Limitations of reverse-transcriptase polymerase chain reaction analyses for detection of micrometastatic epithelial cancer cells in bone marrow

Quantitative detection of disseminated free cancer cells in peritoneal washes with real-time reverse transcriptase-polymerase chain reaction: a sensitive predictor of outcome for patients with gastric carcinoma

OBJECTIVE

To evaluate the feasibility of real-time reverse transcriptase-polymerase chain reaction (RT-PCR) detection of free cancer cells in the peritoneal washes as a prognostic indicator for patients with gastric carcinoma.

SUMMARY BACKGROUND DATA

Peritoneal lavage cytology (CY) is an excellent prognostic determinant but lacks sensitivity. This can be improved by using RT-PCR to quantitate carcinoembryonic antigen (CEA) mRNA in peritoneal washes.

METHODS

Peritoneal washes were obtained from 189 patients with gastric carcinoma during laparotomy. CEA mRNA levels and CEA/GAPDH mRNA ratios were quantified using a real-time PCR system with fluorescent hybridization probes. Receiver-operating characteristic plots were used to determine which of these parameters should be used as a marker for the intraperitoneal cancer cells. The prognostic significance of its positivity was then evaluated by Kaplan-Meier curves, and its value as an independent prognostic factor was evaluated by multivariate analysis.

RESULTS

The sensitivity and specificity of real-time RT-PCR with an optimal cutoff value were 80% and 94%; those for conventional cytology were 56% and 91%. The survival of 16 patients who were CY-PCR+ was poor and approached that of 35 CY+ patients. Recurrence as peritoneal carcinomatosis was frequent among PCR+ patients but rare for their PCR- counterparts. PCR+ was a significant independent prognostic factor, along with the presence of node metastasis and serosal invasion, but CY+ was not.

CONCLUSIONS

Quantitative RT-PCR of peritoneal washes can replace cytologic examination as a tool for the sensitive evaluation of the risk of intraperitoneal recurrence in patients with gastric carcinoma.

Molecular assessment of lymph nodes in patients with resected stage I non-small cell lung cancer: preliminary results of a prospective study

OBJECTIVES

Routine histologic examination of resected lymph nodes in patients with stage I non-small cell lung cancer may underestimate the incidence of advanced disease. The presence of occult lymph node metastases may predict a higher risk of recurrence after intended curative resection. The purpose of this study was to determine the prognostic significance of TP53 and K-ras mutations in histologically determined negative lymph nodes from patients with stage I non-small cell lung cancer who underwent intended curative surgical resection.

METHODS

Between July 1995 and March 1998, clinical data and tissue samples of primary tumors and lymph nodes were collected in a prospective fashion from 102 patients undergoing resection for non-small cell lung cancer (stage I, n = 55; stage II, n = 32; stage IIIA, n = 15). TP53 and K-ras mutations were detected by direct sequencing. If molecular alterations were found in the primary tumor, the corresponding lymph nodes were examined for these same TP53 (by oligonucleotide hybridization) and K-ras (by allele-specific ligation) mutations.

RESULTS

TP53 mutations were found in 47 of 94 primary tumors (50%), and K-ras mutations were present in 26 of 55 adenocarcinomas (47%). A total of 134 lymph nodes from 32 patients with stage I disease were analyzed. In 9 cases (28%) the same TP53 or K-ras mutations were found in tumor and lymph node specimens, suggesting occult metastasis. On the basis of nodal location, 7 patients had their disease upstaged by a single stage and 2 patients by two stages. All 28 patients with stage II or III disease had pathologically determined positive nodes that were confirmed as positive by molecular analysis. Standard histopathologic assessment of regional lymph nodes failed to detect metastases at levels below 0.9% tumor-specific mutant TP53 clones per node. No statistically significant difference in disease-specific or overall survival was observed between patients with stage I disease with and without molecular lymph node metastases.

CONCLUSIONS

Occult lymph node metastases are present in a significant percentage of patients with stage I non-small cell lung cancer. These data suggest that molecular analysis allows a more accurate assessment of staging. However, larger studies are needed to determine the clinical role of molecular staging.

Emerging molecular markers of cancer

Alterations in gene sequences, expression levels and protein structure or function have been associated with every type of cancer. These 'molecular markers' can be useful in detecting cancer, determining prognosis and monitoring disease progression or therapeutic response. But what is the best way to identify molecular markers and can they be easily incorporated into the clinical setting?

Human mammaglobin RT-PCR assay for detection of occult breast cancer cells in hematopoietic products

BACKGROUND

The aim of this study was: (i) to evaluate the sensitivity and specificity of mammaglobin as a reverse transcriptase polymerase chain reaction (RT-PCR) marker of breast cancer cells; (ii) to determine the incidence of tumor cell contamination of hematopoietic samples from patients with breast cancer.

MATERIALS AND METHODS

A nested RT-PCR assay for mammaglobin was developed. Sensitivity was determined by serial dilution assays with breast cancer cell lines, human breast cancers and normal breast tissue. Specificity was evaluated in hematopoietic samples from healthy volunteers and patients with hematological malignancies or solid tumors other than breast cancer.

RESULTS

The mammaglobin transcript was detected in all 15 breast cancers, one benign breast tumor and five normal breast tissues studied, as well as in three breast cancer cell lines, in dilutions as low as 10(-8). The transcript was not detected in any of 47 peripheral blood samples, 15 bone marrow aspirates and 28 peripheral blood progenitor cell samples from the three control populations. Mammaglobin mRNA was detected in 19 of 78 peripheral blood samples from patients with breast cancer starting systemic chemotherapy, as well as in five of 30 repeat samples collected before the fourth cycle of treatment. The transcript was also present in six of seven bone marrow aspirates from patients with metastatic disease, two of five with loco-regional disease, but not in the aspirate of two patients with thrombocytopenia and a previous history of breast cancer.

CONCLUSIONS

Human mammaglobin mRNA is a sensitive and specific marker of breast cancer cells and should be further studied as a molecular marker of tumor cell contamination of hematopoietic tissues.

Circulating calcitonin and carcinoembryonic antigen m-RNA detected by RT-PCR as tumour markers in medullary thyroid carcinoma

Detection of local relapse or metastasis in medullary thyroid carcinoma (MTC) continue to pose a major diagnostic challenge. Besides established diagnostic studies such as serum calcitonin (CT) and carcinoembryonic antigen (CEA), molecular detection of circulating tumour cells may be an additional diagnostic tool for the early detection of disease recurrence. We performed reverse transcription-polymerase chain reaction (RT-PCR) on blood samples from patients diagnosed with MTC disease using primers specific for CT and CEA, respectively. CT mRNA was not detectable in peripheral blood of all patients with MTC (n = 11) and all controls (n = 32). CEA mRNA was significantly more often detected patients with MTC (72.7%) than in controls (34.4%; p = 0.038; Fisher exact test). With an example of a patient with MTC and massive tumour mass in the neck we demonstrate the failure of detection of CT mRNA over a period of 6 months, whereas CEA mRNA could be detected in peripheral blood of this patient. As a consequence, CT mRNA detected by RT-PCR in the peripheral blood can not be recommended as a tumour marker in MTC. However, the use of carcinoembryonic mRNA may provide a significant improvement in diagnosis of recurrent disease in MTC.

