IN-VITRO RADIATION-INDUCED APOPTOSIS AND EARLY RESPONSE TO LOW-DOSE RADIOTHERAPY IN NON-HODGKINS-LYMPHOMAS

Purpose: Prospective investigation of spontaneous and in vitro radiati on-induced apoptosis to predict early response to palliative radiother apy in patients with non-Hodgkin's lymphomas. Patients and methods: Fi ne-needle sampling was performed in 28 tumor sites (26 patients) and y ielded adequate cell numbers in 27 cases. Apoptotic cells were counted by fluorescence microscopy immediately after sampling and after 24-h culture (spontaneous apoptosis) and 24 h after 2- and 10-Gy in vitro i rradiation (radiation-induced apoptosis). Early response to low-dose i n vivo radiotherapy (mostly 4 Gy in two fractions over 3 days) was eva luated 15 days after treatment. Results: The tumor response rates at 1 5 days were 11 (39%) complete responses, nine (32%) responses of great er than 50% reduction in volume, six (21%) responses of less than 50% reduction in volume and two (7%) cases of no response, Tumors achievin g complete or major response after in vivo irradiation had higher perc entages of apoptotic cells after in vitro irradiation, while no signif icant differences in terms of spontaneous apoptosis were observed betw een responders and non-responders, Conclusion: Spontaneous and in vitr o radiation-induced apoptosis can be easily and quickly assessed on ce lls obtained by fine-needle sampling of non-Hodgkin's lymphoma lesions . The present results suggest that in vitro radiation-induced apoptosi s could be used as a predictive assay of early response to low-dose in vivo irradiation in patients with non-Hodgkin's lymphomas. (C) 1998 E lsevier Science Ireland Ltd.