ANTHRANOID LAXATIVE ABUSE - A RISK FOR COLORECTAL-CANCER

Anthranoid-containing laxatives - aloe, cascara, frangula, and rheum - may play a role in colorectal cancer. This risk is particularly impor tant in view of the wide abuse of self administered laxatives for chro nic constipation. There are data on the genotoxic potential of anthran oids and there is evidence of a tumourigenic potential in rodents. A c ase report and clinical-epidemiological studies have evaluated the can cer risk in patients who have abused anthranoid laxatives over a long period. Pseudomelanosis coli is a reliable parameter of chronic laxati ve abuse (>9-12 months) and is specific for anthranoid drugs. In a ret rospective study of 3049 patients who underwent diagnostic colorectal endoscopy the incidence of pseudomelanosis coli was 3.13% in patients without pathological changes. In those with colorectal adenomas, the i ncidence increased to 8.64% (p<0.01), and in those with colorectal car cinomas it was 3.29%. This lower rate was probably caused by incomplet e documentation of pseudomelanosis coli in those with carcinoma. In a prospective study of 1095 patients, the incidence of pseudomelanosis c oli was 6-9% for patients with no abnormality seen on endoscopy, 9.8% (p=0.068) for patients with adenomas, and 18.6% for patients with colo rectal carcinomas. From these data a relative risk of 3.04 (1.18, 4.90 ; 95% confidence interval) can be calculated for colorectal cancer as a result of anthranoid laxative abuse.