Increased incidence of parathyroid adenomas following X-ray treatment of benign diseases in the cervical spine in adult patients.
OBJECTIVE
To determine whether or not exposure to ionizing radiation as an adult increases the risk of developing parathyroid adenomas.


METHODS
A cohort of 27 415 patients had received X-ray treatment to palliate pain originating from arthrosis and spondylosis from 1950 to 1964. In a subcohort of 8144 patients the cervical spine was the target, or one of the targets for the treatment. With the technique used it could be assumed that, as a rule, the parathyroid glands had been included in the treated volume. Patients with parathyroid adenomas were obtained from the Swedish Cancer Register from 1958 to 1995. The standardized incidence ratio (SIR) was calculated.


RESULTS
The number of person-years at risk was 180 492 in the cohort exposed at the cervical spine, and 412 994 in the control cohort irradiated only at other sites. The calculated dose in the parathyroid region in the study cohort was about 1 Gy. The observed number of parathyroid adenomas in the study cohort was 22, and 24 in the control cohort. Expected numbers based on population data were 12.0 and 24.7, respectively, giving an SIR of 1.83 (95% CI 1.14-2.76) and 0.97 (CI 0.62-1.45), respectively. Mean age at exposure was 48.9 years (SD 10.2) and at diagnosis 71.5 years (SD 8.3). The time from exposure to diagnosis varied from 2 to 34 years (median 26 years). The excess relative risk was about 0.8 per Gy.


CONCLUSIONS
Exposure to ionizing radiation to the cervical spine in adult age seems to be associated with an increased risk of developing parathyroid adenomas.
Rasmuson
Torgny
T
Department of Oncology, Umeå University, Sweden. Torgny.Rasmuson@onkologi.umu.se
Damber
Lena
L
Johansson
Lennart
L
Johansson
Robert
R
Larsson
Lars-Gunnar
LG
D000236:Adenoma / Q000209:etiology*; D000328:Adult; D016022:Case-Control Studies; D002574:Cervical Vertebrae; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000209:etiology*; D010146:Pain / Q000532:radiotherapy; D010280:Parathyroid Glands / Q000528:radiation effects; D010282:Parathyroid Neoplasms / Q000209:etiology*; D011879:Radiotherapy Dosage; D012307:Risk Factors; D013122:Spinal Diseases / Q000532:radiotherapy*; D013128:Spinal Osteophytosis / Q000532:radiotherapy; D025241:Spondylarthritis / Q000532:radiotherapy