Automated screening for micrometastases in bone marrow smears

Markers of circulating breast cancer cells

The detection of circulating tumor cells (CTC) aids in diagnosis of disease, prognosis, disease recurrence, and therapeutic response. The molecular aspects of metastasis are reviewed including its relevance in the identification and characterization of putative markers that may be useful in the detection thereof. Also discussed are methods for CTC enrichment using molecular strategies. The clinical application of CTC in the metastatic disease process is also summarized.

Circulating tumour cells in clinical practice: Methods of detection and possible characterization

Circulating Tumour Cells (CTCs) can be released from the primary tumour into the bloodstream and may colonize distant organs giving rise to metastasis. The presence of CTCs in the blood has been documented more than a century ago, and in the meanwhile various methods have been described for their detection. Most of them require an initial enrichment step, since CTCs are a very rare event. The different technologies and also the differences among the screened populations make the clinical significance of CTCs detection difficult to interprete. Here we will review the different assays up to now available for CTC detection and analysis. Moreover, we will focus on the relevance of the clinical data, generated so far and based on the CTCs analysis. Since the vast majority of data have been produced in breast cancer patients, the review will focus especially on this malignancy.

Circulating tumor cells (CTCs): detection methods and their clinical relevance in breast cancer

The enumeration of circulating tumor cells has long been regarded as an attractive diagnostic tool, as circulating tumor cells are thought to reflect aggressiveness of the tumor and may assist in therapeutic decisions in patients with solid malignancies. However, implementation of this assay into clinical routine has been cumbersome, as a validated test was not available until recently. Circulating tumor cells are rare events which can be detected specifically only by using a combination of surface and intracellular markers, and only recently a number of technical advances have made their reliable detection possible. Most of these new techniques rely on a combination of an enrichment and a detection step. This review addresses the assays that have been described so far in the literature, including the enrichment and detection steps and the markers used in these assays. We have focused on breast cancer as most clinical studies on CTC detection so far have been done in these patients.

Clinical significance of bone marrow microinvolvement in nonsmall cell lung carcinoma

BACKGROUND

The divergences in the clinical significance of bone marrow microinvolvement (BMM) in patients with nonsmall cell lung carcinoma (NSCLC) necessitated a long-term large series study.

METHODS

Between March 1997 and June 2001, the authors analyzed 212 bone marrow specimens (from the posterior iliac crest) taken from patients with NSCLC before surgery. The degree of tumor differentiation included well differentiated carcinoma in 12 Patients, moderately differentiated carcinoma in 112 Patients, and poorly differentiated carcinoma in 68 Patients. The pTNM staging (according the the criteria of the American Joint Committee on Cancer) included Stage IA in 8 patients, Stage IB in 70 patients, Stage IIB in 36 patients, Stage IIIA in 54 patients, Stage IIIB in 14 patients, and Stage IV in 10 patients. The specimens were evaluated by immunohistochemical staining with antihuman cytokeratin AE1/AE3, Ber-EP4, and clone MNF116 mixed solution to detect the presence of malignant epithelial cells in the bone marrow.

RESULTS

Positive results were observed in 66 patients (34.4%). The occurrence of BMM was not found to be related to patient age, gender, cell type, or TNM status. The 5-year disease-free survival rates were 44.9% and 40.5% in BMM-negative and BMM-positive patients, respectively (P = 0.3797). The 5-year cumulative survival rates were 43.5% and 44.0% in BMM-negative and BMM-positive patients, respectively (P = 0.4262). Multivariate analysis failed to demonstrate BMM as an independent prognostic factor (P = 0.1817).

CONCLUSIONS

The results of the current study showed that although BMM was observed frequently in patients with NSCLC, regardless of tumor stage and pathologic types, its occurrence was not a good predictor of long-term prognosis.

Use of automated microscopy for the detection of disseminated tumor cells in bone marrow samples

The use of automated microscopy has reached the maturity necessary for its routine use in the clinical pathology laboratory. In the following study we compared the performance of an automated microscope system (MDS) with manual method for the detection and analysis of disseminated tumor cells present in bone marrow preparations from breast carcinoma patients. The MDS System detected rare disseminated tumor cells among bone marrow mononuclear cells with higher sensitivity than standard manual microscopy. Automated microscopy also proved to be a method of high reproducibility and precision, the advantage of which was clearly illustrated by problems of variability in manual screening. Accumulated results from two pathologists who had screened 120 clinical slides from breast cancer patients both by manual microscopy and by use of the MDS System revealed only two (3.8%) missed by the automatic procedure, whereas as many as 20 out of 52 positive samples (38%) were missed by manual screening.

