Biological Predictors of Response to Radiotherapy in Head and Neck Cancer: Recent Advances and Emerging Perspectives

Altered Fractionation Radiotherapy in Head and Neck Cancer: Clinical Issues and Pitfalls of “Evidence-Based Medicine”

The authors present a critical appraisal of the biological bases of altered fractionation and a brief overview of published randomized trials with conventional fractionation as the control arm, reviews and meta-analysis on altered fractionation radiotherapy in head and neck cancer. The major controversial issues emerging from these studies are reviewed and the limiting factors which so far have prevented the widespread use of altered fractionation regimens in current clinical practice are analyzed. Future perspectives regarding predictive biological assays for patient selection and the integration of altered fractionation regimens with radiochemotherapy protocols, biomodulators and novel radiotherapy techniques are also reviewed and summarized.

HPV-associated differential regulation of tumor metabolism in oropharyngeal head and neck cancer

HPV-positive oropharyngeal cancer patients experience significantly lower locoregional recurrence and higher overall survival in comparison with HPV-negative patients, especially among those who received radiation therapy. The goal of the present study is to investigate the molecular mechanisms underlying the differential radiation sensitivity between HPV-negative and HPV-positive head and neck squamous cell carcinoma (HNSCC). Here, we show that HPV-negative HNSCC cells exhibit increased glucose metabolism as evidenced by increased production of lactate, while HPV-positive HNSCC cells effectively utilize mitochondrial respiration as evidenced by increased oxygen consumption. HPV-negative cells express HIF1α and its downstream mediators of glucose metabolism such as hexokinase II (HKII) and carbonic anhydrase IX (CAIX) at higher levels, while the expression level of cytochrome c oxidase (COX) was noticeably higher in HPV-positive HNSCC. In addition, the expression levels of pyruvate dehydrogenase kinases (PDKs), which inhibit pyruvate dehydrogenase activity, thereby preventing entry of pyruvate into the mitochondrial tricarboxylic acid (TCA) cycle, were much higher in HPV-negative HNSCC compared to those in HPV-positive cells. Importantly, a PDK inhibitor, dichloroacetate, effectively sensitized HPV-negative cells to irradiation. Lastly, we found positive interactions between tonsil location and HPV positivity for COX intensity and COX/HKII index ratio as determined by immunohistochemical analysis. Overall survival of patients with HNSCC at the tonsil was significantly improved with an increased COX expression. Taken together, the present study provides molecular insights into the mechanistic basis for the differential responses to radiotherapy between HPV-driven vs. spontaneous or chemically induced oropharyngeal cancer.

Differential effects of patient-related factors on the outcome of radiation therapy for rectal cancer

OBJECTIVE

The objective of this study was to investigate whether cancer specific survival in rectal cancer patients is affected by patient-related factors, conditional on radiation treatment.

METHODS

359 invasive rectal cancer patients who consented and provided questionnaire data for a population-based case-control study of colorectal cancer in Metropolitan Detroit were included in this study. Their vital status was ascertained through to the population-based cancer registry. Hazard ratios (HR) for cancer specific and other deaths and 95% confidence intervals (CIs) were calculated according to selected patients' characteristics, stratified by radiation status, using joint Cox proportional hazards models.

RESULTS

A total of 159 patients were found to be deceased after the median follow-up of 9.2 years, and 70% of them were considered to be cancer specific. Smoking and a history of diabetes were associated with an increased probability of deaths from other causes (HR 3.20, 95% CI 1.72-5.97 and HR 2.02, 95% CI 0.98-4.16, respectively), while regular use of non-steroidal anti-inflammatory drugs (NSAIDs) was inversely correlated with cancer-specific mortality (HR 0.50, 95% CI 0.30-0.81). Furthermore, the associations of smoking and NSAIDs with the two different types of deaths (cancer vs others) significantly varied with radiation status (P-values for the interactions= 0.014 for both). In addition, we observed a marginally significantly reduced risk of cancer specific deaths in the patients who had the relative ketogenic diet overall (HR=0.49, 95% 0.23-1.02).

CONCLUSION

Further research is warranted to confirm these results in order to develop new interventions to improve outcome from radiation treatment.

