Individuals with autism spectrum disorder (ASD) may be at higher risk of developing cancer early in life, but this risk seems largely related to the presence of co-occurring birth defects or intellectual disability, according to new findings.
Researchers found that people with ASD and birth defects had a twofold higher risk of cancer compared with those without ASD. For individuals with birth defects and intellectual disability, the risk for cancer was nearly five times greater.
But ASD alone, without these comorbidities, did not appear to confer an increased risk of cancer.
“Additional research on specific cancer types, perhaps through multinational efforts, should be considered to gain a better understanding of the burden of different cancer types among individuals with ASD and such comorbidities,” the authors, led by Qianwei Liu, MD, of the Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden, write.
The findings were published in Annals of Oncology.
There have been few studies of cancer risk among individuals with ASD. In those studies that have explored such an association, findings have been inconsistent, likely because of potential confounders or narrow definitions of autistic disorder.
To clarify whether a link exists, Liu and colleagues analyzed the overall risk of cancer and risk by cancer type among individuals with conditions that fell within the ASD spectrum, as well as by comorbidity status.
The researchers conducted a population-based cohort study using data from the Swedish Medical Birth Register, which covers 99% of all births in Sweden since 1973. The cohort included 2.3 million individuals born during 1987–2013 in Sweden with follow-up through 2016 (up to age 30) and used the Swedish National Patient Register to identify persons with ASD.
The cohort was divided into three groups: individuals who had been diagnosed with an ASD (n = 40,334), their siblings without ASD (n = 36,160), and individuals in the general population without ASD (n = almost 2.3 million).
A total of 205 cancer cases (0.51%) were identified in the ASD arm: 135 had been diagnosed with cancer before they had been diagnosed with ASD, and 70 had been diagnosed with cancer after they had been diagnosed with ASD. There were 7958 cancer cases (0.35%) among the control persons.
Overall, the investigators found a statistically significantly increased risk of any cancer among individuals with ASD (odds ratio [OR], 1.3) compared with those without ASD. However, this increased risk was primarily attributable to those with ASD and comorbid birth defects (OR, 2.1) or those with both birth defects and intellectual disability (OR, 4.8), not those with ASD who did not have birth defects or intellectual disability (OR, 1.0).
The increased risk for any cancer was higher for narrowly defined autistic disorder (OR, 1.7) compared with other types of ASD (OR, 1.2). The authors also found a small but not significant risk associated with ASD and intellectual disability alone (OR, 1.4).
In addition, a significant association between ASD and cancer was only observed for certain malignancies. These included cancers of the eye (n = 10; 4.8% of cancers among individuals with ASD), central nervous system cancers (n = 66; 31.9% of all cancers among individuals with ASD), and thyroid cancer (n = 9; 4.3% of all cancers among individuals with ASD).
The associations remained stable after adjusting for confounders that included sex, birth year, parental age, parental education, birth characteristics, and maternal smoking.
The authors note that because their study focused on cancer diagnoses up to age 30, “continued follow-up is needed to examine the risk of cancers diagnosed in later life among individuals with ASD, regardless of the presence of comorbidities, as the etiologies of cancers diagnosed in later life likely differ from those diagnosed in early life.”
The study was funded by the Swedish Cancer Society, the European Union’s Horizon 2020 research and innovation program “RECAP preterm,” the Karolinska Institutet, and the China Scholarship Council. The authors have disclosed no relevant financial relationships.
Ann Oncol 2022 Jul;33:713-719. Full text
Roxanne Nelson is a registered nurse and an award-winning medical writer who has written for many major news outlets and is a regular contributor to Medscape.