This is a small intestinal GIST and pT4 means that surgery has already been done and the tumor is large.
To know about the possibility of long-term life, we need some more details: mitoses in the tumor and molecular analysis in addition to the completeness of the surgery.
Considering this larger tumor and presumably all other factors favourable, there may be significant risk of tumor coming back later.
Imagining will certainly reduce those chances (if the molecular analysis is favourable).
Next Steps
Better go to a medical oncologist