Background Studies that have investigated the epidemiological relationship between thalassaemia and cancers are scarce. Therefore, we conducted a longitudinal nationwide cohort study to determine whether patients with thalassaemia are at an increased risk of cancer.

Methods We investigated the incidence and risk of cancer in 2655 patients diagnosed with thalassaemia between 1998 and 2010 by using data from the Taiwan Longitudinal Health Insurance Database. The comparison cohort comprised 10 620 people from the general population without thalassaemia. The follow-up period extended from the diagnostic date for thalassaemia to the date of a cancer diagnosis, censoring or 31 December 2011. We used Cox proportional hazard regression models to analyse the risks of cancer.

Results The incidences of cancer were 3.96 and 2.60/1000 person-years for the thalassaemia and comparison cohorts, respectively. The overall incidence of cancer was 52% higher in the thalassaemia cohort than in the comparison cohort, with an adjusted HR (aHR) of 1.54 (95% CI 1.15 to 2.07). Patients with thalassaemia had a considerably higher risk of haematological malignancy (aHR=5.32, 95% CI 2.18 to 13.0) and abdominal cancer (aHR=1.96, 95% CI 1.22 to 3.15) than did the comparison cohort. Furthermore, patients with thalassaemia with transfusion exhibited a 9.31-fold risk for developing haematological malignancy and a 9.12-fold risk for developing abdominal cancer compared with those who did not receive transfusion.

Conclusions This nationwide retrospective cohort study indicates that patients with thalassaemia carried substantial risks of haematological malignancy and abdominal cancer compared with those of the general population.