In a study of the incidence of cancer in a cohort of adolescent idiopathic scoliosis (AIS) patients treated 25 years previously, investigators have found that patients treated with bracing or surgery had an overall cancer rate of 4.3%. This is ﬁve times higher than that of an age-matched Danish population.
To conduct the retrospective study, Ane Simony (Center for Spine Surgery and Research, Lillebaelt Hospital, Middelfart, Denmark) and colleagues identified 215 consecutive AIS patients treated between 1983 and 1990 and requested them to return for clinical and radiographic examination. The incidence of cancer was determined through chart review and follow-up interviews. Using the original radiographic log ﬁle that included patient position, mAs, kV and the total number of X-rays taken, a radiation physicist calculated the total radiation dose during treatment and follow-up adjusted for body mass index (BMI) and sex. From the original cohort of 215 consecutive AIS patients, radiation information was available in 211 of the patients, and medical charts were available in 209 AIS patients.
Eighty three per cent (170 patients) participated in the follow-up study with questionnaires. The calculated mean total radiation exposure was 0.8–1.4 mSv per examination and 2.4–5.6 mSv/year. An average of 16 radiographs were taken during the treatment period. Nine patients developed cancer, mostly breast (three) and endometrial (four). The AIS patients had a relative risk of 4.8 (CI 2.3–5.8, p=0) for developing cancer compared to the normal Danish population.
“Repeated radiation exposure during adolescence, speciﬁcally to the breast and thyroid gland, has been previously reported to be associated with the development of cancers; however, the exact correlation between radiation dose in children and adolescents is poorly understood. Our ﬁndings reveal a higher incidence of endometrial and breast cancer in our AIS cohort compared to the age-matched population in Denmark. Although previous studies have shown an increased breast cancer and breast cancer death in patients exposed to radiation for spinal deformities, this is the ﬁrst study reporting the incidence of endometrial and breast cancer in a relatively healthy population of adolescent females after radiation exposure during the 1980s and 1990s. Looking at the total number of radiographic examinations, the patients who developed cancer had on average more…examinations than the cohort in general,” the authors explain.
Further, the study showed that patients who developed endometrial cancers had a low BMI (mean=16.4kg/m2; range 15.9–16.6kg/m2) at ﬁrst radiation exposure, and were described as skeletally immature. The patients diagnosed with breast cancer were older at the time of diagnosis, more mature at the ﬁrst radiation exposure and had a mean BMI of 20.4kg/m2 (range 18–22.4kg/m2). None of the 123 patients who developed cancer had suffered from any medical history of diseases requiring diagnostic computed tomography scans. None of the patients had experienced radiation exposure during their current or previous occupation. The rate of active smokers in the cohort was 11.8%, compared to 11–20% of smokers in the normal population in Scandinavia.
The investigators state that further AIS cohort studies, with a larger sample size, are needed to provide accurate cancer risk estimates associated with radiation exposure in patients with AIS. Further, they maintain that there is still room for improvement in the reduction of radiation exposure.
“Although the radiation exposure to the patients has been reduced during the last decade, surgically treated patients are still exposed to radiation during the surgical correction of the deformity. [A] study by Himmetoglu et al indicates that DNA damage may be present after standing radiographs even with newer equipment. Thus, even with reduced radiation exposure, strategies to further reduce radiation exposure should continue. A recent study by Ilharreborde et al including the new EOS technology suggests that even with a reduced radiation protocol, it is possible to perform examinations with an acceptable image quality,” they state.