Predicting tumour response

Abstract

Response prediction is an important emerging concept in oncologic imaging, with tailored, individualized treatment regimens increasingly becoming the standard of care. This review aims to define tumour response and illustrate the ways in which imaging techniques can demonstrate tumour biological characteristics that provide information on the likely benefit to be received by treatment. Two imaging approaches are described: identification of therapeutic targets and depiction of the treatment-resistant phenotype. The former approach is exemplified by the use of radionuclide imaging to confirm target expression before radionuclide therapy but with angiogenesis imaging and imaging correlates for genetic response predictors also demonstrating potential utility. Techniques to assess the treatment-resistant phenotype include demonstration of hypoperfusion with dynamic contrast-enhanced computed tomography and magnetic resonance imaging (MRI), depiction of necrosis with diffusion-weighted MRI, imaging of hypoxia and tumour adaption to hypoxia, and 99m Tc-MIBI imaging of P-glycoprotein mediated drug resistance. To date, introduction of these techniques into clinical practice has often been constrained by inadequate cross-validation of predictive criteria and lack of verification against appropriate response end points such as survival. With further refinement, imaging predictors of response could play an important role in oncology, contributing to individualization of therapy based on the specific tumour phenotype. This ability to predict tumour response will have implications for improving efficacy of treatment, cost-effectiveness and omission of futile therapy.

Bench to bedside molecular functional imaging in translational cancer medicine: to image or to imagine?

“…212,214,215 Other radiopharmaceuticals recognised by MDR1 Pgp that have been used to probe Pgp functions in nude mouse xenograft models expressing multidrug-resistant KB8-5-11 tumour cells are 67/68 Ga-3-ethoxy-ENBDMPI, 67 Ga for SPECT, and 68 Ga PET imaging. 214,215 Other MDR proteins that are being studied include MRP1 (gene symbol ABCC1), MRP2 (gene symbol ABCC2), and breast cancer resistance protein (BCRP, gene symbol ABCG2). 211,212,214 99m Tc-sestamibi is a lipophilic cationic radiotracer commonly used to study MDR proteins in cancer and has been used in vivo studies for breast, head and neck, hepatobilliary, gastric, and lung cancers.…”

P-Glycoprotein Expression in Heart, and its Potential Physiological Relevance

“…Several techniques to assess the treatment-resistant phenotype in cancer, include demonstration of hypoperfusion with dynamic contrast-enhanced computed tomography and magnetic resonance imaging (MRI), depiction of necrosis with diffusion-weighted MRI, imaging of hypoxia and tumor adaption to hypoxia, and 99m Tc-SESTAMIBI imaging of P-glycoprotein mediated drug resistance [7].…”

Incorporating prognostic imaging biomarkers into clinical practice

“…Prognostic biomarkers should be distinguished from predictive imaging biomarkers and imaging markers of response. Predictive imaging biomarkers are imaging characteristics that provide information on the likely benefit from treatment and are discussed in detail elsewhere in this journal [ 1 ] . Imaging biomarkers of response represent surrogate measures for the beneficial outcomes that are intended from treatment.…”