Effect of Stereotactic Body Radiotherapy on the Growth Kinetics and Enhancement Pattern of Primary Renal Tumors

Results of Stereotactic Body Radiation Therapy for Primary Renal Cell Carcinoma in a Large Multicenter Series

BACKGROUND AND OBJECTIVE

For inoperable patients, stereotactic body radiation therapy (SBRT) is a noninvasive treatment approach for primary renal cell carcinoma (RCC). We aimed to evaluate local control (LC) of primary RCC treated with SBRT.

METHODS

This multicenter retrospective study involved 16 centers in Australia, France, Italy, and the Netherlands. The primary endpoint was the LC probability, and the secondary endpoints were progression-free survival, overall survival (OS), cumulative incidence of cancer-related deaths, toxicities, and renal function evolution after SBRT.

KEY FINDINGS AND LIMITATIONS

A total of 144 patients, treated between 2008 and 2020, with a median follow-up of 43 mo (interquartile range [IQR], 24.0-81.2), were included. The median age was 76 yr (IQR, 67.0-82.0) and the median tumor size was 4.4 cm (IQR, 3.3-5.6). The median baseline estimated glomerular filtration rate (eGFR) was 60 ml/min/1.73 m2. Of the patients, 40% had mild to moderate eGFR (30-60 ml/min). The two main treatment regimens were 42 Gy in three fractions and 26 Gy in one fraction. The LC probability was 98% at 1 yr (95% confidence interval [CI], 94-99) and 96% (95% CI, 92-99) at 5 yr. The median OS was 58 mo and the cumulative incidence of cancer-related deaths was 8% (95% CI, 3-15) at 5 yr. Seventy-one patients (49%) experienced at least one toxicity, including grade 1 in the majority (32%), grade 2 (14%), and grade 3 (1%). Two patients (1%) underwent dialysis (grade 4). The median eGFR loss was -7 ml/min (IQR, -17; 0) at the last follow-up.

CONCLUSIONS AND CLINICAL IMPLICATIONS

This large series of primary RCC treated with SBRT demonstrates excellent LC and renal function preservation, and is associated with an acceptable toxicity profile. SBRT is an alternative treatment for inoperable patients.

Response evaluation and tumor shrinkage pattern post-SBRT for renal cell carcinoma

PURPOSE

Despite the promising application of stereotactic body radiotherapy (SBRT) in renal cell carcinoma (RCC), the optimal time and method for assessing tumor responses to SBRT remain unclear. We aimed to compare the utility of Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 and modified RECIST (mRECIST) in RCC response assessment and clarify the tumor shrinkage pattern post-SBRT.

MATERIALS AND METHODS

We retrospectively studied patients with RCC treated with SBRT at our institution between November 2016 and December 2021. Baseline and follow-up images were evaluated using RECIST 1.1 and mRECIST. Landmark analyses were conducted to assess the association between local control and tumor response status evaluated using the above two criteria.

RESULTS

Ninety-one RCC patients with 103 primary or metastatic lesions were included. Objective response rates (ORRs) were higher and pseudoprogression was less commonly assessed by mRECIST than by RECIST 1.1 within each time period. The median shrinkage rate of bone lesions was much lower using RECIST 1.1 than that using mRECIST (-0.8 vs -1.7 cm/year). According to both criteria, the ORR tended to be stable on the 9-12 months post-SBRT. Patients with a tumor response at 9-12 months had a lower probability of infield recurrence using mRECIST (P = 0.047), this was not observed using RECIST 1.1 (P = 0.061).

CONCLUSION

mRECIST results in an earlier and more pronounced response evaluation compared to RECIST 1.1 in patients with RCC treated with SBRT. Nine to twelve months post-SBRT may serve as an early landmark for tumor response evaluation by mRECIST.

A Randomized Trial of Stereotactic Body Radiation Therapy vs Radiofrequency Ablation for the Treatment of Small Renal Masses: A Feasibility Study (RADSTER)

OBJECTIVE

To evaluate the feasibility of a trial comparing stereotactic beam radiation therapy (SBRT) and radiofrequency ablation (RFA) for small renal masses (SRM).

METHODS

Patients opting for treatment of a SRM at a single center were randomized 1:1 to SBRT or RFA. Crossover if ineligible for treatment after randomization was allowed. Biopsies were completed prior to randomization and 12 months post-treatment. Our primary outcome was feasibility of the trial design. Secondary outcomes included treatment efficacy and safety.

