SPECIAL FEATURE New strategy for HER-2 testing and trastuzumab therapy

The role of trastuzumab in the management of HER2-positivemetastatic breast cancer: an updated review

Yutaka Tokuda Æ Yasuhiro Suzuki ÆYuki Saito Æ Shinobu Umemura

Received: 11 January 2009 / Accepted: 21 May 2009 / Published online: 17 July 2009

� The Japanese Breast Cancer Society 2009

Abstract Currently, trastuzumab is one of the key drugs

in the treatment strategy for HER2-positive breast cancer.

Although metastatic breast cancer is unlikely to be cured,

some HER2-positive patients have survived for a long time

with complete response to trastuzumab therapy. In HER2-

positive metastatic breast cancer, single agent trastuzumab

is effective and less toxic. Combination of trastuzumab

with cytotoxic drugs is also effective. Therefore, major

guidelines recommend using trastuzumab as a key drug in

the management of HER2-positive metastatic breast can-

cer. However, many clinical questions still need to be

solved. In this article, recent evidence was reviewed to find

some answers about these issues.

Keywords Metastatic breast cancer � HER2-positive �Trastuzumab

Introduction

Currently, trastuzumab is one of the key drugs in the

treatment strategy for HER2-positive breast cancer.

Although metastatic breast cancer is unlikely to be cured,

some patients have survived for a long time with complete

response to trastuzumab therapy [1]. In HER2-positive

metastatic breast cancer, single agent trastuzumab is

effective with favorable toxicity. Combination of trast-

uzumab with cytotoxic drugs is also effective. Therefore,

major guidelines recommend using trastuzumab as a key

drug in the treatment strategy of HER2-positive metastatic

breast cancer. However, many clinical questions still need

to be solved. In this article, recent evidence is reviewed to

find some answers about these issues.

Trastuzumab combined with hormone therapy for

HER2 and hormone receptor-positive breast cancer

To select proper treatment, tumor biology and clinical

factors should be considered for each patient. Approxi-

mately half of breast cancers are HER2-positive as well as

hormone receptor-positive. Generally, endocrine therapy is

preferred for initial treatment of hormone receptor-positive

metastatic breast cancer because of its favorable toxic

profile. The National Comprehensive Cancer Network

(NCCN) guideline recommends trastuzumab for beyond

first-line therapy in patients refractory to standard endo-

crine therapy [2]. However, preclinical [3] and clinical [4]

evidence suggests that HER2 positivity gives intrinsic

resistance to hormone therapy. The targeting of both hor-

mone receptors and HER2 signaling pathways in hormone

receptor and HER2-positive breast cancers may overcome

resistance to anti-estrogen therapy. Thus, another option

for HER2-positive and hormone receptor-positive meta-

static breast cancer patients is the combination of trast-

uzumab and endocrine therapy.

In terms of this issue, a randomized trial was conducted

[5]. The TAnDEM study randomly assigned 208 post-

menopausal patients with HER2-positive and hormone

receptor-positive metastatic breast cancer to anastrozole

alone or anastrozole plus trastuzumab. Anastrozole 1 mg

Y. Tokuda (&) � Y. Suzuki � Y. Saito

Department of Breast and Endocrine Surgery, Tokai University

School of Medicine, 143 Shimokasuya, Isehara,

Kanagawa 259-1193, Japan

e-mail: tokuda@is.icc.u-tokai.ac.jp

S. Umemura

Department of Pathology, Tokai University School of Medicine,

143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan

123

Breast Cancer (2009) 16:295–300

DOI 10.1007/s12282-009-0142-8

was administered daily, and trastuzumab 4 mg/kg of

loading dose was administered on week 1 followed by

2 mg/kg weekly until disease progression. Crossover to

receive trastuzumab was actively offered to all patients

who progressed on anastrozole alone. A preliminary anal-

ysis reported that benefits of combination showed a sig-

nificantly better overall response rate (20 vs. 7%) as well as

progression-free survival (4.8 vs. 2.4 months, P = 0.0016).

Seventy percent of the patients initially assigned to anas-

trozole alone received trastuzumab later during the course

of the disease. Overall survival of the combination group

was 28.5 months compared with 23.9 months for the an-

astrozole alone group (P = 0.325). Cardiac toxicity

developed in 13 of 103 patients of the combination group

compared with 2 of 104 patients of the anastrozole alone

group. Therefore, combinations of hormone therapy plus

trastuzumab for patients with HER2-positive metastatic

breast cancer seem to be safe and have promising efficacy.

