Postoperative External Beam Radiotherapy for Differentiated Thyroid Cancer: Outcomes and Morbidity With Conformal Treatment
Received 8 July 2008; received in revised form 10 September 2008; accepted 23 September 2008. published online 18 December 2008.
Purpose
To review institutional outcomes for patients treated for differentiated thyroid cancer with postoperative conformal external beam radiotherapy (EBRT).
Methods and Materials
This is a single-institution retrospective review of 131 consecutive patients with differentiated thyroid cancer who underwent EBRT between January 1996 and December 2005. Histologic diagnoses included 104 papillary, 21 follicular, and six mixed papillary-follicular types. American Joint Committee on Cancer stage distribution was Stage III in 2 patients, Stage IVa–IVc in 128, and not assessable in 1. Thirty-four patients (26%) had high-risk histologic types and 76 (58%) had recurrent disease. Extraglandular disease spread was seen in 126 patients (96%), microscopically positive surgical margins were seen in 62 patients (47%), and gross residual disease was seen in 15 patients (11%). Median EBRT dose was 60 Gy (range, 38–72 Gy). Fifty-seven patients (44%) were treated with intensity-modulated radiotherapy (IMRT) to a median dose of 60 Gy (range, 56–66 Gy). Median follow-up was 38 months (range, 0–134 months).
Results
Kaplan-Meier estimates of locoregional relapse-free survival, disease-specific survival, and overall survival at 4 years were 79%, 76%, and 73%, respectively. On multivariate analysis, high-risk histologic features and gross residual disease predicted for inferior locoregional relapse-free survival, whereas high-risk histologic features, M1 disease, and gross residual disease predicted for inferior disease-specific and overall survival. The IMRT did not impact on survival outcomes, but was associated with less frequent severe late morbidity (12% vs. 2%).
Conclusions
Postoperative conformal EBRT provides durable locoregional disease control for patients with high-risk differentiated thyroid cancer if disease is reduced to microscopic burden. Patients with gross disease face significantly worse outcomes. The IMRT may significantly reduce chronic radiation morbidity, but requires additional study.
∗Department of Radiation Oncology, UT M.D. Anderson Cancer Center, Houston, TX
†Department of Experimental Diagnostic Imaging, UT M.D. Anderson Cancer Center, Houston, TX
‡Department of Surgical Oncology, UT M.D. Anderson Cancer Center, Houston, TX
§Department of Head and Neck Surgery, UT M.D. Anderson Cancer Center, Houston, TX
‖Department of Endocrine Neoplasia and Hormonal Disorders, UT M.D. Anderson Cancer Center, Houston, TX
Reprint requests to: David L. Schwartz, M.D., Department of Radiation Oncology, Unit 97, UT M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030. Tel: (713) 563-2381; Fax: (713) 563-2331
Supported in part by P01 CA06294, awarded by the National Cancer Institute.
Presented in part at the Seventh International Conference on Head and Neck Cancer, San Francisco, CA, July 2008, and the 50th Scientific Meeting of the American Society of Therapeutic Radiology and Oncology, Boston, MA, September 20–24, 2008.
ABSTRACT