Organ preservation in rectal cancer

Between 25 and 30 per cent of resectable rectal cancers are early disease (tumour node metastasis T1–2 N0 M0 or stage I) and this could increase with the introduction of screening. This article focuses on the management of fit patients with early low and mid rectal cancer, and explores the possibility and safety of organ (rectum and anal sphincter) preservation. The surgical standard of total mesorectal excision (TME) is integral to the multimodal management of rectal cancer, and preoperative short-course radiotherapy further improves local control. The results of the Dutch1 and the UK Medical Research Council CR072 trials, with 5-year local recurrence rates of 2 per cent or less in patients with early rectal cancer, have become the benchmark. A small clinical (c) T1 rectal cancer with low risk of nodal involvement (3 cm or less in diameter, differentiation G1–2, no lymphovascular invasion) is considered appropriate for full-thickness local excision (LE), either by transanal excision or transanal endoscopic microsurgery. LE is appealing to both patients and surgeons because of reduced morbidity, negligible risk of urogenital dysfunction and the prospect of organ preservation. In 2003, 43·7 per cent of T1 rectal cancers registered in the US National Cancer Database were treated by LE. Outcome analysis confirmed previous reports that LE for pT1 tumours carries an increased risk of local failure compared with standard resection (12·7 versus 6·9 per cent)3. The risk of lymph node metastasis in pathological (p) T1 tumours increases with the depth of submucosal invasion (sm): 3 per cent for T1 sm1, 8 per cent for T1 sm2 and 23 per cent for T1 sm34. LE, therefore, should be limited to ultrasound (u) T1 sm1 N0, pG1–2 T1 sm1 disease without lymphovascular invasion. Endorectal ultrasonography (ER US) performed by an experienced examiner can distinguish massive (corresponding to sm2–3) from superficial (corresponding to sm1) submucosal invasion with a sensitivity of 98 per cent and specificity of 88 per cent5. Accurate nodal staging in patients with deeply invading uT1 tumours (sm2–3) is essential, but remains a major problem; better diagnostic modalities to determine node positivity are needed. Although the accuracy of ERUS and magnetic resonance imaging with the use of ultrasmall iron-based particles may improve, detection of micrometastatic disease will always be a problem. Endoscopic posterior mesorectal excision (EPME), developed by the St Gallen group and reported in this issue of BJS6, is presented as an adjunct to LE for T1 N0 cancer. This partial lymphadenectomy allows node sampling while sparing the rectum. Two of 25 patients with ‘lowrisk’ T1 tumours (three or fewer of the following risk factors: tumour budding, poorly demarcated invasive front, moderately or poorly differentiated cancer cells in the invasive front, extension of the tumour to the middle or deep submucosal layer, cancer cells in lymphatics) and three of ten with ‘high-risk’ T1 tumours (at least four of these factors) were node positive. Patients with positive nodes received chemoradiotherapy (CRT). It is interesting to consider how many patients would be upstaged to cN+ if more accurate imaging were available (N0 was defined as less than 1 cm in diameter at ERUS). The main problem with LE and EPME is that the classical diagnostic and therapeutic aspects of cancer management are not adhered to. LE exposes the excision bed to tumour contamination, whereas the mesorectum is only partially removed at EPME. Lymphatic spread may well deviate from the usual routes referred to by Tarantino and colleagues6. Finally, it is questionable whether optimal salvage surgery can be performed after LE, EPME and CRT. Thus, EPME may have to be restricted to patients with pT1 sm1 disease in whom the probability of having to perform a completion TME is very low. There is more than one therapeutic option for patients with uT1 sm2–3 rectal cancer, who have an 8–23 per cent risk of node positivity. One option, TME preceded by short-course radiotherapy, is complicated by surgery-related mortality and morbidity, including anorectal and urogenital dysfunction, as well as radiotherapy-related acute and late toxicity. Another option, LE and EPME, has significantly less mortality, morbidity and functional sequelae; it limits the use of CRT to patients with pN+ disease. However, LE without EPME, followed by CRT in unfavourable T1 carcinoma, is undoubtedly inferior to the local control obtained