Cancer Drug Coverage Parity Act of 2013 - Amends the Employee Retirement Income Security Act of 1974 (ERISA), the Public Health Service Act, and the Internal Revenue Code to require a group or individual health plan providing benefits with respect to anticancer medications administered by a health care provider to provide no less favorable coverage for prescribed, patient-administered anticancer medications used to kill, slow, or prevent the growth of cancerous cells and that have been approved by the Food and Drug Administration (FDA).

Applies such requirement to medication that is prescribed based on a finding by the treating physician that the medication is: (1) medically necessary for the purpose of killing, slowing, or preventing the growth of cancerous cells in accordance with nationally accepted standards of medical practice; and (2) clinically appropriate in terms of type, frequency, extent site, and duration.

Permits such coverage to be subject to the same cost-sharing applicable to anticancer medications administered by a health care provider under the plan.

Prohibits a health plan from imposing an increase in out-of-pocket costs, reclassifying benefits with respect to anticancer medications, or applying more restrictive limitations on prescribed orally- or intravenously-administered or injected anticancer medications.

Requires a plan to provide notice to each participant and beneficiary regarding the coverage required under this Act.

Prohibits a health plan from taking specified actions to avoid the requirements of this Act.

Requires the Medicare Payment Advisory Commission to assess how closing the Medicare part D donut hole affects Medicare coverage for orally-administered anticancer medications, with a particular focus on cost and accessibility.