Tom's radiation therapy is on at the moment.

[tufguy]

Is it correct to say that something is "on" instead of "going on"?

1) Tom's radiation therapy is on at the moment.
2) Don't take this medicine until your chemo therapy is on.
3) Interviews are on in my company.

 

[emsr2d2]

"On" doesn't work in any of them. Nor does "going on".

1. Tom is undergoing radiotherapy at the moment.
2. Don't take this medicine until your chemotherapy has started.
3. Interviews are being conducted at my company.

(Note that we generally use "radiotherapy", not "radiation therapy". "Chemotherapy" is a single word.)