A TRIAL TO DISCRIMINATE SPONTANEOUS REGRESSION FROM NONREGRESSION CASES DURING MASS-SCREENING FOR NEUROBLASTOMA

We tried to discriminate between cases of spontaneous regression and n on-regression during mass screening for neuroblastoma, taking advantag e of differences in respect to the urinary homoranillic acid/vanillyl mandelic acid (HVA/VMA) ratio and the original tumor site among true p ositive, false negative and natural occurrence cases. After classifyin g them into a total of six groups depending on the two factors, ratio: < 1, 1-2 or greater-than-or-equal-to 2 and tumor site: adrenal or ext ra-adrenal in origin, we calculated the mathematical probability of a given true positive case being one of spontaneous regression. A tumor of extra-adrenal origin was likely to regress spontaneously, especiall y one with an HVA/VMA ratio < 1 or greater-than-or-equal-to 2 (82.2-10 0%). A tumor of adrenal origin with an HVA/VMA ratio < 1 seemed unlike ly to regress spontaneously (0-4%). The present method, employing simp le preoperative information, would be useful in future for the selecti on of true positive cases which should be observed without treatment.