Radiation worsens thyroid cancer patient outcomes

Apr 19, 2009

Patients who've been exposed to radiation prior to developing thyroid cancer have more aggressive disease and worse clinical outcomes, according to new research from Mount Sinai Hospital in Toronto.

The findings are particularly worrisome for individuals who were treated with radiation of the head and neck for acne, who have had extensive diagnostic imaging of the head and neck, who received radiation therapy for another body site, or who have had occupational exposure to radiation without adequate protection.

The comparison of outcomes of thyroid cancer patients who had not been exposed to radiation versus patients who were exposed at least three years prior to diagnosis was published in the April 2009 issue of the Archives of Otolaryngology -- Head & Neck Surgery (Vol. 135:4, pp. 355-359).

Lead author Dr. Raewyn Seaberg and colleagues in the department of otolaryngology identified 125 patients treated at Mount Sinai Hospital between 1963 and 2007 who had been exposed to radiation three years or more prior to surgical treatment. They compared the medical treatment required and outcomes of these individuals to those of 574 patients who had never been exposed to radiation.

Fifty-six percent of radiation-exposed patients had been treated for acne or another benign childhood condition, a practice that was common in the 1930s to 1960s. Occupational exposure was the next most common reason for radiation exposure, at 26%, followed by environmental exposure at 11%, radiation to other body sites at 6%, and radioactive iodine treatment at 4%.

The subgroup of patients exposed to direct external radiation therapy to the head and neck accounted for most patients with stage IV disease (56%), MACIS (metastases, age, completeness of surgical excision, local invasion, and tumor size) scores higher than 8 (60%), local recurrence (63%), distant metastases (55%), and death from thyroid cancer (80%).

The aggressiveness of the cancer and the long-term outcomes at a median of 10.6 years were worse for patients who had prior exposure to radiation.

Comparative findings included the following:

Outcomes	Exposure	No exposure
Multifocal tumors	63%	36%
Tumors exhibiting extrathyroid spread	26%	8%
Stage IV disease	16%	5%
Distant metastases	9%	2%
Disease at follow-up	8%	3%
Death from thyroid malignant neoplasm	4%	1.5%
Total or near-total thyroidectomy	83%	38%
Additional operative procedures	23%	2%
Adjuvant external radiotherapy for treatment of malignant lesions	6%	1%