Patient selection for DIBH radiotherapy of locally advanced non-small cell lung cancer
Kristine Fjellanger,
Norway
OC-0935
Abstract
Patient selection for DIBH radiotherapy of locally advanced non-small cell lung cancer
Authors: Kristine Fjellanger1,2, Linda Rossi3, Ben J. M. Heijmen3, Helge Egil Seime Pettersen1, Inger Marie Sandvik1, Sebastiaan Breedveld3, Turid Husevåg Sulen1, Liv Bolstad Hysing1,2
1Haukeland University Hospital, Department of Oncology and Medical Physics, Bergen, Norway; 2University of Bergen, Institute of Physics and Technology, Bergen, Norway; 3Erasmus MC Cancer Institute, Department of Radiotherapy, Rotterdam, The Netherlands
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Purpose or Objective
Deep inspiration breath hold (DIBH) during radiotherapy treatment can reduce the risk of radiation pneumonitis (RP) and 2-year mortality compared to treatment in free breathing (FB) for patients with locally advanced non-small cell lung cancer (LA-NSCLC). DIBH is not commonly used for this patient group, although the equipment to perform DIBH is available in many clinics. The extra time needed for imaging, comparative planning and treatment in DIBH could be a factor preventing its use in busy clinics. This study investigates if specific patient and tumor characteristics predict the benefit of DIBH, in order to prioritize the patients with the greatest benefit.
Material and Methods
In a prospective study, 4DCTs and DIBH CTs were acquired at treatment planning for 37 patients with LA-NSCLC. Treatment plans in FB and DIBH were generated without manual intervention, using a system for automated multi-criterial planning. Normal tissue complication probabilities (NTCPs) for radiation pneumonitis (RP) grade ≥2 and 2-year mortality were calculated for each technique using validated models. Correlations between the ∆NTCPs between FB and DIBH and the following patient characteristics were investigated: primary tumor location in right vs. left lung and upper vs. lower lobes, expansion of the lungs with DIBH (relative increase in lung volume compared to FB) and cranio-caudal motion extension of the primary tumor in FB (breathing motion). The Wilcoxon signed-rank test was used for related samples and linear regression was used to test correlations between two continuous variables. p-values ≤0.05 were considered statistically significant.
Results
The NTCP for RP was significantly lower with DIBH than FB regardless of tumor position (Figure 1), and there was no correlation between ΔNTCP and tumor motion in FB (p = 0.1) or lung expansion with DIBH (p = 0.2).
For 2-year mortality, the benefit of DIBH depended on tumor location. 83%, 79% and 80% of the patients with tumors in the left upper lobe, right upper lobe and left lower lobe, respectively, had a lower NTCP for 2-year mortality with DIBH than FB (ΔNTCP range -4.6 to 0.6 pp). This benefit was seen only for 43% of the patients with tumors in the right lower lobe (ΔNTCP range -1.2 to 3.7 pp) (Figure 2). No correlation was found between ΔNTCP and tumor motion in FB (p = 0.3) or lung expansion with DIBH (p = 0.9).
Conclusion
DIBH reduced the NTCPs for RP for 92% and 2-year mortality for 74% of LA-NSCLC patients. While DIBH reduced the risk of RP consistently regardless of patient characteristics, the ability to reduce the risk of 2-year mortality was evident among patients with upper and left lower lobe tumors but not right lower lobe tumors. The anatomical changes that occur during DIBH, with compression and shifting of the heart and expansion of the lungs, have different effects on the risk of mortality depending on tumor location.