Small-Cell Lung Cancer Presenting as Hypercalcemia

Hypercalcemia of malignancy is a common and life-threatening complication in cancer patients, typically seen in advanced breast cancer, multiple myeloma, and non-small-cell lung cancer. In contrast, it is rare in small-cell lung carcinoma (SCLC), where parathyroid hormone levels remain mostly within the normal range despite elevated calcium. We present a case of hypercalcemia in a patient with SCLC and discuss its clinical implications. A 67-year-old male with a significant smoking history and a history of hypertension and atrial fibrillation presented with symptoms, including nausea, vomiting, fatigue, weight loss, excessive thirst, and pleuritic chest pain. Laboratory tests revealed elevated calcium levels (12.2 mg/dL) and signs of organ involvement. Imaging studies suggested metastatic disease, and a liver biopsy confirmed a metastatic neuroendocrine tumor consistent with SCLC. Further investigation showed suppressed parathyroid hormone and low parathyroid hormone-related peptide levels. Lytic bone lesions were not identified on imaging. Despite hydration therapy, the patient's hypercalcemia was refractory, and intravenous zoledronic acid was initiated, improving his encephalopathy. He chose comfort measures and passed away several days later. The patient's hypercalcemia was refractory to hydration, and bisphosphonate therapy was initiated with partial improvement. Despite treatment, the patient's prognosis remained poor, and he transitioned to palliative care. Hypercalcemia in SCLC, though rare, often indicates a poor prognosis and may be related to mechanisms such as cytokine production or bone marrow involvement. The management of hypercalcemia requires rapid intervention, primarily through intravenous hydration. Bisphosphonates and other adjunct therapies may be necessary for refractory cases. Early palliative care discussions are essential, as these patients typically have a limited life expectancy.