Changes in pulmonary function after definitive radiotherapy for NSCLC

Abstract

Introduction: The objective of this study was to identify factors associated with early and long-term pulmonary function (PF) changes after definitive radiotherapy for NSCLC patients. PF was measured by spirometry i.e. forced expiratory volume in 1s (FEV1), and forced vital capacity (FVC).

Materials: Early (within the first year) PF change was analyzed in 211 patients with 986 pairs of PF-tests (PFTs). Long-term PF change was analyzed relative to the PF at 12months after radiotherapy in 106 patients (1286 PFTs). To investigate the impact of patient and treatment related factors on PF, they were tested as covariates in multivariable analysis.

Results: Early PF change was quantified at six months after the start of radiotherapy. Smoking status and increasing V60 was associated with a significant decrease in PF, whereas smoking was protective. In addition, neoadjuvant chemotherapy had a negative impact on FVC. Long-term FEV1 and FVC were analyzed using linear regression. Treatment year and V60 had a significant impact on loss of FEV1. V60 had a significant impact on FVC changes.

Conclusion: In this study, early PF change reached a plateau at 6months after the start of radiotherapy for NSCLC. Large volume of lung receiving high dose was associated with long-term FEV1 change.

Keywords: Definitive radiotherapy; Early and long-term changes; NSCLC; Pulmonary function.

Figure 1:

Profile on how patient population for final analysis was established.

Figure 2

a. Data on long-term pulmonary function expressed in FEV₁ from 2 patients. The straight lines are the estimated loss, λ in the model. Zero denotes baseline, i.e. 12 months after start of radiotherapy. b: Data on long-term pulmonary function expressed in FVC from 2 patients. The straight lines are the estimated loss, λ in the model. Zero denotes baseline, i.e. 12 months after start of radiotherapy.

Figure 2

a. Data on long-term pulmonary function expressed in FEV₁ from 2 patients. The straight lines are the estimated loss, λ in the model. Zero denotes baseline, i.e. 12 months after start of radiotherapy. b: Data on long-term pulmonary function expressed in FVC from 2 patients. The straight lines are the estimated loss, λ in the model. Zero denotes baseline, i.e. 12 months after start of radiotherapy.

Figure 3.

Model based on early FVC changes at 6 months relative to baseline. The curves illustrate the model for 4 different groups, and the marks are patient groups. Group number 1, no neoadjuvant chemotherapy plus smokers* (□ patients were divided into 33 percentiles). The same is true for group 2, neoadjuvant chemotherapy and smokers* (□). Group 3, no chemotherapy and non-smokers^o (○) and group 4, chemotherapy and non-smokers^o (◊) are each divided into 2 tiles. The model for FEV₁ changes is not illustrated, since it is the same model despite there is only two covariates having a significant effect on FEV₁ changes at 6 months. *smokers were defined as people having smoked within the last 10 years.^o Non-smokers were defined as never smoker or former- smokers ≥10 years.