In Canada, an estimated 3,000 women are diagnosed with ovarian cancer each year. More Canadian women die from ovarian cancer than all other gynecologic cancers combined, including cervical and endometrial (uterine) cancers.
Ovarian cancer remains difficult to detect. Although the 5-year survival rate is approximately 90% when ovarian cancer is detected in its earliest stages, 80% of cases are diagnosed at an advanced stage where 5-year survival is only about 30%.
Currently, no reliable screening test exists for ovarian cancer.
The causes of ovarian cancer are not known. Some factors that may increase the risk of ovarian cancer include the following:
- aged 50 years and above
- family history of ovarian cancer or breast cancer (higher risk in women with BRCA1 or BRCA2 gene mutation)
- having had cancer before (e.g., breast, uterine, colon)
- having never been pregnant
Some people with ovarian cancer do not have these risk factors, and other people who have these risk factors do not go on to have ovarian cancer.
Other risk factors such as early onset of menstruation or late menopause are not well proven.
Fertility treatments that include stimulation of ovulation may also increase the risk of ovarian cancer, but this is also not well proven and is difficult to confirm.
Symptoms and Complications
Ovarian cancer often goes undiagnosed until it reaches an advanced stage, primarily because symptoms are not common in the early stages and when they do occur, the symptoms may be general and non-specific.
Symptoms of ovarian cancer can include:
- abdominal discomfort
- abnormal vaginal bleeding
- bloating or increase in abdominal size
- changes in bowel movements (e.g., constipation)
- feeling full earlier than normal after eating
- increased urinary urgency or frequency
- loss of appetite
- pain during sexual intercourse
- pelvic pain
- upset stomach
- weight loss or gain
These symptoms appear commonly and may be normal or can be associated with a variety of other conditions, but if they persist, talk to your doctor.
Making the Diagnosis
Unfortunately, no reliable screening test exists for ovarian cancer, and approximately 80% of ovarian cancers are diagnosed in advanced stages.
If ovarian cancer is suspected, the following tests may be performed:
- physical examination, including a pelvic and abdomen exam
- ultrasound – transvaginal/pelvic and abdominal – a test used to create a "picture" of the pelvic and abdominal contents
- CT scans (computed tomography), or MRI (magnetic resonance imaging), or bone scans to see if the cancer has spread
- blood tests to check your blood cells and organ function (e.g., kidney, liver) and to test for a tumour marker called cancer antigen 125 (CA-125)
A CA-125 test uses an antibody to detect a chemical produced at higher levels by ovarian cancer cells. However, it is elevated in only about 50% of cases of early-stage ovarian cancer and can also be elevated in noncancerous conditions, especially in premenopausal women. In instances where ovarian cancer is suspected, the CA-125 may assist in the diagnosis in combination with other tests. The OVA-1 test, which includes a measure of CA-125, has been recently developed to aid in early diagnosis.
If the results of these tests suggest ovarian cancer, additional tests will be required to confirm the diagnosis. But, it is important to keep in mind that not all ovarian tumours are cancerous - many turn out to be benign (noncancerous).
To confirm a diagnosis of ovarian cancer, cancer tissue or cancer cells must be obtained by one of the following procedures:
- taking a sample of abdominal fluid if it is present: This is usually a simple procedure done with local anaesthetic. Pathologists then examine the fluid for cancer cells.
- obtaining a biopsy of the tumour: This is a fairly simple procedure and is done under local anaesthetic, usually with CT or ultrasound guidance.
- undergoing a laparotomy: This is a surgical exploration of the abdomen to help confirm a diagnosis and, if need be, to also remove all evidence of the cancer as the first step in treatment.
If ovarian cancer is confirmed, the above tests also help determine the stage of ovarian cancer. Ovarian cancer has the following stages:
- stage IA-C: confined to one or both ovaries
- stage IIA-B: spread to other areas in the pelvis (e.g., fallopian tubes, uterus)
- stage IIIA-C: spread to the organs or lymph nodes within the abdomen
- stage IVA-B: spread to organs beyond the abdomen
From a biopsy, the grade of the tumour can be determined. The grade describes how abnormal the tumour cells appear under a microscope. Ovarian cancer can be grade 1, 2, or 3. Higher-grade tumors appear more abnormal under a microscope.
Treatment and Prevention
It may not be possible to prevent ovarian cancer. Ovarian cancer may be related to ovulation and the menstrual cycle. Using the birth control pill, which suppresses ovulation, has been shown to decrease the risk of ovarian cancer, but the reason for this is unclear.
Women who have an inherited risk of ovarian cancer may choose to have their ovaries and fallopian tubes surgically removed (prophylactic surgery). Tubal ligation has also been shown to decrease the risk of ovarian cancer for women with this genetic profile. While prophylactic surgery offers what is thought to be the greatest reduction in risk, it may not completely eliminate the risk. Moreover, the lining of the abdominal cavity (peritoneum) may develop cancer similar to ovarian cancer even if the ovaries are removed.
Treatment of ovarian cancer usually involves a combination of surgery and chemotherapy. During a laparotomy (open incision of the abdomen), the surgeon may remove the ovaries, fallopian tubes, uterus, cervix, some of the fatty tissue covering the abdomen (omentum), and lymph nodes. If the cancer has spread outside of the ovaries, the surgeon may remove these tumours with goal of removing all or most of the tumour that they can see.
With early-stage ovarian cancer, women who still want to have children may choose to have only one fallopian tube and ovary removed. But, there may still be a chance that cancer could appear in the other ovary, the fallopian tube, or the uterus.
Chemotherapy with anticancer medications usually involves taking a combination of medications. Chemotherapy may be given intravenously (injected into the vein) or directly into the abdominal cavity (intraperitoneal chemotherapy). Intraperitoneal chemotherapy is currently given only to women who have advanced-stage disease and have had most of their tumor removed during surgery.
Certain individuals may also be candidates for radiation therapy. Biotherapy and immunotherapy treatments are currently under study. Women with ovarian cancer should also talk to their doctor about available clinical trials.
A complete response to the treatment (remission) occurs when no detectable cancer is found either through examination by an oncologist or through tests such as an ultrasound or CT.
Despite achieving remission with treatment, ovarian cancer can recur months to years later in as many as 70% of women. The risk of recurrence is highest in women with advanced-stage disease at diagnosis. To monitor for recurrent disease, doctors may use a combination of physical examinations, CT scans, or blood tests (e.g., CA-125).