Lateral lymph node recurrence and induction chemotherapy 57 CHAPTER 4 Introduction In the past decades, the treatment of rectal cancer has undergone major changes. Not only has total mesorectal excision (TME) become the gold standard1 but neoadjuvant treatment schemes have also been added, making it possible to induce a complete response and even spare the rectum.2 However, locally recurrent rectal cancer (LRRC) after neoadjuvant treatment with TME still occurs in 5–10 percent of patients,3,4 and the origin of this remains to be elucidated. In the East, mainly described in Japanese articles, it is hypothesized that LRRC may arise from positive lateral lymph nodes (LLNs) located in the obturator compartment and around the iliac vessels.5,6 After a primary LLN dissection (LLND) performed in low and advanced tumours, it has been reported that tumour cells can be identified in these LLNs in up to 20 percent of cases.7,8 We contemplated before that these lateral tumour deposits may result in (dorso)lateral recurrences (latLRs), and also observed that irradiating this compartment may prevent these fromdeveloping.9,10 However, with modern intensity-modulated radiotherapy (IMRT) techniques, a problem arises if this lateral compartment is not included in the IMRT volume, as this would increase latLR rates. Apart from the origin of latLRs, once these have occurred their treatment is surgically challenging. Evaluating the treatment of LRRC in our centre between 1994 and 200811 showed that latLRs resulted in only 28–56 percent R0 resections, with a poor 5-year survival between 19 and 37 percent. However, in earlier years, diagnostic imaging was of low quality andmany presacral recurrences might have beenmore laterally located, and anastomotic recurrences might have been designated as a latLR. In this study, we evaluated the treatment of latLRs in our centre in the last 10 years, with meticulous evaluation of high-quality magnetic resonance imaging (MRI), and combined this with endoscopic and pathologic data to distinguish latLRs from actual mid-presacral and anastomotic recurrences. Ourmainobjectivewas to analysewhether any changes can be made in the treatment of these aggressive recurrences in order to improve their poor prognosis in the future.