20-Year Comparative Survival and Mortality of Cancer of the Stomach by Age, Sex, Race, Stage, Grade, Cohort Entry Time-Period, Disease Duration & Selected ICD-O-3 Oncologic Phenotypes: A Systematic Review of 157,258 Cases for Diagnosis Years 1973-2014: (SEER*Stat 8.3.4)

Background and Importance.—Globally, almost one million new cases of stomach cancer were estimated to have occurred in 2012 (952,000 cases, 6.8% of the total), making it the fifth most common malignancy in the world, after lung, breast, colorectal, and prostate. Gastric cancer was the world's third leading cause of cancer mortality in 2012, responsible for 723,000 deaths, 8.8% of total cancer deaths.1 In 2017, 28,000 new cases and 10,960 deaths are estimated for gastric cancer in the United States.2 Estimated United States prevalence counts on January 1, 2014, for patients diagnosed within the previous 5-years was 48,271 (SEER Cancer Statistics Review-2014). Prognostic indices of survival & mortality in patients with gastric cancer are related to tumor stage including nodal involvement, direct tumor extension beyond the gastric wall, and wide-spread dissemination. Tumor histologic grade (degree of loss of cellular differentiation), and oncotype-specific ICD-O-3 phenotypes also provides important prognostic information. By more than 90%, the most common histologic type of stomach cancer is adenocarcinoma. The National Cancer Institute (NCI) ICD-O-3 SEER Site/Histology Validation List catalog (September 18, 2015) enumerates almost 200 subtypes for gastric cancer sites C160-C166, C168-C169. Based on the results of molecular evaluation of 295 primary gastric adenocarcinomas reported to The Cancer Genome Atlas (TCGA) project in 2014, a novel classification separating gastric cancers into four subtypes according to Epstein-Barr virus positive status, microsatellite instability, chromosomal instability, or genomic stability was proposed.3 Of interest, Helicobacter Pylori infection and its role in the development of gastric cancer is not mentioned. All cancer has a genetic basis. However, given the histologic and etiologic heterogeneity of gastric cancer, eventual comprehensive molecular characterization and genomic sequencing with identification of chromosomal aberrations, nucleotide substitutions mortality follow-up study is focused on short- and long-term comparative patient outcomes of stomach adenocarcinoma, ICD-O-3 8140-8147, and other selected gastric cancer oncotypes. Objective.—To update trends in incidence, prevalence, short- and long-term survival, and mortality of gastric cancer using the statistical database of SEER*Stat 8.3.4 for diagnosis years 1973-2014 employing multiple case selection variables. Methods.—A retrospective, population-based study using nationally representative data from the National Cancer Institute's (NCI) Surveillance, Epidemiology, and End Results (SEER) program to evaluate 157,258 cases for diagnosis years 1973-2014 comparing multiple variables of age, sex, race, stage, grade, cohort entry time-period, disease duration and histologic oncotype: Relative survival statistics were analyzed in two cohorts: 1973-1994 and 1995-2014. Survival statistics were derived from: SEER*Stat Database: Incidence – SEER 9 Regs Research Data, November 2016 Submission (1973-2014) <Katrina/Rita Population Adjustment> Released April 2017. Results.—By more than 90%, the most common type of stomach cancer is adenocarcinoma. From 1975 to 2014, gastric cancer incidence has been steadily decreasing in the United States at the rate of −1.5% per year. In a total of 157,258 cases of invasive staged cancer of the stomach, mean age in males was 67.5 years, females 69.6 years, both male & female 67.4 years. Greater than 90% of cases occurred between ages 45-85+ years with the zenith in males at 70-74 years (15.1%) and 85+ years in females (17.9%). The overall annual US death rate per 100,000 per year for stomach cancer from 1975 to 2014 has decreased from 5.1 to 3.1, but excess mortality at 0-5 years remains exceedingly high. Mortality is a function of incidence and survival, and unfortunately, almost all of this decrease is due to the decrease in incidence of stomach cancer. Of the 157,258 invasive cases, 86.6% were clinically staged and 76.8% were histologically graded. Conclusions.—Given the histologic and etiologic heterogeneity of gastric cancer, major improvements in mortality and survival outcomes await the development of diagnostic markers for earlier diagnosis, and genomic sequencing and identification of chromosomal aberrations, nucleotide substitutions and epigenetic modifications that drive malignant transformation, for the development of targeted therapies for almost 200 gastric cancer subtypes.