Risk of cancer onset in sub-Saharan Africans affected with chronic gastrointestinal parasitic diseases.

Gastrointestinal Schistosomiasis and Amebiasis are uncommon in the western world, while such
infections are frequent in the African community. In addition to the problems associated with the clinical
symptoms of these parasitic infections, it is important to stress the increase in cancer of the Gastro-Intestinal
(GI) tract. In this study we evaluate the prevalence of cancer in patients affected by chronic inflammatory
diseases caused by the above named parasites. In three years, from January 2000 to December 2003, we
observed a total of 1199 subject. Of these, 950 presented with complaints of diarrhoea, vomiting, abdominal
pain, melena, hematemesis, rectal discharges and alteration of bowel habits. A total of 818 patients were
evaluated in Uganda (Mulago and Arua hospitals) and 381 at Luisa Guidotti Hospital in Zimbabwe. An
exhaustive clinical history was collected for each patient and then physical and laboratory examinations
were performed. The clinical files of all patients previously admitted to the respective hospitals were obtained
and the information taken from these files was then integrated with our clinical findings. Subjects who were
found free of gastro-intestinal disease after examinations and did not have a clinical history of infective GI
disease but presented with other pathologies, were regarded as control group. The control group was
composed of 249 subjects. The subjects who were positive on examination underwent further investigations.
The number of patients affected by schistosomiasis and amoebiasis were 221 and 224 respectivelly. The
number of patients who suffered from aspecific enterocolitis was 454, intestinal tuberculosis was present in
21 patients and we found 30 patients with esophageal candidiasis. Patients who had the above mentioned
GI diseases were then divided into 3 groups. First group was composed of patients who had a clinical history
of infective GI diseases and were re-admitted for similar symptoms, and on examination were positive for
the presence of the same infective GI diseases. Such patients were placed in the “Chronic group”. The second
group was formed of patients who had previously undergone treatment for infective GI diseases but on readmission
were found free of infective GI disease, and this group was described as the “Cured group”. They
had symptoms associated with other pathologies. Athird group, which we described as the “Acute group”
was composed of patients who did not have any previous case of GI infection and were admitted for the first
time. Such patients were found positive on examination for infective GI diseases. In the 950 patients, we
found a total of 45 tumors. The tumors were prevalent (42 tumours) in the chronic group. In 34 patients the
tumorwas in the colo-rectal region, in 3 patients in the stomach, in 4 patients in the oesophagus and 1 patient
had cancer in the small bowel. Our results show a strong association between the chronic infection of the GI
tract and the likelihood to develop tumours. However, it is not clear which biological mechanisms are
implicated in such transformations. They may depend on the chronic inflammation of the GI mucous which
permits the entrance of carcinogenic materials or on the effects of mutagenic products produced by the
parasites or both.