Immunotherapy and targeted therapy for cervical cancer: an update

The prognosis of patients with metastatic cervical cancer is poor with a median survival of 8-13 months. Despite the potency of chemotherapeutic drugs, this treatment is rarely curative and should be considered palliative only. In the last few years, a better understanding of Human papillomavirus tumor-host immune system interactions and the development of new therapeutics targeting immune check points have renewed interest in the use of immunotherapy in cervical cancer patients. Moreover, next generation sequencing has emerged as an attractive option for the identification of actionable driver mutations and other markers. In this review, we provide background information on the molecular biology of cervical cancer and summarize immunotherapy studies, targeted therapies, including those with angiogenesis inhibitors and tyrosine kinase inhibitors recently completed or currently on-going in cervical cancer patients.

Radio-sensitization by Piper longumine of human breast adenoma MDA-MB-231 cells in vitro

BACKGROUND

The current study investigated the effects of Piper longumine on radio-sensitization of human breast cancer MDA-MB-231 cells and underlying mechanisms.

MATERIALS AND METHODS

Human breast cancer MDA-MB-231 cells were cultured in vitro and those in logarithmic growth phase were selected for experiments divided into four groups: control, X-ray exposed, Piper longumine, and Piper longumine combined with X-rays. Conogenic assays were performed to determine the radio-sensitizing effects. Cell survival curves were fitted by single-hit multi-target model and then the survival fraction (SF), average lethal dose (D0), quasi-threshold dose (Dq) and sensitive enhancement ratio (SER) were calculated. Cell apoptosis was analyzed by flow cytometry (FCM).Western blot assays were employed for expression of apoptosis-related proteins (Bc1-2 and Bax) after treatment with Piper longumine and/or X-ray radiation. The intracellular reactive oxygen species (ROS) level was detected by FCM with a DCFH-DA probe.

RESULTS

The cloning formation capacity was decreased in the group of piperlongumine plus radiation, which displayed the values of SF2, D0, Dq significantly lower than those of radiation alone group and the sensitive enhancement ratio (SER) of D0 was1.22 and 1.29, respectively. The cell apoptosis rate was increased by the combination treatment of Piper longumine and radiation. Piper longumine increased the radiation-induced intracellular levels of ROS. Compared with the control group and individual group, the combination group demonstrated significantly decreased expression of Bcl-2 with increased Bax.

CONCLUSIONS

Piper longumine at a non-cytotoxic concentration can enhance the radio-sensitivity of MDA- MB-231cells, which may be related to its regulation of apoptosis-related protein expression and the increase of intracellular ROS level, thus increasing radiation-induced apoptosis.

Phase II trial of cetuximab in the treatment of persistent or recurrent squamous or non-squamous cell carcinoma of the cervix: a Gynecologic Oncology Group study

PURPOSE

The Gynecologic Oncology Group (GOG) conducted a phase II trial to assess the efficacy and tolerability of the anti-EGFR antibody cetuximab, in persistent or recurrent carcinoma of the cervix.

PATIENTS AND METHODS

Eligible patients had cervical cancer, measurable disease, and GOG performance status ≤2. Treatment consisted of cetuximab 400 mg/m(2) initial dose followed by 250 mg/m(2) weekly until disease progression or prohibitive toxicity. The primary endpoints were progression-free survival (PFS) at 6 months and response. The study used a 2-stage group sequential design.

RESULTS

Thirty-eight patients were entered with 3 exclusions, leaving 35 evaluable for analysis. Thirty-one patients (88.6%) received prior radiation as well as either 1 (n=25, 71.4%) or 2 (n=10) prior cytotoxic regimens. Twenty-four patients (68.6%) had a squamous cell carcinoma. Grade 3 adverse events possibly related to cetuximab included dermatologic (n=5), GI (n=4), anemia (n=2), constitutional (n=3), infection (n=2), vascular (n=2), pain (n=2), and pulmonary, neurological, vomiting and metabolic (n=1 each). No clinical responses were detected. Five patients (14.3%; two-sided 90% CI, 5.8% to 30%) survived without progression for at least 6 months. The median PFS and overall survival (OS) times were 1.97 and 6.7 months, respectively. In this study, all patients with PFS at 6 months harbored tumors with squamous cell histology.

CONCLUSION

Cetuximab is well tolerated but has limited activity in this population. Cetuximab activity may be limited to patients with squamous cell histology.

