Molecular imaging of hypoxia with radiolabelled agents

Tissue hypoxia results from an inadequate supply of oxygen (O2) that compromises biological functions. Structural and functional abnormalities of the tumour vasculature together with altered diffusion conditions inside the tumour seem to be the main causes of tumour hypoxia. Evidence from experimental and clinical studies points to a role for tumour hypoxia in tumour propagation, resistance to therapy and malignant progression. This has led to the development of assays for the detection of hypoxia in patients in order to predict outcome and identify patients with a worse prognosis and/or patients that would benefit from appropriate treatments. A variety of invasive and non-invasive approaches have been developed to measure tumour oxygenation including oxygen-sensitive electrodes and hypoxia marker techniques using various labels that can be detected by different methods such as positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), autoradiography and immunohistochemistry. This review aims to give a detailed overview of non-invasive molecular imaging modalities with radiolabelled PET and SPECT tracers that are available to measure tumour hypoxia

Role of preoperative MR imaging in the evaluation of patients with persistent or recurrent gynaecological malignancies before pelvic exenteration

PURPOSE: To determine the diagnostic performance of MRI in assessing local tumour extent and evaluate associations between MRI features and survival in patients undergoing MRI before pelvic exenteration for persistent or recurrent gynaecological cancers. METHODS AND MATERIALS: The study included 50 patients with persistent or recurrent gynaecological malignancies who underwent pelvic exenteration between January 1999 and December 2011 and had MRI at most 90 days before surgery. Two radiologists independently assessed invasion of adjacent organs (on a 5-point scale). Diagnostic accuracy, inter-reader agreement, and associations between organ invasion on MRI and patient survival were evaluated. RESULTS: Areas under receiver operating characteristic curves (AUCs) for invasion of the bladder, rectum and pelvic sidewall were 0.96, 0.90 and 0.98 for reader 1 and 0.95, 0.88 and 0.90 for reader 2. Corresponding sensitivities/specificities were 87.0 %/92.6 %, 81.3 %/97.0 % and 87.5 %/97.2 % for reader 1, and 87.0 %/100.0 %, 75.0 %/97.0 % and 75.0 %/94.4 % for reader 2. Inter-reader agreement was excellent for organ invasion (κ = 0.81-0.85). Pelvic sidewall invasion on MRI was associated with overall and recurrence-free survival (P = 0.01-0.04 for the two readers). CONCLUSION: Preoperative MRI is accurate in predicting organ invasion. It may guide surgical planning and serve as a predictive biomarker in patients undergoing pelvic exenteration for gynaecological malignancies. KEY POINTS: • MRI can accurately assess bladder and rectal wall invasion before major surgery. • MRI identifies patients requiring extended pelvic exenteration by detecting sidewall invasion. • Inter-reader agreement for detecting organ invasion and tumor size is excellent. • Pelvic sidewall invasion on MRI is associated with shorter overall and recurrence-free survival