“Light” from low-level laser therapy (LLLT), through a process called photobiomodulation (PBM), has been in existence in supportive care in cancer, in particular in the management of oral mucositis (OM) in patients undergoing chemotherapy, radiation therapy and haematopoietic stem cell transplantation. In this book, the authors attempt to portray the current status of the supportive care interventions that are possible with PBM using LLLT in patients undergoing cancer treatment for solid tumours, haematological malignancies, and head and neck cancers.