Exploratory analysis as a sequel to suspected increased rate of cancer in a small residential or workplace community.

A suspicion that the incidence of cancer is rising in a residential or workplace community is often a cause of alarm among members of that community. The seemingly excessive number of diagnoses encountered may he due to: (i) a known explanatory variable, such as ageing of the community members; (ii) random occurrence of an event which is rare under stable conditions; (iii) exposure to an undefined carcinogenic agent. An exploratory analysis is suggested in order to consider the support indicated by the data with respect to each of the two last possibilities while controlling the first. The analysis involves several procedures which differ with respect to the targeted temporal pattern of the diagnoses. These procedures are mainly based on the a priori probability that a diagnosis is made within the time interval observed between consecutive diagnoses. When the number of diagnoses is found to be excessively large, the temporal pattern of the diagnoses may indicate whether the event is likely to be an incidental occurrence or due to the effect of a carcinogen.