Gutierrez had a testicle removed two years ago, but the cancer returned last year, leaving him facing chemotherapy and a long road back to good health.
However, the Argentina international won his fight and returned to training, eventually pulling on the black and white shirt again for the first time against Manchester United on March 4.
The 31-year-old cemented himself in the affections of Magpies fans on Sunday when he sealed a vital 2-0 victory over West Ham with a goal in what appears likely to be his final game for the club.
“Since I had the treatment the only thing that I was thinking was recovery,” Gutierrez told Shields Gazette. “I was not really thinking about playing football, to be honest.
“The chemotherapy is a harsh treatment. Your body really feels it. You lose your hair with all the medication going into your body. It was hard. After that when I finished with the treatment, and I started outside the medication, my body started its recovery.
“It got nicer, because every day, my body was getting better. But, of course, during the chemo, it was hard watching your body in that type of state.
“In those moments, you don’t think about playing football again. Then the doctor says, ‘You are okay, you can start again’. I started to think, ‘Oh well, let’s see what happens’.
“I didn’t know how my body was going to react. Every day, I was improving. One day, I did a two-minute run, the next day four, and so on. Obviously, I got up to doing a marathon too!
“The good thing is my body reacted really well to the treatment and the exercise. The doctor told me the fact I was a footballer, and fit already, was a big help to recover and come back.
“You train all the days all year, so your body has memory of being well and fit. My body would feel it for a few days then get stronger.”