When a terminally ill dancer becomes part of a radical treatment group, she uncovers the deadly secrets of a renegade oncologist and must battle to save more lives than her own.

Thank you Jean-Marie. The hero IS a young mother, so that works.
Funnily this script, is far less developed than the other I have posted a logline for- but it seems to feel tighter.
Partly, I am trying decide which to focus on right now.

Hi sarapensalfini,

Seems to be good.
I see a Hero, her flaw, her quest, her antagonist, the conflict, what's at stakes... the whole story in 31 words.

I don't see what could improve your logline except something that increase empathy for your hero (maybe replace "dancer" by "young mother", or something like that...).

I saw two good movies close to the genre : "Coma" and "Extreme mesures". In these two movies, the hero was a doctor. I think that the fact the hero is a patient is a bonus because it increases the stakes and it makes the quest harder.