Mesothelioma Tumor Response to Chemotherapy
Mesothelioma, a cancer primarily caused by exposure to asbestos, begins in the lining of the lung (pleura), heart (pericardia) or abdomen (peritonea). Malignant pleural mesothelioma is the most common form. Standard frontline treatments for mesothelioma are surgery, chemotherapy and radiation, or some combination of the three. Because chemotherapy is almost always used to treat mesothelioma, researchers are investigating the best way to measure tumor volume and response to treatment.
Measuring tumor volume can be problematic in malignant pleural mesothelioma because tumors exhibit variable versus spherical patterns of growth. A recently published article in the European Journal of Radiology suggests that the volumetric method is a suitable method for measuring chemotherapy response. The “modified RECIST” is another measurement technique that can be used, measuring tumor thickness and volume changes, and corresponds with the volumetric method.
In this study from Turkey, fifty seven patients who were diagnosed with malignant pleural mesothelioma were evaluated for response to chemotherapy. Computed tomography (CT), modified RECIST, and World Health Organization (WHO) methods were all evaluated as ways to measure tumor volume.
Computed tomography is a powerful, non-destructive technique that produces two and three dimensional images of the tumors from X-ray images. CT scans can reveal the dimensions, shape, internal defects and density of masses in the body. Typically CT scans measure tumors from two different sites and at three different levels. RECIST (Response Evaluation Criteria in Solid Tumors) is a uni-dimensional way of measuring solid tumors which was modified to more accurately assess the non-spherical growth and changes in mesothelioma tumors. A bi-dimensional response criteria has been established by WHO and used for many years, although is now seen as inadequate and insufficient.
The purpose of the study was to determine if three dimensional analysis was the most beneficial method in evaluating tumor response to extended survival times. From all three measurement methods, the overall median survival time varied from 10 month to 16 months. The researchers found drawbacks and poor evaluation with just the RECIST or WHO methods and recommend measuring tumors using the volumetric method.
Several limitations to the study were acknowledged: one, manual measurement of tumor volume was time consuming and tiring; two, the patient number was low; and three, patients with applied talc pleurodesis were not separately assessed. Despite this, recommendations remain to use three dimension measurement of tumor volume for evaluation. In the future, larger studies need to be taken to confirm the efficacy of this method and establish it as a routine method for measuring responses to chemotherapy in mesothelioma patients.