This randomized phase II trial studies how well cisplatin and fluorouracil work compared with carboplatin and paclitaxel in treating patients with anal cancer that cannot be removed by surgery, has come back at or near the same place as the primary tumor, or spread to other places in the body. Drugs used in chemotherapy, such as cisplatin, fluorouracil, carboplatin and paclitaxel, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. It is not yet known whether cisplatin and fluorouracil are more effective than carboplatin and paclitaxel in treating anal cancer.

PRIMARY OBJECTIVES:

I. To evaluate best overall response rate (ORR).

SECONDARY OBJECTIVES:

I. Overall survival (OS). II. Progression free survival (PFS). III. Disease control rate (DCR) (stable disease [SD] or better) at 12 and 24 weeks.

IV. Best ORR of non-irradiated lesions. V. Anti-tumor activity and magnitude of response as captured by waterfall plot analyses.

VI. Toxicity. VII. Quality of life (QOL). VIII. Feasibility of conducting a multicenter international study on squamous cell carcinoma of the anus (SCCA) and recruit within a reasonable time frame.

TERTIARY OBJECTIVES:

I. Explorative biomarker analysis.

OUTLINE: Patients are randomized to 1 of 2 treatment arms.

ARM A: Patients receive cisplatin intravenously (IV) over 1-4 hours on day 1 and fluorouracil IV continuously over 24 hours on days 1-4. Treatment repeats every 21 days for 8 courses in the absence of disease progression or unacceptable toxicity. Patients with complications associated with the central venous access which prevent further infusion of fluorouracil and only after discussion with the Chief Investigator may receive capecitabine twice daily (BID) on days 1-4.

ARM B: Patients receive paclitaxel IV over 1 hour on days 1, 8, and 15 and carboplatin IV over 30-60 minutes on day 1. Treatment repeats every 28 days for 6 courses in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed up at 30 days and then every 12 weeks.

Inclusion Criteria:

• Inoperable, locally recurrent or metastatic disease (tumor resectability should be assessed by a local surgeon or multidisciplinary team)
• Histological or cytological confirmation of epidermoid anal carcinoma (includes squamous, basaloid and cloacogenic lesions) from the primary tumor or a newly diagnosed recurrent/metastatic lesion
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) =< 2
• Measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) criteria version 1.1
• Previous definitive chemo-radiation is permitted for early stage tumors (cisplatin-based chemotherapy [chemo]-radiation is permitted but only if tumor progression/relapse occurs after 6 months from treatment completion)
• Previous systemic chemotherapy is permitted if administered as induction treatment (=< 2 cycles) before definitive chemoradiotherapy for early stage disease and there is no evidence of tumor progression during or after treatment completion
• Human immunodeficiency virus positive (HIV+) patients will be considered eligible if they are on highly active anti-retroviral therapy (HAART) and have a cluster of differentiation (CD)4 count of >= 200/ul (HIV+ patients who are on HAART and have a CD4 count < 200/ul are eligible if the plasma viral load is below the level of detection according to the local assay)
• Absolute neutrophil count (ANC) >= 1.5 x 10^9/l
• Platelets >= 100 x 10^9/l
• Hemoglobin (Hb) >= 9 g/dl for males and >= 8 g/dl for females
• Creatinine clearance >= 50 ml/minute
• Serum bilirubin =< 1.5 x upper limit of normal (ULN)
• Alanine transaminase (ALT) or aspartate transaminase (AST) =< 3 x ULN (if liver metastases are present, serum transaminases =< 5 x ULN are permitted)
• Fertile men and women must agree to take adequate contraceptive precautions during, and for at least six months after therapy
• Life expectancy of at least 3 months

Exclusion Criteria:

• Tumors of adenocarcinoma, melanoma, small cell and basal cell histology are excluded
• Locally recurrent tumor which is amenable to curative resection (as deemed by a local surgeon or multidisciplinary team)
• Tumor relapse/progression within 6 months of completion of a cisplatin-based chemoradiotherapy regimen for the treatment of early stage tumors
• Previous administration of > 2 cycles of systemic chemotherapy as induction treatment before definitive chemoradiotherapy for early stage disease
• Tumor progression during or immediately after completion of =< 2 cycles of systemic chemotherapy as induction treatment before definitive chemoradiotherapy for early stage disease
• Previous use of systemic chemotherapy or other investigational drugs for the treatment of inoperable locally recurrent or metastatic tumors (previous use of radiotherapy in this setting is not an exclusion criterion if: 1) non-irradiated target tumor lesions are present at randomization for the purpose of tumor response assessment or 2) in the absence of non-irradiated target tumor lesions, progression of the irradiated tumor lesions according to the RECIST criteria version 1.1 is documented)
• Current or recent (within 30 days of first study dosing) treatment with another investigational drug or participation in another investigational study
• Documented or symptomatic brain metastases and/or central nervous system metastases or leptomeningeal disease
• Major surgery performed < 28 days from treatment start
• Palliative radiotherapy completed =< 7 days from treatment start
• Clinically significant (i.e. active) cardiac disease (e.g. symptomatic coronary artery disease, uncontrolled cardiac arrhythmia, or myocardial infarction within the last 6 months); any history of clinically significant cardiac failure
• History of interstitial lung disease (e.g. pneumonitis or pulmonary fibrosis) or evidence of interstitial lung disease on baseline chest computed tomography (CT) scan
• HIV+ patients who are not on HAART or have a CD4 count of < 200/ul in the presence of detectable plasma viral load according to the local assay
• Known history of active hepatitis B or hepatitis C infection
• Serious active infection requiring intravenous (i.v.) antibiotics at enrollment
• Other malignancy within the last 5 years, except for adequately treated carcinoma in situ of the cervix or squamous carcinoma of the skin, or adequately controlled limited basal cell skin cancer
• Other clinically significant disease or co-morbidity that may adversely affect the safe delivery of treatment within this trial
• Known hypersensitivity to any of the study drugs or excipients
• Known peripheral neuropathy > grade 1 (absence of deep tendon reflexes as the sole neurological abnormality does not render the patient ineligible)
• Pre-existing hearing impairment
• Patients planning for a live vaccine
• Pregnant or lactating females