Distribution of cancer and adenomatous polyps in the colorectum: study in an Iranian population

There is consensus that the majority of colorectal carcinomas (CRCs) arise from adenomatous polyps. Therefore, for management of colorectal cancer, diagnosis and endoscopic resection of adenomas is advised. If the same etiologic factors are operating for polyps and cancers their anatomical distributions should be the same. The present study was conducted to determine whether the distribution of adenomas is consistent with that of CRCs and for comparison with other studies, especially in Western populations.

We reviewed, retrospectively , endoscopically reported anatomic sites of all adenomatous polyps and CRCs which were histologically confirmed from Jan 1992 to Dec 2005 in Tabriz, the North-west of Iran. One hundred and forty-three CRC's and 180 adenomatous polyps (in 145 patients) were found. Patients with polyposis syndromes were excluded the analysis. Age and sex of patients, size and anatomic sites of polyps and cancers were studied.

The average ages of patients with adenomas and cancers were 46.3(SD 14.7) and 53.9(SD 13.3)years, with 55.5% and 62.2% in males, respectively. In both cancer and adenoma cases the most common presenting symptoms were rectal bleeding and bloody diarrhea ( 52.4% , 16.9% and 39.2% , 15.8% for cancers and adenomas, respectively) without any significant difference(0>05). The vast majority of adenomas (85%) and cancers (81.7%) were left sided (p>0.05). The propensity for polyps to be found in the descending colon was of borderline significance (p=0.07). The cecal segment uniquely demonstrated cancers(p=0.01) without any polyps.

A similar anatomic distribution pattern and left shift of colorectal adenomas and cancers in this Iranian population is compatible with most other Asian countries. However, because of the occurrence of the neoplasms in the right colon total colonoscopy should still be considered for screening purposes.