BIG 1-98 Letrozole trial
Should either tamoxifen or letrozole be used alone for five years (daily) or should they be used in sequence (one followed by the other), and should tamoxifen or letrozole be given first.
BIG 1-98/IBCSG18-98: Adjuvant Letrozole trial. A phase III study to evaluate Letrozole as adjuvant endocrine therapy for postmenopausal women with receptor (ER and/or PgR) positive tumours.
Previously we did not know whether it would be better to start with anti-oestrogen treatments called Letrozole (an aromatase inhibitors or “AI” for short) soon after diagnosis and continue for five years, or if giving both drugs in a sequence (of letrozole followed by tamoxifen or tamoxifen followed by letrozole) would show superior results. Further results from the Breast International Group (BIG) trial, coordinated in Australia and New Zealand through the ANZ Breast Cancer Trials Group (ANZBCTG) show that it seems to be the most promising strategy to start treatment with letrozole and continue for five years, but if necessary patients, who have particular side effects on letrozole, can switch to tamoxifen after two years without loss of effectiveness.
Letrozole alone is more effective than tamoxifen alone. In terms of what is the best sequence (of letrozole followed by tamoxifen or tamoxifen followed by letrozole), results showed it appears to be better to start treatment with letrozole and continue for five years, but if necessary patients can switch to tamoxifen after two years without loss of effectiveness.
Beyond 10 years results continued to show trends favouring letrozole. Letrozole reduced contralateral breast cancer frequency in the first 10 years, but this wasn’t shown beyond 10 years.
Adjuvant Letrozole and Tamoxifen Alone or Sequentially for Postmenopausal Women With Hormone Receptor-Positive Breast Cancer: Long-Term Follow-Up of the BIG 1-98 Trial. Ruhstaller T, Giobbie-Hurder A, Colleoni M, Jensen MB, Ejlertsen B, de Azambuja E, Neven P, Lang I, Jakobsen EH, Gladieff L, Bonnefoi H, Harvey VJ, Spazzapan S, Tondini C, Del Mastro L, Veyret C, Simoncini E, Gianni L, Rochlitz C, Kralidis E, Zaman K, Jassem J, Piccart-Gebhart M, Di Leo A, Gelber RD, Coates AS, Goldhirsch A, Thurlimann B, Regan MM; members of the BIG 1-98 Collaborative Group and the International Breast Cancer Study Group. J Clin Oncol. 10 January, 2019; 37 (2):105-14