Challenges in the management of urothelial cancer : novel treatment, evaluation of biomarkers, and imaging techniques

Abstract

Urothelial cancer (UC) is the most common malignancy found in the urinary tract. The global annual incidence is approximately 430 000 new cases (Sweden: 3 200 new cases). Approximately one in four new UC patients being diagnosed has muscle-invasive disease. For curative intent, treatment involving surgical removal of the primary tumour remains the gold standard for locally advanced UC. Still, one in two patients relapses despite undergoing curative intended surgery or bladder-preserving radiotherapy. Platinum-containing regimens have been the standard treatment since the 1980s, despite only reaching an overall survival of about 1 year. During the last decade, merely one new chemotherapy has been approved for metastatic UC: vinflunine. The primary aim of this thesis was to improve the management of advanced and metastatic UC by evaluating experimental treatments and exploring predictive and prognostic biomarkers.

Paper I describes a patient with metastatic UC and with no available standard treatment options after failing platinum treatment. The patient received the tyrosine kinas inhibitor sorafenib in second-line for almost one year. Immunohistochemistry (IHC) analysis of this patient’s tumour revealed intermediate expression of vascular endothelial growth factor receptor 2 (VEGFR2) and high expression of platelet-derived growth factor receptor β, two key targets of sorafenib. In Paper II, the prognostic value of S100A4, S100A6, and VEGFR2, markers of metastasis, proliferation and angiogenesis, were analysed by IHC in tumour specimen from 83 UC patients following cystectomy of the urinary bladder. Expressions of these proteins were compared with overall and disease-free survival. High expression of VEGFR2 and low tumour stage were independently correlated with longer survival. No association was found for S100A4 or S100A6 in this cohort. The Phase I trial Vinsor (Paper III) was the first clinical study to assess safety of vinflunine plus sorafenib in metastatic UC patients, refractory to platinum. Primary endpoint was to define the recommended Phase II dose (RPTD). In patients treated with a start dose of vinflunine 280 mg/m2 the RPTD of sorafenib was 400 mg. In patients receiving vinflunine 320 mg/m2, the RPTD was not determined because of toxicity. The median overall survival was 7.0 months and the overall response rate was 41%. Predicting early response to treatment is of clinical importance in improving outcome. In Paper IV the predictive value of response evaluation with early 18F-FDG PET scans and plasma exosomes were analysed in a subset of Vinsor trial patients (Paper III). Results demonstrated that early changes on 18F-FDG PET predicted survival and RECIST based on subsequent CT scans. Plasma exosomes could be isolated and quantified, but analysis revealed no association to treatment response. In Paper V, the cytotoxic properties of the peptidase-enhanced alkylating agent melflufen was studied in vitro. In UC cell lines melflufen increased cell death compared to melphalan. Aminopeptidases were found to be of importance for melflufen efficacy in vitro and high expression of aminopeptidase N expression in UC tumour specimens was associated with longer overall survival.

In summary, the results of this thesis indicate that subsets of UC patients may have a clinical benefit of sorafenib and that combined treatment with vinflunine is safe and possibly increases treatment efficacy. VEGFR2 appears to have prognostic potential besides being a target for therapy. Early treatment assessment of metastatic UC patients with 18F-FDG PET holds predictive potential. Melflufen shows antitumoral effects in UC cell lines and could be a future novel chemotherapy against this cancer.