Initial Experience with Tositumomab and I-131-Labeled Tositumomab for Treatment of Relapsed/Refractory Hodgkin Lymphoma

PURPOSE

To determine the maximum tolerated dose (MTD) of [¹³¹I]tositumomab in patients with refractory/recurrent Hodgkin lymphoma (HL) and to preliminarily determine if [¹³¹I]tositumomab has activity against HL and if positron emission tomography (PET) with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]DG) performed 6 weeks post-therapy predicted 12-week response.

PROCEDURES

Separate dose-finding studies were performed for patients with and without prior transplant. A single therapeutic total body radiation dose (TBD) of [¹³¹I]tositumomab was administered. TBD was escalated/de-escalated based on dose-limiting hematologic toxicity (DLT) using a modified continual reassessment method. [¹⁸F]DG-PET/CT scans were performed at baseline and 6 and 12 weeks post therapy.

RESULTS

Twelve patients (nine classical HL, three lymphocyte-predominant [LP] HL) completed two dosing levels (n = 3 each) in the post-transplant (55 cGy, 79 cGy) and no transplant (75 cGy, 87 cGy) groups. Hematologic toxicities were common and transient. Twelve weeks after [¹³¹I]tositumomab, 10 patients progressed and two with LPHL achieved complete response. [¹⁸F]DG-PET/CT at 6 weeks post therapy appeared more predictive than CT at 6 weeks of a response at 12 weeks.

CONCLUSIONS

Tositumomab and [¹³¹I]tositumomab was well-tolerated in patients with relapsed/refractory HL. Complete responses in LPHL support a therapeutic effect in this subtype. Early metabolic response assessments by [¹⁸F]DG-PET in HL after radioimmunotherapy appear to be more predictive than purely anatomic assessments.

Role of immune escape mechanisms in Hodgkin's lymphoma development and progression: a whole new world with therapeutic implications

Hodgkin's lymphoma represents one of the most frequent lymphoproliferative syndromes, especially in young population. Although HL is considered one of the most curable tumors, a sizeable fraction of patients recur after successful upfront treatment or, less commonly, are primarily resistant. This work tries to summarize the data on clinical, histological, pathological, and biological factors in HL, with special emphasis on the improvement of prognosis and their impact on therapeutical strategies. The recent advances in our understanding of HL biology and immunology show that infiltrated immune cells and cytokines in the tumoral microenvironment may play different functions that seem tightly related with clinical outcomes. Strategies aimed at interfering with the crosstalk between tumoral Reed-Sternberg cells and their cellular partners have been taken into account in the development of new immunotherapies that target different cell components of HL microenvironment. This new knowledge will probably translate into a change in the antineoplastic treatments in HL in the next future and hopefully will increase the curability rates of this disease.

Molecular Pathogenesis of Hodgkin's Lymphoma: Increasing Evidence of the Importance of the Microenvironment

Hodgkin's lymphoma (HL) represents the most common subtype of malignant lymphoma in young people in the Western world. Most patients can be cured with modern treatment strategies, although approximately 20% will die after relapse or progressive disease. The histologic hallmark of the disease is the presence of the characteristic Hodgkin Reed-Sternberg (HRS) cells in classical HL and so-called lymphocyte-predominant (LP) cells in nodular lymphocyte-predominant HL. HL is unique among all cancers because malignant cells are greatly outnumbered by reactive cells in the tumor microenvironment and make up only approximately 1% of the tumor. Expression of a variety of cytokines and chemokines by the HRS and LP cells is believed to be the driving force for an abnormal immune response, perpetuated by additional factors secreted by reactive cells in the microenvironment that help maintain the inflammatory milieu. The malignant HRS and LP cells manipulate the microenvironment, permitting them to develop their malignant phenotype fully and evade host immune attack. Gene expression signatures derived from non-neoplastic cells correlate well with response to initial and subsequent therapies, reflecting their functional relevance. Recent biomarker studies have added texture to clinical outcome predictors, and their incorporation into prognostic models may improve our understanding of the biologic correlates of treatment failure. Moreover, recent preclinical and clinical studies have demonstrated that the tumor microenvironment represents a promising therapeutic target, raising hope that novel treatment strategies focused on the interface between malignant and reactive cells will soon emerge.

Gene Expression Profiling for In Silico Microdissection of Hodgkin's Lymphoma Microenvironment and Identification of Prognostic Features

Gene expression profiling studies based on DNA microarrays have demonstrated their ability to define the interaction pathways between neoplastic and nonmalignant stromal cells in cancer tissues. During the past ten years, a number of approaches including microdissection have tried to resolve the variability in DNA microarray measurements stemming from cancer tissue sample heterogeneity. Another approach, designated as virtual or in silico microdissection, avoids the laborious and time-consuming step of anatomic microdissection. It consists of confronting the gene expression profiles of complex tissue samples to those of cell lines representative of different cell lineages, different differentiation stages, or different signaling pathways. This strategy has been used in recent studies aiming to analyze microenvironment alterations using gene expression profiling of nonmicrodissected classical Hodgkin lymphoma tissues in order to generate new prognostic factors. These recent contributions are detailed and discussed in the present paper.

Rituximab in Hodgkin lymphoma: is the target always a hit?

In 1997, the anti-CD20 monoclonal antibody (MAb) rituximab became the first MAb approved for clinical use in oncology, and ushered in a new era of rationally designed targeted agents in cancer therapeutics. It is currently approved for use in non-Hodgkin lymphoma (NHL), chronic lymphoid leukemia (CLL), and rheumatoid arthritis (RA). Rituximab is non-mutagenic, associated with low treatment-related toxicity, and few, if any, long term adverse events, making it an attractive agent to be tried in off-label settings like Hodgkin lymphoma (HL). HL consists of two distinct subtypes - classic HL (cHL) and lymphocyte predominant HL (LPHL). CD20 is present in virtually all patients with LPHL, and in a significant minority of patients with cHL. In this CD20 positive sub-population, the use of rituximab is a rational intervention strategy. Rituximab has been used in patients with cHL as well as LPHL with good efficacy. In this article, we provide a clinically-oriented overview of the use of rituximab in the different sub-types of HL, and report updated results of our series of 8 LPHL patients treated with rituximab. A systematic review of the literature is also presented.

The Role of Allogeneic Stem Cell Transplantation in Relapsed/Refractory Hodgkin's Lymphoma Patients

Despite the favorable prognosis of most patients with Hodgkin's Lymphoma (HL), 15-20% of patients remain refractory to chemoradiotherapy, and 20-40% experience relapses following autologous stem cell transplantation (SCT) being used as salvage approach in this situation. Long-term survival of only 20% was reported for patients who failed this option. As some authors suggested the presence of a graft versus HL effect, allogeneic SCT was introduced as a further option. Myeloablative strategies were reported to be able to achieve cure in some younger patients, but high nonrelapse mortality remains a problem. Reduced intensity conditioning, in turn, was found to be associated with high posttransplant relapse rates. As there is currently no standard in the management of HL patients who failed autologous SCT, we here review the literature on allogeneic stem cell transplantation in HL patients with a special focus on the outcomes and risk factors being reported in the largest studies.