Current treatment strategies in follicular lymphomas

High-dose therapy with autologous stem cell transplantation versus chemotherapy or immuno-chemotherapy for follicular lymphoma in adults

BACKGROUND

Follicular lymphoma (FL) is the most common indolent and second most common Non-Hodgkin`s lymphoma (NHL) in the Western world. Standard treatment usually includes rituximab and chemotherapy. High-dose therapy (HDT) followed by autologous stem cell transplantation (ASCT) is an option for patients in advanced stages or for second-line therapy, leading to improved progression-free survival (PFS) rates. However, the impact of HDT and ASCT remains unclear, as there are hints of an increased risk of second cancers.

OBJECTIVES

We performed a systematic review with meta-analysis of randomised controlled trials (RCTs) comparing HDT plus ASCT with chemotherapy or immuno-chemotherapy in patients with FL with respect to overall survival (OS), PFS, treatment-related mortality (TRM), adverse events and secondary malignancies.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and EMBASE as well as conference proceedings from January 1985 to September 2011 for RCTs. Two review authors independently screened search results.

SELECTION CRITERIA

Randomised controlled trials comparing chemotherapy or immuno-chemotherapy with HDT followed by ASCT in adults with previously untreated or relapsed FL.

DATA COLLECTION AND ANALYSIS

We used hazard ratios (HR) as effect measures used for OS and PFS as well as relative risks for response rates. Two review authors independently extracted data and assessed the quality of trials.

MAIN RESULTS

Our search strategies led to 3046 potentially relevant references. Of these, five RCTs involving 1093 patients were included; four trials in previously untreated patients and one trial in relapsed patients. Overall, the quality of the five trials is judged to be moderate. All trials were reported as randomised and judged to be open-label studies, because usually trials evaluating stem cell transplantation are not blinded. Due to the small number of studies in each analysis (four or less), the quantification of heterogeneity was not reliable and not evaluated in further detail. A potential source of bias are uncertainties in the HR calculation. For OS, the HR had to be calculated for three trials from survival curves, for PFS for two trials.We found a statistically significant increased PFS in previously untreated FL patients in the HDT + ASCT arm (HR = 0.42 (95% confidence interval (CI) 0.33 to 0.54; P < 0.00001). However, this effect is not transferred into a statistically significant OS advantage (HR = 0.97; 95% 0.76 to 1.24; P = 0.81). The subgroup of trials adding rituximab to both intervention arms (one trial) confirms these results and the trial had to be stopped early after an interim analysis due to a statistically significant PFS advantage in the HDT + ASCT arm (PFS: HR = 0.36; 95% CI 0.23 to 0.55; OS: HR = 0.88; 95% CI 0.40 to 1.92). In the four trials in previously untreated patients there are no statistically significant differences between HDT + ASCT and the control-arm in terms of TRM (RR = 1.28; 95% CI 0.25 to 6.61; P = 0.77), secondary acute myeloid leukaemia/myelodysplastic syndromes (RR = 2.87; 95% CI 0.7 to 11.75; P = 0.14) or solid cancers (RR = 1.20; 95% CI 0.25 to 5.77; P = 0.82). Adverse events were rarely reported and were observed more frequently in patients undergoing HDT + ASCT (mostly infections and haematological toxicity).For patients with relapsed FL, there is some evidence (one trial, N = 70) that HDT + ASCT is advantageous in terms of PFS and OS (PFS: HR = 0.30; 95% CI 0.15 to 0.61; OS: HR = 0.40; 95% CI 0.18 to 0.89). For this trial, no results were reported for TRM, adverse events or secondary cancers.

AUTHORS' CONCLUSIONS

In summary, the currently available evidence suggests a strong PFS benefit for HDT + ASCT compared with chemotherapy or immuno-chemotherapy in previously untreated patients with FL. No statistically significant differences in terms of OS, TRM and secondary cancers were detected. These effects are confirmed in a subgroup analysis (one trial) adding rituximab to both treatment arms. Further trials evaluating this approach are needed to determine this effect more precisely in the era of rituximab. Moreover, longer follow-up data are necessary to find out whether the PFS advantage will translate into an OS advantage in previously untreated patients with FL.There is evidence that HDT + ASCT is advantageous in patients with relapsed FL.

p37Ing1b regulates B-cell proliferation and cooperates with p53 to suppress diffuse large B-cell lymphomagenesis

The Inhibitor of Growth (ING) gene family encodes structurally related proteins that alter chromatin to regulate gene expression and cell growth. The initial member, ING1, has also been proposed to function as a tumor suppressor in human cancer based on its ability to suppress cell growth and transformation in vitro. Mouse Ing1 produces two proteins (p31 and p37) from differentially spliced transcripts. We have recently generated p37(Ing1b)-null mice and observed spontaneous follicular B-cell lymphomagenesis in this model to show that ING proteins can function in vivo as tumor suppressors. In this present report, we examine the role of p37(Ing1b) in the regulation of B-cell growth and explore the relationship between p37(Ing1b) and p53-mediated tumor suppression. Our results indicate that p37(Ing1b) inhibits the proliferation of B cells and follicular B cells regardless of p53 status, and loss of p53 greatly accelerates the rate of B-cell lymphomagenesis in p37(Ing1b)-null mice. However, in contrast to the highly penetrant follicular B-cell lymphomas observed in p37(Ing1b)-null mice, mice lacking both p37(Ing1b) and p53 typically present with aggressive diffuse large B-cell lymphomas (DLBL). Analysis of marker gene expression in p37(Ing1b)/p53 null tumors indicates that the double-null mice develop both nongerminal center and germinal center B-cell-like DLBL, and also documents up-regulation of nuclear factor-kappaB activity in p37(Ing1b)/p53-null B cells and B-cell tumors. These results confirm that p53 mutation is an important mechanistic step in the formation of diffuse large B-cell lymphomas and reveals a p53-independent role for Ing1b in suppressing B-cell tumorigenesis.