Long-Term Follow-Up of Allogeneic Hematopoietic Stem Cell Transplantation for Solid Cancer

Graft-versus-cancereffect and innovative approaches in thetreatment of refractory solid tumors

Background/aim

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been used for the treatment of various refractory solid tumors during the last two decades. After the demonstration of graft-versus-leukemia (GvL) effect in a leukemic murine model following allo-HSCT from other strains of mice, graft-versus-tumor (GvT) effect in a solid tumor after allo-HSCT has also been reported in a murine model in 1984. Several trials have reported the presence of a GvT effect in patients with various refractory solid tumors, including renal, ovarian and colon cancers, as well as soft tissue sarcomas [1]. The growing data on haploidentical transplants also indicate GvT effect in some pediatric refractory solid tumors. Novel immunotherapy-based treatment modalities aim at inducing an allo-reactivity against the metastatic solid tumor via a GvT effect. Recipient derived immune effector cells (RDICs) in the antitumor reactivity following allo-HSCT have also been considered as an emerging therapy for advanced refractory solid tumors.

Conclusion

This review summarizes the background, rationale, and clinical results of immune-based strategies using GvT effect for the treatment of various metastatic and refractory solid tumors, as well as innovative approaches such as haploidentical HSCT, CAR-T cell therapies and tumor infiltrating lymphocytes (TIL).

Proceedings From the Fourth Haploidentical Stem Cell Transplantation Symposium (HAPLO2016), San Diego, California, December 1, 2016

The resurgence of haploidentical stem cell transplantation (HaploSCT) over the last decade is one of the most important advances in the field of hematopoietic stem cell transplantation (HSCT). The modified platforms of T cell depletion either ex vivo (CD34+ cell selection, "megadoses" of purified CD34+ cells, or selective depletion of T cells) or newer platforms of in vivo depletion of T cells, with either post-transplantation high-dose cyclophosphamide or intensified immune suppression, have contributed to better outcomes, with survival similar to that in HLA-matched donor transplantation. Further efforts are underway to control viral reactivation using modified T cells, improve immunologic reconstitution, and decrease the relapse rate post-transplantation using donor-derived cellular therapy products, such as genetically modified donor lymphocytes and natural killer cells. Improvements in treatment-related mortality have allowed the extension of haploidentical donor transplants to patients with hemoglobinopathies, such as thalassemia and sickle cell disease, and the possible development of platforms for immunotherapy in solid tumors. Moreover, combining HSCT from a related donor with solid organ transplantation could allow early tapering of immunosuppression in recipients of solid organ transplants and hopefully prevent organ rejection in this setting. This symposium summarizes some of the most important recent advances in HaploSCT and provides a glimpse in the future of fast growing field.

Recipient and donor cells in the graft-versus-solid tumor effect: It takes two to tango

Allogeneic hematopoietic stem cell transplantation (alloHSCT) produces -similar to the long-established graft-versus-leukemia effect- graft-versus-solid-tumor effects. Clinical trials reported response rates of up to 53%, occurring mostly but not invariably in association with full donor chimerism and/or graft-versus-host disease. Although donor-derived T cells are considered the principal effectors of anti-tumor immunity after alloHSCT or donor leukocyte infusion (DLI), growing evidence indicate that recipient-derived immune cells may also contribute. Whereas the role of recipient-derived antigen-presenting cells in eliciting graft-versus-host reactions and priming donor T cells following DLI is well known, resulting inflammatory responses may also break tolerance of recipient effector cells towards the tumor. Additionally, mouse studies indicated that post-transplant recipient leukocyte infusion produces anti-leukemia and anti-solid-tumor effects that were exclusively mediated by recipient-type effector cells, without graft-versus-host disease. Here, we review current preclinical and clinical evidence on graft-versus-solid-tumor effects and growing evidence on the effector role of recipient-derived immune cells in the anti-tumor effect of alloHSCT.

Long-term outcome in patients treated at home during the pancytopenic phase after allogeneic haematopoietic stem cell transplantation

Patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT) were given the option to be treated at home during the pancytopenic phase. Daily visits by a nurse and phone calls from a physician from the unit were part of the protocol. During almost two decades, 252 patients with haematological malignancies and non-malignant disorders were included. Median age was 47 (range 0-72) years. Myeloablative conditioning was given to 102 patients and reduced intensity to 150. Donors were matched unrelated (n = 160), HLA-identical siblings (n = 71), or HLA-mismatched (n = 21). Cumulative incidence of acute graft-versus-host disease (GVHD) was 35% and that of chronic GVHD was 46%. Non-relapse mortality was 14% 10 years after HSCT. In patients with haematological malignancies (n = 229), the 10-year probability of relapse was 34%. No patients died at home. Overall survival was 59% and relapse-free survival was 50% after 10 years. We conclude that patients treated at home after HSCT have an encouraging long-term outcome.

