Natural History of Gastric Cancer: Observational Study of Gastric Cancer Patients Not Treated During Follow-Up

Understanding the natural progression of untreated gastric cancer is critical for determining the disease prognosis as well as treatment options and timing. The aim of this study is to analyze the natural history of gastric cancer. We included patients with gastric cancer who had not received any treatment and were staged using endoscopy/endoscopic ultrasonography and computed tomography on at least two follow-up visits during intervals of nontreatment. Tumor volumes were also measured in addition to the staging. Survival of each stage at diagnosis was also analyzed. A total of 101 patients were included. The mean follow-up period was 35.1 ± 34.4 months. The gastric cancer doubling time was 11.8 months for T1 and 6.2 months for T4. The progression time from early gastric cancer to advanced gastric cancer was 34 months. It decreased as the stages advanced: from 34 months between tumor-nodes-metastasis stage I and II to 1.8 months between stage III and IV. No variable was identified as a risk factor for cancer progression. The 5-year survival rates of untreated patients were 46.2% in stage I and 0% in stage II, stage III, and stage IV. The progression and doubling times of gastric cancer shorten as the stages advance. Objective data reported in this study can be a critical factor in determining treatment timing and screening interval.