Trastuzumab alone versus trastuzumab plus

chemotherapy as first-line treatment

Trastuzumab monotherapy has shown efficacy and is well

tolerated. Thus, the NCCN guideline recommends both

trastuzumab alone and combination of trastuzumab and

chemotherapy as first-line treatment for HER-positive

metastatic breast cancer patients [2]. However, the clinical

question of whether trastuzumab monotherapy followed by

trastuzumab and chemotherapy at disease progression has

equal efficacy to an initial combination therapy of trast-

uzumab and chemotherapy remains to be answered. A

randomized phase III study of trastuzumab monotherapy

followed by docetaxel and trastuzumab versus the combi-

nation of trastuzumab and docetaxel as first-line treatment

was conducted in Japan.

A result of the first-analysis was reported at the San

Antonio Breast Cancer Symposium in 2008 [6]. Eligible

patients had HER2-positive metastatic breast cancer with a

measurable tumor based on RECIST, ECOG performance

status 0 or 1, and left ventricular ejection fraction more than

50%. Patients with prior chemotherapy for metastatic breast

cancer, adjuvant trastuzumab and docetaxel were excluded.

The patients were randomly assigned to sequential weekly

trastuzumab 2 mg/kg (loading 4 mg/kg) alone followed by

a combination of docetaxel (60 mg/m2 every 3 weeks) and

trastuzumab at disease progression or concurrent combi-

nation of trastuzumab and docetaxel. Primary endpoints

were time to progression of trastuzumab alone and combi-

nation of trastuzumab and docetaxel and overall survival.

Secondary endpoints were overall response rates, progres-

sion-free survival of sequential trastuzumab monotherapy

followed by docetaxel and trastuzumab, time to treatment

failure of trastuzumab monotherapy versus the initial

combination group and safety in both arms.

The planned sample size was 80 patients in each group.

The Independent Data Management Committee recom-

mended stopping recruitment because there was a signifi-

cant difference in death rate. Finally, 112 patients were

enrolled, and 107 patients were analyzed. Statistically

significant progression-free survival was observed for the

trastuzumab and docetaxel group compared with the

trastuzumab monotherapy group (HR: 4.24, P \ 0.0001).

In terms of overall survival, the results suggested that the

combination group was superior to the sequential group

(HR: 2.72, P = 0.0352), though the number of deaths was

insufficient. Time to treatment failure was significantly

superior in the combination group. Overall response rates

were 67.9% for the combination group, 14.8% for trast-

uzumab monotherapy and 47.2% for sequential trast-

uzumab and docetaxel. According to the above evidence, a

combination of trastuzumab and cytotoxic drugs could be

considered as standard for first-line therapy.

Trastuzumab combined with anthracyclines

In preclinical studies, cisplatin, thiotepa and etoposide

were found to be synergistic with trastuzumab. Additive

interactions were observed with doxorubicin, paclitaxel,

methotrexate and vinblastine [7]. Thus, to determine the

efficacy and safety of trastuzumab in combination with

chemotherapy as a first-line treatment for patients with

HER-2-overexpressing metastatic breast cancers, a ran-

domized, placebo-controlled, multicenter, multinational

phase III trial was designed [8]. Patients without prior

anthracycline treatment were randomly grouped to receive

trastuzumab plus anthracycline (doxorubicin or epirubicin)/

cyclophosphamide (AC) or AC alone. Cyclophosphamide

(600 mg/m2) was administered in combination with

doxorubicin (80 mg/m2) or epirubicin (75 mg/m2). Che-

motherapy was repeated every 3 weeks for six cycles.

Patients with prior anthracycline treatment in the adjuvant

setting received either trastuzumab plus paclitaxel or just

paclitaxel. Paclitaxel (175 mg/m2) was administered by IV

infusion over a 3-h period, after premedication. Four

hundred sixty-nine HER-2-overexpressing breast cancer

patients without prior chemotherapy for metastatic disease

were enrolled.

