A rare case report of colon metastasis from primary oropharyngeal squamous cell carcinoma treated with a combination of surgery, radiotherapy and immunotargeted therapy.

Background: Oropharyngeal squamous cell carcinoma (OPSCC) is a type of head and neck squamous cell carcinoma (HNSCC). The incidence of distant metastasis from HNSCC is approximately 10-15%. The most frequent organs of distant metastasis include the bone, liver, and lungs, and the occurrence of metastasis to the colon is very rare. To date, the treatment recommendation for these patients, especially local treatment, is unclear. This case reports a real case of a rare metastatic location from OPSCC, thus expanding our knowledge of OPSCC. At the same time, it suggests that local treatment has potential value in patients with metastatic HNSCC, especially for those with concomitant local symptoms. Case Description: The patient, a 72-year-old male, underwent radical radiotherapy with concurrent chemotherapy for previously diagnosed with cT4N2M0 stage III HPV16 (+) (American Joint Committee on Cancer, 8th) OPSCC. The patient experienced diarrhea during the post-treatment monitoring period and subsequently underwent a re-examination. The positron emission tomography-computed tomography (PET-CT) findings confirmed colonic metastasis and axillary lymph node enlargement. After the surgical removal of the colon tumor, OPSCC metastasis was confirmed. PET-CT findings of other organs and primary lesions did not suggest recurrence or metastasis. This case provides a new reference for the pattern of disease progression in patients with HNSCC who have received radical concurrent radiochemotherapy. This patient achieved long-term, high-quality survival as a result of local surgery, radiotherapy, systemic immune checkpoint inhibitor therapy, and anti-vascular targeted therapy. The patient's progression-free survival (PFS) has reached 28 months, and apart from bone marrow suppression induced by chemotherapy, no adverse reactions have occurred during the combination of immunotherapy and targeted therapy. Conclusions: This case not only provides an example of a rare metastatic location of OPSCC, thus expanding our knowledge of OPSCC. At the same time, it suggests that local treatment has potential value in patients with metastatic HNSCC, especially for those with concomitant local symptoms.