This study determined the association of blood and dietary vitamin C levels with the risk of stomach cancer.
Data from 215 cancer patients were compared with data from 416 participants without cancer.
The results showed that high blood levels of vitamin C were associated with a reduced risk of stomach cancer.

Further details can be found in the study.

Plasma and dietary vitamin C levels and risk of gastric cancer in the European Prospective Investigation intoCancer and Nutrition (EPIC-EURGAST).
Carcinogenesis. 2006 Nov;27(11):2250-7. Epub 2006 Jun 14.