OVARIAN CANCER DEFINITION
Ovarian cancer is a type of cancer that begins in the ovaries. Women have two ovaries, one on each side of the uterus. The ovaries — each about the size of an almond — produce eggs (ova) as well as the hormones estrogen and progesterone.
Ovarian cancer often goes undetected until it has spread within the pelvis and abdomen. At this late stage, ovarian cancer is more difficult to treat and is frequently fatal. Early-stage ovarian cancer, in which the disease is confined to the ovary, is more likely to be treated successfully.
Surgery and chemotherapy are generally used to treat ovarian cancer.
OVARIAN CANCER CAUSES
Although we know that ovarian cancer, like many other cancers, is caused by cells dividing and multiplying in an unordered way, nobody completely understands why cancer of the ovary occurs. We know that the following risk factors are linked to a higher chance of developing the disease:
Most women who develop ovarian cancer do not have an inherited gene mutation. Women with close relatives who have/had ovarian cancer, as well as breast cancer, have a higher risk of developing ovarian cancer compared to other women. There are two genes – BRCA1 and BRCA2 – which significantly raise the risk. The BRCA1 and BRCA2 genes also raise the risk of breast cancer. Those genes are inherited. The BRCA1 gene is estimated to increase ovarian cancer risk by 35% to 70%, and the BRCA2 by 10% to 30%. People of Ashkenazi Jewish descent are at particularly high risk of carrying these types of gene mutations.
Women with close relatives who have/had colon cancer, prostate cancer or uterine cancer are also at higher risk of ovarian cancer.
Genetic screening can determine whether somebody carries the BRCA1 and/or BRCA2 genes. Although a test for gene mutations known to significantly increase the risk of hereditary breast or ovarian cancer has been available for more than a decade, a study by researchers from Massachusetts General Hospital found that few women with family histories of these cancers are even discussing genetic testing with their physicians or other health care providers.
After eight years of searching, an international team of scientists found that a single nucleotide polymorphisms (SNP) on chromosome 9 that is uniquely linked to ovarian cancer. The scientists estimated that women carrying that particular version of the SNP on both copies of chromosome 9 have a 40 per cent higher lifetime risk of developing ovarian cancer than women who do not carry it on either copy of chromosome 9, while women with only one copy of the variant have a 20 per cent higher lifetime risk of developing ovarian cancer than women who have none.
OVARIAN CANCER PATHOPHYSIOLOGY
Most theories of the pathophysiology of ovarian cancer include the concept that it begins with the dedifferentiation of the cells overlying the ovary. During ovulation, these cells can be incorporated into the ovary, where they then proliferate. Ovarian cancer typically spreads to the peritoneal surfaces and omentum.
Ovarian carcinoma can spread by local extension, lymphatic invasion, intraperitoneal implantation, hematogenous dissemination, and transdiaphragmatic passage. Intraperitoneal dissemination is the most common and recognized characteristic of ovarian cancer. Malignant cells can implant anywhere in the peritoneal cavity but are more likely to implant in sites of stasis along the peritoneal fluid circulation. As discussed later, these mechanisms of dissemination represent the rationale to conduct surgical staging, debulking surgery, and intraperitoneal administration of chemotherapy. In contrast, hematogenous spread is clinically unusual early on in the disease process, although it is not infrequent in patients with advanced disease.
EPITHELIAL OVARIAN CANCER
Epithelial tumors represent the most common histology (90%) of ovarian tumors. Other histologies include the following:
- Sex-cord stromal tumors
- Germ cell tumors
- Primary peritoneal carcinoma
- Metastatic tumors of the ovary
Epithelial ovarian cancer is thought to arise from epithelium covering the ovaries, which is derived from the coelomic epithelium in fetal development. This coelomic epithelium is also involved in formation of the Müllerian ducts, from which the Fallopian tubes, uterus, cervix, and upper vagina develop.
Five main histologic subtypes, which are similar to carcinoma, arise in the epithelial lining of the cervix, uterus, and fallopian tube, as follows:
- Serous (from fallopian tube)
- Endometrioid (endometrium)
- Mucinous (cervix)
- Clear cell (mesonephros)
Some variation is observed in the patterns of spread and disease distribution within the various histologic subtypes.
