HOW ACCURATE IS SIZE MEASUREMENT OF PANCREAS CANCER MASSES BY COMPUTED AXIAL-TOMOGRAPHY (CT) SCANNING

With the advent of preoperative radiotherapy for pancreas cancers, the ir measurement by imaging is rendered more important, so that outcome data from various treatment programs may be compared. Two radiologists have examined tumor size measurements from 29 patients by CT scans ob tained within a week of measurement in the Pathology Department after resection. The radiologists assessed these scans independently from on e another and blinded from the pathologic measurement. The largest dia meter of their readings was compared to the largest diameter of the tu mor measured by the Pathology technician. The correlation between radi ologists (P < 3 x 10(-8) was excellent, Correlation between the averag e of the two radiologic estimates of greatest tumor diameter and actua l tissue measurement is excellent for tumors (n = 21) greater than 2 a nd less than 5 cm in diameter (P < 0.03), but of four specimens measur ed in the Pathology laboratory as less than 2 cm, all were measured by the radiologists as being at least 1.5 cm larger. Twenty of the 29 ca ncers (69%) were measured by two radiologists to be within 1 cm of the actual diameter. The nine specimens producing the greatest errors wer e two with diffuse mucinous tumors throughout the gland (radiologists undercalled by 2.5 cm), one 7 cm mass with a cystic center composed of necrotic cells (overcalled by 2.5 em, perhaps because of deformity or release of fluid in Pathology), four small masses (1, 1.5, 1.5, and 1 .5 cm in diameter), smaller than the normal diameter of the pancreas h ead, and two tumors with inexplicably inaccurate size estimates. Of th e nine cases with errors of at least 2 cm by at least one radiologist, six were measured as larger than actual. Current techniques are reaso nably accurate for tumors >2 cm in diameter. Spiral and thin-section C T scanning with bolus enhancement will probably further improve the ra diologist's estimate of pancreas tumor size, particularly of T1 cancer s.