Effect of rehydration on guaiac-based faecal occult blood testing in colorectal cancer screening

A novel hypothesis on the sensitivity of the fecal occult blood test: Results of a joint analysis of 3 randomized controlled trials

BACKGROUND

Estimates of the fecal occult blood test (FOBT) (Hemoccult II) sensitivity differed widely between screening trials and led to divergent conclusions on the effects of FOBT screening. We used microsimulation modeling to estimate a preclinical colorectal cancer (CRC) duration and sensitivity for unrehydrated FOBT from the data of 3 randomized controlled trials of Minnesota, Nottingham, and Funen. In addition to 2 usual hypotheses on the sensitivity of FOBT, we tested a novel hypothesis where sensitivity is linked to the stage of clinical diagnosis in the situation without screening.

METHODS

We used the MISCAN-Colon microsimulation model to estimate sensitivity and duration, accounting for differences between the trials in demography, background incidence, and trial design. We tested 3 hypotheses for FOBT sensitivity: sensitivity is the same for all preclinical CRC stages, sensitivity increases with each stage, and sensitivity is higher for the stage in which the cancer would have been diagnosed in the absence of screening than for earlier stages. Goodness-of-fit was evaluated by comparing expected and observed rates of screen-detected and interval CRC.

RESULTS

The hypothesis with a higher sensitivity in the stage of clinical diagnosis gave the best fit. Under this hypothesis, sensitivity of FOBT was 51% in the stage of clinical diagnosis and 19% in earlier stages. The average duration of preclinical CRC was estimated at 6.7 years.

CONCLUSIONS

Our analysis corroborated a long duration of preclinical CRC, with FOBT most sensitive in the stage of clinical diagnosis.

Time trends in cancer incidence and mortality in central Italy

Time trends in cancer incidence and mortality represent an essential tool for monitoring the changes in population lifestyle and in the environmental risks and the effectiveness of the health system on cancer control in a specific area. During 1985-1997 82 506 malignant tumours were diagnosed in the Tuscany Cancer Registry, central Italy (about 1 200 000 inhabitants) and 54 979 cancer deaths registered in the period 1985-1999 by the Regional Mortality Registry were analysed. A statistically significant decrease in incidence was evidenced for stomach and gallbladder in both sexes, and for oesophagus, larynx and lung among males. Significant increases were documented for melanomas of the skin, kidney and non-Hodgkin's lymphoma in both sexes for colon, prostate and Kaposi's sarcoma among males and for breast, thyroid and multiple myeloma among females. Mortality decreased significantly for stomach and thyroid in both sexes and for oral cavity and pharynx, oesophagus, rectum, larynx, lung, bone, prostate, testis and Hodgkin's disease among males and colon, gallbladder and breast among females. Mortality increased for soft tissue, brain and multiple myeloma. In conclusion, most of these data can be explained as the effect of the modifications that occurred in smoking habits between the sexes and as the consequence of the primary and secondary prevention activities that are ongoing in the area.

Stool screening for colorectal cancer: evolution from occult blood to molecular markers

BACKGROUND

Colorectal cancer is the second leading cause of malignant death, and better preventive strategies are needed. Participation rates for colorectal cancer screening remain low due, in part, to perceived discomfort, potential harm, and high costs with available tools.

METHODS

Stool testing, unlike other conventional screening approaches, is noninvasive and requires no cathartic preparation. However, widely used fecal blood tests yield frequent false-negative and false-positive results that lower screening effectiveness and raise program costs. There is a compelling biological rationale to target DNA alterations exfoliated from neoplasms into stool, and multiple DNA markers would need to be assayed because of the genetic heterogeneity of colorectal neoplasia. Early clinical studies with this multi-target DNA-based stool assay approach suggest high sensitivity for both colorectal cancer and premalignant adenomatous polyps while maintaining high specificity.

CONCLUSIONS

This apparently accurate and user-friendly new approach holds promise to improve the effectiveness, efficiency, and appeal of colorectal cancer screening. Large-scale clinical studies are clearly warranted to corroborate the early results.