The overall response rates were 60% for trastuzumab

plus AC and 42% for AC alone. Median duration of

response was 9.1 months for trastuzumab plus AC and

6.5 months for AC alone (P = 0.0025). Median time to

progression was 8.1 months for trastuzumab plus AC and

6.0 months for AC alone. Median overall survival was

31 months for trastuzumab plus AC and 21 months for AC

296 Breast Cancer (2009) 16:295–300

123

alone. Therefore, trastuzumab plus concomitant anthracy-

clines demonstrated significant clinical activity.

A syndrome of cardiac dysfunction was reported more

commonly with trastuzumab plus AC (27%; NYHA class

III or IV) than with AC alone (8%), paclitaxel alone (1%),

or trastuzumab plus paclitaxel (13%). To date, the mech-

anism of adverse effects of trastuzumab on cardiac function

has not been fully explained. These results led to the

general recommendation that combined use of anthracy-

clines and trastuzumab should be avoided. However,

combining trastuzumab with anthracyclines is still attrac-

tive. Thus, some recent trials showed impressive efficacy

and no significant cardiotoxicity with the combination. At

the neoadjuvant setting, trastuzumab was used concurrently

with fluorouracil, epirubicin and cyclophosphamide with-

out significant cardiotoxicity [9]. For metastatic breast

cancer, epirubicin or liposomal doxorubicin was also

investigated to obtain more than 60% overall response rates

without significant cardiotoxicity [10–12] (Table 1).

Amrubicin is a third generation, totally synthetic

anthracycline (Fig. 1). In preclinical studies, amrubicin

demonstrated a higher level of anti-tumor activity than

conventional anthracyclines without showing any evidence

of the cumulative cardiac toxicity [13]. Therefore, the

authors investigated the combination of amrubicin and

trastuzumab in a human tumor xenograft model with

HER2-positive cancer. The data suggested a therapeutic

advantage in the administration of trastuzumab in combi-

nation with amrubicin (Fig. 2). This promising combina-

tion warrants further clinical evaluation in the treatment of

HER2-positive breast cancer [14].

Trastuzumab plus taxanes

In the pivotal trial [8], patients with prior anthracycline

treatment in the adjuvant setting received either trast-

uzumab plus paclitaxel or just paclitaxel. Compared to

paclitaxel alone, combined therapy had a significantly

higher response rate (38 vs. 16%) and time to disease

progression (7 vs. 3 months), and a trend toward better

median overall survival (22 vs. 18 months).

A similar antitumor efficacy has been reported with

trastuzumab plus docetaxel [15]. In a phase II trial, 186

metastatic breast cancer patients without prior chemother-

apy were randomly assigned to docetaxel with or without

trastuzumab. Trastuzumab plus docetaxel demonstrated

significantly better response rates (61 vs. 34%), time to

disease-progression (12 vs. 6 months), and median overall

survival (31 vs. 23 months).

In the phase II HERTAX trial, 101 metastatic breast

cancer patients without prior chemotherapy were randomly

assigned to combined therapy with trastuzumab plus

docetaxel (100 mg/m2 every 3 weeks) or trastuzumab

monotherapy at the same dose followed by docetaxel alone

at progression. Progression-free survival, the primary end-

point, was defined as the time from treatment initiation until

disease progression or death for combined therapy, and

from treatment initiation until disease progression on sub-

sequent docetaxel or death for the sequential monotherapy.

In a preliminary report from the 2008 ASCO meeting [16],

combined therapy demonstrated a significantly higher

overall response rate (73 vs. 50%), but there was no sig-

nificant benefit to combined therapy in terms of progres-

sion-free survival (9.4 vs. 10.8 months), and the difference

in median overall survival was not significant (30.5 vs.

20.2 months). According to the UpToDate systematic

review [17], serial administration of trastuzumab alone

followed by taxane monotherapy at disease progression is

an acceptable alternative and is a preferred strategy for

indolent and/or relatively asymptomatic disease.

