INTRODUCTION
Ovarian cancer has a prevalence rate of around 3% among all the cancers seen in women all over the world. Most of the ovarian tumors are non malignant or non cancerous. The tumors which are cancerous or have low malignant potential can prove to be life threatening due their spread to various sites within the body. The different categories of ovarian cancer are as follows: a) Epithelial ovarian tumor b) Ovarian germ cell tumor c) Ovarian stromal tumor
- Epithelial ovarian tumor: They can be either malignant or low malignant potential tumor. The tumors with low malignant potential are less threatening than the malignant one. Even if they reach other organs, they do not form a growth within the affected structure, they will remain confined to the lining of the organ. They are commonly seen in younger females and are quite rare. On the other hand almost 90% of the ovarian cancers belong to the category of malignant epithelial tumor. They are again subdivided into four subtypes namely, serous, mucinous, endometroid and clear cell; serous being the commonest type among them. The tumors are graded on the basis of the similarities between the appearance of the normal tissue and that of the tumorous tissue. Grade 1 is assigned to the tumor which very closely resembles the normal tissue; grade 3 has the least resemblance and grade 2 being the intermediate one. The prognosis worsens proportionally with the dissimilarity among the appearance of the normal and cancerous tissue when seen under a microscope. The tumor is most likely to spread to the pelvic organs and even to the abdominal organs. In severe cases the tumor may reach up to the liver, lungs, brain, bone or skin. When the spread reaches the abdomen it can cause ascites.
- Ovarian germ cell tumor: Mostly ovarian germ cell tumors are benign in nature; very rarely they can be malignant. Only 2%of the ovarian cancers can be germ cell tumors. They generally have a good prognosis with a high survival rate. They can be further classified into dysgerminomas, endodermal sinus tumors, teratomas or choriocarcinomas.
- Ovarian stromal tumor: About 1% of the ovarian cancers belong to this category. Most commonly seen in elderly women above the age of 50. These tumors may lead to heavy vaginal bleeding due to their tendency to secrete estrogen. They may even produce testosterone which will lead to development of male pattern of hair growth or stopping of normal menstrual cycles. The malignant variety of these tumors have subtypes, namely, granulose cell tumor, granulose theca tumor, Sertolli- Leydig cell tumors.
Narod et al state that oral contraceptives can have preventive effects on ovarian cancer, but the efficacy of oral contraceptive pills on hereditary forms of ovarian cancer was debatable. In their research, they established the fact that OCPs do prevent the chances of occurrence of ovarian cancer even in patients who are carrier of the gene responsible for hereditary ovarian cancer (Narod et al., 1998).
The number of successful full term conceptions has been observed to have a positive effect on ovarian cancer. With each successive pregnancy the risk for ovarian cancer reduces proportionally. Thus nulliparity accounts for a higher risk of the disease. Certain case control and cohort studies have shown the link in between dietary intake and occurrence of ovarian cancer. Intake of fat rich diet, starchy food, food with high glycemic value, carbohydrate and protein rich diet are responsible for increasing the risk of ovarian cancer. Whereas consumption of fruits and vegetables decrease the risk substantially (Bray et al., 2005).
INCIDENCE AND PREVALENCE
Europe and Northern America shows the highest incidence rate of ovarian cancer in the world with Malta showing an age- standardized rate or 11.8 per 100,000 (World Cancer Research Fund International, 2012). Ovarian cancer is the fifth most prevalent cancer in European women. As high as 65,600 new cases were recorded in the year 2012. The prevalence is higher in aged females than the younger ones. The incidence is recorded to be higher in the women of higher socioeconomic strata than that of the lower ones; the reason could be less number of children or lower parity in the affluent women. The increase in the number of ovarian cancer cases have raised by 32% from 1975-77 and 1977-79 and since then a fall of 11% has been observed from 1997-1999 and 2009-2011. Overall, in the last decade a fall of 10% is recorded in Europe (Cancer Research UK, 2014).
