INTRODUCTION

1. Intensity Modulated versus 3D Conformal Radiation Therapy for Limited Stage-Small Cell Lung Cancer Carmen A. Pereza,1, Amanda McLanea,1, Andreas Rimnera,1, Daphna Y. Gelbluma,1, Richard M. Gewantera,1, Lee M. Krugb,1, Maria C. Pietanzab,1, Kenneth E. Rosenzweiga,2, Abraham J. Wua,1 Department of Radiation Oncologya, Thoracic Oncology Service/Department ofMedicineb, Mount Sinai School of Medicine2, Memorial Sloan-Kettering Cancer Center New York, NY1 INTRODUCTION RESULTS I. Outcomes at median follow-up of 20 months 3DCRT vs. IMRT p= 0.129 p= 0.118 Images courtesy of Margie Hunt 80% • The majority of clinical trials addressing outcomes in limited-stage small cell lung cancer (LS-SCLC) following definitive chemoradiotherapy have relied on 3D conformal radiotherapy (3DCRT) techniques. • Intensity modulated radiotherapy (IMRT) may decrease toxicity or facilitate dose escalation, but clinical data is lacking. p= 0.030 64% 55% 63%, median 40m 36% OBJECTIVE 45%, median 21m To compare disease control outcomes, dosimetric parameters, and toxicity following either 3DCRT- or IMRT-based definitive chemoradiotherapy for LS-SCLC. METHODS p = 0.499 p = 0.062 p = 0.880 Stratified by Stage Retrospective Study Profile • 149 LS-SCLC patients • Diagnosed 2003-2009 • Treated at MSKCC with thoracic RT and platinum-based chemotherapy • 72 treated with 3DCRT • 70/72 (97%) completed intended RT dose • 26/72 (36%) with retrievable dosimetric data • 77 treated with IMRT • 70/77 (91%) completed intended RT dose • 76/77 (99%) with retrievable dosimetric data • Statistics: Kaplan-Meier methods to estimate survival outcomes; Log-rank test to assess univariate associations;Mann-Whitney U test (nonparametric test) to compare the distribution of dosimetric data II. Dosimetric Parameters III. Grade 2+ Toxicity IMRT 3DCRT 8.8% Pneumonitis p= 0.764 7% p= 0.235 34.1% Esophagitis 45.5% 17.1% p= 0.04 Fatigue 35.1% % Incidence CONCLUSIONS • In our dataset, patients with more advanced stage were more likely to be treated with IMRT than 3DCRT. • Overall survival was significantly worse in the IMRT group, presumably due to higher disease stages represented in this group and unaccounted treatment variables. However, local control was not significantly different between the 3DCRT and IMRT-treated patients. • Despite larger treatment volumes, IMRT was associated with similar dosimetric parameters compared to 3DCRT, except for lower hotspots, higher lung volumes receiving low doses of RT (i.e., lung V5 and V10), and lower heart V30. • The rates of grade 2+ toxicity were comparable for IMRT vs. 3DCRT, except for worse fatigue in the IMRT group. This may be in part due to larger treatment volumes in the IMRT group. • Results from ongoing clinical trials may support dose escalation for LS-SCLC in the future. The enhanced conformality of IMRT may facilitate meeting dose constraints in this setting, and based on our retrospective experience, use of this radiation delivery technique does not appear to result in compromised local tumor control in the thorax.