What happened, in summary

This 62-year-old Taiwanese woman had a history of right Stage IIB triple-negative breast cancer, with ER-negative, PR-negative, and HER2-negative biomarkers. Ten years earlier, she had undergone right modified radical mastectomy, neoadjuvant chemotherapy, and postoperative radiotherapy. Her breast cancer later recurred with lung metastasis. Over the next 2 years, the metastatic disease was refractory to 4 chemotherapy lines: capecitabine, eribulin mesylate, paclitaxel plus gemcitabine, and carboplatin plus gemcitabine. Because treatment options were limited, she started sacituzumab govitecan at 10 mg/kg. She had no major symptoms after cycle 1, but after cycle 2 she developed shortness of breath, dry cough, and diarrhea. Two weeks later, she came to the emergency room in acute respiratory distress, with oxygen saturation of 82% on room air. Chest imaging showed worsening bilateral infiltrates and diffuse ground-glass opacities. Testing for atypical infections was negative, and no other clear cause was found. Her team diagnosed grade 3 sacituzumab-govitecan-induced interstitial pneumonitis. The drug was stopped, oxygen support was escalated, and she received methylprednisolone 40 mg twice daily, equivalent to about 2 mg/kg/day of prednisolone. After 1 week, her breathing and chest X-ray findings improved markedly, and steroids were tapered over 1 month. Because of the limited choices for metastatic triple-negative disease, she accepted a rechallenge at half dose, 5 mg/kg. She received 4 more cycles without recurrent pneumonitis. However, follow-up CT later showed disease progression, with one new pulmonary metastasis and enlargement of prior lung metastases. Her progression-free survival on sacituzumab govitecan was 5.37 months.