High tumour contamination of leukaphereses in patients with small cell carcinoma of the lung: a comparison of immunocytochemistry and RT-PCR

In small-cell lung carcinoma (SCLC) tumour cell contamination of leukaphereses is unknown. The present study was performed to define appropriate markers for reverse transcriptase polymerase chain reaction (RT-PCR), then to assess the contamination rate of leukaphereses and corresponding bone marrow samples. Immunocytochemistry (ICC) and RT-PCR methods were also compared. Among the 33 patients included, analyses were performed in 16 who had multiple leukaphereses and 17 who had only bone marrow. Leukapheresis products and bone marrow were analysed by ICC using several specific monoclonal antibodies against neural-cell adhesion molecule (N-CAM), epithelial glycoprotein (EGP-40) and cytokeratins (CK). Samples were also analyzed by RT-PCR for expression for N-CAM, synaptophysin, neuron-specific enolase, chromogranin, cytokeratin-18/-19, CEA, EGP-40, apomucin type 1 (MUC-1) and human endothelial cell-specific molecule (ESM-1). Using ICC staining, contaminating tumour cells were detected in 34% of leukaphereses (27% in patients with limited disease and 43% in those with extensive disease). N-CAM was the most reliable marker for detection of contamination. For RT-PCR, CK-19 and CEA were the only appropriate markers. Positive signal rate in leukaphereses increased to 78% (89% for patients with limited disease and 67% for extensive disease). In bone marrow, both techniques were in agreement whereas in leukaphereses, RT-PCR was better than ICC. A high rate of tumour cell contamination was demonstrated not only in bone marrow but also in leukaphereses from SCLC patients. The most appropriate technique was RT-PCR mainly in patients with limited disease.

Detection of MAGE-A3 in breast cancer patients' sentinel lymph nodes

The detection of occult metastatic breast cancer cells by RT-PCR is limited by the poor specificity of most tumour mRNA markers. MAGE-A3 is a highly specific tumour mRNA marker that is not expressed in non-cancer cells. This study assesses MAGE-A3 mRNA as a molecular marker for the detection of tumour cells in the sentinel lymph nodes (SLN) of breast cancer patients. Serial frozen sections of SLN (n = 121) were obtained from 77 AJCC (American Joint Committee on Cancer) Stage I-IIIA breast cancer patients. MAGE-A3 mRNA analysis of SLN was performed by RT-PCR and Southern blot analysis. Tumour cells were detected in 48 of 121 (40%) SLN from 77 patients by H&E or IHC staining, and 35 of 77 (45%) patients, overall, had histopathologically (H&E and/or IHC) positive SLN. Among histopathologically negative SLN, 28 of 73 (38%) SLN were MAGE-A3 mRNA positive by RT-PCR. Overall, 41 of 77 (53%) patients and 50 of 121 (41%) SLN were positive for MAGE-A3. MAGE-A3 mRNA expression in the SLN occurred more frequently with infiltrating lobular carcinoma (P < 0.001) than with infiltrating ductal carcinoma, adding further evidence of possible phenotypic differences between these 2 subtypes of breast cancer. Due to its high specificity, MAGE-A3 mRNA is a potentially useful marker for detecting breast cancer cells in the SLN. One half of breast tumours expressed MAGE-A3 mRNA, which has important potential implications for antigen-specific targeted immunotherapy.

Reverse-transcriptase polymerase chain reaction of the maspin gene in the detection of bone marrow breast carcinoma cell contamination

BACKGROUND

Maspin is a molecular marker used for the detection of contaminating breast carcinoma (BC) cells in peripheral blood and lymph nodes. However, its specificity has been questioned recently. The objective of this study was to verify the specificity of this marker and to determine the incidence of positive bone marrow results in patients with BC who are eligible for high-dose chemotherapy (HDT) both in early and advanced disease stages and before and after treatment.

METHODS

Bone marrow specimens from 41 patients with BC as well as from 35 normal volunteers and 17 patients with hematologic tumors were examined for maspin transcript expression by a modified nested reverse transcriptase-polymerase chain reaction technique.

RESULTS

Maspin transcript was found in all normal and neoplastic breast tissues and in none of the 35 normal bone marrow specimens (specificity, 100%; 95% confidence interval, 90-100%). However, the transcript was found in 40% of the bone marrow samples from patients with hematologic malignancies. Thus, this marker appears very specific for discriminating between normal controls and patients with BC, but it cannot be considered disease specific. Among patients with BC, bone marrow was positive for the maspin transcript in 32% of patients with early-stage disease and in 75% of patients with metastatic disease before chemotherapy. After treatment, in 75% of patients with early-stage disease and in 50% of patients with metastatic disease, the bone marrow results became maspin negative.

CONCLUSIONS

On the basis of the current data, although it is not disease specific, maspin is a reliable marker for detecting bone marrow molecular disease in patients with BC and should be considered for prospective studies as a prognostic indicator and as an assay for monitoring residual disease.

Immunocytochemical detection of bone marrow micrometastases in colorectal carcinoma patients, using a monoclonal antibody to villin

The search continues to find methods to more effectively distinguish colorectal carcinoma patients who could be separated into high-risk and low-risk categories. Investigators have reported on the detection of occult micrometastases in bone marrow using antibodies to cytokeratin, which is a marker of epithelial cells but which has no tissue specificity, as opposed to villin, a cytoskeletal protein that is specifically involved in the formation of brush-border microvilli in the small intestine and colon epithelium. Specificity and sensitivity of antibody to villin (ID2C3) and antibody to cytokeratin (A45-B/B3) were first studied in normal bone marrow and in a test system in which cancer cell lines were mixed in normal bone marrow. In a preliminary study including 16 colorectal carcinoma patients, we compared the number of villin-positive cells with cytokeratin-presenting cells. As A45-B/B3, ID2C3 was determined to be sensitive enough to detect one cancer cell in 10(6) hematopoietic cells. Staining of hematopoietic cells with irrelevant antibody and a light staining of megakaryocytes with ID2C3 limited the specificity of the method. In colorectal carcinoma patients, correlation between ID2C3 and A45-B/B3 was 94%. Sensitivity and specificity of ID2C3 antibody to villin were satisfactory. Its clinical relevance must be investigated in further studies.

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.

Detection and clinical significance of occult tumour cells in colorectal cancer

BACKGROUND

A variety of techniques have been employed for the detection of occult tumour cells in the blood, bone marrow and lymph nodes of patients with colorectal cancer. This review examines the methods used, results obtained and the clinical significance of studies in this field.

METHODS

A Medline literature search was performed using the terms colorectal cancer, minimal residual disease, micrometastasis, polymerase chain reaction, reverse transcriptase polymerase chain reaction and immunocytochemistry; further references were obtained from key articles.

RESULTS

Immunocytochemical examination of bone marrow is the benchmark for detecting clinically significant occult disease. Larger standardized studies are required to confirm the prognostic significance of molecular assays for the detection of tumour cells in blood and bone marrow. The prognostic significance of lymph node tumour cells detected by either immunohistochemical or molecular methods awaits further affirmation.

CONCLUSION

Standardization of terminology and techniques used, combined with large prospective clinical studies, is required if detection of occult residual disease is to become a prognostic marker for recurrence in colorectal cancer.

Ectopic expression of guanylyl cyclase C in CD34+ progenitor cells in peripheral blood

PURPOSE

To examine the utility of guanylyl cyclase C (GC-C)-specific nested reverse transcriptase polymerase chain reaction (RT-PCR) to detect circulating tumor cells in patients with colorectal cancer.

PATIENTS AND METHODS

Peripheral-blood mononuclear cells from 24 patients with Dukes' stage D colorectal cancer were analyzed by GC-C-specific nested RT-PCR using 1 microg of total RNA. Peripheral-blood mononuclear cells from 20 healthy volunteers served as controls. Additionally, peripheral-blood CD34+ progenitor cells were assayed for the expression of both GC-C and other epithelial cell-specific markers.

