Successful vaccination with the therapeutic immunogen G17DT appears beneficial in patients with advanced gastric or gastroesophageal cancer, researchers report in the May 1st issue of Cancer.
As lead investigator Dr. Jaffer A. Ajani told Reuters Health, “I believe that the results are intriguing. Patients who were successfully immunized seemed to have a higher response rate and longer survival.”Dr. Ajani of the University of Texas MD Anderson Cancer Center, Houston and colleagues explain that G17DT is a conjugate of the amino-terminal sequence of gastrin 17 and diphtheria toxoid. The agent elicits a specific and high-affinity antigastrin antibody response that is antiproliferative and antimetastatic.To investigate the effect of G17DT, the researchers conducted an open-label study of untreated patients with gastric adenocarcinoma who were vaccinated intramuscularly on weeks 1, 5, 9 and 25. They were also given cisplatin and 5-fluorouracil every 28 days.In total, 79 patients were evaluated for overall response and 94 were evaluated for immune response. The overall response rate was 30% and 69% were deemed to be successful immune responders. The median time to progression was 5.4 months.The time to progression was significantly longer in immune responders than non-responders. This was also true of median survival – 10.3 months versus 3.8 months.Successful vaccination was a significant independent overall survival prognosticator and was independent of other clinical factors. G17DT did not have an adverse effect on safety.Thus, added Dr. Ajani, the “immunization effort needs to improve – with a more aggressive vaccination strategy.”Overall, the researchers conclude, “A phase III investigation of G17DT is warranted to delineate its true contribution to patient survival.” (Source: Cancer 2006;106:1908-1916: Reuters Health: Oncolink: May 2006.)