Humoral immune response against tumor antigens after treatment with a cancer antigen specific active immunotherapy and its association with improved clinical outcome

1. A method of treating a prostate cancer patient who is responsive to cancer antigen specific active immunotherapy (CASAI) using prostatic acid phosphatase as a target cancer antigen where the method comprises the steps of:

i. selecting a prostate cancer patient with white blood cells who has been treated with a cancer antigen specific active immunotherapy (CASAI) using prostatic acid phosphatase fused to granulocyte macrophage colony-stimulating factor as a target cancer antigen to activate the patient's white blood cells under ex vivo conditions and who has an increase in reactive antibody levels in two or more non-target predetermined biomarker antigens of prostate cancer where the increase in reactive antibody levels is determined using an immunoassay that detects reactive antibody levels for at least four of the following predetermined biomarker antigens of prostate cancer: PSA, KLK2, KRAS, ERAS, LGALS8, and LGALS3 compared to a baseline antibody level from before CASAI treatment; and,

ii. treating the prostate cancer patient with CASAI using a target cancer antigen comprising prostatic acid phosphatase fused to granulocyte macrophage colony-stimulating factor to activate the patient's white blood cells under ex vivo conditions.

2. The method of claim 1 , wherein the selected patient has elevated post-treatment antibody levels reactive to the target cancer antigen where the elevation is determined by obtaining a baseline and a post-treatment antibody level reactive to the target cancer antigen.

3. The method of claim 1 , wherein the baseline reactive antibody levels or the post-treatment reactive antibody levels from the patient are reactive IgG levels.

4. The method of claim 1 , wherein the reactive antibody levels are detected using a solid support surface and a fluorescent or enzymatic label.

5. The method of claim 1 , wherein the selected patient has an increase in reactive antibody levels of PSA and one or more other non-target predetermined biomarker antigens selected from the group consisting of KLK2, KRAS, ERAS, LGALS8, and LGALS3.

6. The method of claim 1 , wherein the selected patient has an increase in reactive antibody levels of ERAS and any one of four markers selected from the group consisting of KLK2, KRAS, LGALS8, LGALS3, and PSA.

7. The method of claim 1 , wherein the selected patient has an increase in reactive antibody levels of KRAS and any one of four markers selected from the group consisting of KLK2, ERAS, LGALS8, LGALS3, and PSA.

8. The method of claim 1 , wherein the selected patient has an increase in reactive antibody levels of ERAS.

9. The method of claim 1 , wherein the selected patient has an increase in reactive antibody levels of KLK2.

10. The method of claim 1 , wherein the selected patient has an increase in reactive antibody levels of PSA.

11. The method of claim 1 , wherein the CASAI is sipuleucel-T treatment.