Durable complete response to tislelizumab plus cetuximab in a 94-year-old patient with advanced lower lip squamous cell carcinoma: A case report and literature review.

[BACKGROUND] Lip squamous cell carcinoma (SCC) is a rare subtype of head and neck squamous cell carcinoma (HNSCC), accounting for approximately 1 % of all oral malignancies. Unlike other oral SCCs (e.g., tongue or buccal SCC), lip SCC has distinct epidemiological features: it shows a stronger association with chronic sun exposure (especially ultraviolet radiation) and a lower correlation with smoking/alcohol consumption. It is more common in elderly males, and advanced cases with lymph node metastasis are associated with poor prognosis. The treatment of advanced lip SCC in elderly patients is uniquely challenging due to its anatomical location (functional and aesthetic importance), which makes aggressive therapies like surgery more likely to cause functional impairment (e.g., difficulty in mouth opening or speech) and poor tolerance to such therapies due to comorbidities [1-3].

[CASE SUMMARY] A 94-year-old female patient presented with a progressively enlarging mass on the right lower lip, which was diagnosed as poorly differentiated squamous cell carcinoma with neck lymph node metastasis (cT4N2M0). Due to her advanced age and late-stage disease, she was not eligible for surgery, radiotherapy, or chemotherapy. She received combination therapy with tislelizumab (200 mg intravenously every 3 weeks) and cetuximab (400 mg/m intravenously every 2 weeks) starting from November 27, 2024. Significant improvement of the lip mass was observed after treatment, and complete response was achieved on January 8, 2025, after two cycles of treatment. Consolidation therapy was continued for six months, with no recurrence or metastasis during follow-up. As of July 31, 2025 (6 months after initial treatment), the patient remains in complete response with regular follow-up. Immunohistochemical analysis showed PD-L1 positivity with a combined positive score (CPS) of 80, which may predict a favorable response to immunotherapy.

[CONCLUSION] This case demonstrates that the combination of tislelizumab and cetuximab can achieve remarkable efficacy in elderly patients with advanced lip SCC, even without surgery, radiotherapy, or chemotherapy. PD-L1 high expression (CPS = 80) may serve as a valuable predictive biomarker for immunotherapy response in such cases. Six months follow-up confirms the durability of the response, supporting the potential of this regimen in extreme elderly populations.