Establishment of a method for measuring tumor size in the Apc^+/Min-FCCC mouse by colonoscopy

A60

The scientific potential of numerous unique animal models of carcinogenesis has not been fully realized due to our limited ability to monitor tumor growth in vivo. Establishment of a method for the accurate measurement of colon lesion size is needed to both characterize the dynamics of tumor growth and monitor responsiveness to therapeutic interventions. The goal of the present study was to develop an endoscopy-based protocol for the accurate estimation of tumor size in vivo from images obtained during colonoscopic examinations. This technology was established using a unique strain of Multiple Intestinal Neoplasia (Min) mice established at Fox Chase Cancer Center (Apc^+/Min-FCCC), which spontaneously develop multiple colorectal tumors. Anesthetized Apc^+/Min-FCCC mice received colonoscopic examinations, using a rigid endoscope. The endoscope (1.5 mm diameter) was inserted anally, and high-resolution images of 10 colon adenomas (from 8 animals) were captured using a CCD camera. Lesion size was estimated by comparing the dimensions of the tumor relative to a reference rod of known diameter using a novel geometric construction. The resulting areas were compared with estimates from magnetic resonance imaging (MRI) scans made the following day and validated at necropsy.A comparison of the cross-sectional area of each lesion as estimated via colonoscopy with that measured at necropsy yielded a correlation coefficient of 0.92. A similar correlation (ρ = 0.91) was obtained when tumor volume from MRI was compared with that calculated from lesion measurements at necropsy. Application of this technique to mouse models of colon carcinogenesis will provide unique insight into both the dynamics of tumor growth and the responsiveness of lesions to therapeutic intervention. (Supported by U54 CA105008 and CA06927 from the National Cancer Institute.)