Cancer occurs when cells undergo a transformation and begin to grow and multiply without normal controls. As the cells grow and multiply, they form masses called tumors. Cancer is dangerous because it overwhelms healthy cells by taking their space and the oxygen and nutrients they need to survive and function.
Ovarian cancer occurs when a tumor forms in one or both of a woman's ovaries. The ovaries are a pair of small organs that produce and release ova, or human eggs. The ovaries also produce important hormones such as estrogen andprogesterone. They are located in the lower abdomen (pelvis), on either side of thewomb (uterus). Ova released by the ovaries travel through the fallopian tubes to the uterus, where they may or may not be fertilized by the male sperm.
Cancerous tumors are malignant. This means they spread to other tissues and organs. Not all tumors, however, are malignant.
In a process called metastasis, malignant tumors may encroach on and invade neighboring organs or lymph nodes, or they may enter the bloodstream and spread to remote organs such as the liver or lungs. Metastatic tumors are the most aggressive and serious of all tumors.
The type of cell that originated the abnormal growth determines the class of the ovarian tumors.
- Epithelial tumors: These tumors arise from a layer of cells that surrounds the outside of the ovary called the germinal epithelium. About 70-80% of all ovarian cancers are epithelial. These are most common in women who have been through menopause (aged 45-70 years).
- Stromal tumors: Stromal tumors develop from connective-tissue cells that help form the structure of the ovary and produce hormones. Usually, only one ovary is involved. These account for 5-10% of ovarian cancers. These tumors typically occur in women aged 40-60 years. Often, surgical removal of the tumor is the only treatment needed. If the tumor has spread, though, the woman needs chemotherapy.
- Germ cell tumors: Tumors that arise from germ cells (cells that produce the egg) account for about 15% of all ovarian cancers. These tumors develop most often in young women (including teenaged girls). Although 90% of women with this type of cancer are successfully treated, many become permanentlyinfertile.
- Metastatic tumors: Only 5% of ovarian cancers have spread from other sites. The most common sites from which they spread are the colon (52%), breast (17%), stomach (10%), and pancreas (5%).
- Within these main classes are many different subtypes of tumors.
Noncancerous (benign) ovarian masses include abscesses or infections, fibroids, cysts, polycystic ovaries, endometriosis-related masses, ectopic pregnancies, and others.
- Of markedly enlarged ovarian masses (>4 cm) found in women who are still menstruating (have not been through menopause), about 20% are cancerous.
- Of markedly enlarged masses found in women who have been through menopause, about 45-50% are cancerous.
The incidence of ovarian cancer varies greatly. Globally, Scandinavia, Israel, and North America have the highest rates. Developing countries and Japan have the lowest rates.
- At least 15,000 women die each year from ovarian cancer.
- The 5-year survival rate is greater than 75% if diagnosis of the cancer occurs before it has spread to other organs. However, the 5-year survival rate drops to 20% when the tumor has spread to the upper abdomen.
- In the United States, about 1 in 56 women develops cancer of the ovary. More than 26,000 new cases are diagnosed each year.
Ovarian cancer is difficult to diagnose because symptoms often do not occur until late in the disease. Symptoms do not occur until the tumor has grown large enough to apply pressure to other organs in the abdomen, or until the cancer has spread to remote organs.
The symptoms are nonspecific, meaning they could be due to many different conditions. Cancer is not usually the first thing considered in a woman having symptoms.
The only early symptom of the disease ismenstrual irregularity.
Symptoms that come later include the following:
- Pelvic pain or pressure.
- Pain with intercourse.
- Abdominal swelling and bloating.
- Urinary frequency.
- Ascites - Collection of fluid in the abdomen, contributing to abdominal distension and shortness of breath.
- Loss of appetite.
- Feeling full after eating little.
- Gas and/or diarrhea.
- Nausea and vomiting.
- Abnormalities in menstruation, pubertal development, and abnormal hair growth (with tumors that secrete hormones).
In 95% of ovarian cancer cases, no identifiable cause is present; however, family history does play a role.
- The lifetime risk for US women of developing ovarian cancer is 1.4%.
- If one first-degree relative -a mother, sister, or daughter -has the disease, the risk increases to 3-5%.
- The risk can climb to 50% if 2 first-degree relatives have the disease.
- If a woman has ovarian cancer and her daughter develops ovarian cancer, the daughter will probably develop the cancer at a relatively young age (younger than 60 years).
Ovarian cancer has been linked with 3 hereditary syndromes.
- Breast-ovarian cancer syndrome.
- Hereditary nonpolyposis colorectal cancersyndrome.
- Site-specific ovarian cancer syndrome.
Breast-ovarian cancer syndrome: A mutation in a gene called BRCA1 has been linked to increased risk of both breast and ovarian cancer.
