Beneficiary Access to Care Act of 2003 - Amends title XVIII (Medicare) of the Social Security Act with respect to the prospective payment system for hospital outpatient department services (OPD) to: (1) require the Secretary of Health and Human Services to treat as a separate group of covered OPD services any drug or biological that was treated as such a group as of December 31, 2002, and any drug or biological that has ceased to be eligible for transitional, pass-through payments by reason of the limited period of payment specified; and (2) add special rules for 2004 for the calculation of Medicare OPD fee schedule amounts, among other payment-related changes.Directs the Comptroller General to study and report to Congress on pharmacy services used to provide cancer drug therapies in hospital outpatient setting.