Trastuzumab plus taxane versus trastuzumab plus

vinorelbine

Combinations of vinorelbine and trastuzumab are also

active for patients with taxane-refractory metastatic breast

cancer. Although this combination of trastuzumab with

vinorelbine appears to be as active as combinations of

trastuzumab with a taxane, its place in the treatment

algorithm for HER2-positive metastatic breast cancer is

uncertain. In one study, the TRAVIOTA, efficacy of

trastuzumab plus vinorelbine for first-line treatment was

compared with that of trastuzumab plus taxane for HER2-

positive metastatic breast cancer [18]. Eighty-one patients

were randomly assigned to trastuzumab plus vinorelbine

25 mg/m2/week (n = 41) or trastuzumab plus paclitaxel

Table 1 Trastuzumab plus anthracyclines: clinical trials in metastatic breast cancer

References Regimen N ORR (%)

Untch et al. [10] Epirubicin/cyclophosphamide (60/600 mg/m2) 26 62

Epirubicin/cyclophosphamide (90/600 mg/m2) 25 64

Theodoulou et al. [11] Myocet� (60 mg/m2, q3w) 33 58

Cortes et al. [12] Myocet� (50 mg/m2, q3w) 69 98

Paclitaxel (80 mg/m2, qw)

Breast Cancer (2009) 16:295–300 297

123

(80 mg/m2/week) (n = 14), docetaxel (35 mg/m2/week)

(n = 24) or paclitaxel (175 mg/m2) plus carboplatin

(AUC 6) (n = 2). Median time to disease-progression

was 8.5 months for trastuzumab plus vinorelbine and

6.0 months for trastuzumab plus taxane (P = 0.09).

Overall response rates were 51% for trastuzumab plus

vinorelbine and 40% for trastuzumab plus taxane, though

the difference was not significant because of the small

sample size. In terms of toxicity, alopecia was less frequent

in the combination with vinorelbine than that with taxanes.

Thus, the combination with vinorelbine could be chosen by

some patients.

Trastuzumab continuation beyond progression

An important clinical question is whether trastuzumab

should be continued after progression on the first trast-

uzumab-containing regimen. A preclinical study showed

that the combination of trastuzumab with taxanes was more

effective than cytotoxic chemotherapy alone after being

refractory to trastuzumab [19].

A German trial, the GBG-26/BIG3-05 trial, randomly

assigned 156 patients with progressive metastatic breast

cancer under trastuzumab-based first-line therapy to cape-

citabine 2,500 mg/m2 daily for 14 of every 21 days with or

without trastuzumab. Trastuzumab 6 mg/kg was adminis-

tered every 3 weeks. The trial was prematurely closed

because of slow accrual. However, a preliminary report

showed that the overall response rate was 48% for the

combination group and 27% for capecitabine alone

(P = 0.011) [20]. Median time to disease-progression, a

Fig. 1 Structures of anthracyclines

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Tu

mo

r w

eig

ht

(g)

Control Trastuzumab Amrubicin Trastuzumab/Amrubicin

p<0.0001

p<0.0001

p=0.001

Fig. 2 Effects of trastuzumab and amrubicin on HER2-positive

human tumor xenografts in athymic nude mice. A tumor fragment of

HER2-positive human gastric cancer xenograft (4-1 ST [22]) was

subcutaneously inoculated into female Balb/cA athymic nude mice.

Mice were randomly divided into experimental groups when each

tumor had reached a palpable size (100–300 mm3). Five weeks after

tumor inoculation, mice bearing the tumors were treated with a single

intravenous administration of trastuzumab (36 mg/kg) (T), amrubicin

(25 mg/kg) (A) or trastuzumab plus amrubicin (T ? A). Mean tumor

weight (g) of T ? A was significantly reduced to 0.233 ± 0.27,

compared with that of control (3.152 ± 0.83) (P \ 0.0001), T

(2.697 ± 0.64) (P \ 0.0001) and A (0.870 ± 0.31) (P = 0.001)

298 Breast Cancer (2009) 16:295–300

123

primary endpoint, was 8.2 months for the combination

group and 5.6 months for the capecitabine alone group

(HR = 0.69, P = 0.034). Median overall survival was

25.5 months for the combination and 20.4 months for the

capecitabine group (HR = 0.76, P = 0.26). Therefore,

continuing trastuzumab beyond progression appears to

improve the efficacy of second-line capecitabine treatment.

Trastuzumab plus lapatinib versus lapatinib

monotherapy

A benefit for continued trastuzumab after progression was

also suggested in a randomized trial, EGF104900, pre-

sented at the 2008 ASCO meeting [21]. The trial assigned

296 patients with progressive metastatic breast cancer

under trastuzumab-based therapy to lapatinib alone

(1,500 mg, daily) and lapatinib (1,000 mg, daily) plus

continuation of trastuzumab. The overall response rate was

10.3% for combined therapy and 6.9% for lapatinib alone

(P = 0.46). Clinical benefit rates were 24.7 and 12.4% for

combined therapy and lapatinib alone, respectively (P =

0.01). Median progression-free survival was 2.8 months for

combined therapy and 1.9 months for lapatinib alone

(P = 0.008), although overall survival was not signifi-

cantly different.

