Ovarian Cancer Poses Deadly Threat
Edition: October 2001 - Vol 9 Number 10
Author: Laura Thill
Half of all women diagnosed with ovarian cancer are expected to die within five years, according to the Ovarian Cancer National Alliance. Ranked among the deadliest of gynecologic cancers, the disease is the fifth leading cause of cancer-related death among U.S. women.
While the numbers of diagnosed cases of ovarian cancer appears to be in decline from 25,000 in 1999 to 23,100 in 2000 14,000 American women alone died of it in 2000.
There are no sufficient means for screening ovarian cancer, according to E.E Partridge and M.N. Barnes [CA Cancer J Clin 1999 Sept.-Oct; 49 (5): 297-320]. Because it tends to be asymptomatic, the disease often is well advanced by the time it is detected. Whereas 90 percent of women survive over five years when their cancer is discovered before it spreads to the ovaries, only 25 percent of cases in the United States actually are diagnosed at an early stage.
What Is Ovarian Cancer?
Ovarian cancer is a malignant tumor that originates in the ovaries, according to the National Cancer Institute (NCI). The cancer cells break away from the ovary and spread to other tissues and organs a process called shedding, according to the NCI. During shedding, ovarian cancer seeds or forms new tumors on the peritoneum (large membrane lining the abdomen) and on the diaphragm (thin muscle separating the chest from the abdomen). Fluid sometimes collects in the abdomen a condition called ascites and causes abdominal bloating or swelling.
Once the cancer cells invade the bloodstream, or lymphatic system, they can easily pervade, and form new tumors in, other areas of the body.
Types of Ovarian Cancer
There are three basic kinds of ovarian tumors:
Epithelial tumors originate from epithelial cells or those covering the outer surface of the ovary. Epithelial ovarian carcinoma (EOC) is the most common type of ovarian cancer, according to the Ovarian Cancer National Alliance, accounting for 65 percent to 95 percent of all cases. The following table outlines the percentage of cases that each type of EOC accounts for.
Percent of EOC Cases
Depending on their level of differentiation or maturity, the epithelial carcinomas are further categorized by grade:
Grade 0. These borderline tumors have low malignant potential and are extremely well differentiated.
Grade 1. Well differentiated.
Grade 2. Moderately differentiated.
Grade 3. Poorly differentiated.
Source: Ovarian Cancer National Alliance. www.ovariancancer.org.
Well-differentiated tumors carry the best prognoses. Clear cells and undifferentiated cancers have very poor prognoses.
Germ cell tumors originate from the cells that form the eggs and account for about five percent of ovarian cancers. Germ cell carcinomas occur most often in women in their early twenties. There are six basic kinds of germ cell carcinoma, three of which are most common. These include:
Endodermal sinus tumors.
Often, tumors that emerge in the germ cells are benign.
Stromal tumors, responsible for five percent of ovarian cancers, grow in the connective tissue cells that hold the ovary together. They also develop in estrogen- and progesterone-producing cells. The two most common forms of stromal carcinoma are granulose cell tumors and Sertoli-Leydig tumors. Seventy percent of these cancers are diagnosed in Stage 1, according to the Ovarian Cancer National Alliance.
While all women are at risk for ovarian cancer, some factors may increase their odds of developing this disease:
Age. Fifty-six percent of women diagnosed are over 65 years.
Family or personal history of ovarian, endometrial, breast or colon cancer.
Never having children or a history of infertility.
Other factors believed to contribute to ovarian cancer, but as of yet unproven, include:
Use of talc.
Use of hormone replacement therapy after menopause.
Use of fertility drugs (although infertility itself may be the source of the disease).
It may not be possible to eliminate all risk for ovarian cancer, but the Ovarian Cancer National Alliance lists the following options for reducing one's risk:
Oral contraceptives. These are said to reduce the risk of ovarian cancer by about five to 10 percent. Five years on the pill may halve the risk for this disease.
Pregnancy and breast feeding. Women who have had three or four full-term pregnancies are said to have a 50 percent lower risk rate.
