Impact of COVID-19 vaccination on radiation-induced lung injury in breast cancer patients: a retrospective cohort study.

[BACKGROUND] The safety of COVID-19 vaccination during radiotherapy remains a concern among oncologists. This study investigates whether vaccination increases the risk of radiation-induced lung injury (RILI) in breast cancer patients.

[METHODS] We retrospectively analyzed 157 breast cancer patients treated with radiotherapy between April 2021 and October 2022. Lung injury was assessed through post-treatment imaging and correlated with COVID-19 vaccination status.

[RESULTS] Of 157 patients, 70 (44%) developed radiologic signs of radiation induced lung injury. Most patients (85%) were vaccinated. Statistical analysis revealed no significant association between vaccination status and injury risk (Chi-square p = 0.3569; logistic regression p = 0.646, OR = 1.063, 95% CI: 0.821-1.383). A non-significant trend toward reduced injury was noted in the two-dose subgroup.

[CONCLUSION] The findings of this study indicate that the administration of the COVID-19 vaccine prior to the commencement of radiation therapy is not associated with an increased likelihood of pulmonary toxicity. Although a slight protective effect was observed with two vaccine doses, it was not statistically significant. The retrospective nature of the study and the limited sample size necessitate the execution of larger, prospective, long-term follow-up studies to elucidate the underlying immunological mechanisms.