Abscopal Effect Following Immunotherapy and Combined Stereotactic Body Radiation Therapy in Recurrent Metastatic Head and Neck Squamous Cell Carcinoma: A Report of Two Cases and Literature Review

Abstract

Objective: We present two patients with recurrent, metastatic head and neck squamous cell carcinoma (R/M HNSCC) after platinum-based chemotherapy and radiotherapy (RT) with complete response via abscopal effect following combined immunotherapy (IT) and stereotactic body radiation therapy (SBRT). We review the literature for patients undergoing combined treatment with IT and RT to identify potential cases of abscopal response. Study Design: This is a case series with a contemporary review of the literature. Methods: Retrospective chart review identified two patients with potential abscopal responses after IT and RT for R/M HNSCC. The MEDLINE database was queried using the search terms “abscopal AND head and neck squamous cell carcinoma” and “immunotherapy AND stereotactic body radiation therapy.” Results: Two patients with metastatic HNSCC developed complete responses via a possible abscopal effect following combined SBRT and IT. Interim follow-up of both patients revealed a sustained, complete response. We examine the immunogenic effects of RT and report the first cases of potential abscopal effect for R/M HNSCC. We also review several preclinical studies demonstrating the synergistic efficacy of combined RT and IT with a discussion of possible mechanism. Conclusion: Observation of abscopal effect with combined IT and RT is currently under investigation through several preclinical studies and trials. To the best of our knowledge, these are the first two reported cases of abscopal effect for patients with HNSCC. We report two patients with R/M HNSCC with sustained, complete response after systemic IT and local RT.

Risk factors for distant metastasis in locoregionally controlled oral squamous cell carcinoma: a retrospective study

“…This is a rare phenomenon in which radiotherapy causes the tumor to halt its growth even in metastases that are far from the irradiated area. This phenomenon has received renewed attention in head and neck cancer 15,16 . The synergistic impact of the abscopal effect and immune checkpoint inhibitors could aid in activating the immune system and suppressing distant metastases.…”

Exosomal PD-L1: New Insights Into Tumor Immune Escape Mechanisms and Therapeutic Strategies

“…This represents a promising therapeutic strategy for tumors and has drawn increased attention (Liu et al, 2018;Ngwa et al, 2018;Rodriguez-Ruiz et al, 2018;Choi et al, 2020). Interestingly, blocking ExoPD-L1 suppresses the growth of not only the local tumor, but also tumors at a distant site (Poggio et al, 2019).…”

“…The abscopal effect refers to that treatment of a local tumor leads to the regression of distant tumors ( Postow et al, 2012 ; Demaria and Formenti, 2020 ; Fionda et al, 2020 ; Mondini et al, 2020 ). This represents a promising therapeutic strategy for tumors and has drawn increased attention ( Liu et al, 2018 ; Ngwa et al, 2018 ; Rodriguez-Ruiz et al, 2018 ; Choi et al, 2020 ). Interestingly, blocking ExoPD-L1 suppresses the growth of not only the local tumor, but also tumors at a distant site ( Poggio et al, 2019 ).…”

Abscopal effect of stereotactic radiotherapy combined with anti‐PD‐1/PD‐L1 immunotherapy: Mechanisms, clinical efficacy, and issues

“…This case, together with the related phenomenon, caused wide public concern and a growing number of similar reports have been since published in various journals. Several studies [12][13][14][15][16][17][18][19] have detailed the characteristics and results of clinical cases after SABR and anti-PD-1/PD-L1 combination treatment over the recent years (Table 1). However, public opinions are still polarized on those insufficient statistical results regarding the abscopal effect.…”