theranostic target that can add on to the armamentarium in the management of

patients with advanced melanoma.

Radio-immunotherapy comprises tagging a radiolabel with a monoclonal anti-

body (or minibodies, haptens, etc.). The antibody is chosen according to the specific

cancer antigen being targeted, e.g., CD20 in lymphomas. The antibody localizes to

the disease sites and mediates antibody-induced cytotoxic effects. Additionally, the

radiolabel irradiates the cell to which the antibody is bound and adjacent tumor cells

to which the antibody might not be bound (bystander effect). Thus, the cell-killing

efficacy is increased. ¹³¹I-Tositumomab and ⁹⁰Y-Ibritumomab tiuxetan are the only

FDA-approved radio-immunotherapies in lymphomatous diseases till date (Kraeber-

Bodéré et al. 2016). Recently, a novel anti-CD37 targeting radioimmunotherapy,

177Lu-Lilotomab satetraxetan, was given the fast-track designation by the FDA due

to its encouraging results in Phase 1/2a studies (Kolstad et al. 2020).

Chemokine receptors play an important role in cancer progression, and among

these chemokine receptors, CXCR4 is the most widely expressed receptor on

malignant tumors, and its role in tumor biology has been studied extensively

(Zlotnik et al. 2011). No in vivo method suitable for whole body CXCR4 disease

quantification has been described, and this unmet clinical need has been reported

recently. 68Ga-Pentixafor is a CXCR4 targeting high affinity PET imaging probe,

and

the

tracer

has

been

evaluated

in

multiple

myeloma

(Fig.

7.3),

in

lymphoproliferative disorders, and in lung carcinoma (Fig. 7.4), and the imaging

results are extremely promising (Watts et al. 2017).

Fig. 7.3

68Ga-Pentixafor PET/CT in a 60-year-old male with multiple myeloma showing diffuse

and focal tracer uptake in axial and appendicular skeleton (MIP image—a and sagittal fused

PET/CT image—b), showing diffuse and focally increased tracer uptake in marrow and lytic

bony lesions. The corresponding ¹⁸F-FDG PET images (c, d) did not show any abnormal uptake

in marrow and elsewhere in the skeleton

104

B. Singh et al.