Bernard Madoff should not be released early from his 150-year prison sentence, even though he has terminal kidney failure, federal prosecutors said Wednesday. The 81-year-old Madoff, who orchestrated the largest Ponzi scheme in history, asked for compassionate release from prison last month, saying he has less than 18 months to live. But the US Attorney’s office for the southern district of New York said Madoff’s crime was “unprecedented in scope and magnitude” and is “sufficient reason” to deny Madoff’s request. “Since his sentencing, Madoff has demonstrated a wholesale lack of understanding of the seriousness of his crimes and a lack of compassion for his victims, underscoring that he is undeserving of compassionate release,” the US Attorney’s office wrote. Madoff was arrested in December 2008 on allegations that the prestigious asset management firm he ran in Manhattan was, in fact, a pyramid-type scheme that swindled billions of dollars from thousands of people. He pleaded guilty to 11 felony charges related to money laundering, perjury and falsifying financial documents. He began his prison term in July 2009. More than 500 victims wrote to the court about Madoff’s early release request, with an “overwhelming” amount of them opposed. The court said the letters show “how deeply Madoff’s crimes continue to affect his victims, many of whom, as one put it in a letter to the court, are ‘serv[ing] a kind of life sentence of [their] own.’” In one letter, a victim blamed her husband’s death on the stress of losing money through Madoff’s scheme. The woman acknowledged that Madoff is suffering with his condition, but she noted there are “many of his victims who are suffering and who will continue to suffer.” The US Attorney’s office also said it “clearly reckoned” with Madoff’s medical condition and the fact that the sentence means he will die in prison. But because of his “continuing refusal to accept responsibility and show remorse,” they stood by their decision. They acknowledged Madoff has kidney failure, and a doctor says he has about 18 months to live. But prosecutors also noted Madoff’s condition has improved recently. Madoff has been serving his sentence at a federal prison in Butner, North Carolina. He initially submitted a compassionate release request in September to the Bureau of Prisons, which issued a denial in December. In a letter detailing the denial, the warden did not dispute Madoff’s condition or his life expectancy, but noted that Madoff had refused dialysis. He re-started dialysis in November 2019, prosecutors said, and Madoff is able to care for himself. – CNN’s Kara Scannell and Clare Duffy contributed to this report.