Clapper, Patti, Schweizer and Mason

Malignant Pleural Mesothelioma (MPM) is a disease primarily caused by exposure to asbestos that occurs in 2,000 to 3,000 people each year in the United States alone. Mesothelioma is a rare form of cancer that most commonly arises in the lining of the pleura, or thin membrane surrounding the lung. MPM is hard to diagnose and to treat, with a median overall survival rate ranging between 9 to 17 months. 

 

Although there has been significant scientific and medical progress over recent years, there remains no cure and many controversial issues over diagnosis and treatment, including what are the best methods of measuring responses to treatment. Most treatments for mesothelioma aim to palliate symptoms and improve survival times. While standard front line treatments have been accepted, much research remains to be done.

 

Evaluating responses to therapies for patients diagnosed with MPM also has been and remains very challenging. Different modalities have been used in therapy response evaluation to try to better predict disease progression, survival times, and prognosis.

 

Computed tomography (CT) and positron emission tomography (PET) scans are two important methods of imaging in evaluating therapy response in patients with MPM. CT scans have been widely utilized for the diagnosing, staging and monitoring of therapeutic responses in MPM. Another common imaging modality are PET scans, often using an analogue of glucose called FDG, or fluorodeoxyglucose.   Some evidence shows that FDG-PET scans may be able to predict patient outcome early and monitor response to therapy throughout the course of treatment.

 

In attempts to improve abilities to evaluate prognosis in patients with MPM who are undergoing chemotherapy, many studies are investigating different methods of measuring response rates to a variety of treatment methods. A recent study published in Lung Cancer (March 2010) evaluated the use of combined FDG-PET/CT in measuring response to therapy in patients diagnosed with MPM. The aim of the study was to evaluate which parameters using FDG-PET with CT could lead to better evaluation of response to treatment. 

 

Because the diffuse pattern of growth in mesothelioma makes the use of RECIST – response evaluation criteria in solid tumors- criteria difficult, this study used modified RECIST criteria more suitable for evaluating response rates with MPM. Forty one patients diagnosed with MPM and treated with pemetrexed and platinum based chemotherapy were selected. They were then evaluated by FDG-PET/CT within two weeks of beginning therapy and then again within two weeks after receiving three cycles of standard chemotherapy.

 

Due to the rarity of the disease, this study, as well as many others, was performed with small patient populations making it so that comparisons of PET-measurements and modified RECIST parameters are only partially available.  The study aim was to investigate which parameters using a combination FDG-PET/CT-imaging might be superior in evaluating mesothelioma malignancies.  

 

Results suggest there is an advantage to combining CT and FDG-PET imaging and using specific parameters for measuring therapy response as well as prognosis and survival times in MPM. The authors of the study suggest that a modified RECIST and FDG-PET/CT should be considered in the care of patients with mesothelioma as well as being included as a routine imaging evaluation. 

 

In addition to aiding early identification of positive or negative patient response, using multimodal imaging technology may also be helpful in assessing new systemic treatments for mesothelioma. Further studies, hopefully with larger groups of patients, are needed for definite conclusiveness on the best method of assessing therapy response for mesothelioma.