"The judge said he considered her medical condition but that she would receive care in the state prison," Eakin said after Tuesday's hearing in West Chester.
Eakin said Arnold could be eligible for parole after about a year. She said she would appeal and request that Arnold, 57, be released on bail during that process, "largely because of health concerns."
Eakin and a spokesman for the Attorney General's Office declined to comment on the length of the sentence.
The term topped what the guidelines recommend at the aggravated range, Eakin said. When the Court of Judicial Discipline investigated the case, Arnold was given a one-month suspension without pay.
She resigned when the Attorney General's Office filed charges.
By contrast, two former Philadelphia Traffic Court judges who admitted fixing tickets face six months or less under federal sentencing guidelines. Neither has been sentenced.
Arnold pleaded guilty in June to misdemeanor charges of obstructing justice and tampering with evidence.
Prosecutors say she told an employee at her court to "hold onto" a harassment citation filed against one of her adult sons for fighting with her other son.
When a state police officer inquired nearly two months later about why the citation had not been docketed, Arnold told him the court was backlogged, according to court documents.
About three weeks later, Arnold entered the citation into the court system herself, identifying her son as a black female when he is a white male, prosecutors say.
The discrepancies were discovered through a routine check, and the employee Arnold told to hold onto the citation was subpoenaed.
Prosecutors say Arnold later sought to have that employee fired.
In a sentencing memorandum, filed before Arnold's diagnosis became public, Senior Deputy Attorney General Susan Digiacomo said Arnold had "stained the fabric of the black robe" and asked that she be sentenced to prison.
The memo did not specify for how long.
Digiacomo declined to comment.
Joe Peters, spokesman for the Attorney General's Office, said Digiacomo noted the seriousness of Arnold's condition in court Tuesday and "acknowledged also that the court would likely take that into consideration."
Eakin said she was uncertain how Arnold's chemotherapy would be administered at the state prison.
"I am concerned for her health," she said. "I will say that."