RESULTS

GC-C mRNA was detected in blood mononuclear cells from all 24 patients with colorectal cancer and all healthy volunteers. These unexpected positive results reflected low-level ectopic transcription of GC-C in CD34+ progenitor cells. Moreover, CD34+ progenitor cells expressed other epithelial cell-specific markers, including prostate-specific antigen, prostate-specific membrane antigen, carcinoembryonic antigen, CK-19, CK-20, mucin 1, and GA733.2. Limiting the quantity of mononuclear cell total RNA analyzed to < or = 0.8 microg eliminated detection of GC-C and other tissue-specific transcripts in blood of healthy volunteers. However, under the same conditions, GC-C mRNA was detected in mononuclear cells from all 24 patients with metastatic colorectal cancer. Using 0.5 microg of total RNA and GC-C-specific primers, nested RT-PCR detected a single human colon carcinoma cell (approximately 20 to 200 GC-C transcripts/cell) in 10(6) to 10(7) mononuclear blood cells.

CONCLUSION

These data suggest that GC-C may be useful for detecting circulating colorectal cancer cells. They also demonstrate that CD34+ cells are a source of ectopically expressed epithelial cell-specific markers and that CD34+ cells may contribute to the high false-positive rate generally observed when those markers are used to detect rare circulating metastatic cancer cells by RT-PCR.

Cytokeratin 20 is not a reliable molecular marker for occult breast cancer cell detection in hematological tissues

Cytokeratins are potential markers for epithelial cell detection in hematological tissues. Thus, we developed a nested reverse transcriptase-polymerase chain reaction (RT-PCR) strategy to detect cytokeratin 20 (CK20) mRNA and studied its sensitivity and specificity as a molecular marker of occult breast cancer cells. In cell dilution experiments with human breast cancer cell lines, the limit of detection was 1 tumor cell in 1,000 hematological cells. In RNA dilution experiments of breast cancer cells' RNA in E. Coli tRNA, the CK20 transcript was only detectable when at least 1 ng of total tumor RNA was present in a total of 1 microg of RNA mixture. In parallel experiments using colorectal cancer specimens, CK20 mRNA was detected with as little as 1 pg of total tumor RNA, suggesting a low level of CK20 mRNA expression in breast cancer cells. The CK20 transcript was detected in all six tumors and five hematological samples of breast cancer patients but in none of nine hematological cell lines. However, CK20 transcript was also detected in unfractionated nucleated cell population of hematological samples from 23 of 31 (74%) healthy volunteers and from 12 of 24 (50%) patients with hematological malignancies. When mononucleated and polymorphonucleated cell populations of hematological samples from these control groups were screened separately, CK20 expression was detected in 94% of polymorphonucleated cell fractions and in 44% of mononucleated cell subpopulations. Thus, we conclude that the low sensitivity and specificity of RT-PCR detection of CK20 mRNA limits its usefulness for breast cancer cell detection in hematological products.

The role of imaging studies and molecular markers for selecting candidates for radical prostatectomy

For the typical patient who has newly diagnosed prostate cancer, clinically organ-confined disease of moderate grade, and a PSA less than 10 ng/mL, the current role of imaging studies and molecular biomarkers is limited. Bone scans are not necessary for newly diagnosed men with a PSA less than 10 ng/mL in the absence of bone pain. Similarly, abdominal and pelvic CT scanning rarely provides any useful diagnostic or staging information when the PSA is less the 20 ng/mL and is indicated rarely. Endorectal coil MR imaging adds staging information for patients with a PSA between 10 and 20 ng/mL, a Gleason score of 7 or less, and 50% or more positive biopsies on a sextant sampling. Indium 111 capromab pendetide scanning (ProstaScint) is FDA-approved to evaluate newly diagnosed patients at high risk for metastases. These patients have a Gleason score of 7 or greater and a PSA greater than 20 ng/mL, a Gleason score of 8 to 10 regardless of the PSA value, or clinical stage T3 disease and a Gleason score of 6 or greater. RT-PCR testing of blood or bone marrow for prostate-specific or prostate cancer-specific gene expression, or "molecular staging," is a promising technique whose current use is still investigational. Much useful information may be gained by careful study of prostate needle biopsy material. Aside from current Gleason grading and the number or percentage of cores involved with cancer, no molecular biomarker is approved for clinical use. p27, p53, bcl-2, Ki-67 (MIB-1), and the assessment of neovascularity hold promise, but prospective multicenter studies are needed. In the long-term, multiple gene expression profiling of biopsy material using gene chips may revolutionize the care of patients with prostate cancer and those who elect radical prostatectomy.

Technical aspects of minimal residual disease detection in carcinoma patients

The burden of occult malignant cells which remains after a course of treatment that has resulted in clinical remission is referred to as minimal residual disease (MRD). MRD is increasingly considered as a determinant of local or systemic recurrence in cancer patients. During the last 20 years, methods for the detection of rare cancer cells have evolved from mere cytomorphological investigations to a variety of immunological and molecular assays. Since surgical therapy remains the best treatment option for cancer patients with resectable tumors, the first question to address is whether the removal of the tumor was complete or some cancer cells remained from the tumor at the primary site. Several tumor-associated DNA alterations have been identified to solve this diagnostic problem. Assays detecting tumor-associated DNA alterations have been applied to resection margins and body fluids such as bronchoalveolar lavage, sputum, urine, pancreatic juice, colonic lavage, and stool. Due to the higher sensitivity of immunocytochemical and reverse-transcriptase polymerase chain reaction (RT-PCR)-based assays, the second question to be addressed is whether systemic hematogenous or lymphatic spread of cancer cells occurred. Disseminated cancer cells have been detected in bone marrow aspirates, peripheral blood, and lymph node biopsies, and cancer cell dissemination is regarded as a relevant and independent prognostic factor. Thus, sensitive techniques for the detection of MRD are likely to guide indications for surgical or adjuvant therapy protocols in clinical oncology. However, since many of the assays for the detection of MRD are complex, and results are influenced by a variety of technical aspects, the majority of diagnostic applications have not yet been sufficiently standardized. Consequently, quality control and reproducibility of minimal disease detection assays remain unsolved problems. Therefore, well controlled collaborative studies are urgently required to evaluate indications and diagnostic standards for these assays. This review summarizes technical aspects and their implications for the clinical application of presently available assays for MRD detection in carcinoma patients.

Minimal residual disease in non-small-cell lung cancer

Early metastatic relapse after complete resection (R0) of apparently localized primary tumors is frequent in patients with non-small-cell lung cancer (NSCLC). This observation indicates an occult tumor cell dissemination already present at the time of primary surgery but undetectable by current tumor staging methods. During the past 10 years ultrasensitive immunohisto-/-cytochemical and molecular assays have been developed that are able to detect single tumor cells and small tumor cell clusters present in lymph nodes classified as tumor-free by conventional histopathologic analysis, bone marrow, or peripheral blood. Here we present an overview of the incidence and prognostic impact of such early disseminated tumor cells in patients with NSCLC.

