Neoadjuvant trastuzumab induces apoptosis in primary breast cancers.
OBJECTIVE
Greater understanding of the cellular response in trastuzumab-treated patients will provide insight into the clinical management of patients.


METHODS
We performed a neoadjuvant trial in 35 patients with locally advanced HER-2/neu overexpressing breast cancers who received weekly trastuzumab given as a single agent for the first 3 weeks, followed by a combination of trastuzumab and docetaxel for 12 weeks before surgery. Sequential core biopsies were taken at baseline and within weeks 1 and 3 after the first dose of trastuzumab. Clinical response to trastuzumab was assessed by tumor measurements on day 22 before chemotherapy. Core biopsies were assessed by immunohistochemistry for cell cycle and proliferation (Ki67, p27, phosphorylated [p] -MAPK), apoptosis and survival (apoptotic index, p-Akt), epidermal growth factor receptor, and total and p-HER-2.


RESULTS
There was early tumor regression with a median decrease of -20.0% (range. 0% to 60.4%) after only 3 weeks of trastuzumab, and eight patients (23%) had a partial response. Consistent with the clinical regressions, apoptosis was significantly induced (median increase from 3.5% to 4.7%; P = .006) within week 1, a 35% increase above baseline. No significant change in epidermal growth factor receptor score was observed in week 1, without changes in total or p-HER-2 expression. Tumors with high baseline Ki67 were less likely to respond (P = .02).


CONCLUSIONS
In primary breast cancers, trastuzumab substantially induces apoptosis, providing a molecular explanation for both its therapeutic efficacy and its successful combination with cytotoxic chemotherapy.
Mohsin
Syed K
SK
Breast Center at Baylor College of Medicine/The Methodist Hospital, 1 Baylor Plaza, MS 600, Houston, TX 77030, USA.
Weiss
Heidi L
HL
Gutierrez
M Carolina
MC
Chamness
Gary C
GC
Schiff
Rachel
R
Digiovanna
Michael P
MP
Wang
Chun-Xia
CX
Hilsenbeck
Susan G
SG
Osborne
C Kent
CK
Allred
D Craig
DC
Elledge
Richard
R
Chang
Jenny C
JC
D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000494:pharmacology* / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000951:Antigens, Neoplasm / Q000032:analysis; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000601:surgery; D002453:Cell Cycle; D049109:Cell Proliferation; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D011446:Prospective Studies; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab