Subclinical thyroid disease after radiation therapy detected by radionuclide scanning.

Abstract

PURPOSE:

The actuarial risk for developing benign or malignant thyroid disease following radiation therapy (RT) is controversial, but may be as high as 50% at 20 years. An effective screening modality should be specific but not overly sensitive, a limitation of ultrasound. We questioned whether Technetium-99 m pertechnetate ((99m)Tc TcO(4)(-)) scanning could detect clinically significant disease in ostensibly disease-free cancer survivors.

METHODS AND MATERIALS:

Eligibility criteria included an interval of at least 5 years after RT to the cervical region, a thyroid gland that was normal to palpation, euthyroid status determined by clinical examination, free T4 and TSH. The 34 patients scanned included 16 children (<18 years old) and 18 adults at the time of RT, 16 females and 18 males. The mean age at RT was 20 years (range, 2.1-50.3 years), and the mean age at (99m)Tc TcO(4)-scanning was 33 years (range, 13.6-58 years), providing a mean interval of 13 years (range, 5.3-26.6 years). The mean RT dose to the thyroid was 36.4 Gy (range, 19.5-52.5). Thyroid scanning was performed with a 5 mCi dose of (99m)Tc TcO(4)(-) obtaining flow, immediate and delayed static, and pinhole collimator images.

RESULTS:

Seven patients (21.6%) had abnormal scans, and the percentage was higher among children (25%) and females (25%) compared to adults (16.7%) and males (16.7%), respectively. Two of 34 patients (5.9%) were discovered to have a thyroid cancer; histopathologies were papillary and follicular carcinoma.

CONCLUSION:

In this population of clinically normal cancer survivors who had been irradiated to the cervical region, subclinical thyroid disease, of potential clinical significance, was detected by (99m)Tc TcO(4)(-) in about 20%. Children may be more commonly affected. Although the cost effectiveness of screening will require a larger sample number, we propose a surveillance schema for this patient population.

• Authors: A Sandhu, L S Constine, R E O'Mara, A Hinkle, A G Muhs, P D Woolf
• Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys) Vol. 48 Issue 1 Pg. 181-8 (Aug 01 2000) ISSN: 0360-3016 [Print] United States
• PMID: 10924988 (Publication Type: Case Reports, Journal Article)

Chemical References

• Radiopharmaceuticals
• Sodium Pertechnetate Tc 99m

Topics

• Adolescent
• Adult
• Carcinoma (diagnostic imaging, etiology)
• Cerebellar Neoplasms (radiotherapy)
• Child
• Child, Preschool
• Female
• Hodgkin Disease (radiotherapy)
• Humans
• Male
• Medulloblastoma (radiotherapy)
• Neoplasms, Radiation-Induced (diagnostic imaging, etiology)
• Neoplasms, Second Primary (diagnostic imaging, etiology)
• Radionuclide Imaging
• Radiopharmaceuticals
• Sodium Pertechnetate Tc 99m
• Thyroid Gland (diagnostic imaging, radiation effects)
• Thyroid Neoplasms (diagnostic imaging, etiology)