ESTRO meets Asia 2024 - Abstract Book

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Invited Speaker

ESTRO meets Asia 2024

521

Which target volume should we select when radiotherapy is combined with immune blockers?

Vincent Grégoire

Radiation Oncology, Leon Berard Cancer Center, Lyon, France

Abstract

Ionizing radiations are a very potent inducer of an immune response by releasing Damage Associated Patterns (DAMPS) stimulating the immune cycle via activation of the tumor antigen presenting cells and the cancer cell specific T-lymphocytes. Pre-clinical experiments and clinical examples are in line with this finding. However, when combined with concomitant chemo-radiotherapy in randomized phase III trials for loco-regional treatment of head and neck or lung tumors, immune blockers failed to show an improvement in Progression-Free Survival or Overall Survival. The reasons for such failures are still unknown. Among various hypotheses, one can postulate that regional irradiation and irradiation of major blood vessels such as the carotid arteries (for head and neck tumors) or the pulmonary arteries and maybe partly the aorta (for lung tumors) and the lymph nodes associated with these vessels decreased the pool of immune cells needed to elucidate an immune response. The balance between ionizing radiation as very efficient immunosuppressor, and a potent stimulator of an immune response may turn in favor of the immunosuppression.

This lecture will review the clinical data on concomitant association of immune blockers and radiotherapy, discuss the potential reasons for the unsuccessful trials, and propose new trial design testing such hypothesis.

522

Correct sequencing of therapies

Dora Lai Wan Lai Wan Kwong

Clinical Oncology, The University of Hong Kong, Hong Kong, Hong Kong

Abstract

As immunotherapy (IO) with checkpoint inhibitors has proven to be effective in advanced/metastatic disease setting for many cancers, its integration into definitive treatment in early stage disease is also tested. Radiotherapy (RT) is an established loco-regional treatment and is often used in combination with systemic treatment like chemotherapy. Radiotherapy can induce immunogenic cell death which stimulates immune response, thus combining radiotherapy (RT) and immunotherapy (IO) have potential synergistic effect. However, the best sequence of combining these modalities is uncertain. Different trials have tested combining radiotherapy/chemoradiotherapy with IO in different sequence like neoadjuvant, concurrent, adjuvant or continuous throughout treatment. Results from Phase III trials can highlight the importance of sequence of combination and selection of patients for IO use.