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J. Callahan
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MO17 - Radiotherapy I: Stereotactic Ablative Body Radiotherapy (ID 106)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Radiation Oncology + Radiotherapy
- Presentations: 1
- Moderators:M. Zwitter, S.K. Vinod
- Coordinates: 10/29/2013, 16:15 - 17:45, Bayside 204 A+B, Level 2
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MO17.01 - Response assessment of Stereotactic Ablative Body Radiotherapy (SABR) for pulmonary metastases: utility of 4D-FDG-PET and CT perfusion (ID 2225)
16:15 - 16:20 | Author(s): J. Callahan
- Abstract
- Presentation
Background
Response assessment using conventional RECIST criteria after SABR of lung targets can be confounded by fibrotic response. The purpose of this study was to evaluate the utility of 4D-FDG-PET/CT and CT perfusion scans in the response assessment of single fraction SABR for inoperable pulmonary oligometastases.Methods
This is a prospective ethics approved clinical study of patients undergoing single fraction SABR with 26Gy for pulmonary metastases. Eligible patients had 1-2 metastases with no extrathoracic disease on staging FDG-PET. Serial 3D / 4D-FDG-PET and CT perfusion studies were performed at baseline, 14 days and 70 days after therapy. Two radiologists independently reported CT perfusion scans.Results
At a median follow-up of 16 months (range 3-27), 10 patients with 13 metastases received SABR. A further 7 patients (41%) were screened from the study due to interval progression of disease between the time of the original FDG-PET and trial 4D-FDG-PET / perfusion CT. The mean time between the original FDG-PET and trial scans was 62 days. No patient progressed locally, 7/10 patients progressed distantly of which 2/7 received subsequent SABR. At the end of study period, 5/10 patients are alive without disease. The median progression free survival was 14 months. The change in SUVmax from baseline was higher on 3D than 4D-PET by a mean of 20.6% (range 0.2%-47.2%) at 14 days and 14.8% (range 0-37.8%) at 70 days. Overall, the SUVmax increased at 14 days (mean 104.9%, p<0.01) and decreased at 70 days (mean=55.5%, p<0.01), despite persistent morphological lesions on the concurrent late timepoint CT. There was strong level of inter-observer agreement of CT perfusion interpretation with a median intraclass correlation coefficient of 89% (range 57%-98%). Perfusion parameters of Time to Peak Blood Flow and Blood Volume showed a median increase of 18.8% and 23.0% at 2 weeks post-therapy and decreased below baseline by a median 7.0% and 14.0% at 70 days (non-significant).Conclusion
High rates of interval progression between staging scans indicates a need to expedite management of oligometastases in a timely fashion. Increased tumour perfusion and FDG-PET intensity at 2 weeks post-RT is likely due to an inflammatory response to large single dose SABR. Late PET response was associated with tumour control despite CT apparent morphological lesions. Conventional 3D PET may overestimate change in PET intensity post SABR as compared to 4D PET. These findings, in particular CT perfusion findings, require a larger patient cohort for validation.Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
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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
- Moderators:M.M. Tin, F. Macbeth
- Coordinates: 10/30/2013, 10:30 - 12:00, Bayside 204 A+B, Level 2
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MO23.01 - Four-dimensional Gallium-68 perfusion PET/CT scans can improve radiotherapy planning through functional avoidance of lung (ID 2490)
10:30 - 10:35 | Author(s): J. Callahan
- Abstract
- Presentation
Background
[68]Ga-macroaggregated-albumin ([68]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) [68]Ga-perfusion PET/CT for functional adaptation of radiation therapy (RT) planning in patients with non-small cell lung cancer (NSCLC).Methods
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.Results
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.Conclusion
This is the first study of [68]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.Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.