In conclusion, according to the data obtained so far, the

authors recommend a treatment algorithm as shown in the

Fig. 3. Hormone receptor-positive patients with favorable

prognosis such as bone or soft tissue metastases only are

recommended to be treated by endocrine therapy and

concurrent trastuzumab. Hormone receptor- negative

patients, hormone receptor-positive and endocrine refrac-

tory patients, or hormone receptor-positive patients with

unfavorable prognosis should be treated by trastuzumab

combined with chemotherapy. After disease progression on

a first-line trastuzumab-containing regimen, trastuzumab

should be continued with a second- or third-line chemo-

therapy. After approval of lapatinib in Japan, the regimen

of capecitabine and lapatinib is also an option for patients

progressive on a trastuzumab-containing regimen.

References

1. Ohta M, Tokuda Y, Suzuki Y, Kubota M, Watanabe T, Fujii H,

et al. A case with HER2-overexpressing breast cancer completely

responded to humanized anti-HER2 monoclonal antibody. Jpn J

Clin Oncol. 2001;31:553–6.

2. National Comprehensive Cancer Network (NCCN). http://www.

nccn.org/professionals/physician_gls/default.asp.

3. Pietras RJ, Arboleda J, Reese DM, Wongvipat N, Pegram MD,

Ramos L, et al. HER-2 tyrosine kinase pathway targets estrogen

receptor and promotes hormone-independent growth in human

breast cancer cells. Oncogene. 1995;10:2435–46.

4. Carlomagno C, Perrone F, Gallo C, De Laurentiis M, Lauria R,

Morabito A, et al. c-erb B2 overexpression decreases the benefit

of adjuvant tamoxifen in early-stage breast cancer without axil-

lary lymph node metastases. J Clin Oncol. 1996;14:2702–8.

5. Mackey JR, Kaufman B, Clemens M, Bapsy PP, Vaid A, Wardley

A, Tjulandin S, Jahn M, Lehle M, Jones A. Trastuzumab prolongs

progression-free survival in hormone-dependent and HER2-

positive metastatic breast cancer. San Antonio Breast Cancer

Symposium 2006; abstract 3.

6. Nakagami K, Inoue K, Mizutani M, Hozumi Y, Fujiwara Y,

Masuda N, Tsukamoto F, Saito M, Ohashi Y, Sano M, Noguchi

S. Randomized Phase III study of trastuzumab monotherapy

followed by docetaxel and trastuzumab versus the combination of

trastuzumab and docetaxel as first-line treatment in patients with

HER2 positive metastatic breast cancer. San Antonio Breast

Cancer Symposium 2008; abstract 3132.

7. Pegram M, Hsu S, Lewis G, et al. Inhibitory effects of combi-

nations of HER-2/neu antibody and chemotherapeutic agents

used for treatment of human breast cancers. Oncogene. 1999;

18:2241–51.

8. Slamon DJ, Leyland-Jones B, Shak S, Fuchs H, Paton V,

Bajamonde A, et al. Use of chemotherapy plus a monoclonal

antibody against HER2 for metastatic breast cancer that overex-

presses HER2. N Engl J Med. 2001;344:783–92.

9. Buzdar AU, Ibrahim NK, Francis D, Booser DJ, Thomas ES,

Theriault RL, et al. Significantly higher pathologic complete

remission rate after neoadjuvant therapy with trastuzumab, pac-

litaxel, and epirubicin chemotherapy: results of a randomized trial

in human epidermal growth factor receptor 2-positive operable

breast cancer. J Clin Oncol. 2005;23:3676–85.

