Relationship between baseline metabolic ¹⁸F-FDG parameters and survival in malignant pleural mesothelioma

Objectives: In this analysis, we aimed to retrospectively evaluate our data on metabolic PET parameters in MPM patients and search if there is a prognostic importance of them in our epidemic MPM cases or not.

Methods: ¹⁸F-FDG PET/CT images of totally 45 patients (23 M, 22 F, mean age: 58.8±1.4) who were imaged for primary staging of MPM were re-evaluated retrospectively. Patients were followed up for median 24 months. Patients were followed up until today or death. After ceCT histopathological confirmation was made in all patients. Pleural thickness was calculated from CT images. Measurement was performed from the most explicit area. Relationship between genders, histopathological subtype of tumour, disease stage, SUVmax of pleural surface, pattern of uptake, MTV, TLG and overall survival was analysed. During statistical analysis patients were divided into groups according to below and above of the median values for age (58), pleural thickness (17.5mm), SUVmax (9.35), MTV (29.6ml) and TLG (166.7).

Results: Totally 45 (23 M, 22 F, mean age :58.8±1.4) patients with MPM consisted of 16 (36%) epithelial, 3 (7%) sarcomatoid and 11 (24%) mixt subtypes and were included to the analysis. Totally 5 (33%) patients had diagnosed as MPM but subtyping could not be performed. Totally 6 (13%) patients had limited pleural thickness and 39 (87%) had diffuse plural thickness. While mean pleural thickness was calculated as 19.4±2.5 mm its was ranged between 6 to 100 mm.In the evaluation of ¹⁸F-FDG PET/CT images, focal, diffuse and focal+diffuse uptake were detected in the pleural lesions of 8 (18%), 15 (33%) and 15 (33%) patients, respectively. ¹⁸F-FDG PET/CT was negative in 7 (16%) patients. Median SUVmax of ¹⁸F-FDG positive patients was calculated as 9.35 (min-max: 3-29.6). Moreover, pathological ¹⁸F-FDG uptake was seen in the mediastinal-hilar lymph nodes of 11 (24%) patients. Mean SUVmax of lymph nodes was calculated as 7.72±3.05. Multiple bone metastases were observed in one patient. MTV in the thorax was ranged between 3.74 and 801 ml (median: 29.6) while those values for TLG were 21.97 and 8051(median: 166.7), respectively. Although 8 (18%) out of 45 patients treated surgery alone, 37 (82%) received adjuvant chemo±radiation therapy following surgery. Totally 16 (35%) patients were died during median 24 months follow-up period. In the Kaplan-Meirer analysis estimated mean survival time was calculated as 63.53±6.4 months. Cumulative 5-year survival rate was 50.9%. Significant survival difference was found between cT1 vs cT2 (p=0.05) and cStage1 vs cStage2 (p=0.01) in the evaluation based on clinical stages. In the analysis of PET/CT parameters, difference between groups below and above of 166.7 median value for TLG was significant (p=0.02).However difference between groups based on 9.35 median value (p=0.19) for SUVmax and 29.6ml median value (p=0.46) for MTV were not statistically significant. In the univariate Cox-Regression analysis, age, clinical stage, pleural FDG uptake pattern and TLG in the multivariate Cox-analysis, age, pleural thickness, pleural FDG uptake pattern were found as significant prognostic factors.

Conclusion: Despite the limited reported study and limited included patient numbers, metabolic PET parameters seems to have a prognostic value in MPM. Results of our study are needed to confirm by prospective larger studies. Research Support: None