Evolving standards in preoperative staging and treatment of rectal cancer.

Colorectal cancer has become the commonest cancer in Hong Kong since 2011 and rectal cancer constitutes about one third of all colorectal cancers.1 Rectal cancer has a much higher local recurrence rate of about 10% than colon cancer.2 Hence, stern efforts must be made to safeguard patients from recurrence during the management of rectal cancer. In current practice, good oncological outcome with low local recurrence rate for rectal cancer treatment relies on careful exercise of total mesorectal excision (TME) technique which is the standard for midand low-rectal cancer resection3 and perioperative radiotherapy with/without chemotherapy. In the Dutch rectal cancer trial, combination of TME and preoperative short-course radiotherapy (5 Gy for 5 days) was associated with a significantly lower recurrence rate of 2.4% at 2 years versus 8.2% with TME only (P<0.001).4 A combination of longcourse radiotherapy (usually 50.4 Gy over 6 weeks) and fluorouracil offers additional benefit of tumour downstaging to improve sphincter preservation rate or even complete tumour remission in about 15% to 20% of patients.5 Radiotherapy, given after operation, can also reduce local recurrence rate. However, a randomised trial showed that, compared with postoperative chemoradiation, preoperative chemoradiation was associated with significantly better local control and less toxicity for locally advanced rectal cancer, which is defined as T3 or T4 or lymph node–positive rectal cancer.6 Hence, most colorectal centres adopt the policy of offering neoadjuvant (preoperative) chemoradiation to locally advanced rectal cancer. As the preoperative local staging of rectal cancer affects the management plan, the accuracy of staging is very important. Preoperative local staging usually relies on endorectal ultrasound or magnetic resonance imaging (MRI). Recently, MRI has emerged as the preferred modality for local staging of rectal cancer by colorectal surgeons. Apart from having high reproducibility and accuracy in assessing T stage and regional lymph node status, high-resolution MRI can predict circumferential resection margin (CRM) of the rectal tumour. In pathology terms, a positive CRM is defined as presence of tumour within 1 mm of radial surgical margin and it is associated with high chance of local Hong Kong Med J 2014;20:364–5 DOI: 10.12809/hkmj144370 Jensen TC Poon*, FCSHK, FHKAM (Surgery)