UC San Diego

Background

The insulin-like growth factor-I (IGFI) receptor is a potential target for breast cancer treatment and may be influenced by dietary intake.

Methods

Nested, case-control study of 265 postmenopausal breast cancer survivors; primary breast cancer tissue was stained to determine IGFI receptor status. Change in carbohydrate intake from baseline to year 1 of study was estimated from 24-hour dietary recalls. Breast cancer recurrence cases (91) were matched to two controls (n = 174) on disease and study characteristics and counter matched on change in carbohydrate intake. Weighted conditional logistic regression models fit the risk of recurrence on IGFI receptor status and dietary change.

Results

Half of the tumors were IGFI receptor positive. Increased risk of recurrence was associated with IGFI receptor-positive status [HR 1.7; 95% confidence interval (CI), 1.2-2.5] and, separately, with a stable/increased intake of carbohydrates (HR 2.0; 95% CI, 1.3-5.0). There was a borderline significant interaction between those two variables (P = 0.11). Specifically, carbohydrate intake had no significant impact on risk of recurrence among women who were receptor negative, yet increased the risk of recurrence by more than 5-fold among women who were receptor positive (HR 5.5; 95% CI, 1.8-16.3).

Conclusions

Among women whose tumor tissue is positive for the IGFI receptor, reducing carbohydrate intake after diagnosis could reduce the risk of breast cancer recurrence. These findings need replication in a larger sample.

Impact

This is the first study to suggest that it may be possible to personalize dietary recommendations for breast cancer survivors based on molecular characteristics of their primary tumor tissue. .