eP354 - Sustained Complete Clinical Response After Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Adenocarcinoma: A Case Report

Purpose/Background: Pre-operative treatment with concurrent radiotherapy and chemotherapy for rectal adenocarcinoma has been shown to significantly reduce tumor burden, local recurrence, toxicity effects, and improve overall survival. Pathologic complete response (pCR) is a desired outcome after neoadjuvant chemoradiotherapy (nCRT), which may only be determined after surgery and pathologic analysis of the specimen. The concept of a “watch-and-wait” approach has gained interest – that is, the deferment of surgery and conduct of close surveillance if patients exhibit a complete clinical response (cCR). This report highlights a patient who underwent solely nCRT, yet presented with sustained cCR.Methods/Interventions: Our patient is a 68 year-old male, who in 2017 presented with a two-year history of intermittent constipation, crampy abdominal pain, and weight loss. The patient underwent colonoscopy and biopsy, revealing a well-differentiated adenocarcinoma at 5 cm from the anal verge. Pre-treatment imaging with chest and abdominal CT, and pelvic MRI, showed a locally-advanced node-positive disease without distant metastasis (Stage IIIB (cT3N1M0)). Due to symptoms of gut obstruction, the patient underwent laparoscopic transverse loop colostomy with an unremarkable postoperative course. The patient then received neoadjuvant treatment in the form of long course chemoradiotherapy (LCCRT) that consisted of 25 sessions of radiotherapy at 1.8 Gy per fraction (total 45 Gy) with concurrent oral capecitabine at 825 mg/m2 twice a day, with no significant side effects. The patient was scheduled for elective low anterior resection (LAR) after LCCRT. However, he was lost to follow-up. In the interim, the patient did not report any recurrence of pre-treatment symptoms.Results/Outcomes: After five years from completion of LCCRT, the patient consulted inquiring on the possibility of stoma reversal. No lesion was appreciated on digital rectal examination (DRE). Colonoscopy with biopsy of the fibrotic area was negative for malignancy. Repeat imaging with CT and MRI showed interval resolution of the mass with development of fibrosis at the tumor site, no enlarged pelvic lymph nodes, and no evidence of metastatic disease. Due to the uncommon nature of the case, a multidisciplinary team (MDT) agreed to a transanal excision of the rectal fibrosis for definite histopathology. The patient, however, did not accede to the plan and opted for continued surveillance.Conclusion/

Discussion: The presently sustained cCR status of our patient has been the result of an inadvertent “watch-and-wait” strategy, which itself was brought about due to logistical and financial constraints. Had it not been for the initial diversion surgery, the patient may have likely not followed-up at all. Yet this omission was, in retrospect, not truly detrimental.

The continued development of protocols for the treatment of locally-advanced rectal cancer have increasingly improved outcomes, at times obviating the need for surgical management, thus sparing the patient of the associated risks and morbidities. However, current literature is not conclusive of the benefits of the “watch-and-wait” approach, nor is it definitive in recommending it as the standard of care in patients who demonstrate cCR. The decision to proceed with a “watch-and-wait” approach should be tailored to the individual patient, and part of a shared decision-making process between an MDT and the patient.Post-LCCRT Pelvic MRI and Colonoscopy(From L-R) (First three images) Representative cuts of the Pelvic MRI on follow-up 5 years post-LCCRT, showing non-enhancing soft tissue thickening and fibrosis in the left ischiorectal fossa (green arrows). (Rightmost image) Corresponding site of fibrosis seen on colonoscopy; biopsy was negative for malignancy