Anaplastic Thyroid Cancer Patterns of Nodal Disease and Proposed Radiotherapy Target Volumes

R. W. Gao, Robert Foote, Y. Garces, Daniel J Ma, M. A. Neben-Wittich, D. M. Routman, Samir H Patel, S. Ko, L. A. McGee, Keith Christophe Bible, A. V. Chintakuntlawar, J. C. Morris, M. Rivera, F. Abraha, S. C. Lester

Research output: Contribution to journalArticlepeer-review

Abstract

PURPOSE/OBJECTIVE(S): Radiotherapy (RT) plays an important role in locoregional control for anaplastic thyroid cancer (ATC). Due to its rarity, RT guidelines for ATC are lacking. In this single institution retrospective analysis, we describe ATC patterns of nodal disease at presentation, recurrence, and progression and propose corresponding RT target volumes. MATERIALS/METHODS: We used a prospectively maintained database to identify all ATC patients with definitive or adjuvant IMRT and chemotherapy from 2006 to 2020. Patients receiving palliative RT were excluded. We identified in-field, marginal (within the 40-50 Gy isodose line), and out-of-field sites of locoregional recurrence and progression (LRR). Sites of disease at presentation and LRR were mapped to inform RT target volume recommendations. RESULTS: Forty-seven patients met inclusion. Median follow-up was 6.6 months (IQR: 1.9-19.6). Forty-four (93.6%) patients underwent resection. Table 1 summarizes RT nodal coverage and sites of disease. All patients received elective nodal RT to levels II-IV and VI. RT volumes also included: IA (23.4%), IB (44.7%), V (87.2%), VII (27.7%), and mediastinal 1-6 (53.2%). Cumulative incidence of LRR at 3- and 12-months was 26.1% (95% CI: 15.9-42.8) and 35.7% (23.9-53.4). Isolated LRR risk at 3- and 12-months was 6.5% (2.2-19.8) and 8.9% (3.4-22.9). Fourteen (29.8%) in-field LRRs occurred at a median interval of 44 days (range: 15-208) from completion of RT. Sites of in-field LRR included the postoperative thyroid bed, ipsilateral III-IV, VI, 1, and 3A. Four (8.5%) patients experienced marginal LRRs at a median of 35 days (range: 32-139), 3 of whom progressed in the mediastinum at 2, 3P, 4, and 6. Two (4.3%) patients experienced out-of-field LRRs at VII and the contralateral retromolar trigone, respectively. Throughout the pre-treatment and follow-up period, no patients had disease at IA and 1 (2.1%) patient each had disease at IB and VII. Five (10.6%) patients had bilateral neck disease. No baseline or treatment characteristics, including RT dose (stratified by < or ≥66 Gy), were significant predictors of LRR on univariate analysis. Twelve (25.5%) patients were alive at last follow-up, of whom 8 (17.0%) had no evidence of LRR or distant progression. CONCLUSION: Isolated LRR risk in ATC patients treated with comprehensive RT and chemotherapy is low. Complete inclusion of mediastinal levels 1-6 is warranted to avoid marginal failures. Distant recurrence remains common and additional efforts are needed to appropriately select patients for comprehensive treatment. No dose-response relationship was observed between 51 and 70 Gy.

Original languageEnglish (US)
Pages (from-to)e418-e419
JournalInternational journal of radiation oncology, biology, physics
Volume111
Issue number3
DOIs
StatePublished - Nov 1 2021

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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