Caring for patients with cancer is now being conducted in the era of a triple planetary crisis, which threatens our future on the planet. The impacts of this crisis are profound – disrupting cancer care due to displacement from extreme weather events, increasing cancer incidence and worsening cancer outcomes due to pollution, and threatening food and economic security due to loss of biodiversity. Clear that these changes will worsen in the coming years. The burden of these changes are not equitable, with the greatest impacts on countries that have contributed least to the crisis. While healthcare is the fifth leading cause of greenhouse gas emissions, climate awareness and activism in healthcare are low.

This paper examines the relationship between climate change and cancer care, highlighting regional disparities, environmental drivers of cancer risk, and the need for systemic adaptation. We present case studies from the Philippines, Nigeria, and Brazil each illustrating how climate-related events affect oncology delivery in vulnerable settings. We then explore how pollution, heat, and plastic use intersect with cancer risk and outcomes. Finally, we outline practical strategies and evidence-based toolkits for decarbonising cancer care across surgery, radiotherapy, medical oncology, and clinical trials. These insights, informed in part by global collaboration during London Global Cancer Week 2024, support the urgent integration of sustainability into oncology practice worldwide.