OVARIAN CANCER

Ovarian cancer is a cancerous growth arising from different parts of the ovary.

The most common form of ovarian cancer (≥80%) arises from the outer lining (epithelium) of the ovary. Other forms arise from the egg cells ( germ cell tumor).

In 2004, 25,580 new cases were diagnosed and 16,090 women died of ovarian cancer. The risk increases with age and decreases with pregnancy. Lifetime risk is about 1.6%, but women with affected first-degree relatives have a 5% risk. Women with a mutated BRCA1 or BRCA2 gene have a 25% risk. Ovarian cancer is the fifth leading cause of death from cancer in women and the leading cause of death from gynecological cancer.

In early stages ovarian cancer is associated with abdominal distension.

10-year relative survival ranges from 84.1% in stage IA to 10.4% in stage IIIC.

Ovarian cancer causes non-specific symptoms. Early diagnosis would result in better survival, on the assumption that stage I and II cancers progress to stage III and IV cancers (but this has not been proven). Most women with ovarian cancer report one or more symptoms such as abdominal pain or discomfort, an abdominal mass, bloating, back pain, urinary urgency, constipation, tiredness and a range of other non-specific symptoms, as well as more specific symptoms such as pelvic pain, abnormal vaginal bleeding or involuntary weight loss. There can be a build-up of fluid (ascites) in the abdominal cavity.

Diagnosis of ovarian cancer starts with a physical examination (including a pelvic examination), a blood test (for CA-125 and sometimes other markers, and transvaginal ultrasound. The diagnosis must be confirmed with surgery to inspect the abdominal cavity, take biopsies (tissue samples for microscopic analysis) and look for cancer cells in the abdominal fluid. Treatment usually involves chemotherapy and surgery, and sometimes radiotherapy.

In most cases, the cause of ovarian cancer remains unknown. Older women, and in those who have a first or second degree relative with the disease, have an increased risk. Hereditary forms of ovarian cancer can be caused by mutations in specific genes (most notably BRCA1 and BRCA2, but also in genes for hereditary nonpolyposis colorectal cancer). Infertile women and those with a condition called endometriosis, those who have never been pregnant and those who use postmenopausal estrogen replacement therapy are at increased risk. Use of combined oral contraceptive pills is a protective factor. The risk is also lower in women who have had their uterine tubes blocked surgically .

Symptoms

Studies on the accuracy of symptoms

Two case-control studies, both subject to results being inflated by spectrum bias, have been reported. The first found that women with ovarian cancer had symptoms of increased abdominal size, bloating, urge to pass urine and pelvic pain. The smaller, second study found that women with ovarian cancer had pelvic/abdominal pain, increased abdominal size/bloating, and difficulty eating/feeling full. The latter study created a symptom index that was considered positive if any of the six (6) symptoms "occurred >12 times per month but were present for <1>

Ovarian Cancer Symptoms Consensus Statement

In 2007, the Gynecologic Cancer Foundation, Society of Gynecologic Oncologists and American Cancer Society originated the following consensus statement regarding the symptoms of ovarian cancer.

Ovarian cancer is called a “silent killer” because symptoms were not thought to develop until the disease had advanced and the chance of cure or remission poor. However, the following symptoms are much more likely to occur in women with ovarian cancer than women in the general population. These symptoms include:

• Bloating
• Pelvic or abdominal pain
• Pain in the back or legs
• Diarrhea, gas, nausea, constipation, indigestion
• Difficulty eating or feeling full quickly
• Urinary symptoms (urgency or frequency)
• Pain during sex
• Abnormal vaginal bleeding
• Trouble breathing

Women with ovarian cancer report that symptoms are persistent and represent a change from normal for their bodies. The frequency and/or number of such symptoms are key factors in the diagnosis of ovarian cancer. Several studies show that even early stage ovarian cancer can produce these symptoms. Women who have these symptoms almost daily for more than a few weeks should see their doctor, preferably a gynecologist. Prompt medical evaluation may lead to detection at the earliest possible stage of the disease. Early stage diagnosis is associated with an improved prognosis.

