Systematic review of ablative therapy for the treatment of renal allograft neoplasms

ARTICLE HIGHLIGHTS

Research background

Kidney allograft tumours represent a challenging complication of renal transplantation. Optimal treatment should ensure adequate oncological results while preserving as much renal function as possible. For many years, graftectomy has been considered the gold standard. In the last decade, improved surgical techniques and technological advances have favoured the use of nephron-sparing alternatives such as partial nephrectomy and focal ablation. Preliminary reports on ablation treatment of solid masses of the kidney allograft have shown promising results. However, solid evidence supporting widespread application of ablation therapy are lacking and there is still concern in the transplant community regarding efficacy and safety in the long term. To date, no guideline, meta-analysis or systematic review on the topic have been published.

Research motivation

The rarity of the disease and the multiple options available (radiofrequency ablation, cryoablation, microwave ablation, high-intensity focused ultrasound, and irreversible electroporation) make it extremely difficult to assess results of ablation therapy for the treatment of kidney allograft neoplasms. A better insight into this complex topic would help clinicians choose the best treatment and provide the basis for further research.

Research objectives

We performed a systematic review of ablation therapy for the treatment of solid neoplasms of the transplanted kidney. All major ablation techniques were considered. Overall and treatment-specific outcomes were extensively reported in order to offer a comprahensive overview on currently availbale data and remark the need for properly designed clinical trials.

Research methods

We conducted a systematic review according to the PRISMA 2009 Checklist. PubMed was extensively searched in March 2019 for any papers reporting on ablation therapy of kidney allograft neoplasms. Only English manuscripts were considered. No time limits were applied. Multiple key word combinations were used. Duplicate articles were removed. Remainder were screened out reading titles and abstracts. Manuscripts potentially describing cases of ablation of kidney allograft tumours were assessed in full text. Only original studies reporting on actual cases of ablative treatment of neoplasms in the transplanted kidney were included. Additional search of reference lists was performed. Selected studies were also assessed for methodological quality using a tool based on a modification of the Newcastle Ottawa scale. Data were extracted and transferred to a dedicated database for analysis purpose. Given the nature of the studies and the large heterogeneity of the patients included, we decided not to meta-analyze data. To the best of our knowledge, this is the first systematic review on the topic.

Research results

Preliminary search identified 133206 articles. After duplicate were removed (n = 87755), a pool of 45451 manuscripts remained for further evaluation. Reviewing articles by title and abstract, 110 full text papers were selected. Articles not reporting on original cases of ablation of kidney allograft tumours were excluded (n = 82). No additional cases were found through references lists. At the end of the process, 28 studies were included in the systematic review: 12 retrospective case reports, 13 single-centre retrospective non-comparative case series, 2 multi-centre retrospective non-comparative case series, and 1 multi-centre retrospective comparative study. In total, 100 kidney transplant neoplasms in 92 recipients were treated by 100 ablation procedures: 78 radiofrequency ablation, 15 cryoablation, 3 microwave ablation, 3 high-intensity focused ultrasound, and 1 irreversible electroporation. According to our review, incidence of renal allograft neoplasms is approximately 0.2%. Recipient age at the time of tumour diagnosis ranged from 21 to 71 years whereas time between transplant and diagnosis ranged from 0.1 to 312 mo. Most represented lesions were papillary and clear cell renal cell carcinomas. Considered neoplasms were more often endophytic with a maximal tumour diameter ranging from 5 to 55 mm. The vast majority were asymptomatic masses staged T1a N0 M0. Ablation was predominantly performed using a percutaneous route under ultrasound or computed tomography guidance. Overall, retrieved reports showed that ablation therapy was effective with only 3 episodes of primary tratment failures and 1 episode of local recurrence. Safety was also satisfactory. There were no intra-operative complications or cancer-related deaths. Post-operative complications were rare and allograft function was preserved in most of the recipients. Follow-up range was 1-81 mo.

Research conclusions

Our systematic review, shows that ablation therapy has been increasingly used as an effective and safe alternative to graftectomy and nephron-sparing surgery in carefully selected recipients with kidney allograft neoplasms. In particular, ablation was successfully offered to all patients with benign tumours or with T1a N0 M0 malignant lesions not suitable for more demanding surgical procedures. Main advantages of ablation therapy were easy feasibility, mini-invasiveness, short intra-operative time, reduced risk of bleeding, low post-operative complication rate, preserved allograft function, and short hospital stay. The inability to obtain definitive histological diagnosis and the difficult follow-up represented the main limitations of ablation therapy.

Research perspectives

Overall results of ablation therapy are encouraging but there is still a lack of long-term efficacy and safety data. Current evidence do not allow to safely extend indications to more advanced cancer stages. Radiofrequency ablation is the most widely used ablative modality. Proper comparison between different ablation therapies is limited by the small experience gained with cryoablation, microwave ablation, high-intensity focused ultrasound, and irreversible electroporation. In theory, tailored treatments might help achieve the best outcomes. Properly designed multi-centre prospective randomized clinical trials are needed.