Radiation and breast cancer: a review of current evidence

This paper summarizes current knowledge on ionizing radiation-associated breast cancer in the context of established breast cancer risk factors, the radiation dose–response relationship, and modifiers of dose response, taking into account epidemiological studies and animal experiments. Available epidemiological data support a linear dose–response relationship down to doses as low as about 100 mSv. However, the magnitude of risk per unit dose depends strongly on when radiation exposure occurs: exposure before the age of 20 years carries the greatest risk. Other characteristics that may influence the magnitude of dose-specific risk include attained age (that is, age at observation for risk), age at first full-term birth, parity, and possibly a history of benign breast disease, exposure to radiation while pregnant, and genetic factors

Risk factors for breast cancer among Filipino women in Manila.

Age-adjusted incidence rates of breast cancer vary greatly worldwide with highest rates found in the typically 'westernised' countries of North America and Europe. Much lower rates are observed in Asian and African populations but an exception to this has been reported for the Manila Cancer Registry in the Philippines. The reason for this high rate is unknown but may be associated with the change in lifestyle that has occurred in urban Manila since the 1960s. In 1995, a randomised controlled trial was set up in Manila to evaluate the feasibility of a screening intervention by clinical breast examination as an alternative to mammography. The cohort of 151,168 women was followed-up to 2001 for cancer incidence and a nested case-control study carried out. This aimed to evaluate the increase in breast cancer risk associated with known risk factors. Increased risks were seen for a high level of education (OR = 1.9 95%CI 1.1-3.3 for education stopped at > or =13 versus or =30 versus <20 years). We found no association with excess body weight, height, use of exogenous hormones or alcohol consumption. From this study, the recognised "classical" risk factors do not fully explain the high breast cancer incidence in Metro Manila, especially when compared to other urban Asian populations. We conclude that it is too simplistic to ascribe the high risk to 'westernisation'