Abstract
A 56–year–old woman diagnosed with left breast cancer, as T4bN1M0 stage IIIB (squamous cell carcinoma; ER negative, PgR negative; HER2 3+). Underwent 12 weekly paclitaxel and trastuzumab cycles and achieved partial response (PR). After completion, cycle 12 she was admitted with a 38°C fever, cough, and sore throat 8 days afterward, followed the next day by dyspnea. SpO2 was 93% and bilateral lower lung fields. fine crackling. Chest CT showed ground–glass density with partial infiltrates in bilateral lung fields, and KL–6 had increased to 694 U/mL, yielding a diagnosis of interstitial pneumonitis reguiring steroid pulse therapy. She became afebrile the day after pulse therapy and reported no marked symptoms. Drug–induced interstitial pneumonitis was suspected and a drug lymphocyte stimulation test for paclitaxel and trastuzumab, showed negative results. Total mastectomy with axillary lymph node dissection was done on day 23 after admission. Postoperative trastuzumab was cautiously reinstituted with no recurrent interstitial pneumonitis, resulting in paclitaxel being considered causally related.
