Q&A on diagnosis, screening and follow-up of colorectal neoplasia

The discovery and validation of colorectal cancer biomarkers

Colorectal cancer is currently the third most common malignancy in the world. Patients have excellent prognosis following surgical resection if their tumour is still localized at diagnosis. By contrast, once the tumour has started to metastasize, prognosis is much poorer. Accurate early detection can therefore significantly reduce the mortality from this disease. However, current tests either lack the required sensitivity and selectivity or are costly and invasive. Improved biomarkers, or panels of biomarkers, are therefore urgently required. We have addressed current screening strategies and potential protein biomarkers that have been proposed. The role of both discovery and hypothesis-driven proteomics approaches for biomarker discovery and validation is discussed. Using such approaches we show how multiple reaction monitoring (MRM) can be successfully developed and used for quantitative multiplexed analysis of potential faecal biomarkers.

TNM staging system of colorectal carcinoma: a critical appraisal of challenging issues

CONTEXT

Colorectal cancer is the leading cause of morbidity and death among gastrointestinal tumors and ranks fourth after lung, breast, and ovarian cancers. Despite a continuous refinement of the T (tumor), N (node), and M (metastasis) staging system to express disease extent and define prognosis, and eventually to guide treatment, the outcome of patients with colorectal cancer may vary considerably even within the same tumor stage. Therefore, the need for new factors, either morphologic or molecular, that could more precisely stratify patients into different risk categories is clearly warranted.

OBJECTIVES

To present the state of the art with regard to the colorectal cancer staging system and to discuss confusing and/or challenging issues, including the assessment of peritoneal membrane involvement, vascular invasion, tumor deposits, and pathologic tumor response to neoadjuvant chemoradiotherapy.

DATA SOURCES

Literature review of relevant articles indexed in PubMed (US National Library of Medicine) and primary material from the authors' institutions.

CONCLUSIONS

Two emerging needs exist for the TNM system, namely, further stratification of patients with the same tumor stage and incorporation of nonanatomic factors, the latter including molecular and treatment factors. The identification and classification of morphologic features encountered in the pathologic examination of colorectal cancer specimens may be difficult and a source of subjective variability. Enhanced pathologic analysis, agreed-upon standard protocols, and standardization should improve the completeness and accuracy of pathology reports.

Detection of colonic polyps according to insertion/withdrawal phases of colonoscopy

BACKGROUND AND AIMS

Issues on colonoscopy quality are crucial to reduce the advanced neoplasia miss rate of colonoscopy. Recently, a >6-min withdrawal time has been recommended. However, the relative prevalence of polyp detected during insertion and withdrawal phases of colonoscopy is unknown. Therefore, we designed this prospective, endoscopic study.

MATERIALS AND METHODS

Three hundred and sixty-eight patients with 396 adenomas were selected from a consecutive colonoscopic series of 1,205 cases. Detection rates of adenomas, advanced adenomas, and cancer according to withdrawal and insertion phases of colonoscopy, also subgrouping polyps for size and location, were compared.

RESULTS

Thirty-two (74%) advanced adenomas and 21 (95%) cancers were detected during the insertion, being only 11 (26%) and one (5%) identified during withdrawal, respectively. This was mainly due to a higher detection of >10 mm polyps during insertion than during withdrawal (75% versus 25%).

CONCLUSIONS

Most advanced neoplasia are detected during the insertion. Although withdrawal time has been shown to be important, the scope insertion phase related to polyp detection should be specifically addressed.