Cisplatin and Fluorouracil Compared With Carboplatin and Paclitaxel in Treating Patients With Inoperable Locally Recurrent or Metastatic Anal Cancer

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 male…