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. Author manuscript; available in PMC: 2020 Jun 3.
Published in final edited form as: Int J Radiat Oncol Biol Phys. 2017 Dec 1;100(3):606–617. doi: 10.1016/j.ijrobp.2017.11.036

Table 2.

Effect of reirradiation dose on overall survival when controlling for potential confounders among definitive patients who completed treatment (multivariable Cox regression)*

Variable HR 95% CI P value
Dose of reirradiation (continuous, per Gy) 0.957 0.937–0.978 <.0001
Systemic therapy (yes vs no) 1.383 0.869–2.202 .170
Time between RT courses (continuous, per y) 0.982 0.955–1.010 .200
Year of retreatment (continuous, per y) 1.003 0.959–1.048 .900
Organ dysfunction (yes vs no) 1.586 1.140–2.208 .006
Tumor site
 Nasopharynx, base of skull, sinonasal, other Ref Ref Ref
 Oral cavity, oropharynx, larynx, hypopharynx 2.044 1.303–3.205 .002

Abbreviations: CI = confidence interval; HR = hazard ratio; Ref = reference; RT = radiation therapy.

*

Random effects term accounting for baseline institutional differences in hazard demonstrated a variance of 8 × 10−5, suggesting minimal effect; model included 244 patients, 172 events, and 6 degrees of freedom.