Micrometastasis in breast cancer and other solid tumors

Hematogenous distant metastasis is the leading cause of cancer-related death in breast cancer and other solid tumors. By applying sensitive immunocytochemical and molecular assays, disseminated tumor cells (DTC) in bone marrow (BM) can be detected in 20-40% of cancer patients without any clinical or even histopathological signs of metastasis and the presence of these DTC at primary diagnosis predicts the subsequent occurrence of overt metastases in bone and other organs. cDNA-microarray analysis on primary breast carcinomas from patients with and without tumor cells in BM revealed a predominant downregulation of potential metastasis-suppressor genes in BM-positive tumors. Thus, dissemination of tumor cells appears to be an early process associated with a specific molecular signature of the primary tumor.

Comparison of multitarget fluorescence in situ hybridization in urine with other noninvasive tests for detecting bladder cancer

OBJECTIVES

To present a single-centre study investigating aneuploidy at chromosomes 3, 7, 17 and 9p21 (e.g. loss at 9p21) using a multitarget fluorescence in situ hybridization (FISH) system, as identifying genetic alterations in urine specimens is a promising approach for the noninvasive detection of bladder cancer.

PATIENTS AND METHODS

Urine samples from 103 patients were evaluated, including those from 46 with histologically confirmed urothelial carcinoma, two with other urological malignancies, and 55 who acted as controls. The urine samples were taken before any manipulation. The validity of FISH (Urovision, Vysis, Downers Grove, Ill, USA) was compared with other noninvasive urine tests, including the BTA-Stat test, the nuclear matrix protein (NMP)-22 test, and immunocytology against 486p3/12 and LewisX. Those evaluating the tests were unaware of the clinical and histopathological data. FISH was considered positive if five or more urinary cells had gains of two or more chromosomes. The threshold for the urine tests were 10 U/mL (NMP-22), 30% positive cells (486p3/12), or 5% positive cells, respectively (LewisX).

RESULTS

The sensitivity was 69% (FISH), 67% (BTA-Stat), 69% (486p3/12), 96% (LewisX) and 71% (NMP22), respectively; the respective specificity was 89%, 78%, 76%, 33% and 66%.

CONCLUSION

Multitarget FISH had a better specificity than the other urine markers but because of its inadequate sensitivity it does not seem to be powerful enough to replace endoscopy. Optimizing the marker panel could provide a higher sensitivity.

Mediastinal lymphadenectomy in non-small cell lung cancer: effectiveness in patients with or without nodal micrometastases - results of a preliminary study

OBJECTIVES

So far it has not clearly been demonstrated that systematic mediastinal lymphadenectomy improves survival in patients with non-small cell lung cancer. One explanation might be that in some patients an early spread of tumor cells has occurred which might not be curable by surgical means. To test this hypothesis lymph nodes of patients which were treated either by lymph node sampling or systematic lymphadenectomy were screened for micrometastatic spread of tumor cells and the influence of nodal micrometastases on the efficacy of lymphadenectomy was analyzed.

METHODS

Lymph nodes from patients (n=94) which were included in a randomized trial of lymph node sampling (LS, n=41) versus radical systematic lymphadenectomy (LA, n=53) were screened by immunohistochemistry for disseminated tumor cells using the antibody Ber-Ep4. The median observation time was longer than 5 years and follow-up data were available from all 94 patients. Kaplan-Meier curves were calculated and tested for statistical significance using the log-rank test.

RESULTS

Standard histopathological analysis revealed no lymph node involvement (pN0) in 61 patients, pN1 disease in 13 patients and pN2 disease in 20 patients without significant differences between LA and LS with respect to T-stage, N-stage or age and sex of the patients. By immunohistochemistry a minimal nodal spread of tumor cells was detected in 21 out of 94 patients (LS, n=10 (24%); LA, n=11 (21%)). Similar to the entire group of patients also in the subset of patients with nodal micrometastases the type of lymphadenectomy did not significantly influence the long-term survival (P=0.27 and P=0.39, respectively). In contrast, in patients with a negative immunohistochemical analysis systematic lymphadenectomy resulted in an improved overall survival (P=0.044).

