Radiotherapy assisted with biomaterials to trigger antitumor immunity

As an extensively applied therapeutic approach to combat tumors, radiotherapy generates localized ionizing radiation to destruct tumor cells. Despite its importance in clinical oncology, radiotherapy would often cause significant organ toxicity, and its therapeutic effect is limited by tumor hypoxia. Moreover, although abscopal therapeutic effects have occasionally been observed, radiotherapy is still mostly employed as a local treatment method that could hardly control tumor metastases. In recent years, strategies involving biomaterials and nanomedicine have received increasingly high attention to enhance cancer radiotherapy. Beyond sensitizing tumors for radiotherapy via various mechanisms, many biomaterial systems with immune stimulating effects have also been introduced to boost the antitumor immunity post cancer radiotherapy. In this mini-review, we will summarize the progress of different biomaterials and nanomedicine systems in combination with radiotherapy to trigger antitumor immune responses and enhance the efficacy of immunotherapy, and discusses the perspectives and challenges of this research direction aimed at clinical translations.