Radiolabeled somatostatin analogues based on octreotide have proven useful in the management of somatostatin receptor subtype 2 (sstr2)-positive tumours in clinical trials. The aim was to compare the potency and evaluate the combination of 111In- and 177Lu-DOTATOC with a double-deleted version of vaccinia virus (ddVV), an oncolytic virus for inhibiting the growth of sstr2-expressing human embryonic kidney (HEK-293) cells or MC-38 murine colon cancer cells grown as monolayers or as spheroids. Cytotoxicity studies were carried out using ddVV, 111In-DOTATOC and 177Lu-DOTATOC, individually or in combination on MC-38 spheroids, HEK-293 cells and spheroids. HEK-293 cell growth in spheroids was reduced to 17.2 ± 4.9% and 26.5 ± 6.3 % with 111In-DOTATOC and 177Lu-DOTATOC alone and 13.1 ± 7.1% and 0% in combination, respectively. MC-38 spheroids showed greater toxicity in combination treatment. Combination of ddVV with 111In- or 177Lu-DOTATOC is only advantageous in monolayer culture. No advantage was observed in spheroid models.

Radiolabeled somatostatin analogues based on octreotide have proven useful in the management of somatostatin receptor subtype 2 (sstr2)-positive tumours in clinical trials. The aim was to compare the potency and evaluate the combination of 111In- and 177Lu-DOTATOC with a double-deleted version of vaccinia virus (ddVV), an oncolytic virus for inhibiting the growth of sstr2-expressing human embryonic kidney (HEK-293) cells or MC-38 murine colon cancer cells grown as monolayers or as spheroids. Cytotoxicity studies were carried out using ddVV, 111In-DOTATOC and 177Lu-DOTATOC, individually or in combination on MC-38 spheroids, HEK-293 cells and spheroids. HEK-293 cell growth in spheroids was reduced to 17.2 ± 4.9% and 26.5 ± 6.3 % with 111In-DOTATOC and 177Lu-DOTATOC alone and 13.1 ± 7.1% and 0% in combination, respectively. MC-38 spheroids showed greater toxicity in combination treatment. Combination of ddVV with 111In- or 177Lu-DOTATOC is only advantageous in monolayer culture. No advantage was observed in spheroid models.