RESULTS

Over 18 months, 33 patients were screened resulting in the recruitment and randomization of 24 patients (SBRT = 12; RFA = 12). Fourteen received SBRT, 7 RFA, and 3 dropped out. Crossover occurred from RFA to SBRT due to inability to perform RFA. Mean estimated glomerular filtration rate (EGFR) reduction was similar at 1 year (RFA -3 ml/minutes/1.73 m2, SBRT -5.3 ml/minutes/1.73 m2, P = .7). One-year biopsies were performed in 95.2% (20/21) of patients receiving treatment. Per protocol analysis demonstrated a higher pathologic response (RFA 100% vs SBRT 33.3.%, P = .01) in patients undergoing RFA compared to SBRT but not in the intention to treat analysis. No patients developed local failure, metastasis or death during the study period.

CONCLUSION

Recruitment, randomization, and follow-up of patients with SRMs was feasible and our results support performing a larger randomized trial. Multidisciplinary evaluation of patients before randomization is needed to assess RFA feasibility to reduce crossover. Both treatments have excellent short-term safety profiles. While not a surrogate for clinical response, RFA had a non-statistically significant improvement in pathological response.

CLINICALTRIALS

gov: NCT03811665.

Comparative efficacy and safety of ablative therapies in the management of primary localised renal cell carcinoma: a systematic review and meta-analysis

BACKGROUND

Non-invasive and minimally invasive ablative treatments, including stereotactic body radiotherapy (SBRT), radiofrequency ablation, microwave ablation, and cryoablation, have emerged as key treatment options for managing renal cell carcinoma, especially for patients who are unsuitable for surgery. We aimed to compare the clinical efficacy and safety of these emerging treatment methods in patients with localised renal cell carcinoma.

METHODS

In this systematic review and meta-analysis, we searched PubMed (MEDLINE), Embase, and the Cochrane Library for publications between Jan 1, 2000, and March 1, 2024. Eligible articles were observational studies and randomised controlled trials including at least five adult patients (age ≥18 years) with primary and localised renal cell carcinoma treated with SBRT, radiofrequency ablation, microwave ablation, or cryoablation and that reported on local control outcomes. Two reviewers independently screened titles and abstracts and then full texts of eligible studies were independently evaluated by the same reviewers, with disagreements resolved via discussion or consultation with a third reviewer. Summary estimates were extracted from published reports manually using a standardised data extraction form. The primary endpoint was local control rate at 1 year, 2 years, and 5 years after start of treatment. A meta-analysis was conducted using a DerSimonian and Laird model to summarise local control rates. Publication bias was evaluated using funnel plots and Egger's test. We also recorded the frequency and severity of adverse events after treatment on the basis of the Common Terminology Criteria for Adverse Events (version 5.0) and Clavien-Dindo complication index. The study protocol was prospectively registered with PROSPERO, CRD42024511840.

FINDINGS

We identified 6668 records, of which 330 were assessed via full-text review, and 133 were included in our systematic review and meta-analysis. The eligible studies included data for 8910 patients (mean age 67·9 years [SD 7·3], 2518 [31·4%] of 8018 patients with available data were female and 5500 [68·6%] were male). Local control rates for SBRT were 99% (95% CI 97-100; I2=6%) at 1 year, 97% (95-99; I2=0%) at 2 years, and 95% (89-98; I2=42%) at 5 years; for radiofrequency ablation were 96% (94-98; I2=73%) at 1 year, 95% (92-98; I2=77%) at 2 years, and 92% (88-96; I2=78%) at 5 years; for microwave ablation were 97% (95-99; I2=74%) at 1 year, 95% (92-98; I2=77%) at 2 years, and 86% (75-94; I2=66%) at 5 years; and for cryoablation were 95% (93-96; I2=61%) at 1 year, 94% (91-96; I2=69%) at 2 years, and 90% (87-93; I2=74%) at 5 years. The proportion of patients who reported grade 3-4 adverse events was 3% (121 of 3726) after cryoablation, 2% (39 of 2503) after radiofrequency ablation, 1% (22 of 2069) after microwave ablation, and 2% (11 of 612) after SBRT. Risk of bias was moderate in most studies (70 [53%] of 133) and no publication bias was observed.

