Monoclonal antibodies (mAbs), which play a prominent role in
cancer therapy, can interact with specific
antigens on
cancer cells, thereby enhancing the patient's immune response via various mechanisms, or mAbs can act against cell
growth factors and, thereby, arrest the proliferation of
tumor cells.
Radionuclide-labeled mAbs, which are used in
radioimmunotherapy (RIT), are effective for
cancer treatment because
tumor associated-mAbs linked to cytotoxic
radionuclides can selectively bind to
tumor antigens and release targeted cytotoxic radiation. Immunological positron emission tomography (immuno-PET), which is the combination of PET with mAb, is an attractive option for improving
tumor detection and mAb quantification. However, RIT remains a challenge because of the limited delivery of mAb into
tumors. The transport and uptake of mAb into
tumors is slow and heterogeneous. The tumor microenvironment contributed to the limited delivery of the mAb. During the delivery process of mAb to
tumor, mechanical drug resistance such as
collagen distribution or physiological drug resistance such as high intestinal pressure or absence of lymphatic vessel would be the limited factor of mAb delivery to the
tumor at a potentially lethal mAb concentration. When α-emitter-labeled mAbs were used, deeper penetration of α-emitter-labeled mAb inside
tumors was more important because of the short range of the α emitter. Therefore, combination
therapy strategies aimed at improving mAb
tumor penetration and accumulation would be beneficial for maximizing their therapeutic efficacy against solid
tumors.