Peripheral blood stem cells are increasingly used to ensure rapid haematological engraftment after myeloablative chemotherapy. After mobilization, progenitor cells in the blood can be enumerated to predict an adequate collection by leukapheresis. The Advia 120 automated counter has an immature cell channel measuring a parameter known as large undifferentiated cells (LUC's), which were quantified to assess their value in refining the timing of apheresis. Data were available from 102 apheresis sessions. Positive correlation was found for peripheral blood CD34+ cells and apheresis counts (r = 0.82, P < 0.0005) but not for total WCC (r = -0.15, P = 0.13) or LUC count (r = 0.12, P = 0.23). Our results indicate that the LUC population in peripheral blood has no relevance to the subsequent CD34 content of the apheresis product and CD34 cell enumeration by flow cytometry is advocated.

4401 Standard therapy for myeloma includes induction therapy followed by high dose melphalan and autograft (HDM/autograft). Safe delivery of HDM requires optimum peripheral blood stem cells (PBSC) as quantitated by CD34 expression. In ability to collect sufficient PBSC is not uncommon and efficacy of subsequent harvest after failed first attemp needs evaluation. In this single centre analysis, 62 patients with myeloma treated at our centre between 1997 and 2009 were analysed to assess the results of second and subsequent harvest and the factors predictive of failure to mobilize CD34 cells more than 2×10^6/kg. 40 patients were male and 22 were females with a median age of 57 yr. (range: 41–68, M:56yr. Vs. F: 58 yr., p=0.6) Before first harvest patients received induction therapy with either VAD (or similar) chemotherapy to maximum response (n=46), thalidomide combination (n=15) or combination (n=2) and only 2 patients had exposure to Melphalan. 49 patients (78%) achieved at least PR with induction therapy. For the first harvest mobilization was attempted with Cyclo/GCSF (n=56), ESHAP (n=5) and GCSF alone (n=1) at a median interval of 38 days from finishing induction (range: 15–535). Median CD34 yield after first attempt was 1.7×10^6/kg (range: 0.04–14.6) in 1 (n=52) or 2 (n=10) collects. 28 patients (45%) achieved yield more than 2. Yield was slightly lower in female patients (1.39 vs. 2.58, p=0.074) but there was no effect of age, type of chemotherapy, response or mobilization regimen. 28 patients had back to back mobilization with either Cyclo/GCSF or ESHAP priming at a median of 35 d from first harvest (range: 11–99) and the median CD34 yield was 1.7(range: 0.03–14.7) in 1(n=19) or 2 (n=9) collects. All other patients had second harvest at a median of 1018 d(range: 25–2246) and 21 had the collection attempted after HDM/Autograft. The median CD34 yield in the entire cohort of 62 patients was 2.4 (range: 0.03–27.2) and this was achieved in 1(n=45) or 2 (n=17) procedures. Patients who had HDM/autograft (n=21) achieved same yields as others (median: 2.8 vs. 2.2, p=0.11) and required similar number of procedures (median: 1, p=0.62). 26/62 patients (42%) achieved more than 2×10^6 yield in second attempt. Rate was lower in HDM group but not statistically significant (28% vs. 51%, p=0.13). 12/62 (19%) had third attempt at harvest at a median of 862 days from second harvest. The median CD34 yield was 2.3 (range: 0.09–4.13) and 6 (50%) achieved yield more than 2×10^6/kg. There was no correlation between CD34 yield in first and subsequent harvests (R^2: 1.2%). Out of 26 patients who did not collect more than 2 in first attempt, only 9 (35%) managed to achieve this yield in second attempts, especially if they had HDM/autograft. This single centre analysis shows that failure to achieve sufficient CD34 cells in first attempt results in low yields in subsequent tries at PBSC mobilization. If this is a predictor of disease behaviour will be analysed. For patients who may be candidates for more than one HDM procedures efforts to increase the yield in first attempt should be tried. Impact of newer drugs on the attempts at subsequent mobilization needs evaluation. Disclosures: No relevant conflicts of interest to declare.

8124 Background: HDCT with autologous stem cell rescue (ASCR) is an established treatment for recurrent Hodgkin and non- Hodgkin lymphoma (HL, NHL) but some of these pts fail to mobilise adequate numbers of CD34+ cells from the peripheral blood (PB). Harvest of bone marrow (BM) stem cells and use of these alone or in combination with PB derived cells is an option but there are concerns about feasibility and outcome. Methods: 29 pts who had HDCT after failed PB stem cell harvest between July 1999 and December 2005 were studied in terms of CD34+ cell yield (PB and BM), transfusion dependence, engraftment and survival. Results: There were 17 males and 12 females (median age 49yrs, range 19–66) with recurrent HL (n=16) or NHL (n=13). All had received at least 2 lines of chemotherapy (10 pts =3) and 7 had received radiotherapy (5 mediastinal, one neck and one abdominal field). Mobilisation of CD34+ cells from PB was attempted using chemotherapy followed by filgrastim. 22 pts proceeded to leukapheresis on the basis of predictive CD34+ counts (median collects 2; range 0–4) with a median total collect of 0.98×106 CD34+cells/kg (range 0.03–1.84). Subsequently, all pts had a BM harvest producing a median collect of 1.63x106 CD34+cells/kg (range 0.45–4.75). 29 pts then received BEAM/CBV followed by re-infusion of PB+BM cells except in 7 pts where only BM cells were available. In 26/29 pts surviving to day 100; total CD34+ cells infused, 2.37×106/kg (range 1.73- 5.0), time to neutrophils >0.5×109/L, 12 days (range 9–23), platelet units transfused, 6 (range 0–24), red cells units transfused 6 (range 0–18) (all medians). 2 pts continued to have red cell transfusions beyond day 100. 3/29 pts died due to severe neutropenia/septicaemia at days 23–25 (treatment related mortality 10.3%); the CD34+ dose received by these pts was 1.97×106/kg in 2 and 1.84×106/kg in 1. Beyond day 100, 9 pts have died from HL/NHL and 2 are lost to follow-up. Conclusions: In patients with HL/NHL who fail to mobilise adequate numbers of CD34+ cells from PB, a BM harvest can produce a combined BM/PB collect capable of producing haemopoeitic reconstitution following HDCT without excessive toxicity. No significant financial relationships to disclose.