- About 30-40% of women who have this mutation develop ovarian cancer.
- Another mutation, involving the BRCA2 gene, also increases the risk of ovarian cancer but to a lesser degree.
- These mutations are hereditary.
- Clues that may indicate the presence of these mutationsinclude family members who have ovarian cancer or breast cancer (especially those whoare diagnosed with these cancers whenyounger than 50 years), a relative with both breast and ovarian cancer, or a male relative with breast cancer.
- Development of more precise estimates of cancer risk and better genetic testing for carriers of these genes is taking place.
Hereditary nonpolyposis colorectal cancer (HNPCC) syndrome (Lynch syndromeII): this genetic syndrome has been dubbed "family cancer syndrome" and is associated with colon cancer developing in people younger than 50 years.
- Other organs that can be involved include the uterus, ovary, breast, stomach, and pancreas.
- A mutated gene causes this syndrome.
- Women with this syndrome have a 10% chance of developing ovarian cancer.
Site-specific ovarian cancer syndrome: This is the least common of the 3 syndromes and experts don't know much about it, yet. This syndrome may be due to mutations of the BRCA1 gene.
Other factors that increase ovarian cancer risk include the following:
- Age greater than 50 years.
- No pregnancies.
- Use of fertility drugs: Some studies have shown that the use of fertility drugs increases the risk of ovarian cancer, but study results have not been consistent.
- Ashkenazi Jewish heritage.
- European (white) heritage: White women are much more likely to have ovarian cancer than African American women.
- Asbestos exposure.
- Repeated exposure of the genitals to talc.
- Irradiation of the pelvic area.
- Some viruses, especially the virus that causes mumps.
Some findings suggest that estrogen may promote ovarian cancer in women who have been through menopause. For years,the cancer risks involved with usinghormone replacement therapy divided the medical community. Research findings in 2002 and early 2003 showed that hormone replacement therapy does not provide many of the benefits it was believed to have, and it increases the risk of heart disease. Experts no longer recommend long-term hormone replacement therapy for most women.
Some factors decrease ovarian cancer risk.
- Any factor that inhibits ovulation (release of an egg from the ovary) seems to protect against development of ovarian cancer. This may be because ovulation disrupts the epithelial layer of the ovary. As cells divide to repair the damage, uncontrolled division and malignant changes may occur.
- Term pregnancy (lasting the full 9 months) significantly reduces the risk of ovarian cancer. As the number of pregnancies increases, the risk of ovarian cancer decreases.
- Use of oral contraceptives (birth control pills) reduces the risk of ovarian cancer.
- Breastfeeding lowers risk of ovarian cancer, and the risk decreases with increasing duration of breastfeeding.
- Removal of the ovaries before cancer appears reduces the risk to zero. This may be a consideration in women with inherited cancer risks. Experts should base this decisionon genetic testing and counseling.
- Having the woman's "tubes tied" (tubal ligation) to prevent pregnancy.
- Havinga hysterectomy lowers the risk of ovarian cancer.
Treatment of ovarian cancer should be under the direction of an experienced gynecologic oncologist (a specialist in women's cancers).
Surgery is the usual first treatment for ovarian cancer. Whenever possible, the surgery takes placeat the time of exploratory laparotomy. The operation is paused while the pathologist rapidly reviews the biopsy tissues. The pathologist's report determines the structures affected by cancer and if they should be removed. This spares the woman from undergoing another surgery.
- For stage I tumors, only the involved ovary and fallopian tube may be removed for women who wish to become pregnant in the future. For women who do not wish to become pregnant, both ovaries, both fallopian tubes, and the uterus are removed. This is a hysterectomy with bilateral (2-sided) salpingo-oophorectomy. Usually this procedure removes the lymph nodes surrounding these organs and the omentum. If the tumor cell type is especially worrisome (grade 3 tumors and all stage IC tumors), chemotherapy is usually given as well.
- Stage II cancer treatment involves removal of the uterus, ovaries, and fallopian tubes, resection (partial removal)of any tumor in the pelvic area, and resection of any other structures affected with cancer. Chemotherapy is strongly recommended. The best treatment at this time involves a platinum-based agent (carboplatin) and paclitaxel (Taxol). These agents are administered in 6 cycles of 3 weeks each.
- Stage III treatment is identical to stage II treatment, except more aggressive chemotherapy and possibly experimental treatments are given. Some women may be candidates for direct abdominal treatment.This type of treatment is referred to as peritoneal therapy. This type of therapy is more difficult to take but may improve survival.
- Stage IV treatment involves extensive debulking and multi-agent chemotherapy.
After chemotherapy is completed, the woman may undergo "second-look surgery". Her surgeon will examine her remaining pelvic and abdominal structures for evidence of residual cancer. Samples of fluid and tissues may be taken to check for residual cancer cells.