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Molecular Oncology, Markers, Clinical Correlates |
1 Pathology Division, National Cancer Center Research Institute East, Chiba, Japan; 2 Division of Thoracic Oncology, National Cancer Center Hospital East, Chiba, Japan; 3 Internal Medicine and Thoracic Oncology Division, National Cancer Center Hospital, Tokyo, Japan
| ABSTRACT |
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Experimental Design: Between June 2002 and October 2003, 36 adenocarcinoma patients who experienced a relapse after surgical resection were treated with gefitinib at our hospital. The histologic patterns of the tumors were divided into four distinctive subtypes according to the revised World Health Organization histologic classification, and the dominant histologic subtype for the maximum cut surface of each resected specimen was documented. Association between the response to gefitinib and the clinicopathological features or immunohistochemical expression of epidermal growth factor receptor (EGFR), phosphorylated EGFR, or c-erbB-2 were then investigated.
Results: A significant association between the response to gefitinib and dominant papillary subtype findings was observed (P = 0.0021); the survival time of papillary subtype patients was also significantly prolonged compared with that of non-papillary subtype patients (P = 0.03). No other clinicopathological features or the expression of EGFR, phosphorylated EGFR, or c-erbB-2 were associated with the response to gefitinib.
Conclusions: The results of the present study indicate that dominant papillary subtype findings of lung adenocarcinomas can be an important predictor of the response to gefitinib. Thus, this type of adenocarcinoma might be susceptible to postoperative adjuvant treatment with gefitinib.
| INTRODUCTION |
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Epidermal growth factor receptor (EGFR) has been shown to play an important role in the growth of many solid tumors and is overexpressed in approximately 40 to 80% of NSCLCs (7, 8, 9)
. Furthermore, the overexpression of EGFR has been associated with a poor prognosis in several studies on lung cancer (10
, 11) . EGFR activation occurs when ligands, such as epidermal growth factor, transforming growth factor-
, or amphiregulin, bind to its extracellular domain, resulting in cell proliferation, angiogenesis, metastasis, and antiapoptosis (8
, 9)
. Gefitinib (IRESSA; AstraZeneca, Osaka, Japan) is an orally active, selective EGFR tyrosine kinase inhibitor that blocks downstream of the EGFR signal transduction pathway (12)
. In this context, gefitinib has a quite different profile from chemotherapeutic agents that have ever been used.
After phase I studies, two multicenter, randomized, double-blind phase II studies (IDEAL1, ref. 13 ; IDEAL2, ref. 14 ) were carried out to evaluate the tolerability and efficacy of gefitinib in patients with advanced NSCLC who had been treated previously with platinum-based combination chemotherapy. In total, 426 patients were enrolled in the two studies, and all of the patients had been treated previously with platinum-based combination chemotherapy. In both studies, the administration of two different gefitinib dosages (250 mg/day and 500 mg/day) were compared. No significant differences in efficacy were seen between the two dosages, but the 250 mg/day treatment was better tolerated than the 500 mg/day treatment in both studies. For the 250 mg/day gefitinib arms, the response rates were 18.4% and 12.0% in IDEAL1 and IDEAL2, respectively.
The results of IDEAL1 showed that gefitinib was significantly more effective for the treatment of adenocarcinomas than for other histologies (odds ratio, 3.45) and was also more effective in females than in males (odds ratio, 2.65). These findings were unexpected, given the mechanism of the drug, because squamous cell carcinomas are known to overexpress EGFR, the target of gefitinib, to a greater degree than adenocarcinomas. On the other hand, gefitinib-induced severe acute interstitial pneumonia resulting in a high mortality rate is a serious social problem in Japan (15) . Although the precise mechanism of gefitinibs action is not yet completely understood, clinically it is more important to identify favorable characteristics in the treatment with gefitinib.
Gefitinib has been confirmed to be significantly effective for the treatment of adenocarcinomas, and some investigators have reported that gefitinib is especially effective in adenocarcinomas with bronchiolo-alveolar features (16 , 17) . To the best of our knowledge, however, these studies only examined biopsy specimens, and no studies examining surgical specimens have been done. Lung cancer is generally characterized by histologic heterogeneity; thus, studies examining histologic features should be done using surgically resected specimens.
