Ovarian cancer is the fifth leading cause of cancer death in women, the leading cause of death from gynecological malignancy, and the second most commonly diagnosed gynecologic malignancy (The Merck Manual of Diagnosis and Therapy Section 18. Gynecology And Obstetrics Chapter 241. Gynecologic Neoplasms).
It is idiopathic, meaning that the exact cause is usually unknown. The disease is more common in industrialized nations, with the exception of Japan. In the United States, females have a 1.4% to 2.5% (1 out of 40-60 women) lifetime chance of developing ovarian cancer.
More than half of the deaths from ovarian cancer occur in women between 55 and 74 years of age and approximately one quarter of ovarian cancer deaths occur in women between 35 and 54 years of age.
The risk for developing ovarian cancer appears to be affected by several factors.
The link to the use of fertility medication, such as clomiphene citrate, has been controversial. An analysis in 1991 raised the possibility that use of drugs may increase the risk for ovarian cancer. Several cohort studies and case-control studies have been conducted since then without providing conclusive evidence for such a link.
There is good evidence that genetic factors are important. Carriers of certain mutations of the BRCA1 or the BRCA2 gene, more frequent in some populations (e.g. Ashkenazi Jewish women) are at a higher risk of both breast cancer and ovarian cancer, often at an earlier age than the general population. Patients with a personal history of breast cancer or a family history of breast and/or ovarian cancer, especially if at a young age, may have an elevated risk. A strong family history of uterine cancer, colon cancer, or other gastrointestinal cancers may indicate the presence of a syndrome known as hereditary nonpolyposis colorectal cancer (HNPCC, also known as Lynch II syndrome), which confers a higher risk for developing ovarian cancer.
Other factors that have been investigated, such as talc use, asbestos exposure, high dietary fat content, and childhood mumps infection, are controversial and have not been definitively proven.
Ovarian cancer is classified according to the histology of the tumor (ICD-O codes). Histology dictates many aspects of clinical treatment, management, and prognosis.
Ovarian tumors can be classified by their presumed cell of origin. The main categories are, surface epithelial-stromal tumours, sex cord-stromal tumours (ICD-O 8590), germ cell tumours (ICD-O 9060-9090) and secondary or metastatic tumours.
Surface epithelial-stromal tumours are the most common and prototypic ovarian cancers. They are thought to originate from the ovarian surface lining, and include serous cystadenocarcinoma (8441/3), and mucinous cystadenocarcinoma (8470/3). The abdominal cavity is lined with the same cells that make up the ovarian surface lining, and it is possible to have cancer begin there, in which case, it is called primary peritoneal cancer. Treatment, however, is basically the same as treatment for ovarian cancer.
Sex cord-stromal tumors (8590) include lesions that are hormonally active such as the estrogen-producing granulosa cell tumor (8620/3) and the virilizing Sertoli-Leydig cell tumor or arrhenoblastoma.
Germ cell tumors (9060-9090) of the ovary originate from germ cells and tend to occur in young women and girls. These tumors represent approximately 5% of ovarian cancers. They tend to be well encapsulated and many are benign, hence prognosis than for other ovarian tumors.
There are also mixed tumors secondary or metastatic tumors.
Ovarian cancer often is primary, but can also be secondary, i.e. the result of metastasis from primary cancers elsewhere in the body, for example, from breast cancer, or from gastrointestinal cancer, in which case the ovarian cancer is a Krukenberg cancer.
Historically ovarian cancer was called the “silent killer” because symptoms were not thought to develop until the chance of cure was poor. However, recent studies have shown this term is untrue and that 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, difficulty eating or feeling full quickly, urinary symptoms (urgency or frequency).
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.
Ovarian cancer at its early stages (I/II) is difficult to diagnose until it spreads and advances to later stages (III/IV). This is due to the fact that most of the common symptoms are non-specific.
Ovarian cancer has a poor prognosis. It is disproportionately deadly because symptoms are vague and non-specific, hence diagnosis is late. More than 60% of patients presenting with this cancer already have stage III or stage IV cancer, when it has already spread beyond the ovaries.
Ovarian cancers that are malignant shed cells into the naturally occurring fluid within the abdominal cavity. These cells can implant on other abdominal (peritoneal) structures included the uterus, urinary bladder, bowel, lining of the bowel wall (omentum) and can even spread to the lungs. These cells can begin forming new tumor growths before cancer is even suspected.
More than 50% of women with ovarian cancer are diagnosed in the advanced stages of the disease because no cost-effective screening test for ovarian cancer exists. The five year survival rate for all stages is only 35% to 38%. If, however, diagnosis is made early in the disease, five-year survival rates can reach 90% to 98%.
Hence, it would be advantageous to have method for the analysis of ovarian cancer disorders as well as a method for detection of ovarian cancer in a subject.