The star, 55, who spoke about her family in Monday's The Real Full Monty, lost her sister Bernie, 52, to the disease in 2013, and Anne, 69, and Linda, 61, found out they had secondary terminal breast cancer and liver cancer respectively, earlier in the year.
WATCH: Coleen makes emotional comments about sister Annie and Linda
"Cancer took my sister Bernie in 2013, I didn't think life could get any worse than that then bam 2020 comes alone," Coleen said on the show.
"My first thought with Anne and Linda was, 'I can't bear losing any more sisters, I can't bear it!'
"It's been horrendous actually, you try and be strong for them, as they are being strong, there are just times when you feel so weak with it and angry, it's unfair," she added.
Speaking about her fears for herself, she continued: "Once I got over shock and trauma, then you go through the panic of 'Am I next?' it's obviously in my family."
The sisters spoke exclusively to HELLO! in September
Coleen's emotional appearance comes just a day after her sister Linda revealed that her liver cancer has spread.
The star completed chemotherapy in September and spoke exclusively to HELLO! at the time about getting treatment during lockdown and how she struggled with losing her hair, but on Sunday, she told The Mirror: "It's scary, I'm not going to lie. I try to be upbeat and positive but I had a really bad day when I got back [home].
"I told my sisters I was fine but when I got inside my house, I cried. I needed to have that cry because I'm scared to death of dying."