Elevated thyroglobulin levels and negative I-131 whole body scans: Six-year experience in United Arab Emirate

Abstract

16508 Purpose: This is a retrospective study of thyroid cancer patients seen at Oncology Department at Mafraq Hospital/UAE from 1/1999 to 12/2005. Clinical data, prognostic factors and treatment outcomes were studied, special emphasis was put on patients with elevated Serum Thyroglobulin (TG) and negative I-131 whole body scans. Patients and Methods: Total of 144 patients were fully evaluated, intent to treat analysis was used. All patients were treated surgically and post-op thyroid technician 99 scan were performed. I-131 ablation was given if the tumor size was =1 cm or if =1 cm (micropapillary) and multi-focal. Post ablation scan was done on day 10 and thyroxin was given in suppressive doses. Periodic evaluations were done with TG level, I-131 whole body scan, neck US and CXR. Plain CT scans and PET scans were done in selected cases. Results: Male to female ratio 1:2.42, non-smokers were 90%, non-alcoholics were 99%, Diabetes and Hypertension were associated in 28% of cases, family history of thyroid cancer was noted in 8%, papillary carcinoma was seen in 85.8%, follicular cancer in 11.6%, hurthel cell cancer in 0.83% and medullary cancer in 0.17%. Vascular and lymphatic invasion was noted in 29% of all cases. Interesting all patients with vascular or lymphatic invasion relapsed locally or distantly. Post-operative thyroid scan showed residual thyroid tissue in 96% of cases. During follow up TG levels (cut off 5.0 ng/ml) were elevated in 52 patients (37% cohort). Diagnostic I-131 scans were done in 36 patients and were positive in 24 patients (67%) and negative in 12 patients (33%). In the 12 patient group of research interest with elevated TG and negative I-131 whole body scans, 9 received high dose I-131 therapy. Of these patients 8 (88%) showed positive post therapy scan and 1 (12%) showed negative post therapy scan. Conclusion: 1. TG is more sensitive marker than diagnostic I-131 scan in making treatment decisions. 2. Lympho vascular invasion has adverse prognostic value. No significant financial relationships to disclose.