Now this is a very interesting thread, and I can relate to many answers, both pro and against telling co-workers.
If I may share my two cents:
I am a telecom software engineer. I learnt about my condition the same day that I arranged a routine business trip, which I obviously had to cancel. My boss and two of my closest colleagues learnt what's happening from day one. I literally went to my office to tell them, in between two hospitals, while searching for an haematologist.
In the course of the next 3 months, I only missed work for 2 days: the day of the diagnosis, and the day of my biopsy. The rest of my teammates initially learnt that I'm dealing with a blood issue, a "bad gene", a potentially fatal illness (if you don't discover it), which is treatable with a pill. No one heard the word leukemia, and no one freaked out. They basically knew exactly what was going on, without the scary name.
In the course of these 3 months, one by one also learnt the scary word as well, in due time. Only my team and not the whole company, but that's enough people. No one flinched. They already knew my treatment is working, and they also saw me busting my a** at work, being at my best, without missing a day (hello, my name is workaholic, nice to meet you! ). They didn't have to think twice, whether they should change the way they treat me.
I think that's what made the difference. Everyone knew, but they didn't realize. They learnt the scary name, at the exact time they were ready to hear it.
PS: My boss knowing the exact situation is a blessing. It really helps a lot with appointments and tests, because they are almost always within working hours, and I am fully excused to miss a couple of hours of work. Plus, they value twice the work I do.
PS2: Forget about co-workers. What do you do with dating? Do you tell? I would say, definitely not at the beginning. I have to admit that I'm 16 months into treatment, single, and haven't dated anyone since diagnosis - at the beginning because I didn't feel like it, and then because of COVID. But those are excuses. I'm definitely rusty!!!