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Abstract
BACKGROUND:
The prognostic impact of preoperative 18F-FDG PET/CT in advanced gastric cancer (AGC) remains a matter of debate. This study aims to evaluate the prognostic impact of SUVmax in preoperative 18F-FDG PET/CT of AGC according to histologic subtype, with a focus on the differences between tubular adenocarcinoma and signet ring cell (SRC) carcinoma.

METHODS:
As a discovery set, a total of 727 AGC patients from prospective database were analyzed according to histologic subtype with Cox proportional hazard model and p-spline curves. In addition, another 173 patients from an independent institution was assessed as an external validation set.

RESULTS:
In multivariate analysis, high SUVmax in preoperative 18F-FDG PET/CT of AGC was negatively correlated with disease-free survival (DFS) and overall survival (OS) in patients with diffuse type (DFS: HR 2.17, P < 0.001; OS: HR 2.47, P < 0.001) or SRC histology (DFS: HR 2.26, P = 0.005; OS: HR 2.61, P = 0.003). This negative prognostic impact was not observed in patients with intestinal type or well or moderately differentiated histology. These findings have been consistently confirmed in a validation set. The p-spline curves also showed a gradual increase in log HR as SUVmax rises only for SRC histology and for diffuse-type AGC. Finally, a novel predictive model for recurrence of AGC with diffuse type or SRC histology was generated and validated based on the preoperative SUVmax.

CONCLUSIONS:
Preoperative high SUVmax of AGC is a poor prognostic factor in those with diffuse type or SRC histology. This study is the first to demonstrate the differential prognostic impact of preoperative PET/CT SUVmax in AGC according to histologic subtype and provide a clue to explain previous discrepancies in the prognostic impact of preoperative PET/CT in AGC. Prospective studies are required to validate the role of preoperative SUVmax in AGC.

Author information

Chon HJ1,2, Kim C1, Cho A3, Kim YM4, Jang SJ5, Kim BO6, Park CH7, Hyung WJ8, Ahn JB9, Noh SH8, Yun M10, Rha SY11.
1
Medical Oncology, CHA Bundang Medical Center, CHA University, Seongnam, South Korea.
2
Yonsei Graduate School, Yonsei University College of Medicine, Seoul, South Korea.
3
Department of Nuclear Medicine, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-ku, Seoul, 120-752, South Korea.
4
Department of Surgery, CHA Bundang Medical Center, CHA University, Seongnam, South Korea.
5
Department of Nuclear Medicine, CHA Bundang Medical Center, CHA University, Seongnam, South Korea.
6
Biostatistics Collaboration Unit, Department of Research Affairs, Yonsei University College of Medicine, Seoul, South Korea.
7
Department of Internal Medicine, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, South Korea.
8
Department of Surgery, Yonsei University College of Medicine, Seoul, South Korea.
9
Department of Internal Medicine, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-ku, Seoul, 120-752, South Korea.
10
Department of Nuclear Medicine, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-ku, Seoul, 120-752, South Korea. yunmijin@yuhs.ac.
11
Department of Internal Medicine, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-ku, Seoul, 120-752, South Korea. rha7655@yuhs.ac.