Low Rectal Cancers: Evolution from Abdominoperineal Resection (APR) to Sphincter Saving Procedures (SSP)

Management of low rectal tumours is challenging for the surgeon as well as the patient as it involves subjecting the patient to a temporary, permanent or no stoma without compromising oncologic safety. Technically working in the confines of deep pelvis is a daunting task for achieving these results. The decision whether to leave a patient with a permanent stoma or save his sphincter is of utmost importance. Surgery for low rectal cancer has gradually evolved towards more sphincter saving procedures (SSP), mainly as a result of


Introduction
Management of low rectal tumours is challenging for the surgeon as well as the patient as it involves subjecting the patient to a temporary, permanent or no stoma without compromising oncologic safety. Technically working in the confines of deep pelvis is a daunting task for achieving these results. The decision whether to leave a patient with a permanent stoma or save his sphincter is of utmost importance. Surgery for low rectal cancer has gradually evolved towards more sphincter saving procedures With the advent of advanced gadgets and better understanding of tumour characteristics, more and more patients are subjected to SSP instead of APR.
The importance of distal resection margin is being overshadowed by circumferential resection margin. The main limit for sphincter preservation is not the longitudinal distance between the tumour and the anal sphincter, but the circumferential distance between the tumour and the skeletal muscles of the pelvic floor. This new concept transforms a 1 cm discussion to a 1mm [1].
Depending of the experience of the surgeon and specialization of the hospital, the rate of APR in rectal cancer surgery varies from 8% to 53% [5].

Objectives
Primary outcome measure of our study was to determine the various types of surgical treatment options in practice for distal rectal tumours & to compare the trend of APR and SSP in a highvolume centre.

Patients & Methods
This is a retrospective study of 3 years (2014-2016), carried out in the Colorectal Division of Department of General & Minimal Access Surgery SKIMS, Srinagar, India, which is a tertiary care institute & a high volume centre for colorectal surgery. Institute approval was sought to collect the data for publication purpose. Data was collected from Operation theatre record register, Medical Record Department, Pathology Department Archives Store and OPD follow up register. Documented carcinoma rectum < 10 cm from AV, patients who have underwent APR and LAR as recorded in case sheets & patients of various types of adenomas in low and middle rectum were included in the study. Patients undergoing Anterior resections, simultaneous surgical procedures, unresectable tumours at laparotomy & excision done for other benign pathologies were excluded from the study. We allocated patients to two groups: i.
Group A including patients who underwent APR ii. Group B including patients who underwent various types of SSP like LAR, TAE & TAMIS.
All the data was collected & tabulated in Excel work sheet. Statistical analysis of data was done using Microsoft Excel and SPSS software. Data of 167 patients was included in the study. More than 50 % of patients were above 50 years of age and almost 25% were younger than 40 years. Mean (±SD) age was 46.1(±7.89) years (Table 1).  The two groups were comparable in terms of age & gender. (Table 2).  (Table 3). In further sub group analysis, we compared the rate of APR vs. LAR in patients with growths within 6 cm & 7.5 cm and the rate of APR was 35.8 and 29.6% respectively ( Table 4).

Discussion
The standard approach of curative treatment in rectal cancer is surgery. Early stage cancers may be successfully treated with local excision. However, the vast majority of rectal cancers present at advanced stages and need more extensive surgery in the form of LAR or APR. Treatment of distal rectal tumours is challenging in providing a continent anal opening. Sphincter preservation with coloanal anastomosis in LAR has become an established option for low rectal cancers, however most patients with rectal cancer involving anal canal are routinely treated with APR.
Colorectal cancer generally tends to be more common in elderly, but the incidence among younger patients is increasing.
Both the incidence and mortality rates of CRC have been decreasing in the United States [6]. The observed decline in incidence is largely attributed to an increase in screening, specifically colonoscopy, which is recommended for all adults 50 years or older [7]. Conversely, the incidence of CRC in adults younger than 50 years, for whom CRC screening is not recommended, appears to be increasing, and these patients are more likely to present with advanced disease [8,9].
Several individual studies from Indian subcontinent consistently document a relatively high proportion of young age rectal cancer, with a mean age of around 40-45 yr [10][11][12]. In our study proportion of patients younger than 40 years was 26.4% and mean age of presentation was 50.27 years.
In a retrospective study of 153 patients of rectal cancer involving lower and middle rectum, Shapour Omidvari et al reported that out of 138 patients subjected to surgery 96 (70%) underwent LAR and 42 (30%) were subjected to APR [13]. Thus LAR to APR ratio was close to 1:3. In our study the overall incidence of APR as compared to other sphincter saving procedures was 17.36% which is close to 1:6. In 2007 data from Tata Memorial Hospital, Mumbai , one of the largest centres catering to colorectal cancer surgeries in India (2005 data) revealed the rate of APR being 45% as compared to 55% for LAR in low rectal cancers [14]. If we look at some of the largest clinical trials in rectal surgery, the aggregate percentage of patients subjected to APR is 39 % ( Table 5) [15].  [16].
Jonas Geohl from a cancer centre in Germany reported their data from1985 to 2007 (Table 6), wherein they performed surgeries on 725 low rectal cancers within 7.5cm from anal verge. SSP were performed in 379 (52.3%) patients including LAR in 275 and inter sphincteric resection in 104 patients. APR was done on 346 (47.7%) patients [17]. In our series 29.6% patients who had their tumours within 7.5% were subjected to APR. One of the reasons for a low rate of APR in our study is the volume of rectal surgeries we perform at our centre. On an average we perform more than 100 rectal cancer surgeries and along with colon almost 250-300 colorectal cancer surgeries every year. In this study we have included only low and middle rectal cancers over a period of 3 years and the number is 167 for 3 years. A high-volume centre has been defined as a centre where >24 (17-35) rectal cancer surgeries or >126 (85-167) colon surgeries are performed per year [18]. In a meta-analysis by Talya Salz et al. [19] they reported that many studies that measured hospital volume and surgery type, found a positive association between higher hospital volume and higher rate of sphincter-sparing procedures. The significant odds ratios were 0.44, 0.55, and 0.73. Significant differences between APR rates for high and low volume hospitals were reported as 26.4% vs. 29.8% for high and low volume, respectively, in one study, and 47% vs. 49% for high and low volume hospitals, respectively, in another study [20,21].

Conclusion
Low rectal cancer continues to be a challenge for the surgeon in maintaining balance between oncological clearance and sphincter preservation. Most of such patients can be offered continent sphincters as a result of improvement in knowledge and skills besides innovations in technology. The case volume of the centre plays a pivotal role in performing sphincter preserving operations. Ideally all low volume centres should preferably refer these cases to high volume centres for giving the maximum possible benefit to the patients in the form of sphincter preservation and better quality of life.