Studies examine incidence of gastric cancer, benefits associated with chemotherapy regimens

Gastric cancer is the fourth most common type of cancer and the second most common among cancer deaths worldwide. While tumors of the cardia, the upper part of the stomach adjoining the esophagus, may be related to gastroesophageal reflux, the majority of noncardia gastric cancers are attributable to chronic mucosal infection by the bacterium Helicobacter pylori, according to background information in a study by William R. Anderson, M.D., of the National Cancer Institute, Rockville, Md., and colleagues.

"Overall, gastric cancer incidence has steadily declined in many countries over the past 50 years or longer. However, overall trends may mask important age- specific differences. Furthermore, the overall decline runs counter to the subsite-specific rise in cardia cancers that may be related to obesity and gastroesophageal reflux," the authors write.

The researchers analyzed U.S. population-based age-specific data for noncardia gastric cancer, using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program, which covers approximately 26 percent of the U.S. population. From 1977 through 2006, there were 83,225 adults with new primary gastric cancer, including 39,003 noncardia cases.

The authors found that the overall age-standardized annual incidence per 100,000 population declined during the study period from 5.9 to 4.0 in whites, from 13.7 to 9.5 in blacks, and from 17.8 to 11.7 in other races. "Age-specific trends among whites varied significantly between older and younger age groups: incidence per 100,000 declined significantly from 19.8 to 12.8 for ages 60 to 84 years and from 2.6 to 2.0 for ages 40 to 59 years but increased significantly from 0.27 to 0.45 for ages 25 to 39 years. Conversely, rates for all age groups declined or were stable among blacks and other races. Age-period-cohort analysis confirmed a significant increase in whites among younger cohorts born since 1952."

"Targeting all cancer cases in residents of defined geographic areas, the large-scale SEER database is broadly representative of cancer incidence in the United States as a whole. Further age-specific analyses of noncardia gastric cancer incidence trends for low-risk populations will be informative," the authors conclude.

Chemotherapy After Gastric Cancer Surgery Appears to Provide Survival Benefit

Patients who have gastric cancer surgery followed by chemotherapy have an associated decreased risk of death and improved disease-free survival compared to patients who have surgery alone, according to an analysis of previous studies, reported in the May 5 issue of JAMA.

Gastric cancer is a common and highly fatal disease, with current 5-year survival rates less than 20 percent, according to background information in the article. "Surgery for disease at an early stage can usually be performed with curative intent, but the 5-year survival rate is disappointing. Over the last 3 decades, numerous phase 3 studies including a surgery-only group have been reported, but definitive evidence of the efficacy of adjuvant [after surgery] chemotherapy is lacking," the authors write.

Xavier Paoletti, Ph.D., of the Institut National du Cancer, Boulogne, France, and colleagues with the Global Advanced/Adjuvant Stomach Tumor Research International Collaboration (GASTRIC) Group, assessed the benefit of adjuvant chemotherapy quantitatively through a meta-analysis based on individual patient data from all relevant trials. For this analysis, the researchers identified 31 eligible trials (6,390 patients). As of 2010, individual patient data were available from 17 trials (3,838 patients representing 60 percent of the targeted data) with a median (midpoint) follow-up exceeding 7 years.

There were 1,000 deaths among 1,924 patients assigned to chemotherapy groups and 1,067 deaths among 1,857 patients assigned to surgery-only groups. The researchers found that there was a significant benefit from any chemotherapy compared with surgery alone, with analysis indicating an overall 18 percent reduction in the risk of death with chemotherapy. The estimated median overall survival was 4.9 years in the surgery-only group vs. 7.8 years in the group receiving adjuvant chemotherapy. An absolute improvement of about 6 percent in overall survival was observed after 5 years, and maintained at 10 years. Five-year overall survival increased from 49.6 percent to 55.3 percent with chemotherapy. Adjuvant chemotherapy was also associated with an 18 percent reduction in the risk of relapse, compared with surgery alone.

"In conclusion, this patient-level meta-analysis shows that adjuvant fluorouracil-based chemotherapy, even in monotherapy, is associated with improvement in overall survival and is recommended for patients who have not received perioperative treatments after complete resection of their gastric cancer. Future reports based on data being collected will explore prognostic factors and the surrogacy of disease-free survival for overall survival in this population," the authors write.