Abstract
RATIONALE: Mutations in the epidermal growth factor receptor (EGFR) gene are highly prevalent in non-small cell lung cancer, while rare in other cancers. Primarily it's hardly present in bone metastases from cancer of unknown primary (BMCUP). Currently, no specific treatment options for bone metastases from unknown primary cancers exist. PATIENT CONCERNS: The right shoulder and back pain of a 72-years-old man had been persistent for 2 weeks and had developed worse on 1 particular day. The right upper arm was compromised, which also hindered the arm's ability to raise and flex, and nighttime sleep was impacted. After applying the analgesic patch externally, the symptoms did not improve. No coughing or sputum production, chest tightness, shortness of breath, acid reflux, belching, abdominal pain, distension, diarrhea, backache, hematuria, black or bloody feces, or other discomforts appeared over the course of the illness. DIAGNOSES: The patient had a particular type of bone metastases from primary cancers with genetic test results indicating EGFR amplification and mutation. INTERVENTIONS: A third-generation tyrosine kinase inhibitors drug, oral Osimertinib 80 mg once a day with bisphosphonates anti-bone destruction treatment was performed on schedule. OUTCOMES: Following treatment, the patient's tumor-related symptoms were significantly improved by controlling the disease for up to 11 months and providing great pain relief. LESSON: EGFR-based genetic testing has emerged as a key measure for targeted therapy in non-small cell lung cancer. However, there are fewer relevant studies for other tumor types like BMCUP. Combined with literature reviews and our report, we provide evidence that targeting EGFR mutations according to the "basket theory" for the treatment of BMCUP is effective.