Fig. 1

STROBE study flowchart and the number of individuals at each stage of the study. ¹We only included those treated (classes 1–2) with only one record to ensure data consistency. ²The Seventh American Joint Committee on Cancer staging clinical stage cT4bNanyM0. ³Conventional fractionated external beam radiotherapy dose ≤ 70 Gy at 1.8–2 Gy/fraction. ⁴Without missing information in the TCR and death registry