They conducted a non-concurrent, long-term, follow-up study in 71 patients who were diagnosed endoscopically as having EGC, confirmed as cancer on biopsy, but in whom surgical resection was not conducted or was delayed by more than six months.
In observing the natural course of EGC in 56 cases, the team found that over a period of 6-137 months, 20 remained in the early stage while 36 progressed to the advanced stage. The proportion remaining in the early stage consistently decreased with time.
The median duration of those who remained in the early stage was estimated as 44 months. The cumulative five-year risk for progressing to the advanced stage was 63%.
38 patients did not undergo surgical resection for gastric cancer. The cumulative five-year corrected survival was estimated as 62.8% among those who were unresected.
Hazard ratio for gastric cancer mortality was 0.51, more for those not having surgery.
The hazard-rate ratio for gastric cancer mortality was 0.65 (P = 0.34) for EGC detected by screening, vs. non-screening detected. The hazard-rate ratio for gastric cancer mortality was 0.51, significantly lower for patients whose operations were delayed, compared with those who never had a resection.
In concluding on behalf of the team, Dr Tsukuma stated, "Although EGC showed a relatively long natural history in general, it progressed to the advanced stage with time and led to death from gastric cancer for the most part if left untreated."