Telomere length in breast cancer patients before and after chemotherapy with or without stem cell transplantation.

High-dose chemotherapy and peripheral blood stem cell transplantation (PBSCT) may accelerate telomere length loss in haematopoietic stem cells. As data including pre-and post-treatment samples are lacking, we studied leukocyte telomere length and telomerase activity before and after treatment in breast cancer patients randomized to receive 5 adjuvant courses FEC (5-FU, epirubicin and cyclophosphamide) (n = 17), or 4 x FEC followed by high-dose cyclophosphamide, thiotepa, carboplatin and autologous PBSCT (n = 16). Haemoglobin, MCV, leukocyte-and platelet numbers were assessed prior to (t(0)), 5 months after (t(1)) and 9 months after chemotherapy (t(2)); these parameters were decreased at t(1)and t(2)compared to t(0)(high-dose: all parameters; standard-dose: leukocytes and platelets), and all parameters were lower after high-dose than standard-dose treatment at t(1). Paired individual leukocyte samples of t(0)and t(1)showed telomere length change (determined by telomere restricted fragment (TRF) assay) ranging from +0.8 to -2.2 kb, with a decreased TRF length in 9 patients of both groups. Telomerase activity (determined by TRAP assay) was below detection limit in leukocyte samples of t(0)and t(1). Thus, standard-and high-dose chemotherapy negatively affect haematological reconstitution in this setting. In individual patients, telomere length can be remarkably changed following haematological proliferative stress after treatment.