Prophylactic oophorectomy (removal of ovaries).
Symptoms and Diagnosis
Symptoms of this disease often are mild or don't even exist until the cancer has matured to an advanced stage.
Current research has attempted to determine the usefulness of measuring CA-125 levels in the blood. Often, higher-than-normal amounts of this substance referred to as a tumor marker exist in the blood of women with ovarian cancer, according to the National Cancer Institute (NCI).
Transvaginal ultrasound is also being considered as a possible tool for early detection of ovarian cancer. The NCI lists the following possible symptoms of ovarian cancer:
Abdominal discomfort or pain, such as gas, indigestion, pressure, swelling, bloating and cramps.
Nausea, diarrhea, constipation or frequent urination.
Loss of appetite or unexplained feeling of fullness.
Weight gain or loss for no apparent reason.
Abnormal vaginal bleeding.
It is possible, however, for these symptoms to be caused by less serious conditions. Some diagnostic tests available to evaluate the possibility of ovarian cancer include the following:
Lower GI series of bacterium enema (as a series of x-rays of the colon and rectum).
CT or CAT scan.
Staging Ovarian Cancer
Ovarian cancer is staged at surgery based on International Federation of Gynecology and Obstetrics classifications. The stage of cancer at the time of diagnosis is a major indicator of prognosis.
Cancer is limited to one or both ovaries.
IA. Cancer is limited to one ovary and the tumor is confined within the ovary. No ascites is present and the tumor surface is unruptured.
IB. Cancer is limited to both ovaries without any tumor on their outer surfaces. No ascites exists and the tumor surface is unruptured.
IC. The tumor is classified as either stage IA or IB and the tumor exists on the outer surface of one or both ovaries; and/or at least one tumor has ruptured; and/or ascites is present or abdominal washings contain malignant cells.
The tumor exists in one or both ovaries, as well as on other pelvic structures.
IIA. Cancer has invaded the uterus and/or fallopian tubes.
IIB. Cancer has reached the bladder or rectum.
IIC. In addition to being classified stage IIA or IIB, the tumor exists on the outer surface of one or both ovaries; and/or at least one of the tumors has ruptured; and/or there is ascites or abdominal washings containing malignant cells.
The tumor has spread to one or both ovaries. In addition, cancer has moved beyond the pelvis to the abdominal lining and/or cancer has spread to the lymph nodes.
IIIA. Cancer is visible on one or both ovaries, but not in the abdomen. However, small deposits of cancer in the abdomen can show up in biopsies. Cancer has not yet spread to the lymph nodes.
IIIB. Cancer is visible in one or both ovaries, and deposits 2 centimeters in diameter or less are visible in the abdomen. Cancer has not yet spread to the lymph nodes.
IIIC. The tumor exists in one or both ovaries. Also, cancer has spread to the lymph nodes and/or deposits in the abdomen exceed 2 centimeters in diameter.
Cancer affects one or both ovaries. The disease also has metastasized to the liver or lungs. Ovarian cancer cells may be found in the pleural fluid surrounding the lungs.
Source: The Ovarian Cancer National Alliance. www.ovariancancer.org.
The course of treatment for ovarian cancer depends on the stage of the disease, according to the NCI. Treatment usually includes surgery and/or chemotherapy or radiation therapy.
Predictive Gene Testing
Over 4,000 diseases ovarian cancer included are believed to stem from genes passed along from one generation to the next.
The most common gene mutation involves a single changed base in the DNA, according to the NCI and the National Center for Human Genome Research. The consequences of a gene mutation depend on how it affects the body's protein (which interacts with thousands of other proteins to maintain a healthy body) and how crucial that particular protein is to healthy living.
Over the past 20 years, researchers have explored gene mutations, making it increasingly possible to detect some diseases and, in various instances, predict others. Gene testing raises many people's hopes for saving lives through prevention and early detection of disease. At the same time, however, it raises questions for those who must cope with a greater understanding of the genetic structure they've inherited.