Each year around 163.500 new cancer cases are diagnosed in Turkey and the number is 14 million worldwide, and cancer is responsible for about 20% of the deaths
22. Cancer is a disease that requires a long struggle due to the health problems it brings along and its effect on the quality of life of the patients. Cancer affects all people, without age, gender, language, religion or race, and a considerable portion is also expected to emerge in underdeveloped countries
22.
Another important health problem of underdeveloped and developing countries is parasitic diseases. It has been reported that countries with especially insufficient infrastructure, in terms of public health, continue to have an important health problem and the prevalence is high 1-6. Parasitic infections, especially infections caused by intestinal protozoa, may cause severe clinical symptoms and fatal complications (such as persistent diarrhea and malabsorption) in cases of immunodeficiency, like in cancer patients, while exhibiting a mild and self-limiting clinical course in immunocompromised individuals 3,4,9.
It also increases the risk and prevalence of parasitic infections in immunocompetent individuals compared to the normal population 9,10. Studies on cancer patients around the world, have reported that the frequency of intestinal parasites varies from country to country and varies between 6.7-88.9% 1,5,9,17,19. In the south of Brazil and Sao Paulo, the prevalence was 61.6% and 66.7% respectively and it was reported as 6.7% and 10% in Central and Northwest Iran, respectively 1,5,9,17. In Saudi Arabia, the frequency of coccidian parasites in cancer patients with diarrhea is declared to be 88.9% 19. Although there are a few studies on intestinal parasites in immunosuppressive patients and pediatric cancer patients in Turkey, there are differences in the methods and types of parasites investigated 20,21,23,24. In two studies, the incidence of intestinal parasites was reported to be 22.5% 14 in immunosuppressed patients and 30.3% 20 in pediatric cancer patients. In a study investigating only Microsporidium spp. in cancer patients, the prevalence was 17.8% 16, and in another study investigating only Cryptosporidium parvum (C.parvum), prevalence it was found to be 12.3% by ELISA (Enzyme Linked Immunosorbent Assay) method and 7.8% by kinyoun acid fast staining method 23. In our study, the incidence of intestinal protozoa was 38.7% in adult patients diagnosed with cancer. The prevalence of intestinal protozoa in our study group is higher than the prevalence (4.0-22.4%) detected in the normal population in our country and our region (10-15). However, the study in which all intestinal parasites are investigated shows similarities to rates found in children with cancer 20.
Immunosuppression also changes the diversity of parasitic infectious agents in patients 3. Opportunistic pathogens, especially Cryptosporidium spp. and Microsporidium spp., predominate in immunocompetent individuals 1,4,9,16,17,19, while Entamoeba spp., Giardia intestinalis (G. intestinalis) and Blastocystis sp. are more commonly encountered in immunocompetent individuals (10-13, 21, 23). In our study, the most common intestinal protozoon was Blastocystis sp. (30.6%) followed by E. coli (7.2%) and G. intestinalis (4.5%). Microsporidium spp. and C. parvum were found in 3.6% and 1.8%, respectively. C. parvum 1,5,19, Blastocystis sp. 1,9 and G. intestinalis 17 have been reported as the most common intestinal protozoa in some studies in cancer patients. Sonmez et al. 23 reported the prevalence of cryptosporidiosis in diarrheal children with leukemia and lymphoma, diagnosed with kinyoun acid fast staining and ELISA as 7.86% and 12.35%, respectively. Karaman et al. 21 reported that the incidence of Microsporidium spp. in cancer patients was 10.9%. Compared to the results of these studies, the prevalence of C. parvum and Microsporidium spp. is lower in our study. This difference may be related to the study group, difference and sensitivity of the method used.
Studies that investigated the risk factors that may affect the prevalence of intestinal protozoa in cancer patients have reported different results depending on the study group and region. Jeske et al. 5 reported that there was no association between the prevalence of parasitic infections and the type of cancer, but the prevalence was high among those with pets. Rasti et al. 9 and Mohammadi-Ghalehbin et al. 1 did not find a relationship between age, educational level and prevalence of parasitic infections, but Rasti et al. 9 and Sanad et al. 19 found that the frequency of parasitic infection was higher in men than in women. Durak et al. 20 reported that in cancer patients with anal itching and crowded number of individuals sharing the same home, the prevalence of parasitic infections was higher. In our study, there was no statistically significant difference in the distribution of parasitic infections according to patients' demographics, illness stories, personal hygiene habits, clinical status, and complaints.
It is important to determine the frequency of parasitic diseases, parasite types and risk factors that may affect the follow-up and treatment process and the quality of life of the immunocompromised patients, such as cancer patients. We think that this area needs more research, which will help clinicians and create new approaches for patients' treatment and follow-up.