Biomarker assessments in asbestos-exposed workers as indicators for selective prevention of mesothelioma or bronchogenic carcinoma: rationale and practical implementations

Clinical utility of hyaluronic acid values in serum and bronchoalveolar lavage fluid as tumor marker for bronchogenic carcinoma

Various authors have proposed the use of hyaluronic acid (HA) as a tumor marker. In order to analyze its usefulness as a marker in bronchogenic carcinoma, the most common carcinoma in men, we determined the HA values in serum and bronchoalveolar lavage fluid (BAL). We performed prospective studies on two groups of patients: 81 diagnosed as having bronchial carcinoma and 34 with benign respiratory diseases.

HA values were higher in patients with cancer than in those with benign diseases (serum: 79.8 ng/ml vs 63.7 ng/ml; BAL: 927 ng/mg vs 522 ng/mg). Also, the percentage of patients with levels exceeding the established cutoff was greater in the group with cancer than in the group with benign diseases (serum: 24.6 vs 17.6; BAL: 25.3 vs 3). Statistically significant differences in these percentages were found in BAL (p<0.01). Patients with extended small cell carcinoma had higher HA values (p=0.04) than those with limited disease, and the percentage of patients with abnormal HA values was larger in the group with extended disease than in the group with limited disease (p=0.004). The serial determinations of HA values in serum reflected the clinical evolution after treatment in 73% of the small cell carcinomas. Most of the patients with benign diseases whose HA values exceeded the cutoff level suffered from acute infectious dis-eases. Once these cases were excluded, the specificity of HA value determination in the diagnosis of carcinoma was very high (serum 96%, BAL 100%). The determination of HA levels in serum or BAL did not have any prognostic value in this study.

We conclude that the HA levels in serum and BAL could be of interest as a tumor marker, especially in patients with small cell carcinoma.

Soluble markers for diagnosis of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive and invasive tumor, whose incidence is expected to peak, in many countries, at the end of the present decade, 20–40 years after the peak of asbestos use (asbestos being the most important etiological factor). MPM has a poor prognosis, in part, owing to a difficult and often late diagnosis hindered by a lack of available tests able to diagnose or predict this cancer in its early stages. Recently, there has been increased interest in noninvasive, economic and well-accepted diagnostic tests for screening of asbestos-exposed subjects, as well as for monitoring response of MPM patients to treatment. Several markers have been studied in biofluids, such as serum, plasma and pleural effusions, especially using ELISA, and some of them are still under investigation. However, only mesothelin and ostepontin have proven levels of sensitivity and specificity that are worth testing in the clinical setting.

Current status of screening for malignant pleural mesothelioma

Malignant mesothelioma is characterized by its association with asbestos, its long latency period, and the propensity for the diagnosis to be obtained in the later stages of the disease. Because the high-risk cohorts for mesothelioma are fairly well defined by the association with asbestos, and the exposure is usually in the workplace, it is hypothesized that early detection of the disease could (1) find patients at an earlier, more treatable stage and (2) result in prolonged survival over the present median 12 months from the start of therapy. Many studies have used standard chest X-ray to characterize changes associated with asbestos-exposed individuals, but the insensitivity of X-ray in screening patients with mesothelioma has never supported the wide-scale adaptation of such an effort. With the advent of computerized tomography, prospective trials, many of which are chiefly prevalence detection studies, have been performed and stress the importance for proper detailing by carefully qualifying suspicious changes, as well as defining the correct cohort to screen. Most recently, serum biomarkers with the potential to discriminate asbestos-exposed, non-cancer-bearing individuals from those with mesothelioma have been investigated both at single institutions and with multi-institutional-blinded trials. These markers, including soluble mesothelin-related protein, osteopontin, and megakaryocyte potentiating factor, may, in the future, be incorporated into a screening algorithm for high-risk asbestos-exposed individuals to help monitor these cohorts in a noninvasive fashion and guide the use of computerized tomography.

Sensitive and specific new enzyme-linked immunosorbent assay for N-ERC/mesothelin increases its potential as a useful serum tumor marker for mesothelioma

BACKGROUND

Because mesothelioma initially progresses on the surface of the pleura and peritoneum without forming masses, it has been difficult to diagnose at an early stage. It would be very useful to identify a tumor marker that could be used for screening to enable more diagnoses to be made at an early, treatable stage.

MATERIALS AND METHODS

We had previously identified N-ERC/mesothelin as a potential biomarker for mesothelioma. In the current work, we used a newly developed ELISA system to gain data on N-ERC/mesothelin levels in various clinical settings. A total of 102 healthy volunteers were recruited. In addition, 39 patients were diagnosed with mesothelioma, 53 patients were diagnosed with diseases that should be distinguished from mesothelioma, and 201 subjects were diagnosed with asbestos-related nonmalignant diseases (including simple exposure to asbestosis) who were treated at any of the cooperating hospitals were enrolled.