Detection of occult metastasis in patients with breast cancer

The most important factor affecting the outcome of patients with invasive cancer 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 routinely employed methods (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. 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.

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.

Bone-marrow microinvolvement in non-small cell lung cancer is not a reliable indicator of tumour recurrence and prognosis

AIMS

This study aimed to examine the incidence of bone-marrow microinvolvement in non-small cell lung cancer (NSCLC) patients and its correlation with tumour recurrence and prognosis.

METHODS

Between March 1997 and August 1998, we analysed 96 bone-marrow specimens (from the posterior iliac crest) of NSCLC patients before surgery. Tumour differentiation showed well differentiated carcinoma in six, moderately differentiated carcinoma in 69, and poorly differentiated carcinoma in 21. p-TNM staging showed stage Ia in five, stage Ib in 33, stage IIb in 19, stage IIIa in 26, stage IIIb in eight, and stage IV in five. The specimens were examined by immunohistochemical staining with anti-human cytokeratin AE1/AE3 and clone MNF116 mixed solution (Ab1, n=96) and/or Ber-EP4 (Ab2, n=80) to detect the presence of malignant epithelial cells in the bone marrow.

RESULTS

Positive results were observed in 21 patients (21. 9%). The occurrence of bone-marrow microinvolvement was not related to patient age, sex, cell type, or TNM status. The 30-month disease-free survival rates were 50.2% and 53.9% in bone-marrow negative and bone-marrow positive patients, respectively (P=0.5670); the 30-month cumulative survival rates were 66.7% and 67.6% in bone-marrow negative and bone-marrow positive patients, respectively (P=0.9351). Multivariate analysis failed to demonstrate bone-marrow microinvolvement as an independent prognostic factor.

CONCLUSIONS

Our results show that bone-marrow microinvolvement is not unusual, and its occurrence cannot be translated into early tumour recurrence or poor outcome during an intermediate-term follow-up, which means bone-marrow microinvolvement may be an epiphenomenon rather than true metastasis in NSCLC.

Detection of occult metastases in lung carcinomas: progress and implications for lung cancer staging

The ability to detect occult regional and systemic metastases in patients with operable lung carcinoma could have a significant impact on the management of the disease. Here, we review the literature, including studies from our own laboratory, regarding the clinical significance of the presence of occult metastases in patients with lung cancer. The accumulated evidence strongly suggests that the detection of occult regional and systemic metastases is an important predictor of disease progression. The use of this method should be considered in the future design of lung cancer clinical trials, at the very least. The detection of occult metastases should have an impact on lung cancer management; to reflect this, we propose a change in the TNM staging system to indicate the presence or absence of occult regional (lymph node) and systemic (bone marrow) metastases. The proposed change is TNnMm, where n and m are occult nodal and bone marrow metastases status.

Strategies for rare-event detection: an approach for automated fetal cell detection in maternal blood

This article explores the feasibility of the use of automated microscopy and image analysis to detect the presence of rare fetal nucleated red blood cells (NRBCs) circulating in maternal blood. The rationales for enrichment and for automated image analysis for "rare-event" detection are reviewed. We also describe the application of automated image analysis to 42 maternal blood samples, using a protocol consisting of one-step enrichment followed by immunocytochemical staining for fetal hemoglobin (HbF) and FISH for X- and Y-chromosomal sequences. Automated image analysis consisted of multimode microscopy and subsequent visual evaluation of image memories containing the selected objects. The FISH results were compared with the results of conventional karyotyping of the chorionic villi. By use of manual screening, 43% of the slides were found to be positive (>=1 NRBC), with a mean number of 11 NRBCs (range 1-40). By automated microscopy, 52% were positive, with on average 17 NRBCs (range 1-111). There was a good correlation between both manual and automated screening, but the NRBC yield from automated image analysis was found to be superior to that from manual screening (P=.0443), particularly when the NRBC count was >15. Seven (64%) of 11 XY fetuses were correctly diagnosed by FISH analysis of automatically detected cells, and all discrepancies were restricted to the lower cell-count range. We believe that automated microscopy and image analysis reduce the screening workload, are more sensitive than manual evaluation, and can be used to detect rare HbF-containing NRBCs in maternal blood.

