Ovarian cancer is a malignant growth of the ovary. The cancer may be primary (arising in the ovary) or secondary (due to the spread of cancer from another part of the body).
The ovaries are a pair of almond-shaped glands situated on either side of the uterus immediately below the opening of the fallopian tubes. Each ovary contains numerous cavities called follicles, in which egg cells develop. The ovaries also produce the female sex hormones oestrogen and progesterone.
Incidence and causes
Ovarian cancer can occur at any age but is most common in women over 50 and in those who have never had children. A family history of cancer of the ovary, breast, or colon, especially in close relatives under 50, is an important risk factor. Having taken oral contraceptives in the past substantially reduces the risk.
In most cases, ovarian cancer causes no symptoms until it is widespread. The first symptoms may include vague discomfort and swelling in the abdomen; nausea and vomiting; and abnormal vaginal bleeding. The swelling may be due to the tumour itself or to ascites (excess fluid in the abdominal cavity).
Diagnosis and treatment
Diagnosis of ovarian cancer involves a physical examination, ultrasound scanning, and blood tests to measure levels of a substance produced by the tumour.The tumour is usually surgically removed, along with the uterus and the unaffected ovary. In younger women whose cancer is found early, it is sometimes possible to perform less radical surgery and preserve fertility. The extent of spread within the abdomen is assessed during surgery. Surgery is followed by chemotherapy, unless the cancer was found at a very early stage. Platinum-based drugs, which are combined with paclitaxel, are usually given. Survival rates depend on the type of tumour and how advanced it is at the time of diagnosis; as the disease is often quite advanced, less than one in four women survive for more than five years.
Ovarian cancer in more detail
Ovarian cancer is the second most common of all genital cancers and accounts for 10-15% of all gynaecological cancers in developing countries including India. Over the past two decades there has been an increase in the incidence as well as survival rate amongst women with ovarian cancer.
The risk of a woman developing cancer of the ovary in her lifetime is around 1:70 to 1:100. Patients of low parity, decreased fertility and delayed childbearing appear to be more predisposed. There appears to be a familial predisposition to the disease.
Association between ovarian cancer, colon, breast cancer and endometrial adenocarcinoma has also been recognized. In such families cancers tend to occur at a younger age less than 40 years. Five to ten per cent malignant ovarian tumours are genetic, and gene BRCA-1 and BRCA-2 mutations are implicated. BRCA-1 gene mutation on chromosome-17 and BRCA-2 gene mutation on chromosome 13 are noted. With one family affected, the lifelong risk is 2.7%, but it goes up to 13% with two or more relations. The risk increases with age up to 70 years.
The Pattern of inheritance is autosomal dominant, and ovarian tumour occurs at a younger age below 50 years, associated with a risk of breast and colonic cancer. Occurrence of mumps prior to menarche and multiple ovulation in IVF programme appear to increase the risk of ovarian malignancy in later life.
Geographical variations are suggestive of the fact that high dietary fat intake, the use of talc on the perineum and industrial pollution are environmental factors implicated in the high incidence in the West.
Protective factors include multiparity, breastfeeding, anovulation and use of oral contraceptive pills. These contraceptive pills reduce its incidence by 40-50% and the beneficial effect extends for about 10 years after stoppage of pills. The effect is also dose dependent.
Late diagnosis and early metastasis are responsible for the poor survival rates. Since no satisfactory method of mass screening has as yet been developed, only 20% of cases are confined to the ovaries at the time of diagnosis.
Eighty per cent of ovarian malignancies are of epithelial origin and almost 80% are in Stage III or IV at the time of diagnosis. In younger patients, germ cell tumours are more frequently encountered when tumour markers like alpha-fetoproteins, CEA and hCG are useful.
Eighty per cent are primary tumours and 20% are secondary from the breast, colon, stomach and uterus. Before menarche, 10% are malignant, during reproductive years 15% are malignant but after menopause it is rises to 50%. Bilateral tubectomy or hysterectomy reduces the risk of ovarian cancer if the theory of mutagen ascending the genital tract is correct.