This study evaluates whether a 7-day ketogenic dietary regimen before 2-[18F]FDG PET/CT can improve the diagnostic accuracy of imaging in adults with suspected or histologically confirmed lepidic-predominant lung adenocarcinoma (LPA). LPA frequently shows low glucose metabolism and may yield false-negative FDG PET/CT results. Approximately 30 participants will undergo a tailored ketogenic diet for 7 days before PET/CT. Imaging results will be compared with histopathology and additionally assessed against literature-reported diagnostic performance and a matched retrospective institutional cohort.

Lepidic-predominant lung adenocarcinoma is a subtype of non-small cell lung cancer characterized by relatively low glucose metabolism, which may reduce the sensitivity of standard 2-[18F]FDG PET/CT. Preclinical and translational evidence suggests that a ketogenic diet may enhance tumour FDG uptake in this setting. This prospective proof-of-concept interventional study will enroll approximately 30 adults with CT evidence of a pulmonary nodule suspicious for LPA or histologically confirmed LPA. After informed consent, participants will undergo an initial dietary assessment and receive an individualized ketogenic diet plan. The ketogenic diet will be followed for 7 days prior to FDG PET/CT. On the day of imaging, participants will undergo a second dietary evaluation, laboratory testing, urinalysis, and PET/CT. PET/CT images will be reviewed independently by two board-certified nuclear medicine physicians. Diagnostic performance will be assessed using visual and semiquantitative PET parameters, with histopathological diagnosis as the reference standard. Study-level results will also be compared with values reported in the literature and with a matched retrospective cohort from the same institution.

Inclusion Criteria:

• Written informed consent.
• Age 18 years or older.
• CT evidence of a lung nodule suspicious for LPA or lung biopsy positive for LPA.
• Target nodule diameter at least 10 mm.
• ECOG performance status 0 to 2.
• Willingness and ability to adhere to a controlled ketogenic diet for 7 days.
• Ability to comply with study procedures and visit schedule.

Exclusion Criteria:

• Not suitable for prolonged imaging procedures.
• Renal failure.
• Type 1 diabetes mellitus.
• Pancreatitis.
• Severe dyslipidemia.
• Other malignancies that are progressing or required active treatment within the previous 3 years.
• Serious or unstable medical, psychiatric, or substance use disorders that could interfere with study participation.
• Pregnancy or breastfeeding.
• Refusal to participate

This is a single-arm, open-label study. However, PET/CT images will be independently reviewed by two board-certified nuclear medicine physicians using blinded image assessment.