Utility of Prophylactic Autologous Stem Cell Collection for Patients with Acute Myeloid Leukemia in First Remission.

High-dose therapy and autologous stem cell transplant (SCT) is an option for patients with AML most commonly performed in first complete remission (CR1) or CR2. Stem cell (SC) collection in CR1 typically follows consolidation. SC collection in CR2 is limited by the need to achieve a second remission prior to harvest, and the use of additional induction therapy that may result in marrow toxicity and SC depletion. In addition, a SC product collected in CR2 might be more likely to have leukemia cell contamination that could contribute to subsequent relapse. Prophylactic collection of SC from patients in CR1 who are not imminently going on to SCT may therefore be reasonable and theoretically could improve outcome of SCT in CR2. However, many patients never relapse, and for those who do, alternative options, and the need to achieve a 2nd CR, further limit the chance that these cells will be used. The morbidity and cost of SC collection, and the need for prolonged storage, call into question the practice of routine prophylactic SC harvest. To determine the utility of SC collection in CR1, we identified 67 patients with AML who had autologous SCs collected between 1995 and 2002. Charts were reviewed to assess whether the collection was prophylactic or for immediate use and we reviewed the timing and outcomes of transplant. 61/67 patients had SCs collected in CR1, 5 in CR2, 1 in CR3. 22 had collection for imminent therapeutic use and 45 for potential future use. Among the 22 patients whose cells were collected for planned SCT, cells were collected in CR1 in 17 cases and CR2 in 5 cases. 11 (50%) remain in CR a median of 58 mo (range 4–103) after SCT, and 11 died a median of 11 mo (4 – 28) after SCT. Causes of death were relapse (n=8), transplant related mortality (TRM) (n=1), TRM after allogeneic SCT (n=1), and unrelated causes (n=1). Of 17 patients transplanted in CR1, 8 (47%) remain in CR. Of the patients whose cells were both collected and used in CR2, 3/5 remain in remission 8, 53, and 103 mo after SCT and 2 died of relapse 10 and 24 mo after SCT. 5/45 patients whose stem cells were collected prophylactically in CR1 used these cells for SCT in CR2 a median of 16 months (15 – 28) after collection. 2/5 of these patients remain in CR 21 mo and 51 mo and 3 had died of relapsed disease 9–12 mo after SCT. Stem cells remain unused in 40 of these patients and 21 (53%) remain in CR a median of 39 mo (7–98 ) after collection. 15/21 remain in CR without further therapy. 3 patients are currently alive receiving therapy for relapse and therefore may use cells in the future. 6 patients are in CR after allogeneic SCT in CR1 (2), CR2 (3) or untreated relapse (1). 16/40 will never use stored cells. 12 died of disease a median of 10 mo (4–22) after prophylactic SC collection and 4 died from complications of allogeneic SCT in CR1 (3) or CR2 (1). In summary, of the 45 patients with SCs harvested prophylactically in AML CR1, 5/21 (23%) who required further therapy went on to use these cells with 2/5 long-term survivors. Another 24 have done well with initial therapy but remain at risk for relapse and may use SCs in the future. In our experience, prophylactic autologous SC harvest and storage from patients with AML in CR1 remains a reasonable option. Additionally, SCT for AML in CR has resulted in frequent long-term remission at our institution.