Racial variations in pancreatic cancer

A20

Introduction: The incidence and/or mortality rates for the major cancers in the US are significantly higher for African Americans (AA) than for Whites. Herein we report a descriptive epidemiologic study on the racial variations seen in the trends, incidence, age specific rates, and survival of pancreatic cancer.
 Methods: Data were obtained from NCI’s Surveillance, Epidemiology, and End Results Program (SEER) for the years 1973-2004. Using SEER Registry 9, there were 8,245 cases of pancreatic cancer in AA and 63,903 in Whites. Cases were compared by linear and by log-log plots of the age of diagnosis and age specific incidence rates. Log-log plots represent a mathematic transformation that provides insight into age dependent tumor development. Similar graphical patterns imply similar mechanisms of transformation or a similar carcinogenic process. The two main histological tumor types of the pancreas -- ductal epithelial carcinomas and neuroendocrine tumors -- were considered. Incidence rates are expressed as number of cases per 100,000 persons. Only invasive tumors were included.
 Summary: Of the two main pancreatic tumor types, ductal epithelial carcinomas that arise in the ducts comprise >97% of all pancreatic carcinomas and neuroendocrine tumors <3%. The incidence rate of pancreatic cancer is significantly higher in AA men (19.1) than in White men (13.2) and significantly higher in AA females (14.8) than in White females (9.7). This higher rate in AA has been consistent for 30 years. Over this period, there has been no significant change in the trend of pancreatic cancer in either racial group. The median age of diagnosis was 68 for AA and 72 for Whites. In every age group, the age specific rate was higher in AA than in Whites. Log-log plots of the age of diagnosis and the age specific incidence rates revealed parallel linear rate patterns for both racial groups. The frequency of neuroendocrine tumors was similar in both racial groups, comprising <3% of all pancreatic cancers. For both groups, the overall 5-year survival rate was only 10%.
 Conclusions: Because ductal epithelial tumors constitute 97% of all reported pancreatic cancers, racial variations apply only to this tumor type. For both genders, AA are more susceptible to pancreatic ductal epithelial cancers than are Whites. This is evident by higher incidence rates spanning 30 years, higher age specific incidence rates in all age groups, and lower median age of diagnosis. Even though AA have higher rates, the parallel rate patterns in log-log plots of age specific rates suggest that the pathogenesis or etiology of pancreatic ductal cancer in AA and in Whites is similar. Survival is very unfavorable in both groups. Reasons for the greater susceptibility of the AA population to pancreatic cancer are unclear. The etiology of pancreatic cancer is unknown. Cigarette smoking has been implicated as the cause in less than 25% of cases.