CONCLUSIONS

Our data provide some evidence that systematic lymphadenectomy improves survival in patients without an early locoregional spread of cancer cells. As long as these patients can not be identified preoperatively all patients should undergo a systematic mediastinal lymphadenectomy.

Occult micrometastasis: enrichment, identification and characterization of single disseminated tumour cells

The decision as to whether systemic adjuvant therapy should be applied in breast cancer patients for secondary prevention of metastatic relapse is based solely on the statistical prognosis. For this reason, the direct identification of minimal residual cancer in distant organs (e.g. bone marrow) is of particular importance. In breast cancer 25-43% of the patients exhibit micrometastatic disease in bone marrow, following resection of their primary tumours. Successful enrichment, reliable identification and molecular profiling of disseminated tumour cells at the single cell level are still key issues in ongoing and future studies. In addition, first attempts have been reported to evaluate the biology of disseminated tumour cells using in vitro and in vivo models. Taken together, the advancing characterization of disseminated tumour cells opens the avenue for the development of new therapeutic approaches aimed at preventing metastatic relapse.

Molecular determinants of occult metastatic tumor cells in bone marrow

The success of mammographic screening for breast cancer is that it involves increasingly more patients with small primary tumors formerly thought to have an overall excellent prognosis. Yet, only approximately two thirds of these patients actually have this favorable prognosis, while the remaining third develops metastatic disease. Thus, there is emerging evidence that epithelial tumor cells can disseminate into secondary organs at an earlier stage of primary tumor development than appreciated by current risk classifications. Bone marrow is one of the most prominent secondary organs screened for the presence of disseminated tumor cells. The current data suggest that bone marrow micrometastases represent a selected population of dormant and heterogeneous cancer cells. The analysis of micrometastatic cells opens a new avenue by which to assess the molecular determinants of both early tumor cell dissemination and subsequent outgrowth into overt metastases. Moreover, identifying therapeutic target structures (e.g., HER2/neu), monitoring the elimination of bone marrow micrometastases, and assessing treatment-resistant tumor cell clones might help to understand the current limitations of adjuvant systemic therapy. This review summarizes the current knowledge of the biological characteristics of micrometastatic cancer cells in bone marrow of breast cancer patients.

Molecular profiling of micrometastatic cancer cells

Malignant tumors of epithelial tissue are the most common form of cancer and are responsible for the majority of cancer-related deaths in Western industrialized countries. As a result of progress in surgical treatment of these tumors, lethality is linked increasingly to early metastasis, which is generally occult at the time of primary diagnosis. For this reason, the direct identification of minimal residual cancer is of particular importance. The studies described below demonstrate the utility of immunocytochemical and molecular analysis in the diagnosis and characterization of minimal residual cancer. These methods not only can identify this critical stage of tumor progression but also may facilitate the development of therapies to prevent manifest metastasis.

MAGE-A gene expression pattern in primary breast cancer

Melanoma antigen (MAGE)-A-derived peptides elicit a strong in vitro T-cell response against tumor cells. For determination of MAGE-A1, -2, -3, -4, -6, and -12 expression profile in invasive breast cancer, we developed a multiplex seminested reverse transcription-PCR-method. In total, 18 of 67 (27%) tumors were positive for at least one of these MAGE transcripts, and the expression pattern was heterogeneous: MAGE-A1 was positive in 4 of 67 (6%), MAGE-A2 in 13 of 67 (19%), MAGE-A3 in 7 of 67 (10%), MAGE-A4 in 9 of 67 (13%), MAGE-A6 in 10 of 67 (15%), and MAGE-A12 in 6 of 67 (9%) patients. The MAGE-A transcripts were more frequently expressed in ductal breast carcinomas compared with other histomorphological types. We observed a preferential expression of MAGE-A in patients at a higher risk of recurrence: those harboring tumors with high levels of the protease urokinase-type plasminogen activator and its inhibitor plasminogen activator inhibitor 1, high score of the Ki-67 proliferation antigen, and lesser degree of differentiation. Our findings suggests a potential involvement of MAGE-A in tumor progression, with potential implications for active immunotherapy.

