Abstract P2-08-14: Dissecting the effect of hormone receptor (HR) status expression in patients (pts) with HER2-positive (HER2+) early breast cancer (EBC): Exploratory analysis from the ALTTO (BIG 2-06) trial
Authors: Lambertini M , Campbell C , Gelber RD , Viale G , McCullough A , Tonghua L , Hilbers F , Korde LA , Werner O , Chumsri S , Jackisch C , Wolff AC , Vaz-Luis I , Ferreira AR , Prat A , Moreno Aspitia A , Piccart M , Loi S , de Azambuja E 
Published: May 2019

Background

We investigated the clinical outcomes and behavior of HER2+ EBC according to centrally tested HR status in pts treated with modern chemotherapy (CT) and trastuzumab (T)-based regimens.

Patients and methods

ALTTO is an international phase 3 trial in HER2+ EBC pts randomized to 4 adjuvant anti-HER2 treatment arms: T alone, lapatinib (L) alone, their sequence (T-&gt;L) or their combination (T+L). Pts in the L alone arm were excluded from the present analysis.

HER2 and HR status were centrally tested for all patients. HER2 status was defined based on the 2007 ASCO/CAP guidelines. HR-positive (HR+) was defined as ≥1% tumor cells with expression of estrogen (ER) and/or progesterone receptors.We investigated the prognosis of pts with HR+ or negative (HR-) HER2+ EBC, the risk of developing early (years 0-5) and late (years 6-8) recurrences, the factors impacting this risk, and the patterns of relapse according to HR status.

Univariate and multivariate Cox proportional hazard models were used to compare hazard rates within the HR subgroups; a conditional landmark analysis was conducted to investigate late recurrences. For the hazard ratios for HR status, an interaction between log(time) and HR status was included as proportional hazard assumption was not satisfied.

Results

This analysis included 6,271 HER2+ pts of whom 3,601 (57%) had HR+ and 2,670(43%) HR- EBC. Median follow-up was 6.93 years (range 6.81-6.96).

5-year disease-free survival (DFS) was 86% (85-87) in HR+ and 83% (82-85) in HR- pts; 8-year DFS was 80% (78-81) in HR+ and 79% (77-81) in HR- pts. The mean annual hazards of recurrence in years 0-5 were 3% in HR+ and 4% in HR- pts, while in years 6-8 they were 3% in HR+ and 2% in HR- pts. The hazard ratios for HR status (ref=HR-) were 0.60 (0.51-0.72) overall, 0.74 (0.65-0.85) for years 0-5 and 1.61 (1.17-2.24) for years 6-8.

In HR+ pts, risk factors for recurrence overall were age ≥65 (p=0.01), tumor size pT3-4 (p&lt;0.001), nodal status pN1-3 (p&lt;0.001), tumor grade 2 or 3 (p&lt;0.001), anthracycline-only CT (p&lt;0.001), no use of aromatase inhibitors (p&lt;0.001), and ER&lt;10% (p=0.01). Main risk factors for recurrence in both years 0-5 and years 6-8 were pN2-3 (p=0.04 for both) and high (≥5) HER2 FISH ratio (p=0.02 for both).

In HR- pts, risk factors for recurrence overall were BMI (obesity or underweight; p=0.01), pT3-4 (p&lt;0.001), pN1-3 (p&lt;0.001) and anthracycline-only CT (p&lt;0.001). No significant risk factors for recurrence in years 0-5 were identified. Main risk factor for recurrence in years 6-8 was BMI (obesity; p=0.002).

HR+ pts had lower incidence of visceral disease (58.8% vs. 69.6%; p=0.005) and lung metastasis (18.5% vs. 27.8%; p=0.006); bone was the most common site of first recurrence (30%).

Conclusions

This large analysis of centrally tested HR+ and HR- HER2+ EBC provides strong evidence on the existence of two different diseases within the HER2+ population based on HR expression. These up-to-date estimates of pts outcomes after modern CT and T-based regimens may be used as “historical control” for the design of future de-escalation or escalation trials separately in HR+ and HR- HER2+ EBC pts.

Citation Format: Lambertini M, Campbell C, Gelber RD, Viale G, McCullough A, Tonghua L, Hilbers F, Korde LA, Werner O, Chumsri S, Jackisch C, Wolff AC, Vaz-Luis I, Ferreira AR, Prat A, Moreno Aspitia A, Piccart M, Loi S, de Azambuja E. Dissecting the effect of hormone receptor (HR) status expression in patients (pts) with HER2-positive (HER2+) early breast cancer (EBC): Exploratory analysis from the ALTTO (BIG 2-06) trial [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-14.