Risk of Pneumonitis After Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer in Patients With Prior Anatomic Resection

Abstract

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has emerged as a standard treatment option for early stage, medically inoperable non-small cell lung cancer (NSCLC). Dosimetric factors including lung volume receiving 20 Gy (V20) >10%and mean lung dose (MLD) >4 Gy are established risk factors for radiation pneumonitis (RP) following SBRT, but limited data evaluate the relative risk of RP in patients undergoing SBRT following prior anatomic lung resection (ALR). This study assessed the incidence of RP and all grade 2+ pulmonary toxicity in patients treated with SBRT for NSCLC following ALR and compare toxicity rates to patients without prior ALR. Materials/Methods: The medical records of 83 consecutive patients with T1-T3 NSCLC treated with 87 courses of SBRT for 93 lung tumors (16 central, 77 peripheral) between January 2007 and September 2013 were reviewed. Sixteen patients with a history of prior ALR were identified, including lobectomy (n Z 12), bilobectomy (nZ 1), and pneumonectomy (n Z 3), with 67 patients without history of prior ALD. The most commonly used fractionation regimen was 50Gy in 5 fractions. Toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v.4.0. Rates of grade 2+ RP and any grade 2+ pulmonary toxicity were compared between patients with and without prior ALR. Crude rates of RP and all grade 2+ pulmonary toxicity were compared using Fisher’s exact test. Actuarial estimates of freedom from RP (FFRP), in-lobe control (ILC), and overall survival (OS) were calculated with the Kaplan-Meier method and compared between cohorts via the log rank method. Results: At a median follow up of 11.9 months (range 1.2 to 81 months), 3 patients developed grade 2+ RP at a median of 4.0 months (range: 1.0-14.8 months). The crude rates of RP were 6.3% and 2.9% for patients with and without prior ALD, respectively (p>0.05). The 2 year Kaplan-Meier estimates of freedom from RP were 86% and 97% (p>0.05). Crude rates of all grade 2+ pulmonary toxicity were 11.8% and 2.9%, respectively, with associated 2 year estimates of 97% and 81%, respectively (p>0.05). The 2 cohorts were well matched by mean lung dose (4.67 Gy vs 4.15 Gy), lung V20 (5.16% vs 4.35%), mean PTV (30.63 cc vs 36.16 cc), and median prescribed dose (50 Gy vs 54) (p>0.05 for all). Conclusions: Observed rates of pulmonary toxicity were low among patients treated by SBRT after ALR. These data provide reassurances that SBRT can be performed safely for patients with prior ALR when conventional lung DVH constraints are utilized. Author Disclosure: J.T. Hayes: None. A.M. Chen: None. M.E. Daly: None.