Evaluation of different biomarkers to predict individual radiosensitivity in an inter-laboratory comparison--lessons for future studies.

Radiotherapy is a powerful cure for several types of solid tumours, but its application is often limited because of severe side effects in individual patients. With the aim to find biomarkers capable of predicting normal tissue side reactions we analysed the radiation responses of cells from individual head and neck tumour and breast cancer patients of different clinical radiosensitivity in a multicentric study. Multiple parameters of cellular radiosensitivity were analysed in coded samples of peripheral blood lymphocytes (PBLs) and derived lymphoblastoid cell lines (LCLs) from 15 clinical radio-hypersensitive tumour patients and compared to age- and sex-matched non-radiosensitive patient controls and 15 lymphoblastoid cell lines from age- and sex- matched healthy controls of the KORA study. Experimental parameters included ionizing radiation (IR)-induced cell death (AnnexinV), induction and repair of DNA strand breaks (Comet assay), induction of yH2AX foci (as a result of DNA double strand breaks), and whole genome expression analyses. Considerable inter-individual differences in IR-induced DNA strand breaks and their repair and/or cell death could be detected in primary and immortalised cells with the applied assays. The group of clinically radiosensitive patients was not unequivocally distinguishable from normal responding patients nor were individual overreacting patients in the test system unambiguously identified by two different laboratories. Thus, the in vitro test systems investigated here seem not to be appropriate for a general prediction of clinical reactions during or after radiotherapy due to the experimental variability compared to the small effect of radiation sensitivity. Genome-wide expression analysis however revealed a set of 67 marker genes which were differentially induced 6 h after in vitro-irradiation in lymphocytes from radio-hypersensitive and non-radiosensitive patients. These results warrant future validation in larger cohorts in order to determine parameters potentially predictive for clinical radiosensitivity.

Dose-dense induction with sequential high-dose cytarabine and mitoxantone (S-HAM) and pegfilgrastim results in a high efficacy and a short duration of critical neutropenia in de novo acute myeloid leukemia: a pilot study of the AMLCG.

Dose density during early induction has been demonstrated to be one of the prime determinants for treatment efficacy in acute myeloid leukemia (AML). The German AML Cooperative Group has therefore piloted a dose-dense induction regimen sequential high-dose AraC and mitoxantrone followed by pegfilgrastim (S-HAM) in which 2 induction cycles are applied over 11 to 12 days instead of 25 to 29 days as used in conventional double induction, thereby increasing dose density 2-fold. Of 172 de novo AML patients (excluding acute promyelocytic leukemia), 61% reached a complete remission, 22% a complete remission with incomplete peripheral recovery, 7% had persistent leukemia, 10% died (early death) resulting in an overall response rate of 83%. Kaplan-Meier estimated survival at 2 years was 61% for the whole group (patients with unfavorable karyotypes, 38%; patients with favorable karyotypes, 69%; patients with intermediate karyotypes, 75%) after S-HAM treatment. Importantly, the compression of the 2 induction cycles into the first 11 to 12 days of treatment was beneficial for normal hematopoiesis as demonstrated by a significantly shortened duration of critical neutropenia of 31 days compared with 46 days after conventionally timed double induction.