The purpose of a study was to determine differences in serious adverse events associated with aromatase inhibitors compared with Tamoxifen ( Nolvadex ), and to explore whether these adverse events might be ameliorated by switching to aromatase inhibitors after 2-3 years of Tamoxifen.

The analysis has shown that any duration of aromatase inhibitors was associated with a higher probability of developing cardiovascular disease ( odds ratio, OR=1.20, p=0.01; NNT 143 ) and bone fractures ( OR=1.48, p<0.00001; NNT 34 ), but a reduced probability of venous thrombosis ( OR=0.53, p<0.00001; NNT 67 ) and endometrial carcinoma ( OR=0.32, p<0.00001; NNT 200 ).

The risks of individual serious adverse events were similar for upfront aromatase inhibitors and for switching to aromatase inhibitors after Tamoxifen. However, compared with 5 years of Tamoxifen, there was a non-significant trend towards increased death without recurrence with upfront aromatase inhibitors ( OR=1.12, p=0.16 ), but lower with switching to aromatase inhibitors after Tamoxifen ( OR=0.74, p=0.03 ).

In conclusion, the treatment with aromatase inhibitors is associated with a statistically significant increase in cardiovascular risk, which is of similar magnitude to the risk of venous thrombosis and endometrial cancer with 5-years of Tamoxifen. While switching to aromatase inhibitors does not appear to reduce the risk for the development of serious adverse events when compared to upfront use of aromatase inhibitors, fewer deaths unrelated to breast cancer occur with switching than with upfront strategies.

Source: San Antonio Breast Cancer Symposium ( SABCS ), 2010

XagenaMedicine2010


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