In addition to the above. all states offer Pre-Existing Cinditions Insurance Plan, PCIP, from the Patient Protection and Afforale Care Act, enacted that covers people who have not had insurance for 6 months or more, and have cancer or other pre-existing condition, but you mention having insurance, so I don't know if it applies.
Based on age, Medcare coverage, over age 65
See about applying for Medicaid. Each state differs, some also have HIPP, Health Insurance Premium Payment Program.
There are cost sharing assistance Charities, and patient assistance programs
Chronic disease fund
Health well foundation
National organize for rare disorders
Patient access network
Patient Advocatd Foundation
Patient Srtviced Inc
RxAssist Patient Assistance Program center
Partnership for prescription assistance
Needy,Ed's
Together Rx Access