An epidemiologic study of cancer deaths recorded in the last half of the 20th century is conducted. The number of deaths for one particular cancer had increased markedly in developed nations. More than 30% of cancer deaths in men, and more than 24% of cancer deaths in women, were caused by this neoplasm in 1998. In some nations, prevention strategies reduced deaths from this cancer. Which of the following neoplasms was most likely identified by this study?