Caractérisation des propriétés biophysiques du stroma dans le cancer humain : vers une oncologie computationnelle personnalisée (DCE-MRI)

Patients will undergo an MR scan before undergoing cytoreductive surgery. If neoadjuvant chemotherapy is administered, an extra MR scan is planned before the start of the neoadjuvant chemotherapy.

During surgery, tissue samples will be taken for interstitial fluid pressure (IFP) measurement, immunohistochemistry (IHC) and characterization of biophysical properties (viscoelastic properties and hydraulic conductivity).

A flat-ended cylindrical indentation tip, with 5 mm diameter, will be attached to a load cell to indent the sample. After the initial contact, the control algorithm will drive the tip to indent a given depth (30% of sample's height) into the test material at a constant velocity (1 mm/s). After reaching the prescribed depth, the position of the indentation tip will be fixed at this value for a given amount of time (300 s) in order to start the stress relaxation process. Units: Pa = kg m-1 s-2

The hydraulic conductivity of samples will be measured by detecting the amount of fluid exchange through the sample due to a hydrostatic pressure gradient in a closed system. The system includes two EasyMount Ussing diffusion chambers placed in a 2-channel EasyMount stand (Physiologic Instruments, Inc.; San Diego, CA), pressure reservoirs (syringes), and a bubble tracker device for measuring the liquid exchange.

The nominal hydraulic conductivity (K') will be calculated by:

K'=〖(d/D)〗^2 L/ρgh ∆x/∆t Where L and D are the tissue thickness and tissue area (interface), d is the glass tube diameter, ρ is the liquid density, h is the liquid column height, g is the gravity acceleration, x is bubble displacement and t is time.

Develop and validate a computational fluid dynamics (CFD) model to calculate interstitial fluid pressure based on dynamic contrast enhanced (DCE)-MRI data. This approach is based on Darcy's law (v=-K∇P) with v the velocity and ∇P the pressure gradient. The boundary condition at the outer edge of the tumor will be set to equal the convective outflow velocity values (v), as calculated during DCE-MRI. Hydraulic conductivity values (K) will be based on the tissue sample measurements. Other operational parameters such as the fluid properties (e.g. viscosity of interstitial fluid) will be based on literature values.

Quantitative laser ablation-ICP-MS will be used to analyze platinum penetration/distribution in peritoneal metastases that are left in situ during IP drug delivery but resected after completion of the procedure. The pixel intensities will be bilinearily interpolated and the Pt penetration depth set at 50% of the maximum intensity values.