Cancer occurrence rates in a period of time for a given population is expressed in various ways. The incidence rate is a direct measure of the probability of developing cancer and is usually expressed per year. Incidence rates may be crude (all ages) or age specific. Since cancer is very age dependent, age specific rates are usually more informative. Cancer in elderly is more prevalent compare to cancer in younger age. When comparing population groups with different age distributions (such as the United States vs. China), the incidence rate should be age adjusted by multiplying each age-specific rate by the percent of individuals in a population with the same ages and then summing these to produce a single value. For etiological studies, incidence rates tend to be more informative than mortality rates, as they identify all diagnosed cases. (more…)

Cancer is also called malignant neoplasm. This implies that the growth is a new growth (neoplasm) that if unchecked will kill the host (malignant). Normal cells can express some of the preceding properties at certain appropriate times, such as in wound healing, embryogenesis, organ repair and regeneration, and revascularization, but the proliferation is coordinated, orderly, and self-limited. In cancer, however, these characteristics are excessive, disordered, and not self-limited, resulting in an inappropriate proliferation (tumor burden) and spread that is inappropriate to the host and that has morbid implications if not successfully treated. (more…)