The G8 screening tool is widely recommended for the identification of frailty in older adults with cancer. However, prospective validation data in the Portuguese population are currently lacking.

This prospective observational study aims to evaluate the diagnostic performance of the G8 screening tool compared with a Comprehensive Geriatric Assessment (CGA) in older adults with cancer. Patients aged ≥70 years with solid tumors will be assessed using both the G8 screening tool and a multidimensional CGA. Frailty will be defined as impairment in at least one CGA domain. The performance of the G8 will be evaluated in terms of sensitivity, specificity, and area under the receiver operating characteristic curve.

This study aims to provide the first prospective validation of the G8 screening tool in Portuguese older adults with cancer and to support its implementation in clinical practice.

Older adults represent a growing proportion of the oncology population and are characterized by significant heterogeneity in functional status, comorbidities, and physiological reserve. These factors may influence treatment tolerance, toxicity, and clinical outcomes.

International guidelines from European Society for Medical Oncology (ESMO), American Society of Clinical Oncology (ASCO), and International Society of Geriatric Oncology (SIOG) recommend the use of geriatric assessment to guide treatment decisions in older adults with cancer. The Comprehensive Geriatric Assessment (CGA) is considered the reference standard for evaluating multiple health domains, including functional status, cognition, nutrition, psychological state, social support, and comorbidities. However, its routine implementation is limited by time and resource constraints.

The G8 screening tool is a rapid geriatric screening instrument developed specifically for older patients with cancer. It consists of eight items derived mainly from the Mini Nutritional Assessment, along with additional clinical parameters such as age, mobility, polypharmacy, and self-perceived health status. A score ≤14 is generally considered indicative of frailty and the need for further assessment.

Although the G8 has been validated in several international settings, prospective validation data in the Portuguese population are lacking.

This prospective observational study aims to evaluate the diagnostic accuracy of the G8 screening tool compared with a multidimensional CGA in older adults with cancer in Portugal. Frailty will be defined as impairment in at least one CGA domain.

To our knowledge, this study represents the first prospective validation of the G8 screening tool in Portuguese older adults with cancer. The results of this study may support the implementation of geriatric screening strategies and improve clinical decision-making in oncogeriatric care in Portugal.

Inclusion Criteria:

• Age ≥70 years;
• Histologically confirmed solid malignancy, regardless of tumor site or stage;
• Referral to a multidisciplinary geriatric oncology consultation;
• Consideration for or planned systemic anticancer treatment;
• Ability to understand and respond to assessment tools (G8 and comprehensive geriatric assessment), with or without caregiver assistance;
• Provision of written informed consent by the patient or legal representative.

Exclusion Criteria:

• Age <70 years;
• Diagnosis of hematological malignancy (e.g., leukemia, lymphoma, multiple myeloma);
• Severe cognitive impairment precluding completion of assessment tools without available caregiver support;
• Clinical instability or acute condition preventing data collection (e.g., hospitalization for acute complication);
• Refusal to participate or inability to provide informed consent.

Older adults (≥70 years) with solid malignancies referred for multidisciplinary geriatric oncology evaluation and considered for systemic anticancer treatment.