarian cancer, accounting for 70-80% of all cases.

Up to 1 in 5 women with HGSC have an inherited mutation in the BRCA1 or BRCA2 genes. If a woman with HGSC has a mutation in the BRCA1 or BRCA2 genes, her first-degree family members (for example her mother, sister or daughter) have a 50% chance of having the same mutation. Inheritance of the BRCA1 or BRCA2 gene mutation increases a woman’s lifetime risk of developing HGSC. For example, while the average woman in the general population has less than a 2% chance of developing HGSC, the risk is increased up to 40% for women who have a BRCA1 or BRCA2 gene mutation. The 4 other types of ovarian cancer mentioned above (low-grade serous cancer, endometriod cancer, clear cell cancer, or mucinous cancer) are not usually caused by a mutation to the BRCA1 or BRCA2 genes. Click to learn more about risks for ovarian cancer.

At this point in time, there is no good way for us to screen for ovarian cancer or to diagnose HGSC at an early stage. However, we can decrease the number of deaths from HGSC by identifying women at high risk and preventing the development of this deadly disease before it starts.