Ovarian cancer

Ovarian cancer accounts for 4.2 percent of all cancers in women and has the highest incidence rate among all genitourinary cancers in women following cervical cancer in Korea. There is growing concern about ovarian cancer as its incidence rate is on the rise every year with approximately 1,400 newly-diagnosed patients annually, whereas the incidence rate of cervical cancer is gradually decreasing.

The ovaries are small organs located in the female pelvis which are found in pairs on either side of the uterus. In a healthy, reproductive female, the ovaries release an ovum once a month on average where fertilization can occur when an ovum meets a sperm. They also play an important role in the production of estrogen.

Ovarian cancer is classified as epithelial ovarian carcinoma, which occurs in the cortex of the ovaries; and non-epithelial cancer, which can be further classified as a germ cell tumor or sex cord-stromal tumor. Epithelial ovarian carcinoma accounts for 90 percent of all ovarian cancers and it can occur in all age groups but rarely before adolescence and mostly between the ages of 40 and 70, with the highest incidence rate between the ages of 56 and 60. 

The suspected cause of ovarian cancer is continuous ovulation and so the risk is higher if there is more ovulation. This applies to middle-aged women who have never given birth or completed a pregnancy. Also, family history, aging, endometrial cancer and a medical history of breast cancer are considered risk factors for ovarian cancer.

Signs and symptoms of ovarian cancer are often absent in the early stages of the disease. As the disease progresses, there may be pain, abdominal distension, vaginal bleeding and other possible symptoms. As a result, over two-thirds of all ovarian cancers are detected at later stages (III/IV) when the treatment is often difficult. Therefore the necessity for prevention and early detection is unquestionable.

Ovarian cancer is difficult to diagnose at its early stages using a simple cytological test like a Pap smear for testing cervical cancer. Routine pelvic examinations, trans-vaginal ultrasounds and CA-125 (biomarker) blood tests are used for early detection of ovarian cancer but there is no definitive and perfect diagnostic method for ovarian cancer. Another difficulty in ovarian cancer detection is that the tissue of the ovary must be obtained by direct surgical procedures such as laparotomy or laparoscopy for pathology testing to classify the ovarian tumor as benign or malignant. But the chance for early detection can be raised if an annual visit to an obstetrics and gynecology clinic is made and a pelvic examination and ultrasonography are performed. Therefore it is important to have routine check-ups.

The ovaries are often observed with non-specific cysts related to menstrual cycle, thus not all patients with ovarian tumors undergo surgery; but those with several indications for exploratory surgery do. Indications include: an ovarian tumor observed in a patient with menopause; the size of the tumor rapidly increases during a two- to three-month period of observation; the tumor is larger than 8 cm even if it is a cyst; the tumor has a mixed shape or solid content in ultrasound examinations; a malignancy is suspected in a color Doppler imaging, CT or MRI scan; the level of CA-125 is above 100 U/ml on a CA-125 blood test in a menopausal woman.

If the tumor is diagnosed as ovarian cancer during the laparotomy, complete surgical staging is necessary for future treatments. Ovarian cancer staging is as follows: stage I, if limited to one or both ovaries; stage II, if spread to tissues in the pelvis or implants onto uterus or fallopian tubes; stage III, if peritoneal implants beyond pelvis onto diaphragm, omentum or lymph nodes; stage IV, if there is any distant metastasis.

When diagnosed with ovarian cancer, aggressive surgical excision is important for following chemotherapy and thus improving the survival rate.

Low-grade early stage I ovarian cancers are not treated with chemotherapy but from late stage I onwards, all ovarian cancers are treated with chemotherapy. Surgical and post-surgical adjuvant chemotherapy with paclitaxel and carboplatin are the most basic treatment methods for ovarian cancer.

Recently the progression and onset of cancers have been researched down to the molecular and genetic levels and numerous important genetic alterations have been identified. Using these, various molecular target therapy for cancer is now being investigated. For example, three recent randomized clinical trials with Bevacizumab (a molecular drug for blocking new vessel formation of tumors) have been shown to prolong progression-free survival in patients with primary and recurrent ovarian cancer. Because ovarian cancer has a poor prognosis compared to other cancers, the development of this kind of molecular treatment is more important.

The treatment of ovarian cancer is done using surgery and chemotherapy. However, 75 percent of patients are diagnosed at stage III or later when the disease progression is very rapid. Therefore, the overall five-year survival rate of ovarian cancer is only 39 percent and accounts for 57 percent of deaths in female reproductive organ cancers. Early identification is the key to a good treatment outcome, so it is important that efforts are made to identify the cancer during its early stages. All healthy women should have screening tests every year.

By Kim Byoung-gie

The author is a doctor at the department of obstetrics and gynecology at Samsung Medical Center and professor of Sungkyunkwan University School of Medicine. ― Ed.