LAUSR

The most important prognostic factor in locally recurrent rectal cancer is completeness of surgical resection with clear margins (R0 resection). Ascertaining a complete resection of pelvic sidewall recurrences is more difficult to achieve when compared to other compartments due to the involvement of local structures such as the internal iliac vessels and nerve roots/sciatic nerve. This study was reviewed, deemed low risk and approved by the local institutional ethics committee. A case of a re-recurrent rectal cancer in a 73-year-old female is presented with a previous stage III primary rectal cancer resected in 2014 followed by adjuvant therapy and a left pelvic sidewall recurrence diagnosed with elevated carcinoembryonic antigen (CEA) levels on surveillance in 2018. In the referring institution, the patient underwent an attempted resection of the recurrent mass with positive margins on histology followed by post-operative radiotherapy to bilateral pelvic lymph nodes (50 Gy in 25 fractions). Her CEA levels continued to increase and a positron emission tomography (PET) scan confirmed residual disease activity medial to surgical clips involving the pelvic surface of obturator internus with a 16 mm intense focus in the anterior abdominal wall, representing a tumour implant. After multidisciplinary team discussion, the patient underwent long-course chemoradiotherapy (39.6 Gy in 22 fractions) with subsequent re-imaging highlighting a partial metabolic response to the abdominal wound tumour implant and pelvic sidewall recurrence on PET (Fig. 1) and magnetic resonance imaging (Fig. 2). Ten weeks later, the patient underwent bilateral ureteric stent insertion, laparotomy, full-thickness resection of the infraumbilical abdominal wall mass followed by left internal iliac vessel resection, complete obturator internus excision and intraoperative radiotherapy (IORT). Medial mobilization of the descending colon, left ureter, bladder and low colorectal anastomosis was performed to generate space and gain access into the left pelvic sidewall. The left internal iliac artery and vein were ligated and dissection continued caudally to include the mass (Fig. 3a). In order to ensure an R0 resection, lateral dissection was continued to resect the left obturator muscle by detaching it from the posterior aspect of the acetabulum and ischium together with the piriformis muscle (Fig. 3b). An intraoperative decision was made to resect the lumbosacral bundle and S1/2 nerve roots to provide a clear radial margin (Fig. 3c, the patient had complained of sciatic nerve pain preoperatively). IORT (10 Gy) was then delivered to the lateral bony margin. Apart from a prolonged postoperative ileus, recovery was unremarkable. The patient developed a left foot drop and reduced hip adductor and abductor power. This was managed with orthotics using ankle-foot orthosis and physiotherapy input. Two weeks post-operatively, the patient was independently mobilizing with a gutter frame up to a distance of 80 m, and is able to perform transfers with one assist. Currently the patient is mobilizing freely with the use of a crutch and is expected to be able to mobilize without any assistance over the next coming months. The histopathology of the left pelvic sidewall mass reported recurrent adenocarcinoma infiltrating fibrofatty tissue and extensive intraneural invasion of a 5 mm calibre nerve with clear resection margins throughout. One lymph node revealed a metastatic deposit. The abdominal lesion was excised showing adenocarcinoma with clear of margins.