# A Case of Peritoneal Carcinomatosis After Hyperprogression in Human Papillomavirus-Positive (HPV+) Oropharyngeal Squamous Cell Carcinoma

## TL;DR

A patient with HPV-positive oropharyngeal cancer experienced rapid tumor growth (hyperprogression) after immunotherapy and developed rare peritoneal metastasis.

## Contribution

This is the first reported case of peritoneal carcinomatosis following hyperprogression in HPV+ oropharyngeal squamous cell carcinoma.

## Key findings

- HPV+ HNSCC can lead to hyperprogression after immunotherapy.
- Peritoneal carcinomatosis is a rare metastasis site in HNSCC.
- This case highlights the need for further study on hyperprogression and unusual metastasis patterns in HPV+ tumors.

## Abstract

Immunotherapy has been shown to provide clinical benefit in selected patients with head and neck squamous cell carcinoma (HNSCC), regardless of human papillomavirus (HPV) infection, and including recurrent/metastatic (R/M) platinum refractory tumors. Hyperprogression is an uncommon negative outcome of treatment with immunotherapy. We present the case of a patient with HPV+ HNSCC who presented hyperprogression after immunotherapy and a rare metastasis location with peritoneal carcinomatosis and subcutaneous nodules. HPV+ HNSCC is related to distant recurrence after a longer interval of time and more diverse metastasis sites compared with HPV- disease. However, the literature on peritoneal metastasis in HNSCC remains limited, with few documented cases. To the best of our knowledge, this is the first case reporting peritoneal carcinomatosis after hyperprogression in HNSCC.