Viral reactivation as a cause of unexplained fever in patients with progressive metastatic breast cancer.

Patients suffering from metastatic breast cancer and recurrent fever were investigated for viral reactivation or new viral infection as a possible cause of these febrile episodes. Three groups of patients were included in the study: (a) patients under adjuvant chemotherapy with cyclophosphamide, methotrexate and fluoruracil, (b) patients with stable metastatic disease treated with cyclophosphamide, fluoruracil and Adriamycin or mitoxantrone and (c) patients with progressive metastatic disease who also received the latter treatment. During the time of observation, patients under adjuvant chemotherapy did not present with fever or asymptomatic viral reactivation or bacterial infections at all. Out of 7 patients with stable disease, 2 had bacterial infections that coincided with the leukocyte nadir, and 1 presented with asymptomatic reactivation of cytomegalovirus. In contrast, fever in 9 of 11 patients with progressive disease was associated with a reactivation of herpes simplex virus (HSV) and in 3 of them with a consecutive reactivation of varicella zoster virus (VZV). The increase in complement-fixing anti-HSV or anti-VZV antibodies occurred in close association with a rise of the respective preexisting antibodies of the IgG class. In addition, HSV-infected cells were recovered from the urine of 7 patients with progressive disease further corroborating the serological data. Incidentally, natural killer cell activity, which has been postulated to be connected with the defense against viral infections, was found to be significantly lower in the group of patients with progressive disease, as compared to the group of patients under adjuvant chemotherapy (P less than 0.05) or to the group of patients with stable disease (P less than 0.05). We conclude that unexplained fever in patients with progressive metastatic breast cancer may result from viral reactivation.