ESTRO 2022 - Abstract Book

S910

Abstract book

ESTRO 2022

PO-1075 Results of Concurrent SBRT and Immunotherapy in Recurrent and Metastatic Head and Neck Cancer

M.T. Yilmaz 1 , S. Yuce Sari 1 , B.Y. Aktas 2 , S. Aksoy 3 , I. Gullu 3 , M. Cengiz 1 , G. Ozyigit 1 , G. Yazici 1

1 Hacettepe University Faculty of Medicine, Radiation Oncology, Ankara, Turkey; 2 Afyonkarahisar State Hospital, Medical Oncology, Afyonkarahisar, Turkey; 3 Hacettepe University Faculty of Medicine, Medical Oncology, Ankara, Turkey Purpose or Objective Median survival in metastatic/recurrent HNC (M/R HN-SCC) is less than 1 year, and locoregional recurrence (LRR) is the main cause of cancer-related death. Combined local and systemic therapies are required in order to achieve better results. Stereotactic body radiotherapy (SBRT), which can work synergistically with immune checkpoint inhibitors (ICI), can be a promising treatment option with more satisfactory response rates. We frequently apply 3x8 Gy SBRT concurrently with ICI in patients with M/R HN-SCC, and this study aims to share the clinical results and toxicity profile of these patients. Materials and Methods Fifteen patients diagnosed with M/R HN-SCC were evaluated retrospectively. All patients received SBRT to all metastatic and recurrent foci with concurrent ICI. Toxicity was evaluated according to the Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC) criteria. Results The median age at the time of diagnosis was 57 years (range: 19-80 years). Four patients were female, and 11 were male. A total of 25 lesions were irradiated in 15 patients between January 2019 and July 2020. Sixteen of these lesions were re- irradiation, and three of them received the 3 rd course of RT. At the last control, four patients were dead; one was due to disease progression. Eight patients had complete responses, one had a partial response, four had stable diseases, and two had progressive diseases. None of the lesions irradiated via SBRT with concurrent ICI progressed during the follow-up except for one. Therefore, the SBRT-C rate was 96%. The 6-, 12-, and 24-month OS rate was 93%, 76%, and 57%; the PFS rate was 86%, 50% and 33%, %the LRFS rate was 86%, 70%, and 53%, the RRFS rate was 86%, 65%, and 49%, and the DMFS rate was 93%, 61%, and 46%, respectively. Mean OS was 21.2 months (standard error [SE]:2.2, 95% confidence interval [CI]: 17.7- 25.7) and mean PFS was 16.2 months (SE: 2.4, 95% CI: 11.4-20.9). The abscopal effect was observed in two patients who both had nasopharyngeal cancer. Acute grade 1 SBRT-related dermatitis was observed in only one patient and no other acute side effects were observed. A stent was placed in the carotid artery in two patients prior to re-irradiation due to the late SBRT-related carotid blowout syndrome (CBOS) risk. In one patient CBOS could be prevented but the other patient succumbed to CBOS. Other late SBRT-related side effects were observed in three patients (dysphagia, pituitary insufficiency, skull base osteomyelitis). A total of five patients developed ICI-related toxicity (recall dermatitis in one patient and hypothyroidism in four patients). Conclusion By using ICI and SBRT concurrently, we have achieved excellent OS and PFS and also achieved satisfactory outcomes in HN- SCC re-irradiation which is one of the most challenging areas of RT. 1 Heinrich Heine University, Düsseldorf University Hospital, Dept. of Radiation Oncology, Düsseldorf, Germany; 2 West German Proton Therapy Centre Essen (WPE), Dept. of Particle Therapy, Essen, Germany Purpose or Objective Checkpoint inhibitors have become the standard of care for recurrent inoperable or metastatic head and neck cancer (rmHNC). In patients with high disease or symptom burden, oncologists are inclined to add platinum-based chemotherapy, despite its high toxicity. Radiation therapy (RT) is established for the treatment of symptomatic lesions and for tertiary prevention. RT was not allowed and/or not reported in the pivotal studies. The aim of this study was to evaluate the combination of checkpoint inhibitors and RT, also in the non-trial population (multimorbid, elderly and frail patients). Materials and Methods We identified 83 patients with rmHNC treated with a programmed cell death protein-1 (PD-1) inhibitor since 2017 in the electronic medical records of our head and neck cancer center. Retrospectively collected data (characteristics, therapy, outcome, acute and late toxicity) were investigated by descriptive statistics and survival analyses using the Kaplan-Meier method, the log-rank test, and the Cox regression model. We performed all calculations using R version 4.1.1. Results Median age was 64 years (range: 28-92), median Charlson comorbidity index was 8 (range: 3-13). 38.6% of the patents were older than 70 years at the start of therapy. 33.7% had an ECOG performance score ≥ 2. The median follow-up time was 18.2 months. 63.9% of the patients received additional RT. The median overall survival (OS) rate was 7.8 months (95% confidence interval [CI]: 5.2-13.9 months). There were no difference in outcomes among three age subgroups (<60 years, 60-70 years and 70+ years at baseline). We found an overall response rate of 33.8%, with a median duration of response of 21.4 months. The addition of RT to systemic treatment was associated with favorable survival: hazard ratio of 0.5 (CI: 0.28-0.87; p=.015). This association was more pronounced, if escalated RT (defined as >50Gy EQD2 or RT of all lesions) was used. Complete PO-1076 Do patients with rmHNC treated with checkpoint inhibitors benefit form additional radiotherapy? B. Tamaskovics 1 , J. Haussmann 1 , D. Jazmati 1,2 , J. Neuwahl 1 , A. Rezazadeh 1 , E. Bölke 1 , W. Budach 1 , C. Matuschek 1