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N. Plumridge
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P2.14 - Radiotherapy (ID 715)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Radiotherapy
- Presentations: 1
- Moderators:
- Coordinates: 10/17/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P2.14-001 - Mid-Treatment Perfusion PET/CT Is More Effective Than Ventilation PET/CT in Functionally-Adapted Radiotherapy for NSCLC (ID 8508)
09:30 - 09:30 | Author(s): N. Plumridge
- Abstract
Background:
To assess the utility of four-dimensional (4D) ventilation/perfusion (V/Q) PET/CT lung imaging to facilitate mid-radiotherapy treatment adaption with volumetric modulated arc radiotherapy (VMAT).
Method:
In a prospective clinical trial, patients with non-small cell lung cancer (NSCLC) underwent [68]Ga-4D-V/Q PET/CT scanning before and during a six-week (60Gy) course of definitive chemoradiation. Functional lung volumes were delineated on both datasets as ‘highly perfused’ (HPLung) and ‘highly ventilated’ (HVLung), using a 70[th] centile SUV threshold. Three VMAT plans were created on the mid-treatment datatsets: optimised to anatomical lung, HPLung, and HVLung volumes, respectively. Functional dose volumetrics were assessed using the parameters of mean lung dose (MLD), and lung volume receiving 5, 20 or 30Gy, (V5, V20, and V30). Plan quality was assessed for consistency with respect to conformity indices, and doses to critical structures.
Result:
The study cohort consisted of 10 patients resulting in a total of 30 VMAT plans. PTV volumes reduced by a mean of 5.5% between scans. HVLung volume increased between scans by a median value of 39.2%. Subsequent volumetric and spatial changes were reflected in varying DICE similarity coefficients, or DSC (ranging from 0.336-0.923). HPLung decreased by a median value of 4.5% with spatial discrepancy represented by DSC of 0.568-0.805. Increase in ventilated function was most prevalent adjacent to the target, limiting the benefit of adaptive planning (Fig 1). Plan quality was consistent with the median PTV D95 ranging from 60.6-61.3Gy, and mean conformity index ranging from 1.23-1.25. Functional MLD of HPLung decreased by a mean of 7.3%, p=0.02. Plans optimised to HPLung resulted in a reduction of perfused lung V5 by a mean of 13.2%, p<0.01, with HVlung plans yielding a decrease in ventilated lung V5 of 9.6%, p=0.02. Fig 1 Figure 1
Conclusion:
To achieve reduced irradiation of functional lung, radiotherapy adaptation is more effectively facilitated by perfusion rather than ventilation imaging.
