Inguinal Node Sparing Radiotherapy For Patients With Early Stage Anal Cancer

Inclusion Criteria: 1. Participants capable of giving informed consent. 2. Patients must be 18 years of age or older. 3. Patient should have histologically proven primary squamous cell carcinoma. 4. Patients must have early AC, Stage T1-3 N0 M0. 5. No inguinal nodal involvement confirmed by PET imaging and SLNB. 6. No history of prior malignancy other than non-melanoma skin cancer or other malignancy with disease free survival ≥ 5 years. 7. Performance status ECOG 0-2 / Zubrod performance status ≥70. 8. Patient should be eligible for concomitant chemotherapy (e.g. adequate hepatic, renal and bone marrow function). 9. Women of child bearing potential (WOCBP) must have a negative serum (or urine) pregnancy test at the time of screening. WOCBP is defined as any female who has experienced menarche and who has not undergone surgical sterilization (hysterectomy or bilateral oophorectomy or bilateral salpingectomy) and is not postmenopausal. Menopause is defined as 12 months of amenorrhea in a woman over age 45 years in the absence of other biological or physiological causes. In addition, females under the age of 55 years must have a serum follicle stimulating hormone, (FSH) level \> 40 mIU/mL to confirm menopause. 10. Patients of childbearing / reproductive potential should use highly effective birth control methods, as defined by the investigator, during the study treatment period. A highly effective method of birth control is defined as those that result in low failure rate (i.e. less than 1% per year) when used consistently and correctly (Note: abstinence is acceptable if this is established and preferred contraception for the patient and is accepted as a local standard). 11. Females must not breastfeed during study treatment. 12. Male patients should agree to not donate sperm during study treatment. 13. Absence of any condition hampering compliance with study protocols and follow-up schedule; those conditions should be reviewed with the patient prior to trial registration. Exclusion Criteria: 1. T1N0 patients going for primary surgery 2. Prior radiation therapy to the pelvis. 3. Pregnancy or lactation. 4. Prior surgical treatment for anal cancer other than biopsy. 5. Prior surgical or chemotherapy treatment for anal cancer. 6. Evidence of distant metastases. 7. Comorbid medical conditions precluding radical treatment at the discretion of Oncologist. 8. Histology other than squamous cell carcinoma or variants.