An international expert panel has established the first formal clinical definitions and assessment frameworks for loneliness specifically in older cancer patients, distinguishing between emotional isolation (lacking intimate bonds) and social isolation (lacking broader community connections). The consensus emphasizes that loneliness in this population involves contextual factors including disease trajectory, treatment burden, and disrupted social networks. This standardization addresses a significant gap in geriatric oncology, where loneliness has been recognized as a health risk factor but lacked consistent clinical definition or measurement tools. The framework provides oncologists and geriatricians with structured approaches to identify and address isolation in older cancer patients, who face compounded risks from both age-related social changes and cancer-related disruptions. While the consensus represents important progress in recognizing loneliness as a clinical concern, its practical implementation will require validation studies and training programs for healthcare providers. The framework's emphasis on both emotional and social dimensions could inform more comprehensive psychosocial interventions, potentially improving treatment adherence and quality of life outcomes in this vulnerable population.