Detection of 'rare event' fetal erythroblasts in maternal blood using automated microscopy

This paper describes the use of automated microscopy to detect fetal erythroblasts in maternal blood. The technology is based on the following approach: (1) the use of centrifugal cytology for the preparation of monolayers; (2) simultaneous staining of fetal hemoglobin (immunoalkaline phosphatase) and chromosome sequences (FISH); (3) multi-mode microscopy to detect rare events; (4) visual evaluation of image memories containing detected objects. Model systems show that fetal cells in frequencies as low as 1 in a million cells can be detected easily (manually or by automated microscopy). Algorithms for automated cell selection were developed for a test set of 6 patients. Optimization of hardware and software routines will make analysis of several million cells in approximately 1 h feasible.

Skip metastasis to the mediastinal lymph nodes in non-small cell lung cancer

BACKGROUND

Whether any difference exists in clinical characteristics between resected non-small cell lung cancer with either skip or ordinary mediastinal lymph node metastases (N2 disease) needs to be clarified.

METHODS

There were 110 patients with stage IIIA N2 disease. Thirty-three patients demonstrating no metastasis at the hilar nodes [skip (+) group] were compared with the other 77 patients [skip (-) group]. To investigate the extent of nodal involvement, we classified the mediastinal lymph nodes into three regions (superior, inferior, or aortic).

RESULTS

There were no significant differences regarding histologic type, T status, or the site of the primary tumors between the skip (+) and the skip (-) N2 groups. In the skip (+) group, mediastinal node metastasis was found in only one region (level 1) in 30 patients (90.9%) and in two regions (level 2) in 3 (9.1%), whereas 28 patients (36.4%) from the skip (-) group revealed mediastinal metastasis at two or three regions (level 2 or 3). The overall survival rate at 5 years after operation was 35% in the skip (+) group and 12.7% in the skip (-) group (p = 0.054). This favorable clinical outcome in the skip (+) group could be explained partially by the higher proportion of patients with level 1 metastases. Furthermore, regarding patients with level 1 disease, the skip (+) group tended to have a better prognosis than the skip (-) group (p = 0.096).

CONCLUSIONS

These results suggest that patients with skip mediastinal lymph node metastases represent a unique subgroup of N2 disease.

Detection of minimal disease in patients with solid tumors

The detection and elimination of minimal systemic disease in patients with solid tumors is one of the main current topics in clinical oncology. The present review focuses, therefore, on new diagnostic approaches to identify minimal disease in peripheral blood, bone marrow, and lymph nodes of patients with epithelial cancer as the major type of solid tumors in Western industrialized countries. These approaches may be used to improve tumor staging and monitoring of adjuvant therapies, as well as to detect tumor cell contamination in autologous stem cell grafts. Most investigators have developed either immunocytochemical assays with monoclonal antibodies to a variety of epithelial-specific cytoskeleton and membrane antigens or molecular methods based on the extensive amplification of a specific (c)DNA sequence by the polymerase-chain reaction (PCR). In immunocytochemical assays, antibodies to cytokeratins can be regarded as the most specific and sensitive probes to detect isolated epithelial tumor cells in bone marrow and blood. Molecular methods are based on the detection of either mutations in oncogenes and tumor suppressor genes (e.g., ki-ras and p53 genes) or the mRNA expression of tissue-specific and tumor-associated genes. mRNA species targeted in these assays encode cytokeratins, prostate-specific antigen, prostate-specific membrane antigen, carcinoembryonic antigen, and polymorphic-epithelial mucin. To introduce the available methods into clinical practice, standardized protocols need to be developed and validated in multi-center studies.

Detection of immunocytochemically stained rare events using image analysis

The detection of rare-event cells circulating in peripheral blood using automated image analysis was evaluated using a model system consisting of cells from a breast cancer cell line (SKBR3) seeded in a mononuclear cell suspension. Slides of cells with optimal morphology were prepared according to an optimized preparation procedure based on centrifugal cytology in combination with formalin fixation. SKBR3 cells were immunocytochemically stained for cytokeratin using the cam 5.2 monoclonal antibody and labelled with alkaline phosphatase using CAS-red as substrate. Because, for optimal segmentation of cell images, plain differences in absorption wavelength are required, the red immunostaining was combined with a green nuclear counter-staining based on ethyl green. Slides were automatically screened for cytokeratin-positive SKBR3 cells resulting in a lowest detectable frequency of one positive cell per 1.87 x 10(6) negative cells. A comparison between manual screening and automated screening for cytokeratin-positive cells showed a high level of correlation (0.9998). For the definition of the total number of objects per slide, two counting procedures were evaluated. Results were close to the visual score with a coefficient of variation of 0.47% for the counting procedure used in this study. It is concluded that optimization of preparation and staining procedures for the detection of rare-event cells using automated image analysis results in optimal image contrast and, consequently, in an increase in sensitivity for detecting rare events.

