What is the standard treatment regimen for patients with stage I, II, or III anal squamous cell carcinoma?

The standard treatment regimen for patients with stage I, II, or III anal squamous cell carcinoma is radiation therapy with concurrent chemotherapy. This approach is widely accepted due to several factors inherent to the disease's biology and the effectiveness of the treatment modality.

Anal squamous cell carcinoma typically has a significant association with human papillomavirus (HPV) infection, and the tumor's sensitivity to radiation makes it amenable to treatment with this modality. The use of chemotherapy alongside radiation enhances the overall efficacy of the treatment. The concurrent chemotherapy typically involves agents such as fluorouracil and mitomycin C, which can sensitize the cancer cells to radiation, thus improving local control of the tumor and potentially reducing the risk of metastasis.

Additionally, this combined modality approach is particularly important for preserving anal function, as surgery in many cases may lead to complications such as incontinence or the need for a permanent colostomy. Therefore, for patients who are considered at least stage I through III, radiation therapy with concurrent chemotherapy represents a robust standard that aims to maximize treatment effectiveness while preserving quality of life.

In contrast, options like surgery followed by observation or treatments such as immunotherapy and hormonal therapy are not standard for this specific type and stage of cancer, making radi