Different imaging techniques can have different sensitivity in evaluating the response of malignant pleural mesothelioma (MPM) patients to chemotherapy, but a new study found a technique called 18F-FDG-PET/CT to be superior to others, and it called for the method’s inclusion in treatment assessments to help identify those not likely to respond to chemotherapy.
The study, “Metabolic Response Assessment With 18F-FDG-PET/CT Is Superior To Modified RECIST For The Evaluation Of Response To Platinum-Based Doublet Chemotherapy In Malignant Pleural Mesothelioma,” was published in the European Journal of Radiology.
Monitoring cancer patients’ response to chemotherapy is widely seen as a crucial step in improving outcomes and reducing mortality risk, but there is no consensus on which technique is best to evaluate the response in those with MPM.
In the study, researchers used two techniques to analyze cancer response in 82 MPM patients. The patients had all gone through three chemotherapy cycles with either cisplatin and pemetrexed or carboplatin and pemetrexed. The imaging techniques, mRECIST and integrated 18F-FDG-PET/CT — the latter of which has the capacity to depict metabolic abnormalities in cells — were used to assess MPM response to chemotherapy in each patient.
Non-responder patients were defined as those with an increase of 25 percent or more in SUVmax (a measure of cancer cell activity), compared with previously measured values. The team also compared time to cancer progression (TTP) and overall survival (OS) between patients who responded to treatment and those who did not.
Results using mRECIST criteria indicated that 62 (75.6 percent) of the 82 patients were considered to have stable disease, 15 (18 percent) showed cancer partial remission, and five (six percent) had progressive disease. The cumulative mean OS and TTP in this group were 728 days and 365 days, respectively.
The number of patients considered to have partial remission and progressive disease using the mRECIST method was corroborated by the 18F-FDG-PET/CT method, and it identified them all as being metabolic responders. But the number of responder patients with stable disease differed here. Among the 62 mRECIST stable-disease patients, 18 (29 percent) were classified as non-responders by the 18F-FDG-PET/CT technique.
Median time to cancer progression was about 14 months for responders and 10 months for non-responders.
The analysis showed that responders tended to have longer overall survival, but the finding was not considered statistically significant.
Together, the results indicate that the mRECIST technique may classify certain patients as having had a successful response to chemotherapy, while the 18F-FDG-PET/CT method might not agree. The latter could offer the more accurate assessment, the researchers said, because it was closely linked to actual time to cancer progression in the patients.
“Metabolic response is significantly correlated with the median TTP, suggesting it should be included in the evaluation of the response to chemotherapy in MPM patients classified as mRECIST SD, to identify non-responders,” the team concluded.