Stereotactic body radiotherapy (SBRT) has been established as the standard of care in medically inoperable patients with peripherally located early-stage non–small-cell lung cancer (NSCLC). Our objective is to report outcomes, toxicity, and dose-volume histogram (DVH) data for patients receiving helical tomotherapy–based SBRT.
Michael Dominello, DO, Shauna Campbell, Ahmad Hammoud, Jay Burmeister, PhD, Gregory Dyson, PhD, Michael Snyder, PhD, Andre Konski, MBA, MD, Neha Amin, MD; Barbara Ann Karmanos Cancer Center, Detroit Medical Center, Wayne State University
Background: Stereotactic body radiotherapy (SBRT) has been established as the standard of care in medically inoperable patients with peripherally located early-stage non–small-cell lung cancer (NSCLC). Our objective is to report outcomes, toxicity, and dose-volume histogram (DVH) data for patients receiving helical tomotherapy–based SBRT. We hypothesize that adverse effects and oncologic outcomes using a helical approach will be similar to those previously reported using nonhelical treatment platforms.
Methods: A retrospective review was performed for all consecutive patients with peripheral, early-stage NSCLC, or oligometastatic lung lesions treated at our institution from 2008–2013. All patients were treated with helical tomotherapy-based SBRT, where treatment planning followed full-body immobilized 4-D simulation with or without abdominal compression. Demographic data, DVH data, local failure (LF) as defined by Response Evaluation Criteria in Solid Tumors (RECIST), toxicity using Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0), progression-free survival (PFS), and overall survival (OS) were analyzed. The Kaplan-Meier method was used to estimate survival functions, while Cox regression (for PFS and OS) and competing risks analysis (for LF) were used to analyze the survival endpoints. The Fisher’s exact test was used to analyze association of prior therapy with development of clinical radiation pneumonitis (CRP).
Results: Seventy-six patients (85 lesions) meeting the criteria above were identified. Fifty-three patients (70%) met Radiation Therapy Oncology Group (RTOG) criteria for early-stage NSCLC (American Joint Committee on Cancer [AJCC] 7th ed T1–2aN0M0), whereas 23 (30%) did not. Mean age was 71 years, with 37 (49%) male and 39 (51%) female patients. The most common SBRT fractionation scheme was 48 Gy administered in four fractions over 2 weeks (70%). Local failure rate for all patients at 1 year was 3.2%, and 2-year rate was 10.3%. Median PFS and OS for all patients were 1.42 years (95% confidence interval [CI], 0.95–1.71 and 2.04 years (95% CI, 1.71–NR [not reached]). For patients with early NSCLC, median PFS and OS were 1.35 years (95% CI, 0.95–2.95) and 1.89 years (95% CI, 1.42–NR), respectively. Median percent lung volume receiving minimum 5 Gy (V5) was 21% (9%–54%), V10 = 12% (3%–44%), and V20 = 5% (1%–30%). Mean heart dose was 2.3 Gy, and mean dose to 15 cc of myocardium was 0.8 Gy. Median dose to 1 cc of chest wall or rib for lesions nearby the chest wall was 39 Gy (range: 0–62 Gy). Six patients developed CRP: four patients with grade 2, one with grade 3, and one with grade 5. No patients developed clinical cardiac toxicity. Two patients experienced at least grade 2 chest wall pain following treatment. Prior thoracic surgery (P = .019) was significantly associated with CRP. Prior chemotherapy (P = 1.0), prior conventional thoracic radiotherapy (P = .324), and prior SBRT (P = .520) were not associated with CRP.
Conclusions: This study represents one of the largest series of patients with thoracic tumors treated with helical tomotherapy–based SBRT. Compared with reports from series using nonhelical SBRT platforms, LF rates and toxicity profiles are similar. Patients with prior lung surgery were at significantly higher risk of developing at least grade 2 CRP. Further work is ongoing to determine DVH parameters that may better predict CRP in this patient population. A history of thoracic surgery should be integrated into predicting a risk-to-benefit ratio when considering SBRT.