Outcome of radiation therapy for renal transplant rejection refractory to chemical immunosuppression

Recombinogenic, genotoxic, and cytotoxic effects of azathioprine using in vivo assays

Azathioprine (Aza) is a purine antimetabolite immunosuppressant that is widely employed for immunosuppressive therapy in post-transplant recipients or patients with autoimmune diseases. Chronic use of immunosuppressants might produce several side effects, including a high rate of neoplasms in these patients. Considering that genotoxic effects are associated with an increased risk of developing cancer, the aim of this study was to examine the recombinogenic, genotoxic, and cytotoxic effects of Aza using Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster, as well as comet and micronucleus assays in mouse bone marrow cells. Further, the adverse effects of Aza were determined in mouse hepatic and renal tissues using histopathological analysis. Data demonstrated that Aza induced significant increased genotoxicity in D. melanogaster and mouse bone marrow cells at all concentrations tested. Homologous recombination was the predominant genotoxic event noted for the first time to be initiated by Aza in SMART. In histopathological analysis, Aza did not show any marked toxic activity in mouse hepatic and renal tissues. Therefore, the high rate of neoplasms reported in patients with long-term use of Aza may be attributed, at least partially, to the genotoxic action of this drug.

Local graft irradiation for kidney allograft rejection: a case series and review of the literature

Introduction:

Due to its immunosuppressive properties, local graft irradiation (LGI) has been proposed as a second line therapy for treatment of acute kidney rejection.

Case Presentation:

In this case-series we report 6 patients with biopsy proven acute kidney allograft rejection refractory to conventional antirejection therapy who underwent LGI for treatment of acute rejection at our center. Three of these patients had living donor transplants, 2 had deceased donor transplants, and one had received a simultaneous kidney/pancreas transplant. All patients were treated with anti thymocyte-globulin or muromonab-CD3, and intravenous steroids for initial treatment of rejection. Three patients also received intravenous immunoglobulin. LGI was tried as a last resort and was well tolerated and resulted in either improvement or stabilization of renal function in 5 patients. One patient could not be given the complete course of chemical immunosuppression for treatment of rejection due to concomitant cryptococcal meningitis and was switched to LGI with good short-term response.

Discussion:

Our results suggest that LGI could be considered a second line therapy to the conventional anti-rejection therapy for patients with refractory acute kidney allograft rejection, or for patients who cannot receive systemic immunosuppression due to severe infection.

Radiotherapy for Rejection of Renal Transplant Allografts Refractory to Medical Immunosuppression

OBJECTIVE

To evaluate the outcome and prognostic factors of patients who underwent local graft irradiation for acute renal allograft rejection refractory to modern immunosuppressive medications.

METHODS

From 1996 to 2005, 33 patients received local graft irradiation (LGI), with 3 patients receiving 2 courses of radiation. Graft rejection was diagnosed when a rise in creatinine prompted a renal biopsy that demonstrated acute allograft rejection. Upon failure of medical immunosuppresion to resolve rejection, patients were then referred by the organ transplant team for LGI. The median dose was 800 cGy (range, 600-800 cGy), and was given in 200 cGy fractions generally using AP/PA fields. A retrospective review was conducted to determine dialysis-free survival, defined as the date from initiation of radiation therapy to date of hemodialysis placement, and to analyze potential factors that may predict dialysis free survival.

RESULTS

Median follow-up from date of radiation therapy to date of last follow-up was 25 months (range, 0.9-99.4 months). The median time between allograft transplantation and radiation therapy was 17.8 months. For the entire group of patients, 20.6% were alive with a functioning graft. The median dialysis-free survival for the entire group was 3.8 months. The median dialysis-free survival for those patients not on dialysis at time of irradiation versus those patients on dialysis was significantly different (5.6 versus 0 months, P = 0.02).

CONCLUSION

In renal allograft transplant recipients who experienced acute rejection episodes refractory to modern chemical immunosuppression, LGI was well tolerated and remains a viable salvage treatment option.