[Secondary malignancies after gastrectomy for gastric cancer]

In patients who have undergone gastrectomy for gastric cancer, the use of adjuvant chemotherapy has now become very widespread in Japan. The possibility of secondary malignancies in these patients emerges as a long-term effect of these therapeutic agents. This collaborative study was done to examine the possibility of secondary malignancies resulting from both operative methods and anticancer agents at the surgical departments of seven major institutions in Japan. The study was carried out using questionnaires for all patients with gastric cancer who had undergone gastrectomy between 1960 and 1975 in those hospitals and who had survived more than one year after gastrectomy. A total of 235 secondary malignancies (2.32%) were noted among 10,138 gastrectomized patients, and 22 cancers of the gastric remnant (0.29%) were recorded among 7,672 subtotal gastrectomized cases. Cancers suspected to be recurrent gastric cancer were all excluded. As to anticancer agents, Mitomycin C (MMC), 5-Fluorouracil (5-FU) or Tegafur and Cyclophosphamide (EDX) were analyzed. The occurrence rate of secondary cancers in gastric cancer patients was calculated in many instances by dividing the actual number of secondary cancers by the total time at risk (person-years). Patients with gastric cancer who had undergone gastric resection revealed a lower incidence of secondary malignancies than had been expected. The most common secondary cancers were those occurring in the digestive system, followed by those of the respiratory system. With regard to MMC, 67 secondary cancers (2.21%) occurred in the MMC group and 168 cancers (2.36%) in the non-MMC group. Although the overall incidence of secondary cancers showed no difference between MMC and non-MMC groups, secondary cancers of the digestive system were less common in the MMC group than in the non-MMC group. A total of 22 cancers originated in the gastric remnant out of 7,672 subtotally resected stomachs. The interval between the first operation and cancer of the gastric remnant varied greatly without showing any detectable trend. Nine cancers were observed to involve the anastomotic site while 14 did not involve the anastomotic site. The incidence of cancer of the gastric remnant tended to be slightly higher with the Billroth II method than in the Billroth I method, but there was no difference in the site of secondary malignancy between the two groups.