The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Health Risks from Exposure to Low Levels of Ionizing Radiation: Beir VII Phase 2
nonfatal cancers and of more accurate diagnostic information with data on histological types of cancer. Results based on analyses by the committee of updated incidence data (1958–1997) are discussed in Chapter 12.
Thompson and colleagues evaluated cancer incidence data from 1958 to 1987 for the cancer sites shown in Figure 6-4 and Table 6-2. For each site, they evaluated whether there was a significant association with dose, whether there were departures from linearity, and whether risks were modified by city, sex, age at exposure, attained age, or time since exposure.
Of the cancer sites shown in Figure 6-4 and Table 6-2, the largest ERR/Sv was for breast cancer. Relatively large values were also seen for nonmelanoma skin cancer and for cancers of the ovary, urinary bladder, and thyroid. In addition to these sites, the 95% confidence intervals excluded zero for cancers of the stomach, colon, liver, and lung. It should be noted that the size of the ERR/Sv may be affected by the size of the baseline risk. These ERRs/Sv were obtained from a model with no modifying factors and are not strictly comparable to those based on mortality data and shown in Figure 6-3, which included modifying factors and were intended to be applicable to a person exposed at age 30 at attained age 70.
FIGURE 6-4 Excess relative risk at 1.0 Sv (RBE 10) for solid cancer incidence and 95% confidence interval, 1958–1987. SOURCE: Reproduced with permission from Thompson and others (1994).
In addition to analyses by Thompson and colleagues (1994), several papers provide further analyses that, in some cases, give more attention to histological type and, in other cases, are based on case-control studies that include data on possible modifying factors that were not available for the full cohort. These results are summarized below for selected cancer sites.
Female Breast Cancer
In a case-control interview study nested within the LSS cohort and including cases occurring in 1950–1985, Land and colleagues (1994b) investigated known risk factors for breast cancer: age at the time of a first full-term pregnancy, number of children, and cumulative period of breast-feeding. The influence of these factors on breast cancer risks in women in the LSS cohort was similar to that found in other studies. The relationship of these factors and radiation exposure was reasonably well described by a multiplicative model (in which known risk factors for breast cancer do not modify the ERR/Sv), whereas an additive model could be rejected.
Preston and colleagues (2002a) conducted pooled analyses of breast cancer incidence in eight cohorts. Analyses from this paper based on the LSS cohort alone that included cases