Parameter estimation of perfusion models in dynamic contrast-enhanced imaging: a unified framework for model comparison.

Patients follow-up in oncology is generally performed through the acquisition of dynamic sequences of contrast-enhanced images. Estimating parameters of appropriate models of contrast intake diffusion through tissues should help characterizing the tumour physiology. However, several models have been developed and no consensus exists on their clinical use. In this paper, we propose a unified framework to analyse models of perfusion and estimate their parameters in order to obtain reliable and relevant parametric images. After defining the biological context and the general form of perfusion models, we propose a methodological framework for model assessment in the context of parameter estimation from dynamic imaging data: global sensitivity analysis, structural and practical identifiability analysis, parameter estimation and model comparison. Then, we apply our methodology to five of the most widely used compartment models (Tofts model, extended Tofts model, two-compartment model, tissue-homogeneity model and distributed-parameters model) and illustrate the results by analysing the behaviour of these models when applied to data acquired on five patients with abdominal tumours.

Adoptive transfer of tumor-infiltrating lymphocytes in patients with metastatic melanoma: intent-to-treat analysis and efficacy after failure to prior immunotherapies.

PURPOSE: Adoptive cell transfer (ACT) using autologous tumor-infiltrating lymphocytes (TIL) was reported to yield objective responses in about 50% of metastatic patients with melanoma. Here, we present the intent-to-treat analysis of TIL ACT and analyze parameters predictive to response as well as the impact of other immunotherapies. EXPERIMENTAL DESIGN: Eighty patients with stage IV melanoma were enrolled, of which 57 were treated with unselected/young TIL and high-dose interleukin-2 (IL-2) following nonmyeloablative lymphodepleting conditioning. RESULTS: TIL cultures were established from 72 of 80 enrolled patients. Altogether 23 patients were withdrawn from the study mainly due to clinical deterioration during TIL preparation. The overall response rate and median survival was 29% and 9.8 months for enrolled patients and 40% and 15.2 months for treated patients. Five patients achieved complete and 18 partial remission. All complete responders are on unmaintained remission after a median follow-up of 28 months and the 3-year survival of responding patients was 78%. Multivariate analysis revealed blood lactate-dehydrogenase levels, gender, days of TIL in culture, and the total number of infused CD8+ cells as independent predictive markers for clinical outcome. Thirty-two patients received the CTLA-4-blocking antibody ipilimumab prior or post TIL infusion. Retrospective analysis revealed that nonresponders to ipilimumab or IL-2 based therapy had the same overall response rate to ACT as other patients receiving TIL. No additional toxicities to TIL therapy occurred following ipilimumab treatment. CONCLUSION: Adoptive transfer of TIL can yield durable and complete responses in patients with refractory melanoma, even when other immunotherapies have failed.