Implications of occult metastatic cells for systemic cancer treatment in patients with breast or gastrointestinal cancer

The early and clinically occult spread of viable tumour cells to the organism is becoming acknowledged as a hallmark in cancer progression, since abundant clinical and experimental data suggest that these cells are precursors of subsequent distant relapse. Using monoclonal antibodies against epithelial cytokeratins or tumour-associated cell membrane glycoproteins, individual carcinoma cells can be detected in cytological bone marrow preparations at frequencies of 10(-5) to 10(-6). Prospective clinical studies have shown that the presence of such immunostained cells in bone marrow is prognostically relevant with regard to relapse-free and overall survival, even in malignancies that do not preferentially metastasise to bone. As current treatment strategies have resulted in a substantial improvement of cancer mortality rates, it is noteworthy to consider the intriguing options of immunocytochemical screening of bone marrow aspirates for occult metastatic cells. Besides improved tumour staging, such screening offers opportunities for guiding patient stratification for adjuvant therapy trials, monitoring response to adjuvant therapies (which, at present, can only be assessed retrospectively after an extended period of clinical follow-up), and specifically targeting tumour-biological therapies against disseminated tumour cells. The present review summarises the current data on the clinical significance of occult metastatic cancer cells in bone marrow.

Minimal residual disease in gastrointestinal cancer

Tumor progression after curative resection of gastrointestinal carcinomas is probably caused by pre- or intraoperative tumor cell dissemination. Disseminated tumor cells are generally detected by immunohistochemistry- or PCR-based molecular-biology methods. A consensus on which is the most adequate detection method has not yet been found, which makes the comparison of data difficult. The prognostic relevance of disseminated cells has been shown, at least in part, for esophageal, gastric, pancreatic, and colonic cancer. The data regarding hepatocellular cancer is conflicting. This article gives a critical review of tumor cell detection in gastrointestinal cancer.

Detection and enrichment of disseminated renal carcinoma cells from peripheral blood by immunomagnetic cell separation

We have established an immunomagnetic separation procedure for the detection of circulating tumor cells in the peripheral blood based on the magnetic cell sorting (MACS) technique. In previous in vitro experiments, renal-cell carcinoma (RCC) cells were mixed with peripheral blood. In dilutions of 1:200 to 1:107 tumor cells per mononuclear blood cells, an average recovery rate of 84% of tumor cells was determined. In our study, 104 peripheral blood samples from 59 renal carcinoma patients were analyzed. MACS resulted in significant depletion of leukocytes, permitting a search for tumor cells on just 1 slide. Analyzing 8 ml of peripheral blood per patient, 19/59 RCC patients carried disseminated tumor cells (32%) in the range of 1 to 38 cells (median 8). Interestingly, for the cytokeratin-positive (CK+) patient group, we found a correlation between tumor cell number and grading (G2 vs. G3) and an increased number of CK+ patients with advanced tumor stage. MACS appears to be an efficient technique to detect disseminated tumor cells in peripheral blood.

Bone marrow micrometastases detected by RT-PCR for mammaglobin can be an alternative prognostic factor of breast cancer

PURPOSE

To evaluate a new prognostic factor of breast cancer, bone marrow micrometastases which was detected by RT-PCR for mammaglobin, a sensitive molecular marker of breast cancer, was examined.

MATERIALS AND METHODS

One hundred and eleven samples from stage I-III breast cancer patients were examined. Bone marrow micrometastases and clinicopathological parameters, which were age, tumor size, lymph node metastasis and status of the estrogen receptor, were evaluated for the prognostic factor by statistical analysis.

RESULTS

Median follow-up time was 21.1 months. Thirty-three (29.7%) out of 111 samples were RT-PCR positive. Eight cases (24.2%) in this group showed recurrent lesions in the distant organs. Whereas six (7.7%) out of 78 RT-PCR negative patients had distant recurrences. In the premenoposal patients, and in the patients with axillary lymph node metastases, RT-PCR positive cases showed significantly higher distant recurrent rate. Bone marrow micrometastases, axillary nodal status, and estrogen receptor were independent prognostic factors for breast cancer by both univariate and multivariate analysis.

CONCLUSIONS

Bone marrow micrometastases detected by RT-PCR for mammaglobin can be a useful predictive marker for early distant recurrence of breast cancer.

Biological implications of tumor cells in blood and bone marrow of pancreatic cancer patients

BACKGROUND

Patients with pancreatic cancer often have tumor recurrence despite curative resection. Cancer cells detected in blood or bone marrow at the time of diagnosis may relate to tumor stage and to prognosis. Recent research emphasis has centered on tumor cells in bone marrow aspirates, but whether these represent early micrometastases or blood-borne cells in transit is unknown.

PATIENTS AND METHODS

We developed a specific immunocytochemical assay that evaluated more than 5.3 x 10(6) extracted mononuclear cells per sample of blood and bone marrow and that could identify a single tumor cell in that population. The assay was applied to samples of blood and bone marrow from 105 patients with pancreatic cancer and 66 controls. The prevalence of isolated tumor cells was compared with Union Internationale Contre le Cancer (UICC) stage. A multivariate Cox regression analysis for survival was performed.

RESULTS

Pancreatic cancer cells were detected in 26% of blood samples and in 24% of bone marrow specimens. Specificity for cancer was 96%. The prevalence of isolated tumor cells in patients with proven resectable cancer was 9% in blood and 13% in bone marrow. The prevalence increased with UICC tumor stage in blood (P =.04) but not in bone marrow (P =.52) and correlated in blood with resectability (P =.02), progression of disease (P=.08), and peritoneal dissemination (P =.003). While survival correlated significantly with tumor stage (P <.001) and isolated tumor cells in blood correlated with tumor stage, the finding of cancer cells in blood or bone marrow, or both, was not independently associated with survival in patients with pancreatic cancer.

CONCLUSIONS

Isolated tumor cells in blood but not bone marrow reflect the stage of growth and spread of pancreatic cancer, particularly in the peritoneal cavity. The findings are consistent with cells in bone marrow aspirates being in transit, not implanted. These disseminated cancer cells may be the consequence, rather than the cause, of progression.

Occult metastasis

The most important factor affecting the outcome of patients with invasive cancers is whether the tumor has spread, either regionally (to regional lymph nodes) or systemically. However, a proportion of patients with no evidence of systemic dissemination will develop recurrent disease after primary 'curative' therapy. Clearly, these patients had occult systemic spread of disease that was undetectable by methods routinely employed (careful pathological, clinical, biochemical and radiological evaluation). In addition, the success of adjuvant therapy is assumed to stem from its ability to eradicate occult metastases before they become clinically evident [1]. Therefore, methods for the detection of occult metastases in patients with the earliest stage of cancer, i.e., prior to detection of metastases by any other clinical or pathological analysis, have received a great deal of attention.

Lack of prognostic influence of circulating tumor cells in peripheral blood of patients with colorectal cancer

BACKGROUND AND AIMS

Circulating tumor cells in peripheral blood may be detected using high-sensitivity molecular techniques in several types of solid neoplasms, but their significance in colorectal cancer is controversial. The aim of this study was to assess the prognostic value of carcinoembryonic antigen (CEA) messenger RNA (mRNA) detection in peripheral blood samples from patients with colorectal cancer.

METHODS

Peripheral vein blood samples from 95 consecutive patients with histologically confirmed colorectal carcinoma were obtained immediately before surgery to determine the presence of circulating tumor cells by use of a reverse-transcription polymerase chain reaction targeting CEA mRNA. Endpoints of the study were disease-free and overall survival. Results are referred to the whole series and, more importantly, to the 68 patients who underwent surgery for cure.

RESULTS

After a median follow-up of 42 months, 19 of 68 patients (28%) operated on for cure had tumor relapse. In addition, 50 of 68 patients (73%) were alive. The probability of disease-free and overall survival was dependent on lymph node metastases and degree of differentiation, but not on the presence of circulating tumor cells (disease-free survival: relative risk, 1.00; 95% confidence interval [CI], 0.39-2.22, P = 0.99; overall survival: relative risk, 0.91, 95% CI, 0.34-2.43; P = 0.84). Similar results were obtained when all 95 patients with colorectal cancer were analyzed (disease-free survival: relative risk, 1.11; 95% CI, 0.63-1.95; P = 0.71; overall survival: relative risk, 1.21; 95% CI, 0.63-2.30, P = 0.55).

