Background
Leading clinical groups and international guidelines recommend the increased use of radical radiotherapy (RR) as curative-intent treatment in early-stage (ES) and locally advanced (LA) lung cancer (LC) (Stage I-III, non-metastatic). Rapidly evolving diagnostic pathways and radiotherapy technology have enabled greater number of patients with treatable, localised disease to be detected and to receive RR safely. However, the use of RR for LC patients varies widely internationally, due to differences in clinical decision-making and inequitable RR resource allocation. While lung cancer survival has improved in many countries in recent years , the direct contribution of RR to these improvements has not been examined at population-level.
 
Objectives
Using population-based national cancer registry data from a UK nation, securely linked with individual patient-level clinical and patient data, over a 12-year period between 2010 and 2021 this study
(1)          Describes trends in treatment and survival outcomes of non-metastatic LC patients in Northern Ireland by demographics, tumour characteristics and treatment modalities.
(2)          Investigates the impact of changes in RR use for non-metastatic (Stage I to III) LC patients, alongside associated treatments, on survival outcomes, adjusting for key patient, clinical and tumour factors.
 
Methods
A large, national,   population-based dataset of Northern Ireland patients diagnosed with Stage I to III (non-metastatic) primary lung cancer between 1st January 2010 and 31st December 2021 were included.  These were linked with patient-level clinical information from regional LC multidisciplinary meetings  and a radiotherapy clinical database. Stage IV (metastatic) LC patients were excluded.  A stepwise Weibull multivariate model for the association between RR and cause-specific survival was built, included adjustment for non-RR treatment pathways and pertinent tumour- and patient-related factors including (1) period of diagnosis (2) sex, age and co-morbidity (Charlson co-morbidity score (CCS), ECOG performance status (PS) and Forced Expiratory Volume in 1 second (FEV1) (3) stage and histology (4) surgery and systemic therapy (5) radiotherapy administration (6) radiotherapy dose.
key patient-level variables used in clinical decision-making about suitability for RR, were also recorded
 
Results 
Complete records were available for 5882 patients. RR use increased from 17% (272/1644) to 31% (651/2122) between 2010-2013 and 2018-2021 coincident with a 5-year cause-specific survival increase from 22% to 33% over the same period. Palliative radiotherapy reduced from 34% (561/1644) to 14% (302/2122) over the same period, with the proportion receiving surgery relatively stable [24% (396/1644) in 2010-2013 and 21% (435/2122) in 2018-2021]. Adjusted hazard ratios, modelled using a Weibull distribution, for 2018-2021 compared to 2010-2010, with and without radiotherapy included were 0.67 (95% CI: 0.61-0.72) and 0.78 (95% CI: 0.72-0.85) respectively, indicating that increasing RR use was the strongest and most significant contributor to survival improvement over the period and more than surgery or chemotherapy.
 
Conclusions/Implications for practice and policy
RR usage is increasing and accounted for improved outcomes more than other changes in the lung cancer service in the same time period. These population-level data support prioritisation and expansion of RR utilisation for a wider range of LC patients to improve outcomes.