A literature review of the association between diffusion-weighted MRI derived apparent diffusion coefficient and tumour aggressiveness in pelvic cancer

•Low ADC values are associated with more aggressive tumours.•ADC values have a potential to differentiate pelvic cancers at high risk of poor response and recurrence.•ADC values allow evaluation of biological behaviour of pelvic cancers.

Diffusion-weighted magnetic resonance imaging (DW-MRI) is used extensively to improve tumour detection and localization because it offers excellent soft tissue contrast between malignant and non-malignant tissues. It also provides a quantitative biomarker; the apparent diffusion coefficient (ADC) can be derived from DW-MRI sequences using multiple diffusion weightings. ADC reflects the tumour microenvironment, e.g. cell membrane integrity and cellularity and has potential for reporting on tumour aggressiveness. This review focuses on the use of the DW-MRI derived imaging biomarker ADC to reflect tumour aggressiveness and its potential impact in managing pelvic cancer patients. The clinical studies which evaluate the role of ADC in pelvic tumours (prostate, bladder, rectal, ovary, cervix and uterus) are summarized and the evidence linking ADC values with tumour aggressiveness is evaluated.