In vitro capacity of various cyclooxygenase inhibitors to revert immune suppression caused by radiation therapy for breast cancer.

Radiation therapy triggers blood monocytes to an increased secretion of immunosuppressive prostaglandins (PGs), which in part can explain the post-irradiation impairment of lymphocyte blastogenesis. Since low mitogen responses of lymphocytes in irradiated breast cancer patients is linked to a poor prognosis a clinical trial is planned to examine if treatment with inhibitors of PG-synthesis during irradiation can counteract immunosuppression and increase survival. In the present investigation we have compared nine different inhibitors of PG-synthesis for capacity to enhance phytohemagglutinin responses of blood lymphocytes before and after irradiation for breast cancer. Five of the drugs (aspisol, indomethacin, meclofenamic acid, ketoprofen and diclofenac) enhanced the reactivity to more than 150%. In general, the strongest enhancements were observed in lymphocyte preparations obtained at completion of irradiation when reactivity was most depressed followed by those obtained at one month and before irradiation.