The 31-year-old, who last played in April, returned to South America when the illness was diagnosed and has had his left testicle removed.
Gutierrez spoke about his battle with cancer on Tuesday, saying it made other problems "insignificant".
"When I confirmed that I had cancer I went home crying. This was the most difficult game I had to play," he told Argentine TV.
"I detected a tumour in a testicle. I came here [Argentina] and I assumed the costs, despite having a contract with Newcastle.
"Money is not important. What is important is health and I had to start chemotherapy.
"I removed the left testicle. I returned to England and Newcastle told me to leave. It was hard to find my hair falling out. I did not want to cut it. I wanted to hold on.
"Fighting cancer makes the rest of the problems insignificant.
"I decided to tell my story because maybe it will help people who have cancer."
Gutierrez thanked fans for their support on Twitter late on Tuesday, tweeting that he was "always looking forward".