Bispecific single-chain antibodies as effective tools for eliminating epithelial cancer cells from human stem cell preparations by redirected cell cytotoxicity

High-dose chemotherapy (HDC) with autologous bone marrow or peripheral stem cell transplantation is discussed as one option to treat the extensive stage of a variety of tumors. Effective methods to eliminate contaminating tumor cells from human bone marrow or stem cell grafts may improve the outcome of the patients. We investigated 3 recombinant bispecific single-chain antibodies (bscAbs) directed against 17-1A (EpCAM), c-erbB-2 (HER-2/neu) and LeY on the one and CD3 on the other binding site for their ability to induce lysis of epithelial tumor cells by retargeting autochthonous T lymphocytes present in bone marrow mononuclear cells (BMMC) and in peripheral stem cell mononuclear cells (PSMC). The bscAbs showed remarkable specific lysis of different epithelial tumor cell lines with BMMCs as well as with PSMCs as effector cells. Investigation of the alpha 17-1A-alpha CD3 bscAb revealed a significant correlation between the percentage of CD3(+) cells present in the BMMCs and the rate of lysis as well as the absence of detrimental effects on the viability of hematopoietic progenitor cells as determined by colony-forming unit assays (CFUs). Our results indicate that recombinant bispecific single-chain antibodies could be new tools for purging of human bone marrow and peripheral stem cell grafts from contaminating epithelial cancer cells for patients receiving autologous stem cell transplantation after HDC.

Clinical significance of occult metastatic cells in bone marrow of breast cancer patients

The early and clinically occult spread of viable tumor cells to the organism is increasingly considered a hallmark in cancer progression, as emerging data suggest that these cells are precursors of subsequent distant relapse. Using monoclonal antibodies to epithelial cytokeratins or tumor-associated cell membrane glycoproteins, individual carcinoma cells can be detected on cytologic bone marrow preparations at frequencies of 10(-5) to 10(-6). Prospective clinical studies have shown that the presence of these immunostained cells in bone marrow, as a frequent site of overt metastases, is prognostically relevant with regard to relapse-free and overall survival. This screening approach may be, therefore, used to improve tumor staging and guide the stratification of patients for adjuvant therapy in clinical trials. Another promising application is monitoring the response of micrometastatic cells to adjuvant therapies, which, at present, can only be assessed retrospectively after an extended period of clinical follow-up. The present review summarizes the current data on the clinical significance of occult metastatic breast cancer cells in bone marrow.

The fate and prognostic value of occult metastatic cells in the bone marrow of patients with breast carcinoma between primary treatment and recurrence

BACKGROUND

The current study examines the fate of occult metastatic cells detected in bone marrow (BM) at primary diagnosis and evaluates whether persistently positive findings support the prognostic influence of these cells in patients with Stage I--III (International Union Against Cancer) breast carcinoma.

METHODS

The authors analyzed BM aspirates, at the time of primary diagnosis and after a median interval of 19 months (range, 7--67 months), from 89 patients who were free of recurrence. The presence of cytokeratin (CK) positive cells was assessed with the monoclonal anti-CK antibody A45-B/B3. Patients were observed prospectively for a median of 41 (range, 12--78) months after the first aspiration.

RESULTS

At the time of primary diagnosis, 24 of 89 patients (27%) presented with occult metastatic cells in the BM. Of the same 89 patients, 25 (28%) had a positive BM finding at the time of the second BM analysis. Among those patients with an initially negative BM finding, 15 patients (17%) had occult metastatic cells at time of the second BM aspiration, whereas 10 patients (11%) had a persistently positive BM finding. Patients with a persistently negative BM status (n = 50) had a significantly better overall survival than patients with a positive BM status at the time of the second BM aspiration (n = 25), both by univariate analysis (P = 0.045, log-rank) and multivariate analysis (P = 0.034, Cox regression).

