Barbara Ewals is the Chief Executive Officer (ex‑officio) of the International Society of Geriatric Oncology (SIOG), the global multidisciplinary society dedicated to improving cancer care for older adults. She manages the organisation’s operations, supports governance and strategic planning, and works with the Board, Secretariat, networks, committees, and continental branches to advance SIOG’s mission across more than 80 countries. Ewals has previous experience as Executive Director at Initiative for Global Resilience and expertise in international partnerships and stakeholder engagement.
Under her leadership, SIOG has expanded its global reach and strengthened education, research, and collaboration in geriatric oncology, including initiatives promoting integrated care models such as the GerOnTe Consortium. Based in Bangkok, Thailand, she contributes to shaping multidisciplinary practice, policy dialogue, and capacity building for cancer care in ageing populations.
The 100 CEOs featured here reflect the diversity and complexity of modern oncology leadership. In 2025, some lead the world’s largest cancer institutions; others guide specialized societies or emerging innovators. What unites them is responsibility: for millions of patients, for the integrity of science, and for the future direction of cancer care globally.
This list is not a celebration of power, but a recognition of stewardship, accountability, and impact – and of the leaders whose choices continue to shape the fight against cancer. For the many deserving individuals not mentioned in this list, we will continue to acknowledge, honor and elevate your voices in our daily publications from across the world.
See the full list of The 100 Influential CEOs in Oncology in 2025 and stay tuned For other special category nominations.
