PURPOSE: Computed tomographic colonography (CTC) has generated considerable interest as a screening technique for colorectal cancer. One of the most important features of CTC, however, is its ability to detect extracolonic lesions. We have previously documented the frequency and nature of such lesions. The most common extracolonic early stage cancer detectable by CTC is renal cell carcinoma (RCC). We aim to evaluate the potential impact of detecting preclinical RCC on a CTC screening program.

METHODS: We developed a Markov model that simulates the natural history of preclinical RCC. We supposed that a hypothetical population of 100,000 subjects aged 60 years undergoes a single CTC screening procedure or dose not. We then compared the difference in life expectancy for preclinical RCC patients between the screening and non-screening strategy. The parameters of the model are based on our systematic literature reviews and SEER (the Surveillance, Epidemiology, and End Results program) database. Sensitivity analyses were performed by changing assumptions about biological variables (such as lead time) and clinical variables (such as age at screening).

RESULTS: In the base-case analysis, screening a population of 100,000 subjects aged 60 years by CTC saved 909.2 life years (between 3 and 4 days per person screened). The sensitivity analyses show the RCC-related life year gains are 842.9 and 836.5 respectively for the populations aged 55 and 65 years. The outcome of the analysis varied widely in response to changes in the proportion of early stage RCC detected by CTC and the transition probability of early stage RCC developing to advanced RCC. Other variables had a much smaller effect on life expectancy.

CONCLUSIONS: Detection of RCC as a result of CTC screening is likely to bring improvements in life expectancy that, while not adequate on their own to justify a screening program, should be included in the balance sheet of costs and benefits.