Low-dose ionizing radiation from cardiac imaging may promote cancer
Exposure to low-dose ionizing radiation (LDIR) from cardiac procedures contributes to an increased risk of developing malignancies, with a possible dose–response relationship between exposure level and cancer risk, as reported in a recent study.
“The potential increase in cancer-related morbidity and mortality associated with exposure to radiation from cardiac imaging should inform judicious use of such procedures over the patients’ lifespan,” the investigators said.
“Physicians ordering and performing cardiac imaging should ensure that exposure is ‘as low as reasonably achievable’ with consideration to alternative non-LDIR procedures when possible without sacrificing quality of care,” they added.
The case–control study involved adult congenital heart disease (CHD) patients: 602 cancer patients (median age 55.4 years) and 2,405 noncancer controls. Compared with controls, cancer patients had undergone more LDIR-related cardiac procedures such as cardiac catheterizations, chest CT and nuclear imaging (p<0.0001 for all).
The cumulative incidence of developing cancer over the course of adulthood up to 64 years of age was 15.3 percent (95 percent CI, 14.2–16.5). Meanwhile, the cumulative incidence of developing cancer during the 15-year follow-up was 8.5 percent (7.8–9.1) in the group with high LDIR exposure (≥6 LDIR procedures) vs 3.3 percent (3.0–3.6) in the group with low LDIR exposure (≤1 LDIR procedure; p<0.0001).
Cumulative LDIR exposure emerged as an independent risk factor for cancer development. The odds of developing cancer increased by 1.08 times per LDIR procedure, by 1.10 times per 10 mSv (effective dose estimates) and by 2.37 times with high LDIR exposure. [Circulation 2018;137:1334-1345]
The observed associations persisted and remained very similar through numerous sensitivity analyses.
Noting that the current study is the first to analyse and document the association between LDIR-related cardiac procedures and incident cancer in the population of adults with CHD, the authors highlighted the need to confirm their findings in children and using prospective studies to reinforce policy recommendations for radiation surveillance in CHD patients where no regulation currently exists.
In an accompanying editorial, Drs Ninian Lang from the Queen Elizabeth University Hospital Glasgow and Niki Walker from the Golden Jubilee National Hospital in Glasgow agreed with the authors that prospective assessment is important and should include consideration of patient age at the time of LDIR. [Circulation 2018;137:1334-1345]
“However, we would argue that there should be no reason to delay the development of a ’patient passport’ that patients with CHD would carry with them that could be replicated in hospital electronic medical records,” wrote Lang and Walker.
Ideally, the said passport is electronic and portable. It should include an overview of the patient’s CHD history, including diagnoses, anatomy and interventions, while emphasizing the cumulative lifetime LDIR exposure.
Lang and Walker pointed out that an accurate and continuously updated list of LDIR procedures “would act as an extra ‘stop and think’ checkpoint for both the healthcare team and the patient,” and, in turn, avoid the ordering of otherwise unnecessary LDIR imaging procedures.
“It is likely that exposure to ionizing radiation will be an inevitable cornerstone in the assessment, intervention and follow-up of patients with CHD for the foreseeable future, despite significant advances in alternative techniques,” they continued.
In light of the impressive survivorship in CHD, he present study adds further weight to the use of the lowest radiation dose that is reasonable, without compromising care, and should provide the impetus for robust, routine and longitudinal collection of cumulative radiation exposure in all patients with CHD around the world, Lang and Walker said.