Serial [18F]Thymidine (FLT)PET/CT as a Biomarker of Response in Pemetrexed Therapy for Non-Small Cell Lung Cancer

Inclusion Criteria: 1. Adult patients, at least 18 years of age 2. Histologically confirmed non-small cell lung cancer with at least one site of disease \> 1 cm by at least one type of standard imaging (e.g. CT, chest x-ray, MRI) 3. Recommended to start systemic therapy which includes pemetrexed and a platinum-based agent. 4. Participants must be informed of the investigational nature of this study and provide written informed consent in accordance with institutional and federal guidelines prior to study-specific procedures. 5. Participants must be willing and able to comply with scheduled visits and imaging procedures in the opinion of the investigator or treating physician. Exclusion Criteria: 1. Females who are pregnant or breast-feeding at the time of screening will not be eligible for this study. Female participants of child-bearing potential will have a urine pregnancy test at the time of the screening visit. 2. Patients with only a single site of primary lung cancer who have undergone or are recommended to undergo radiation therapy to that site will not be eligible, the inclusion of patients who may be undergoing radiation therapy to ancillary disease sites may be allowed to enter the study at the discretion of the PI if it is not felt to affect the ability to capture FLT information for at least one primary site of disease. 3. Patients who have received chemotherapy within 2 weeks of enrollment will be excluded from the study. 4. Patients who have undergone cancer surgery removing a significant portion of active disease, in the opinion of an investigator, within 2 months prior to study enrollment will be excluded. 5. Inability to tolerate imaging procedures in the opinion of the investigator or treating physician 6. Serious or unstable medical or psychological conditions that, in the opinion of the investigator would compromise the subject's safety or successful participation in the study. 7. Unwilling or unable to provide informed consent