RESULTS

Serum N-ERC/mesothelin levels measured by a new ELISA system showed that the median values from patients with mesothelioma were extremely high compared with levels obtained from other patients. Analysis in terms of histologic type showed that serum levels of N-ERC/mesothelin were elevated in epithelioid type mesothelioma, especially. In four important models of clinical settings, the sensitivity and specificity of N-ERC/mesothelin were about 71% to 90% and 88% to 93%, respectively.

CONCLUSION

N-ERC/mesothelin is a very promising tumor marker for mesothelioma, especially epithelioid mesothelioma.

Asbestos exposure, pleural mesothelioma, and serum osteopontin levels

BACKGROUND

We investigated the presence of osteopontin in pleural mesothelioma and determined serum osteopontin levels in three populations: subjects without cancer who were exposed to asbestos, subjects without cancer who were not exposed to asbestos, and patients with pleural mesothelioma who were exposed to asbestos.

METHODS

A group of 69 subjects with asbestos-related nonmalignant pulmonary disease were compared with 45 subjects without exposure to asbestos and 76 patients with surgically staged pleural mesothelioma. Tumor tissue was examined for osteopontin by immunohistochemical analysis, and serum osteopontin levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

There were no significant differences in mean (+/-SE) serum osteopontin levels between age-matched subjects with exposure to asbestos and subjects without exposure to asbestos (30+/-3 ng per milliliter and 20+/-4 ng per milliliter, respectively; P=0.06). In the group with exposure to asbestos, elevated serum osteopontin levels were associated with pulmonary plaques and fibrosis (56+/-13 ng per milliliter) but not with normal radiographic findings (21+/-5 ng per milliliter), plaques alone (23+/-3 ng per milliliter), or fibrosis alone (32+/-7 ng per milliliter) (P=0.004). Serum osteopontin levels were significantly higher in the group with pleural mesothelioma than in the group with exposure to asbestos (133+/-10 ng per milliliter vs. 30+/-3 ng per milliliter, P<0.001). Immunohistochemical analysis revealed osteopontin staining of the tumor cells in 36 of 38 samples of pleural mesothelioma. An analysis of serum osteopontin levels comparing the receiver-operating-characteristic curve in the group exposed to asbestos with that of the group with mesothelioma had a sensitivity of 77.6 percent and a specificity of 85.5 percent at a cutoff value of 48.3 ng of osteopontin per milliliter. Subgroup analysis comparing patients with stage I mesothelioma with subjects with exposure to asbestos revealed a sensitivity of 84.6 percent and a specificity of 88.4 percent at a cutoff value of 62.4 ng of osteopontin per milliliter.

CONCLUSIONS

Serum osteopontin levels can be used to distinguish persons with exposure to asbestos who do not have cancer from those with exposure to asbestos who have pleural mesothelioma.

Current controversies regarding the role of asbestos exposure in the causation of malignant mesothelioma: the need for an evidence-based approach to develop medicolegal guidelines

Asbestos is a group of fibrous silicate minerals that includes two mineralogic groups: amphiboles and serpentines. While the carcinogenic role of amphiboles (eg, crocidolite and amosite) is well established, medical "experts" that tend to strongly advocate their views currently argue in medicolegal cases multiple specific issues regarding the carcinogenicity of asbestos fibers. For example, it is controversial whether chrysotile causes malignant mesothelioma (MM); what are the specific carcinogenic thresholds for amphiboles and chrysotile; what occupations are truly at risk to develop MM as a result of asbestos exposure; what is the role of chrysotile in the development of peritoneal MM; how to assign causation in individuals exposed to multiple industrial products containing variable concentrations of various asbestos fibers; and, what criteria should be used to accept causation in household exposure cases and others. The causation criteria currently acceptable in U.S. courts are surprisingly flexible and subject to variable interpretation by medical "experts." At a time where thousands of individuals are claiming causation of MM by asbestos exposure, there is a need to develop more specific causation guidelines based on scientific evidence. Evidence-based medicine has been proposed as a new approach to the study, teaching, and the practice of medicine and has been used as a process of systematically reviewing the relevant studies in the literature to assess their scientific validity and development of guidelines. This article summarizes some of the current controversies regarding the role of asbestos exposure in the causation of MM and suggests the need for future evidence-based medicine-type studies to develop causation guidelines that could be used consistently during litigation.