The compassionate release program is found in 18 U.S. Code § 3582 - Imposition of a sentence of imprisonment. It is for federal cases, not state cases. There are 18 factors to consider. The standard is "extraordinary and compelling reasons warrant such a reduction." Generally, it means imminent death/terminal illness.
On a listserv a Bucks County criminal lawyer belongs to, someone commented on the program, "The federal "compassionate release" statute is 18 USC 3582(c)(1)(A). On its face, the standards are far more flexible than the "suspension of sentence due to terminal illness" statute in PA. Even when limited to the categories of terminal illness and elderly-and-ill, as provided in the BOP's program statement (agency regulation) on the subject, which I believe to be unlawfully narrow, the standards on their face seem encouraging. On the other hand, release must be recommended by the BOP and the motion to modify the sentence must itself be filed by the U.S. Attorney's office on behalf of the BOP, and not by the prisoner or counsel for the prisoner (unlike a PA motion). In practice, however, it is basically a black hole. Endless delay at the Central Office level is the name of the game, arbitrary refusal to file for prisoners who appear to be fully qualified (and have been recommended for release by their warden) is common, and many die while awaiting action."
Some folks, however, did comment on the same email that they have had success with the Compassionate Release program.
A few years ago the Bureau of Prisons published "Compassionate Release; Procedures for Implementation of 18 U.S.C. 3582 (c)(1)(A) & 4205(g)" as well as an update in 2015.