Abstract
BACKGROUND: Pneumonitis is a possible side effect of radiotherapy for lung cancer. Since it can occur up to several months following treatment, symptoms may not be associated with previous radiotherapy, and pneumonitis can become severe before diagnosed. This study aimed to develop a symptom-based scoring system to contribute to earlier detection of radiation pneumonitis requiring medical intervention (grade ≥ 2). METHODS: Patients irradiated for lung cancer complete a paper-based questionnaire (symptom-based score) during and up to 24 weeks following radiotherapy. Patients rate symptoms potentially associated with pneumonitis, and scoring points are assigned to severity of these symptoms. Sum scores are used to identify radiation pneumonitis. If radiation pneumonitis is suspected, patients undergo standard diagnostic procedures. If grade ≥ 2 pneumonitis is confirmed, medical intervention is indicated. The discriminative power of the score will be assessed by calculating the area under the receiver operating characteristic curve (AUC). If statistical significance of the AUC is reached, the optimal sum score to predict radiation pneumonitis will be established, which is defined as a cut-off value with sensitivity ≥90% and specificity ≥80%. Assuming a ratio between patients without and with pneumonitis of 3.63, a sample size of 93 patients is required in the full analysis set to yield statistical significance at the level of 5% with a power of 90% if the AUC under the alternative hypothesis is at least 0.9. Considering potential drop-outs, 98 patients should be recruited. If > 20% of patients are not satisfied with the score, modification is required. If the dissatisfaction rate is > 40%, the score is considered not useful. In 10 patients, functionality of a mobile application will be tested in addition to the paper-based questionnaire. DISCUSSION: If an optimal cut-off score resulting in sufficiently high sensitivity and specificity can be identified and the development of a symptom-based scoring system is successful, this tool will contribute to better identification of patients experiencing pneumonitis after radiotherapy for lung cancer. TRIAL REGISTRATION: Clinicaltrials.gov ( NCT04335409 ); registered on 2nd of April, 2020.