Inhibition of radiation induced migration of human head and neck squamous cell carcinoma cells by blocking of EGF receptor pathways

Background

Recently it has been shown that radiation induces migration of glioma cells and facilitates a further spread of tumor cells locally and systemically. The aim of this study was to evaluate whether radiotherapy induces migration in head and neck squamous cell carcinoma (HNSCC). A further aim was to investigate the effects of blocking the epidermal growth factor receptor (EGFR) and its downstream pathways (Raf/MEK/ERK, PI3K/Akt) on tumor cell migration in vitro.

Methods

Migration of tumor cells was assessed via a wound healing assay and proliferation by a MTT colorimeritric assay using 3 HNSCC cell lines (BHY, CAL-27, HN). The cells were treated with increasing doses of irradiation (2 Gy, 5 Gy, 8 Gy) in the presence or absence of EGF, EGFR-antagonist (AG1478) or inhibitors of the downstream pathways PI3K (LY294002), mTOR (rapamycin) and MEK1 (PD98059). Biochemical activation of EGFR and the downstream markers Akt and ERK were examined by Western blot analysis.

Results

In absence of stimulation or inhibition, increasing doses of irradiation induced a dose-dependent enhancement of migrating cells (p < 0.05 for the 3 HNSCC cell lines) and a decrease of cell proliferation (p < 0.05 for the 3 HNSCC cell lines). The inhibition of EGFR or the downstream pathways reduced cell migration significantly (almost all p < 0.05 for the 3 HNSCC cell lines). Stimulation of HNSCC cells with EGF caused a significant increase in migration (p < 0.05 for the 3 HNSCC cell lines). After irradiation alone a pronounced activation of EGFR was observed by Western blot analysis.

Conclusion

Our results demonstrate that the EGFR is involved in radiation induced migration of HNSCC cells. Therefore EGFR or the downstream pathways might be a target for the treatment of HNSCC to improve the efficacy of radiotherapy.

Overexpression of epidermal growth factor type-1 receptor (EGF-R1) in cervical cancer: Implications for Cetuximab-mediated therapy in recurrent/metastatic disease

OBJECTIVES

To evaluate and compare epidermal growth factor type-1 receptor (EGF-R1) expression in short term and established cervical cancer cell lines generated from primary and metastatic/recurrent sites of disease. To evaluate the sensitivity of cervical cancer cell lines to treatment with a chimeric MAb against EGFR-1 (Cetuximab).

METHODS

EGFR-1 expression was evaluated by flow cytometry on 22 cervical cancer cell lines including 14 primary cervical cancer cell lines obtained from cervical biopsies (11 patients) and recurrent sites of disease (three patients) as well as eight established cell lines. Tumor cell lines were tested for sensitivity to Cetuximab-mediated complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) in 51Cr release assays. Finally, Cetuximab-mediated inhibition of cell proliferation was also tested.

RESULTS

Fourteen out of fourteen (100%) primary tumors and seven out of eight (87.5%) established cervical cancer cell lines expressed EGFR-1 by flow cytometry. Cell lines from recurrent/metastatic sites of disease expressed higher levels of EGFR-1 when compared to those obtained from primary sites (p>0.05). Minimal CDC was detected in the majority of cervical cancer cell lines exposed to complement+/-Cetuximab in the absence of peripheral blood lymphocytes (PBL). In contrast, cervical tumor cell lines were found highly sensitive to Cetuximab-mediated ADCC when challenged with PBL from either healthy donors or cervical cancer patients. Importantly, ADCC was further increased in the presence of complement. Finally, tumor proliferation was significantly inhibited by Cetuximab in all cervical tumors tested.

CONCLUSIONS

EGFR-1 is highly expressed in primary and recurrent cervical tumors. Cetuximab might be a novel and attractive therapeutic strategy in patients harboring chemotherapy-resistant, recurrent, or metastatic cervical cancer.

