Incidence of lymphohaematopoietic malignancies in a petrochemical industrycohort: 1983-94 follow up

Objectives-In response to a previous finding of increased mortality from ly mphohaematopoietic (LH) malignancies, this study examines incidence of LH m alignancy in a petrochemical industry cohort. Emphasis is on chronic lympho cytic leukaemia (CLL) and on comparisons by period of first employment. Method-The study cohort consists of 8942 employees who were active in the p eriod 1970-92 and alive on 31 December 1982. Record linkage with the Louisi ana tumour registry (LTR) provided information on cancer for cases occurrin g between 1983 and 1994. Standardised incidence ratios (SIR), with the sout h Louisiana population as a comparison, were computed for all cancers, all LH malignancies and specific LH subtypes. Analyses were conducted for sex a nd race categories, and by period of first employment, job type, duration o f employment, and latency. Results-672 Cases of cancer were identified, including 59 LH malignancies; Women (n=1169) had an overall cancer SIR below unity and four LH malignanci es versus 2.28 expected. Among the 7773 men, those first employed before 19 50 had no overall cancer excess, a significant 1.4-fold increase in overall LH malignancies (43 observed versus 30.78 expected), and four CLL cases ve rsus 3.27 expected. Findings for men first employed after 1950 are based on fewer cases, but there was no indication of excesses of overall cancer or LH malignancy. Numbers were too small in the group first employed after 195 0 for meaningful analysis of LH malignancy subtypes such as CLL (one case). Conclusion-These findings do not suggest a continuing excess of CLL but do suggest a small increase in incidence of overall LH malignancy for workers first employed before 1950. This may reflect associations with earlier work place conditions, although work related patterns are mixed. Interpretation is Limited by the diverse group of diseases within LH malignancies, and the lack of control for non-work factors other than sex, age, race, and period of diagnosis. This study has a major advantage of more complete and reliab le cancer ascertainment compared with the mortality investigation, and show s the feasibility and benefits of using cancer registry incidence data in a n occupational cohort study.