ESTRO 2024 - Abstract Book

S5164

Radiobiology - Immuno-radiobiology

ESTRO 2024

Objective: Investigate different combinations of treatments that could potentially enhance anti-tumor immunity in solid tumors. Here, C3H Mammary carcinoma of varying sizes were treated with anti-CTLA-4 and combined with either (i) Proton radiation, or (ii) VDA OXi4503, or (iii) Hyperthermia.

Material/Methods:

All experiments were carried out using a murine C3H mammary carcinoma that have previously shown to be less immunogenic [2]. These tumors were grown in the right rear foot of CDF1 mice. Treatments were started (day 0) when tumors reached sizes of around 50, 100, 200 and 400 mm 3 , representing varying tumor load or burden. These included either proton radiation (single dose of 20 Gy given on day 0), or OXi4503 (50 mg/kg, injected i.p. on days 0, 3, 7, and 10), or hyperthermia (single fraction of 42,5 °C given for 60 minutes on day 0) followed by anti CTLA-4 (injected i.p. on days 1, 4, 8, and 11). The study was concluded at day 90 and the endpoint was time in days taken for tumor to grow to 1000 mm3 from the day treatments were initiated (day 0). The difference in days for the tumor to reach 1000 mm3 was compared across different treatment groups. Furthermore, dose response curve (proton radiation and anti-CTLA-4) for 100 mm3 size tumors was also carried out using tumor growth time assay.

Results:

Median time in days taken for tumors to reach 1000 mm3 for different treatment groups are shown in the Table 1 below.

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