MORTALITY
The number of deaths from ovarian cancer is higher in older females than the younger population. Over the last decade, the mortality percentage has reduced in Europe by almost 20%. A significant fall of 25% was observed between 1971-73 and 2010-12. Ovarian cancer ranks 6th among the cancer deaths in European women. The survival rate of five years and above is now commonly seen in young females. The survival rate is indirectly proportional to the age at which the patient is diagnosed. Although survival rates are seen to be increasing with time. Patients surviving up to 10 years after the diagnosis have also been reported, but such cases usually involve the younger patients.
RISK FACTORS: The following factors were taken into consideration as they were thoroughly studied and researches were made upon them by various scholars. Each factor taken here has been scrutinized by repeated trials; large numbers of patients were taken into consideration to reach up to the conclusions. They were followed up at regular intervals, al the necessary tests were performed in order to confirm the observations.
- Age: As described earlier, higher the age more are the chances of development of the disease.
- Family history: Though rare, but the women with a positive family history of ovarian cancer runs a higher risk of developing the same.
- Genetic factors: Mutations in BRCA1 or BRCA2 gene have also found to be responsible for development of the cancer.
- Hormonal factors: Higher the body is subjected to ovulation, higher is the risk of ovarian cancer. Thus any factor that reduces the incidence of ovulation or affects ovulation proves to be helpful in alleviating the risk. For example, late menarche or early menopause, multiparity, OCPs and breast feeding.
- Fertility: Nulliparous females possess higher risk of the disease. Studies have shown that the effect of nulliparity on ovarian cancer cannot be reduced by the means of infertility drugs or assisted reproductive technologies.
- Breast density: As observed in a cohort study, higher breast density also increases the risk (Wernli et al., 2013). A proper methodology was followed in their research by Wernli et al., a considerable number of patients were studied, and the women had to undergo mammography. The results were studied in the light of the age groups of the affected women along with their breast densities. The results indicated the risk factors to be higher in a specific age group.
- Tobacco: A strong link between tobacco and ovarian cancer has been established in various studies conducted in different parts of the world. Tobacco consumption has been found to be a direct cause of the disease (Jordan, Whiteman, Purdie, Green & Webb, 2006). Although the fact that tobacco has role in ovarian cancer was denied earlier, but in a number of successive studies, done with a larger section of women, it was proved that there definitely exists a link between the two. The fact was tested by repeated and extensive studies by Jordan and co- researchers. The result was a concrete proof of the association. The incidences of the different types of ovarian epithelial cancers were recorded in the patients with a habit of tobacco consumption. Also condemning the habit of smoking has shown positive results with better prognosis.
- Height: The risk of ovarian cancer increases by 7-10% with every 5cm increase in the height. This data was revealed in the meta- analysis and pooled analysis ( Wiren et al., 2013). Studies were undertaken with women from seven different regions, follow ups were over quite an extensive time period. It was observed that height has a direct role in cancer of any kind. Different types of cancer and mortality rates associated with them were found in women who were comparatively taller.
- Obesity: A successive number of studies stated that premenopausal obese women are more prone to ovarian cancer than postmenopausal obese females (Schouten et al., 2008). In the study it was observed that women with a height of less than 1.6 meters had lesser incidence of ovarian cancer than in women with a height of above 1.7 meters. The study was conducted with women suffering from ovarian epidermal cancer. A series of 12 cohort studies were undertaken to reach up to the conclusion. Patients from North America and Europe were taken as subjects for study.
- Diet: Diet rich in fats and starch complex increases the risk manifolds.
- History of cancer: Females having a history of breast cancer show greater risk of development of ovarian cancer. The risk increases further if it is accompanied by positive family history of either breast or ovarian cancer (Bergfeldt et al., 2002). A large number of patients were studied to reach up to the conclusion, they were followed up over an extensive period of 6 years. Proper medical surveillance even suggested that a prophylactic oopherectomy can reduce the risk of developing ovarian cancer in patients with a history of breast cancer, thus establishing the findings with more conviction.
- Certain diseases: Diseases like endometriosis, diabetes and ovarian cysts predisposes the patients to ovarian cancer. Also intake of certain medications like NSAIDs or paracetamol may increase the chances of development of carcinoma.
REFERENCES
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