Tumor lysis syndrome followed by tumor regression after COVID-19 in a patient with chronic lymphocytic leukemia.

Coronavirus disease 2019 (COVID-19) can become lethal in patients with hematological malignancies; however, several cases of tumor regression after COVID-19 have been described, and the precise mechanism behind this paradoxical effect is unknown. Herein, we describe a case of Tumor lysis syndrome (TLS) followed by tumor regression after COVID-19. A 72-year-old woman with untreated chronic lymphocytic leukemia was admitted to our hospital with SARS-CoV-2 antigen-positive pneumonia. On admission, her anti-SARS-CoV-2 spike antibody was negative despite receiving two prior vaccinations. Immediately after admission, she developed confusion and ventricular tachycardia. Laboratory data showed acidosis, hyperkalemia, and a rapid decrease of tumor cells in peripheral blood, and she was diagnosed with clinical TLS. She was transferred to the intensive care unit and received continuous hemodialysis therapy. Although hyperferritinemia and bicytopenia, which suggest a cytokine storm followed, she recovered without steroids and additional COVID-19 treatment in 8 days. 2 months later, CT revealed a marked shrinking of lymphadenopathy, which was compatible with tumor regression after COVID-19. Considering the impaired humoral immunity and abrupt response, direct oncolysis caused by SARS-CoV-2 and cytokine storm-induced cell-mediated immune reaction may have been responsible for this paradoxical effect.