CONCLUSIONS

Preoperative detection of blood circulating tumor cells by means of reverse-transcription polymerase chain reaction of CEA does not have prognostic significance in patients with colorectal cancer.

Influence of Preharvest Tumor Cell Contamination in Bone Marrow or Blood Does Not Predict Resultant Tumor Cell Contamination of Granulocyte Colony-Stimulating Factor Mobilized Stem Cells

Tumor cell contamination of stem cell collections harvested from breast cancer patients is a common phenomenon described by several investigators but with findings that vary among reports. Although so-called co-mobilization of these cells has been hypothesized, the origin of tumor cell contamination in stem cells is still unknown. A total of 47 G-CSF mobilized stem cell grafts from patients with nodal-positive (n = 30), chemosensitive metastatic (n = 11), and 5 women with inflammatory breast cancer were evaluated for cancer cells by immunocytochemistry. Additionally, 40 bone marrow aspirations and 23 peripheral blood samples collected prior to apheresis and after one to two cycles of conventional chemotherapy were available for examination. Tumor cell contamination of leukapheresis correlated best with preharvest blood state. This was valid when the nominal (positive/negative) presence of tumor cells in blood was compared to the nominal presence of tumor cells in apheresis samples and when the it was correlated to the tumor cell load of apheresis samples (TCL = tumor cells per 10(6) nucleated cells investigated). The correlation between blood and stem cells was better (nominal and quantitative) than that between marrow and stem cells, despite the larger sample size of marrow aspirations. The presence or absence of cancer cells in apheresis samples could not be safely predicted by the presence or absence of tumor cells in marrow or blood alone. Diagnostic specificity seems to improve from a combination of results from marrow and blood analysis. No correlation was found in quantitative analysis of tumor cell contamination between marrow and blood. In conclusion, the results suggest that blood and bone marrow represent different compartments for epithelial cancer cells and that contaminating tumor cells in stem cell harvests may be derived from the blood and/or marrow compartment. The tumor cell contamination of a stem cell harvest cannot be safely predicted by a preceding blood or marrow analysis.

Molecular tools in the detection of micrometastatic cancer cells--technical aspects and clinical relevance

The frequent failure to reduce the mortality due to epithelial cancers by common medical intervention results primarily from early dissemination of cancer cells, which is missed by conventional diagnostic procedures used for tumor staging. Individual carcinoma cells present in regional lymph nodes, blood or distant organs (e.g., bone marrow) can be detected by sensitive immunologic or molecular methods. Here, we review recently developed molecular assays for the detection of individual micrometastatic cancer cells and their clinical application in patients with epithelial tumors.

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.

Detection of micrometastasis through tissue-specific gene expression: its promise and problems

The detection of micrometastasis holds great promise for earlier staging of patients with malignant diseases and may ultimately guide therapeutic decisions. So far, reverse-transcriptase polymerase chain reaction (RT-PCR) amplification of genes expressed by the tumor in a tissue-specific manner is the method with the highest diagnostic sensitivity. It is well-established that the identification of single tumor cells is feasible in tissues and bodily fluids in both experimental and clinical samples. However, at present it is difficult to assign clinical significance to results obtained from such tests, primarily because their diagnostic specificity is disputed, both conceptionally and methodologically. For example, amplification of candidate mRNA targets is detectable in non-cancer patients using conditions that generally fail to generate such signals from healthy individuals. We have established that transcription of the tissue-specific genes can be affected by different means. Specifically, some target mRNA species are detectable in peripheral blood nuclear cells as low abundance constitutive-like expression, whereas others are induced through in vitro tissue culturing. In addition, mRNA expression may be distinctly upregulated by different cytokines or growth factors in vivo. Also, background transcription of target mRNAs can occur in different lineages of peripheral blood cells. Finally, expression may be substantially different in tissues such as peripheral blood, bone marrow, or lymph nodes. As a consequence, cancer patients in unrelated clinical situations may present with different levels of background expression, making the diagnostic specificity of test results difficult to assess. To add to this complexity, an increasing body of literature is being generated using various targets for a multitude of malignant diseases. There is a great variety of methods for sampling, specimen processing, nucleic acids recovery, test conditions, and readout formats, making it impossible to compare data. In summary, modalities of quantitative RT-PCR methods and standardization issues should be discussed to address these questions.

Polymerase chain reaction in the detection of circulating tumour cells in peripheral blood of melanoma patients

Conflicting results were obtained by various research groups using the tyrosinase reverse transcription polymerase chain reaction (RT-PCR) for detecting melanoma cells circulating in peripheral blood. Whereas 100% positivity was initially reported for stage IV patients, more recent investigations reported positive detection rates between 30% and 50% in patients with disseminated melanoma. While the high detection rate initially reported in metastatic melanoma may be explained by contamination problems, methodological differences in different steps of the technical procedure of RT-PCR may account for the differences reported in more recent examinations. Major differences may result from the kind of blood preparation, the RNA isolation method, the kind of RT enzyme used, and the gene targeted by PCR primers. In our experience, blood purification by a Ficoll gradient increased melanoma cell detection rates compared to RNA extraction from total blood or after erythrocyte lysis. Amplification of MelanA in addition to tyrosinase resulted in a 30% enhanced sensitivity of melanoma cell detection compared to amplification to tyrosinase alone, whereas gp100/pMel17 and MUC18 gene products were already detected in blood from nonmelanoma patients. These findings are in agreement with those of other groups. Currently, an increase in the sensitivity for detection of circulating tumour cells to more than 50% of patients with disseminated melanoma seems to be unlikely. It is interesting that between 15% and 30% positive results and sometimes more have already been obtained from patients with primary melanoma. So far, there is no data for judging the prognostic significance of the detection of circulating tumour cells in patients without clinically recognisable metastases. Our limited experience shows that staging examinations in these patients reveal no proof of macrometastasis. Therefore, it is presently unclear whether these positive findings are associated with long-term prognosis or if they merely reflect false positive findings in this highly sensitive RT-PCR technique.

Detection of breast cancer cell contamination in leukapheresis product by real-time quantitative polymerase chain reaction

Identification of sensitive techniques for breast cancer cell detection might be relevant for high-dose chemotherapy programs with autologous stem cell transplantation. We investigated the feasibility of Maspin, Mammaglobin and c-ErbB-2 amplification by real-time quantitative polymerase chain reaction (RQ-PCR) for the detection of breast cancer cells in leukaphereses. Expression of the three markers was determined in primary breast cancers and cell lines. Peripheral blood (PB), bone marrow (BM), and leukapheresis samples from patients with malignancies other than breast cancer were used as controls. Sensitivity was evaluated by dilution of primary tumors and cell lines with mononuclear blood cells. We found expression of the three markers in all primary tumors and most cell lines. No blood specimen from control patients had the Maspin transcript, while only one was positive for Mammaglobin. Weak c-ErbB-2 expression was detectable in most PB, all BM and all leukapheresis samples from controls. We observed a low sensitivity of Maspin RQ-PCR and a sensitivity of Mammaglobin RQ-PCR up to one tumor cell in 10(6) mononuclear cells. One out of 18 leukaphereses from breast cancer patients screened for the presence of Mammaglobin mRNA was positive. We conclude that Mammaglobin RQ-PCR might be a useful tool for detection of leukapheresis contamination.

