Correspondence re: Schoen et al., Lack of Association between Adipose Tissue Distribution, and Insulin-like Growth Factor-I and Insulin-like Growth Factor Binding Protein-3 in Men and Women. Cancer Epidemiol. Biomark. Prev., 11: 581–586, 2002

We commend Schoen et al. (1) on their well-conducted study, in which the authors conclude there is no association between adiposity and either IGF-I¹ or IGF binding protein-3, although there was a strong correlation between visceral adipose tissue and insulin level. It has been suggested recently that the relationship between adiposity and IGF-I may be an inverted U, i.e., nonlinear (2). Inspection of Table 3 in Schoen et al. (1) suggests that visceral adipose tissue and some of the IGF-related measures have an inverted U-shaped relationship. If this were so, it is not surprising that both the correlation coefficients and the trend tests were not statistically significant, because both tests assume a monotonically increasing or decreasing trend. Given the increasing attention to the role of the IGF family in cancer etiology (3), it would be informative to know whether this purported inverted U-shaped relationship exists in the Schoen et al. (1) study population. Understanding how adiposity and its characteristics influence the levels of the IGF family members provides much needed insight regarding potentially modifiable cancer risk factors.