Spontaneous Dramatic Regression of Clear Cell Renal Cell Carcinoma After Pazopanib-Induced Severe Systemic Inflammatory Syndrome: A Case Report and Literature Review

Abstract

Renal cell carcinoma (RCC) is the most common type of kidney cancer, accounting for a significant proportion of all cancer cases in Korea. This case report presents a unique instance of spontaneous dramatic tumor regression in a 42-year-old Korean male diagnosed with clear cell RCC. The patient initially presented with right lower back pain, weight loss, and a loss of appetite. Following systemic immunotherapy with nivolumab and ipilimumab, and right radical nephrectomy, the patient was diagnosed with metastatic clear cell RCC, with new metastatic lesions detected in the liver, and on the chest wall on follow-up imaging. Second-line systemic treatment with pazopanib was initiated. Shortly thereafter, the patient developed severe systemic inflammatory syndrome, resulting in a mental stupor and acute kidney failure. Intensive care, including continuous renal replacement therapy and high-dose immunosuppressants, was administered. The patient's condition improved significantly with the intensive care regimen, leading to unintended tumor regression. These potentially fatal side effects occurred without infection, as confirmed by negative blood and urine cultures, and were attributed to the recent introduction of pazopanib. Follow-up imaging showed a significant reduction in hepatic metastatic lesions and the disappearance of chest wall nodules. This is the first reported case of RCC tumor regression following the side effects of pazopanib, underscoring the need for further studies into the immune mechanisms involved in RCC treatment and highlighting potential therapeutic strategies that leverage innate immune responses.

Keywords: inflammatory syndrome; pazopanib; renal cell carcinoma; spontaneous tumor regression.

Figure 1

(A) Erect view of abdominal radiography showing a mass-like opacity in the right abdomen. (B) Contrast-enhanced abdominal computed tomography revealing a heterogeneous enhancing mass occupying the right kidney, with nephromegaly measuring 19.1 cm in length. The mass extends into the pelvicalyceal system and proximal ureter and is associated with tumor thrombosis in the right renal vein, infra-diaphragmatic inferior vena cava, and at the branching site of the left renal vein. (C) Axial view of positron emission tomography/computed tomography (PET/CT) of the torso, showing a large hypermetabolic lesion in the right kidney with a maximum standardized uptake value (SUV) of 13.3 (consistent with renal cell carcinoma and involving the proximal ureter.

Figure 2

(A) Contrast-enhanced chest computed tomography revealing the appearance of new and gradually enlarging small nodules (yellow arrows) in the left anterior chest wall, suggestive of metastasis. (B) Follow-up chest computed tomography demonstrating the disappearance of these nodules.

Figure 3

(A) Dynamic contrast-enhanced magnetic resonance imaging (MRI) of the liver showing a rim-enhancing mass (yellow arrow) in the subcapsular area of segment 7 (S7) with peritumoral hyperemic and edematous parenchymal changes, diffusion restriction, and internal linear hypointense foci on T1-weighted and T2-weighted images with signal drop at the in-phase sequence. (B) Follow-up MRI revealing a decreased remnant metastatic lesion (yellow arrow) in the posterior margin of S7 with uncertain viability.