THE ROGERS,WILL PHENOMENON - STAGE MIGRATION AND NEW DIAGNOSTIC-TECHNIQUES AS A SOURCE OF MISLEADING STATISTICS FOR SURVIVAL IN CANCER

A cohort of patients with lung cancer 1st treated in 1977 had higher 6 mo. survival rates for the total group and for subgroups in each of the 3 main TNM stages (tumor, nodes and metastases) than a cohort treated between 1953 and 1964 at the same institutions. The more recent cohort had undergone many new diagnostic imaging procedures. According to the old diagnostic data for both cohorts, the recent cohort had a prognostically favorable zero-time shift. By demonstrating metastases that had formerly been silent and unidentified, the new technological data resulted in a stage migration. Many patients who previously would have been classified in a good stage were assigned to a bad stage. Because the prognosis of those who migrated, although worse than that for other members of the good-stage group, was better than that for other members of the bad-stage group, survival rates rose in each group without any change in individual outcomes. When classified according to symptom stages that would be unaltered by changes in diagnostic techniques, the 2 cohorts had similar survival rates.