New scoring system identifies kidney outcome with radiation therapy in acute renal allograft rejection.

Purpose: To evaluate the role of radiation therapy for acute refractory renal rejection after failure of medical intervention, and to identify risk factors that influence graft survival following radiation therapy.

Methods: Between June 1989 and December 1995, 53 renal transplant recipients (34 men and 19 women) were treated with localized radiation therapy for acute renal allograft rejection. Graft rejection was defined as an increase in serum creatinine with histologic evidence of rejection on renal biopsy. Ninety-one percent were cadaveric transplant recipients. The majority of patients who experienced acute graft rejection initially received corticosteroid therapy, except for 25% who were referred for radiation therapy and steroids for the first rejection. In more recent years, patients with moderate or severe steroid-resistant or recurrent rejection received OKT3, a polyclonal antilymphocyte antibody (ATGAM), tacrolimus (FK506), or mycophenolate mofetil (MMF). Patients who failed to respond to medical treatment were then referred for radiation therapy. Ultrasound was performed for kidney localization. Treatment consisted of a dose of 600 cGy given in 3 or 4 fractions using 6 MV photons, delivered AP or AP/PA.

Results: The overall actuarial graft survival from the initiation of RT was 83% at 1 month, 60% at 1 year, and 36% at 5 years. The median follow-up from the date of transplant to the last follow-up was 22 months. The median time from the date of transplant to the initiation of radiotherapy was 3 months, and the median time from the initiation of radiotherapy to the last follow-up was 10 months. Variables evaluated were as follows: human leukocyte antigen matching on HLA-A, HLA-B, and HLA-DR, the transplant panel-reactive antibodies (PRA) at transplantation, number of acute rejection episodes, interval from the date of the transplant to the first rejection, serum creatinine levels at the time of the first radiation treatment, number of transplants, and concomitant immunosuppressive therapy. Independent factors examined by Cox regression modeling were: gender (p = 0.005), creatinine levels (p = 0.000), HLA-DR (p70% (p = 0.014). Each factor was scored using integral coefficients to generate four different groups. The Kaplan-Meier survival analyzed by group produces an interpretable separation of the risk factors for graft loss.

Conclusions: The outcome in patients treated with radiation therapy for acute renal graft rejection can be predicted by a novel scoring system. Patients with scores of three or less are able to achieve 100% renal graft salvage, while patients who have scores of 12 or higher are not able to be salvaged with the current radiation therapy regimen. Future studies should be directed toward identifying more effective treatment for patients who have a high score based on our criteria. The scoring system should be utilized to identify patients at risk who could benefit from radiation therapy. Further study with a randomized trial utilizing this scoring system is needed to confirm the validity of the scoring system in predicting graft survival and the efficacy of radiation in patients who receive radiation therapy for acute graft rejection.