Lapatinib monotherapy in patients with relapsed, advanced, or metastatic breast cancer: efficacy, safety, and biomarker results from Japanese patients phase II studies.
BACKGROUND
HER2-positive metastatic breast cancer (MBC) relapsing after trastuzumab-based therapy may require continued HER2 receptor inhibition to control the disease and preserve the patients' quality-of-life. Efficacy and safety of lapatinib monotherapy was evaluated in Japanese breast cancer patients after trastuzumab-based therapies.


METHODS
In studies, EGF100642 and EGF104911 evaluated the efficacy and safety of oral lapatinib given 1500 mg once daily in patients with advanced or MBC. All patients progressed on anthracyclines and taxanes; HER2-positive patients had also progressed on trastuzumab.


RESULTS
For HER2-positive tumours (n=100), objective response rate was 19.0% (95% confidence interval (CI): 11.8-28.1) and clinical benefit rate (CBR) was 25.0% (95% CI: 16.9-34.7). One out of 22 HER2-negative tumour was documented as complete response (n=22). The median time-to-progression (TTP) in the HER2-positive and HER2-negative groups was 13.0 and 8.0 weeks (P=0.007); median overall survival was 58.3 and 40.0 weeks, respectively. The most frequent adverse event was diarrhoea. TTP and CBR were significantly associated with HER2 expression. Patients with tumours harbouring an H1047R PIK3CA mutation or low expression of PTEN derived clinical benefit from lapatinib.


CONCLUSIONS
Lapatinib monotherapy had shown anti-tumour activity in Japanese patients with HER2-positive MBC that relapsed after trastuzumab-based therapy, including those with brain metastases. Patients benefiting from lapatinib may have biomarker profiles differing from that reported for trastuzumab.
Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaracho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan. toi@kuhp.kyoto-u.ac.jp
M
M
Toi
H
H
Iwata
Y
Y
Fujiwara
Y
Y
Ito
S
S
Nakamura
Y
Y
Tokuda
T
T
Taguchi
Y
Y
Rai
K
K
Aogi
T
T
Arai
J
J
Watanabe
T
T
Wakamatsu
K
K
Katsura
C E
CE
Ellis
R C
RC
Gagnon
K E
KE
Allen
Y
Y
Sasaki
S
S
Takashima
D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D018450:Disease Progression; D005260:Female; D006801:Humans; D007564:Japan; D053208:Kaplan-Meier Estimate; D000077341:Lapatinib; D008875:Middle Aged; D011799:Quinazolines / Q000009:adverse effects / Q000627:therapeutic use*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics; D055815:Young Adult
D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D000077341:Lapatinib; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases