Abstract
Purpose: To introduce a version of the Lyman normal-tissue complication probability (NTCP) model adapted to incorporate censored time-to-toxicity data and clinical risk factors and to apply the generalized model to analysis of radiation pneumonitis (RP) risk. Methods and Materials: Medical records and radiation treatment plans were reviewed retrospectively for 576 patients with non-small cell lung cancer treated with radiotherapy. The time to severe (Grade ≥3) RP was computed, with event times censored at last follow-up for patients not experiencing this endpoint. The censored time-to-toxicity data were analyzed using the standard and generalized Lyman models with patient smoking status taken into account. Results: The generalized Lyman model with patient smoking status taken into account produced NTCP estimates up to 27 percentage points different from the model based on dose-volume factors alone. The generalized model also predicted that 8% of the expected cases of severe RP were unobserved because of censoring. The estimated volume parameter for lung was not significantly different from n = 1, corresponding to mean lung dose. Conclusions: NTCP models historically have been based solely on dose-volume effects and binary (yes/no) toxicity data. Our results demonstrate that inclusion of nondosimetric risk factors and censored time-to-event data can markedly affect outcome predictions made using NTCP models.
Original language | English (US) |
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Pages (from-to) | 568-574 |
Number of pages | 7 |
Journal | International Journal of Radiation Oncology Biology Physics |
Volume | 72 |
Issue number | 2 |
DOIs | |
State | Published - Oct 1 2008 |
Keywords
- Lung cancer
- Lyman model
- NTCP
- Radiation pneumonitis
- Smoking
ASJC Scopus subject areas
- Radiation
- Oncology
- Radiology Nuclear Medicine and imaging
- Cancer Research