Synergy between photonics and biological approaches—A review of combination therapies for cancer theranostics

Cancer therapies have evolved considerably over the past several decades. Physical interactions, particularly through phototherapy as a new class of treatment modality, have become widely used. Phototherapy utilizes light to combat cancer by generating heat (photothermal therapy), reactive oxygen species (photodynamic therapy), or photochemical internalization, to kill targeted cells. While these therapies have shown promise in pre-clinical studies, they have demonstrated limitations in clinical cancer treatment. Primarily, while phototherapies excel in eliminating primary tumors, they often fail to provide systemic effects, particularly when treating metastatic cancers, in addition to certain undesirable side effects. Phototherapy has been combined with immunotherapy, nanomedicine, and other cancer therapies to overcome specific weaknesses and enhance the therapeutic benefits of individual treatments. These combinations often involve nanomaterials to deliver adjuncts for phototherapy to the tumor site, immune stimulants/adjuvants to enhance the immune response, and immune checkpoint inhibitors to counter immune suppression. Phototherapies may also be combined with specific photonics-related principles to enable simultaneous diagnostic and therapeutic effects, known as theranostics. Herein, we review current approaches to modern cancer therapies, such as nanotechnology-based therapies, immunotherapies, and especially phototherapy, and the combination of these therapies with diagnostic techniques in combating cancer.