Conjugated estrogen and breast cancer risk
—VIRGINIA DONNELLY, MSN, ARNP-C, Yardville, N.J.
This has long been a troublesome question. The package inserts for topical conjugated estrogen preparations contain all the same contraindication information as those for oral and transdermal estrogens, even though vaginal preparations are intended for local rather than systemic effect.
A number of conditions affect the amount of systemic absorption. Atrophy and thinning of mucosal membranes results in increased absorption, as does the dose of product used. Most vaginal products carry the recommendations that they be used at a higher initial dose until re-epithelialization is complete; a lower dose is then used for maintenance therapy. The highest-dose vaginal creams (1.25 g conjugated equine estrogen [CEE]) reach a serum level of 60 pg/mL of estradiol, which is the same as with an oral dose of CEE. A tablet formulation of 17-beta estradiol showed "low" systemic absorption during the maintenance phase of treatment. As always, each patient should be considered based on her particular circumstances. However, with low levels of circulating estrogen, the risk factors would be reduced greatly. For more information, see Menopause. 2000;7:156-161 and Obstet Gynecol. 1994;84:215-218.
—Sherril Sego, MSN, FNP (129-6)