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MO23 - Radiotherapy II: Lung Toxicity, Target Definition and Quality Assurance (ID 107)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Radiation Oncology + Radiotherapy
- Presentations: 1
MO23.01 - Four-dimensional Gallium-68 perfusion PET/CT scans can improve radiotherapy planning through functional avoidance of lung (ID 2490)
10:30 - 12:00 | Author(s): D. Pham
Ga-macroaggregated-albumin (Ga-MAA) perfusion PET/CT is a novel molecular imaging technique for the assessment of functional lung volumes. This prospective study aims to investigate the utility of four-dimensional (4D) Ga-perfusion PET/CT for functional adaptation of radiation therapy (RT) planning in patients with non-small cell lung cancer (NSCLC).
An interim analysis was performed of a prospective clinical study of patients with NSCLC who underwent 4D-perfusion PET/CT scanning prior to curative intent RT. All patients were planned to 60Gy in 30fx with or without concurrent chemotherapy based on conventional anatomical lung volumes. Subsequently, a single nuclear medicine physician in conjunction with a single radiation oncologist contoured the functional ‘perfused’ lung using a visually adapted threshold. Functional lung was defined as lung parenchyma with Ga-MAA uptake. A second volume labeled as ‘high-perfused’ lung was created based on a visually adapted 30% max SUV threshold (figure 1). A single RT planner optimised the 3D conformal radiotherapy plan to spare the functionally ‘perfused’ and ‘high-perfused’ lung volumes respectively. Dose volumetrics were compared using mean lung dose (MLD), V5, V10, V20, V30, V40, V50 and V60 parameters. Figure 1 figure 1 - RT Plans optimised to each of the conventional, 'perfused' and 'high perfused' lung volumes.
14 consecutive patients had RT plans adapted to functional lung volumes based on perfusion PET/CT. This patient cohort consisted of ex-smokers with pre-existing airways disease, with a mean FEV1 of 1.87L (0.83L-2.82L) and DLCO of 54% (27%-87%). The average MLD of the original treatment plans was 11.44Gy using conventional anatomical lung measurements. When considering the functional ‘perfused’ lung and ‘high perfused’ lung, the original plan produced an average MLD of 11.12Gy and 12.41Gy respectively. Plans optimized for ‘perfused’ lung only showed significant improvement of the V60 dose parameter (median 1.00Gy, p=0.04). However, plans optimized for ‘high perfused’ lung improved MLD, V30, V40, V50 and V60 (all p-values <0.05). The MLD was improved by a median of 0.86Gy, p<0.01. The largest improvement was found in the V30 parameter, with a median difference of 1.76Gy.
This is the first study of Ga perfusion PET/CT for planning the treatment of lung cancer patients. RT plans adapted to ‘high perfused’ but not ‘perfused’ functional lung volumes allows for significant technical improvement of conventional RT for NSCLC patients. The clinical impact of this improvement in planning technique should be validated in the context of a prospective study measuring patient toxicity outcomes.
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