# Efficacy of 18F‐Fluoro‐2‐Deoxyglucose Positron Emission Tomography as a Predictor of Treatment Response to Neoadjuvant S‐1 + Oxaliplatin Chemotherapy for Gastric Cancer

## TL;DR

This study shows that FDG-PET scans can predict how well gastric cancer patients respond to a specific chemotherapy treatment before surgery.

## Contribution

The study identifies optimal SUVmax reduction thresholds for predicting treatment response in gastric cancer patients undergoing SOX chemotherapy.

## Key findings

- SUVmax decreased significantly after chemotherapy, especially in higher-grade tumors.
- A 53% ΔSUVmax cut-off predicted Grade 1b or higher response, and 75% for Grade 2 or higher.
- Patients with ΔSUVmax >50% had better recurrence-free survival.

## Abstract

Neoadjuvant chemotherapy is widely recognized as the established treatment for advanced gastric cancer. However, predicting its efficacy before surgery remains challenging.

The present study aimed to evaluate the effectiveness of 18F‐fluoro‐2‐deoxyglucose positron emission tomography (FDG‐PET) as a predictor of treatment response to the S‐1+Oxaliplatin regimen (SOX).

Thirty patients who underwent gastrectomy following neoadjuvant SOX between January 2021 and July 2023 were included. Patients underwent FDG‐PET pre‐ and postsurgery. The maximum standardized uptake value (SUVmax) from FDG‐PET was examined in relation to histological tumor response and prognosis. SUVmax decreased significantly after chemotherapy in all patients (p < 0.001), especially in those with Grade 1a, 2, and 3 tumors (p < 0.05). SUV reduction increased stepwise with the histological response grade. Optimal cut‐off values for the percentage decrease in SUVmax (ΔSUVmax) predictive of histologic efficacy were identified as 53% (area under curve 0.855, p = 0.0018) for Grade 1b or higher and 75% (area under curve 0.806, p = 0.0044) for Grade 2 or higher. Patients with ΔSUVmax > 50% had improved recurrence‐free survival (p = 0.027).

FDG‐PET may be useful as a predictor of treatment response in neoadjuvant SOX therapy for gastric cancer. The determination of the optimal ΔSUVmax value may enhance the precision of histological tumor response prediction.