You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

PURPOSES: The spread of coronavirus disease 2019 (COVID-19) has affected socioeconomic and healthcare systems in many countries. Accordingly, many individuals may have canceled their annual health-check programs, including esophagogastroduodenoscopy, which would have resulted in lower numbers of newly diagnosed patients with gastric cancer in comparison to other times. METHODS: Questionnaires were distributed to 62 hospitals every week from May 2020 to August 2020 (total 744) through mailing lists of the Stomach Cancer Study Group of the Japan Clinical Oncology Group. The number of patients with gastric cancer and hospital systems during the COVID-19 pandemic were surveyed. RESULTS: In total, 74% (551 out of 744) of the questionnaires were answered and analyzed. In early May, approximately 50% of hospitals had to restrict surgical slots due to the COVID-19 pandemic. However, they gradually loosened the restrictions thereafter. The number of gastrectomies was < 80% that of the same period in the previous year, and hospitals in Tokyo were seriously affected by a 50% decrease in the number of gastrectomies. CONCLUSIONS: The number of gastrectomies was lower than that in the previous year. Further multi-center follow-up studies are required to evaluate the long-term effects of COVID-19 on the clinical outcomes of patients with gastric cancer.
["Prevention"]