Retifanlimab after chemoradiation for anal cancer

Inclusion Criteria:

* Subject or legally authorized representative is willing and able to provide written informed consent.
* Age ≥ 18 on day of signing informed consent.
* Consent for use of archival tissue and blood draws for research purposes.
* Documentation of Disease

  o Patients must have pathologically confirmed anal squamous cell carcinoma.

  ° Pathology confirmation of the primary tumor at time of initial diagnosis is acceptable.
* Disease Specific Criteria

  * Patients must have MRD after completion of definitive-CRT defined as:

    * Detectable on the last day of or after completing definitive-CRT.
    * In patients with MRD within 6 months of CRT completion, patients with no overt clinical or radiographic progression will be eligible, the treatment response evolves for up to 6-months after completion of CRT. The ACT II trial demonstrated that 70% of patients with an incomplete response to CRT at 3-months achieved a clinical complete response by 6-months \[18\].
    * ctDNA will be assessed using Natera Signatera, a CLIA- validated tumor informed ctDNA assay, which MSK patients currently undergo baseline, on-treatment, and surveillance monitoring as standard of care.
    * As patients will not have measurable radiographic disease at time of enrollment, RECIST will not be used for study.
  * Patients must sign informed consent within 4 weeks of positive ctDNA result. The 4 weeks is considered from the date that the ctDNA resulted, and not the date it is drawn.
* Patients must have completed definitive CRT per institutional standards or as determined appropriate by the principal investigator.
* Resolution of all non-hematologic toxicities of prior therapy or surgical procedures to baseline or Grade 1 (except for hypothyroidism requiring medication, which must have resolved to Grade ≤2), alopecia, and other toxicities considered clinically nonsignificant and/or stable on supportive therapy as determined by the investigator.

  o Lymphopenia is a known side effect of CRT, which can take months to resolve \[4\], and is not an exclusion to eligibility.
* ECOG Performance Status of ≤ 2
* Required Organ Function

  * Adequate hematologic function defined as follows:

    * Absolute neutrophil count (ANC) ≥= 1,000 cells/mm3
    * Platelets ≥ 75,000 cells/mm3
    * Hemoglobin ≥ 9 g/dl
  * Adequate renal function defined as follows:

    * Creatinine clearance (CrCL) of ≥30 mL/min by the Cockcroft-Gault formula (Note: For agents for which renal excretion is not a major route of clearance and for which renal toxicity is not an issue, the threshold for creatinine clearance should be ≥30 mL/min.):

CrCl (mL/min) = \[ (140 - Age) × Weight (kg)\] / \[72 × Serum Creatinine (mg/dL)\], multiplied by 0.85 for females.

* Adequate hepatic function defined as follows:

  * Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN) (patients with known Gilbert's disease who have bilirubin level ≤ 3 x ULN may be enrolled)
  * AST and ALT ≤2.5 x institutional ULN
* Adequate cardiac function defined as follows:

  * Patients with known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, should have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification.
  * To be eligible for this trial, patients with known congestive heart failure should be class 2B or better (see Appendix II: New York Heart Association (NYHA) Functional Classification).

Exclusion Criteria:

* Presence of metastatic or recurrent disease.
* Active infection requiring parenteral antibiotic(s).
* Known active TB (Bacillus tuberculosis) infection.
* Known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.
* Active immune disease requiring systemic immunosuppression in excess of physiologic maintenance doses of corticosteroids (\>10mg of prednisone or equivalent).
* Interstitial lung disease or active noninfectious pneumonitis.
* Known active CNS metastases and/or carcinomatous meningitis.
* History of allogeneic bone marrow/stem, cell, or solid organ transplant.
* Pregnant or nursing or expecting to conceive or father children within the projected duration of the trial.

  o Participants of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) during study therapy and for 6 months following the completion of study therapy.
* Uncontrolled infection with human immunodeficiency virus (HIV). HIV-infected patients on effective anti-retroviral therapy with undetectable viral load and CD4+ count \>300/μL within 6 months are eligible.
* Known to be hepatitis B virus (HBV) surface antigen, or any other positive test for HBV indicating acute or chronic infection. Patients who are receiving or who have received anti-HBV therapy and have undetectable HBV DNA prior to study entry are eligible.
* Known active hepatitis C virus (HCV) as determined by positive serology and confirmed by polymerase chain reaction (PCR). Patients on or who have received antiretroviral therapy are eligible provided they are virus-free by PCR for at least 6 months prior to study entry.
* Receipt of a live vaccine within 28 days of planned start of study drug. Note: Examples of live vaccines include, but are not limited to, the following: measles, mumps, rubella, chicken pox/zoster, yellow fever, rabies, BCG, and typhoid vaccine. Seasonal influenza vaccines for injection are generally killed virus vaccines and are allowed; however, intranasal influenza vaccines (e.g., FluMist®) are live-attenuated vaccines and are not allowed.
* Prior therapy with an anti-PD-1, anti-PD-L1, or anti-CTLA-4 agent.
* History of allergic reaction to the study agent(s), compounds of similar chemical or biologic composition to the study agent (s) (or any of its excipients).