Dual-energy CT (DECT) provides information on the blood volume in tumors and lymph nodes. As tumors respond to treatment, preliminary data suggests that the blood volumes changes as well. Investigators are therefore using DECT to test whether it can be used on radiation treatment to rapidly assess response to treatment.

Inclusion Criteria:

• Patients aged greater than 18 years with a diagnosis of stage III non-small cell lung cancer.
• Planned treatment with either definitive chemoradiotherapy or preoperative chemoradiotherapy followed by surgical resection.
• PET-CT study within 4 weeks of next available DECT study.
• Patients must have measurable primary and nodal disease, defined by at least one lesion (primary and lymph node) greater than 1 cm.
• Kidney function sufficient to tolerate iodine-based CT contrast.
• No allergy to iodine-based contrast.
• Ability to understand and the willingness to sign informed consent.

Exclusion Criteria:

• Participants with a prior history of thoracic radiotherapy.
• Participants may not be receiving any other study agents.
• Inability to tolerate CT contrast
• Pregnant women are excluded from this study because radiotherapy has the potential for teratogenic or abortifacient effects. Because there is an unknown but potential risk of adverse events in nursing infants secondary to treatment of the mother with radiotherapy, breastfeeding should be discontinued if the mother is treated with radiotherapy. These potential risks may also apply to other agents used in this study.

Patients with stage III lung cancer treated with chemoradiotherapy or chemoradiotherapy followed by surgery