Cancer vaccines and immunotherapeutic approaches in hepatobiliary and pancreatic cancers

Hepatobiliary and pancreatic cancers along with other gastrointestinal malignancies remain the leading cause of cancer-related deaths worldwide. Strategies developed in the recent years on immunotherapy and cancer vaccines in the setting of primary liver cancer as well as in pancreatic cancer are the scope of this review. Significance of orthotopic and autochthonous animal models which mimic and/or closely reflect human malignancies allowing for a prompt and trustworthy analysis of new therapeutics is underlined. Combinational approaches that on one hand, specifically target a defined cancer-driving pathway, and on the other hand, restore the functions of immune cells, which effector functions are often suppressed by a tumor milieu, are shown to have the strongest perspectives and future directions. Among combinational immunotherapeutic approaches a personalized- and individual cancer case-based therapy is of special importance.

The Principles of Engineering Immune Cells to Treat Cancer

Chimeric antigen receptor (CAR) T cells have proven that engineered immune cells can serve as a powerful new class of cancer therapeutics. Clinical experience has helped to define the major challenges that must be met to make engineered T cells a reliable, safe, and effective platform that can be deployed against a broad range of tumors. The emergence of synthetic biology approaches for cellular engineering is providing us with a broadly expanded set of tools for programming immune cells. We discuss how these tools could be used to design the next generation of smart T cell precision therapeutics.

Risk Factors for Subsequent Central Nervous System Tumors in Pediatric Allogeneic Hematopoietic Cell Transplant: A Study from the Center for International Blood and Marrow Transplant Research (CIBMTR)

Survivors of hematopoietic cell transplantation (HCT) are at risk of subsequent solid tumors, including central nervous system (CNS) tumors. The risk of CNS tumors after HCT in pediatric HCT recipients is not known. We evaluated the incidence and risk factors for CNS tumors in pediatric recipients of allogeneic HCT reported to the Center for International Blood and Marrow Transplant Research between 1976 and 2008. A case control design was used. There were no CNS tumors in the nonmalignant cohort (n = 4543) or in those undergoing HCT for solid tumors (n = 26). There were 59 CNS tumors in 8720 patients transplanted for hematologic malignancies. In comparison with the general population, pediatric HCT recipients with hematologic malignancies had a 33 times higher than expected rate of CNS tumors (95% confidence interval, 22.98 to 45.77; P < .0001). The cumulative incidence of subsequent CNS tumors was 1.29% (95% confidence interval .87 to 1.87) at 20 years after HCT. Significant risk factors in the entire cohort were having an unrelated donor (HR, 3.35; P = .0002) and CNS disease before HCT for both acute lymphoblastic leukemia (HR, 8.21; P = .0003) and acute myeloid leukemia (HR, 6.21; P = .0174). Analysis of the matched cohort showed having an unrelated donor transplant (HR, 4.79; P = .0037), CNS disease before HCT (HR, 7.67; P = .0064), and radiotherapy exposure before conditioning (HR, 3.7; P = .0234) to be significant risk factors. Chronic graft-versus-host disease was associated with a lower risk (HR, .29; P = .0143). Survivors of HCT for nonmalignant diseases did not show an increased incidence of CNS tumors, whereas survivors of hematologic malignancies have a markedly increased incidence of CNS tumors that warrants lifelong surveillance.

Review of allogeneic hematopoietic stem cell transplantation with reduced intensity conditioning in solid tumors excluding breast cancer

Solid tumors in adults constitute a heterogeneous group of malignancy originating from various organ systems. Solid tumors are not completely curable by chemotherapy, even though some subgroups are very chemo-sensitive. Recently, oncologists have focused on the use of allogeneic hematopoietic stem cell transplantation (allo-HSCT) with reduced intensity conditioning (RIC) for the treatment of some refractory solid tumors. After the demonstration of allogeneic graft-versus-leukemia effect in patients with hematological malignancies who received allo-HSCT, investigators evaluated this effect in patients with refractory metastatic solid tumors. According to data from experimental animal models and preliminary clinical trials, a graft-versus-tumor (GvT) effect may also be observed in the treatment of some solid tumors (e.g., renal cell cancer, colorectal cancer, etc.) after allo-HSCT with RIC. The use of RIC regimens offers an opportunity of achieving full-donor engraftment with GvT effect, as well as, a reduced transplant-related mortality. Current literature suggests that allo-HSCT with RIC might become a choice for elderly and medically fragile patients with refractory metastatic solid tumors.