ESTRO 2024 - Abstract Book

S5182

Radiobiology - Immuno-radiobiology

ESTRO 2024

subpopulations changes, which were suggested in the literature to serve as predictive immunotherapy markers, as well.

Material/Methods:

We recruited 110 patients with triple-negative breast cancer (TNBC) starting in September 2021. We collected blood samples from these patients before the start of therapy and after each type of therapy: post-chemotherapy, post-surgery, post-possible radiation therapy, post-capecitabine chemotherapy, and three months after completing all treatments. The patients received systemic treatments based on standardized chemotherapy protocols following international recommendations. We compared the values of patients' blood samples with the values of age- and gender-matched healthy controls. In the samples taken at different time points, we measured and compared more than seventy cell populations using six fluorescent panels. However, we could measure the samples from patients, who have already finished their complex therapies (sometimes lasting one year).

Results:

In our measurements, the frequency of NKG2A+ NK cells increased due to chemotherapy, but decreased due to radiotherapy. The occurrence of NKG2D+ NK cells was reduced by all therapeutic modalities, and their numbers began to rise only three months after the completion of treatments but still significantly differed from the levels in healthy controls. The appearance of NKp30+ NK cells was more common compared to healthy individuals and was reduced by both chemotherapy and radiotherapy. The frequency of PD1+ NK cells was lower not only in untreated patients, but also in breast cancer patients after any treatment compared to healthy controls. Radiation therapy slightly increased their occurrence. In our measurements, the frequency of PD1+, PDL1+, and CTLA4+ T cells were higher after chemotherapy, while the occurrence of PDL2+ and CTLA4+ CD8+ cells increased by surgery. According to our results, the frequency of LAG3+, TIGIT+, VISTA+ and Ox40+ cells among CD8+ cells increased most notably after surgical intervention. For TIM3+ cells, we only found a decrease, but for 4-1BB+ cells we only found increase.

Conclusion:

The therapy for early TNBC patients is long and complex, and the above results are only partial, but they clearly show that different treatments have varying effects on specific cell populations targeted by immunotherapies. We plan to continue measuring the finishing patients and compare the immune cell changes with therapeutic outcomes to select the subpopulations with predictive capacity.

Keywords: immune cells, complex therapy, PD1+ CD8+ cells

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Poster Discussion

Protons and X-rays combined with anti-PDL1 in two oral cancer tumors with different immunogenicity

Anne Marit Rykkelid 1 , Priyanshu M Sinha 2 , Charlemagne A Folefac 2 , Michael R Horsman 2 , Brita S Sørensen 3 , Tine M Søland 4 , Olaf JF Schreurs 4 , Eirik Malinen 1 , Nina FJ Edin 1