According to the results published in 2004, the American Society of Clinical Oncology (ASCO) has updated its guidelines on the treatment of breast cancer, focusing its attention on the use of tamoxifen and of aromatase inhibitors. The most important points are the following: - women with cancers positive to estrogen receptors should use aromatase inhibitors, both as a primary adjuvant therapy and after 2-3 years of tamoxifen use, up to an overall duration of at least 5 years. - women who, after a starting period with aromatase inhibitors, should interrupt for any reason its assumption, should use tamoxifen to be able to reach 5 years of adjuvant therapy. - women using tamoxifen for 5 years can have further benefits from the use of aromatase inhibitors for 5 further years of adjuvant therapy. - the use of particular markers to identify which is the optimal therapeutical choice is not advised. - because of interactions, it is necessary to pay a particular attention to the use of tamoxifen associated with P2D6 cytochrome inhibitors (paroxetine, fluoxetine, buproprion). - it is necessary to consider the various side effects of the two drugs: venous thromboembolism, endometrial cancer, polyps and endometrial hyperplasia with tamoxifen; osteoporosis, arthralgia and fractures with aromatase inhibitors. If side effects became intolerable, one can make the shift from one class of drugs to the other. - women, in whom pre-menopausal treatment is performed, should start with tamoxifen.
The novelty of these guidelines is in the introduction of aromatase inhibitors into the schemes of adjuvant endocrine therapy, which was previously occupied only by tamoxifen. It is necessary to consider the negative effects on skeleton, so women chosen for this therapy should monitor their bone mineral density and possibly use bisphosphonates, if necessary. Some other points to consider are the tendency to venous thromboembolism in obese women and the tendency to depression in women affected by breast cancer; both conditions imply a particular attention in the prescription of tamoxifen (as to depression, venlafaxine is the most indicated drug in these conditions, since its interaction with P2D6 cytochrome is very low).
