Stereotactic radiotherapy (SRT) for differentiated thyroid cancer (DTC) oligometastases: an AIRO (Italian association of radiotherapy and clinical oncology) systematic review

Purpose: The aim of this systematic review was to examine efficacy of stereotactic radiotherapy (SRT) in patients with oligometastatic thyroid cancer. Materials and methods: A systematic search was conducted by means of PubMed, Scopus, and Cochrane library. Clinicaltrials: gov was searched for ongoing or recently completed trials, and PROSPERO was searched for ongoing or recently completed systematic reviews. We analyzed only clinical studies as full text carried out on patients with oligometastatic thyroid cancer treated with SRT. Conference papers, surveys, letters, editorials, book chapters, and reviews were excluded. Time of publication was restricted to the years 1990-2021. Results: The number of evaluated patients was 146 (267 lesions), and the median age was 58 years. The median 1-year local control (LC) was 82% (range 67.0%-97.1%); the median disease-free survival (DFS) was 12 months (range 4-53); the median 1-year overall survival was 72% (range 66.6%-85.0%); the 3-year cancer-specific survival was 75.0%; and the 4-year cancer-specific survival was 37.5%. No grade 3-5 acute toxicity was reported. No late effects were recorded. Conclusions: SRT for oligometastases from thyroid cancer as salvage therapy is well tolerated and yields high rates of LC and prolonged DFS.