Influence of Baseline Positron Emission Tomography in Metastatic Gastroesophageal Cancer on Survival and Response to Therapy

Background: The value of baseline fluorodeoxyglucose-positron emission tomography-computed tomography (PET-CT) remains uncertain once gastroesophageal cancer is metastatic. We hypothesized that assessment of detailed PET-CT parameters (maximum standardized uptake value [SUVmax] and/or total lesion glycolysis [TLG]), and the extent of metastatic burden could aid prediction of probability of response or prognosticate. Methods: We retrospectively analyzed treatment-naive patients with stage 4 gastroesophageal cancer (December 2002-August 2017) who had initial PET-CT for cancer staging at MD Anderson Cancer Center. SUVmax and TLG were compared with treatment outcomes for the full cohort and subgroups based on metastatic burden (<= 2 or >2 metastatic sites). Results: We identified 129 patients with metastatic gastroesophageal cancer who underwent PET-CT before first-line therapy. The median follow-up time was 61 months. The median overall survival (OS) was 18.5 months; the first progression-free survival (PFS) was 5.5 months. SUVmax or TLG of the primary tumor or of all metastases combined had no influence on OS or PFS, whether the number of metastases was <= 2 or >2. Overall response rates (ORRs) to first-line therapy were 48% and 45% for patients with <= 2 and >2 metastases, respectively (nonsignificant). ORR did not differ based on low or high values of SUVmax or TLG. Conclusions: This is the first assessment of a unique set of PET-CT data and its association with outcomes in metastatic gastroesophageal cancer. In our large cohort of patients, detailed analyses of PET-CT (by SUVmax and/or TLG) did not discriminate any parameters examined. Thus, baseline PET-CT in untreated metastatic gastroesophageal cancer patients has limited or no utility.