An approach to the management of recurrent metastatic squamous cell carcinoma of the anus: A case report

Abstract

Introduction: Anal squamous cell carcinoma (ASCC) is an uncommon gastrointestinal cancer that is increasingly curable when diagnosed in early stages. Distant metastases are relatively uncommon. New technologies have been introduced for the early detection of disease recurrence across all solid tumors, but their role in ASCC has not been well described. We present a case of isolated metachronous metastasis to the lung from primary ASCC, without primary recurrence and the application of circulating tumor DNA (ctDNA) technology in management. Case Report: The patient is a 63-year-old female who presented with altered bowel habits, rectal bleeding and was found to have a 3×2 cm mass fixed to the anal sphincter on colonoscopy. Biopsy showed moderately differentiated invasive squamous cell carcinoma. Imaging revealed inguinal lymphadenopathy but was negative for distant metastases. She underwent definitive chemoradiotherapy without complications. Post-treatment surveillance scans were negative for residual disease or distant metastasis. Two years later, positron emission tomography (PET)/computed tomography (CT) scans revealed a 0.5 cm sub-pleural nodule which when repeated three months later grew to 0.7 cm. The nodule was then surgically resected. Histology was positive for metastatic squamous cell carcinoma, similar to the primary tumor. Given the dearth of data related to treatment in the setting of resected isolated metastatic disease we pursued ctDNA testing which was negative. Given this finding along with the clinical presentation, time to metastasis (two years) and absence of other evidence of recurrence we opted to monitor expectantly rather than administer systemic chemotherapy. Conclusion: Anal squamous cell carcinoma with metachronous distant metastasis is an unusual phenomenon. Treatment with chemotherapy in completely resected metastatic disease is controversial. Use of ctDNA technology may have a role in aiding in this complex decision making.