This is the first prospective study to investigate the safety and efficacy of IMPT for the treatment of SCLC. We will utilize adaptive planning throughout the radiation course. In addition, we will study the dosimetric parameters of IMPT and their correlation with treatment-related toxicities, particularly cardiac events.

The goal of intensity-modulated proton therapy (IMPT) is to deliver radiation to the tumor while minimizing exposure to surrounding normal tissues.

Patients enrolled will experience <35% incidence of cardiac events at 1-year. Cardiac events included are acute heart disease, acute myocardial infarction, cardiomyopathy, dysrhythmia, heart failure, pericarditis, and pericardial effusion.

The optimal frequency of conebeam CT during treatment will be determined by a mixed model:

• The local control, distant metastases, patterns of failure will be summarized as frequency and percentage.
• Chi-square test will be used to test their relationships with other categorical variables.
• General linear model will be used to measure their association with continuous covariates with and without adjusting for other factors