Even for PTS, I would still not use cure or incurable. Treatable is the more accurate term.
Scholars are making it harder with their increasing definition expansion of terms within dictionaries too.
Cure can mean: recovery or relief from a disease; or, a complete or permanent solution or remedy.
The problem is that they are now including everything and anything, which crosses with other definitions.
Incurable means: not likely to be changed or corrected.
Define likely? Likely: having a high probability of occurring or being true.
Ok, so for incurable, you can rule it out because PTSD has a majority full recovery, which places it on the positive side of relief.
Now treatable: capable of being treated : yielding or responsive to treatment.
From everything above, PTSD recovery falls much closer to treatable, as it is responsive to treatments of various type, and some will get full relief, others partial, others not much at all.
So if you want to use the term PTSD, it does not directly fall into curable or incurable, because not everyone will get relief from treatment, incurable is inaccurate as per above, thus leaving treatable which more aptly describes the outcome for EVERY person with PTSD.