Dangerous Duplicates

The report contrasts the ascertainment of cases by the regional cancer registry with a specially designed search for records and pathology material which was then submitted to critical review irrespective of the original diagnosis. Boundary changes over the intervening years were accounted for and the results contrasted between time periods and with the cancer registry records. A large proportion of cancer registry cases were never subjected to histopathological diagnosis and comparisons between the new data and records are not easy to undertake. The study describes a probable true rise in the incidence of follicular non-Hodgkin's lymphoma in certain parts of Yorkshire over the last 20 years; there is less evidence of a similar change in Hodgkin's disease incidence over the same period of time. Knowledge of changing trends in lymphoma incidence, whether geographical or temporal, may provide important insights into the aetiology of these malignancies. These data are normally provided by cancer registrations. Some information on lymphoma incidence is available on an international basis (Waterhouse et al., 1982) and annual reviews of registrations for England and Wales are produced by the Office of Population Censuses and Surveys (OPCS, 1978-85). Mortality figures are also provided over longer periods but their value in relation to disease incidence is restricted due to the significant change in survival of lymphoma patients in recent years. Certain limitations are also attached to the use of standard incidence figures from lymphoma registration which necessitate caution in their interpretation. This is the result both of inaccuracy and lack of resolution of the data. Inaccuracy may occur at source due to difficulties in establishing a reliable pathological diagnosis (Bird et al., 1984). It can also be due to incorrect registration of cases; this will vary with time as registration procedures have become more efficient since cancer registries were first established 30 years ago. Very little is known about the past or present efficiency of cancer registration, or how accurately cancer registry figures reflect the true incidence of neoplastic diseases. Examination of the figures published by OPCS for the Yorkshire Health Region (OPCS, 1978) appear to suggest that there has been an approximate doubling in the registration rate of non Hodgkin's lymphoma between 1968 and 1980, while for Hodgkin's disease the rate has remained constant in males and doubled in females. These trends are also observed nationally with Hodgkin's disease incidence remaining constant while other malignant neoplasms of lymphoid and …