Treatment of relapsed Wilms tumour (WT) patients: experience with topotecan. A report from the SIOP Renal Tumour Study Group (RTSG)

BACKGROUND

Topotecan has been variably incorporated in the treatment of patients with relapsed Wilms tumour (WT) who failed initial treatment with three or more effective drugs. Our objective was to describe outcome and to retrospectively investigate the potential role of topotecan in relapsed WT patients.

METHODS

Children who were treated with topotecan as part of their chemotherapeutic regimens for relapsed WT were identified and included in our retrospective study. Patient charts were reviewed for general patient characteristics, histology and stage at initial diagnosis, number and type of relapse, salvage treatment schedules, toxicity, response to treatment and outcome.

RESULTS

From 2000 to 2012, 30 children (median age at relapse 5.5 years, range 1.6-14.5 years) were identified to have received topotecan as part of their salvage regimens (primary progressive disease n = 3, first, second and third relapse n = 13, 9 and 2 respectively, partial response n = 3). Topotecan was administered as a single agent (12 patients) or in combination with other drugs (18 patients). Sixteen patients had high-risk histology according to the SIOP classification, 15 died within 12 months because of progressive disease. Fourteen patients had SIOP intermediate-risk histology of which four patients displayed objective responses to topotecan. Overall, 6 out of 14 intermediate-risk patients survived (median follow up of 6 years), however, three of whom (stage V) had bilateral nephrectomy after topotecan treatment.

CONCLUSIONS

Topotecan does not seem to show effectiveness in the treatment of relapsed WT patients with initial high-risk histology. In patients with intermediate-risk histology, the role of topotecan might deserve further attention, to prove its efficacy.

HBO and the uptake and retention of [125I] MIBG in human platelets and two neuroendocrine cell lines

In this paper we report the effects of Hyperbaric Oxygen (HBO) exposure on the uptake and retention of meta-Iodobenzylguanidine (MIBG) in human platelets and two neuroendocrine cell lines. The combination of [131I] MIBG and HBO is used for therapy of neuroblastoma. Exposure to HBO can cause oxidative stress, which is potentially capable of affecting uptake and storage of MIBG in both neuroendocrine cells and platelets. Oxidative stress generated by menadione decreased both the uptake and retention of MIBG in the platelets and the cell lines. HBO did not affect these processes, indicating that the HBO induced oxidative stress is not high enough to affect the MIBG uptake and storage pathways in these cells. This suggests that the positive effects observed by the treatment of neuroblastoma patients with the combination of HBO and [131I] MIBG are most likely not due to improved uptake or retention of MIBG in the neuroblastoma. Neither can reduced cytotoxicity (trombocytopenia) be expected due to decreased uptake/retention of [131I] MIBG in platelets or their precursor cells.

Menadione inhibits MIBG uptake in two neuroendocrine cell lines

In this paper we report on our studies of the effect of menadione on the uptake of MIBG in the neuroendocrine cell lines PC12 and SK-N-SH. Menadione inhibits the uptake of MIBG in both cell lines in a dose-dependent manner. Inhibition of MIBG uptake is most pronounced in the PC12 cell line. Comparison of the inhibitory action of menadione on the uptake and retention of MIBG with that of imipramine and reserpine suggests that menadione inhibits uptake 1 mediated uptake as well as granular storage.

Meta-iodobenzylguanidine uptake in platelets, megakaryoblastic leukaemia cell lines MKPL-1 and CHRF-28-11 and erythroleukaemic cell line HEL

The major toxicity encountered with [131I]-Meta-iodobenzylguanidine (MIBG) therapy in neuroblastoma patients is an often isolated thrombocytopenia. We believe that this results from MIBG-induced radiotoxicity of the megakaryocytes. Since it is difficult to obtain enough human megakaryocytes for uptake studies, we investigated whether the megakaryocytic cell lines, MKPL-1, CHRF-288-11 and HEL, are good models to study serotonin and MIBG accumulation in human megakaryocytes. Compared with platelets, low levels of specific MIBG accumulation (imipramine-sensitive) were shown in all cell lines, but that of serotonin was negligible in MKPL-1 and CHRF-288-11. Furthermore, the proportion of specific uptake of both MIBG and serotonin appeared greatest in the HEL cells. Although these cells seem to be good candidates to study serotonin and MIBG uptake, they are not a good model to investigate MIBG and serotonin accumulation in human megakaryocytes since they have no functional storage granules.

Uptake of the neuron-blocking agent meta-iodobenzylguanidine and serotonin by human platelets and neuro-adrenergic tumour cells

The adrenomedulla-imaging agent meta-iodobenzylguanidine (MIBG) is concentrated by various tumours of neuroectodermal origin. Radio-iodinated [131I]MIBG is therefore increasingly used for diagnosis and therapy of these disorders. To study the cause of thrombocytopenia associated with [131I]MIBG therapy, we investigated the uptake of MIBG in human platelets in comparison with that of serotonin. Specific imipramine-sensitive uptake of [131I]MIBG was much slower than of [3H]serotonin, but after prolonged incubation high and serotonin-equivalent uptake levels were observed. Accumulation of MIBG saturated at 10- to 100-fold higher concentration than serotonin, and the affinity for uptake and intracellular storage in platelets was much higher for serotonin than for MIBG. Conversely, serotonin was not detectably concentrated by neuroadrenergic Uptake-I in SK-N-SH neuroblastoma and PC12 pheochromocytoma cells. Fluvoxamine inhibited the uptake of norepinephrine and MIBG in PC12 cells, similarly to that of serotonin in platelets. However, the drug was 100-fold more effective in inhibiting platelet transport of MIBG than of serotonin. The results indicate that MIBG uptake in platelets is not mediated by a neuro-adrenergic Uptake-I, but probably proceeds via the serotonin transport system. MIBG concentration by platelets was at least as efficient as in neuro-adrenergic tumour cells and has therefore (radio)biological potential for injuring these cells or precursor megakaryocytes. Platelet uptake of MIBG could be selectively blocked by fluvoxamine in concentrations which minimally affected its accumulation in neuro-adrenergic target cells.