Radiation Pneumonitis in Breast Cancer Patients With Pre-existing Subpleural Curvilinear Lines Following Postoperative Radiation Therapy: 2 Cases

<h2>Abstract</h2> This report describes two breast cancer patients with subpleural curvilinear lines (SCLs), a potential marker for interstitial lung disease (ILD), who developed radiation pneumonitis (RP) after radiotherapy. We present one case of asymptomatic, out-of-field organizing pneumonia (OP) and another of severe RP requiring steroids and treatment interruption. These cases suggest SCLs may signal an increased RP risk, representing the first report of this association in breast cancer. Although causality is not established and SCLs are not specific to ILD, these findings emphasize the need to carefully evaluate baseline interstitial changes on planning CT scans.