Association of thyroid radiation dose with thyroid dysfunction in patients with locally advanced non-small cell lung cancer treated with concurrent chemoradiotherapy followed by maintenance immunotherapy

Abstract

Background and purpose: We investigated whether incidental irradiation to the thyroid increased the risk of thyroid dysfunction among patients with non-small cell lung cancer (NSCLC) undergoing concurrent chemoradiotherapy (CCRT) followed by maintenance immunotherapy (IO).

Materials and methods: This was a retrospective study of 250 patients diagnosed with locally advanced NSCLC during 2014-2022 who were treated with definitive CCRT followed by maintenance IO. The primary endpoint was the incidence of thyroid dysfunction, which we compared between patients with irradiation of the supraclavicular fossa (the SCFi group) and those without (the non-SCFi group).

Results: By a median follow-up time of 16.6 months, 23/64 patients (35.9%) in the SCFi group and 27/186 patients (14.5%) in the non-SCFi group developed thyroid dysfunction (P < 0.001). The 3-year cumulative incidence of thyroid dysfunction was 54.9% in the SCFi group and 17.0% in the non-SCFi group (P < 0.001). A higher thyroid volume exposed to 10 Gy of radiation (V10Gy) significantly and independently predicted an increased risk of thyroid dysfunction (hazard ratio, 2.82). The 3-year cumulative incidence of thyroid dysfunction was 67.9% in patients with V10Gy ≥ 19.8% and 25.6% in patients with V10Gy < 19.8% (P < 0.001). Via recursive-partitioning analysis, patients were classified into three risk groups based on the V10Gy cutoff of < 19.8% and age cutoff of ≥ 75 years. The 3-year cumulative incidence of thyroid dysfunction was the highest (74.0%) in the high-risk group (P < 0.001).

Conclusion: Incidental irradiation of the thyroid during CCRT is associated with an increased risk of thyroid dysfunction during maintenance IO. This supports the need to minimize the thyroid dose.