Systematic review of lapatinib in combination with letrozole compared with other first-line treatments for hormone receptor positive(HR+) and HER2+ advanced or metastatic breast cancer(MBC).
BACKGROUND
Third-generation aromatase inhibitors (letrozole, anastrozole) have shown superior efficacy in early and advanced breast cancer compared with tamoxifen. For HR+, HER2+ MBC, combination of an AI with an anti-HER2 agent (lapatinib or trastuzumab) has shown clinical benefit.


METHODS
Six databases were searched until January 2009 for randomized controlled clinical trials, assessing the safety and efficacy of first-line treatments for postmenopausal women with HR+ and HER2 (ErbB2) positive MBC, who have not received prior therapy for advanced or metastatic disease. Relevant interventions were lapatinib, aromatase inhibitors, tamoxifen, and trastuzumab. Outcomes included overall survival (OS), progression-free-survival (PFS), time-to-progression (TTP), and objective response rate (ORR).


RESULTS
Eighteen studies (62 papers) were included. Lapatinib + letrozole was significantly superior to letrozole alone based on a direct head-to-head study in terms of PFS/TTP and ORR. Using a network meta-analysis, compared with lapatinib + letrozole, tamoxifen (HR = 0.45 (95% CI: 0.32, 0.65) and anastrozole (HR = 0.53 (0.36, 0.80)) scored significantly worse in terms of PFS/TTP and ORR (tamoxifen: OR = 0.25 (0.12, 0.53), anastrozole: OR = 0.27 (0.12, 0.58). The combination also seemed significantly superior to exemestane in terms of PFS/TTP (HR = 0.52 (0.34, 0.79)). Lapatinib + letrozole also seemed better, although not significantly, in terms of OS versus tamoxifen: HR = 0.74 (0.49, 1.12), anastrozole: HR = 0.71 (0.45, 1.14) and exemestane: HR = 0.65 (0.39, 1.11). When compared with trastuzumab + anastrozole, lapatinib + letrozole seemed to be better in terms of OS (HR = 0.85 (0.47, 1.54)), PFS/TTP (HR = 0.89 (0.54, 1.47)) and ORR (OR = 0.92 (0.24, 3.48)), although, none of these results were significant.


CONCLUSIONS
Lapatinib + letrozole was significantly superior to letrozole in terms of PFS/TTP and ORR based on a direct head-to-head study. Indirect comparisons appeared to favor lapatinib + letrozole versus other first-line treatments used in this patient population in terms of three main outcomes: OS, PFS/TTP and ORR. Indirect comparison results are based on a network analysis for which the basic assumptions of homogeneity, similarity and consistency were not fulfilled. Therefore, despite the fact that these are the best available data, the results need to be interpreted with caution.
Kleijnen Systematic Reviews Ltd., York, UK. rob@systematic-reviews.com
Rob
R
Riemsma
Carol A
CA
Forbes
Mayur M
MM
Amonkar
Konstantinos
K
Lykopoulos
Jose R
JR
Diaz
Jos
J
Kleijnen
Daniel W
DW
Rea
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018450:Disease Progression; D005260:Female; D006801:Humans; D000077341:Lapatinib; D000077289:Letrozole; D020360:Neoadjuvant Therapy; D009362:Neoplasm Metastasis; D009570:Nitriles / Q000008:administration & dosage* / Q000009:adverse effects; D011799:Quinazolines / Q000008:administration & dosage* / Q000009:adverse effects; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D014230:Triazoles / Q000008:administration & dosage* / Q000009:adverse effects
D000077341:Lapatinib; D000077289:Letrozole; D009570:Nitriles; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D018160:Receptors, Cytoplasmic and Nuclear; D014230:Triazoles; C508053:ERBB2 protein, human