Molecular diagnosis of head and neck cancer

Patients with advanced stages of head and neck cancer frequently develop locoregional recurrence as well as distant metastases. These data indicate that traditional diagnostic methods such as histopathology and radiology are not sensitive enough to detect the small numbers of tumor cells which are left behind, defined as minimal residual disease (MRD). Sensitive diagnostic assays based on molecular markers appear to be powerful tools to improve the staging of these patients. At the DNA level, tumor-specific p53 mutations seem to have great potential for the detection of "occult" tumor cells at surgical margins and lymph nodes. At the RNA level HNSCC associated antigens like the E48 antigen, allow the detection of rare HNSCC cells in blood and bone marrow and, it is hoped, also in lymph nodes and lymph node aspirates. However, the molecular assays which are used to detect MRD are subject to certain (technical) problems which affect their sensitivity and specificity. In this paper we will present examples of molecular assays such as the plaque assay using p53 mutations and the E48 RT-PCR, and show their use for MRD detection in cervical lymph nodes. In addition, we will discuss the problems and pitfalls associated with these sensitive techniques.

Simultaneous immunohistochemical detection of tumor cells in lymph nodes and bone marrow aspirates in breast cancer and its correlation with other prognostic factors

PURPOSE

We studied the prognostic and predictive value of immunohistochemically detected occult tumor cells (OTCs) in lymph nodes and bone marrow aspirates obtained from node-negative breast cancer patients. All were classified as distant metastases-free using conventional staging methods.

PATIENTS AND METHODS

A total of 484 patients with pT1-2N0M0 breast cancer and 70 with pT1-2N1M0 breast cancer and a single affected lymph node participated in our trial. Ipsilateral axillary lymph nodes and intraoperatively aspirated bone marrow were examined. All samples were examined for OTCs using monoclonal antibodies to cytokeratins 8, 18, 19. Immunohistological findings were correlated with other prognostic factors. The mean follow-up was 54 +/- 24 months.

RESULTS

OTCs were detected in 180 (37.2%) of 484 pT1-2N0M0 patients: in the bone marrow of 126 patients (26.0%), in the lymph nodes of 31 patients (6.4%), and in bone marrow and lymph nodes of 23 (4.8%) patients. Of the 70 patients with pT1-2N1MO breast cancer and a single involved lymph node, OTCs were identified in the bone marrow of 26 (37.1%). The ability to detect tumor cells increased with the following tumor features: larger size, poor differentiation, and higher proliferation. Tumors of patients with OTCs more frequently demonstrated lymph node invasion, blood vessel invasion, higher urokinase-type plasminogen activator levels, and increased PAI-1 concentrations. Patients with detected OTCs showed reduced disease-free survival (DFS) and overall survival (OAS) rates that were comparable to those observed in patients who had one positive lymph node. Multivariate analysis of prognostic factors revealed that OTCs, histological grading, and tumor size are significant predictors of DFS; OTCs and grading of OAS.

CONCLUSION

OTCs detected by simultaneous immunohistochemical analysis of axillary lymph nodes and bone marrow demonstrate independent metastatic pathways. Although OTCs were significantly more frequent in patients with other unfavorable prognostic factors, they were confirmed as an independent prognostic factor for pT1-2N0M0, R0 breast cancer patients.

Clinical significance of circulating cancer cells in peripheral blood detected by reverse transcriptase-polymerase chain reaction in patients with breast cancer

Detection of breast cancer micrometastases based on specific genetic markers may provide useful information to justify appropriate therapeutic strategies. We examined the presence of a carcinoembryonic antigen (CEA) messenger RNA(mRNA) in the peripheral blood of 32 patients with varying stages of breast cancers by means of the reverse transcriptase-polymerase chain reaction (RT-PCR) assay prior to and after the curative operation. CEA mRNA were detected in the peripheral blood samples from 12 (38%) out of 32 breast cancer patients prior to surgery. Among 12 CEA mRNA-positive patients prior to surgery, 4 (33.3%) relapsed from breast cancer within 2 years after surgery. Moreover, CEA mRNA was detected in the peripheral blood samples obtained prior to surgery in 3 out of 11 patients (27.2%) with a stage I disease. One out of three of these patients had a relapse in lung. There were four patterns of CEA mRNA expression, ( +, + ), (+, -), (-, + ), and (-, -) in the pre- and post-operative blood samples. In 12 CEA mRNA-positive patients submitted to surgical resection of the primary tumor, persistence of CEA mRNA expression was observed in five patients (+, +) within a month after surgical treatment. Three out of these 5 patients (60%) relapsed from breast cancer within 2 years after surgery. In 7 other patients (+, -), CEA mRNA expression was not detected within a month after tumor removal, and recurrence occurred in 1 out of the 7 patients (14%) within 2 years after surgery. In 19 patients, CEA mRNA expression was not detected in pre- or post-operative blood samples (-, -). There was a patient whose blood sample was negative for CEA mRNA before the operation, but changed to show a positive result after surgery (-,+). No recurrence was found in 20 of CEA mRNA-negative patients prior to surgery (-, +), (-, -). This study suggested that the presence of CEA mRNA expression in preoperative peripheral blood sample represent the progression of the disease, especially the risk of hematogenous metastasis in the patients in spite of their clinical stage, and the presence of CEA mRNA in the postoperative blood sample may represent the evidence of a residual disease. Thus consideration might be given for adding combined multi-modal therapy.

The clinical utility of multimarker RT-PCR in the detection of occult metastasis in patients with melanoma

Cutaneous melanoma is characterized by a high propensity for metastasis. Currently, surgical intervention remains the mainstay of therapy. This approach has proven most beneficial when the diagnosis is of early stage primary lesions. Likewise, patients undergoing resection for a solitary site of metastasis have shown a survival advantage. Identification of metastatic disease depends predominantly on radiographic techniques requiring the presence of significant tumor burdens for successful imaging. However, at that time, the role of surgery and/or biochemotherapy may be of limited value. Techniques to identify minimal disease states may permit more accurate assessment of prognosis. The detection of occult tumor cells by RT-PCR in the blood, lymph nodes, and bone marrow of melanoma patients provides one such approach to monitor tumor progression. Single-marker RT-PCR has been used as one such approach but is noted to have limitations in sensitivity and specificity based on the heterogeneity of tumor marker expression among tumors as well as within an individual tumor lesion or among multiple lesions in individual patients. We employed a multimarker reverse transcriptase polymerase chain reaction assay that demonstrates improved sensitivity over a single-marker approach. Currently, the consequences of detecting systemic subclinical metastasis remain unknown pending longer-term follow-up. The detection of occult melanoma cells using molecular techniques in conjunction with known clinicopathologic prognostic factors may provided a novel and efficient approach in monitoring tumor progression and further identify high-risk patients diagnosed early in the disease course.

Recent advances in technologies for the detection of occult metastatic cells in bone marrow of breast cancer patients

Approximately half of breast cancer patients with stage I-III disease will suffer metastatic disease despite resection with tumour-free margins. In 30-40% of these patients, individual carcinoma cells can already be detected at the time of primary therapy in cytological bone marrow preparations using immunocytochemistry. Numerous prospective clinical studies have shown that the presence of occult metastatic cells in bone marrow is prognostically relevant to patient survival. Only a few studies failed to do so, thus stimulating a critical discussion on the methodology and clinical value of bone marrow analysis. The potential for obtaining improved prognostic information on patient outcome, for monitoring tumour cell eradication during adjuvant and palliative systemic therapy, and for specifically targeting tumour biological therapies are intriguing clinical opportunities that may be afforded by bone marrow analysis. Standardized and robust methodology is a prerequisite for clinical application of these techniques, however.