CONCLUSIONS

In many patients with primary breast carcinoma, minimal residual disease can be detected by follow-up examination of the BM. This finding is prognostically relevant and provides reason to include BM monitoring in future clinical trials.

Characterization of disseminated tumor cells

The most prominent secondary organs screened for the presence of occult disseminated tumor cells are regional lymph nodes and bone marrow. The current data suggest that micrometastatic cells represent a selected population of dormant cancer cells, which still express a considerable degree of heterogeneity. The analysis of micrometastatic cells will open a new avenue to assess the molecular determinants of both early tumor cell dissemination and subsequent outgrowth into overt metastases. Moreover, identifying therapeutic target structures (e.g., HER2), monitoring the elimination of bone marrow micrometastases, and assessing treatment-resistant tumor cell clones may help in understanding the current limitations of adjuvant systemic therapy. This review summarizes the current knowledge on the biological characteristics of micrometastatic cancer cells in bone marrow and lymph nodes of cancer patients.

Identification and characterisation of minimal residual disease in solid tumors

Malignant tumors of epithelial tissue are the most common form of cancer and are responsible for the majority of cancer-related deaths in Western industrialized countries. As a result of progress in surgical treatment of these tumors lethality is linked increasingly with early metastasis, which is generally occult at the time of primary diagnosis. The decision as to whether systemic adjuvant therapy should be applied for secondary prevention of metastatic relapse following resection of the primary tumor is based solely on the statistical prognosis. For this reason the direct identification of minimal residual cancer is of particular importance. The studies described below demonstrate the utility of immunocytochemical and molecular analysis in the diagnosis and characterization of minimal residual cancer. For the first time these methods give access to this critical stage of tumor progression and also contribute to the development of new approaches to therapy aimed at preventing manifest metastasis.

Disseminated tumor cells: diagnosis, prognostic relevance, and phenotyping

Malignant tumors of epithelial tissue are the most common form of cancer and are responsible for the majority of cancer-related deaths in Western industrialized countries. As a result of progress in surgical treatment of these tumors, lethality is linked increasingly with early metastasis, which is generally occult at the time of primary diagnosis. The decision as to whether systemic adjuvant therapy should be applied for secondary prevention of metastatic relapse following resection of the primary tumor is based solely on the statistical prognosis. For this reason, the direct identification of minimal residual cancer is of particular importance. The studies described below demonstrate the utility of immunocytochemical and molecular analysis in the diagnosis and characterization of minimal residual cancer. These methods give access for the first time to this critical stage of tumor progression and also contribute to the development of new approaches to therapy aimed at preventing manifest metastasis.

ErbB2 overexpression on occult metastatic cells in bone marrow predicts poor clinical outcome of stage I-III breast cancer patients

Occult hematogenous micrometastases are the major cause for metastatic relapse and cancer-related death in patients with operable primary breast cancer. Although sensitive immunocytochemical and molecular methods allow detection of individual breast cancer cells in bone marrow (BM), a major site of metastatic relapse, current detection techniques cannot discriminate between nonviable shed tumor cells and seminal metastatic cells. To address this problem, we analyzed the relevance of erbB2 overexpression on disseminated cytokeratin-18-positive breast cancer cells in the BM of 52 patients with locoregionally restricted primary breast cancer using immunocytochemical double labeling with monoclonal antibody 9G6 to the p185erbB2 oncoprotein. Expression of p185erbB2 on BM micrometastases was detected in 31 of 52 (60%) patients independent of established risk factors such as lymph node involvement, primary tumor size, differentiation grade, or expression of p185erbB2 on primary tumor cells. After a median follow-up of 64 months, patients with p185erbB2-positive BM micrometastases had developed fatal metastatic relapses more frequently than patients with p185erbB2-negative micrometastases (21 versus 7 events; P = 0.032). In multivariate analysis, the presence of p185erbB2-positive micrometastases was an independent prognostic factor with a hazard ratio of 2.78 (95% confidence interval, 1.11-6.96) for overall survival (P = 0.029). We therefore conclude that erbB2 overexpression characterizes a clinically relevant subset of breast cancer micrometastases.

