A composition for use as a medicament for the treatment of cancer, wherein said composition is administered to a subject according to an administration regimen comprising: (i) at least a first intratumoral injection; and (ii) at least a second sub-cutaneous or intramuscular injection, wherein said at least one intratumoral injection is administered prior to said at least one sub-cutaneous or intramuscular injection, and wherein said composition is an aqueous composition comprising particles wherein: (i) each of said particles comprises a complex of (a) polyinosinic-polycytidylic acid [poly(I:C)], or a salt or solvate thereof, wherein at least 40% of poly(I:C) molecules comprised in said particles have at least 850 base pairs, and at least 50% of poly(I:C) molecules comprised in said particles have between 400 and 5000 base pairs; and (b) water-soluble, linear homo-polyalkyleneimine or hetero-polyalkyleneimine, or a salt and/or solvate thereof, wherein the average molecular weight of said linear polyalkyleneimine is between 17 and 23 kDa; (ii) at least 90% of said particles has a mono-modal diameter distribution below 300 nm; (iii) said particles have a z-average diameter of less than or equal to 200 nm, as measured according to ISO 22412:2017, with polydispersity index of said particle diameter which is inferior to 1.5; (iv) said composition contains polyinosinic-polycytidylic acid [poly(I:C)] at a concentration of at least 0.5 mg/mL; (v) said composition has: a pH of between 2 and 4 and osmolality of between 200 and 600 mOsm/kg; and (vi) said composition has a zeta potential between 35 mV and 50 mV, according to ISO 13099-2:2012. (i) at least a first intratumoral injection; and (ii) at least a second sub-cutaneous or intramuscular injection, (i) each of said particles comprises a complex of (a) polyinosinic-polycytidylic acid [poly(I:C)], or a salt or solvate thereof, wherein at least 40% of poly(I:C) molecules comprised in said particles have at least 850 base pairs, and at least 50% of poly(I:C) molecules comprised in said particles have between 400 and 5000 base pairs; and (b) water-soluble, linear homo-polyalkyleneimine or hetero-polyalkyleneimine, or a salt and/or solvate thereof, wherein the average molecular weight of said linear polyalkyleneimine is between 17 and 23 kDa; (a) polyinosinic-polycytidylic acid [poly(I:C)], or a salt or solvate thereof, wherein at least 40% of poly(I:C) molecules comprised in said particles have at least 850 base pairs, and at least 50% of poly(I:C) molecules comprised in said particles have between 400 and 5000 base pairs; and (b) water-soluble, linear homo-polyalkyleneimine or hetero-polyalkyleneimine, or a salt and/or solvate thereof, wherein the average molecular weight of said linear polyalkyleneimine is between 17 and 23 kDa; (ii) at least 90% of said particles has a mono-modal diameter distribution below 300 nm; (iii) said particles have a z-average diameter of less than or equal to 200 nm, as measured according to ISO 22412:2017, with polydispersity index of said particle diameter which is inferior to 1.5; (iv) said composition contains polyinosinic-polycytidylic acid [poly(I:C)] at a concentration of at least 0.5 mg/mL; (v) said composition has: a pH of between 2 and 4 and osmolality of between 200 and 600 mOsm/kg; and (vi) said composition has a zeta potential between 35 mV and 50 mV, according to ISO 13099-2:2012.