AJCC staging for anal canal cancers is based on the size of the tumor and local invasion of adjacent organs or structures.A tumor that is 2 cm or smaller is designated T1, larger than 2 cm but not more than 5 cm is T2, and larger than 5 cm is T3. Any size tumor that invades a local structure is designated T4. Staging of disease includes CT of the chest, abdomen, and pelvis and pelvic MRI. Positron emission tomography scanning should be considered for larger (T2 or greater) tumors or any node-positive disease. HIV testing and checking a CD4 count should also be considered if indicated. Historically, treatment consisted of surgery alone or radiation therapy alone. Epithelial or subepithelial tumors were locally excised, and more advanced lesions underwent APR. The introduction of multimodality therapy combining chemotherapy andradiation therapy promised to preserve continence, to avoid colostomy, and to offer similar or improved survival. Nigro was the first to promote radiation therapy with chemotherapy as definitive treatment for squamous cell cancers of the anal canal. The current protocol includes infusional 5-FU with mitomycin C and external beam radiation to the pelvis with a minimum dose of 45Gy. The inguinal nodes, pelvis, anus, and perineum should be included in the radiation fields. Patients with T2 lesions and residual disease after 45 Gy, T3 or T4 tumors, or node-positive disease are usually treated with an additional 9 to 14 Gy for a total dose of 54 to 59 Gy. In patients treated with APR for persistent or locally recurrent disease, 5-year actuarial survival is repoed at 57%.46 Despite high success rates with definitive chemoradiotherapy, 15% to 30% of patients will have recurrence or fail to respondcompletely.47 Patients with persistent disease up to 6 months after treatment generally require APR. Those who have local recurrence are also recommended for APR. In the setting of isolated inguinal node recurrence, groin dissection is generally required with consideration for radiation therapy to the inguinal node basins if no prior radiotherapy was given. Up to 50% of patients treated with salvage APR can expect a 5-year cure. This is compared with approximately 27% of patients treated with salvage radiation and concurrent cisplatin-based chemotherapy who can expect cure. In those patients presenting with anal squamous cell carcinoma in the setting of HIV infection, disease severity (CD4 count and use of antiretroviral therapy) has a significant impact on success of standard chemoradiation. The current consensus is that standard protocols for chemoradiotherapy should be attempted, regardless of HIV status, and that medical management of the patient's HIV infection be optimized. The 2-year survival rates for HIV-positive patients have been repoed to be the same as for HIV-negative patients, 77% and 75%, respectively Ref: Sabiston 20th edition Pg no : 1415