In this study, we investigated the clinicopathological and immunohistochemical features of surgically resected adenocarcinoma specimens from patients who were subsequently treated with gefitinib after relapse to identify any characteristics that were associated with a favorable response to gefitinib.
| PATIENTS AND METHODS |
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Pathological Studies.
All surgical specimens were fixed with 10% formalin or absolute methanol and embedded in paraffin. The tumors were cut at approximately 5-mm intervals, and serial 4-µm sections were stained with H&E, Alcian blue-periodic acid Schiff method to visualize cytoplasmic mucin production, or Verhoeff van-Gieson method (18)
to visualize elastic fibers. Lymphatic permeation and pulmonary metastases were evaluated on sections stained with H&E. Vascular invasion and pleural invasion were evaluated with the Verhoeff van-Gieson method. Three observers (Y. K., G. I., and K. T.) who were unaware of the clinical data independently reviewed all pathologic slides. The histologic diagnoses were based on the revised World Health Organization histologic classification (19)
. In addition, the histologic subtypes and percentage of each subtype present in the tumor were evaluated with the maximum cut surface of the tumor. The histologic patterns were divided into four distinctive subtypes: bronchioloalveolar carcinoma (BAC), acinar subtype, papillary subtype, and solid adenocarcinoma with mucin. The dominant subtype of each tumor was then documented. Tumor size was measured as the maximal diameter on the cut section of the lung. The pathologic stage was determined according to the classification of the Union Internationale Contre le Cancer (20)
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Immunohistochemistry.
Tissue blocks were cut into 4-µm sections and mounted on silane-coated slides (Matsunami, Tokyo, Japan). The slides were then deparaffinized in xylene, dehydrated in a graded alcohol series, and blocked for endogenous peroxidase with 3% H2O2 in absolute methanol. After microwave pretreatment in citrate buffer (pH 6.0) at 95°C for 20 minutes, immunostaining was done at 4°C overnight with a mouse monoclonal antihuman EGFR (Novocastra, Newcastle, United Kingdom; ref. 21
) at a dilution of 1:10, a mouse monoclonal antihuman phosphorylated EGFR (provided by Kyowahakko, Tokyo, Japan) that recognizes Try-1173 of the activated EGFR at a dilution of 1:10. As for the use of the antihuman phosphorylated EGFP (p-EGFR), a synthetic peptide (CGSTENAEpYLRVAPQSS), the amino acid sequence of which corresponds to COOH-terminal region of human EGFR, was used as an immunogen to generate a monoclonal antibody specific for the tyrosine-phosphorylated EGFR molecule. Obtained monoclonal antibody (KM2911) was further characterized by ELISA, Western blot assay, and immunohistochemical staining to verify the specificity and sensitivity. Furthermore, we compared the immunostaining of KM2911 with that of another monoclonal antibody against tyrosine-phosphorylated EGFR (MAB3052, Chemicon International, Inc., Temecula, CA) and confirmed the same specificity and sensitivity. The tissues were then exposed to DAKO EnVision+ (DAKO, Glostrup, Denmark) at room temperature for 30 minutes. Staining was visualized by exposure to 3,3'-diaminobenzidine for 3 to 5 minutes. For c-erbB-2, mouse monoclonal antihuman c-erbB-2 (Ventana, Frankfurt, Germany) and the NX/EX automatic stainer (Ventana) were used (22)
As positive controls, lung adenocarcinoma specimen, which had been surgically resected at our hospital and had been determined previously to be strongly positive, was used for the EGFR and p-EGFR experiments. Breast cancer specimen, also surgically resected at our hospital and known to be strongly positive, was used for the c-erbB-2 experiment. Negative controls for each antibody were done with nonimmune serum instead of the primary antibodies. The expression of each receptor was scored as follows: = no discernible staining, or <10% of cells stained; 1+ = >10% of cytoplasmic staining, or plasma membrane staining with weak intensity; 2+ = >10% of plasma membrane staining with moderate intensity; and 3+ = >10% of plasma membrane staining with strong intensity. Staining of 2+ and 3+ were evaluated as positive. As for EGFR and p-EGFR, no universal evaluation criteria exist at present; therefore, we applied the same criteria as c-erbB-2. Although this evaluation criteria basically followed HercepTest (23)
, we added some modification to evaluate cytoplasmic staining.
Statistical Analysis.
