Role of magnetic resonance imaging in loco-regional evaluation of cancer rectum, pre and post neoadjuvant therapy
The high rate of local recurrence is considered the major concern and challenge regarding the surgical treatment of cancer rectum. The target of use of pre-operative neoadjuvant therapy is reducing tumour size and improving its resectability in order to reduce local recurrence risk and improve survival rates.
Plans for management and treatment of locally advanced rectal cancer showed clear changes after use of neoadjuvant therapy. This in turn necessitates accurate evaluation of the tumour parameters before and after use of combined chemotherapy and radiation therapy (CRT).
Aim of study is to assess the initial stage of cancer rectum then its response to neoadjuvant therapy using MRI, prior to operative interference. This is followed by post-operative histo-pathological data correlation.
Methods: This study was conducted on 50 patients. All patients were examined by high-resolution T2- weighted images. Turbo-spin-echo sequences taken in sagittal plane, axial plane perpendicular to tumor axis and coronal plane parallel to tumor axis or anal canal. All are according to tumor height. Diffusion weighted images (DWI) performed in all cases.
Results: Following neoadjuvant therapy, down-staging was detected in this study in more than 90% of patients regarding the T2 signal and apparent diffusion coefficient (ADC) value of the tumour, also status of depth of involvement of meso-rectal fascia (MRF), circumferential resection margin (CRM), extramural vascular invasion (EMVI) and nodal involvement.
Conclusion: Pre-operative MRI in cancer rectum is irreplaceable to assess initial staging and postneoadjuvant therapy response thus improving surgical results.
Keywords: MRI, CRT, DWI, ADC, MRF, CRM, EMVI