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Local excision of rectal carcinoma

Local excision has been around a long time. Before the modern era of surgery it was the only means of treating rectal cancer. After the introduction of anaesthesia and aseptic surgery, it was considered an option for cure in the early 1900s. The criteria used at that time were very similar to those amplified by Morson in the 1970s [1] by the addition of histopathological factors including grade, completeness of excision and lymphovascular invasion. Driven by the aim to avoid a permanent colostomy and also the mortality of major surgery, the proportion of patients with rectal cancer treated by local excision has increased in the last 10 years or so. Imaging by endoanal ultrasound has enabled the identification of early T stage (T1, T2) lesions although there are limitations to the accuracy of this assessment with overstaging reported in 29% of T1 and 13% of T2 tumours [2] and sensitivity and specificity for T1 tumours of 86% and 94% [3]. Magnetic resonance imaging is less sensitive than ultrasound for these early tumours. Surgical technical advances including transanal endoscopic microsurgery (TEM) have expanded the scope of local excision to the entire rectum and more proximally. The application of adjuvant treatment in the form of postoperative chemoradiotherapy has also been applied to the strategy of local excision often for tumours of T2 and occasionally T3 as well as T1 stage [4–6]. There are now several reports of large numbers of patients undergoing local excision when used in three clinicopathological circumstances: first for patients with disseminated disease whose primary tumour is small, secondly in elderly patients or those with comorbidity for whom a major resection is likely to be too traumatic with a high risk of morbidity and mortality and thirdly as primary treatment for cure. In the last of these, the strategy of local excision has tended to divide into two schools of thought. The first largely developed in Europe has reduced the indications to T1 tumours while the second, advocated by some units in the United States has expanded them combing local excision with adjuvant chemoradiotherapy. The argument for reducing the indications has been based upon the histopathological examination of major resection specimens in which T stage has been related to the prevalence of regional lymph node metastasis. Hermanek [7] has demonstrated a prevalence of regional lymphadenopathy of 5% for T1 tumours rising to nearly 20% for T2. Within the group of T1 tumours, there is evidence that depth of penetration into the submucosa and the morphology whether polypoid or sessile influence the incidence of regional lymph node metastases. Analysis by Haggitt et al. [8] and subsequently Kikuchi et al. [9] has shown prevalence rates for regional lymphadenopathy ranging from 5% to 25% depending on the depth of invasion of the submucosa and the morphology, a sessile having a greater risk than a polypoid tumour. This has been mirrored by correlation of morphology whether exophytic (polypoid) or sessile (flat adenocarcinoma or ulcerated carcinoma) with cancer-specific 5-year survival rates of 100% and 71%. Exophytic morphology is more likely to be associated with an earlier T stage with 86%of exophytic and only 26% of nonexophytic carcinomas being of stage T1 [10]. These data support the view that local excision should only be applied to T1 tumours invading the superficial submucosa. Where local spread goes beyond into the deep submucosa, the risk of lymph node metastases may rise to over 20%. If this rate is regarded as unacceptable, then the indication for local excision should be confined to the T1 tumour with only superficial penetration of the submucosa. The data from series combining local excision of T stages beyond T1 with adjuvant treatment are difficult to analyse. It is not possible to establish a prospective randomized trial of local excision and major resection for obvious reasons. Attempts to compare the cancer-specific outcome of series reporting the results of local excision and radical resection of T1 and T2 tumours do suggest, however, that local recurrence is less following the latter. Thus in three large series, local recurrence occurred in 13% after local excision for T1 carcinomas compared with 2% after radical resection and corresponding 5-year survival rates were 77% and 87% [11–13]. Advocates of local excision have maintained that subsequent salvage radical surgery in the event of a local recurrence results in ultimate survival no different from the expected rate were a major resection to have been carried out as primary treatment . Salvage surgery after recurrence following local excision cannot, however, always be either possible or curative. Low recurrence rates of < 5% after TEM have been reported suggesting that case selection can result in a satisfactory cancer specific outcome [14–17]. One of the difficulties encountered in interpreting the results of local excision is that the patients reported have been accrued over many years, during which new pathological data have become available to refine the indications. Any group of patients undergoing local recurrence is therefore not homogeneous histopathologically. This may explain some of the cancer-specific failures.