Epithelial tumors are found as partially cystic lesions with solid components. The surface may be smooth or covered in papillary projections (see the image below), and the cysts contain fluid ranging from straw-colored to opaque brown or hemorrhagic.
OVARIAN CANCER SYMPTOMS
Early-stage ovarian cancer rarely causes any symptoms. Advanced-stage ovarian cancer may cause few and nonspecific symptoms that are often mistaken for more common benign conditions, such as constipation or irritable bowel.
Signs and symptoms of ovarian cancer may include:
- Abdominal bloating or swelling
- Quickly feeling full when eating
- Weight loss
- Discomfort in the pelvis area
- Changes in bowel habits, such as constipation
- A frequent need to urinate
OVARIAN CANCER DIAGNOSIS
The GP (general practitioner) will carry out a vaginal examination and check for any visible abnormalities in the uterus or ovaries. The doctor will also check the patient’s medical history and family history. Further tests will be ordered – these are usually done by a gynecologist – a doctor who specializes in treating diseases of the female reproductive organs.
If the woman is diagnosed with ovarian cancer the doctor will want to identify its stage and grade. The stage of a cancer refers to the cancer’s spread while the grade refers to how aggressively it is spreading. By identifying the stage and grade of the cancer the doctor will be able to decide on the best treatment. The stage and grade of ovarian cancer alone cannot predict how it is going to develop.
The following tests are used to diagnose ovarian cancer:
There is a cancer marker called CA 125 (cancer antigen 125) which is made by certain cells in the body. A high blood level of CA 125 may indicate the presence of cancer, but could also be due to something else, such as infections of the lining of the abdomen and chest, menstruation, pregnancy, endometriosis, or liver disease. This blood test is just one test among others, designed to help the doctor make a diagnosis. Normal blood levels of CA125 alone do not definitely mean there is no cancer either. They are just indications.
This is a device that uses high frequency sound waves which create an image on a monitor of the ovaries and their surroundings. A transvaginal ultrasound device may be inserted into the vagina, while an external device may be placed next to the stomach. Ultrasound scans help doctors see the size and texture of the ovaries, as well as any cysts
Laparoscopy and possibly Endoscopy
A laparoscope – a thin viewing tube with a camera at the end – is inserted into the patient through a small incision in the lower abdomen. The doctor can examine the ovaries in detail, and can also take a biopsy (extract a small sample of tissue for examination). The patient will undergo a general anesthetic for this procedure. The doctor may carry out an endoscopy to determine whether the cancer has spread to the digestive system.
If the patient has had bleeding from the rectum, or constipation the doctor may order a colonoscopy to examine the large intestine (colon). The colonoscope – a thin tube with a camera at the end – will be inserted into the rectum.
Abdominal fluid aspiration
If the patient’s abdomen is swollen the doctor may decide to carry out this test. A build up of fluid in the abdomen might indicate that the ovarian cancer has spread. A thin needle goes through the skin into the abdomen and a sample of the liquid is extracted. Some of the liquid may be drained into a bag if there is a lot of it (abdominal tap). The fluid is checked in the laboratory for cancer cells.
This test will help the doctor see if the cancer has spread to the lungs, or to the pleural space surrounding the lungs.
CT (computerized tomography) scan
X-rays are used to create a 3-dimensional picture of the target area.
MRI (magnetic resonance imaging) scan
Magnets and radio waves produce 2-dimensional and 3-dimensional pictures of the target area.
OVARIAN CANCER TREATMENT
Treatment of ovarian cancer usually involves a combination of surgery and chemotherapy.
Treatment generally involves removing both ovaries, the fallopian tubes, the uterus as well as nearby lymph nodes and a fold of fatty abdominal tissue (omentum) where ovarian cancer often spreads. Your surgeon also will remove as much cancer as possible from your abdomen.
Less extensive surgery may be possible if your ovarian cancer was diagnosed at a very early stage. For women with stage I ovarian cancer, surgery may involve removing one ovary and its fallopian tube. This procedure may preserve the ability to have children.
After surgery, you’ll likely be treated with chemotherapy to kill any remaining cancer cells. Chemotherapy drugs can be injected into a vein or directly into the abdominal cavity or both.
Chemotherapy may be used as the initial treatment in some women with advanced ovarian cancer.