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Benefits of switching postmenopausal women with hormone-sensitive early breast cancer to anastrozole after 2 years adjuvant tamoxifen: Combined results from 3,224 women enrolled in the ABCSG Trial 8 and the ARNO 95 trial.
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Benefits of switching postmenopausal women with hormone-sensitive early breast cancer to anastrozole after 2 years adjuvant tamoxifen: Combined results from 3,224 women enrolled in the ABCSG Trial 8 and the ARNO 95 trial
Objectives of the combined analysis of ABCSG Trial 8 and the German ARNO 95 trial • To prospectively assess whether switching postmenopausal women with hormone receptor-positive early breast cancer from adjuvant tamoxifen (TAM) to anastrozole (ANA) at 2 years is more effective than continuing on adjuvant TAM
Trial endpoints • Primary endpoint • Event-free survival (EFS) • Secondary endpoints include • Distant recurrence-free survival (DRFS) • Tolerability Events = locoregional recurrences, distant metastases, contralateral breast cancer
ABCSG 8 – ARNO 95:Combined analysis trial structure Total patients n=3,224 ABCSG 8 n=2,262 + ARNO 95 n=962 TAM 3 years n=1,606 Primary surgery +/- RTx + TAM 2 years ANA 3 years n=1,618
Event-free survival:28 months median follow-up Number Events 3yrs EFS n=3,224 n=177 TAM 1,606 110 92.7% ANA 1,618 67 95.8% Events = locoregional recurrences, distant metastases, contralateral breast cancer
Event-free survival Event-free survival (%) 100 ANA 95 90 TAM 85 80 ANA vs TAM p=0.0009HR 0.60 [95% CI 0.44-0.81] 75 0 0 1 2 3 4 5 EFS time in years* At risk: 858 1606 1217 343 176 TAM 593 874 1618 1243 375 178 ANA 623 *Zero point = 2 years after surgery
TAM 1224 869 600 ANA 1247 879 631 Distant recurrence-free survival 100 Distant recurrence-free survival (%) ANA 96 92 TAM 88 ANA ANA vs vs TAM TAM 84 HR 0.61 [95% CI 0.42-0.87] p p =0.0067 =0.0067 0 0 1 2 3 4 5 DRFS time in years At risk: 1606 351 181 1618 382 181 *Zero point = 2 years after surgery
Subgroup analysis of EFS n 3,224 2,389 833 3,044 167 1,265 1,959 2,519 564 All patients Nodal status -ve +ve Grading G1, G2, Gx G3 Age <60 years 60 years Receptor (ER / PR) +ve / +ve +ve / -ve 0.25 0.50 0.80 1.00 1.25 1.50 2.00 3.00 ANA better TAM better Hazard ratio (ANA vs TAM)
Overall survival Number Deaths 3 yrs. OS (%) TAM 1,606 59 96.4 ANA 1,618 45 97.1 ANA vs TAM p=0.16 HR 0.76 95% CI 0.52-1.12
Tolerability data from ABCSG 8 • Both treatments were well tolerated • The incidence of prespecified side effects was low in both groups • As expected, there were significantly more fractures in patients switching to anastrozole: 27 (2.4%) vs 14 (1.2%) for tamoxifen • No significant difference between treatments was seen in gynaecological side effects because - as seen in ATAC - these generally occur soon after starting tamoxifen
Summary • Switching from TAM to ANA at 2 years is superior to continuing on TAM in terms of: • EFS (HR=0.60) • DRFS (HR=0.61) • The benefits of switching to ANA are seen regardless of baseline prognostic factors • ANA is more effective in G1/G2 tumors • Both treatments are well tolerated
Main question for the future • We now know that ANA is superior to TAM when used as: • Initial adjuvant therapy for 5 years and • When patients are switched from TAM • Trials are needed to determine if one of these approaches is more appropriate than the other
Conclusion Postmenopausal women currently on adjuvant tamoxifen should be switched to anastrozole after 2 years of treatment