Validation of Effective Dose as a Better Predictor of Radiation Pneumonitis Risk Than Mean Lung Dose: Secondary Analysis of a Randomized Trial
Abstract
PURPOSE
To confirm the superiority of effective dose (Deff) over mean lung dose (MLD) for predicting risk of radiation pneumonitis (RP), using data from patients on a randomized trial of intensity modulated radiation therapy (IMRT) versus passively scattered proton therapy (PSPT).
METHODS AND MATERIALS
The prescribed target dose for the 203 evaluated patients was 66 to 74 Gy (relative biological effectiveness) in 33 to 37 fractions with concurrent carboplatin/paclitaxel. Time to grade ≥2 RP was computed from the start of radiation therapy, with disease recurrence or death considered censoring events. Generalized Lyman models of censored time to RP were constructed with MLD or Deff as the dosimetric parameter. Smoking status (current, former, never) was also analyzed.
RESULTS
Of the 203 patients, 46 experienced grade ≥2 RP (crude incidence 23%) at a median 3.7 months (range, 0.6-12.6 months). The volume parameter estimated for the Deff model was n = 0.5, confirming estimates from earlier studies. Compared with MLD (in which n = 1), the dosimetric parameter Deff, computed using n = 0.5, resulted in a better fit of the Lyman model to the clinical data (P = .010). Using Deff, the model describes RP risk for IMRT and PSPT data combined because no further improvement was found from separate fits (P = .558). Based on Deff, predicted RP risk per patient ranged from 24 percentage points lower to 19 percentage points higher than predictions based on MLD. For patients with similar MLD,…
How strong is the evidence?
Evidence Hub reads this as a secondary / pooled analysis, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 203 participants or records.
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