Off-Protocol Radiotherapy in Prospective Systemic Therapy Trials for Metastatic Non-Small Cell Lung Cancer

Radiotherapy is commonly used for patients with metastatic non-small cell lung cancer (NSCLC)-for symptom palliation, or ablation of metastases. Increasing evidence shows that radiotherapy alters the natural history of metastatic NSCLC. Here, we evaluate prospective systemic therapy trials for protocol specifications and documentation of radiation use during and before trial enrollment.

Clinicaltrials.gov was queried for completed, phase II-IV systemic therapy trials for metastatic NSCLC. Trial information was summarized using descriptive statistics. Fisher's exact test and logistic regression were used to assess associations between trial-related factors, radiation allowance, and trial positivity.

A total of 405 trials were screened, and 79 were included. Most trials were phase III (n = 50, 63.3%), randomized (n = 68, 86.1%), and unmasked (n = 56, 70.9%). PD-1/PD-L1, EGFR, and VEGF were the most common drug targets, in 46.9% (n = 37), 34.2% (n = 27), and 15.2% (n = 12) of studies, respectively. Most studies (n = 74, 93.7%) allowed radiation before trial enrollment and required a washout period. During the study period, 8.9% (n = 7) of studies prohibited ("off-protocol") radiation. A drug washout around radiation delivery was required in 21.5% (n = 17) of studies. No studies permitting off-protocol radiation addressed allowable total dose, fractionation, technique or organ-at-risk constraints. Allowance of off-protocol radiation was not significantly associated with trial positivity (OR 0.23; 95% CI, 0.01-1.49; P = .19). While pre-enrollment radiation was reported in 32.9% (n = 26) of studies, no study reported off-protocol radiation use or adjusted for it during outcome analyses.

Among prospective systemic therapy trials for NSCLC, radiation details are inconsistently reported. Given overlapping toxicities and the common use of radiotherapy in this setting, future trials require clear parameters regarding radiotherapy use before and during trial enrollment.