Jun 29, 2012 - Mesothelioma Treatment May Make Monitoring the Cancer More Difficult
A relatively common treatment for mesothelioma can interfere with future monitoring of the disease and may make reliable prognosis and treatment more difficult. That’s the conclusion of a new study in the June issue of the Journal of Cancer. The study examined the medical history of patients who underwent a procedure called talc pleurodesis and discovered that it made accurate monitoring through FDG-PET/CT scans afterward nearly impossible.
Talc pleurodesis is a procedure during which talc is injected into the intra-membranous space of the pleura, or thin lining surrounding the lungs. This space is filled by a viscous fluid that is used in healthy patients as a lubricating agent so the lungs and other organs can move within the body cavity without causing friction, which would damage the organ’s sensitive tissue. However, in patients with pleural mesothelioma, an excess of fluid is often present. This excess fluid increases the pressure within the chest cavity, making breathing difficult and inducing pain.
Talc pleurodesis is a procedure meant to alleviate this painful symptom of mesothelioma. This type of pleurodesis is done using talc slurry, usually a mixture of sterile talc, sodium chloride and a local anaesthetic such as lidocaine 1%. The mixture is then introduced via a chest drain and is useful in patients who wish to avoid surgery where there would be an increased risk of complications. It is a relatively simple procedure and has been successful in the treatment of recurrent effusions (Doddoli et al, 2004).
FDG-PET scans are widely accepted as the best method for detecting and monitoring mesothelioma tumors. The process involves injecting a radioactive tracer element before using positron emission tomography and computerized tomography scanning (PET/CT) to spot possible malignant mesothelial cells. Because this radioactive tracer is absorbed differently in cancer cells than in healthy cells, experts can generally spot the cancerous lesions easily.
In addition, during chemotherapy treatment, doctors can judge how effective the treatment is by measuring the ability of the cancer cells to absorb this radioactive tracer.
An Italian team of researchers examined the medical records of eight individual mesothelioma patients who had previously undergone chemotherapy and talc pleurodesis. The same patients were scanned using FDG-PET/CT at about 14 days after their talc treatment and once after 125 days. Unfortunately, they discovered that the talc actually changes the rates at which the cancer cells absorb the radioactive tracer used during the PET/CT scans. This effectively makes it appear as if the patient’s cancer is progressing at a much faster rate than it actually is or that it isn’t responding well to chemotherapy when it actually may be.
This false test result may cause primary doctors to change the method of treatment, discontinue chemotherapy, or opt for radical procedures which carry a much higher risk to the patient and their quality of life.
The Italian team suspects that with further study scientists may be able to create a sort of sliding scale which they could use to judge the progression of the mesothelioma without interference from the talc. Effectively, this new measurement tool would account for the talc, thereby compensating for the increased “uptake” of the radioactive tracer and provide a more accurate picture of how the individual’s cancer is progressing or responding.
Until such a scale is created, however, mesothelioma specialists must be made aware of this fact and must compensate to the best of their abilities in order to provide the highest quality of care to their patients.
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