Endocrine responsiveness and tailoring adjuvant therapy for postmenopausal lymph node-negative breast cancer: a randomized trial.
BACKGROUND
The role of adjuvant chemotherapy in postmenopausal patients with lymph node-negative breast cancer is controversial. After demonstrating the efficacy of chemotherapy combined with tamoxifen for postmenopausal patients with lymph node-positive disease, the International Breast Cancer Study Group launched a randomized trial (Trial IX) to evaluate the role of adjuvant chemotherapy preceding treatment with tamoxifen for patients with lymph node-negative disease.


METHODS
After stratification by estrogen receptor (ER) status, patients were randomly assigned to receive three 28-day courses of "classical" adjuvant CMF chemotherapy (cyclophosphamide at 100 mg/m(2) on days 1-14, orally; methotrexate at 40 mg/m(2) on days 1 and 8, intravenously; and 5-fluorouracil at 600 mg/m(2) on days 1 and 8, intravenously) followed by tamoxifen (20 mg/day, orally for 57 months) (CMF-->tamoxifen) or to receive tamoxifen alone (20 mg/day, orally for 60 months). We enrolled 1669 eligible patients, 382 (23%) with ER-negative tumors, 1217 (73%) with ER-positive tumors, and 70 (4%) with unknown ER status. The median follow-up was 71 months. All statistical tests were two-sided.


RESULTS
The added benefit of CMF followed by tamoxifen over tamoxifen alone was statistically significantly dependent on ER status (tests for interaction: P =.01 for disease-free survival [DFS] and P =.07 for overall survival [OS]). For patients with ER-negative tumors, the addition of CMF statistically significantly improved DFS (5-year DFS = 84% for CMF-->tamoxifen versus 69% for tamoxifen alone; difference = 15%; 95% confidence interval [CI] = 6% to 24%; risk ratio [RR] = 0.52; 95% CI = 0.34 to 0.79; P =.003) and OS (5-year OS = 89% for CMF-->tamoxifen versus 81% for tamoxifen alone; difference = 8%; 95% CI = 0% to 16%; RR = 0.51; 95% CI = 0.30 to 0.87; P =.01). By contrast, for patients with ER-positive tumors, addition of CMF provided no benefit in terms of DFS (5-year DFS = 84% for CMF-->tamoxifen versus 85% for tamoxifen alone; difference = -1; 95% CI = -6% to 4%; RR = 0.99; 95% CI = 0.75 to 1.30; P =.92) or OS (5-year OS = 95% for CMF-->tamoxifen versus 93% for tamoxifen alone; difference = 2%; 95% CI = -1% to 5%; RR = 0.95; 95% CI = 0.64 to 1.40; P =.80).


CONCLUSIONS
Postmenopausal patients with lymph node-negative breast cancer benefited substantially from adjuvant chemotherapy if their cancer was ER-negative (i.e., endocrine-nonresponsive). In contrast, if their cancer was ER-positive (i.e., endocrine-responsive), they obtained no benefit from the combination treatment compared with tamoxifen alone.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000628:therapy*; D017024:Chemotherapy, Adjuvant; D003520:Cyclophosphamide / Q000008:administration & dosage*; D004703:Endocrine System / Q000187:drug effects*; D005472:Fluorouracil / Q000008:administration & dosage*; D006801:Humans; D008207:Lymphatic Metastasis / Q000517:prevention & control*; D008727:Methotrexate / Q000008:administration & dosage*; D008875:Middle Aged; D017698:Postmenopause; D011788:Quality of Life; D013629:Tamoxifen / Q000627:therapeutic use* / Q000633:toxicity; D013997:Time Factors; D016896:Treatment Outcome
D018931:Antineoplastic Agents, Hormonal; D013629:Tamoxifen; D003520:Cyclophosphamide; D005472:Fluorouracil; D008727:Methotrexate