Surgical/pathologic-stage migration confounds comparisons of gastric cancer survival rates between Japan and Western countries.

Abstract

PURPOSEPossible causes underlying the substantial differences in gastric cancer survival rates observed between Japan and the West were examined in a randomized trial comparing the Western R1 resection with limited lymphadenectomy and the Japanese R2 resection with extended lymphadenectomy.PATIENTS AND METHODSThe effect of four factors associated with lymphadenectomy on microscopic tumor-node-metastasis (TNM) staging, and on stage-specific survival rates was assessed in 473 curatively resected patients.RESULTSAfter application of extended lymphadenectomy, additional information on N status was available, only in R2 resections with up-staging to N2 status in 30% of patients. The calculated effect of this stage migration on known 5-year survival rates was as follows: an increase of 1% in TNM stage Ia, 2% in Ib, 7% in II, 15% in IIIa, and 15% in IIIb. A further increase in survival was observed by stage migration to N3 or N4 status, due to selective extension of lymphadenectomy to clinically overt metastases...