A proposed staging system for primary gastric lymphoma.

Background: Although primary gastric lymphoma is the most common extranodal lymphoma, no specific staging system exists.

Methods: The authors reviewed 98 cases histologically classified according to the Working Formulation, including low grade B-cell lymphoma of mucosa-associated lymphoid tissue type. Survival rates were calculated by the Kaplan-Meier method according to T, N, and M of the general rules of the International Union Against Cancer TNM system. The definitions of these categories are as follows: T1, tumor invades the lamina propria or submucosa; T2, the muscularis propria; T3, the subserosa; T4, the serosa without invasion of adjacent structures; T5, adjacent structures; N0, no regional lymph node metastasis; N1, perigastric lymph nodes within 3 cm of the edge of the primary tumor; N2, perigastric lymph nodes more than 3 cm from the edge of the primary tumor or in lymph nodes along the left gastric, common hepatic, splenic, or celiac arteries; N3, paraaortic and hepatoduodenal lymph nodes and/or other intraabdominal lymph nodes; N4, beyond N3; M0, no distant metastasis; and M1, positive.

Results: The overall 5-year survival rate was 83.5%; it was 100% in T1, 82.4% in T2, 84.2% in T3, 52.9% in T4, and 33.3% in T5; 93.9% in N0, 90.5% in N1, 66.2% in N2, and 44.4% in N3/N4; and 86.0% in M0 and 25.0% in M1. Based on these results, the authors proposed a new staging system as follows: Stage I, T1/N0, N1/M0; Stage II, T1/N2/M0, T2,T3/N0,N1,N2/M0; Stage III, T4,T5/any N/M0, any T/N3, N4/M0; and Stage IV, any T/any N/M1. According to this system, the 5-year survival rate significantly decreased as the stage progressed: 100% in Stage I, 88.9% in Stage II, 52.1% in Stage III, and 25.0% in Stage IV. In Stages I and II, survival rates were not significantly different whether chemotherapy was done or not, whereas in Stage III all patients treated with surgery alone died.

Conclusions: This staging system is useful for assessing prognosis of and deciding a therapeutic plan for primary gastric lymphoma.