Tolerability of sunitinib in combination with docetaxel and trastuzumab as first-line therapy for HER2+ advanced breast cancer.

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #4120 Background: Trastuzumab (T) combined with docetaxel (D) is approved for the first-line treatment of HER2+ advanced BC (ABC). Sunitinib (SU) is an oral, multitargeted tyrosine kinase inhibitor of VEGFRs, PDGFRs, KIT, RET, and FLT3 with single-agent activity in pts with previously treated ABC. The tolerability and preliminary antitumor activity of SU combined with D and T was investigated in this exploratory study as a first-line regimen for ABC. Materials and methods: A target of 25 female pts (≥18 yrs, ECOG PS 0 or 1) with unresectable, locally recurrent or metastatic HER2+ BC are being enrolled. Starting doses for the 3 treatments are listed in the table below. The primary objective is safety. Secondary endpoints are PK and preliminary tumor activity according to RECIST. After discontinuation of D, responsive pts (PR or SD) can continue SU and T until PD. ![][1] Results: As of May 2008, 18 pts were enrolled; 11 pts continue on study therapy and 7 have discontinued (5 due to PD; 1 due to pt decision; 1 due to G3 fatigue). Of the 18 pts enrolled, 16 are evaluable for safety and 11 for activity. Pts completed 75/96/98 cycles of D/SU/T, respectively, with a median of 5 cycles/pt for each drug (range: 1-13/1-12/1-13). The planned dose of SU (37.5 mg/d) was reduced to 25 mg/d in 6/16 pts due to G4 neutropenia (1); G3 febrile neutropenia (1); G3 fatigue (1); G2 hyperbilirubinemia (1); G2 hypertension (1); and G2 diarrhea (1). D was reduced in 4 pts due to febrile neutropenia (2) and G4 neutropenia (2). T was given q3w in 12 pts and wkly in 4 pts. T dosing was delayed by ≥4 days in 6 pts, 4 due to D dose delay and 2 due to AEs when D was already discontinued (G2 neutropenia and G3 fatigue). Overall, the most frequent AEs were fatigue (68.8%) and neutropenia (43.8%), consistent with the most common toxicities of D. No GI perforation or bleeding were reported. The most frequently reported severe AEs were neutropenia (1 G3 and 6 G4) and febrile neutropenia (5 G3). G-CSF was administered to 8 pts. Of the 11 pts evaluable for antitumor activity, 1 showed a confirmed CR, 7 a confirmed PR, 2 had PD and 1 was not evaluable. Conclusions: The combination of SU 37.5 mg/d (Schedule 2/1) with D 75 mg/m2 q3w and T wkly/3-wkly, given as first-line treatment to HER2+ pts with ABC, shows manageable toxicities. The use of G-CSF appears beneficial. Preliminary antitumor activity is encouraging. Enrollment is ongoing. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4120. [1]: /embed/graphic-1.gif