On December 29, the actor shared a handwritten letter on his official fan page and stated:
"Hello, this is Kim Woo Bin.
I wondered how to start my first sentence for a long time after holding up the pen. Although I'm greeting you guys through a letter, my heart is pounding as if I'm standing in front of you guys. First of all... were you guys really surprised?
I wanted to let everyone know sooner, but I've been so occupied with receiving treatment and taking care of my body that a total of 7 months have passed. Honestly, I also got afraid each time my name appeared on the real-time search ranking so it took me longer, but I wanted to deliver [my message] before this year passed.
First, I think I need to talk about my current condition which is what you are curious about the most. Back in May, I was diagnosed with nasopharyngeal cancer, an illness I've never heard of. With understandings from film directors, sunbae and hoobae actors, and staff members, I adjusted all schedules immediately and started treatment.
Thanks to all of your support and prayers, I have successfully completed 3 chemotherapy sessions in addition to undergoing radiation therapy a total of 35 times. I was able to withstand it all while reading everybody's encouraging messages on the fan cafe. Thank you from the bottom of my heart.
Currently, I am gradually recovering after safely receiving treatment and going for follow-up testing. I've also been taking strolls from time to time and eating meals on a regular basis, and I feel that I'm gradually getting better. However, I think it will take some more time for me to greet you all. Every time I left a message on the fan cafe, I always said to take good care of yourselves as health is first and foremost, but I'm embarrassed that I'm here showing a weak side of me. Through this opportunity, I will take extra care of my health and work hard to only deliver good news.
I pray only the good will happen in the new year for everyone and their families who are going through a difficult time right now. I hope 2018 is only filled with happiness, and I hope all is healthy.
One day, I'll come back healthily as if nothing happened. I always appreciate you guys. Thank you. I love you."