Prognostic Factors after Nonmyeloablative Allogeneic Stem Transplantation (NST) in Chronic Lymphocytic Leukemia (CLL): Expression of P53 May Not Predict Survival.

The abnormal expression of P53 is prognostically important in patients (pts) with CLL treated with conventional chemotherapy. In order to determine its significance upon survival in CLL pts undergoing NST, we analyzed outcome of P53 expression in conjunction with clinical and laboratory parameters in 86 pts transplanted at the MD Anderson Cancer Center between 02/96 and 01/06. Pts were eligible if they had failed conventional chemotherapy and had an HLA-identical or one-antigen mismatched donor.

<<Patient Characteristics>> Median age (range) was 58 (36–73), the majority (81.4%) were males and the median Hematopoietic Stem Cell Transplantation (HSCT) Co-morbidity score was 3 (range 0–8). Pts were heavily pretreated with advanced disease at time of transplant: 66% had 3 or more lines of chemotherapy regimens, 41 (48%) had failed alemtuzumab, 55/65 (85%) had Binet stage B/C, 19(22%) had experienced transformation to Richter’s, 31 (36%) had progressive disease, and 22 (33%) were gallium/PET positive. Twenty-eight of 39 pts (72%) tested had unmutated IgVH. Immunoglobulin (Ig) G, A and M were below normal in 68%, 78% and 50%, respectively. CD4 and CD8 levels were <100 in 26% and 32% of pts, respectively. Median time (range) from diagnosis to NST was 62.3 (6.5–306.6) months. Donors were matched siblings in 43 pts (50%), matched unrelated in 35 pts (40.7%), mismatched unrelated in 2 pts (2.3%), mismatched related in 4 pts (4.7%) and 2 pts (2.3%) from other family members. The source of graft was peripheral blood in 71% of pts, with a median dose of 4.8x10⁶/Kg CD34+ cells infused. Median donor age was 49 (14–77.6) years. Pts and donors were sex-, or ABO-mismatched in 50.7% and 36% of cases, respectively. The conditioning regimens consisted of fludarabine(F), cyclophosphamide(C), rituximab (R) in 40 pts (47%), FCR/Zevalin in 12 pts (14%), FCR/Alemtuzumab (30 mg total) in 26 pts (30%), and 8 pts (9%) received FR/Melphalan.

<<P 53 Analysis>> P53 has been commonly tested by FISH methodology. In this report, 37 pts were tested by FISH. As an alternative, immunohistochemistry (IHC) assessing the expression of P53 in the absence of P21 has been suggested as a surrogate for mutated P53 status. IHC was therefore performed using antibodies to P53 (clone DO7; DAKO, Carpinteria, CA), and P21 (clone SX118:BD Pharmingen, San Diego, CA) on paraffin-embedded bone marrow biopsies in 46 pts. Samples were reviewed for expression of P53 and P21 proteins by T.D. and C.B-R., who were blinded as to outcome. Samples were considered positive for P53 mutation only if 20% or more of the malignant cells expressed P53 protein, with less than 5% expressing P21 protein.

<<RESULTS>> Thirteen of 46 pts (28%) were tested positive for P53+/P21− by IHC, and 10 of 37 (27%) were FISH+. Twenty-one pts were tested by both IHC and FISH: results were concordant in 16 pts (76%); 3 pts were FISH+/IHC−; 2 pts were FISH−/IHC+.

<<Clinical outcome>> With a median follow-up time for surviving pts of 37 (range, 12–131) months, the estimated three-year survival of all 86 pts was 53%. Univariate Cox proportional hazards regression for OS that considered P53 results as well all other clinical variables described above showed that IgG level below normal range at transplantation (P=0.001), CD4 <100 (P=0.005), acute grade III–IV GVHD (P=0.004), # prior chemotherapy regimens >=3 (P=0.023), Richter’s transformation (P=0.038), and % lymphocytes in marrow (P=0.039) were significantly associated with time to death. A multivariate analysis that included all the covariates with P values <0.05 was conducted. This analysis showed the IgG level to be the only significant factor (P=0.033) while CD4 level approached significance (P=0.05). Neither P53 mutation {either by IHC (P= 0.51), or FISH (P=0.95)} nor the HSCT Comorbidity score (P= 0.22) were found to be predictors of survival.

<<Conclusions>> NST may overcome the negative predictor significance of P53 mutation. Considering the poor outcome with conventional chemotherapy, these pts may be considered for NST early in the course of their disease, before experiencing further depletion of their immune system as reflected by IgG and CD4 levels.