Ryan Allen Baker, Presenter: Nothing to Disclose

Gang Han, Abstract Co-Author: Nothing to Disclose

Siriporn Sarangkasiri MS, Abstract Co-Author: Nothing to Disclose

Mary Lou DeMarco, Abstract Co-Author: Nothing to Disclose

Carolyn Turke, Abstract Co-Author: Nothing to Disclose

Craig William Stevens MD, PhD, Abstract Co-Author: Speakers Bureau, MedImmune, Inc

Thomas Jonathan Dilling MD, Abstract Co-Author: Nothing to Disclose

Few analyses have been published regarding clinical and dosimetric factors predictive of RP in patients receiving lung SBRT. We report here on predictive factors from a series of 240 patients.

From 297 isocenters treated in 263 patients, 263 isocenters (240 patients) had evaluable information regarding RP. Age, gender, current smoking status and pack-years, lobe of lung, current O2 use, Charlson Comorbidity Index, prior lung radiotherapy (yes/no), dose/fractionation, V5, V13, V20, Vprescription, mean lung dose (MLD), GTV and PTV volume, total lung volume, PTV/lung volume ratio, and Conformality Index were recorded.

Median follow-up was15.6 months (range: 3.0 – 58.7 months). Twenty-nine patients (11.0%) developed symptomatic pneumonitis (26 grade 2, 3 grade 3). The mean V20 was 6.5% (0.4 – 20.2%) and the average MLD was 5.03 Gy (0.55-12.2 Gy). In univaraible analysis, female gender (p=0.0257) and Age-Adjusted Charlson Comorbidity Index (p=0.0366) were significantly predictive of RP. Among dosimetric parameters, V5 (p=0.0186), V13 (p=0.0438) and Vprescription (where dose = 60 Gy) (p=0.0128) were significant. Vprescription was not significant in patients receiving 50 Gy. There was only a trend toward significance for V20 (p=0.0610). PTV/normal lung volume ratio was highly significant (p=0.0024). However, Conformality Index was not statistically predictive. In multivariable analysis, the clinical factors of female gender, pack years smoking, and larger GITV and PTV volumes were predictive (p=0.0094, 0.0312, 0.0364, and 0.052, respectively), but no dosimetric factors were significant.

In this large series of patients, it appears that clinical factors (not just dosimetric ones) are predictive of pneumonitis. The interrelationship between these variables is unclear. It may be, for instance, that female gender correlated with smaller lung volumes (and therefore a higher ratio of GTV or PTV to normal lung volume). These factors would secondarily lead to higher V5, V13, V20, and MLD. Therefore, clinical factors might be the predominant predictors when treating patients with SBRT to the lung.

Female gender, pack years smoking, and larger GITV and PTV volumes were predictive of radiation pneumonitis in patients undergoing SBRT to the lung.  

Baker, R, Han, G, Sarangkasiri, S, DeMarco, M, Turke, C, Stevens, C, Dilling, T, Clinical (and Not Dosimetric) Factors Might Be of Primary Importance When Predicting Radiation Pneumonitis (RP) in Patients Treated with Stereotactic Radiotherapy (SBRT) to the Lung.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033148.html