Prognostic value of genomic alterations in minimal residual cancer cells purified from the blood of breast cancer patients

The prognostic value of disseminated tumour cells derived from 353 breast cancer patients was evaluated. Disseminated tumour cells were purified from blood using a newly established method and nucleic acids were subsequently isolated. We investigated genomic imbalances (GI) such as mutation, amplification and loss of heterozygosity of 13 tumour suppressor genes and 2 proto-oncogenes using DNA from isolated minimal residual cancer cells. Significant correlations were found between genomic alterations of the DCC - and c-erbB-2 genes in disseminated breast cancer cells and actuarial relapse-free survival. Furthermore, increasing numbers of genomic imbalances measured in disseminated tumour cells were significantly associated with worse prognosis of recurrent disease. Logistic regression and Cox multivariate analysis led to the identification of genomic imbalances as an independent prognostic factor. Determination of disseminated tumour cells by genotyping of oncogenes and tumour suppressor genes seems not only to be a useful adjunct in follow up of carcinoma patients but provides also valuable additional individualized prognostic and predictive information in breast cancer patients beyond the TNM system.

Clinical relevance of occult metastatic cells in the bone marrow of patients with different stages of breast cancer

Data are emerging about the prognostic relevance of occult metastatic cells in the bone marrow of patients with various solid tumors. Discrepancies among different studies on the prognostic relevance of isolated tumor cells may be caused by tumor cell heterogeneity and the use of different immunoassays. There is increasing evidence that validated anticytokeratin antibodies (e.g., A45-B/B3) represent the present standard for the detection of isolated tumor cells. This immunocytochemical assay allows the identification of patients with occult tumor cell dissemination that cannot be identified by conventional screening methods in tumor staging. According to recent studies, these patients are at higher risk for subsequent development of distant metastases and might therefore benefit from early systemic therapy. At advanced stages of the disease, the micrometastatic tumor load after adjuvant therapy, or at the time of emerging recurrences, appears to reflect the tumor's ability to progress. Therapeutic monitoring and cell-cycle independent antibody-based therapy are among possible implications of this new, promising diagnostic tool. The present review also focuses on state of the art, reliable detection methods of occult metastatic cells in the bone marrow of breast cancer patients and on the prognostic relevance of these cells at different stages of the disease.

Detection of circulating breast cancer cells by reverse transcriptase polymerase chain reaction (RT-PCR)

The confounding problem in treatment of breast cancer is the metastasis of breast tumour. Reverse transcriptase polymerase chain reaction (RT-PCR) has been recently used in the detection of circulating breast cancer cells. This review reports on the development of this assay as well as its advantages and disadvantages. We feel that cytokeratin 20 and beta -human chorionic gonadotropin (hCG) mRNA are the best markers for the detection of circulating breast cancer cells. We suggest that the multiple RNA marker RT-PCR assay can help to increase both sensitivity and specificity of detection, and that quantitative RT-PCR assay is more effective than the qualitative assay in the detection of circulating breast cancer cells.

Molecular detection and characterisation of circulating tumour cells and micrometastases in solid tumours

The detection and molecular characterisation of circulating tumour cells (CTC) and micrometastases may have important prognostic and therapeutic implications. Because their numbers are very small, these tumour cells are not easily detected using conventional methods. In the last decade, numerous groups have attempted to detect occult tumour cells in solid malignancies using the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). These assays were in the vast majority directed against tissue-specific markers. PCR was shown to be superior to conventional techniques in detecting occult tumour cells allowing the identification of one malignant cell mixed with 1-10 million normal cells. In some tumours like melanoma and prostatic carcinoma, tissue-specific transcripts were detected with high specificity in the blood of patients with localised and advanced disease. In some reports, PCR was shown to be a strong predictor of poorer outcome. However, due to the many limitations of PCR (e.g false-positives), many groups are developing new approaches for the detection of occult tumour cells. The most attractive technique involves immunomagnetic isolation of CTC and micrometastases prior to downstream analysis. The tumour-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry and in situ hybridisation. This will lead to better quantification and molecular characterisation of these tumour cells. In conclusion, the molecular detection and characterisation of occult tumour cells offer a great opportunity for better stratifying patients with solid tumours and for developing new prognostic markers and targeted therapies.

Pitfalls in the detection of disseminated non-hematological tumor cells

There is not yet a consensus on the reliability of the methods that should be used for the detection of rare disseminated tumor cells from non-hematological malignancies. In this review, we will discuss the advantage and drawbacks of the classical approach of immunocytochemistry and the molecular detection by reverse transcriptase polymerase chain reaction (RT-PCR). The interpretation of the biological significance of circulating tumor cells and the pitfalls of the detection techniques are the main causes of discrepancy between the conclusions of different tumor-cell detection (TCD) studies.

Negative immunomagnetic purging of peripheral blood stem cell harvests from breast carcinoma patients reduces tumor cell contamination while not affecting hematopoietic recovery

BACKGROUND

Because tumor contamination of hematopoietic stem cell grafts may influence the outcome in breast carcinoma (BC) patients undergoing high dose chemotherapy (HDC), several ex vivo procedures for the purging of autologous harvests have been investigated. The authors studied the presence of epithelial tumor cells and the growth of hematopoietic progenitors in peripheral blood stem cell (PBSC) collections from patients with metastatic breast carcinoma before and after a purging procedure performed by a negative immunomagnetic BC cell separation.

METHODS

Eighteen patients entered the study. Tumor contamination was assessed by conventional immunocytochemistry (ICC) and by a liquid culture assay developed in the study laboratory. Committed and more primitive hematopoietic progenitors were quantitated before and after the negative selection. Ten patients received HDC with purged PBSC support.

RESULTS

Before purging, 4 of 18 PBSC collections were found to be contaminated by liquid culture; among these samples, only 1 was positive by ICC. Three of the four positive collections, including the ICC positive sample, became negative after immunomagnetic selection whereas BC cells still were present after the procedure in one harvest. A high recovery of both primitive and mature hematopoietic progenitors was found after the purging procedure. Patients receiving purged PBSC after myeloablation had a prompt and complete hematopoietic reconstitution, and no graft failure was observed at a median follow-up of 1 year.

CONCLUSIONS

The preliminary results of the current study suggest that negative selection of BC cells is able to purge PBSC effectively while having no apparent affect on hematopoietic progenitor recovery in vitro and in vivo.

Detection of circulating tumor cells by reverse transcriptase polymerase chain reaction of maspin in patients with breast cancer undergoing conventional-dose chemotherapy

PURPOSE

To establish, in patients with breast cancer subjected to primary conventional chemotherapy and enrolled in a prospective study, the mobilizing effect of therapy on potentially neoplastic cells by means of a reverse transcriptase polymerase chain reaction (RT-PCR) assay for mRNA of maspin, a protein related to the serpin family of protease inhibitors.

PATIENTS AND METHODS

Peripheral-blood samples were collected from 30 patients with histologically proven breast cancer before and 4 and 8 days after conventional chemotherapy for three consecutive courses. A total of 216 samples were screened for the presence of maspin mRNA by RT-PCR.

RESULTS

Before therapy, all samples but one were negative. After chemotherapy, 11 patients (38%) had positive samples. No difference in the rate of positivity was observed between groups defined according to initial stage, type of chemotherapy, Ki-67-related proliferative activity, or CA 15.3 expression.

