Spanish oncology study finds excess weight in 57.8% of cancer patients
Initial results from the FOBEyCAN registry presented in Madrid show that 23.6% of cancer patients have obesity, prompting calls from SEOM oncologists to integrate body composition tracking into clinical care.
FOBEyCAN study findings
The Spanish Society of Medical Oncology (SEOM) presented the initial findings of the FOBEyCAN study on 30 September 2026 during its annual congress in Madrid. Titled "Fotografía de Obesidad y Cáncer en España: análisis de la situación del exceso de peso en pacientes diagnosticados de cáncer", the project was developed by SEOM's Working Group on Obesity, Metabolism, and Cancer. The initiative aims to determine the prevalence of overweight and obesity among cancer patients across Spain. This first analytical cutoff incorporates patient data gathered up to September 2026, encompassing 1,333 individuals treated across 29 medical centers. The mean age of the enrolled patients is 65 years. The initial results establish that 57.8% of patients with a cancer diagnosis carry excess weight, and 23.6% meet the clinical criteria for obesity.
- All patients
- 23.6 %
- Age 60–69
- 30 %
- Women
- 24 %
- Men
- 21 %
Demographic and tumor variations
Weight distributions within the registry vary across patient demographics and tumor types. Obesity was slightly higher among women at 24%, compared to 21% among men. Conversely, total excess weight, which combines overweight and obesity, affected 61% of male patients compared to 55% of female patients. Patients in the age range of 60–69 years recorded the highest rates, with obesity at 30% and excess weight reaching 61%. When categorized by tumor site, obesity proportions exceeded 20% in cancers of the breast, colon, endometrium, ovary, and kidney. Working group coordinator Laura García Estévez described the widespread distribution of weight issues across different oncology specialties.
Our cancer patients have a high rate of excess weight and it is repeated regardless of tumor type: breast, gastrointestinal, lung, genitourinary, gynecological... no cancer escapes this excess weight.
Clinical implications and patient care
García Estévez pointed out that excess weight reaches nearly 60% in lung, breast, and gastrointestinal cancers. Urological cancers showed a 72% excess weight proportion, although she specified that the urological sample size remains very small and precludes final conclusions. Elena Brozos, another member of the working group, stated that the current release provides a broad descriptive baseline while detailed analyses by tumor category proceed. Existing meta-analyses indicate links between obesity, disease relapse rates, and cancer mortality. García Estévez also noted that 80% of female cancer patients gain weight after diagnosis. Biologically, obesity increases insulin and leptin levels, factors that promote inflammation and disease progression. As a result, SEOM advocates for incorporating weight evaluation and body composition assessments directly into comprehensive patient care.
- Men
- 61 %
- Age 60–69
- 61 %
- All patients
- 57.8 %
- Women
- 55 %
The SEOM2026 congress
The findings were delivered as part of the SEOM2026 congress, running in Madrid through 2 October 2026. The event marks the 50th anniversary of the Spanish Society of Medical Oncology and gathers more than 1,800 medical oncologists. The congress agenda includes 237 speakers, 33 scientific sessions, and 583 scientific communications. Topics scheduled for discussion include precision personalized medicine, clinical and translational research, new therapies, artificial intelligence, cancer prevention, hereditary cancer, sustainability, humanization of care, geriatric oncology, continuous care, and medical training.
