Conclusion
There is abundant evidence from in vivo and in vitro experiments that ionizing radiation, applied to cancer cells or host cells, to the tumor, the whole host or the putative site of tumor development may stimulate the metastatic process. Clinical observations do not directly confirm these data, leaving open the question whether or not radiotherapy enhances metastasis. The overall net outcome of radiotherapy is beneficial as it may reduce metastasis and prolong survival. This therapeutic benefit does not exclude a limitation of the benefit by negative effects of the irradiation on the cancer cells or on the host. The present review of literature suggests clinical trials to investigate correction of the pro-invasive and pro-metastatic activities of radiation by anti-inflammatory or other agents shown to be effective in preclinical settings.
This is about remote tumors not responding to immunotherapy.
I do agree with you and have posted about how radiation does the effect you described.