Detection and relevance of immunohistochemically identifiable tumor cells in lymph nodes

Lymph node metastasis is a well-known feature of poor prognosis in potentially resectable solid epithelial tumors. However, a significant number of apparently lymph node negative patients die early of metastatic disease. Therefore, it has to be assumed that in some patients an early tumor cell dissemination has occurred which is clearly underestimated by current staging procedures. Recently, it has been shown, that an early dissemination of individual carcinoma cells to regional lymph nodes can be detected by using sensitive immunocytochemical techniques with monoclonal antibodies against epithelium-specific proteins. The incidence of immunohistochemically positive patients varies between 12% and 70% depending on the type of primary tumor, the immunohistochemical staining procedure used, and especially on the primary monoclonal antibody. The detection of disseminated tumor cells in lymph nodes by immunocytochemistry is associated with a poorer prognosis in different types of epithelial tumors such as lung cancer or esophageal cancer. The immunocytochemical method might also be useful in the detection of occult tumor cells in sentinel lymph nodes. In conclusion, the immunohistochemical detection of disseminated tumor cells in lymph nodes can help to obtain a more exact identification of patients with an unfavorable prognosis. Whether the identified patients will gain from an adjuvant therapy has to be evaluated in further studies.

Occult tumor cells in bone marrow of patients with locoregionally restricted ovarian cancer predict early distant metastatic relapse

PURPOSE

Based on conventional tumor staging, primary ovarian cancer is viewed as an intraperitoneal disease that rarely spreads to extraperitoneal organs. However, autopsy studies reveal a much higher rate of occult metastasis, indicating that extraperitoneal spread occurs with much greater frequency than previously appreciated. Consequently, we investigated the incidence of early hematogenous dissemination and its association with distant disease-free and overall survival.

PATIENTS AND METHODS

Bone marrow aspirates from 108 patients newly diagnosed with International Federation of Gynecology and Obstetrics stage I to III ovarian cancer were prospectively analyzed with the novel anti-cytokeratin (CK) antibody A45-B/B3. We investigated the frequency of CK-positive tumor cells in bone marrow and their effect on prognosis in relation to established risk factors for tumor progression.

RESULTS

Tumor cells in bone marrow were detected in 32 (30%) of 108 patients. A CK-positive finding was unrelated to established risk parameters, except for poor nuclear grading of the primary tumor. At a median follow-up of 45 months (range, 12 to 77 months), the presence of occult metastatic cells in bone marrow was associated with the occurrence of clinically overt, extraperitoneal (predominantly extraskeletal) distant metastasis (relative risk [RR], 16.5; 95% confidence interval [CI], 6.2 to 56.9; P < .0001) and death from cancer-related causes (RR, 2.3; 95% CI, 1.2 to 4.3; P = .01). Multivariate analysis identified a positive bone marrow finding as an independent prognostic factor of reduced distant disease-free survival for all patients (RR, 13.8; 95% CI, 5.4 to 52.9; P < .0001) and for the 64 stage R0-1 patients (RR, 7.3; 95% CI, 1.5 to 56.8; P = .0021).

CONCLUSION

Our data signal that hematogenous dissemination of tumor cells occurs early and throughout all stages of ovarian cancer. The clinical significance of our findings is supported by the unfavorable prognosis in association with the presence of occult metastatic cells, especially in those patients who received an effective locoregional therapy.

Immunocytochemical detection and characterization of individual micrometastatic tumor cells

