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MA23 - Early Stage Lung Cancer: Present and Future (ID 926)
- Event: WCLC 2018
- Type: Mini Oral Abstract Session
- Track: Treatment of Early Stage/Localized Disease
- Presentations: 1
- Coordinates: 9/26/2018, 10:30 - 12:00, Room 105
MA23.06 - Small Residual Setup Errors After Image-Guided Radiotherapy Affect Heart Dose and Are Linked to Overall Survival (ID 13785)
11:05 - 11:10 | Author(s): Corinne Johnson
There is limited evidence of the effect of radiotherapy image guidance on survival. This work investigates the relationship between small residual set-up errors following IGRT and overall survival in lung cancer patients (mostly with significant comorbidities), and explores which anatomy may be responsible for observed differences.a9ded1e5ce5d75814730bb4caaf49419 Method
Residual setup errors of 546 NSCLC patients treated with an off-line 5mm action threshold correction protocol for bony anatomy were summarized per patient as the mean and standard deviation for each axis, as well as the vector magnitude in a direction from tumour towards the heart, and included in multivariate Cox regression. Delivered dose distributions including residual setup errors were estimated and the difference between the delivered and planned dose was compared for patients who did/did not survive longer than 1 year. Permutation testing (n=1000) assessed significance.4c3880bb027f159e801041b1021e88e8 Result
Residual setup errors were not correlated with any pre-treatment clinical variable. Patients with a residual shift towards the heart (mean ~2 mm, max 5mm) have significantly worse overall survival (hazard ratio 1.310, p = 0.001). The average dose in the heart region changes linearly with the residual shift magnitude towards the heart (~0.8Gy/mm). A higher delivered dose than planned in a region at the heart base (Figure 1, arrow) is associated with poorer survival in multivariate analysis (hazard ratio 1.214/Gy, p<0.001).
Small residual shifts after IGRT are strongly associated with overall survival in NSCLC patients, with shifts of the high dose region towards the heart leading to worse survival. The most likely cause of shorter survival is a corresponding increase in dose to the heart base. This analysis provides direct evidence of the importance of accurate patient positioning and highlights the significance of the heart base as a dose sensitive organ in thoracic radiotherapy patients with early effects on survival.6f8b794f3246b0c1e1780bb4d4d5dc53
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