A 67-year-old male with Eastern Cooperative Oncology Group performance status 1 underwent renal Doppler evaluation for new-onset malignant hypertension. On Doppler imaging, there were incidental findings of right lower pole and left mid-upper pole renal masses measuring 35 × 40 mm and 50 × 45 mm, respectively. The patient had a history of chronic obstructive airway disease, well-controlled type 2 diabetes, ischaemic heart disease post angioplasty, depression, obesity, obstructive sleep apnoea, and new-onset hypertension. Further investigation with MRI confirmed a well-circumscribed 35 × 36 × 42 mm mass in the right kidney lower pole with involvement of the pelvic fat but not the collecting system within the renal pelvis. There was a 55 × 48 × 50 mm exophytic mass, centring at the junction of the left mid and lower poles, with extension to the perinephric and pelvic fat (Fig. 1). Image-guided true-cut biopsy confirmed bilateral clear-cell RCC with Fuhrman Grades 3 and 2 on the left and right sides, respectively. There was no evidence of systemic metastatic disease on staging positron emission tomography/CT. Baseline renal function was within normal limits, with a serum creatinine level of 92 μmol/L, an estimated GFR (eGFR) of 74 mL/min, and a chromium-51-EDTA isotopic calculated GFR of 94 mL/min. The split function on technetium-99 (Tc-99 m) DMSA renal scan was 57%:43% left- and right-sided differential renal function, respectively. After discussion in our institutional multidisciplinary meeting, the patient was offered a staged surgical procedure with left radical nephrectomy, followed by further completion nephron-sparing partial nephrectomy of the right tumour, albeit with high risk of converting to radical nephrectomy due to involvement of the renal sinus. The patient declined a surgical procedure for bilateral tumours due to the high risk of losing both kidneys and lifelong dependence on renal replacement. Considering the involvement of renal pelvic fat and tumour size of >4 cm, interventional radiologists deemed that ablation was not a suitable option for the right-sided tumour because of the risk of ablation-related injury to renal pelvic structures. The right-sided tumour was considered suitable for stereotactic ablative body radiotherapy (SABR). Based on these factors and the patient's preference for avoiding dialysis, the patient was given an option of a hybrid treatment, with the combination of right-sided SABR followed by left radical nephrectomy, which he accepted. The patient consented to 26 Gy in a single fraction to the right-sided RCC. The patient was simulated with a four-dimensional CT scan while free-breathing. The BodyFix vacuum drape (Elekta, Stockholm, Sweden) was used to reduce respiratory motion. An internal target volume was contoured on the average intensity projection of the four-dimensional CT scan. A planning target volume was generated from an isotropic 5 mm margin expansion of internal target volume. The treatment plan consisted of nine non-coplanar fields with mixed energies at 6 MV and 18 MV using a three-dimensional conformal radiation therapy technique (Fig. 2). The volume of right non-tumour kidney receiving more than 50% of the prescription dose was 38.11 cm3 (23% of the total non-tumour kidney volume). The SABR was delivered as an outpatient treatment in a single visit, with approximate duration of 15 min from patient set-up to radiotherapy delivery. The treatment was well tolerated without any significant Grade 3 or 4 toxicity. The patient experienced Grade 1 fatigue post treatment. Three weeks after SABR, he underwent a left-sided robotic radical nephrectomy without significant complications. Histopathology confirmed 63 mm, Grade 3 clear-cell RCC with extension into the renal sinus fat. There was no extension into the peri-renal fat. His post-surgery renal function declined, with serum creatinine level and eGFR of 156 μmol/L and 41 mL/min, respectively. There was no approved adjuvant systemic treatment, so the patient was planned for ongoing surveillance with interval body imaging. The patient developed biopsy-proven left flank relapse along the biopsy track 18 months post treatment. After multidisciplinary meeting discussion, he underwent wide local excision. Histopathology confirmed clear-cell RCC with sarcomatoid features. The tumour was extending to the inked margin. Unfortunately, he experienced another relapse in the left flank, with the development of multiple bilateral lung metastases within 6 months of excision. He received various lines of systemic treatment in the subsequent 2 years and eventually died from the progressive left flank and systemic disease. During his management, the patient remained free of renal replacement therapy. His last serum creatinine and eGFR were 168 