Delivered relative dose intensity in adolescent and young adult germ cell tumours in England: Assessment of data quality and consistency from clinical trials compared to national cancer registration data

Adolescent and young adults (AYA) with germ cell tumours (GCT) have poorer survival rates than children and many older adults with the same cancers. There are several likely contributing factors to this, including the treatment received. The prognostic benefit of intended dose intensity is well documented in GCT from trials comparing regimens. However, evidence specific to AYA is limited by poor recruitment of AYA to trials and dose delivery outside trials not being well examined. We examined the utility of cancer registration data and a clinical trials dataset to investigate the delivery of relative dose intensity (RDI) in routine National Health Service practice in England, compared to within international clinical trials. Linked data from the Cancer Outcomes and Services Dataset (COSD) and the Systemic Anti-Cancer Therapy (SACT) dataset, and data from four international clinical trials were analysed. Survival over time was described using Kaplan-Meier estimation; overall, by age category, International Germ-Cell Cancer Collaborative Group (IGCCCG) classification, stage, tumour subtype, primary site, ethnicity and deprivation. Cox regression models were used to determine the fully adjusted effect of RDI on mortality risk. The quality of both datasets was critically evaluated and clinically enhanced. RDI was found to be well maintained in all datasets with higher RDIs associated with improved survival outcomes. Real-world data demonstrated several strengths, including population coverage and inclusion of sociodemographic variables and comorbidity. It is limited in GCT however, by the poor completion of data items enabling risk classification of patients and a higher proportion of missing data.