Journal of the National Cancer Institute
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J. Natl. Cancer Inst. · Sep 2005
Editorial CommentCigarettes: a smoking gun in cancer chemoprevention.
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J. Natl. Cancer Inst. · Sep 2005
Randomized Controlled Trial Clinical TrialRandomized trial of letrozole following tamoxifen as extended adjuvant therapy in receptor-positive breast cancer: updated findings from NCIC CTG MA.17.
Most recurrences in women with breast cancer receiving 5 years of adjuvant tamoxifen occur after 5 years. The MA.17 trial, which was designed to determine whether extended adjuvant therapy with the aromatase inhibitor letrozole after tamoxifen reduces the risk of such late recurrences, was stopped early after an interim analysis showed that letrozole improved disease-free survival. This report presents updated findings from the trial. ⋯ Letrozole after tamoxifen is well-tolerated and improves both disease-free and distant disease-free survival but not overall survival, except in node-positive patients.
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J. Natl. Cancer Inst. · Sep 2005
Estrogen receptor-positive, progesterone receptor-negative breast cancer: association with growth factor receptor expression and tamoxifen resistance.
Clinical data indicate that estrogen receptor-positive/progesterone receptor-negative (ER+/PR-) breast cancers are less sensitive to tamoxifen than are ER+/PR+ tumors. It has also been reported that tamoxifen may be less effective in tumors that overexpress either HER-2 or HER-1 (epidermal growth factor receptor) and that signaling through these receptors reduces PR expression in experimental models. We hypothesized that ER+/PR- breast tumors are more likely than ER+/PR+ breast tumors to have an aggressive phenotype, to express HER-1 and overexpress HER-2, and are less likely to benefit from tamoxifen adjuvant therapy. ⋯ ER+/PR- tumors express higher levels of HER-1 and HER-2 and display more aggressive features than ER+/PR+ tumors. As in laboratory models, lack of PR expression in ER+ tumors may be a surrogate marker of aberrant growth factor signaling that could contribute to the tamoxifen resistance observed in these tumors.