Automated image cytometry for detection of rare, viral antigen-positive cells in peripheral blood

A cell detection method based upon automated screening is described for recognition of low frequencies (1 in 100,000) of immuno-enzymatically labelled white blood cells in human peripheral blood. The used image cytometry instrumentation (LEYTAS) includes a wide-field, fully automated microscope (Autoplan) and a modular image analysis computer (MIAC), both from Leica, Wetzlar, Germany. The MIAC contains image boards for optimum use of mathematical morphology algorithms. Communication with the MIAC is via a personal computer. Programs for automated cell analysis have been written in C language. Main features of the system are fast analysis of large microscope fields including a count of all cells, selection of objects of interest (alarms), and display of digitally stored images of these alarms. We tested this system for the detection of white blood cells expressing antigen of cytomegalovirus (pp65) in 50 human blood smears from kidney transplant recipients. Immuno-enzymatic (peroxidase) staining was performed with DAB and counterstaining with hematoxylin. For determination of the sensitivity, a series of dilutions of a positive sample with a negative sample was performed. The lowest frequency detected was 1 antigen-positive cell/3 x 10(5) antigen-negative cells. Screening time was about 60 min for one million cells.

Bone marrow micrometastases in primary breast cancer: prognostic significance after 6 years' follow-up

Using an antiserum to epithelial membrane antigen we have screened multiple bone marrow aspirates from 350 patients with primary breast cancer taken at the time of initial surgery. 89 (25%) patients were found to have micrometastases and their presence was related to pathological size (P less than 0.01), the presence of peritumoral vascular invasion (P less than 0.001), and positive lymph nodes (P less than 0.005) but not menopausal status. At a median follow-up of 76 months (range 34-108) 107 patients had relapsed with distant metastases. 48% (43 of 89) of these patients had micrometastases initially compared with 25% (64 of 261) who did not (P less than 0.005). The test predicts for relapse in bone (P less than 0.01) and other distant sites excluding bone (P less than 0.001) and is associated with a shorter overall survival (P less than 0.005). We conclude that the detection of micrometastases signals a high likelihood of early relapse and decreased survival in breast cancer.

Detection of micrometastatic tumor cells in bone marrow of breast carcinoma patients

To determine the incidence and clinical significance of micrometastases in the bone marrow of breast carcinoma patients, we performed an immunoalkaline phosphatase assay using anticytokeratin (AE1, AE3, MAK-6) and antiepithelial (113F1, 260F9, 317G5) antibodies on the bone marrow aspirates of 71 stage IV disease patients with either recurrent regional or distant metastases. Although we detected tumor cells within the bone marrow of 38% of these patients with this assay, no significant correlation was seen with patient's age, menopausal status, bone scan, bone marrow core histology, response to induction chemotherapy, number of metastatic sites, dominant site of metastasis, or subsequent clinical outcome. The clinical parameters that were associated with improved survival were one dominant site of metastatic disease and regional soft tissue recurrence without distant disease.

Micrometastases in breast cancer: long-term follow-up of the first patient cohort

"Micrometastases" can be identified in the bone marrow of patients with apparently localised breast cancer using an immunocytochemical stain for epithelial membrane antigen (EMA). Of 39 women who had marrow samples examined at the time of initial presentation (37), or with locally recurrent disease (2), 13 (33%) had samples which contained small numbers of EMA positive cells. 10 out of 23 (44%) lymph-node positive patients were marrow positive, compared to 1 out of 14 (7%) lymph node negative cases (P = 0.03). Long-term follow-up (median 9.5 years) has shown that 11 out of 13 (85%) patients with micrometastases have developed metastatic disease compared to 8 out of 26 (31%) with negative bone marrow aspirates (P less than 0.05). The small number of EMA positive cells detected in bone marrow samples probably reflects the high metastatic potential of primary or recurrent cancers rather than established microscopic deposits; it is not yet clear whether the finding of such micrometastases will act as an independent variable compared to established prognostic factors.