ESTRO 2025 - Abstract Book

S29

Invited Speaker

ESTRO 2025

career development, ensuring that RTTs have access to advanced training in the latest radiation techniques and equipment. Additionally, we highlight our supportive and collaborative work environment, which resonates with many professionals. For example, we offer a variety of flexible work contracts, we encourage our RTT’s to be involved with projects and we support personal well-being which ensures that employees can maintain a healthy work-life balance. In terms of increasing our accessibility and visibility, we’ve utilized several strategies. We advertise in a newspaper targeted at scholars, offer an online platform where prospective RTTs can schedule coffee meetings with advisors, and distribute branded shoulder bags along with updated brochures. These efforts have allowed us to connect more effectively with potential candidates. We have also conducted market research to gain insights into how the new generation of professionals approaches career choices, ensuring that our recruitment strategies align with current trends. In response to market demands, we’ve made adjustments to the salary scale and job description for RTTs, incorporating the specialist RTT function, a new role with additional responsibilities. We also introduced zero hour contracts, which provide flexibility for RTTs currently working in other professions who wish to continue contributing to oncology care. Conclusion: In conclusion, our experience with RTT recruitment in the Netherlands has underscored the importance of a comprehensive and flexible recruitment strategy. By combining local outreach, strengthening our employer brand, offering professional development opportunities, and creating a flexible learning environment, we have been successful in attracting, training and retaining skilled RTTs. This approach ensures that we continue to meet the growing demand for specialized cancer care while fostering a supportive and innovative workplace.

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Speaker Abstracts Expanding roles of radiotherapy as an immune modulator Hiro Sato Heavy Ion Medical Center, Gunma University, Maebashi, Japan

Abstract:

The success of immune checkpoint inhibitors shed the light to the importance of the immune system in the cancer treatment. With the advent of the cancer immunotherapy era, radiotherapy is taking on new roles in the elimination of cancer cells. Radiotherapy is traditionally considered as a local therapy that works mainly by directly or indirectly damaging the DNA of irradiated cancer cells. Since 2000s, however, it has become clear that the immune response also plays a crucial role in how cancers respond to radiotherapy. It has now been shown that radiotherapy-induced DNA damage itself induces several immune responses. We have shown that DNA damage signaling in cancer cells after radiotherapy regulates PD-L1 expression. This upregulation requires ATR and Chk1 kinases, and depletion of BRCA2 or Ku80 enhances Chk1-dependent PD-L1 upregulation after X-ray irradiation. In addition, STAT1/3 signaling, which is activated via DNA damage, and IRF1 are required for DSB-dependent PD-L1 upregulation. Interestingly, carbon ion irradiation has also upregulated PD-L1 expression in cancer cells, and similar DNA damage signaling was involved in this upregulation. Based on these findings, we also assessed the reproducibility of the same pathway in the clinical setting and found a correlation between Ku80, a non-homologous end joining factor, and radiotherapy induced PD-L1 expression levels, in similar manner to preclinical data. Not only in PD-L1 upregulation, but other studies have also reported that radiotherapy can induce type I interferon via the cGAS/STING pathway, which