W einstock and Reynes 1 present intriguing data from the Surveil- lance, Epidemiology and End Results (SEER) program about the prognosis of patients in the United States with newly diagnosed mycosis fungoides (MF). They report improved overall and relative survival over a registration period of 20 years. Improved survival was evident when recent cohorts of patients were compared with historical controls (e.g., their 1983-1992 vs. 1973-1982) and was statistically significant when date of diagnosis was considered a continuous variable (P Ο 0.0001). They suggest that this was not likely because of any improvements in therapy. Rather, it may have been due to earlier diagnosis, a systematic change in the case mix, a change in the biology of the disease, or the inclusion of more benign disorders in the diagnosis. The latter two suggestions are possible but speculative. In an earlier report of SEER data, 2 the pathology was reviewed, and through 1984 MF was confirmed in 98% of cases. Was the pathology also reviewed for cases registered during 1985-1992?
If improved overall survival were due to earlier diagnosis, two things might happen. First, the age at diagnosis might decline within some or all stage groupings during the study period. Second, patients might migrate into earlier stage groupings, being given a diagnosis prior to their developing detectable widespread skin, lymph node, blood, or visceral involvement. In the latter effect, we do not have in focus any impact that a different stage assignment would have on overall survival for those stage groupings. Instead, we are interested in changes in the proportions of patients assigned to all stage groupings. The SEER reports note that the median age of all registered cases declined slightly over the years (from 64 years to 62 years) 1-2 and that the rate of incidence of Se Β΄zary syndrome hardly changed at all (from 5% to 4%). 1-2 Unfortunately, staging information is not available for the 95-96% of patients without Se Β΄zary syndrome. Overall, then, the information is insufficient to assess whether earlier diagnosis is occurring and whether there is a lead-time bias in the calculation of overall survival.
In response to the most recent report, 1 we analyzed a SEERindependent data set. During 1980 -1997, there were 410 patients with a new diagnosis of MF who were referred to Hamilton, where they received pathologic confirmation and, subsequently, active follow-up. This is not a population-based registry, but Hamilton is a clinical unit that accepts referrals from one-half of Canada. Population-based registries like SEER should provide more accurate statistics about rates of incidence. However, we estimate that a simple majority of patients in our apparent geographic area are referred to Hamilton.