RT Book, Section A1 Harrington, Lea A. A1 Cescon, David W. A1 Hill, Richard P. A1 Tannock, Ian F. A2 Harrington, Lea A. A2 Tannock, Ian F. A2 Hill, Richard P. A2 Cescon, David W. SR Print(0) ID 1179323074 T1 Introduction to Cancer Biology T2 The Basic Science of Oncology, 6e YR 2021 FD 2021 PB McGraw-Hill Education PP New York, NY SN 9781259862076 LK accessbiomedicalscience.mhmedical.com/content.aspx?aid=1179323074 RD 2024/03/29 AB It is recognized increasingly that cancer is a genetic disease that occurs because of mutations in critical (driver) genes and that the development of a cancer, especially in adults, is often a long process taking many years. Epidemiologic studies have identified many environmental factors that can cause mutations and are carcinogenic. When Sir Percival Pott carried out his epidemiologic study in 1775, suggesting that the causative agent of scrotal cancer in young chimney sweeps might be chimney soot (now known to be tar), he not only identified the putative carcinogenic agent but also demonstrated that a cancer may develop years after exposure. Another dramatic example is mesothelioma, which is a rare cancer arising from the pleural membranes around the lungs, that develops decades after exposure to asbestos (Lemen, 2016). Epidemiologic studies have also identified tobacco smoke as a major environmental cause of several types of cancer: Doll and Hill (1950) showed that heavy smokers over the age of 50 have a 1 in 2 chance of dying from a smoking-related disease such as lung cancer. On the positive side, individuals who quit smoking at an early age exhibit a gradual return to a near-normal risk of lung cancer (Doll et al, 2004). More recently, obesity (which is increasingly a health concern throughout the world) has been associated with increased risk of certain types of cancer (eg, breast, colorectal), and reducing weight is associated with a lower cancer risk (Iyengar et al, 2015; Hopkins et al, 2016). These and other studies underscore the possibility that, with some types of cancer, a degree of prevention may be achieved via changes in lifestyle.