PURPOSE To evaluate incidence, time trends, geographic distribution, clinicopathologic presentation features, and prognostic factors for survival and relapse in gastrointestinal (GI) non-Hodgkin's lymphomas (NHLs). PATIENTS AND METHODS Over a 9-year period (1983 to 1991), 2,446 new NHL cases were recorded in a Danish population-based NHL registry (Danish Lymphoma Study Group [LYFO]). Of these, 306 (12.5%) were GI NHL (175 gastric, 109 intestinal, and 22 both sites). LYFO registry data were used for incidence rate (IR) assessment, and time-trend and geographic distribution analysis. Relative risk (RR) values for survival and relapse were identified by multivariate analysis. RESULTS The mean annual, age-standardized IRs for gastric and intestinal NHL were 0.71/10(5) and 0.48/10(5) per year, respectively. Age-specific IRs for both localizations showed an exponential increase as a function of age. Time-trend analysis for the period 1983 to 1991 showed stable IRs for both localizations. Intestinal NHL was more frequent in males (male-to-female ratio, 2.0 v 1.3), and had a higher occurrence of disseminated disease, constitutional symptoms, high-grade histology, and T-cell phenotype (10% v 2%). Gastric NHL had more low-grade cases (38% v 19%), and almost all were of the mucosa-associated lymphoid tissue (MALT) type. The cause-specific 5-year survival rate was 63% for gastric NHL and 49% for intestinal NHL. The Musshoff staging system was an excellent discriminator between truly localized (stage I and II1) and disseminated cases (stage II2 to IV), particularly for gastric NHL, for which no survival difference was found between surgically and conservatively stage localized cases. CONCLUSION (1) No increase in the incidence of GI NHL was found over a 9-year observation period; (2) nonrandom spatial distribution of new GI NHL cases was observed; (3) factors that significantly increased the risk of death in gastric cases were presence of B symptoms (RR = 3.3), clinical stage is more than II1 (RR = 3.0), age more than 72 years (RR = 2.4), and elevated serum lactate dehydrogenase (s-LDH) level (RR = 2.0); and factors that increased the risk of death in intestinal cases were presence of B symptoms (RR = 3.2), age more than 58 years (RR = 2.8), and clinical stage more than I (RR = 2.1); (4) factors that significantly increased the risk of relapse in gastric cases were male sex and no radiotherapy in primary treatment; and in intestinal cases were T-cell phenotype and no surgery in primary treatment; (5) surgical staging, as opposed to thorough noninvasive staging, did not improve staging accuracy and final outcome in localized gastric NHL.
