RESUMO
BACKGROUND: Aromatase inhibitors (AIs) are central to the management of oestrogen receptor-positive breast cancer in the adjuvant and metastatic setting. Levels of circulating steroid hormones (SHs) were measured in patients established on AIs to investigate: the influence of body mass index (BMI) in both the adjuvant and metastatic setting; the class of AI utilized in the adjuvant setting (steroidal versus non-steroidal); and differences in SH levels between women treated adjuvantly and those receiving a second-line AI for locally advanced/metastatic disease. METHODS: Plasma levels of androstenedione, 5-androstene-3ß,17ß-diol, dehydroepiandrosterone, oestradiol and testosterone were measured by radioimmunoassay in women with breast cancer who were receiving AIs in either an adjuvant or a metastatic setting. Differences between mean SH levels by class of AI, BMI, and second-line versus adjuvant therapy were assessed. RESULTS: Sixty-four women were receiving AI therapy, 45 (70 per cent) in an adjuvant setting and 19 (30 per cent) were taking a second-line AI. There was no significant correlation between BMI and SH levels. However, BMI was significantly higher in the second-line AI cohort compared with the adjuvant cohort (29.8 versus 26.2 kg/m2 respectively; P = 0.026). In the adjuvant setting, patients receiving a steroidal AI had significantly higher levels of all five hormones (P < 0.050). In the second-line AI cohort, oestradiol levels were significantly higher than in the adjuvant cohort (4.5 versus 3.3 pg/ml respectively; P = 0.022). Multivariable analysis adjusted for BMI confirmed the higher residual oestradiol level in the second-line AI group (P = 0.063) and a significantly higher androstenedione level (P = 0.022). CONCLUSION: Residual levels of SH were not significantly influenced by BMI. However, the significant differences in residual SH levels between the second-line and adjuvant AI cohort is of relevance in the context of resistance to AI therapy, and warrants further investigation.