Orthotopic administration of (213)Bi-bevacizumab inhibits progression of PC3 xenografts in the prostate.

Aim: To investigate orthotopic targeted α-radioimmunotherapy for the control of early-stage PC3 prostate cancer nude mouse xenografts using the radiolabeled bevacizumab (BZ) immunoconjugate ((213)Bi-BZ), which emits short-range α-radiation.

Materials & Methods: 10(6) PC3 human prostate cancer cells were injected into the lower capsule of the mouse prostate gland 1 week prior to α-radioimmunotherapy. Mice were euthanized and assessed for tumour growth at 2 (two mice), 4 (two mice) and 6 weeks (three mice) post-therapy. The no-therapy control mice received a saline injection in equal volume to each BZ administration.

Results: (213)Bi-BZ is significantly more efficacious in inhibiting xenograft progression in the prostate gland compared with BZ alone (p = 0.009) and when compared with the 'no therapy' protocol (p < 0.0001).

Conclusion: Orthotopic administration of (213)Bi-BZ greatly improves the early control of organ-confined prostate cancer compared with BZ alone (p < 0.01).