eP356 - Complete Pathologic Response After Total Neoadjuvant Therapy for Rectal Cancer in the Philippines: Initial Report on Possible Implications on LMICs

Purpose/Background: Total neoadjuvant therapy (TNT) for rectal cancer has recently been developed to improve pathologic complete response (pCR), survival, chemotherapy completion rates, and avoid resection, among other parameters. Strategies vary extensively as to chemotherapy and radiotherapy (RT) protocols. Previous reports on neoadjuvant chemoRT in the Philippines indicate disparate challenges including planning, organizational, logistical, and financial toxicity issues. This case study on TNT, the first documentation from the Philippines to the best of our knowledge, aims to highlight and provide insights of this modality particularly in resource-limited low to middle income countries (LMICs).Methods/Interventions: Our patient is a 70-year-old Filipino male with a 3-month duration of on and off hematochezia. Initial colonoscopy revealed a nodular, friable rectal mass 5 cm from the anal verge, read as fragments of adenoma and necrotic debris. He then presented at a tertiary city hospital for which further work-up with MRI, chest CT and repeat biopsy showed a Stage IIIB (cT3N2aM0) well-differentiated adenocarcinoma of the rectum with involvement of the mesorectal fascia (MRF). He then underwent TNT consisting of chemoRT with 28 fractions of pelvic RT (5040 cGy) and concurrent oral capecitabine (825 mg/m2 PO twice daily on each day RT is given) over 6 weeks, followed by 12 weeks of CapeOx chemotherapy (Oxaliplatin 130 mg/m2 IV day 1 and Capecitabine 1000 mg/m2 PO twice daily for 14 days every 3 weeks), which he tolerated well. Follow-up MRI of the abdomen showed a significant reduction in the size of the T3 rectal mass with mucinous change and fibrosis, and resolution of the mesorectal/perirectal lymph nodes. Laparoscopy-assisted low anterior resection, total mesorectal excision and loop ileostomy were performed 6 weeks after the last cycle of chemotherapy.Results/Outcomes: Histopathologic examination revealed no residual malignancy with mucinous lakes without tumor in muscularis of resected colorectum. Circumferential, distal and proximal resection margins and lymph nodes were negative for tumor. Patient developed an anastomotic leak within 2 weeks post-op, for which repair and drainage of abscess were done with no further complications. Latest follow-up 16 months post-surgery showed no evidence of recurrence as the patient contemplates ileostomy reversal.Conclusion/

Discussion: pCR through TNT for rectal cancer in a resource-limited setting can be achieved. Adaptive strategies such as the use of oral and generic chemotherapy (rather than IV 5-FU and the globally-short IV leucovorin, avoiding in-hospital care), minimally invasive surgery, shorter RT duration, protocol standardization, locally available resources and trans-disciplinary management expertise, can be maximized towards better outcomes. Further documentation of pCR post-TNT should be pursued to increase the national database towards the universal goal of the “watch and wait” nonoperative approach.Pre-TNT and Post-TNT MRI Images(Blue Arrow) Pre-TNT MRI Diffusion-weighted image (DWI) shows presence of enlarged peri-rectal lymphadenopathy with resolution on corresponding Post-TNT image.

(Red Arrow) Post-TNT MRI T2 image shows rectal mass with scattered T2-hyperintense foci representing mucinous degeneration and a markedly T2-hypointense periphery due to fibrosis as compared to corresponding Pre-TNT image.