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

Abstract

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 90 Yttrium. 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 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. 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. MJ