Mortality-related factors in 1056 radioiodine-treated patients with well-differentiated thyroid cancer in southern Thailand.

Background: Reported risk factors for death related to well differentiated thyroid cancer vary, possibly depending on the methods and geographical site of data collection.

Method: To evaluate variables related to death in well-differentiated thyroid cancer (WDTC) in a population of southern Thailand, we retrospectively reviewed medical records of all those treated with radioactive iodine (I-131) at the Division of Nuclear Medicine from 1983 to 2002. We found 1056 subjects. Variables examined included present status of subjects (transfer, lost, died), cause of death (related and not related to WDTC), duration of follow-up since surgery, largest size of tumor (when available), gender, histology (follicular or papillary, with mixed included in papillary), age of surgery, and site of spread when treated. Survival from WDTC death utilized Kaplan-Meier and Cox regression analysis.

Results: The median follow-up was 7 years, while only 4 years elapsed from surgery for those who died. We did not know the status of 16% of the subjects despite attempts to contact them. Survival was not affected by age, gender, or maximum size of tumor. Age at surgery was significant only for the group older than 55 years, with a 10-year survival of 76%. The spread of the disease that affected survival can be localized to the aerodigestive tract (10-year survival of 65%) and metastases associated with bone fracture (10-year survival 34%), while other metastases (including asymptomatic bone metastases) exhibited a 10-year survival of 93%. Neither lymph node spread nor elevated Tg at maximum stimulation predicted survival.

Conclusions: To better predict survival of WDTC, site of spread and degree of spread has to be specific.