Early hematogenous spread of cancer cells must be regarded as major cause for the later development of metastatic disease in patients with completely resected solid tumors, which account for the majority of cancer-related deaths in industrialized nations. Because current procedures for tumor staging usually fail to detect such micrometastases, immunocytochemical assays with monoclonal antibodies directed against epithelial differentiation antigens have been designed for the detection of individual micrometastatic carcinoma cells in secondary organs. The recent development of monoclonal antibodies directed to epithelial differentiation proteins has opened a diagnostic window to detect such disseminated carcinoma cells. Methods for immunocytochemistry are described in detail in Chapter 2 by Brooks. Several studies have shown that bone marrow is an important, clinically relevant indicator organ for early disseminated cancer cells derived from various epithelial organs, including breast, lung, colon, rectum, prostate, kidney, ovary, esophagus, and pancreas (for review, see ref. 1). The use of various detection antibodies and marker antigens has contributed to an enormous heterogeneity in the methodology applied.The critical methodological evaluation of these antibodies in respect to specificity and sensitivity revealed considerable discrepancies in their potential to build a solid basis for a reliable and reproducible assay. Most of the studies were performed with monoclonal antibodies either against cytokeratin (2-5), a major constituent of the cytoskeleton in epithelial cells, or against membrane-bound mucins, such as epithelial membrane antigen, human milk fat globule, and tumor-associated glycoprotein-12 (6-8).

Malignant potential and cytogenetic characteristics of occult disseminated tumor cells in esophageal cancer

Although micrometastatic cancer cells in lymph nodes can be detected by monoclonal antibodies against epithelial or tumor-associated antigens, it remains unclear whether these cells are precursors of overt metastases or shedded tumor cells with a limited life span. Here we used esophageal cancer as a model to evaluate the prognostic significance and biological characteristics of such micrometastases. In lymph nodes classified as tumor free by conventional histopathological staging, tumor cells were identified with monoclonal antibody Ber-EP4 in 89 of 126 patients (71%) with completely resected (R0) esophageal carcinomas. Multivariate survival analysis underlined the strong and independent prognostic significance of Ber-EP4-positive cells in "node-negative" (pN0) patients. To assess the biology of Ber-EP4-positive cells, we established tumor cell lines from an immunohistochemically positive lymph node and the autologous primary tumor. p53 mutational analysis and multiplex-fluorescence in situ hybridization revealed common aberrations shared between both cell lines, whereas an insertion of chromosome 13 material in the short arm of chromosome 1 was only observed in micrometastatic cells. The tumorigenicity and metastatic potential of both cell lines were demonstrated in severe combined immunodeficient mice. In conclusion, our data provide first direct evidence for the malignant potential of micrometastatic cancer cells.

Overexpression of matrix metalloproteinase 2 predicts unfavorable outcome in early-stage non-small cell lung cancer

This prospective study was performed to assess the impact of matrix metalloproteinase (MMP) 2 expression on the clinical course of patients with operable non-small cell lung cancer (NSCLC). Specimens of 193 consecutive patients with completely resected NSCLC were examined for MMP-2 expression by immunohistochemical staining with a polyclonal antibody. Homogeneous immunostaining of cancer cells was considered positive and heterogeneous, or no staining was considered negative concerning overexpression of MMP-2. Four specimens were excluded from further analyses because of unspecific staining. The median follow-up period was 71.5 months (range, 12-120 months). Overexpression of MMP-2 was observed in 64 (33.9%) of 189 patients and did not correlate with clinicopathoiogical parameters. In patients without lymph node involvement (pN0 stage) MMP-2 overexpression was an independent prognostic parameter for unfavorable outcome: Log-rank analysis showed a significant association of MMP-2 overexpression with shortened cancer-related survival (P = 0.04) and disease-free survival (P = 0.03). Multivariate regression analysis confirmed MMP-2 overexpression as predictor of shortened cancer-related survival in NSCLC without lymph node involvement (P = 0.005, relative risk, 2.6). The present study revealed that MMP-2 overexpression predicts a poor prognosis in early-stage NSCLC. Therefore, it might be worth investigating the role of MMP inhibitors as adjuvant therapeutic agents in NSCLC.

