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The comparative accuracy of different pleural biopsy techniques in the diagnosis of malignant mesothelioma

Tuesday, August 5, 2008

Source: Histopathology

An early diagnosis of mesothelioma is one of the most important aspects of maximizing a patient’s prognosis. A number of studies have correlated early diagnosis with enhanced survival time, so the identification of the most efficient diagnostic technologies is an important aspect of contemporary mesothelioma research.

Physicians have developed a number of biopsy procedures for cancer diagnosis and some of these procedures are used to diagnosis pleural mesothelioma or peritoneal mesothelioma. There are two basic biopsy strategies for most forms of cancer diagnosis: closed biopsy and open biopsy. A closed biopsy refers to the removal of tissue samples from outside the body, using small incisions and the insertion of specific surgical tools for the removal of tissue. A “blind” biopsy refers to a closed biopsy where the physician has no visual indication where his or her instruments are actually taking tissue samples from. Image-guided biopsy refers to the use of CT, or another imaging modality, to guide the physician’s needle during a closed biopsy. An open biopsy traditionally refers to a biopsy completed during invasive surgery, where the physician has a wide view of the affected areas.

When a biopsy is taken for pleural mesothelioma, it is called a pleural biopsy and the same basic strategies apply: closed pleural biopsy refers to a biopsy where tissue samples are removed from the pleural cavity, while open pleural biopsy refers to a biopsy completed during a thoracotomy, a highly invasive surgical procedure that provides wide access to the pleural cavity through a large incision made on the patient’s side and the spreading of the patient’s ribs to facilitate access to the thorax. In contemporary times, an open pleural biopsy may refer to a biopsy conducted through video-assisted thorascopic surgery (VATS), which is a much less invasive procedure than is a thoracotomy.

From these descriptions here, it is easy to assume that open pleural biopsy would give a physician the greatest diagnostic accuracy, while a blind, closed pleural biopsy would provide the least. Even though this is true, the invasiveness of the thoracotomy is generally avoided where possible, so mesothelioma specialists have had to settle for other less accurate techniques when the symptoms displayed during patient presentation are not necessarily indicative of a more serious illness. Image-guided pleural biopsy and VATS have very much increased the accuracy of the less invasive techniques, but they are not yet universally deployed.

Researches from the United Kingdom have recently entered this discussion with their publication of an article that analyzed the accuracy of the aforementioned biopsy techniques.

Overview of the Study

The researchers analyzed the postmortem records of 45 patients who died from pleural mesothelioma at Llandough Hospital in Penarth, Wales in the UK. These records identified the various diagnostic tests completed for each patient, from biopsy procedure to immunohistochemical analysis, and they served as the researcher’s primary data set for their analysis. Among these 45 cases, there were 21 cases of epithelioid mesothelioma, 11 cases of biphasic mesothelioma and 13 cases of sarcomatoid mesothelioma. 41 of the 45 cases were diagnosed when the patient was still alive, while 4 were suspected of mesothelioma, but a diagnosis was never returned.

Of the diagnosed cases, 36 underwent a closed needle biopsy. 31 of these were “blind” biopsies and 5 were CT-guided. Within the same population of diagnosed cases, 21 patients underwent an open pleural biopsy through thoracotomy.

Results

The researchers found results similar to other researchers who have also looked at this question: open pleural biopsy was the most accurate and sensitive procedure, while a blind, closed biopsy was the least accurate. Of the 21 cases of open biopsy performed through thoracotomy, all 21 cases were correctly identified as pleural mesothelioma and the histological subtype was correctly identified in 20 of the 21 cases. The blind biopsies were considerably less accurate and often required multiple procedures to return a diagnosis. When the procedures were quantified, the authors reported a diagnostic accuracy of only 16% of the 31 cases.

However, the accuracy of CT-guided closed biopsy was again confirmed. All five of the CT-guided cases returned an accurate diagnosis on the first attempt at biopsy, for a diagnostic accuracy of 100%—a figure that is directly comparable to thoractomy. Five is a rather small number though, and the other studies that have looked at image-guided biopsy have returned accuracy results in the high 80s or low 90s. That said, CT-guided biopsy is clearly a highly accurate diagnostic method.

Conclusion

This article is the latest among a number of recent publications that confirms the poor diagnostic accuracy of blind biopsy techniques. While open biopsy remains the surest way to determine a diagnosis, the use of CT-guided, or other image-based, closed biopsy has also shown a remarkable accuracy in the diagnosis of mesothelioma. These techniques are much less invasive and can be conducted under less extreme situations. Along with immunohistochemical analysis, as well as other pathology and marker tests, these diagnostic advances have enabled physicians to diagnose the disease much earlier than they ever have been able to. Because of this, patients can begin treatment at an earlier point in time, which may extend their survival time. Even as mesothelioma remains without a cure, recent improvements in diagnostics and patient survival are cause for some hope.

Labels: diagnosis, mesothelioma

posted by Belluck & Fox at 4:08 PM
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