Inclusion Criteria:  Stage I-III anal cancer or stage I-IVA cervical cancer that is p16+ based on immunohistochemistry. Age ≥ 18 years Planned to undergo radiation therapy as definitive treatment, with or without concurrent systemic therapy  Exclusion Criteria:  Anal carcinoma not associated with HPV-16, 18, 31, 33, or 35 will be removed from the Planned to undergo radiation therapy as an adjuvant or post-operative therapy