If you've already had liver cancer, a relapse could come at any time. I would be looking especially at what's going on with Jupiter (transiting Jupiter, and transits to your natal Jupiter). Having a Jupiter-ruled sixth house could suggest that if you have health issues, they have to do with something Jupiter ruled, i.e. the liver.
I can't quite tell for sure where all the house cusps are in the chart you posted, but it looks like you may have Sagittarius intercepted in the sixth, which changes the picture a bit: Mars and/or Pluto would be the actual ruler(s) of your sixth house, but Jupiter has a kind of ghost share in it, and it rules your north node, which puts a little more emphasis on the sixth house. Since Pluto appears to be at the cusp of your sixth and Mars cohabits the same sign as Jupiter, there's a shared message here. You need some extra balance in those Jupiterian areas (Libra) and probably have to pay some extra attention to keeping your health in balance. With Pluto involved, it's no surprise that a big health issue came at a young age.
In and of itself, the south node moving through Sagittarius probably isn't enough of a trigger. But it might be a signal to pay attention: both to taking proper care of your liver, and, since the north node is transiting your twelfth house now, to the underlying spiritual and emotional factors. Complex illnesses such as cancer have complex causes. In the philosophy of healing that I've absorbed, from multiple teachers, illness almost always starts on a spiritual level. If you have a serious or chronic condition, that's a call for healing not just for your body, but also for the spirit.
The nodes transiting the sixth/twelfth house axis--and being in those houses natally, too--brings the spiritual/physical continuum into strong focus. If you do have a relapse, that's a strong call for attention. If you don't have a relapse, you're still getting a call to pay attention to those needs.
thank you