Is Perfusion Dose-Response Different Than Ventilation Dose-Response for Lung Cancer Patients Treated With Radiotherapy?
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.
Forghani F, Castillo R, Castillo E, Jones BL, Rusthoven CG, Kwak J, Grills IS, Guerrero TM, Miften M, Vinogradskiy Y. Is perfusion dose-response different than ventilation dose-response for lung cancer patients treated with radiotherapy? International journal of radiation oncology, biology, physics [Internet]. 2021 Nov 1,;111(3):S15. Available from: https://dx.doi.org/10.1016/j.ijrobp.2021.07.065