Letters to the Editor
2260 contrast to the proposal of Porrata et al., the ALC cannot yet be used as a stratification factor for tumor response and TTP following RIT and should not be used to select patients for such therapy. The potential prognostic role of ALC, and specifically subset analysis of regulatory, cytotoxic and helper T cells, natural killer cells, and indeed the putative role of ADCC more generally in the therapeutic activity of RIT, will need to be clarified in the context of prospective clinical trials.
Time to Progression 100 P = 0.044 80 Proportion
ALC < 1; median 12 Months ALC ≥ 1; median 8 Months
60 40 20 0 0
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36 48 Time (months)
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MJ Bishton1, RJ Hicks2, HM Prince1,3, DS Ritchie1, M Wolf1 and JF Seymour1,3 1 Department of Haematology and Medical Oncology, Peter McCallum Cancer Centre, Melbourne, Australia; 2 Department of Nuclear Medicine, Peter McCallum Cancer Centre, Melbourne, Australia and 3 University of Melbourne, Australia E-mail:
[email protected]
Figure 1 Time to progression by absolute lymphocyte count.
References difference in OS, a small subgroup of these patients with low pre-treatment ALC had prolonged ongoing CR. The reasons for the differences between our cohort and that reported by Porrata et al. are unclear, as is the consideration of whether prior treatment affects outcome, despite both groups including heavily pretreated patients. Possibilities for the differences observed include our use of the chimeric anti-CD20 antibody rituximab for RIT, which is cleared from the circulation at a slower rate than murine antibodies, as well as the use of 131 Iodine as a radioisotope rather than 90Yttrium. However, it is difficult to conceptualize how these minor differences in an otherwise similar treatment modality would result in such a marked divergence in outcome. Both studies are retrospective analyses from single institutions. We would suggest that in
1 Porrata LF, Ristow K, Witzig TE, Tuinistra N, Habermann TM, Inwards DJ et al. Absolute lymphocyte count predicts therapeutic efficacy and survival at the time of radioimmunotherapy in patients with relapsed follicular lymphomas. Leukemia 2007; 21: 2554–2556. 2 Leahy MF, Seymour JF, Hicks RJ, Turner JH. Multicenter phase II clinical study of iodine-131-rituximab radioimmunotherapy in relapsed or refractory indolent non-Hodgkin’s lymphoma. J Clin Oncol 2006; 24: 4418–4425. 3 Maloney DG. Concepts in radiotherapy and immunotherapy: anti-CD20 mechanisms of action and targets. Semin Oncol 2005; 32 (1 Suppl 1): S19–S26. 4 Turner JH, Martindale AA, Boucek J, Claringbold PG, Leahy MF. 131I-Anti CD20 radioimmunotherapy of relapsed or refractory nonHodgkins lymphoma: a phase II clinical trial of a nonmyeloablative dose regimen of chimeric rituximab radiolabeled in a hospital. Cancer Biother Radiopharm 2003; 18: 513–524.
Reply to ‘Claimed association of absolute lymphocyte count with therapeutic efficacy of radio-immunotherapy in patients with indolent lymphoma cannot be verified in an independence data set’ by Mark J Bishton et al
Leukemia (2008) 22, 2260–2261; doi:10.1038/leu.2008.117; published online 15 May 2008
We read with interest the study by Bishton et al.1 evaluating the role of absolute lymphocyte count (ALC) on survival and response rate in a cohort of 35 patients with indolent nonHodgkin lymphoma treated with 131I-rituximab. In contrast to our previous publication,2 Bishton et al. reported an improved time to progression and better likelihood to achieve a complete response in patient with an ALC o1.0 109/l after treated with radio-immunotherapy (RIT). The pressing question based on the study by Bishton and co-workers and our study is if the ALC is the best marker of host immunity affecting survival in patients treated with RIT. The ALC, as a surrogate maker of host immunity has been reported to be a significant factor for survival for different hematological3 and solid tumor malignancies,3 at Leukemia
diagnosis,4 during standard chemotherapy,5 as well as after autologous stem cell transplantation.3 Moreover, ALC is a prognostic factor for survival not only in the adult setting, but also in the pediatric setting.6,7 A limitation of the ALC is that the ALC does not identify the specific lymphocyte subset affecting survival. Besides both studies being retrospective, a major limitation of both studies is the lack of lymphocyte subset analysis to further delineate which lymphocyte analysis might affect survival post-RIT and by which immunological mechanism. Is the ALC lymphocyte subset analysis important? The obvious answer is yes. Recent reports have shown that the ALC at diagnosis in patients with diffuse large B-cell lymphoma is a prognostic factor for survival.8 In the French study (LNH98B3),9 diffuse large B-cell lymphoma patients that at diagnosis had a higher NK cell count, and not the ALC, experienced superior survival compared to those who did not. So that fact that the study by Bishton et al. identified that patient with
Letters to the Editor
an ALC o1.0 109/l tended to do better does not discredit the role of the host immunity in affecting survival in patients treated with RIT, as it might be the possibility that in their low ALC group there was higher NK cells numbers explaining the observed better outcome. Therefore, we agree with the authors that prospective studies are warranted to address these issues.
