Carcinoma of the urinary bladder associated with schistosomiasis in Egypt: the possible causal relationship

Carcinoma of the urinary bladder is the most common malignancy in Egyptians. At the National Cancer Institute in Cairo, it accounts for 27.6% of all cancers--38.5% of cancers in the male and 11.3% in the female. This very high frequency is attributed to underlying schistosomiasis. The infection can lead to malignancy through local tissue damage, mechanical irritation, bilharzial toxins or through secondary bacterial infection. Bacterial products include nitrate reductase capable of synthesizing nitrosoamines and beta glucuronidase enzymes, active at pH 7. Through liver involvement and dysfunction, tryptophan metabolism is disturbed, with the excretion of carcinogenic metabolites. Vitamin A deficiency is responsible for the squamous metaplasia and the high frequency of squamous cell carcinoma observed in the bladder. The characteristic clinico-pathological features of cancer of the urinary bladder are outlined, mainly the occurrence at a young age, the male predominance, especially farmers, and the high association with schistosomiasis. The tumors are often first seen in an advanced stage, arising from the posterior bladder wall and vault. The trigone is only affected in 8.5% of the cases. Histologically, squamous cell carcinomas of low grade are the most frequent cell type. Lymph node involvement is low in spite of the advanced stage of the tumor. Therefore, the results of radical surgery are encouraging. The results of a special study correlating the above parameters with the intensity of ova deposition are presented. Patients with heavy infection at a slightly earlier age but other tumor parameters the same are similar to those of egg-negative cases. This study indicates that other factors also play a role in the induction of tumors that are enhanced by the schistosomal infection. In Fayoum Province, schistosomiasis is decreasing while bladder cancer is increasing. Urine cytology as a screening tool is effective in detecting early bladder cancer. Studies are now in progress to detect tumor associated antigens in sera and urine of patients.