For this companion protocol, we intend to make an assessment of both tumor response and local tissue effects. Patients undergoing the correlative investigation will be a subset of the patients already enrolled on the phase II study.

One of the shortcomings of the trial design recognized in the phase I study had to do with the assessment of local effects, both relating to tumor control and adjacent tissue toxicity. For example, response rates were generally incomplete to the therapy, especially at the lower dose level cohorts, and it was not clear if those patients had residual viable tumor capable of sustaining growth. Repeat biopsies in this population are prohibitively toxic. We generally followed these patients with chest x-rays and CT's until there was evidence of progression. At that point, we would perform a PET scan and repeat systemic staging. Since the majority of patients will retain residual "abnormalities" worrisome for residual disease, ideally, there would be data or testing capable of characterizing these abnormalities earlier in the post-treatment course. In the same token, several patients in the phase I study had post treatment imaging changes around the tumor targets. If these patients had symptomatic decline, it was never clear if the treatment effects around the target were actually involved in the overall decline. Certainly, the patient population selected has other medical problems that will continue to cause poor health. Ideally, though, we would refer to data indicating the degree of damage to surrounding normal lung from the ESR such that a realistic assessment of percentage of overall organ damage from the therapy can be ascertained.

Inclusion Criteria:

• Patients consented, eligible, and scheduled to be treated on the phase II study of extracranial stereotactic radioablation (a.k.a stereotactic body radiotherapy) for early stage lung cancer already approved at Indiana University

Exclusion Criteria:

• Patients with contraindications to functional imaging (e.g. allergy to agent used in studies) and patient unwilling to fulfill requirements of both protocols are ineligible