Former NFL running back Ronnie Hillman is in hospice care as he battles a rare but aggressive form of kidney cancer.

According to a statement released by Hillman’s family to TMZ, the 31-year old was diagnosed with renal medullary carcinoma in August. He had been receiving treatment for the disease over the summer but it was unsuccessful. 

The rare and highly aggressive cancer almost exclusively affects the kidneys of young African Americans with sickle cell trait, according to the National Organization for Rare Disorders (NORD).

Most patients diagnosed with renal medullary carcinoma are young and by the time they are diagnosed, cancer will have spread to lymph nodes and other organs. The rare disease is twice as likely to occur in men as women, with the most common symptoms being blood in urine and pain over the kidney, usually on the right side. 

The exact cause of the disease is not fully known, according to NORD, but it can be treated with chemotherapy, surgery if feasible and occasionally radiation therapy. Still, the outlook is not promising for patients. 

According to a study published in The Ochsner Journal in 2014, the prognosis for renal medullary carcinoma is “extremely poor,” with likelihood of survival of less than a year in most cases. 

A study published in the Journal of the National Medical Association in 2017 argued that “early diagnosis and surgical intervention while the tumor is confined to the kidney” could offer the best chance for a patient’s long term survival. 

Hillman played in the NFL for five years and won a Super Bowl with the Denver Broncos in 2015.

Former Broncos teammate Orlando Franklin tweeted an update to his followers Tuesday, urging them to send well wishes for Hillman and his family. 

Additionally, former Broncos teammate Derek Wolfe told 104.3 The Fan on Tuesday that Hillman also had pneumonia and his prognosis was “not looking good.

News of Hillman’s condition comes as San Francisco 49ers running back Tevin Coleman leads Pfizer’s sickle cell awareness effort and promotes resources available for those living with the disease.

Sickle cell disease is one of the most common inherited blood disorders, affecting approximately 100,000 Americans, according to the Centers for Disease Control and Prevention, and is particularly common among Black and Hispanic Americans.

Update: Hillman died on Wednesday, December 21. He was 31.