Volumetry: an alternative to assess therapy response for malignant pleural mesothelioma?

Abstract

The purpose of our study was to assess robustness of volumetric measurement of malignant pleural mesothelioma (MPM) before and after chemotherapy to modified RECIST (response evaluation criteria in solid tumours) criteria.30 patients with digitally available chest computed tomography (CT) scans before and after three cycles of chemotherapy were included. Three readers independently assessed tumour response using two different methods: 1) the modified RECIST criteria; and 2) the tumour volumetric approach using dedicated software (Myrian1; Intrasense, Paris, France). Inter-rater reliability of unidimensional and volumetric measurements was assessed using intraclass correlation. Tumour response classification for modified RECIST was compared to the volumetric approach applying unidimensional RECIST volumetric equivalent criteria.The determination of unidimensional tumour measurement (RECIST) revealed a low inter-rater reliability (0.55) and a low interobserver agreement for tumour response classification (general k 0.33). Only 14 patients were classified equally. A high inter-rater reliability (0.99) and interobserver agreement (general k 0.9) were found for absolute tumour volumes (volumetric measurements). 27 cases were classified equally. The number of cases classified as ''stable disease'' was higher for the volumetric approach using tumour-equivalent criteria compared to modified RECIST.Volumetric measurement of MPM on CT using Myrian1 software is a reliable, reproducible and sensitive method to measure tumour volume and, thus, therapy response after induction chemotherapy.

Multimodal management of malignant pleural mesothelioma: where are we today?

“…These were recently optimised with only one cut-off value yielding two response categories, although further prospective validation is necessary [7]. Newer software allowing more precise tumour volume measurements will probably increase the staging accuracy in the near future [8,9]. Lung volume measurements can be considered a surrogate marker for patient response, as it has recently been demonstrated that increasing disease volume and decreasing lung volume are associated with a poor prognosis [10].…”

Volumetric assessment in malignant pleural mesothelioma

“…Clinical staging of MPM using current imaging modalities does not accurately predict either pathologic stage or prognosis and is plagued by high interobserver variability (17)(18)(19). This is not surprising since the pathologic classification is based on microscopic assessment of tumor invasion at a cellular scale that is well beyond the spatial resolution of any combined multi-modality approach.…”

“…These methods are based on the measurement of maximal tumor thickness in one or more anatomical planes. Due to the aforementioned difficulties in measuring MPM these methods have found to be unreliable, with high inter-and intra-observer variation when compared with volumetric analysis (19).…”

“…Tumor volume measurement on CT has similarly been found to be useful in assessing treatment response. Liu et al assessed treatment response in patients with MPM by measuring tumor volume on CT before and after therapy, finding that tumor volume reduction post treatment is significantly associated with improved survival, and that patients with a tumor volume of less than 620 cm found that tumor volume measurement on CT is a more reliable measure of chemotherapy response and predictor of outcomes in MPM than RECIST (19).…”

Imaging in pleural mesothelioma: A review of the 12th International Conference of the International Mesothelioma Interest Group

“…The potential role of image-based mesothelioma tumor volume in staging [6], the impact of volume on tumor response assessment [7][8][9][10], the correlation between tumor volume and patient survival [7][8][9]11], and the computerized extraction of mesothelioma tumor volume from CT scans [12] have all been the subject of recent investigation. Mesothelioma, however, presents a unique challenge for image-based tumor volumetrics; before mesothelioma tumor volume can be adopted for clinical application, it is essential to understand the correlation between tumor volume derived from images and the actual, physical tumor bulk that the images represent.…”