LF Porrata1, K Ristow1, TE Witzig1, N Tuinistra2, TM Habermann1, DJ Inwards1, SM Ansell1, IN Micallef1, PB Johnston1 and SN Markovic1 1 Division of Hematology/Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA and 2 Department of Nuclear Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA E-mail:
[email protected]
2261 3 4
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References 1 Bishton MJ, Hicks RJ, Prince HM, Ritchie DS, Wolf M, Seymour JF. Claimed association of absolute lymphocyte count with therapeutic efficacy of radio-immunotherapy in patients with indolent lymphoma cannot be verified in an independence data set. Leukemia 2008; e-pub ahead of print 15 May 2008; doi:10.1038/leu.2008.116. 2 Porrata LF, Ristow K, Witzig TE, Tunistra N, Habermann TM, Inwards DJ et al. Absolute lymphocyte count predicts therapeutic efficacy and survival at the time of radioimmunotherapy in
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patients with relapsed follicular lymphomas. Leukemia 2007; 21: 2554–2556. Porrata LF, Markovic SN. Timely reconstitution of immune competence affects clinical outcome following autologous stem cell transplantation. Clin Exp Med 2004; 4: 78–85. Siddiqui M, Ristoe K, Markovic SN, Witzig TE, Habermann TM, Colgan JP et al. Absolute lymphocyte count predicts overall survival in follicular lymphomas. Br J Haematol 2006; 134: 596–601. Behl D, Porrata LF, Markovic SN, Letendre L, Pruthi RK, Hook CC et al. Absolute lymphocyte count recovery after induction chemotherapy predicts superior survival in acute myelogenous leukemia. Leukemia 2006; 20: 29–34. De Angulo G, Hernandez M, Morales-Arias J, Herzog CE, Anderson P, Wolff J et al. Early lymphocyte recovery as a prognostic indicator for high-risk Ewing sarcoma. J Pediatr Hematol/Oncol 2007; 29: 48–52. De Angulo G, Yuen C, Palla SL, Anderson PM, Zweidler-Mckay PA. Absolute lymphocyte count is a novel prognostic indicator in ALL and AML: implication for risk stratification and future studies. Cancer 2008; 112: 407–415. Kim DH, Baek JH, Chae YS, Kim YK, Kim HJ, Park YH et al. Absolute lymphocyte counts predicts response to chemotherapy and survival in diffuse large B-cell lymphoma. Leukemia 2007; 21: 2227–2230. Plonquet A, Haioun C, Jais JP, Debard AL, Salles G, Bene MC et al. Peripheral blood natural killer cell count is associated with clinical outcome in patients with aaIPI 2-3 diffuse large B-cell lymphoma. Ann Oncol 2007; 18: 1209–1215.
Oncolytic virotherapy for multiple myeloma using a tumour-specific double-deleted vaccinia virus
Leukemia (2008) 22, 2261–2264; doi:10.1038/leu.2008.120; published online 29 May 2008
Oncolytic virotherapy is a tumour-specific strategy, in which viruses selectively kill cancer cells, either through targeted alterations in the cancer cell,1,2 viral deletions,3,4 tissue-specific transcriptional control5 or tumour-specific receptors.6,7 Normal cells are generally left intact. Haematologic malignancies such as multiple myeloma (MM) are particularly attractive for this approach as patients generally have less bulky disease and may have immune system dysfunction favouring viral replication. To date, MM has demonstrated pre-clinical responses to oncolytic measles virus,6,7 vesicular stomatitis virus8 and coxsackievirus A21.9 Our lab has previously developed an attenuated, recombinant double-deleted vaccinia virus (VV) that infects, replicates and expresses genes preferentially in rapidly dividing tumour cells.4 We asked whether VV would be an effective oncolytic virus against MM. Initially, fluorescence-activated cell sorting analysis was used to quantitate the percentage of enhanced green fluorescent protein (EGFP)-positive MM cells after infection with an EGFPexpressing VV. All five cells lines were infected (Figure 1a). After 72 h, RPMI8226 was most efficiently infected and U266 was the least efficient. To confirm that VV infection and gene expression in MM cell lines led to oncolysis and cell death, MM cell lines were infected with VV at a multiplicity of infection (MOI) of 1, and MTT assays were performed (Figure 1b). Compared to mockinfected controls (100% viable), all cell lines showed decreased
viability from 17 to 29% at 72 h. To validate the MTT assays, a trypan blue exclusion assay was performed with similar results (Supplementary Figure S1). In vitro oncolysis, as measured by an assay to detect cytopathic effects, was visible by 48 h (Figure 1c) after infection for the majority of cell lines. This was delayed for the U266 and H929 cell lines suggesting that these cell lines are less susceptible to VV-mediated cell killing though both were infected and express EGFP (Figure 1c, bottom panel). As many anti-myeloma therapeutics act through the induction of apoptosis in MM cells, we asked whether VV-mediated cell death was due to a similar mechanism. Annexin V staining was used to quantitate the number of cells undergoing apoptosis. Compared to mock infection alone, VV infection induced apoptosis in four of five cell lines by 72 h (Supplementary Figure S2). The number of necrotic cells was also increased over mock infection. We next evaluated VV-mediated oncolysis in established tumours after systemic delivery. My5 subcutaneous xenograftbearing mice were treated with systemic (intraperitoneal, 109 plaque-forming unit (PFU) per mouse) VV or vehicle control. After treatment with a single dose of VV, the growth of My5 (Figure 2a) xenografts was significantly (Po0.0001) inhibited by the treatment compared to vehicle control. In addition, My5-bearing mice re-treated with a second dose of VV showed further tumour regression. Selected mice underwent fluorescent imaging at various time points after infection with the EGFPexpressing VV. Viral-mediated EGFP expression was minimal 6 days after VV infection, but slowly spread throughout the tumour and peaked 3 weeks post-infection (Figure 2b). Leukemia
