Introduction. Loneliness is a negative subjective experience linked to adverse physical and psychological outcomes. In oncology, it may act as a psychosocial risk factor affecting quality of life, coping, and survival. The Cancer Loneliness Scale (CLS) is the only instrument specifically developed to assess cancer-related loneliness, but it has not been validated in Spanish-speaking populations.


Purpose. This study aimed to validate the CLS in Colombian cancer patients to provide a reliable tool for assessing loneliness in this context.


Method. A prospective validation study was conducted with 500 adult patients diagnosed with breast, prostate, cervical, gastrointestinal, or hematological cancers at the National Cancer Institute in Colombia. Psychometric properties were assessed using Classical Test Theory (internal consistency, test-retest reliability, construct, concurrent, divergent, and discriminant validity) and Item Response Theory (Rasch model).


Results. The CLS demonstrated a unidimensional structure (CFA: χ²/df = 1.924; CFI = 0.984; TLI = 0.977; RMSEA = 0.061). Internal consistency was high (α = 0.88; ω = 0.91; GLB = 0.84). Test-retest reliability was strong (Lin's coefficient = 0.92; p < 0.001). The CLS correlated positively with the UCLA Loneliness Scale (ρ = 0.75; p < 0.001) and negatively with the FACIT-G and its domains (ρ = -0.40 to -0.55; p < 0.001). No significant correlation was found with the Charlson Comorbidity Index. Rasch analysis confirmed unidimensionality, appropriate item fit (MNSQ 0.78-1.19), and reliability for items (0.98) and persons (0.70). The Wright map indicated that the scale more effectively captured moderate-to-high levels of loneliness, with limited sensitivity at very low levels and overlap between some items.


Conclusions. The Colombian version of the CLS showed robust psychometric properties, supporting its validity and reliability for measuring loneliness in cancer patients. Its use may facilitate the identification of psychosocial risk and inform interventions that contribute to improved health outcomes and reduced inequalities in oncology care.