A radiohalogenated compound for use in a method of treating a metastatic cancer comprising a primary malignant solid tumor and one or more metastatic malignant solid tumors capable of causing concomitant immune tolerance in a subject, comprising the steps of: (a) administering to the subject an immunomodulatory dose of the radiohalogenated compound which compound is differentially taken up by and retained within malignant solid tumor tissue, wherein the radiohalogenated compound has the formula: or a salt thereof, wherein: R 1 comprises a radioactive halogen isotope; a is 0 or 1; n is an integer from 12 to 30; m is 0 or 1; Y is selected from the group consisting of -H, -OH, -COOH, -COOX, -OX, and -OCOX, wherein X is an alkyl or an arylalkyl; and R 2 is selected from the group consisting of -N + H 3, -N + H 2 Z, -N + HZ 2, and -N + Z 3, wherein each Z is independently an alkyl or an aryl; and (b) performing in situ tumor vaccination in the subject at the primary malignant solid tumor using one or more treatments capable of stimulating specific immune cells within the tumor microenvironment, wherein the one or more treatments capable of stimulating specific immune cells within the tumor microenvironment comprise injecting into or applying to the primary malignant solid tumor a composition comprising one or more agents capable of stimulating specific immune cells within the tumor microenvironment, wherein the one or more agents capable of stimulating specific immune cells within the tumor microenvironment comprise a combination of (a) an immunostimulatory mAb that is an antibody to a tumor-specific antigen and (b) an immunostimulatory cytokine; wherein the method further comprises treating the primary malignant solid tumor with external beam radiation therapy (xRT). (a) administering to the subject an immunomodulatory dose of the radiohalogenated compound which compound is differentially taken up by and retained within malignant solid tumor tissue, wherein the radiohalogenated compound has the formula: or a salt thereof, wherein: R 1 comprises a radioactive halogen isotope; a is 0 or 1; n is an integer from 12 to 30; m is 0 or 1; Y is selected from the group consisting of -H, -OH, -COOH, -COOX, -OX, and -OCOX, wherein X is an alkyl or an arylalkyl; and R 2 is selected from the group consisting of -N + H 3, -N + H 2 Z, -N + HZ 2, and -N + Z 3, wherein each Z is independently an alkyl or an aryl; and R 1 comprises a radioactive halogen isotope; a is 0 or 1; n is an integer from 12 to 30; m is 0 or 1; Y is selected from the group consisting of -H, -OH, -COOH, -COOX, -OX, and -OCOX, wherein X is an alkyl or an arylalkyl; and R 2 is selected from the group consisting of -N + H 3, -N + H 2 Z, -N + HZ 2, and -N + Z 3, wherein each Z is independently an alkyl or an aryl; and (b) performing in situ tumor vaccination in the subject at the primary malignant solid tumor using one or more treatments capable of stimulating specific immune cells within the tumor microenvironment, wherein the one or more treatments capable of stimulating specific immune cells within the tumor microenvironment comprise injecting into or applying to the primary malignant solid tumor a composition comprising one or more agents capable of stimulating specific immune cells within the tumor microenvironment, wherein the one or more agents capable of stimulating specific immune cells within the tumor microenvironment comprise a combination of (a) an immunostimulatory mAb that is an antibody to a tumor-specific antigen and (b) an immunostimulatory cytokine; wherein the method further comprises treating the primary malignant solid tumor with external beam radiation therapy (xRT).