The 17-1A antigen is expressed on primary, metastatic and disseminated non-small cell lung carcinoma cells

In view of the high incidence of early distant tumor relapses in apparently completely resected (R0, M0) non-small cell lung cancer (NSCLC), there is a need for an adjuvant therapy. Considering the low tumor burden in these patients, an adjuvant therapy with monoclonal antibodies (i.e., the 17-1A MAb) might be appropriate. The purpose of our study was to test whether the 17-1A antigen is expressed on primary and metastatic NSCLC carcinoma cells. Using immunohistochemistry, the expression of 17-1A was analysed in primary tumors (n = 60) and in lymph node metastases (n = 7) of patients with NSCLC. Additionally, we investigated in 6 patients the expression of 17-1A on disseminated tumor cells in the bone marrow, which were detected by the pan-cytokeratin MAb A45-B/B3 using a double-labeling technique. The 17-1A antigen was homogeneously expressed in 47 (78.3%) out of 60 primary NSCLCs. The expression of 17-1A was independent from the tumor histology, the grade of differentiation, and other clinicopathological parameters (ploidy status, TNM-stage). Lymph node metastases were positive in 4 (57.4%) out of 7 cases. The double-labeling experiments demonstrated that 17-1A is coexpressed on disseminated tumor cells in the bone marrow in 5 (83%) out of 6 patients. The 17-1A antigen is expressed on the majority of primary, metastatic, and disseminated NSCLC cells. Patients with 17-1A-positive tumors might benefit from an adjuvant therapy with MAb 17-1A after completely resected NSCLC.

[Isolated tumor cells in bone marrow predicts reduced survival in lymph node-negative non-small-cell lung cancer]

BACKGROUND

It became recently evident that isolated tumor cells undetectable by conventional tumor staging are frequently present in bone marrow of patients with apparently localized non-small cell lung cancer (NSCLC). The clinical relevance of this minimal hematogenous tumor cell dissemination is under vigorous debate.

METHODS

For tumor cell detection in the bone marrow we used monoclonal antibody CK2 against the epithelial intermediate filament protein cytokeratin 18. The influence of a positive bone marrow finding on clinical outcome was studied in 139 patients with NSCLC postoperatively staged as pT1-4, pN0-2, M0, R0 after a median follow up of 66 months (48-74).

FINDINGS

Cytokeratin-18-positive cells in bone marrow were demonstrated in 83 (59.7%) patients at the time of primary surgery and in 6 of 12 representative patients analyzed twice 3-18 months after surgery. In patients without histopathological lymph node metastases (pN0; n = 66) the occurrence of > or = 2 tumor cells in bone marrow at primary surgery was a strong and independent predictor for overall survival (p = 0.007) in univariate analysis. The multivariate analysis showed a 2.8 times increased risk for shorter survival in patients with disseminated tumor cells versus patients without such cells. Four of the six patients with a positive CK status after surgery developed a tumor recurrence 11-44 months after the operation, while in none of the patients with a negative bone marrow at all times intervals showed a tumor relapse.

CONCLUSIONS

Minimal residual bone marrow involvement is an independent prognostic factor for overall survival in patients with node-negative NSCLC, which may help to identify patients in need of an adjuvant systemic therapy. The postoperative persistence or re-appearance of tumor cells in bone marrow indicates that these are not only shredded cells but rather represent true micrometastasis.

Analytical variables of reverse transcription-polymerase chain reaction-based detection of disseminated prostate cancer cells

Early systemic spread of occult tumor cells that may develop into founders of incurable distant metastasis has been identified in prostate cancer patients by reverse transcription-PCR (RT-PCR) amplification of prostate-specific antigen (PSA) mRNA. Nevertheless, the introduction of this new staging tool into the clinical setting has been hampered by the disparate and contradictory data on the sensitivity and specificity of RT-PCR methods reported recently. We used PSA RT-PCR to examine the influence of analytical variables such as priming and enzyme of reverse transcriptase reaction, temperature and time of primer annealing, primer extension and denaturation, as well as the concentrations of magnesium chloride, Taq polymerase, deoxynucleotide triphosphate, primers and BSA on the amplification process. By systematically varying these chemical and physical components, we could demonstrate a significant increase in amplification yield and in stringency of primer annealing. This may explain the wide variety of published findings on molecular staging of prostate cancer, which currently impedes the clinical introduction of PSA RT-PCR assays in prostate cancer. Methodological analyses are needed for standardization and quality assurance to achieve reproducible molecular methods that can be used in clinical practice.