Cancer risk in patients with primary immune thrombocytopenia – A Swedish nationwide register study

• Published in: Cancer epidemiology 2020-12, Vol.69, p.101806-101806, Article 101806
• Main Authors: Ekstrand, Charlotta, Bahmanyar, Shahram, Cherif, Honar, Kieler, Helle, Linder, Marie
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age; Aged; Aged, 80 and over; Algorithms; Autoimmune diseases; Blood cancer; Cancer; Cohort Studies; Comorbidity; Confidence intervals; Diagnosis; Education; Epidemiology; Female; Gastric cancer; Health risks; Hematologic neoplasms; Hematology; Humans; Idiopathic thrombocytopenic purpura; Immunomodulation; Immunosuppressive agents; Intestine; Leukemia; Liver; Liver cancer; Liver neoplasms; Male; Medicin och hälsovetenskap; Melanoma; Middle Aged; Morphology; Nationwide; Patients; Population; Population studies; Primary immune thrombocytopenia; Purpura, Thrombocytopenic, Idiopathic - complications; Registries; Risk; Socioeconomic factors; Solid tumors; Splenectomy; Sweden; Sweden - epidemiology; Thrombocytopenia; Thrombopoietin; Tumors; Womens health; Young Adult
• ISSN: 1877-7821; 1877-783X; 1877-783X
• DOI: 10.1016/j.canep.2020.101806

•We studied all (N = 6,740) patients in Sweden with primary ITP 1998–2015.•Primary ITP patients have higher overall risk of cancer than the general population.•An increased risk of liver cancer was seen up to 9 years after ITP diagnosis.•Risk of skin cancer (all morphologies) was increased 10–20 years after diagnosis in patients with ITP.•Treating hematologists need to have a high index of suspicion for cancer. Immune thrombocytopenia (ITP) is an autoimmune disease treated with immunosuppressive agents, thrombopoietin receptor agonists, immunomodulation drugs and/or splenectomy. Patients with ITP have been found to have increased risk ofhematological malignancies. Studies investigating stomach/liver cancer are contradictory and the risk of developing other solid tumors is largely unknown. We aimed at estimating risk of overall and organ-specific cancers in patients with primary ITP. The study population was Swedish patients with at least one ITP diagnosis recorded in the National Patient Register and a 1:10 matched comparison cohort from the population. The study period covers 1997−2016. The Cancer Register and the Cause of Death Register provided data on malignancies and deaths, respectively. Primary ITP was identified using an established algorithm. We used time-split Cox models to estimate hazard ratios (HRs) with 95 % confidence intervals (CIs), adjusted for age, sex, index-year, county, income, education, Charlson score and number of in- and outpatient contacts. In total 66,134 individuals were included in the study. Patients with ITP had higher risk of gastro-intestinal, skin (all morphologies), lymphoid and hematological cancers. Adjusted HR (95 % CI) for cancer was 1.37 (1.27–1.48), with highest risk during the first year, but with increased risk remaining for up to 20 years for men. For women, the overall risk was increased during the first year, HR (95 % CI) 2.00 (1.55–2.60). A significantly increased liver cancer risk was seen up to 9 years after diagnosis. Patients with primary ITP have higher risk of cancer than the population. The observed increased risk does not seem to be solely due to surveillance bias, but might be associated with ITP or its treatments. Treating hematologists need to have high index of suspicion for cancer.