Diffuse Cystic Lung Disease Noted In A Patient Treated For Breast Invasive Ductal Carcinoma

SESSION TITLE: Fellows Diffuse Lung Disease Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: October 18-21, 2020 INTRODUCTION: A patient with invasive ductal carcinoma, y(m)pT1cN0(i+)M0, was treated with neoadjuvant docetaxel, carboplatin, trastuzumab, and pertuzumab (TCHP) and adjuvant trastuzumab emtansine (T-DM1). During treatment, imaging demonstrated diffuse cystic lung disease (DCLD). Evaluation for an etiology suggests, but does not implicate, chemotherapy toxicity or radiation therapy. CASE PRESENTATION: In February, 2019 a 44 year-old non-smoker without prior medical history was diagnosed with triple-positive breast cancer. She received TCHP followed by a lumpectomy with sentinel lymph node biopsy. In September, 2019 a CT was obtained; we noted diffuse cystic changes. She subsequently received radiation therapy and adjuvant T-DM1. In December, 2019 a CT chest revealed DCLD, progressively worse since September, without associated nodules or ground glass opacities. History, physical exam, laboratory, and bronchoscopic evaluation did not reveal an etiology. In February 2020, she was referred for lung biopsy. The predominant histologic findings were marked small airway injury, subepithelial fibrosis, hypertrophy of the smooth muscles, and segment obliteration of distal bronchioles. The small airway injury was associated with cyst formation and diffuse mild secondary airspace enlargement. DISCUSSION: The differential diagnosis for DCLD is broad (1, 2), and a diagnostic approach is well-described (3). Imaging and histology excluded known causes for cystic lung disease; findings are best explained as a sequela of a diffuse inflammatory process. DCLD is not a known complication of TCHP or T-DM1 (4, 5). To date, there are no described cases implicating either regimen in DCLD. Yet, there is a molecular basis for the injury pattern (1, 2, 6). A case report describes pediatric cystic lung disease secondary to radiation-induced lung injury. While this patient received local radiation therapy, the CT Chest obtained prior to her treatment demonstrated some cystic changes. This argues against radiation therapy as the etiology. CONCLUSIONS: Following an extensive search, an etiology for this patient's DCLD is not apparent. Evaluation for an etiology suggests, but does not implicate, chemotherapy toxicity or radiation therapy. Reference #1: Gupta N, Vassallo R, Wikenheiser-Brokamp KA, et al. Diffuse cystic lung disease: part 1. Am J Respir Crit Care Med 2015;191: 1354 – 1366. Reference #2: Gupta N, Vassallo R, Wikenheiser-Brokamp KA, et al. Diffuse cystic lung disease: part 2. Am J Respir Crit Care Med 2015;192: 17 – 29. Reference #3: Raoof S, Bondalapati P, Vydyula R, et al. Cystic lung diseases: algorithmic approach. Chest 2016;150: 945 – 965. DISCLOSURES: No relevant relationships by William Wadzinski, source=Web Response No relevant relationships by Whittney Warren, source=Web Response