Purpose: Few studies have evaluated metabolic activity by (18)F-FDG PET as a prognostic factor in advanced gastric cancer (AGC). We investigated its prognostic role in metastatic AGC.
Methods: We enrolled 82 patients with metastatic AGC, who were treatment-naive and underwent pretreatment (18)F-FDG PET/CT scanning. In each patient, the maximal standardized uptake value (SUVmax) was measured in each target lesion. Stomach(SUVmax) was defined as SUVmax in the stomach, while Total(SUVmax) was defined as the highest SUVmax among all the target lesions.
Results: The stomach was the organ most frequently displaying the highest SUVmax among all the target lesions (in 67.1% of patients). A Total(SUVmax) value of 11.5 was the value with the maximum sum of sensitivity and specificity from receiver-operating characteristic curves for progression-free survival (PFS). PFS was significantly longer in patients with a Total(SUVmax) value <11.5 than in those with a Total(SUVmax) value ≥11.5 (P = 0.023); however, overall survival (OS) was not (P = 0.055). A Stomach(SUVmax) value of 6.0 was derived by similar methods. PFS and OS were significantly longer in those with a Stomach(SUVmax) value <6.0 than in those with a Stomach(SUVmax) value ≥6.0 (P = 0.001 and P = 0.006, respectively). Furthermore, those with a low Total(SUVmax) and those with a low Stomach(SUVmax) showed better chemotherapeutic responses (P = 0.016 and P = 0.034, respectively). Among patients with histologically undifferentiated carcinomas, those with lower Total(SUVmax) and those with lower Stomach(SUVmax) showed longer median PFS (P = 0.027 and P = 0.005, respectively) and OS (P = 0.009 and P <0.001, respectively). Multivariate analysis demonstrated Stomach(SUVmax) as an independent predictor of PFS (P = 0.002) and OS (P = 0.038).
Conclusion: Pretreatment metabolic activity may be a useful prognostic marker in patients with metastatic AGC undergoing palliative chemotherapy. Notably, Stomach(SUVmax) was the single, most robust factor predicting prognosis.