Background: Serum IGF-I and IGFBP-3 levels respectively have a positive and negative association with subsequent risk of breast cancer. The anti-oestrogen tamoxifen is widely used as adjunctive therapy after resection of primary breast tumours. Tamoxifen has been reported to influence serum IGF-I, although its effects on BP-3 are unknown. The effects of tumour resection itself on IGF-I and BP-3 levels are unclear.
Aims: To determine the effects of surgery and tamoxifen on IGF-I and BP-3 levels in patients with breast cancer.
Methods: Serum IGF-I was measured by radioimmunoassay (nanograms per mililitre) and IGFBP3 by ELISA (micrograms per mililitre) in 36 pre operative patients (Pre), mean age 61 years, 27 post-operative patients on tamoxifen (Post-T), mean age 59.5 years and 7 post-operative patients not on tamoxifen (Post-NT), mean age 55.5 years. Levels were expressed as a ratio of the upper limit of the age corrected normal range.
Results: Serum IGF-I levels were decreased in Post-T (median ratio plus or minus SD =0.52 plus or minus 0.14) compared to Pre (0.6 plus or minus 0.18, p<0.05) or Post NT (0.62 plus or minus 0.14, p=0.05). There was no significant difference in the BP-3 levels between the three groups. The IGF-I/BP3 ratio was lower in the Post-T (median=0.040 plus or minus 0.013) compared to either Pre (median=0.051 plus or minus 0.027, p<0.05) or Post-NT patients (median=0.054 plus or minus 0.030, p=0.9).
Conclusion: The reduction in circulating IGF-I in response to tamoxifen may in part be responsible for its chemopreventative effects. This benefit is likely to be enhanced further by the lack of effect on BP-3 levels and the consequent decrease in the IGF-I:BP-3 ratio. Removal of the primary tumour does not affect IGF-I levels.
22 - 24 Mar 2004
British Endocrine Societies