Lapatinib combined with letrozole versus letrozole and placebo as first-line therapy for postmenopausal hormone receptor-positive metastatic breast cancer.
OBJECTIVE
Cross-talk between human epidermal growth factor receptors and hormone receptor pathways may cause endocrine resistance in breast cancer. This trial evaluated the effect of adding lapatinib, a dual tyrosine kinase inhibitor blocking epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2), to the aromatase inhibitor letrozole as first-line treatment of hormone receptor (HR) -positive metastatic breast cancer (MBC).


METHODS
Postmenopausal women with HR-positive MBC were randomly assigned to daily letrozole (2.5 mg orally) plus lapatinib (1,500 mg orally) or letrozole and placebo. The primary end point was progression-free survival (PFS) in the HER2-positive population. Results In HR-positive, HER2-positive patients (n = 219), addition of lapatinib to letrozole significantly reduced the risk of disease progression versus letrozole-placebo (hazard ratio [HR] = 0.71; 95% CI, 0.53 to 0.96; P = .019); median PFS was 8.2 v 3.0 months, respectively. Clinical benefit (responsive or stable disease >or= 6 months) was significantly greater for lapatinib-letrozole versus letrozole-placebo (48% v 29%, respectively; odds ratio [OR] = 0.4; 95% CI, 0.2 to 0.8; P = .003). Patients with centrally confirmed HR-positive, HER2-negative tumors (n = 952) had no improvement in PFS. A preplanned Cox regression analysis identified prior antiestrogen therapy as a significant factor in the HER2-negative population; a nonsignificant trend toward prolonged PFS for lapatinib-letrozole was seen in patients who experienced relapse less than 6 months since prior tamoxifen discontinuation (HR = 0.78; 95% CI, 0.57 to 1.07; P = .117). Grade 3 or 4 adverse events were more common in the lapatinib-letrozole arm versus letrozole-placebo arm (diarrhea, 10% v 1%; rash, 1% v 0%, respectively), but they were manageable.


CONCLUSIONS
This trial demonstrated that a combined targeted strategy with letrozole and lapatinib significantly enhances PFS and clinical benefit rates in patients with MBC that coexpresses HR and HER2.
Royal Marsden Hospital, London, United Kingdom. stephen.johnston@rmh.nhs.uk
Stephen
S
Johnston
John
J
Pippen
Xavier
X
Pivot
Mikhail
M
Lichinitser
Saeed
S
Sadeghi
Veronique
V
Dieras
Henry Leonidas
HL
Gomez
Gilles
G
Romieu
Alexey
A
Manikhas
M John
MJ
Kennedy
Michael F
MF
Press
Julie
J
Maltzman
Allison
A
Florance
Lisa
L
O'Rourke
Cristina
C
Oliva
Steven
S
Stein
Mark
M
Pegram
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000009:adverse effects; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage* / Q000009:adverse effects; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000401:mortality / Q000473:pathology / Q000556:secondary*; D018572:Disease-Free Survival; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D000077341:Lapatinib; D000077289:Letrozole; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D009570:Nitriles / Q000008:administration & dosage / Q000009:adverse effects; D017698:Postmenopause / Q000187:drug effects; D011379:Prognosis; D016016:Proportional Hazards Models; D011799:Quinazolines / Q000008:administration & dosage / Q000009:adverse effects; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism*; D018570:Risk Assessment; D016019:Survival Analysis; D016896:Treatment Outcome; D014230:Triazoles / Q000008:administration & dosage / Q000009:adverse effects
D018931:Antineoplastic Agents, Hormonal; D014408:Biomarkers, Tumor; D000077341:Lapatinib; D000077289:Letrozole; D009570:Nitriles; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D014230:Triazoles