CONCLUSION

Our results confirm that RT-PCR for maspin mRNA is a sensitive assay for the study of circulating potentially neoplastic mammary cells in patients with breast cancer. Moreover, our findings indicate a marked effect of conventional-dose chemotherapy on the mobilization of these cells in breast tumors. In our series of patients, this phenomenon does not seem to be associated with other known risk factors. Finally, the data suggest, without proving, an association between the presence of circulating maspin positive cells and a higher risk of disease progression. If this association could be confirmed, then the assay could have prognostic significance. However, larger confirmatory studies are necessary.

Colorectal cancer staging and adjuvant chemotherapy

Colorectal cancer is a significant cause of morbidity and mortality in Western populations. The standard of care for staging patients with colorectal cancer to determine prognosis and identify patients who will receive adjuvant therapy continues to be histopathology of regional lymph nodes. However, the significant variability in survival within each staging category likely reflects the heterogeneity of detecting micrometastatic disease employing this technique. Novel molecular markers of micrometastases currently in development will permit more accurate staging of patients with colorectal cancer. These advances in staging will distinguish patients who will maximally benefit from adjuvant therapy from those who have an especially good prognosis in whom chemotherapy can be avoided. In addition, new adjuvant chemotherapeutic agents, novel combinations of those agents and creative dosing schedules currently being investigated will offer considerable advantages with respect to ease of administration, safety and tolerability, quality of life and efficacy. Ultimately, it is anticipated that advances in molecular diagnostics will define unique biochemical characteristics of patients' tumours, permitting individualization of chemotherapeutic regimens employing novel agents that specifically exploit those characteristics.

Total PSA, free PSA/total PSA ratio, and molecular PSA detection in prostate cancer: which is clinically effective and when?

OBJECTIVES

To ascertain when the serum determination of the free prostate-specific antigen (PSA)/total PSA (fPSA/tPSA) ratio is clinically useful, and whether the identification of PSA or prostate-specific membrane antigen (PSM) mRNA in circulating cells has diagnostic advantages over the determination of their protein product.

METHODS

fPSA, tPSA, and the fPSA/tPSA ratio were determined in the sera of 50 men with benign nonprostatic urologic diseases (EPD), 112 patients with prostate cancer (PCa), and 218 with benign prostatic hyperplasia (BPH). mRNA was extracted from the circulating mononuclear cells of 13 EPD samples, 25 PCa samples, and 38 BPH samples. PSA and PSM mRNA signals were identified in these samples by means of reverse transcriptase-polymerase chain reaction.

RESULTS

Overall, at a fixed specificity of 95%, the sensitivity of tPSA was 19% and that of the fPSA/tPSA ratio was 40% in distinguishing PCa from BPH. The fPSA/tPSA ratio allowed the discrimination of PCa from BPH with satisfactory sensitivity and specificity when considering patients less than 60 years of age (100% and 95%, respectively). PSA and PSM mRNA were positive in 1 and 7 of 13 EPD samples, 6 and 13 of 25 PCa samples, and 6 and 17 of 38 BPH samples. The Gleason score did not correlate with tPSA, the fPSA/tPSA ratio, PSA mRNA, or PSM mRNA.

CONCLUSIONS

The serum determination of the fPSA/tPSA ratio is an excellent index of PCa for subjects younger than 60 years of age; the clinical utility of PSA mRNA identification in circulating cells needs to be validated by large follow-up studies, and the analysis of PSM mRNA seems to be of no clinical interest.

RT-PCR-based detection of occult disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. An overview

Despite recent progress in early detection and local curative therapy, patients with primary epithelial cancer quite frequently relapse with incurable metastasis. Early disseminated tumor cells that may be seminal for distant failure and are undetectable by current diagnostic methods have been identified by immunocytochemical techniques in bone marrow of cancer patients using monoclonal antibodies against cytokeratins. Recently, promising new molecular approaches, namely, reverse transcriptase--polymerase chain reaction (RT-PCR) assays, have been suggested as a potential technique for the detection of minimal residual tumor burden by targeting mRNA transcribed from epithelial genes in bone marrow, peripheral blood, or lymph nodes. Several studies using RT-PCR thus far indicate a highly sensitive and specific staging tool, although the prognostic value is still controversial. However, limitations may arise from ectopic expression of marker mRNA in hematopoietic cells and deficient expression in circulating tumor cells. The present review focuses on the relevant literature and demonstrates the range of current applications of RT-PCR-based assays for detecting disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. We will both summarize technical evaluations of published molecular approaches and discuss the widely disparate results on PCR findings in clinical studies.

Molecular detection of cancer cells in bone marrow and peripheral blood of patients with operable breast cancer. Comparison of CK19, MUC1 and CEA using RT-PCR

We have compared three different RT-PCR procedures to measure cytokeratin 19 (CK19), carcinoembryonic antigen (CEA) and mucin MUC1 gene expression in order to determine their diagnostic value in detecting tumour cells in bone marrow aspirates of patients with operable breast cancer. In an experimental model, the best sensitivity was observed for CK19 and MUC1 RT-PCR assays, although only the CEA and CK19 assays showed good specificity. The study of 42 patients showed that a 'CK19 positive/CEA positive' RT-PCR assay in bone marrow correlated positively with a positive axillary lymph node status (N(0) versus N(1-3), P<0.05). Both assays were also positive in 17% of node negative patients. RT-PCR assays were more sensitive in bone marrow than in peripheral blood. Our results suggest that CK19 and CEA RT-PCR assays are powerful methods for detecting disseminated breast cancer cells. A larger study with long-term follow-up is required in order to clarify their clinical usefulness.

Bone marrow and lymph node assessment for minimal residual disease in patients with breast cancer

The immunocytological detection of disseminated epithelial cells in bone marrow in patients with breast cancer has been performed at many hospitals and institutes since the early 1980s. Despite numerous publications in this field, it has not been possible to standardize the method and establish the 'ideal' antibody, either nationally or internationally. Molecular biological methods using PCR technology could extend the diagnostic spectrum. However, one of the major problems in breast cancer is the lack of a disease-specific marker gene. As a result, immunocytology is still the standard procedure for tumour cell detection. The detection of disseminated single cells in bone marrow in primary breast cancer (also known as minimal residual disease) is a new prognostic factor for disease-free and overall survival. This has been demonstrated in two large (N > 300) groups and several small to medium groups (N = 50-300). As a marker of dissemination in a target organ for metastasis this prognostic factor corresponds much more closely to the tendency of breast cancer to early haematogenic spread. Tumour cell detection may predict the course of the disease better than the axillary lymph node status. Bone marrow aspiration and detection of disseminated cells might replace lymph node dissection, at least in those patients with small tumours and no clinical signs of lymph node involvement. This strategy will soon be investigated in appropriate studies. Another possible clinical use might be in deciding on whether or not to give adjuvant systemic therapy to node-negative patients. Patients with positive tumour cell detection are at a higher risk of subsequent metastasis, even if the axillary nodes are histologically normal. The immunohistological or molecular biological detection of tumour cells in axillary lymph nodes might also be very useful, now that it has been shown that a considerable subset of patients determined to be node-negative by means of conventional methods, are positive according to these new techniques. These methods could be a useful supplement to sentinel node biopsy. A further potential use of this method is in monitoring therapy with new treatment modalities such as gene therapy and immunotherapy. Repeated bone marrow aspiration can provide information on the success of therapy in minimal residual disease (cytoreduction). Immunocytochemical investigation of individual cells may be useful in studying the pathogenesis of metastasis, in particular in the skeleton. Phenotyping of cells might allow statements to be made on the metastatic potential of cells and the question of cell dormancy. It remains to be hoped that this aspect of minimal residual disease will be granted more attention in future.