Preoperative staging of rectal cancer

Abstract

Detailed preoperative staging using high resolution magnetic resonance imaging (MRI) enables the selection of patients that require preoperative therapy for tumour regression. This information can be used to instigate neoadjuvant therapy in those patients with poor prognostic features prior to disturbing the tumour bed and potentially disseminating disease. The design of trials incorporating MR assessment of prognostic factors prior to therapy has been found to be of value in assessing treatment modalities and outcomes that are targeted to these preoperative prognostic subgroups and in providing a quantifiable assessment of the efficacy of particular chemoradiation treatment protocols by comparing pre-treatment MR staging with post therapy histology assessment. At present, we are focused on achieving clear surgical margins of excision (CRM) to avoid local recurrence. We recommend that all patients with rectal cancer should undergo pre-operative MRI staging. Of these, about half will have good prognosis features (T1-T3b, N0, EMVI negative, CRM clear) and may safely undergo primary total mesorectal excision. Of the remainder, those with threatened or involved margins will certainly benefit from pre-operative chemoradiotherapy with the aim of downstaging to permit safe surgical excision. In the future, our ability to recognise features predicting distant failure, such as extramural vascular invasion (EMVI) may be used to stratify patients for neo-adjuvant systemic chemotherapy in an effort to prevent distant relapse. The optimal pre-operative treatment regimes for these patients (radiotherapy alone, systemic chemotherapy alone or combination chemo-radiotherapy) is the subject of current and future trials.

Neoadjuvant Treatment Strategies for Locally Advanced Rectal Cancer

“…Pelvic MRI scanning has been established as the investigation of choice for local staging of rectal cancer prior to surgery [13,14,15] [16,17]. This is commonly defined as disease encroaching to within 1mm of mesorectal fascia (MRF) or lower rectal cancers involving the levator-sphincter complex.…”

“…For patients with such features, with optimum surgery and selective use of pre-operative radiotherapy, DM relapse is Gollins approximately 6-fold greater than LR (approximately 30% vs. 5%) [6,7,28] and is now the main cause of death. MRI scanning is the pre-treatment investigation which can most reliably identify such features [13,14,15].…”

Inhibitory effects of oxaliplatin in experimental radiation treatment of colorectal carcinoma: does oxaliplatin improve 5-fluorouracil-dependent radiosensitivity?

“…Tumor depth, namely T stage, is important as T1 and T2 tumors have excellent long time survival, whereas T3 tumors, which make up 80% of rectal tumors seen in clinical practice (55) and T4 have more variable prognoses, thus, the newest edition of the TNM classification suggests an optional expansion of classifying extramural spread (9,55,56).…”

Prediction of response to preoperative chemoradiotherapy in patients with locally advanced rectal cancer

“…With the advancement of MRI techniques, recent studies are no longer only reliant on staging rectal cancer patients, but also on prognostic and predictive functions (8,9). Diffusion-weighted MRI (DW-MRI) provides information about microscopic structures through the detection of water proton mobility in biologic tissues (9,11).…”