High-resolution pulmonary ventilation and perfusion PET/CT allows for functionally adapted intensity modulated radiotherapy in lung cancer.
OBJECTIVE
To assess the utility of functional lung avoidance using IMRT informed by four-dimensional (4D) ventilation/perfusion (V/Q) PET/CT.


METHODS
In a prospective clinical trial, patients with non-small cell lung cancer (NSCLC) underwent 4D-V/Q PET/CT scanning before 60Gy of definitive chemoradiation. Both "highly perfused" (HPLung) and "highly ventilated" (HVLung) lung volumes were delineated using a 70th centile SUV threshold, and a "ventilated lung volume" (VLung) was created using a 50th centile SUV threshold. For each patient four IMRT plans were created, optimised to the anatomical lung, HPLung, HVLung and VLung volumes, respectively. Improvements in functional dose volumetrics when optimising to functional volumes were assessed using mean lung dose (MLD), V5, V10, V20, V30, V40, V50 and V60 parameters.


RESULTS
The study cohort consisted of 20 patients with 80 IMRT plans. Plans optimised to HPLung resulted in a significant reduction of functional MLD by a mean of 13.0% (1.7Gy), p=0.02. Functional V5, V10 and V20 were improved by 13.2%, 7.3% and 3.8% respectively (p-values<0.04). There was no significant sparing of dose to functional lung when adapting to VLung or HVLung. Plan quality was highly consistent with a mean PTV D95 and D5 ranging from 60.8Gy to 61.0Gy and 63.4Gy to 64.5Gy, respectively, and mean conformity and heterogeneity index ranging from 1.11 to 1.17 and 0.94 to 0.95, respectively.


CONCLUSIONS
IMRT plans adapted to perfused but not ventilated lung on 4D-V/Q PET/CT allowed for reduced dose to functional lung whilst maintaining consistent plan quality.
Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Australia.
Shankar
S
Siva
Department of Radiotherapy Services, Peter MacCallum Cancer Centre, Australia.
Roshini
R
Thomas
Centre for Molecular Imaging, Peter MacCallum Cancer Centre, Australia.
Jason
J
Callahan
Department of Physical Sciences, Peter MacCallum Cancer Centre, Australia.
Nicholas
N
Hardcastle
Department of Radiotherapy Services, Peter MacCallum Cancer Centre, Australia.
Daniel
D
Pham
Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; Department of Physical Sciences, Peter MacCallum Cancer Centre, Australia.
Tomas
T
Kron
Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; Centre for Molecular Imaging, Peter MacCallum Cancer Centre, Australia.
Rodney J
RJ
Hicks
Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Australia.
Michael P
MP
MacManus
Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Australia.
David L
DL
Ball
Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; Centre for Molecular Imaging, Peter MacCallum Cancer Centre, Australia.
Michael S
MS
Hofman
D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods
Function imaging; Functional planning; IMRT; Non-small cell lung cancer; Positron emission tomography