Is Perfusion Dose-Response Different Than Ventilation Dose-Response for Lung Cancer Patients Treated With Radiotherapy?

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International Journal of Radiation Oncology, Biology, Physics



Ventilation-perfusion dose-response studies have focused on using functional imaging to characterize a dose-response and to assess whether the dose-response can predict subsequent pulmonary toxicity. Current dose-response studies typically focus on a single modality (ventilation or perfusion) and perform assessments on a population-based basis. There is no work evaluating whether ventilation dose-response differs from perfusion dose-response for individual lung cancer patients. The purpose of this study was to use single photon emission computed tomography (SPECT)-CT ventilation-perfusion imaging to quantitatively and clinically evaluate whether lung cancer patients treated with radiotherapy have differences between their ventilation and perfusion dose-responses.


Twenty patients with biopsy proven lung cancer enrolled on a prospective functional avoidance protocol underwent SPECT-CT perfusion-ventilation scans pre- and 3-month post-radiotherapy. The SPECT-CT, planning CT, and dose distribution were rigidly registered. We calculated the relative changes in pre- to post-treatment ventilation-perfusion in lung regions receiving ≥ 20 Gy (referred to as ΔPV20 for perfusion and ΔVV20 for ventilation). Differences between perfusion-based ΔPV20 and ventilation-based ΔVV20 were assessed and referred to as ΔfV20. A radiologist read each pre- and post-treatment ventilation-perfusion scans using a semi-quantitative scale that assigned a score ranging from 1 to 8 that reflected functional defect and heterogeneity in each lung. The difference between radiologist scores for the pre- and post-treatment scans was calculated for both ventilation and perfusion. Differences between ventilation-based and perfusion-based radiologist scores were assessed.


Twenty-five percent of patients had a difference of ΔfV20 > 35% between ventilation-perfusion pre- to post-treatment changes (ΔVV20 and ΔPV20) and 20% of patients had opposite directions for ventilation-perfusion pre- to post-treatment changes. Radiologist assessment resulted in 20% of patients having different ventilation-perfusion semi-quantitative change scores for ipsilateral lungs.


The current work employed quantitative metrics and clinical assessments to evaluate whether ventilation dose-response differs from perfusion dose-response for individual lung cancer patients. Our data showed that ventilation dose-response can differ from perfusion dose-response for 20% to 30% of patients. Our study demonstrates that when evaluating functional dose-response for lung cancer patients, it is insufficient to look at ventilation or perfusion alone for a subset of patients; but rather both modes of functional imaging may be needed when predicting for clinical outcomes.





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