Metabolic functional imaging for tumor radiosensitivity monitoring

Assessing tumor radiosensitivity before and during radiation therapy can be a crucial element in decision-making with regard to treatment. However, no known non-invasive test is available at present, which allows for a reliable evaluation of the radiosensitivity of a tissue subjected to radiotherapy. Among tests being evaluated, positron emission tomography (PET) is considered to be a promising method. The purpose of this review is to identify the tests and research paths that have recently been explored for the evaluation of tumor response to treatment after isotopic labeling revealed by nuclear imaging. The majority of the explored methodologies are based on the indirect evaluation of the radiosensitivity by cell proliferation or apoptosis, tissue oxygenation or hypoxia, intrinsic radiosensitivity of clonogenic cells, tumor metabolism and angiogenesis. The development of such methods would permit the adoption of a therapeutic regimen with respect to a given radiosensitivity of a tissue. Therefore, a given therapeutic strategy could be readjusted (by associating, for instance, a radiosensitizer of hypoxic cells) or even modified if it proved to be inadequate or when it presents an unfavorable cost-effectiveness ratio. We present here a critical review of the radiotracers revealed by nuclear imaging that are developed for radiosensitivity monitoring.

Évaluation de la radiosensibilité tumorale par l'imagerie fonctionnelle et métabolique : de la recherche à l'application clinique. Revue de la littérature

During the last half of century considerable research on radiosensitivity biomarkers has been published. However, to date there is no non-invasive marker of cellular radiosensitivity identified for clinical routinely use. In this review, the main functional and metabolic imaging isotopic techniques for tumor radiosensitivity that have been explored over the last years are being described. This indirect evaluation fall into 3 topics associated with tumor proliferation rate or apoptosis, tumor hypoxic fraction, neoangiogenesis and the intrinsic radiosensitivity of clonogenic tumor cells. The final objective of the radiosensitivity monitoring during radiotherapy would be to adapt treatment strategy for overcoming the identified radioresistance mechanism such as hypoxia by the addition of radiosensitisers for example. This would allow better tumor control rather than continue inefficient and costly treatment delivery, which in addition could compromise outcome.

Molecularly targeted agents: Their promise as cancer chemopreventive interventions

Molecular medicine has fully entered in to the oncology arena. The development of targeted therapies is one of the major ongoing efforts in cancer treatment. Targeted therapy refers to treatment strategies directed against molecular targets considered to be involved in neoplastic transformation. Such molecularly targeted agents (MTA) are currently under study in all treatment settings including that of chemoprevention, defined as the use of natural or synthetic agents to interrupt the carcinogenic process, to nip tumours in the bud. This review article aims to provide a general overview of the potential use of some of these MTA in the chemoprevention setting.

Accelerated versus conventional fractionated postoperative radiotherapy for advanced head and neck cancer: results of a multicenter Phase III study

PURPOSE

To determine whether, in the postoperative setting, accelerated fractionation (AF) radiotherapy (RT) yields a superior locoregional control rate compared with conventional fractionation (CF) RT in locally advanced squamous cell carcinomas of the oral cavity, oropharynx, larynx, or hypopharynx.

METHODS AND MATERIALS

Patients from four institutions with one or more high-risk features (pT4, positive resection margins, pN >1, perineural/lymphovascular invasion, extracapsular extension, subglottic extension) after surgery were randomly assigned to either RT with one daily session of 2 Gy up to 60 Gy in 6 weeks or AF. Accelerated fractionation consisted of a "biphasic concomitant boost" schedule, with the boost delivered during the first and last weeks of treatment, to deliver 64 Gy in 5 weeks. Informed consent was obtained. The primary endpoint of the study was locoregional control. Analysis was on an intention-to-treat basis.

RESULTS

From March 1994 to August 2000, 226 patients were randomized. At a median follow-up of 30.6 months (range, 0-110 months), 2-year locoregional control estimates were 80% +/- 4% for CF and 78% +/- 5% for AF (p = 0.52), and 2-year overall survival estimates were 67% +/- 5% for CF and 64% +/- 5% for AF (p = 0.84). The lack of difference in outcome between the two treatment arms was confirmed by multivariate analysis. However, interaction analysis with median values as cut-offs showed a trend for improved locoregional control for those patients who had a delay in starting RT and who were treated with AF compared with those with a similar delay but who were treated with CF (hazard ratio = 0.5, 95% confidence interval 0.2-1.1). Fifty percent of patients treated with AF developed confluent mucositis, compared with only 27% of those treated with CF (p = 0.006). However, mucositis duration was not different between arms. Although preliminary, actuarial Grade 3+ late toxicity estimates at 2 years were 18% +/- 4% and 27% +/- 6% for CF and AF, respectively (p = 0.10).