μmol/L and 36 mL/min, respectively. Follow-up Tc-99 m DSMA renal scan showed absence of uptake in the inferior pole of the right kidney which was consistent with irradiated volume (Fig. 3). On follow-up non-contrast CT, the right-sided RCC remained free of local progression, with minimal reduction in size (4 mm from baseline). Bilateral RCC, either synchronous or metachronous, accounts for approximately 1%–5% of RCC cases [1]. Approximately 90% of bilateral RCCs are sporadic [2]. Synchronous RCCs present a clinical dilemma concerning management decisions. There is no standard of care, and management varies based on the complexity of the individual case. Nephron-sparing approaches are preferred to preserve renal function because of the adverse cardiovascular outcomes associated with chronic kidney disease. If feasible, nephron-sparing partial nephrectomy (PN) is the preferred surgical procedure for bilateral RCC. After PN for bilateral RCC, a mild to moderate decline in renal function is expected, with reported long-term haemodialysis rates of approximately 10% [3]. If bilateral PN is not feasible, every attempt should be made for at least one-sided PN to preserve adequate renal function and avoid lifelong dialysis. Similar to the surgical recommendation in our case, many surgeons prefer a two-step staged surgical procedure [1, 2]. The more complex nephron-sparing PN is performed first to allow some compensation from the contralateral kidney. However, some surgeons prefer a single intervention that reduces psychological and physiological stress, single anaesthesia, and reduced hospital stay. Thermal ablation (TA) is an excellent alternative strategy to preserve renal function in scenarios where one-sided PN is not feasible. However, such tumours are generally not ideal for TA as an alternative treatment. In the reported case, the patient was a high-risk candidate for PN and not a TA candidate because of the large tumour size (>4 cm) and proximity to the renal pelvic structures. Such cases are challenging to the treating physician because of the lack of other nephron-sparing approaches. Over the last decade, SABR has emerged and its use in treating primary RCC has been increasing. In a meta-analysis of 26 studies including 372 patients, Correa et al. reported random-effect estimates for local control of 97.2%, with Grade 3–4 toxicity of only 1.5% [4]. The change in eGFR was acceptable, with a mean decline of 7.7 mL/min. Despite most patients having pre-SABR renal dysfunction, only 2.9% of patients required dialysis. None of the 35 solitary kidney patients required dialysis in this meta-analysis. In clinical scenarios where a one-sided nephron-sparing approach is not possible with either PN or TA, SABR can be an excellent alternative treatment to avoid the lifelong need for dialysis. In the case reported here, the patient underwent SABR treatment for right-sided RCC and nephrectomy for left RCC. There was no reported progression of the right-sided tumour during follow-up. A 50% decline in eGFR was observed immediately after left-sided radical nephrectomy. However, the renal function decline was minimal in the following 4 years (baseline post-nephrectomy eGFR 41 mL/min vs last follow-up eGFR 36 mL/min). The patient remained free of dialysis for the entire course of treatment. As evident in this case (Fig. 3), SABR has the advantage of high conformal dose distribution, which can leave adequate functional renal parenchyma after treatment. The loss of functional renal tissue would have been similar if the patient had undergone PN. Another interesting approach would be to consider SABR for bilateral RCC, particularly in elderly frail patients, long-term anticoagulation patients, or those with multiple competing comorbidities. In this scenario, SABR could be deployed as the first treatment approach whilst reserving surgery as a salvage procedure. SABR for synchronous bilateral RCC has been reported to result in acceptable renal function decline without the need for renal replacement therapy [5]. However, in that case report, the follow-up was <2 years. In conclusion, this case highlighted that SABR could be safe to include in the management paradigm for selected synchronous bilateral RCC, particularly in cases where other nephron-sparing approaches are not feasible. This approach can prevent the lifelong need for renal replacement therapy. This work has no specific funding. Muhammad Ali is a PhD candidate supported through an Australian Government Research Training Program scholarship. Shankar Siva is supported by the Cancer Council Victoria Colebatch Fellowship Open access publishing facilitated by The University of Melbourne, as part of the Wiley - The University of Melbourne agreement via the Council of Australian University Librarians.