The study showed that a tumor circumferential resection margin of less than 2 mm were associated with significantly poorer patient survival. This finding was consistent with a great deal of other literature (6, 8) and what is accepted in our current clinical practice. The distal resection margin was, not shown to be an independent predictor of survival. Again, consistent with other literature (12, 14, 20). Thus, a distal magin of less than 1 cm may be acceptable, if the tumour was completely removed. Unecesserily large distal margins may mean unessecary sacrifice of sphincters in low lying tumours.
Most studies (including the largest of its kind to date (21)), report that a LAR overall produces a higher survival rate than an APR (paradoxically the disease-free survival rates were suggested to be very similar). Though findings were commonly confounded by the fact, that the tumours of the patients were relatively high from the anal verge, and that the subgroups had different PCRT rates (22, 23). Most studies on the subject of local failure indicate greater rates with APR. This is most likely because of CRM involvement, which is directly correlated with a more advanced disease stage and larger tumours. These tumours also present lower and are more locally advanced (24), and have a worse response to neoadjuvant therapy (4). Many surgeons still prefer APR in cases of very low tumors with sphincter complex invasion or impaired preoperative state. As such, LAR could be considered an acceptable alternative – especially in patients with a good response to neoadjuvant treatment and adequate margin from the anal canal.
Because of the aforementioned, the continuation of the intestinal passage is, in clinical practice, desired in nearly every case (25). Despite the benefits offered by the LAR, low anterior resection syndrome (LARS) is a major problem for long term QOL. It usually develops shortly after surgery, then decreases in a few months (the stable state being reached after 2 years). It is more common in patients which have preexisting anorectal dysfunction (especially in women who have given birth – previous trauma to the site of resection (4). Another possible complication is anastomotic leak (may be as high as 10%). Current data suggests, that the functional outcome in LAR is superior to APR when no long-term postoperative complications arise – though some studies with objective measurements dispute this (4, 26, 27). In addition, studies which had a longer follow up suggested, that patients experience a response shift over time, being able to better cope with their condition, the more time passes after surgery. This suggest that planning operations to maximize life expectancy, is linked with an overall higher long term QOL. Thus, smaller DRM, could help the surgeon operate difficult cases, with proper oncological principles, resulting in more favorable long-term survival and functional prognosis. Though caution should still be exercised and so surgeons should not attempt a preferred surgery at any price, but should instead seek to individualize treatment for every case – as well as evaluate for complications both pre and intraoperatively (25). This knowledge could potentially be used to counsel the patient, when conditions for operation, are less than ideal (even when an APR is potentially required). Though, it may be prudent, to view APR as more than a last line treatment in older patients, patients with low life expectancy or major anorectal dysfunction (25).
In our study the APR group (DRM > 1 cm) had a smaller death rate, than the LAR group. This is usually not the case, as studies which report a better prognosis with APR are fewer in number, than those who reporting contrary (23). Despite this the reason for this is most likely neoadjuvant chemotherapy, or PCRT – which may have been used more liberally in cases of patients which are targets for APR, in our sample. The group of patients operated on by the LAR method with a DRM > 1 cm appears to stand out in the number of deaths. Further analysis showed, however, that it was not an independent variable - it can be assumed that the reason for this is similar (5, 28). The difference between mortality in the groups with smaller and larger CRM was also much larger for the LAR method (26%) than for the APR (6%). This may, simply be a consequence of neoadjuvant chemotherapy of PCRT (not excluded in this study). An additional factor to consider here, would be the natural coning of the lower bowel which increases chances of CRM involvement in low LAR operations. Apart from this natural coning, there is the issue of coning into the tumor during surgery, due to the higher anastomotic leak rate after complete mesorectal excision (5).
The limitations of the study were small sample size, with resulting small patient subgroups (which varied significantly in size). Despite being designed to minimize differences between its subgroups, they could not be entirely excluded (some may have remained significant). A potential source of bias could be the unequal numbers of APR and LAR operations (the doctors in our institution prefer performing LAR-s) If the patients were controlled for PCRT, the cohort would be so small, as to be beyond any analytical relevance. The data on the effect of PCRT and neoadjuvant therapy on outcomes was inconclusive until recently and was not in the authours scope of view in the time of study design. The FOxTROT trial was only published in 2019 and reported a response in the tumour, might make the resection easier, and reduce the risk of incomplete surgical resection. It also reported histological regression in some positive pCRMs. The trial also established, that no increase in perioperative morbidity was seen. This may offer hope for functional outcomes of lower tumours, which are otherwise operable only with APR (29). Some studies have, however reported an increase postoperative anorectal disfunction, when combined with PCRT (30). Another confounding factor, could be the surgical donuts themselves, as a negative stapler donut does not preclude involvement of the distal margin, as it contains only a part of a staple or suture line. This is also true for circumferential margins (there is always a risk of residual malignant cells in the rectal stump) (31).
The results have value in the context of sphincter-sparing resections (DRM-s smaller than 1 cm may be neccesary in many cases), which may offer significantly better oncological and functional prognosis in select groups of patients. The question of LAR vs. APR in the context of QOL, remains inconclusive, as research results (especially measured with objective questionaires, are scarce and contradictions are common. It can, however be reasoned that a personalised treatment (the precise criteria for this, are still unavailable and may be of interest for future research), less invasive treatment, which does not compromise oncological principles may be optimal for both functional and oncological outcome, especially when the surgeons evaluate for complications during entire treatment.