10. Untch M, Eidtmann H, du Bois A, Meerpohl HG, Thomssen CH,

Ebert A, et al. Cardiac safety of trastuzumab in combination with

epirubicin and cyclophosphamide in women with metastatic

breast cancer: results of a phase I trial. Eur J Cancer. 2004;

40:988–97.

systemic disease

hormone receptor positive hormone receptor negative or

hormone receptor positive and symptomatic visceral tumor

trastuzumab+

1st-line 2nd-line 3rd-line

……

chemotherapy

trastuzumab+

1st-line 2nd-line ……

endocrine therapy

trastuzumab+

1st-line 2nd-line 3rd-line

……

chemotherapy

Fig. 3 Algorithm for treatment selection for HER2-positive meta-

static breast cancer

Breast Cancer (2009) 16:295–300 299

123

11. Theodoulou M, Campos SM, Batist G, Winer E, Norton L, Hudis

C, et al. TLC D99 (D, Myocet) and Herceptin (H) is safe in

advanced breast cancer (ABC): final cardiac safety and efficacy

analysis. Proc Am Soc Clin Oncol. 2002;21:55a. abstract.

12. Cortes J, Dicosimo S, Climent MA, Cortes-Funes H, Lluch A,

Gascon P, et al. Nonpegylated liposomal doxorubicin (TLC-

D99), paclitaxel, and trastuzumab in HER-2-overexpressing

breast cancer: a multicenter phase I/II Study. Clin Cancer Res.

2009;15:307–14.

13. Suzuki T, Minamide S, Iwasaki T, Yamamoto H, Kanda H.

Cardiotoxicity of a new anthracycline derivative (SM-5887)

following intravenous administration to rabbits: comparative

study with doxorubicin. Invest New Drugs. 1997;15:219–25.

14. Tokuda Y, Umemura S, Saito Y, Suzuki Y. Enhanced anti-tumor

effect of trastuzumab combined with less cardiotoxic anthracy-

cline, amrubicin, in HER2 positive human cancer xenografts in

athymic mice. J Clin Oncol. 2008;26:abstract 14641.

15. Marty M, Cognetti F, Maraninchi D, Snyder R, Mauriac L,

Tubiana-Hulin M, et al. Randomized phase II trial of the efficacy

and safety of trastuzumab combined with docetaxel in patients

with human epidermal growth factor receptor 2-positive meta-

static breast cancer administered as first-line treatment: the

M77001 study group. J Clin Oncol. 2005;23:4265–74.

16. Bontenbal M, Seynaeve C, Stouthard J, Bos M, Braun H,

Erdkamp FL, et al. Randomized study comparing efficacy/toxicity

of monotherapy trastuzumab followed by monotherapy docetaxel

at progression, and combination trastuzumab/docetaxel as first-

line chemotherapy in Her2-neu positive, metastatic breast cancer

(HERTAX study). J Clin Oncol. 2008;26:44s. abstract 1014.

17. Hayes D. Systemic therapy for HER2-positive metastatic breast

cancer. UpToDate version 16.3.

18. Burstein HJ, Keshaviah A, Baron A, Hart R, Lambert-Falls R,

Marcom PK, et al. Trastuzumab and vinorelbine or taxane che-

motherapy for HER2 ? metastatic breast cancer: the TRAVI-

OTA study. J Clin Oncol. 2006;24:18s. abstract 650.

19. Fujimoto-Ouchi K, Sekiguchi F, Mori K. Preclinical study of

continuous administration of trastuzumab as combination therapy

after disease progression with trastuzumab monotherapy. Proc

Amer Assoc Cancer Res. 2005;46:abstract 5062.

20. Von Minckwitz G, Zielinski C, Maarteense E, Vogel P, Schmidt M,

Eidtmann H, et al. Capecitabine vs. capecitabine ? trastuzumab in

patients with HER2-positive metastatic breast cancer progressing

during trastuzumab treatment: The TBP phase III study (GBG 26/

BIG 3-05). J Clin Oncol. 2008;26:47s. abstract 1025.

21. O’Shaughnessy J, Blackwell KL, Burstein H, Storniolo AM,

Sledge G, Baselga J, et al. A randomized study of lapatinib alone

or in combination with trastuzumab in heavily pretreated

HER2 ? metastatic breast cancer progressing on trastuzumab

therapy. J Clin Oncol. 2008;26:44s. abstract 1015.

22. Tokuda Y, Ohnishi Y, Shimamura K, Iwasawa M, Yoshimura M,

Ueyama Y, et al. In vitro and in vivo anti-tumor effects of a

humanized monoclonal antibody against c-erbB-2 product. Br J

Cancer. 1996;73:1362–5.

300 Breast Cancer (2009) 16:295–300

123