CONCLUSION

Accelerated fractionation does not seem to be worthwhile for squamous cell carcinoma of the head and neck after resection; however, AF might be an option for patients who delay starting RT.

Predicting response to treatment in human cancers of the uterine cervix: sequential biopsies during external beam radiotherapy

PURPOSE

To quantify cervix tumor response via weekly biopsies during therapy.

METHODS AND MATERIALS

Pretreatment and subsequent weekly biopsies (when feasible) were obtained during radical external beam radiotherapy, reduced to single-cell suspensions, and assessed for DNA content by flow cytometry.

RESULTS

Data for 41 patients ranging from FIGO Stage Ib to IIIb and with follow-up >100 days are presented. No clinically significant complications due to the weekly biopsies were noted. The actuarial progression-free survival at 2 years was 68%, with initial pelvic progression observed in 3 patients. The biopsies showed (1) Increased tumor cell proliferation was evident even for the earliest on-treatment samples; (2) Sustained cell yields, coupled with high proliferation 2 or more weeks into treatment, were associated with early failure; and (3) Therapy often "selected" for cell subpopulations that were only minor components of the pretreatment biopsy.

CONCLUSIONS

"Accelerated repopulation" began surprisingly rapidly in cervix tumors after the initiation of chemoradiotherapy, and patients with a sustained cell yield and S-phase fraction 2 or more weeks into therapy were at increased risk for tumor progression. Although clearly implicating tumor (re)growth kinetics as a factor in outcome, the sequential biopsy data also suggested interplay between growth potential and in situ sensitivity to treatment.

Phase I study of the humanized antiepidermal growth factor receptor monoclonal antibody EMD72000 in patients with advanced solid tumors that express the epidermal growth factor receptor

PURPOSE

To investigate the safety and tolerability and to explore the pharmacokinetic and pharmacodynamic profile of the humanized antiepidermal growth factor receptor monoclonal antibody EMD72000 in patients with solid tumors that express epidermal growth factor receptor (EGFR).

PATIENTS AND METHODS

This was a phase I dose-escalation trial of EMD72000 in patients with advanced, EGFR-positive, solid malignancies that were not amenable to any established chemotherapy or radiotherapy treatment. EMD72000 was administered weekly without routine premedication until disease progression or unacceptable toxicity.

RESULTS

Twenty-two patients were treated with EMD72000 at five different dose levels (400 to 2,000 mg/wk). National Cancer Institute common toxicity criteria grade 3 headache and fever occurring after the first infusion were dose limiting at 2,000 mg/wk; thus, the maximum-tolerated dose was 1,600 mg/wk. No other severe side effects, especially no allergic reactions or diarrhea, were observed. Acneiform skin reaction was the most common toxicity, but it was mild, with grade 1 in 11 patients (50%) and grade 2 in three patients (14%). Pharmacokinetic analyses demonstrated a predictable pharmacokinetic profile for EMD72000. Pharmacodynamic studies on serial skin biopsies revealed that EMD72000 effectively abrogated EGFR-mediated cell signaling (eg, reduced phosphorylation of EGFR and mitogen-activated protein kinase), with no alteration in total EGFR protein. Objective responses (23%; 95% CI, 8% to 45%) and disease stabilization (27%; 95% CI, 11% to 50%) were achieved at all dose levels, and responding patients received treatment for up to 18 months without cumulative toxicity.

CONCLUSION

Treatment with EMD72000 was well tolerated and showed evidence of activity in heavily pretreated patients with EGFR-expressing tumors. EMD72000 at the investigated doses significantly inhibited downstream EGFR-dependent processes.

P105 as a prognostic indicator in patients irradiated for locally advanced head-and-neck cancer: a clinical/laboratory correlative analysis of RTOG-9003

PURPOSE

In a previous retrospective study, p105 AD, a proliferation-associated nuclear antigen density (AD), was found to be an independent prognostic factor for patients irradiated for locally advanced head-and-neck cancer. We sought to confirm this finding by analyzing patients entered on RTOG 9003, a Phase III randomized trial of altered fractionation radiotherapy.

