Introduction Since total mesorectal excision TME was first

Introduction Since total mesorectal excision (TME) was first described by Heald and Ryall in 1982, rectal cancer has become a potentially curable condition. Traditional abdominoperineal resection has gradually been replaced with TME and coloanal anastomosis for resectable low rectal cancer. In addition, improved overall survival and decreased local recurrence rates have been achieved. Furthermore, for locally advanced (cT3/4, cN1/2) low rectal cancer (lower tumor margin<6 cm above the anal verge), sphincter preservation is a major concern in cancer treatment. Randomized controlled trials have shown that neoadjuvant chemoradiation therapy (CRT) leads to a decrease in tumor size and increases the likelihood of tumor resectability and sphincter preservation with low local recurrence rates. Therefore, neoadjuvant CRT followed by TME is the standard treatment guideline used worldwide for patients with low rectal cancer.
Clinical staging evaluation Computed tomography, which determines the clinical staging of low rectal cancer, is widely used worldwide because of easy accrual, short execution time, and relatively low costs. Rectal tumor shrinkage after neoadjuvant CRT correlates positively with clinical and pathologic changes. However, until now, magnetic resonance imaging (MRI) for selecting node-positive patients, and transrectal ultrasound (TRUS) for determining tumor invasion depth have been the gold standards for clinical staging. Similar to other types of ultrasound, TRUS is operator dependent. However, with an experienced operator, TRUS can be as effective as MRI in detecting perirectal lymphadenopathy. Nevertheless, using MRI to determine whether the circumferential resection margin (CRM) is compromised during TME is another major benefit of using this hcv protease inhibitors approach to determine whether patients require neoadjuvant radiotherapy (RT). Finally, before we depend totally on modern technology, a digital examination should always be performed, which can be as accurate as TRUS or MRI in tumor staging when performed by an experienced surgeon.
Evolutionary process of chemotherapy, radiotherapy, and chemoradiation therapy Prior to the widespread acceptance of TME, randomized controlled trials had confirmed that using adjuvant chemotherapy (CT) and RT could significantly reduce local recurrence rates and improve overall survival rates for rectal cancer patients. In addition, general consensus indicates that neoadjuvant RT has the effects of sterilization of the mesorectal lymphatic channels, tumor bulk reduction in improving resectability and increasing sphincter preservation, exclusion of the small bowel from the radiation field, improved response in untreated tumors, and superior function of nonirradiated neorectum. TME and RT have merged gradually, such that both CT and RT, which are used prior to surgery, enable superior local control and higher overall survival, setting the foundation for subsequent randomized controlled trials in validating their effects. After TME became the dominant surgical procedure for low rectal cancer, more randomized controlled trials were executed, revealing a phenomenon that neoadjuvant RT could reduce local recurrence rates, even after TME surgery. The superior local control ability of neoadjuvant RT was confirmed by both the Dutch TME trial after 12 years of follow-up and the German Rectal Cancer Study Group trial after 11 years of follow-up.
Short- versus long-course radiotherapy The choice of long- or short-course RT has long been an active debate; each choice has its own proponents. However, in improving the tumor downsizing effect, long-course RT is superior to short-course RT, although short-course RT with a longer waiting period can still achieve the same effect, as reported by the Stockholm III trial. Regarding local control, the effectiveness of short-course RT is at least comparable with that of long-course RT. Table 1 summarizes crucial randomized controlled trials about neoadjuvant and adjuvant RT, CT, and CRT with long-term follow-up results.