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ORAL 40 - Biology 1 (ID 154)
- Event: WCLC 2015
- Type: Oral Session
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
ORAL40.06 - Sarcomatoid Differentiation During Progression of Malignant Pleural Mesothelioma (ID 1161)
16:45 - 18:15 | Author(s): B. Vrugt
Malignant pleural mesothelioma (MPM) is a highly aggressive tumour with a high local recurrence rate and often a poor prognosis despite multimodal treatment. We evaluated the prognostic impact of morphological and immunohistochemical changes in sequential biopsies obtained from patients with MPM during disease progression.
Tissue microarrays were constructed from paraffin-embedded tissue samples of 36 MPM patients (26 epithelioid, 6 biphasic and 4 sarcomatoid) taken before induction-chemotherapy, during surgery and at the time point of tumour recurrence. Immunohistochemical staining for calretinin, cytokeratin 5/6 (CK5/6) and Wilm’s tumor-1 (WT-1) as well as the biomarkers mesothelin, osteopontin, and fibulin-3 was performed, and staining intensity and percentage of positively stained tumour cells scored semi-quantitatively. The results were correlated with clinico-pathological characteristics of the patients including overall survival (OS). To determine the prognostic value of the markers at the different time points, a multivariate analysis including all factors that were significant in univariate analysis was performed.
In 28% of patients with epithelioid or biphasic MPM, a transition towards biphasic or sarcomatoid growth pattern during disease progression was observed (Figure 1). This dedifferentiation was associated with significantly decreased immunoreactivity for WT-1 (p=0.03), calretinin (p=0.005), mesothelin (p=0.01) as well as a shorter OS (p=0.04). Figure 1 Overall, patients with epithelioid or biphasic MPM in the diagnostic biopsy had a significantly better OS (29 months; 95% confidence interval (CI): range 27-32 months) in comparison to patients with sarcomatoid MPM (5 months; 95% CI: 3-7 months) (p<0.0005). On multivariate analysis, male gender (p=0.04) and high fibulin-3 (p=0.02) in the pre-chemotherapy samples were found to be associated independently with shorter OS.
In patients with epithelioid or biphasic MPM, high fibulin-3 expression in pretreatment samples and gender are independent predictors of shorter OS. In up to one third of patients disease progression is accompanied by sarcomatoid differentiation, suggesting that factors such as molecular alterations involved in epithelial-to-mesenchymal transition (EMT) are contributing to disease course and clinical outcome. Alternatively, induction chemotherapy might contribute to this transition by promoting selection and outgrowth of therapy resistant tumor cells. Eventually, the different tumor biology of this subgroup of patients may be taken into account for the consideration of alternative patient handling.
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