Staging and prognosis

Invasive anal cancer is curable in a great number of patients, particularly when it is diagnosed early and tumors are small. Anal cancers are most commonly treated with a combination of chemotherapy and radiation, which is discussed in further detail in the treatment section but can be expected to cause the tumors to completely regress in 80 to 90% of patients. Once a diagnosis of cancer is made from any site, one of the first steps done prior to determining how the cancer should be treated is to determine whether it is localized or has spread or metastasized [1] either to nearby lymph nodes or to distant organs, a process known as staging a cancer. The American Joint Committee on Cancer has created a formal staging system for most cancers that is based on 3 criteria: T or tumor size and an assessment of invasion of nearby organs, N or whether or not the cancer has spread to local lymph nodes, and M, which denotes the absence or presence of metastases to distant organs. The stage of a cancer is based on determining the T, N, and M for each tumor, which is then used to guide treatment and also provide an idea of the probability that the cancer can be cured or how effective the treatment is likely to be.