title: Association between white blood cell count following radiation therapy with radiation pneumonitis in non-small cell lung cancer.
abstract: OBJECTIVE
  Radiation pneumonitis (RP) is an inflammatory response to radiation therapy (RT). We assessed the association between RP and white blood cell (WBC) count, an established metric of systemic inflammation, after RT for non-small cell lung cancer.
  
  
  METHODS
  We retrospectively analyzed 366 patients with non-small cell lung cancer who received ≥60 Gy as definitive therapy. The primary endpoint was whether WBC count after RT (defined as 2 weeks through 3 months after RT completion) was associated with grade ≥3 or grade ≥2 RP. Median lung volume receiving ≥20 Gy (V20) was 31%, and post-RT WBC counts ranged from 1.7 to 21.2 × 10(3) WBCs/μL. Odds ratios (ORs) associating clinical variables and post-RT WBC counts with RP were calculated via logistic regression. A recursive-partitioning algorithm was used to define optimal post-RT WBC count cut points.
  
  
  RESULTS
  Post-RT WBC counts were significantly higher in patients with grade ≥3 RP than without (P<.05). Optimal cut points for post-RT WBC count were found to be 7.4 and 8.0 × 10(3)/μL for grade ≥3 and ≥2 RP, respectively. Univariate analysis revealed significant associations between post-RT WBC count and grade ≥3 (n=46, OR=2.6, 95% confidence interval [CI] 1.4‒4.9, P=.003) and grade ≥2 RP (n=164, OR=2.0, 95% CI 1.2‒3.4, P=.01). This association held in a stepwise multivariate regression. Of note, V20 was found to be significantly associated with grade ≥2 RP (OR=2.2, 95% CI 1.2‒3.4, P=.01) and trended toward significance for grade ≥3 RP (OR=1.9, 95% CI 1.0-3.5, P=.06).
  
  
  CONCLUSIONS
  Post-RT WBC counts were significantly and independently associated with RP and have potential utility as a diagnostic or predictive marker for this toxicity.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Chad
authors.initials: C
authors.lastname: Tang
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Gomez
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Levy
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhuang
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Ting
authors.initials: T
authors.lastname: Xu
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Quynh
authors.initials: Q
authors.lastname: Nguyen
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: zliao@mdanderson.org.
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Liao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000704:Analysis of Variance; D019540:Area Under Curve; D002289:Carcinoma, Non-Small-Cell Lung / Q000097:blood* / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008175:Lung Neoplasms / Q000097:blood* / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D017564:Radiation Pneumonitis / Q000097:blood* / Q000175:diagnosis; D012189:Retrospective Studies