All statistical analyses were done with the statistical program StatView, version 5.0 (Abacus Concepts, Berkley, CA). The significance of the relationships between individual clinicopathologic factors; the expression of EGFR, p-EGFR, and c-erbB-2; and a univariate analysis with the Fisher exact probability test was used to evaluate the response to gefitinib. A multivariate regression analysis was conducted according to the Cox proportional hazard model. Kaplan-Meier method was used to calculate survival rates, and a log-rank test was used to evaluate the statistical significance of any differences. A P value of less than 0.05 was considered significant.
| RESULTS |
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| DISCUSSION |
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Clinical factors, including age, gender, performance status, smoking history, previous chemotherapy, and recurrence site, were not associated with the response to gefitinib in this study. The immunohistochemical expression profiles of EGFR, p-EGFR, and c-erbB-2 were also not associated with the response. However, both the dominant histologic subtype and the presence of pleural invasion differed significantly between responders and non-responders according to a univariate analysis, whereas a multivariate analysis revealed that only the dominant histologic subtype was a significant factor. In other words, a dominant papillary subtype was the feature that most favored a response to gefitinib, and the survival period of patients with this feature was significantly longer than that of patients with non-papillary subtypes.
The finding that gefitinib is more effective in papillary subtype lesion is of great interest. Drug delivery might be more effective in this histologic subtype, because cancer cells with a papillary structure usually line the fibrovascular stroma. In an in vitro and in vivo study, Hirata et al. (30) showed that the antitumor effect of gefitinib was partly mediated by the inhibition of tumor angiogenesis through direct effects on microvascular endothelial cells that express EGFR. In the papillary subtype, this direct effect on microvascular endothelial cells might be more efficient than in other subtypes.
The results of the present immunohistochemical study suggest that EGFR expression is not a useful predictor of the response to gefitinib. Recently, Paez et al. (31) and Lynch et al. (32) originally showed that EGFR mutations may predict sensitivity to gefitinib. These epoch-making studies arouse an interest about association of EGFR mutations with histologic subtypes.
In the present study, 9 patients (28%) were positive for EGFR and 14 (40%) were positive for p-EGFR. It seems somewhat strange that the positive rate of p-EGFR surpassed that of EGFR; however, we consider that it is simply because the p-EGFR antibody was more sensitive than the EGFR antibody.
The response rate of our study was high even for adenocarcinoma patients; however, patients were not selected at a point of administration of gefitinib for the most likely respond and patients selection in the present study strictly followed the definition described in the Patients and Methods section. The relatively high proportion of female (53%) and never-smoker (56%) might lead to this result.
A micropapillary pattern (MPP) of lung adenocarcinoma, which was not included in the revised World Health Organization histologic classification, was first described by Silver and Askin (33) . Lung adenocarcinomas characterized by MPP are thought to be more likely to metastasize and have a poor prognosis (34 , 35) . Most MPP-positive adenocarcinoma cases were included in the papillary subtype in the present study. Miler et al. (16) reported that a never-smoker status was a significant predictor of the response to gefitinib, whereas Wu et al. (36) reported that all of their patients who achieved a complete response with gefitinib had bilateral diffuse small pulmonary metastases. Both a never-smoker status and diffuse pulmonary metastases are frequently observed in MPP-positive adenocarcinoma (35) . These reports, combined with the results of the present study, suggest that gefitinib might be effective against MPP-positive adenocarcinoma. In fact, MPP-positive adenocarcinomas (12 cases) were more sensitive to gefitinib than MPP-negative lesions (24 cases) in the present study (P = 0.0328).
In conclusion, the results of the present study indicate that a dominant papillary adenocarcinoma subtype can be an important predictor of the response to gefitinib. Even in patients with pathologic stage IA NSCLC who undergo a complete resection, the 5-year survival rate is about 70% at best (2) . Therefore, adenocarcinoma with a dominant papillary subtype might be susceptible to postoperative adjuvant treatments with gefitinib. However, the precise mechanism of how this agent works is still obscure. Additional studies are needed to reveal the relation between the sensitivity to gefitinib and the histology of papillary subtype.
| FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Requests for reprints: Atsushi Ochiai, Pathology Division, National Cancer Center Research Institute East, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan, Phone: 81-4-7133-1111; Fax: 81-4-7131-4724; E-mail: aochiai{at}east.ncc.go.jp
Received 4/26/04; revised 7/12/04; accepted 7/19/04.
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