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Molecular Oncology, Markers, Clinical Correlates |
-1-Acid Glycoprotein As an Independent Predictor for Treatment Effects and a Prognostic Factor of Survival in Patients with Non-small Cell Lung Cancer Treated with Docetaxel1
Aventis Pharma, Drug Metabolism and Pharmacokinetics [R. B., N. V., G. R. R.], Statistics [R. O.], and Clinical Research Department [J. B., P. C., L. H.], 92165 Antony cedex, France and Collegeville, Pennsylvania, and Comprehensive Thoracic Oncology Program, Dartmouth Hitchcock Medical Center, Lebanon, New Hampshire [J. R. R.]
| ABSTRACT |
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Experimental design: The data were collected from 180 NSCLC patients enrolled in six docetaxel Phase II studies at a dose of 100 mg/m2. Clinical end points for this study were safety reported as the first course adverse events requiring dose reduction, and efficacy was measured by response rate and survival. The independent variables included docetaxel dose, individual estimates of clearance, area under the plasma concentration time curve, extent of previous treatment, and covariables related to the patients demographics, extent of disease, and performance status. The data were analyzed using a logistic regression model for response and severe adverse events and a Cox multivariate regression model for survival.
Results: Docetaxel exposure as measured by the area under the plasma concentration time curve was the only significant predictor (P < 0.0001) of severe toxicity during the first course of therapy. Baseline
1-acid glycoprotein (AAG) was the only significant predictor of response with an odds ratio of 0.44 for changes in AAG from 1.11 to 1.85 grams/liter (P = 0.0039). Cumulative dose, AAG, and extent of disease were independent predictors of survival (P < 0.005). The median survival varied from 15.6 months for patients with a low AAG (AAG
1.11 grams/liter) to 5.5 months for patients with a high AAG (AAG
1.85 grams/liter).
Conclusion: AAG appears to be an independent predictor of response and a major objective prognostic factor of survival in patients with NSCLC treated with docetaxel chemotherapy.
| INTRODUCTION |
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From this large data set of 640 patients with advanced solid tumors enrolled in 24 Phase II studies of docetaxel, the first cycle pharmacokinetic parameters of systemic CL or AUC and baseline AAG level were found to be significant independent predictors of hematologic adverse events (grade 4 neutropenia and febrile neutropenia). In addition, docetaxel exposure, as measured by the first-dose AUC, and baseline AAG were also predictors of time to progression of disease in NSCLC patients (3) . AAG appears to be an important modulator of docetaxel pharmacokinetics and pharmacodynamics.
The biological functions of AAG are poorly understood; it is an acute phase protein, and its plasma level increase as a response to inflammation is triggered by cytokines (e.g., interleukin 6; Ref. 4 ). As a consequence, AAG levels vary in many physiological states (i.e., age and pregnancy) and pathological conditions (i.e., liver cirrhosis, renal disease, and cancer; Refs. 5 and 6 ). Under physiological conditions, the plasma level of AAG varies from 0.36 to 1.46 grams/liter (6) . Increased levels have been reported in all of the pathological conditions already mentioned and, in particular, in NSCLC patients (5) . Acute-phase proteins and AAG in particular have long been associated with poor prognostics in many conditions, including cancer. Many reports of AAG as a "marker of disease" have been published in the 1970s and 1980s (7, 8, 9, 10) . Significant elevations of AAG were found in patients with active lung and gastro-intestinal cancers compared with patients with inactive disease. Moreover, in patients with colorectal cancer treated with 5-fluorouracil, AAG correlated with a response to therapy, with lower AAG levels in responding patients and higher AAG levels in patients with progressive disease (8) . In another study (9) , AAG has been shown to be highly sensitive and specific in the detection of lung cancer. In this study, the normalization of AAG during chemotherapy correlated with a prolonged relapse-free survival.
Increased AAG levels associated with advanced tumors limited the efficacy of STI571, a tyrosine kinase inhibitor, in a mouse model of leukemia (11) . This effect has been proposed as a mechanism of resistance to this agent. However, these findings could not be confirmed in another study (12) . The binding of UCN-01, another protein kinase inhibitor, to AAG modulated the PK and effects of this agent (13) . Similar observations have been made with protease inhibitors used in the treatment of human immunodeficiency virus (14 , 15) .
AAG binds a wide variety of basic, neutral, and acidic drugs (5) . Erythromycin competes with STI571 for AAG binding and can therefore modulate the activity of this agent (11) . Docetaxel is highly bound to plasma protein. Its high-affinity binding to AAG is responsible for a decrease in free fraction with high AAG levels (16) .
The goal of this study was to further assess the effect of AAG on the clinical response and survival in patients with NSCLC treated with docetaxel.
| PATIENTS AND METHODS |
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2 x upper limit of normal). According to the study design, patients may have received previous treatment. The initial docetaxel dose for most patients was 100 mg/m2 given as a 1-h infusion every 3 weeks. Dose reduction of 25% or delay of subsequent courses of therapy was permitted, based on the grade of toxicity observed. These studies were part of the 22 Phase II studies reported in a previous PK/PD analysis of docetaxel. The studies were conducted at multiple centers in Europe and the United States (3)
. These clinical trials were approved by local ethics committees or institutional review boards.
Pharmacokinetic Data
Pharmacokinetic assessment was performed at the first cycle of treatment. The design of the sampling strategy has been published previously by Bruno et al. (3)
. In brief, the sampling strategy consisted of four different sampling schedules of three sampling times, which were assigned randomly to patients on study entry. Docetaxel was assayed in plasma samples using high-performance liquid chromatography and UV detection after solid-phase extraction (23)
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From the population pharmacokinetic parameters (2) , Bayesian methods were used to estimate each individuals pharmacokinetic parameters from the patients plasma concentrations (24) . The NONMEM computer program was used for these studies (version IV, level 2.0; Ref. 25 ). The PK model used a three-compartment structural model with first-order elimination, and the PK parameters considered for this analysis were CL (obtained using the Bayesian estimation) and AUC (calculated from CL).
Clinical End Points
The following clinical end points were considered for this analysis.
Safety.
Febrile neutropenia, infections, grade 3/4 stomatitis, grade 3/4 diarrhea, and severe asthenia reported during the first course of therapy were considered as safety end points. These end points of acute toxicity were only considered at first course because we wanted to study the drug exposure effects, and pharmacokinetic data were only collected at the first course of treatment. These parameters were selected as they typically require dose reduction or treatment delay. Stomatitis and diarrhea were defined and graded using the Common Toxicity Criteria of United States National Cancer Institute, whereas COSTART classification was used for asthenia. Febrile neutropenia was defined as body temperature > 38°C with concomitant National Cancer Institute grade 4 neutropenia (neutrophil count < 500/µl) requiring antibiotics and/or hospitalization.
Because of the few patients and low incidence of severe adverse events, these safety end points were pooled for analysis.
Response Rate.
Response was assessed every 2 weeks during treatment. The patients were considered to be responders when they experienced either a partial or complete response using standard criteria. Patients with minor responses (<50% reduction in tumor size), stable disease, and patients with disease progression were considered as nonresponders. Responses had to be confirmed after a minimum of 4 weeks and were reviewed by an independent panel.
Survival.
Survival was calculated from the date of the first docetaxel infusion to the date of death, last contact for patients lost to follow-up, or a cutoff date for patients alive at the time of closure of the data set.
| Data Analysis |
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A logistic regression analysis was used to relate binary end points, such as the incidence of severe adverse events and response rate, to the independent variables, whereas a Cox regression was used for the survival analysis. Cumulative docetaxel dose was the only time-dependent covariate used in the Cox model. Univariate and multivariate analyses were conducted. The multivariate model involved a stepwise selection of covariates starting from the null model. Significance levels for variable entry or removal at each step in the development of the multivariate model were P < 0.1 and <0.05, respectively. The median survival was estimated using the Kaplan-Meier method. Analyses were carried out using the SAS software (SAS version 6.12; SAS Institute, Inc., Cary, NC).
| RESULTS |
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| PK/PD |
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2-fold greater for a change in AUC from 4.2 to 6.5 µg/h/ml. An increase in AAG from 1.11 to 1.85 grams/liter resulted in a
50% reduction in the odds of experiencing one toxicity event.
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1.11 grams/liter, n = 46) and 15.9% (95% CI: 6.730.1%) for patients with a high AAG (AAG
1.85 grams/liter, n = 44).
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Survival.
The most significant univariate predictors of survival were cumulative dose, baseline AAG, and number of sites of disease (P < 0.0001). CL or AUC, previous radiotherapy, gender, and performance status were also significant predictors of survival (P < 0.05). The risk of death decreased as the cumulative dose of docetaxel increased. However, an increased risk of death was observed for patients with higher baseline AAG, two or more sites of disease, low CL or high AUC at first cycle, poor performance status, female gender, and for patients having received previous therapy.
Only cumulative dose, AAG, and two or more disease sites remained significant in the multivariate analysis (Table 5)
. The risk of death decreased by 20% for each additional cycle of treatment and roughly doubled in patients with a high AAG (1.85 grams/liter) compared with patients with a low AAG (1.11 grams/liter) and in patients with two or more sites of disease.
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1.11 grams/liter, n = 46) to 5.5 months in high AAG patients (AAG
1.85 grams/liter, n = 44). Patients with intermediate AAG values (n = 90) had a median survival time of 9.2 months (Fig. 1)
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| DISCUSSION |
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In our patient population, with a median AAG of 1.42 mg/liter, roughly half of the patients had a level exceeding the maximum seen in healthy subjects. The finding that, during docetaxel treatment of patients with advanced NSCLC, high baseline AAG levels are associated with a lower response rate and disease progression (3) , and shorter survival is consistent with the findings of previous studies where high levels of AAG have been reported to modulate the biological activity of several drugs. High AAG levels are associated with a decrease of the free fraction (fu) of docetaxel (16) . This effect may result in a restriction of free docetaxel distribution in patients with high AAG levels. This pharmacokinetic effect may be an important predictor of safety end points, particularly those related to hematological adverse events. This pharmacokinetic effect may also play an important role in decreasing the overall pharmacologic activity of docetaxel (including tumor shrinkage). These effects of AAG on docetaxel pharmacokinetics and pharmacodynamics may also contribute to the shorter survival observed in this study for patients with high baseline AAG. However, the shorter survival is very likely to be related to the poor prognosis of patients with high AAG (5 , 7, 8, 9) . Several factors have limited the usefulness of AAG as a prognostic factor in cancer. Primarily, levels of this protein are associated with a high frequency of nonspecific changes (5) . In addition, AAG is a heterogeneous glycoprotein with up to four glycoforms, each of which may have a different pathophysiological meaning (27) .
Overall, the observation that patients with high AAG levels demonstrate decreased docetaxel treatment effects both in toxicity and efficacy and shorter survival is of interest. A clinical trial simulation was conducted recently to determine whether patients with high AAG levels might tolerate a higher dose of docetaxel (125 mg/m2 versus 100 mg/m2) and benefit by achieving improved efficacy and longer survival (28) . This simulation, however, did not show a benefit in any of the clinically relevant parameters of efficacy (time to progression) and survival for the patients receiving 125 mg/m2. The predicted median time to progression in this patient population with high AAG was only 8.5 weeks; therefore, these patients could only be treated for a median of three cycles and did not benefit from the dose intensification.
AAG is one covariate in NSCLC that appears to impact on time to disease progression, survival, and response to docetaxel chemotherapy. These observations are likely related to the high-affinity protein binding effects of this drug to AAG and the different prognosis of patients with various levels of AAG. A more complete understanding of the PK/PD interactions between drugs and AAG warrants additional studies.
| FOOTNOTES |
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1 Presented in part at the 34th Annual Meeting of the American Society of Clinical Oncology, May 1619, 1998, Los Angeles, CA. ![]()
2 Present address: Genentech, Inc., South San Francisco, CA. ![]()
3 To whom requests for reprints should be addressed, at Oncology Clinical Research and Development, Aventis pharma SA, tri E2/325, 20 Avenue Raymond Aron, 92165 Antony cedex, France. Phone: 33 1 55 71 73 56; Fax: 33 1 55 71 64 95. ![]()
4 Present address: Elan Pharmaceuticals, Inc., Princeton, NJ. ![]()
5 Present address: MedImmune, Blue Bell, PA. ![]()
6 Present address: Viropharma, Exton, PA. ![]()
7 The abbreviations used are: PK/PD, pharmacokinetics/pharmacodynamics; AAG,
1-acid glycoprotein; AUC, area under the plasma concentration time curve; CI, confidence interval; NSCLC, non-small cell lung cancer; CL, clearance. ![]()
Received 4/16/02; revised 11/11/02; accepted 11/18/02.
| REFERENCES |
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1-acid glycoprotein (AAG) concentration in health. Br. J. Clin. Pharmacol., 20: 500-502, 1985.[Medline]
1-acid glycoprotein to monitor therapy of cancer patients. J. Natl. Cancer Inst. (Bethesda), 71: 25-30, 1983.
-1-acid glycoprotein. Cancer Res., 44: 5415-5421, 1984.
1-acid glycoprotein in the in vivo resistance of human BCR-ABL+ leukemic cells to the Abl inhibitor STI571. J. Natl. Cancer Inst. (Bethesda), 92: 1641-1650, 2000.
1-acid glycoprotein expressed in the plasma of chronic myeloid leukemia patients does not mediate significant in vitro resistance to STI571. Blood, 99: 713-715, 2002.
1-acid glycoprotein. Pharm. Res., 17: 553-564, 2000.[CrossRef][Medline]
1 acid glycoprotein. J. Infect. Dis., 171: 559-565, 1995.[Medline]
1-acid glycoprotein as marker of inflammation and cancer. Clycoconjugate J., 12: 241-247, 1995.
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