Alcohol Drinking, Smoking, Past History of Gastroduodenal Ulcer, Height, and Risk of API2-MALT1 Fusion Positive and Negative Gastric MALT Lymphoma Among Japanese.

Abstract Abstract 5010 Extranodal marginal zone B-cell lymphoma of mucosaassociated lymphoid tissue (MALT Lymphoma) is low-grade extranodal lymphoma, and it comprises 7-8% of all B cell lymphomas, and up to 50% of primary gastric lymphoma. It is known that a preexisting chronic inflammation such as Helicobactoer pylori (H. pylori) gastritis can influence its development, however, some MALT lymphomas with no evidence of such inflammation are found. Protracted remissions may be induced by H. pylori eradication therapy, but cases with t(11;18)(q21;q21) appear to be resistant to the therapy. t(11;18)(q21;q21) has been observed in 25-50% of the cases and API2 at 11q21 and MALT1 at 18q21 are fused as a result of this translocation. Thus, API2-MALT1 fusion positive and negative MALT lymphoma may have different etiology, although histological features of both MALT lymphomas have not been clearly delineated. To clarify differences of epidemiological features between API2-MALT1 fusion positive and negative gastric MALT lymphoma, we conducted a case-control study of 61 newly and histologically diagnosed gastric MALT lymphoma cases (14 of API2-MALT1 fusion positive cases and 47 of negative cases) and 610 age and sex frequency-matched non-cancer controls. API2-MALT1 fusion was evaluated by a multiplex reverse transcription-polymerase chain reaction using formalin-fixed, paraffinembedded sections. We evaluated the association with alcohol intake (never drinkers, occasional drinkers, and frequent but moderate (<50 g/day of alcohol) and frequent and heavy drinkers (≥50 g/day of alcohol)), smoking (<5, 5-19, 20-39, ≥40 pack-years), past history of gastroduodenal ulcer, height, and risk of API2-MALT1 fusion positive and negative gastric MALT lymphoma. Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated using multinomial logistic models adjusted for potential confounders. A significant association was observed between past history of gastroduodenal ulcer and the risk only among fusion negative cases, with ORs of subjects with past history of gastroduodenal ulcer of 2.86 (95% CI, 1.31-6.14; p = 0.008) compared to subjects without past history of gastroduodenal ulcer. No clear associations were observed between alcohol intake, smoking, height and the risk irrespective of positivity of API2-MALT1 fusion. These findings suggest that past history of gastroduodenal ulcer, which may be due to H.pylori infection, does not associated with the carcinogenic mechanism of API2-MALT1 fusion positive gastric MALT lymphoma, and fusion positive and negative tumors have different etiology. Further investigations using large data sets are needed. Disclosures No relevant conflicts of interest to declare.