Outcomes and Patterns of Recurrence for Anaplastic Thyroid Cancer Treated With Comprehensive Chemoradiotherapy

Area of Science:

• Oncology
• Radiation Oncology
• Head and Neck Cancer

Background:

• Anaplastic thyroid cancer (ATC) is rare, leading to a lack of established radiation therapy (RT) guidelines.
• RT is crucial for locoregional tumor control in ATC.

Purpose of the Study:

• To describe patterns of nodal disease in ATC at presentation and progression.
• To propose evidence-based RT target volumes for ATC based on observed disease patterns.

Main Methods:

• Retrospective review of 47 ATC patients treated with intensity-modulated RT and chemotherapy (2006-2020).
• Analysis of locoregional recurrence (LRR) sites: in-field, marginal, and out-of-field.

Main Results:

• Nodal involvement varied, with levels II, III, IV, and VI most common at presentation.
• Comprehensive RT including elective nodal RT to levels II-IV and VI, plus additional volumes, resulted in a 3-month and 12-month cumulative incidence of LRR of 26.1% and 35.7%, respectively.
• Isolated LRR risk at 3 and 12 months was low (6.5% and 8.9%). Marginal failures occurred primarily in the mediastinum.

Conclusions:

• Comprehensive RT and chemotherapy for ATC yield a low isolated LRR risk.
• Inclusion of mediastinal levels 1-6 in RT volumes may be beneficial.
• Omission of levels I and retropharyngeal/retrostyloid (RP/RS) nodal regions may be considered.