The association between RT-induced changes in lung density and global lung function.
13543 Background: Radiation (RT)-induced lung injury is a common side effect following thoracic RT. The study of RT-induced lung injury is complicated by the multiple endpoints considered (e.g., radiologic vs. symptomatic vs. functional). The association between these endpoints is not entirely clear. We herein assess the association between RT-induced changes in computed tomography (CT)-defined lung density and pulmonary function tests (PFTs). METHODS: As part of a prospective clinical study, patients receiving incidental partial lung irradiation underwent PFTs and CT scans before and serially 3-6 months after RT. Patient characteristics are as follows: the majority of patients presented with lung cancer (82%), median age was 62 (range 22-87), 50% received chemotherapy, the median prescribed RT dose was 64 Gy (range 23-86 Gy), and the median mean lung dose (MLD) was 17 Gy (4-36 Gy). Regional lung density was assessed by CT scans and global lung function by PFTs. The percent reductions in PFTs were compared to the average changes in lung density using Pearson correlations. RESULTS: 111 patients had a total of 203 concurrent CT lung density and PFT evaluations during 3- to 24-month post-RT follow-up intervals available for analyses. The average changes in lung density were quantitatively related to the percent reductions in PFTs, albeit with modest correlation coefficients (r), (see table ). The results were similar in patients treated with and without chemotherapy. CONCLUSIONS: There is a quantitative association between the degree of increase in lung density as defined by CT and the percent reduction in PFTs. These results support the concept of a parallel architecture within the lung where the sum of regional injury may be associated with changes in global function. [Table: see text] [Table: see text].
Ma, J; Zhang, J; Zhou, S; Hubbs, JL; Foltz, RJ; Hollis, DR; Light, KL; Wong, TZ; Kelsey, CR; Marks, LB
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