Why not surgically resect the tumor before CAR-T cell therapy? Won't that be more efficient?
CAR-T cell therapy (Chimeric Antigen Receptor-T cell Therapy) is most effective in treating hematological malignancies. Hematological malignancies (known as blood cancers in common parlance) mean the cancers produced due to over-proliferation of hematopoietic stem cells and the liberation of the immature cells into the circulation . Till now all clinical trials of CAR-T cell therapy has seen more and more success. With the development of second, third and fourth generation (also called TRUCK T cells) CAR-T cells the percentage of remission is increasing. But  almost all these advances are in hematological malignancies.

Clinical trials on solid tumors has shown that the "efficacy is not as remarkable as in the case of hematological malignancies". 

The question asked was about resection of the tumor before treating with CAR-T cell therapy. This question is valid only in case of solid tumors (you can't resect blood as it is liquid). As I already said this therapy is only used for blood cancer till now, so there is no question of surgery before the therapy.

I think I could answer your query above. If you want to gain more knowledge, then read below - 


The best use of this therapy in blood cancers is after hemato-poietic stem cell transplantation (note that it is not surgical resection)
If you ask, why this therapy was not successful in solid tumors, I would recommend to read the review published in Springer with the title "Hurdles of CAR-T cell-based cancer immunotherapy directed against solid tumors".


Recently however there are new developments that are helping to apply this immunotherapeutic procedure in case of solid tumors also and in that case it is usually given after surgical resection.