Changes in global function and regional ventilation and perfusion on SPECT during the course of radiotherapy in patients with non-small-cell lung cancer

Abstract

Purpose: This study aimed to (1) examine changes in dyspnea, global pulmonary function test (PFT) results, and functional activity on ventilation (V)/perfusion (Q) single-photon emission computerized tomography (SPECT) scans during the course of radiation (RT), and (2) factors associated with the changes in patients with non-small-cell lung cancer (NSCLC).

Methods and materials: Fifty-six stage I to III NSCLC patients treated with definitive RT with or without chemotherapy were enrolled prospectively. Dyspnea was graded according to Common Terminology Criteria for Adverse Events version 3.0 prior to and weekly during RT. V/Q SPECT-computed tomography (CT) and PFTs were performed prior to and during RT at approximately 45 Gy. Functions of V and Q activities were assessed using a semiquantitative scoring of SPECT images.

Results: Breathing improved significantly at the third week (mean dyspnea grade, 0.8 vs. 0.6; paired t-test p = 0.011) and worsened during the later course of RT (p > 0.05). Global PFT results did not change significantly, while regional lung function on V/Q SPECT improved significantly after ∼45 Gy. The V defect score (DS) was 4.9 pre-RT versus 4.3 during RT (p = 0.01); Q DS was 4.3 pre-RT versus 4.0 during RT (p < 0.01). Improvements in V and Q functions were seen primarily in the ipsilateral lung (V DS, 1.9 pre-RT versus 1.4 during RT, p < 0.01; Q DS, 1.7 pre-RT versus 1.5 during RT, p < 0.01). Baseline primary tumor volume was significantly correlated with pre-RT V/Q DS (p < 0.01). Patients with central lung tumors had greater interval changes in V and Q than those with more peripheral tumors (p <0.05 for both V and Q DS).

Conclusions: Regional ventilation and perfusion improved during RT at 45 Gy. This suggests that adaptive planning based on V/Q SPECT during RT may allow sparing of functionally recoverable lung tissue.

Fig. 1

Changes in lung functions during RT are compared to baseline values. Mean dyspnea grade decreased (breathing improved) gradually and became significant by 3 weeks during RT (a). Dyspnea was graded according to Common Terminology Criteria for Adverse Events version 3.0. Compared to baseline values, mean levels of FEV₁, FVC, and DLCO during RT were not statistically different (b). For regional lung functions, DSs in ventilation (c) and perfusion (d) seen on SPECT decreased (lung function improved) significantly. Improvements are seen mostly in the ipsilateral lung; there were no significant changes in the contralateral lung.

Fig. 2

Tumor location and V/Q SPECT-CT scans are shown during RT. Above pictures show V and Q SPECT scans from patients with central and peripheral tumors. Centrally located tumors had greater changes at 45 Gy during RT.

Fig. 3

Lung functional map is shown on SPECT-CT during RT. Scans show changes in functional mapping on SPECT according to underlying causes and their potential impact for radiation planning. Type B3 defects partially recovered, while B1 and B2 defects did not change significantly during RT. The defect classification has been previously described (16). Briefly the A region consists of functional defects corresponding to the location of tumor. The B1 region represents complete function defect induced by COPD or other unrecoverable diseases. The B2 region is reduced lung function induced by unrecoverable diseases. B3 region consists of temporarily dysfunctional lung induced by tumor and other potentially recoverable diseases. The C region is normally functioning lung.

Fig. 4

Schematic illustrates pulmonary function changes during RT.