Prognostic factors and the effect of treatment with radioactive iodine and external beam radiation on patients with differentiated thyroid cancer seen at a single institution over 40 years.
OBJECTIVE
To assess the prognostic factors and the role of radioactive iodine (RAI) and external beam radiotherapy (RT) in patients with differentiated thyroid cancer.


METHODS
A retrospective review of 729 patients treated between 1958 and 1998. The median follow-up was 11.3 years (range 0.3-39.8 years). Primary outcomes included time to cause-specific survival and time to local-regional relapse. Baseline and treatment variables were assessed for statistical significance using the Cox proportional hazards model.


RESULTS
The 10-year cause-specific survival (CSS) was 87.3% and the 10-year local-regional relapse-free rate (LRFR) was 84.9%. In multivariate analysis there was no statistically significant improvement in CSS with more aggressive treatment (i.e. more extensive surgery, the administration of RAI and/or RT). By multivariate analysis the use of RAI resulted in a statistically significant improvement in LRFR (hazard ratio 0.5; 95% confidence interval 0.3-0.8; P = 0.007). In low-risk patients at AJCC stage I < or = 45 years, there was no apparent benefit from RAI. For patients over 60, with extrathyroid extension but no gross residual disease (n = 70), adjuvant external RT resulted in statistically significantly higher CSS (10-year CSS 81.0%vs. 64.6%, P = 0.04) and LRFR (10-year LRFR 86.4%vs. 65.7%, P = 0.01).


CONCLUSIONS
The use of RAI was associated with improved LRFR but not in low-risk patients. External beam RT improved LRFR and CSS in high-risk patients.
Brierley
J
J
Department of Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario, Canada. james.brierley@rmp.uhn.on.ca
Tsang
R
R
Panzarella
T
T
Bana
N
N
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D018265:Carcinoma, Papillary, Follicular / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy; D002648:Child; D003131:Combined Modality Therapy; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011379:Prognosis; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D018714:Radiotherapy, Adjuvant; D013964:Thyroid Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals