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Journal of Clinical Oncology, Vol 23, No 6 (February 20), 2005: pp. 1218-1227 © 2005 American Society of Clinical Oncology. DOI: 10.1200/JCO.2005.04.098 Molecular Staging in Stage II and III Melanoma Patients and Its Effect on Long-Term SurvivalFrom the Department of Dermatology of the Charité, Humboldt University; Department of Medicine III, Campus Benjamin Franklin, Charité Berlin, Berlin; Department of Biometry and Medical Documentation and Department of Dermatology, University of Ulm, Ulm; Department of Dermatology, University of Mainz, Mainz, Germany; and Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY Address reprint requests to Christiane Voit, MD, Universitätshautklinik Charité, Humboldt University, Schumannstr 20/21, 10117 Berlin, Germany; e-mail: christiane.voit{at}t-online.de
PURPOSE: To assess the prognostic value of serial reverse transcriptase polymerase chain reaction (RT-PCR) -based measurements of tyrosinase mRNA in peripheral blood of stage II and III melanoma patients. PATIENTS AND METHODS: During routine follow-up of American Joint Committee on Cancer stage II and III melanoma patients, serial testing for tyrosinase transcripts in peripheral blood was performed by RT-PCR. The PCR results were compared with the clinical data collected during the follow-up. RESULTS: Over a period of 3 years, 111 patients (78 stage II and 33 stage III patients) were enrolled, and tyrosinase determinations were carried out. The 6-year disease-specific survival probability was 97% for patients always showing negative RT-PCR results and 67% for patients who tested positive at least once. In a Cox proportional hazards model, the prognostic value of sex, age, site of primary tumor, histologic subtype, stage, Breslow's tumor thickness, Clark level, and the time-dependent variable PCR result was assessed. Patients with a positive RT-PCR test had a distinctly higher risk of dying from melanoma, with a hazard ratio of 12.6 (95% CI, 3.4 to 46.3; P < .001). CONCLUSION: Our study shows a strong association between PCR and disease-specific survival time. Detection of tyrosinase mRNA in peripheral blood may be of similar importance for the clinical course of melanoma as the detection of micrometastatic disease in the sentinel lymph node. Whether a combination of these two factors leads to a better definition of the prognosis of melanoma patients is under investigation in current studies.
Clinical and pathologic factors predicting outcome of melanoma patients have been studied for many years, and the results of these efforts have recently been incorporated into a new staging system of melanoma.1-3 Because no therapy with proven survival benefit has been found for patients with disseminated metastases, the interest arose to develop additional diagnostic tests to monitor hematogenous spread with the goal of early detection of recurrent disease and stratification of patients before enrollment in adjuvant treatment studies. Since the original description of a reverse transcriptase polymerase chain reaction (RT-PCR) method for detection of tyrosinase transcripts in peripheral blood,4 controversial data have been reported in terms of sensitivity of this method and its clinical relevance.5-12 The use of a multiple marker assay was introduced to improve the sensitivity.13 Recurrence-free and disease-specific survival depending on RT-PCR test results have been rarely addressed in homogenous patient cohorts.12,14-16 Therefore, large prospective studies with long-term follow-up in stage II and III melanoma patients are necessary to determine the prognostic value of these assays.16-19 We report on serial tyrosinase RT-PCR measurement in 111 consecutive stage II and III melanoma patients during routine follow-up examination to investigate the prognostic relevance of this assay.
Patient Selection and Staging Patients were enrolled between 1995 and 1998 in accordance with the ethical standards of the Helsinki Declaration. The study was approved by the local ethical committee, and informed consent was provided. At the time of enrollment, the previous version of the American Joint Committee on Cancer staging system for melanoma20 was still in use and applied for our patient population. The routine staging procedure in our institution included physical examination and ultrasound B-scan (regional soft tissues, lymph nodes, and in-transit distances). Ultrasound B-scan of the abdomen and chest x-ray were added once a year for stage II patients and twice a year for stage III patients. Computed tomography or magnetic resonance tomography scans of the brain and thoracic, abdominal, and pelvic organs were performed at first clinic visit and on disease progression. Examination procedures were regarded to be negative if no suspicion of metastatic disease was raised. In case of detection of any suspicious lesion, definitive diagnosis was obtained by fine-needle aspiration cytology21,22 and by subsequent histopathologic examination of surgically removed lesions. All blood sampling was performed concomitantly to tumor staging procedures as patients presented for routine follow-up examinations at scheduled intervals. Patients with primary tumors with a tumor thickness of up to 1.5 mm presented every 6 months, and patients with primary tumors thicker than 1.5 mm and stage III patients presented every 3 months; therefore, the time intervals between consecutive tests performed on patients differed, which is the normal course in follow-up. In an earlier study, we reported our experience with tyrosinase RT-PCR from peripheral blood,23 but the patients of the study reported here are completely different and no subset of the former study.
Blood Sample Processing, RNA Preparation, and Reverse Transcription
Nested Tyrosinase PCR
Quality Control Experiments We had participated in an interlaboratory trial of the European Organisation for Research and Treatment of Cancer for interlaboratory quality assurance.25 Several steps have been taken to detect any cross-over contamination. Before cDNA synthesis, RNAs were purified via silica-gel columns and treated with DNAse. cDNA has always been transcribed in duplicate, with and without superscript enzyme. Each PCR run was controlled by a second run starting from RNA preparation to cDNA synthesis and PCR procedure to confirm results. PCR from RNA as template (ie, PCR without reverse transcription) was carried out to exclude amplification of genomic cDNA. Negative and positive controls were run on each agarose gel in addition to patient samples. If the results of patient samples were discordant, the whole procedure starting from RNA preparation was rerun twice until two concordant results were seen. To ensure that RNA in the tyrosinase gene-negative samples had not been degraded, a parallel PCR run for the detection of glyceraldehyde-3-phosphatase dehydrogenase (housekeeping enzyme) using an equal amount of RNA was performed. The specificity of PCR products was examined by sequencing in all positive samples. cDNA was amplified by using HTYR3/4 with previously marked universal primer M13 (forward and reverse). Sequencing was performed via dye primer sequencing (Perkin Elmer, Norwalk, CT). The analysis of each specimen was carried out on a 373 DNA sequencer (ABI; Applied Biosystems, Foster City, CA). In 20 blood samples of healthy donors and of patients with nonmelanoma cancers, tyrosinase transcripts were absent.
Statistics Disease-specific survival time was defined as the time from first blood sampling to the time of death from melanoma. Recurrence-free survival time was defined as the time from first blood sampling to a recurrence or to tumor-related death. Survival data was analyzed by the Kaplan-Meier method.26 Survival curves were compared using the log-rank test. All P values presented are two-sided. Multiple Cox regression was applied with backward elimination (selection level of 0.05) for selection of prognostic factors. The prognostic factors used for variable selection were age, sex, site of primary tumor, stage, histologic subtype, Clark level, and tumor thickness (tumor thickness was forced into the model as a well-known important prognostic factor). These factors were considered as non-time-dependent variables because they were included in the model with their value at time of first blood sampling. Additionally, the RT-PCR result was considered a time-dependent prognostic factor because two to eight RT-PCR results per patient were available, and RT-PCR results changed over time.27 Because we used as survival time the time from first blood sampling instead of time from first diagnosis of the primary tumor, we examined the data for lead time bias. The hazard ratios for the covariate of time from first diagnosis of the primary tumor to first blood sampling in the Cox models for each of our survival times were close to 1 with large P values, thus showing no lead time bias in our data. However, we circumvented a length time bias (ie, slowly progressing lesions with less aggressive potential will preferably be detected) because disease progression was not palpated but detected by ultrasound independent of palpability, and therefore, size of lesion is not that important.28 The statistical analyses were performed with the Statistical Analysis System Version 8.2 (SAS Institute, Cary, NC) and StatXact-3 (Cytel, Cambridge, MA).
During the study period of blood sampling of 3.3 years, 380 blood samples from 111 melanoma patients (throughout patients without sentinel node staging) were collected on the occasion of the routine follow-up examinations. Between two and eight blood samples were drawn from each patient (two samples, 25%; three samples, 40%; four samples, 18%; five samples, 7%; six samples, 5%; seven samples, 4%; and eight samples, 1%). The primary melanoma had been diagnosed between 0 and 15 years before first blood sampling (median, 1 year). At time of first blood sampling, 78 patients presented in clinical stage II after resection of primary melanomas with a Breslow thickness of at least 1.0 mm, whereas 33 patients presented in clinical stage III after resection of lymph nodes without evidence of metastases. The clinical data of these 111 patients are listed in Table 1. The median follow-up interval from the first blood sample to the last routine follow-up examination or death was 6.3 years (range, 0.9 to 8.6 years). The median follow-up interval from last blood sampling to last examination or death was 65.6 months (range, 0.9 to 89.0 months).
Tyrosinase RT-PCR Results Overall, 107 (28.2%) of 380 blood samples were positive for tyrosinase RT-PCR. Positive results were obtained in 23.3% of stage II patients (60 of 258 samples) and 38.5% of stage III patients (47 of 122 samples). In Table 2, RT-PCR results are shown in relationship to sex, primary tumor site, histologic subtype, Clark level, and tumor thickness with respect to the clinical stage at time of first blood sampling. In both clinical stages, data showed a slight tendency towards higher proportions of positivity for tyrosinase RT-PCR for male compared with female patients, but 95% CIs were wide and included the value 1.0. Overall, a positive RT-PCR was observed in 24 (48%) of 50 male patients compared with 26 (43%) of 61 female patients.
Relationship of RT-PCR Result to Tumor Site, Histologic Subtype, Clark Level, and Tumor Thickness No clear differences were observed in RT-PCR positivity for different primary tumor sites. ORs listed in Table 2 have wide 95% CIs, including the value of 1.0. Overall, positivity was observed in 25 (45%) of 55 patients with limb tumors compared with 25 (45%) of 56 patients with other tumor sites. Histologic subtype results were different for stage II and III patients (Table 2). Overall, positivity was observed in 13 (36%) of 36 patients with superficial spreading melanoma (SSM) or lentigo maligna melanoma (LMM) compared with 24 (45%) of 53 patients with nodular melanoma (NM) and nine (53%) of 17 patients with acrolentiginous melanoma (ALM) or other histologic subtypes. Stage II patients with NM showed a higher probability of being tyrosinase positive than stage II patients with SSM or LMM (OR, 2.1). Although 17 (43%) of 40 patients with NM tumors had tyrosinase transcripts in their peripheral blood, only seven (26%) of 27 melanoma patients with SSM or LMM tumors had positive test results. The contrary could be seen for stage III patients. Proportions of positivity were at 67% for SSM and LMM tumors in stage III patients and at 54% for patients with NM tumors. Because of the small numbers, however, no noticeable differences could be seen. A strong association was seen between Clark level and RT-PCR positivity in both clinical stages. Overall, a positive RT-PCR was observed in 37 (51%) of 72 patients with Clark level IV or V compared with five (19%) of 27 patients with Clark level II or III (OR, 4.7; 95% CI, 1.6 to 13.6).
In clinical stage II patients, data showed a strong effect towards higher proportions of positive test results for tumors thicker than 4 mm compared with tumors thinner than 4 mm; however, this effect was not seen in stage III patients. Overall, positivity occurred in 17 (71%) of 24 patients with tumors
Association of RT-PCR Result With Recurrence-Free Survival and Disease-Specific Survival
Cox Proportional Hazards Regression To further model the influence of RT-PCR testing on the prognosis (ie, depending on which RT-PCR result was derived at which point in time), RT-PCR testing was used as a time-dependent prognostic factor in a proportional hazards model. Therefore, a RT-PCR result was considered correct as long as it could not be replaced by the result of the subsequent RT-PCR. This regression analysis for all 111 melanoma patients showed that RT-PCR was a prognostically relevant factor for disease-specific survival, with a hazard ratio of 15.8 (95% CI, 5.2 to 49.0; P < .001), which means that the risk of dying became 15.8 times greater when RT-PCR turned to be positive during follow-up. The regression analysis for all 111 melanoma patients also showed that RT-PCR was a prognostically relevant factor for recurrence-free survival, with a hazard ratio of 4.5 (95% CI, 2.4 to 8.5; P < .001). In a multiple Cox regression analysis, sex, age at time of first blood sampling (in years), site of primary tumor (limb v trunk, neck, and scalp), stage (III v II), Clark level (IV and V v II and III), histologic subtype (NM v SSM and LMM v ALM and others), and, as a time-dependent covariate, RT-PCR result (positive v negative) were considered for variable selection using backward elimination, whereas tumor thickness (in millimeters) was forced into the model as a well-known important prognostic factor. All together, 96 patients were included in the Cox regression analyses because five patients with missing values for histologic type and 10 patients with different histologic types others than NM, SSM, ALM, or LMM were excluded. For disease-specific survival, RT-PCR result and age at time of first blood sampling were selected as important prognostic factors (Table 5). For recurrence-free survival, RT-PCR result, stage, and Clark level were selected as important prognostic factors (Table 6). Patients with stage III tumors and patients with Clark level 4 or 5 had an increased risk of a recurrence. Most striking was that both the probability of dying from the primary tumor and the probability of a recurrence increased dramatically if RT-PCR turned to be positive during follow-up, even though these effects were adjusted for tumor thickness.
A number of reports investigating the relationship between RT-PCR assays for melanoma markers and clinical data have been published. Of these, 16 studies investigated more than 50 patients with clinical disease stages I through III,9,11-13,15,19,22,23,29-36 and eight of these studies12,13,15,23,33-36 were reported with a minimum of 6 months of follow-up, which represents the absolute minimum to assess the potential prognostic value of RT-PCR markers to predict melanoma progression. Among the eight studies with sufficient follow-up, two studies34,35 failed to show a prognostic value of RT-PCR tests, whereas seven studies found a strong association between presence of melanoma markers in peripheral blood and recurrence-free13,15,19,23,33,35,36 or overall12,23,36 survival. In three studies,12,23,36 the RT-PCR was shown to be a relevant prognostic factor in multiple regression analysis, adjusting for various previously established clinical prognostic factors. The present study extends the previous analysis of our group23 in terms of patient numbers and follow-up duration. It also differs from the previous reports in the literature because it systematically addresses the potential informative value of serial blood tests. Serial blood tests, until recently, were only seen as a pure reflection of the stage of disease at diagnosis, but now, they have been proposed to define the prognostic relevance of a change in circulating melanoma cell status dynamically, and not.37 We report here on the clinical relevance of RT-PCR-based detection of circulating tumor cells considering 380 serial tyrosinase RT-PCR analyses in 78 stage II and 33 stage III patients with a median follow-up of 6.3 years. In a Cox proportional hazards model with RT-PCR result as a time-dependent covariate, patients becoming RT-PCR positive during follow-up had an increased risk of dying from melanoma, with a hazard ratio of 12.6 (95% CI, 3.4 to 46.3; P < .001), and had an increased risk for a recurrence, with a hazard ratio of 4.0 (95% CI, 1.9 to 8.3; P < .001). Both hazard ratios are adjusted for tumor thickness. Tumor thickness was forced into the Cox models because it is a known important prognostic factor. However, in both models, it had a P > .05. Therefore, tyrosinase results seem to be more important for prognosis than baseline measurements of tumor thickness; however, this might be a result of serial measurement of RT-PCR during follow-up and consideration of RT-PCR results at the particular time of measurement. At the time when our study was initiated, none of the previous reports by other groups had investigated the prognostic value of serial RT-PCR assays as the main focus of their studies, although four studies did analyze serial data. The results reported in our study are in line with both the findings by Mellado et al,36 which revealed an association between RT-PCR assay results during adjuvant interferon treatment and both overall survival and disease-free survival in 120 melanoma patients across all stages, and the preliminary results reported by Curry et al.19 But our results contrast with the reports by Hanekom et al34 and Brownbridge et al,35 who did not find a considerable RT-PCR conversion rate in melanoma patients before clinical disease progression. The reasons for the discrepancies among the reports are difficult to assess; they may be methodologic in nature, related to the patient populations, or related to the various follow-up intervals. Recently, Szenajch et al24 showed that patients with a more advanced disease more frequently test positive for tyrosinase, which is in line with our results. Osella-Abate et al38 conducted their trial by using fixed intervals of blood samples, independent of stage or the urgency of follow-up visits, and performing baseline blood samples (within 3 to 6 weeks after surgical treatment of regional nodal metastases in all patients). This was not performed in our subset because we wanted to evaluate minimal residual disease in patients who were already in follow-up and not starting from the beginning of diagnosis. Osella-Abate et al, 38 like us, found an association between positive tyrosinase results and disease recurrence during follow-up, and thus, they encouraged the clinical use of serial tyrosinase testing because of reliability and reproducibility.38 However, they did not correctly model the time dependence of the RT-PCR results, as we did in our Cox model. Our report has an advantage over previous studies because we only included patients with stage II and III disease in this study. We also had a major advantage because of the structure of our clinic, which allowed a complete and long-term follow-up (Table 7). In our clinic, all data, including the follow-up information, are available to the principal investigator of the study (C.V.). Because of this, we did not face the situation of other departments in which patients are lost to oncology or surgical services and in which it is difficult to obtain complete data. Another aspect of the study reported here is the finding that the serial RT-PCR assay result is an important prognostic factor for disease-specific survival. Therefore, RT-PCR results may be useful for patient stratification in clinical trials. Thus, stage II and III patients repeatedly presenting with a positive tyrosinase RT-PCR result from peripheral blood by serial testing can be considered as patients at high risk for relapse, and adjuvant clinical trials can be carried out in this patient subset. Further studies are necessary to address whether the RT-PCR assay adds information to serologic assays (S100 protein and melanoma inhibitory factor MIA), which also have been shown to predict survival of melanoma patients in several studies.39-43 The relationship of RT-PCR analysis in peripheral blood and histologic, immunohistologic, and PCR analysis of sentinel lymph nodes has not been systematically investigated to date. Theoretically, the lymph node analysis should yield the relevant information on regional spread, and the RT-PCR analysis of peripheral blood should predict hematogenous spread. The ultimate goal of all prognostic factors (including serologic and mRNA tumor markers), however, is to serve as a basis for treatment decisions. At present, there exists no promising chemotherapy or chemoimmunotherapy for melanoma, and in addition, data concerning adjuvant immunotherapy with interferon do not indicate improvement of disease-free or even overall survival.44 With the currently available data, however, there is no rationale for treatment decisions based on RT-PCR assay results or serologic markers because large prospective trials are necessary (and currently underway) to investigate whether a specific treatment modality may have different effects in patient cohorts with or without PCR evidence for circulating melanoma cells. One interesting aspect could be the recent progress in the field of melanoma vaccines, which are currently entering phase III testing in stage III melanoma patients. Apparently, multiple tyrosine RT-PCRs can be useful for molecular melanoma staging and, hence, for prediction of recurrence or development of metastases.
The authors indicated no potential conflicts of interest.
We thank Heidi Hainzl for her continuous support and helpful discussions.
Supported by grant No. 70-2459-Ke2 from Deutsche Krebshilfe. Both C.V. and M.K. contributed equally to this work. Presented in part at the Oral Melanoma Session of the 38th Annual Meeting of the American Society of Clinical Oncology in Orlando, FL, May 18-21, 2002. Authors' disclosures of potential conflicts of interest are found at the end of this article.
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44. Hancock BW, Wheatley K, Harris S, et al: Adjuvant interferon in high-risk melanoma: The AIM HIGH StudyUnited Kingdom Coordinating Committee on Cancer Research randomized study of adjuvant low-dose extended-duration interferon alfa-2a in high-risk resected malignant melanoma. J Clin Oncol 22:53-61, 2004 Submitted April 19, 2004; accepted November 22, 2004. This article has been cited by other articles:
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