METHODS AND MATERIALS

Paraffin blocks of pretreatment biopsies of the primary tumor of patients with Stage III or IV squamous cell carcinoma of the oral cavity, oropharynx, or supraglottic larynx, or Stage II squamous cell carcinoma of the hypopharynx or base of tongue entered on RTOG 9003 were prospectively collected at patient entry. From these paraffin blocks, areas of tumor were selected based on histologic examinations and sectioned. Nuclear suspensions were then prepared and processed for p105 antibody and DNA staining. Flow cytometric quantification of p105 labeling indices and DNA content were then performed for correlation with local-regional control and survival.

RESULTS

Paraffin blocks of tumor biopsies from 457 of 1073 patients entered were available for p105 determination. There was no significant difference in pretreatment characteristics between patients who had paraffin blocks available or not available. The median (range) of p105 labeling index (LI-C), p105 labeling index of cells in S phase (p105 LI-S), and p105 AD were 56 (range: 6-99), 8.255 (range: 0.913-23), and 67 (range: 5-364), respectively. Multivariate analysis of prognostic factors showed that T stage, N stage, Karnofsky performance status, and fractionation schedule were significant for local-regional control (p < 0.0001, 0.0011, <0.0001, and 0.007, respectively) and T stage, N stage, Karnofsky performance status, and tumor grade were significant for survival (p = 0.018, 0.002, <0.0001, and 0.0058, respectively). Neither p105 LI-C nor p105 LI-S nor p105 AD nor DNA ploidy was significant for local-regional control or survival.

CONCLUSION

p105 labeling indices, antigen density, and DNA ploidy do not predict the outcome of patients irradiated for advanced squamous cell carcinomas of the head and neck.

Nuclear medicine imaging to predict response to radiotherapy: a review

PURPOSE

To review available literature on positron emission tomography (PET) and single photon emission computerized tomography (SPECT) for the measurement of tumor metabolism, hypoxia, growth factor receptor expression, and apoptosis as predictors of response to radiotherapy.

METHODS AND MATERIALS

Medical literature databases (Pubmed, Medline) were screened for available literature and critically analyzed as to their scientific relevance.

RESULTS

Studies on 18F-fluorodeoxyglucose PET as a predictor of response to radiotherapy in head-and-neck carcinoma are promising but need confirmation in larger series. 18F-fluorothymine is stable in human plasma, and preliminary clinical data obtained with this marker of tumor cell proliferation are promising. For imaging tumor hypoxia, novel, more widely available radiopharmaceuticals with faster pharmacokinetics are mandatory. Imaging of ongoing apoptosis and growth factor expression is at a very early stage, but results obtained in other domains with radiolabeled peptides appear promising. Finally, for most of the tracers discussed, validation against a gold standard is needed.

CONCLUSION

Optimization of the pharmacokinetics of relevant radiopharmaceuticals as well as validation against gold-standard tests in large patient series are mandatory if PET and SPECT are to be implemented in routine clinical practice for the purpose of predicting response to radiotherapy.

Epidermal growth factor receptor dependence in human tumors: more than just expression?

The epidermal growth factor receptor (EGFR) is a rational target for antitumor strategies. EGFR signaling causes increased proliferation, decreased apoptosis, and enhanced tumor cell motility and neo-angiogenesis. The EGFR is expressed or highly expressed in a variety of human tumors of epithelial origin. ZD1839 (Iressa) is an orally active, selective EGFR tyrosine kinase inhibitor, which blocks signal transduction pathways implicated in proliferation and survival of cancer cells. The lack of a consistent method of evaluating levels of EGFR has caused a disparity in reports of the EGFR as a prognostic factor; however, for some tumors, EGFR is a strong prognostic indicator associated with more aggressive disease and reduced survival. So far, no clear association between EGFR levels and response to EGFR-targeted agents has been found. Preclinical studies with ZD1839 have noted a relationship between the two in some cases, but not others. EGFR signaling may be increased by a number of mechanisms in addition to high expression levels of EGFR, including receptor mutations, heterodimerization with other members of this receptor family such as HER2 (erbB2), increased expression of (autocrine/ paracrine) ligands, and alterations in molecules that control receptor signaling output. Each of these components could be assessed to give an indication of the magnitude of EGFR signal amplification. Evaluation of signaling components downstream from EGFR should provide information on the activation of the EGFR pathway. Until EGFR-based assays predictive of a response to receptor-targeted therapies are available, there is no clear justification for stratifying patients by EGFR status or excluding patients with low EGFR levels from trials with ZD1839 or other EGFR inhibitors.