A Herpes simplex virus-1 fatal encephalitis following chemo-radiotherapy, steroids and prophylactic cranial irradiation in a small cell lung cancer patient

Approximately 20-25% of patients with limited small cell lung cancer (SCLC) can be cured with an aggressive approach (chest radiation concomitant with chemotherapy) followed by prophylactic cranial irradiation (PCI) to a total dose of 30-36Gy with 3-2Gy per fraction, five fractions per week. Steroid prophylactic therapy with dexamethasone is usually prescribed during PCI to minimize acute radiation induced brain oedema. This approach may induce an immunosuppressive condition leading to a reactivation of an endogenous latent Herpes simplex virus and severe or fatal acute encephalitis may occur as our report will show. A 55-year-old man affected by locally advanced SCLC was referred to our institution after four cycles of chemotherapy with a good partial remission. Chest radiation started concomitantly with two cycles of chemotherapy followed by PCI 36Gy total dose and dexamethasone 8mg i.m. daily. Fifteen days after PCI completion the patient developed acute neurological symptoms of confusion, cognitive impairment, fever with shaking requiring severe sedation therapy. Twenty-five days later MRI T1 weighted images showed haemorrhagic streaked lines on cortical convolutions of the right cerebral hemisphere and diffuse oedema suggestive of herpetic encephalitis. The DNA consensus test on cerebrospinal fluid (CSF) was positive for Herpes simplex virus 1 infection (HSV-1). A diagnosis of herpetic encephalitis HSV-1 was made. Antiviral therapy with high doses of acyclovir was prescribed but symptoms did not ameliorate leading to a comatose state. The patient died 55 days after the end of PCI. In eligible SCLC patients, PCI is an important part of an aggressive therapeutic approach that improves overall and disease free survival decreasing the risk of relapse in the brain. A primary infection or a reactivation of an endogenous latent HSV in brain parenchyma under steroid therapy concomitant to brain irradiation may compromise these benefits.