Successful treatment with anti-programmed-death-1 antibody in a relapsed natural killer/T-cell lymphoma patient with multi-line resistance: a case report

BACKGROUND: Extranodal natural killer/T-cell lymphoma (NKTCL), nasal type, is an aggressive malignancy with poor prognosis. Currently, there is no recommended standard therapy for relapsed NKTCL. CASE PRESENTATION: A 37-year-old woman with lymphadenopathy was diagnosed with NKTCL by biopsy of an enlarged lymph node on the right side of her neck. Enhanced computed tomography revealed no metastasis. For this patient, we performed continuous chemotherapy followed by radiotherapy; however, nodule biopsy showed metastases in her lower limbs 3 months after radiotherapy, which confirmed disease progression. Unfortunately, the patient(’) s temperature was persistently high and her skin ulcers could not be controlled well using multi-line treatment. Therefore, we attempted treatment with the anti-programmed-death-1 (PD-1) antibody, pembrolizumab. Surprisingly, the patient achieved clinical complete remission (CR) after four cycles of pembrolizumab treatment, despite having persistent detectable Epstein-Barr virus (EBV) DNA. Other molecular monitoring techniques were unavailable for this patient owing to the retrospective nature of the study. The only adverse event was soreness of the upper limb joints and muscles. CONCLUSION: This relapsed NKTCL case treated with pembrolizumab showed that multimodal therapy including pembrolizumab would be partially or totally effective for relapsed NKTCL.