Neutron and photon clonogenic survival curves of two chemotherapy resistant human intermediate-grade non-Hodgkin lymphoma cell lines

Background: The potential role of neutron therapy in the management of inte rmediate-grade non-Hodgkin lymphoma (IGNHL) has not been examined because o f the belief that the anticipated radiobiological effectiveness (RBE) would be uniformly very low. Purpose: To determine the fast neutron RBE for two chemotherapy-resistant I GNHL cell lines. Methods and Materials: Conventional soft agar clonogenic survival curves fo llowing irradiation by Co-60 and fast neutron were established for two IGNH L cell lines. These cell lines, WSU-DECL2 and SK-DHL2B, were found in previ ous studies to be able to repair sublethal damage, and were also resistant to L-Pam and doxorubicin chemotherapy. Results: When the surviving fraction after 2 Gy photon was chosen as the bi ological endpoint, the RBE for WSU-DLCL2 and SK-DHL2B measured 3.34 and 3.0 6. Similarly, when 10% survival was considered, the RBE for these two cell lines measured 2.54 and 2.59. The RBE, as measured by the ratios alpha neut ron/alpha photon, for WSU-DLCL2, SK-DHL2B cell lines are 6.67 and 5.65, res pectively. These results indicate that the RBE for these IGNHL cell lines i s higher than the average RBE for cell lines of other histological types. Conclusion: Fast neutron irradiation may be of potential value in treating selected cases of IGNHL. (C) 1999 Elsevier Science Inc.