Abstract PD5-07: The impact of early lapatinib-induced rash on disease-free and overall survival in patients treated within the ALTTO phase III randomized trial
Authors: Azim HA , Sonnenblick A , Agbor-Tarh D , Bradbury I , Daly F , Huang Y , Dueck AC , Pritchard K , Wolff AC , Jackisch C , Lang I , Untch M , Smith I , Boyle F , Xu B , Gomez H , Perez E , Piccart M , de Azambuja E 
Published: May 2016

Background: We have previously shown in a phase III neoadjuvant trial that early development of lapatinib-induced rash (i.e. within 6 weeks after lapatinib initiation) is independently associated with a higher chance of obtaining a pathological complete response (Azim et al; JCO 2013). In the current study, we aimed to investigate whether early lapatinib-induced rash is associated with improved survival in the context of a large phase III adjuvant trial.

Methods: This analysis is based on the ALTTO trial (BIG 2-06, Alliance N063D), in which patients with HER2-positive early breast cancer were randomized to adjuvant trastuzumab, lapatinib, their sequence or their combination for a total duration of 1 year. In this sub-study, we evaluated whether the development of rash (any grade) within 6 weeks of lapatinib initiation was associated with disease-free (DFS) and overall survival (OS). All analyses were tested in a multivariate model adjusted for treatment arm, treatment completion and trial stratification factors.

Results: A total of 6,098 lapatinib-treated patients were included in the current analysis; of whom 2,006 patients (32.9%) developed early lapatinib-induced rash, 1,025 (16.8%) developed rash after 6 weeks and 3,067 (50.3%) did not develop rash. No differences in patient characteristics were observed between the three groups apart from a higher frequency of younger patients (≤ 50) in the early rash group (54% vs. 47% and 44%, p&lt;0.0001). At a median follow-up of 4.5 years, 876 (14.37%) and 377 (6.18%) patients in the lapatinib containing arms experienced a DFS and OS event, respectively. In a multivariate analysis confined to patients randomized to the lapatinib containing arms, the development of early rash was associated with improved DFS (HR: 0.80; 95%CI: 0.69-0.93, p=0.004) and OS (HR: 0.61; 95%CI: 0.48 - 0.78, p&lt;0.001) compared to patients who did not develop early rash, with no interaction according to patient's age (p=0.9). No significant association was observed between the development of rash after 6 weeks of lapatinib initiation and survival. Compared to patients randomized to the trastuzumab alone arm (n=2,076), patients who developed early rash in the sequence (n=580) or combination (n=704) arms of trastuzumab/lapatinib had superior DFS (Sequence: HR 0.75 [95% CI: 0.58 – 0.98], p=0.034; Combination: HR 0.69 [95% CI: 0.54 – 0.89], p=0.005) and OS (Sequence: HR 0.57 [95%CI: 0.36 – 0.88], p=0.012; Combination: HR 0.59 [95% CI: 0.39 – 0.89], p=0.011). On the other hand, patients randomized to the lapatinib only arm who developed early rash (n=722) still had inferior DFS (HR 1.28 [95% CI: 1.04 – 1.59], p=0.02) with no difference in OS (HR: 0.95; 95%CI: 0.67 – 1.35, p=0.79) compared to patients randomized to the trastuzumab alone arm.

Conclusions: The results support our previous findings in the neoadjuvant setting that early development of skin rash within the first 6 weeks can identify patients who derive superior benefit of lapatinib treatment.

Citation Format: Azim Jr HA, Sonnenblick A, Agbor-Tarh D, Bradbury I, Daly F, Huang Y, Dueck AC, Pritchard K, Wolff AC, Jackisch C, Lang I, Untch M, Smith I, Boyle F, Xu B, Gomez H, Perez E, Piccart M, de Azambuja E. The impact of early lapatinib-induced rash on disease-free and overall survival in patients treated within the ALTTO phase III randomized trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD5-07.