Synchronous EGFR-mutated lung adenocarcinoma and metastatic breast cancer: surgery and adjuvant therapy

What happened, in summary

A 55-year-old woman who had never smoked found a right breast mass in December 2022. Ultrasound showed a 22 x 19 mm right breast nodule, and biopsy confirmed invasive breast cancer. Chest CT also found an irregular 2.3 cm right upper-lobe lung nodule with spiculation and pleural retraction, plus a separate 0.7 cm ground-glass nodule. Brain CT showed no metastasis, and lymph nodes were not enlarged on imaging. The multidisciplinary team favored surgery. On December 20, 2022, she underwent thoracoscopic right upper lung lobectomy with mediastinal lymph node dissection and right modified radical mastectomy. Lung pathology revealed 3 tumor foci: a 2.2 cm invasive lung adenocarcinoma, a 0.8 cm microinvasive lung adenocarcinoma with adjacent metastatic foci of invasive breast cancer, and another 1 cm invasive lung adenocarcinoma. One of 3 parabronchial lymph nodes contained metastasis, and genomic testing of the lung adenocarcinoma showed an EGFR exon 19 deletion. Breast pathology showed a 3 cm invasive carcinoma with metastasis in 1 sentinel lymph node and 1 axillary lymph node. Breast biomarkers were ER 90%, PR 10%, HER2 2+ without amplification, Ki-67 5%, and GATA3-positive. The final diagnoses were lung adenocarcinoma pT3N1M0, Stage IIIA, and breast cancer pT2N1M1, Stage IV, Luminal B subtype. She received 6 cycles of docetaxel plus cyclophosphamide, then maintenance icotinib for lung cancer and letrozole for breast cancer. Follow-up CT on December 26, 2024 showed no recurrence. No grade 2 or higher adverse events occurred during postoperative systemic and maintenance therapy, supporting continued follow-up on treatment.