Thyroid dysfunction following radiotherapy for head and neck cancer.
OBJECTIVE
To determine the frequency of hypothyroidism (both subclinical and clinical) following external beam radiotherapy to the whole of the thyroid gland in the treatment of squamous cell cancers of the head and neck.


METHODS
One hundred and four patients who had completed radiotherapy 30 days to 5 years earlier (84 patients) or who were scheduled for radiotherapy (20 patients) had a single measurement of serum-free thyroxine and thyroid stimulating hormone levels between August 1991 and May 1992.


RESULTS
None of the 20 patients assessed prior to treatment showed thyroid dysfunction. Twenty of 84 (23.8%) previously treated patients had subclinical (9.5%) or clinical (14.3%) hypothyroidism. By 5 years, up to 40% of patients may become hypothyroid. Thyroid underactivity was significantly more common in patients having both laryngectomy (including hemi-thyroidectomy) and radiotherapy compared to radiotherapy alone (p < 0.001). Hypothyroidism had not been suspected clinically in any patient tested.


CONCLUSIONS
In view of the frequency and potential morbidity of this complication, thyroid function testing should become a routine part of posttreatment follow-up for these patients.
Department of Radiation Oncology, Westmead Hospital, N.S.W., Australia.
S L
SL
Turner
K W
KW
Tiver
S C
SC
Boyages
D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology*; D011878:Radiotherapy / Q000009:adverse effects*; D013961:Thyroid Gland / Q000528:radiation effects*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors
D013972:Thyrotropin; D013974:Thyroxine