Several other symptoms have been commonly reported by women with ovarian cancer. These symptoms include fatigue, indigestion, back pain, pain with intercourse, constipation and menstrual irregularities. However, these other symptoms are not as useful in identifying ovarian cancer because they are also found in equal frequency in women in the general population who do not have ovarian cancer

Screening

Routine screening of the general population is not recommended by any professional society. This includes the U.S. Preventitive Services Task Force, the American Cancer Society, the American College of Obstetricians and Gynecologists, and the National Comprehensive Cancer Network.

No trial has shown improved survival for women undergoing screening.

Screening tests include the CA-125 marker, transvaginal ultrasound, and combinations of markers such as OvaSure (LabCorp). A definitive diagnosis requires surgical excision of the ovaries and fallopian tubes, so a positive screening test must be followed up by surgery.

The purpose of screening is to discover ovarian cancer in early stages, when it is more curable, on the hypothesis that early-stage cancer develops into later-stage cancer. However, it is not known whether early stage ovarian cancer evolves to later stage cancer, or whether stage III (peritoneal cavity involvement) arises as a diffuse process.

The goal of ovarian cancer screening is to detect ovarian cancer at stage I. Several large studies are ongoing, but none have recommended screening. In 2009, however, Menon et al. reported from the UKCTOCS that utilizing mutimodal screening, in essence first performing annual CA 125 testing, followed by ultrasound imaging on the secondary level, the positive predictive value was 35.1% for primary invasive epithelial ovarian and tubal carcinoma, making such screening feasible. However, it remains to be seen if such screening is effective to reduce mortality.

Diagnosis

Ovarian cancer at its early stages(I/II) is difficult to diagnose until it spreads and advances to later stages (III/IV). This is because most of the common symptoms are non-specific.

When an ovarian malignancy is included in the list of diagnostic possibilities, a limited number of laboratory tests are indicated. A complete blood count (CBC) and serum electrolyte test should be obtained in all patients.

The serum BHCG level should be measured in any female in whom pregnancy is a possibility. In addition, serum alpha-fetoprotein (AFP) and lactate dehydrogenase (LDH) should be measured in young girls and adolescents with suspected ovarian tumors because the younger the patient, the greater the likelihood of a malignant germ cell tumor.

A blood test called CA-125 is useful in differential diagnosis and in follow up of the disease, but it by itself has not been shown to be an effective method to screen for early-stage ovarian cancer due to its unacceptable low sensitivity and specificity. However, this is the only available, widely-used marker currently.

Current research is looking at ways to combine tumor markers proteomics along with other indicators of disease (i.e. radiology and/or symptoms) to improve accuracy. The challenge in such an approach is that the very low population prevalence of ovarian cancer means that even testing with very high sensitivity and specificity will still lead to a number of false positive results (i.e. performing surgical procedures in which cancer is not found intra-operatively). However, the contributions of proteomics are still in the early stages and require further refining. Current studies on proteomics mark the beginning of a paradigm shift towards individually tailored therapy.

A pelvic examination and imaging including CT scan and trans-vaginal ultrasound are essential. Physical examination may reveal increased abdominal girth and/or ascites (fluid within the abdominal cavity). Pelvic examination may reveal an ovarian or abdominal mass. The pelvic examination can include a rectovaginal component for better palpation of the ovaries. For very young patients, magnetic resonance imaging may be preferred to rectal and vaginal examination.

To definitively diagnose ovarian cancer, a surgical procedure to take a look into the abdomen is required. This can be an open procedure ( laparotomy, incision through the abdominal wall) or keyhole surgery. During this procedure, suspicious areas will be removed and sent for microscopic analysis. Fluid from the abdominal cavity can also be analysed for cancerous cells. If there is cancer, this procedure can also determine its spread (which is a form of tumor staging).

Prevention

There are a number of ways to reduce or eliminate the risk of ovaran cancer. Pregnancy before the age of 25 as well as breastfeeding provides some reduction in risk. Tubal ligation and hysterectomy reduce the risk and removal of both ovaries (bilateral oophorectomy) eliminates the risk. The use of oral contraceptives (birth control pills) for five years or more decreases the risk of ovarian cancer in later life by 50%.