Role of Volumetric Modulated Arc radioTherapy (VMAT) in the adjuvant treatment of locally advanced differentiated thyroid cancer: single institution experience.

[PURPOSE] The optimal management of locally advanced differentiated thyroid cancer (DTC) remains a topic of debate, and the adoption of adjuvant external beam radiotherapy (EBRT) is discussed. This study aimed to evaluate the efficacy of EBRT with volumetric modulated arc radiotherapy (VMAT) in improving locoregional relapse-free survival (LRFS) in addition to surgery and radioiodine therapy (RAI). Secondary objective was to assess the tolerability of EBRT with VMAT.

[METHODS] This monocentric, retrospective study included patients with locally advanced DTC, positive resection margins (R1) or lymph node metastases with extra-nodal extension who underwent total thyroidectomy and RAI. Patients were grouped based on whether they received adjuvant EBRT after surgery and RAI, and outcomes were compared.

[RESULTS] Overall, 25 patients were included. EBRT group comprised 10 patients and non-EBRT group 15 patients. In the EBRT group, none experienced locoregional recurrence, compared to 60% in the non-EBRT group. Comparison of the survival curves showed a statistically significant difference (p = 0.043). Additionally, no severe treatment-related adverse effects were reported, indicating good tolerability of EBRT. Distant Disease-Free Survival (DDFS) was similar between the groups.

[CONCLUSION] Adjuvant EBRT using VMAT improves LRFS in patients with locally advanced DTC, without adding significant toxicity. Locoregional control potentially avoid repeated neck surgeries and their associated side effects. Despite some limitations, our findings support the integration of EBRT into treatment protocols for selected high-risk patients. Further studies are needed to confirm these results and to evaluate the long-term impact of EBRT on survival and quality of life.