COVERT CANCER IN COLORECTAL POLYPS - SIZE MATTERS!

Aims To demonstrate the risk of covert cancer in colorectal polyps based on their size in one of the largest series of polyps to date

Tab. 1

Size	Proportion (%)	Location (%) R.colon: L. colon	Morphology(%) Pedunculated: Non-pedunculated
≤ 5mm (N=10775)	67.74	50:50	4:96	0
6-10 mm (N=2375)	14.87	30:70	32:68	0.17
11-19 mm (N=1759)	11.27	31:69	47:53	1.1
≥ 20 mm (N=1007)	6.12	24:76	14:86	7.7

Methods Outcomes of patients who had polyps on screening colonoscopy were analysed. Data was prospectively collected on an online endoscopy and pathology reporting system. A chart review was then carried out using multinomial logistic regression.

Results A total of 15906 polyps were removed at colonoscopy. Mean size was 7.3 mm.

Histopathological diagnosis of cancer was made in 104 polyps (0.65%). 94 polyp cancers (90.25%) were associated with non pedunculated morphology [OR 1.45 p=0.005].

No cancer was found in polyps < 5mm in size. Risk of cancer increased with polyp size as depicted in [Table 1]. Risk of developing cancer in polyps >20mm was significantly higher than in smaller polyps [OR 6.57 p< 0.001].

89 cancers were found in the left colon and rectum compared with 15 cancers in the right colon. [OR 1.98 p=0.007].

Conclusions The prevalence of covert cancer in colorectal lesions < 5mm is negligible and that of polyps 6-10 mm is very low (0.17%). All these cancers were in non-pedunculated polyps in left colon.This means that the ‘resect and discard’ strategy could be extended to 6-10 mm polyps in right colon and potentially to pedunculated polyps in left colon.

Cancer risk, however, increased almost 7 fold in polyps ≥2cm. This calls for careful resection (preferably en-bloc) and retrieval of these polyps to obtain all prognostic information.