It all depends of a person. I never had problem talking to anybody who ever confided to me about any medical problem and I assumed other people are like that too, but no, they are not.
Many people do not now how to react when they hear word "cancer" and they would rather not hear it. Those people are usually very self-centered IMHO and for them hearing about somebody's plight is something that "burdens them" and they do not want to think about it. They usually explain it with "I do not know what to say" which is bogus. I have a friend like that. Any time one of acquaintances or even her relatives gets cancer she purposefully never ask them how are they doing or if they need help because she does not want to spend "energy" thinking about that disease, it might make her upset *eyeroll. Her brother in law has prostate cancer, any time I ask her how is he doing she says " emm, I do not know, I suppose he is well" (????????) . When her neighbor's son got stomach cancer I asked if he is doing OK , her answer "I do not know, I did not ask his mom" , and she is talking to that woman on daily bases ! Some things I would never understand ... So yeah, we will not share except with our daughters and one or two very close friends that are proven as discrete people. My husband also told his private business partner that he has PC since it was responsible thing to do. On the other hand he would not tell about cancer to anybody on his "regular job", because he knows of a friend who lost his job after announcement of cancer diagnosis.
So Madissonman - it is not your fault some of bike buddies are freaking out , they were not true friends to begin with so spend time with ones that are supportive , positive and can laugh even in the time of adversity.