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Survivors of childhood cancer more prone to autoimmune diseases

Some autoimmune diseases 16 times more likely to occur after cancer, risk can last decades

Louise Prime

Wednesday, 11 November 2015

Survivors of childhood cancer are more likely than people who haven’t had cancer to suffer certain autoimmune diseases, according to research* published online today in the Annals of the Rheumatic Diseases. What is more, this excess risk can persist for up to 30 years for most conditions, and up to 50 years for a few of them. Authors of the study urge doctors to pay attention to the long-term health and quality of life of those surviving cancer in childhood, as well as to survival per se.

More children than ever now survive cancer – the current five-year survival rate is 80% – but those who survive seem to be more prone than their peers who haven’t suffered cancer to several health problems in adult life. Researchers in Sweden and Denmark designed a study to assess in more detail the impact of a history of cancer on their risk of various autoimmune conditions.

They used data from cancer registries in Denmark, Iceland and Sweden, covering the 1940s to 2008, to identify people who had had cancer as a child. Using hospital records, they compared rates of various autoimmune conditions among more than 20,000 adults who had suffered cancer before the age of 20 and survived for at least a year, with rates among almost 126,000 people who hadn’t had cancer, matched for age, sex and country of birth. They then calculated standardised hospitalisation rate ratios (SHRRs) and absolute excess risks (AERs).

For all autoimmune diseases combined, childhood cancer survivors had a significantly increased SHRR of 1.4, equivalent to an AER of 67 per 100,000 person-years. But the level of excess risk associated with childhood cancer varied hugely for individual diseases: the SHRRs were significantly increased for autoimmune haemolytic anaemia (16.3), Addison’s disease (13.9), polyarteritis nodosa (5.8), chronic rheumatic heart disease (4.5), localised scleroderma (3.6), idiopathic thrombocytopenic purpura (3.4), Hashimoto’s thyroiditis (3.1), pernicious anaemia (2.7), sarcoidosis (2.2), Sjögren’s syndrome (2.0) and insulin-dependent diabetes mellitus (1.6). The researchers said their figures were probably an underestimate, as they used hospital inpatient data, potentially missing those diagnoses made in general practice.

The type of cancer that someone had suffered as a child also affected the level of excess risk: the SHRRs for any autoimmune disease were significantly increased after leukaemia (1.6), Hodgkin’s lymphoma (1.6), renal tumours (1.6) and central nervous system neoplasms (1.4).

The excess risk was at its peak five years after a cancer diagnosis – perhaps, suggested the authors, because patients were monitored especially closely – and remained for up to 30 years for most conditions. However, it persisted for up to 50 years for Addison’s disease, chronic rheumatic heart disease and insulin-dependent diabetes mellitus.

The study authors suggested several possible explanations for the association, including that “persistent immune abnormalities after treatment with chemotherapy predispose to the development of autoantibodies, which are central to the pathogenesis of many autoimmune diseases”; that the cancer itself, and the immunosuppressive treatment for it, and resulting infections, could alter the immune system as a whole and also result in immunologically different antigens, leading to the production of autoantibodies; or that radiotherapy could help explain the development of autoimmunity.

They concluded: “Cure is no longer a sufficient goal in childhood cancer care. As the vast majority of these patients survive, attention must be paid to their long-term quality of life and health challenges.”

* Holmqvist AS, Olsen JH, Mellemkjaer L, et al. Autoimmune diseases in adult life after childhood cancer in Scandinavia (ALiCCS). doi 10.1136/annrheumdis-2015-207659

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