ESTRO 2024 - Abstract Book

S5172

Radiobiology - Immuno-radiobiology

ESTRO 2024

Conclusion:

The cytotoxic effect of NK cells on lung cancer cells of both monolayer and spheroid was increased by IR. This is due to the increased interaction of NK cells with the lung cancer cells, which was facilitated by the radiation induced overexpression of NK cell activating ligands on the cancer cells’ surface.

Keywords: NK cells, Lung cancer cells, Migration

1368

Digital Poster

Radiation-related lymphopenia post prostate stereotactic body radiation therapy ± pelvic irradiation

Kelly Gaudian 1 , Min Jung Koh 1 , Min Ji Koh 1 , Ryan Collins 1 , Zoya Zwart 1 , Malika Danner 1 , Alan Zwart 1 , Marilyn Ayoob 1 , Thomas Yung 1 , Deepak Kumar 2 , Michael Carrasquilla 1 , Michael Atkins 3 , Simeng Suy 1 , Sean P Collins 1 1 Georgetown University Hospital, Department of Radiation Medicine, Washington, DC, USA. 2 North Carolina Central University, Biotechnology Research Institute, Durham, NC, USA. 3 Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Department of Oncology, Washington, DC, USA

Purpose/Objective:

Prior studies suggest lymphopenia following radiation therapy may impact cancer control and toxicity. Chronic radiation-related lymphopenia (RRL) has been noted in prostate cancer patients treated with conventionally fractionated pelvic radiation therapy. 1 Utilization of high integral dose therapies such as stereotactic body radiation therapy (SBRT) on RRL is less well characterized. This prospective study sought to evaluate the impact of prostate SBRT plus or minus supplemental pelvic nodal radiation (PNI) on RRL.

Material/Methods:

Between 2012 and 2023, 226 men were treated at Georgetown with robotic SBRT using the CyberKnife® (CK) (35.00-36.25 Gy in 5 fractions) alone or in combination with supplemental PNI (37.5-45.0 Gy in 15-25 fractions) per an institutional protocol (IRB#: 2012-1175). Baseline absolute lymphocyte count (ALC, k/μL) was measured 1-2 hours prior to robotic SBRT and at each follow-up appointment (1, 3, 6, 9, 12, 18, and 24 months). Lymphopenia was graded using the CTCAEv.4 (Grade 1 (0.8-1.0 k/μL, Grade 2 (0.5-0.8 k/μL), Grade 3 (0.2-0.5 k/μL), Grade 4 (<0.2 k/μL)). To compare two different treatment groups, Wilcoxon signed-rank test was used. A p-value of < 0.05 determined statistical significance.

Results:

Of 226 patients (SBRT alone: n = 169, SBRT + PNI: n = 57), the median age was 72 years, and 45% of patients were non-white. Baseline lymphopenia was uncommon. In the SBRT alone group, the baseline ALC of 1.7 k/μl decreased by 21% (1.4 k/μL) at 3 months and then stabilized. 38% of these men experienced lymphopenia in the two years