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P1.03 - Poster Session/ Treatment of Locoregional Disease – NSCLC (ID 212)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
P1.03-019 - NTCP-Models for Esophagitis with Dose-Differentiated-Radiotherapy (DART-Bid) (ID 85)
09:30 - 17:00 | Author(s): F. Zehentmayr
The primary dose-limiting toxicity during thoracic irradiation is acute esophagitis (AE). The aim of this study is to investigate dosimetric and clinical predictors for AE grade ≥ 2 in patients treated with accelerated radiotherapy.
66 patients were included in the present analysis: 4 stage II, 44 stage IIIA and 18 stage IIIB. All patients received induction chemotherapy followed by dose differentiated accelerated radiotherapy (DART-bid). Depending on size (mean of three perpendicular diameters) tumors were binned in four groups: <2.5 cm 73.8 Gy, 2.5–4.5 cm 79.2 Gy, 4.5–6 cm 84.6 Gy, >6 cm 90 Gy. Patients were treated in 3D target splitting technique. In order to estimate the normal tissue complication probability (NTCP), two Lyman models and the cutoff-logistic regression model were fitted to the data with AE ≥ grade 2 as statistical endpoint. Toxicity was documented prospectively according to RTOG.
The median follow up was 686 days (range 84–2921 days), 23/66 patients (35%) experienced AE ≥ grade 2. The Lyman-MED model (D50=32.8 Gy, m=0.48) and the cutoff dose model (D~c~=38 Gy) provide the most efficient fit to the current dataset. On multivariate analysis V38 was the most significant predictor of AE ≥ grade 2 (HR=1.05, CI 1.01–1.09, p=0.009).
Following high-dose accelerated radiotherapy the rate of AE ≥ grade 2 is lower than reported for concomitant radio-chemotherapy with the additional benefit of markedly increased loco-regional tumor control. In the current patient cohort the most significant predictor of AE was found to be V38 (volume of the esophagus that receives 38 Gy or above, CI 28.2 – 57.3).
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