1671 Neuroendocrine Tumours of the Anal Canal: A Catastrophic Culprit

Abstract

INTRODUCTION: Neuroendocrine (NE) tumors within the gastrointestinal (GI) tract are a rare type of GI malignancy with an estimated incidence of 2.5–5 per 100,000 people per year. 45% NE tumors arise in the small intestine, with the incidence decreasing throughout distal portions of the GI tract. Anal NE tumors represent 1% of all malignancies of the anal canal and are found incidentally on endoscopy. The rarity of this disease has led to a lack of sufficient data available to help guide therapy. Thus, the prognosis associated with NE tumors has remained poor throughout all stages of the disease. We present a case of anal NE carcinoma with disease recurrence after multiple lines of systemic treatment and salvage immunotherapy. CASE DESCRIPTION/METHODS: A 58-year-old female presented with complaints of constipation and mild rectal bleeding. She underwent a colonoscopy that revealed a 2 cm mass about 1 cm from the anal verge. Biopsy of the anal mass demonstrated high-grade NE carcinoma with small cell features. Staging computed tomography (CT) scan showed no metastases. Magnetic resonance imaging (MRI) of the brain was negative for metastasis. She underwent 4 cycles with cisplatin and etoposide as well as prophylactic cranial irradiation. Follow up CT scan showed an adequate response to initial therapy. However, three months later, repeat imaging showed new left retroperitoneal lymphadenopathy with biopsy revealing recurrent NE carcinoma. She again underwent therapy with cisplatin and etoposide as well as radiation therapy to the area of local recurrence. Repeat imaging showed absence of disease recurrence. The patient remained disease free for the next six months, until follow up imaging revealed a new left adrenal mass and retroperitoneal nodule. MRI of the brain showed brain metastasis. She began therapy with topotecan and cranial radiation, but due to a mixed response to treatment she was transitioned to temozolomide. Therapy continued but ended soon after progression of disease was noted. As a last attempt, she underwent immunotherapy with pembrolizumab but was transitioned to hospice care after the onset of rapid clinical progression of her disease. DISCUSSION: There remains a lack of treatment options beyond standard chemotherapy for this disease. Although she had an initial response to treatment, prognosis for anal NE carcinoma remains grim. This case illustrates the difficulty in management of this disease. Novel approaches in treatment are much needed.