Development of second primary multiple myeloma five years after treatment for limited-stage small cell lung cancer: a rare case report

Introduction. The development of a second primary malignancy (SPM) following small cell lung cancer (SCLC) has been previously reported in the literature. Especially smoking-related malignancy coupling is well known. The development of multiple myeloma (MM) in long-term survivors after treatment for SCLC is unknown. Here, we report the first case in the literature who developed MM 5 years after treatment for limited-stage SCLC. Case report. A 67-year-old male patient was diagnosed with limited-stage SCLC. After he received chemotherapy and radiotherapy, he was followed up without medication. He was admitted to the hospital with back pain and dyspnea 5 years after the diagnosis of small cell lung cancer. MRI revealed osteolytic lesions in the vertebrae. Laboratory testing revealed a markedly elevated serum IgA and an elevated serum beta-2 microglobulin level. Serum immunofixation revealed IgA lambda-type M-protein. Lambda excretion in urine immunofixation electrophoresis was observed. Bone marrow aspiration revealed the frequency of plasma cells to be 80% of all nucleated cells. Hence, the final diagnosis revealed IgA lambda free light chain MM. Treatment was given for multiple myeloma. In the follow-up, the patient experienced increased dyspnea and developed bilateral pleural effusion. The cytology sent from thoracentesis sampling was reported as plasmocyte-rich material. The patient fell into a coma and died in an intensive care unit. Conclusion. We presented the development of MM 5 years after treatment in a patient with SCLC who were treated for one year and then followed up with stable findings. It should be kept in mind that a patient with SCLC who is a long-term survivor and presents with back pain may have developed a primary malignancy originating from bone marrow rather than a bone metastasis. Patients should be advised smoking cessation after the treatment and diagnosis of SCLC. Also, the patients with SCLC who are long-term survivors should be closely monitored for the development of SPM.