Despite uncertain benefits and harms, screening computed tomography (CT) is being marketed to consumers in the U.S. One plausible harm is the detection and treatment of renal carcinoma cases that otherwise would have remained clinically silent during the patient's lifetime.
After estimating the prevalence of preclinical renal carcinoma using meta-analysis of five series of asymptomatic, middle-aged Americans who received CT screening, the authors divided the prevalence by U.S. incidence rates of clinical renal carcinoma among persons of similar age. This calculation would estimate the mean duration of the detectable preclinical period (the “sojourn time”) of renal carcinoma if the incidence of preclinical and clinical renal carcinoma were equivalent.
The 5 series included 16,174 screenees (mean age range, 58–64 years; 61% male). The prevalence of asymptomatic renal carcinoma ranged from 0.11% to 0.76%; the pooled prevalence was 0.21% (95% confidence interval, 0.14–0.28%). The estimated mean sojourn time for renal carcinoma was between 3.7 years and 5.8 years among middle-aged Americans.
Because most renal carcinomas grow slowly during the preclinical period, the authors' estimated mean sojourn time did not seem unduly long. Therefore, the incidence rate of clinical renal carcinoma most likely is a reasonable surrogate for the incidence rate of preclinical renal carcinoma, implying that most renal carcinomas detected by CT screening among middle-aged Americans are likely to progress to clinical diagnosis. Cancer 2004;100:986–90. © 2004 American Cancer Society.