Tamoxifen and megestrol acetate for postmenopausal breast cancer: diverging effects on liver proteins, androgens, and glucocorticoids.
OBJECTIVE
To compare the effects of tamoxifen and megestrol acetate on liver proteins, androgens, and glucocorticoids during adjuvant treatment for postmenopausal breast cancer.


METHODS
A subgroup of women within a large prospective multicenter trial were followed with blood sampling every 3 mo during 2 yr. Women were randomized to receive either continuous tamoxifen 40 mg/d or repeated sequential treatment with tamoxifen and megestrol acetate (MA) 160 mg/d.


RESULTS
We found profound and distinct differences between the two regimens. Tamoxifen increased steroid-binding proteins (SHBG and CBG) and suppressed circulating androgens and IGF-I. In contrast, the metabolic effects of tamoxifen were clearly antagonized by MA. There was a rise in IGF-I and marked suppression of steroid-binding proteins. Levels of free testosterone were reduced by 70%. MA also caused apparent adrenal suppression.


CONCLUSIONS
The different effects on anabolic/catabolic balance and adrenal function may relate to certain clinical effects during treatment.
Löfgren
L
L
Department of Surgery, St Görans Hospital, SE-112 81 Stockholm, Sweden. lars.lofgren@stgoran.se
Wallberg
B
B
Wilking
N
N
Fornander
T
T
Rutqvist
L E
LE
Carlström
K
K
von Schoultz
B
B
von Schoultz
E
E
D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D017024:Chemotherapy, Adjuvant; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D019290:Megestrol Acetate / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D008875:Middle Aged; D017698:Postmenopause; D011446:Prospective Studies; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013629:Tamoxifen / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D013739:Testosterone / Q000097:blood
D018931:Antineoplastic Agents, Hormonal; D012738:Sex Hormone-Binding Globulin; D013629:Tamoxifen; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D019290:Megestrol Acetate