does RAI cause thyroid cancer? a study

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Surgery. 1986 Dec;100(6):1121-7. Related Articles, Links

Graves' disease and thyroid cancer.

Behar R, Arganini M, Wu TC, McCormick M, Straus FH 2nd, DeGroot LJ,

Kaplan EL.

The relationship between Graves' disease or its therapy and

carcinoma of the thyroid remains uncertain. We studied 20 patients

found to have thyroid cancer in glands previously treated for

Graves' disease between 1961 and 1986 at the University of Chicago

Medical Center. Sixteen (80%) occurred in women and four (20%)

occurred in men. The mean age at operation was 37 years (range, 19

to 69 years) and did not differ by sex. Fifteen of the 20 cancers

(75%) were papillary while five (25%) were follicular. Six

individuals (30%) had a history of external radiation to the head

and neck as an infant, child, or young adult. Two others had

received radioiodine (RAI) therapy for Graves' disease 1 and 19

years earlier. Patients were divided into three groups: group I:

four patients (20%) had a neck mass 4, 14, 20, and 41 years after

having had a subtotal thyroidectomy (STT) for Graves' disease; three

of four had a history of external irradiation therapy. These tumors

behaved aggressively, resulting in the death of two of the four

patients. group II: 11 patients (55%) had diffusely enlarge toxic

goiters without a nodule. A carcinoma was diagnosed intraoperatively

on frozen section in only two of these patients. The others received

STT. After recognition on permanent section, those carcinomas that

were 4 mm or greater in diameter received postoperative RAI. One

recurrence occurred and was treated successfully with further RAI.

group III: Five patients (25%) had Graves' disease and a palpable

thyroid nodule. None of them had had a prior thyroidectomy for

Graves' disease, as in group 1. Thyroid carcinoma was diagnosed in

all patients preoperatively or intraoperatively, and a total

thyroidectomy was performed. Each patient is alive and well with a

mean follow-up of 5 years. Between 1971 and 1981, 194 patients had

surgery for Graves' disease, and 10 (5.2%) were found to have an

associated carcinoma; six patients (3.1% of the total) did not have

a nodule or any other suspicion of malignancy before surgery. During

the same time, 303 patients received RAI therapy for Graves' disease

and one (0.3%) has subsequently developed thyroid carcinoma. Thyroid

cancer associated with Graves' disease is found more commonly in

surgically treated patients than in patients after RAI therapy. The

greatest risk factor in our patients was previous external radiation

to the head and neck. Such individuals should be treated with total

thyroid ablation rather than the usual STT, since they are at risk

of developing aggressive thyroid cancers if thyroid remnants are

left.