INTERPRETATION

All investigated ablative methods continue to represent effective treatment choices in renal cell carcinoma, and these findings support multi-disciplinary discussions of these treatment methods, along with surgery and surveillance, to individualise treatment decisions in these patients. Future research should aim to conduct randomised controlled trials across larger patient populations to further elucidate the long-term oncological and survival outcomes associated with these treatments.

FUNDING

None.

Imaging and Nonsurgical Management of Renal Masses

In patients with renal masses, when intervention is warranted, partial nephrectomy is preferred when feasible, especially for T1 renal masses. Thermal ablation, however, has become an accepted alternative treatment of small renal neoplasms with excellent oncologic outcomes. The National Comprehensive Cancer Network guidelines include thermal ablation as a treatment strategy for managing T1a and select T1b masses. Other potential locoregional treatments for malignant and benign renal masses are emerging. Stereotactic body radiation therapy (SBRT) is gaining traction in the management of select localized renal masses and can be considered in patients who are not surgical candidates. Imaging findings after SBRT differ from those after thermal ablation. As this technique becomes more widely used, the temporal evolution of post-SBRT changes needs to be understood to correctly identify local tumor progression. Renal artery embolization is accepted as safe and effective for patients with renal angiomyolipoma. It can also be used in the management of renal cell carcinoma as an adjunct to definitive treatment or for palliation in advanced disease. With the growing acceptance of local-regional treatment of renal masses and the corresponding number of related patients undergoing surveillance and postablation imaging, the diagnostic radiologist will have greater responsibility in the appropriate interpretation of follow-up imaging to accurately assess normal postprocedural findings and define oncologic outcomes. Such interpretations should be based on understanding of the procedure and related imaging findings, both acutely and in the years after treatment. Procedural complications and recurrent tumor are identifiable based on deviations from the expected course. ©RSNA, 2024 Supplemental material is available for this article.

Renal Oncocytoma Treated With Stereotactic Body Radiation Therapy in a Patient With Prior Pancoast Tumor

A renal oncocytoma is a benign tumor of the kidney, typically treated surgically or via ablation therapy, while a Pancoast tumor is a rare tumor of the lung apex, most often non-small cell lung cancer (NSCLC), usually managed with neoadjuvant chemoradiation followed by surgery. In this report, we discuss the diagnosis and management of a 72-year-old man who developed a renal oncocytoma and a recurrent Pancoast tumor. At the time of our patient's treatment for his renal oncocytoma, thermal and radiofrequency ablation were not frequently employed, and active surveillance was also not the standard of care. Therefore, a partial nephrectomy was offered but declined by the patient over quality of life concerns. Following a discussion with radiation oncology, the patient instead opted for stereotactic body radiation therapy (SBRT), which was well tolerated. All clinical and imaging follow-up revealed excellent control of the lesion with no progression. To our knowledge, this is one of the first reported cases of an oncocytoma successfully treated with SBRT. The patient's stage 3 NSCLC Pancoast tumor was treated with the vinblastine cisplatin radiation therapy (VCRT) protocol, first developed at the Verspeeten Family Cancer Centre in London, Ontario. It consisted of four cycles of vinblastine and cisplatin, with the last two cycles administered concurrently with radiation therapy. This treatment produced excellent symptom control and an impressive nine years of disease-free survival. When the Pancoast tumor re-emerged at the end of this interval, it was treated with palliative reirradiation, and symptom control was excellent for another 10 months until a right-sided occipital lobe metastatic lesion was discovered and the patient succumbed to his disease. This report provides a clinical example of the viability and safety of SBRT for the treatment of renal oncocytoma. Importantly, SBRT has shown efficacy in treating renal cell carcinoma, the malignant differential of a renal oncocytoma. Clinicians should therefore consider SBRT for a renal oncocytoma when patients decline surgery (or ablation therapy) or when the pathologic diagnosis of the lesion is in doubt. Our case also provides an example of the successful treatment of a non-resectable NSCLC Pancoast tumor with the VCRT regimen and successful palliative re-irradiation of a recurrent Pancoast tumor.

Salvage stereotactic ablative body radiotherapy after thermal ablation of primary kidney cancer

OBJECTIVE

To evaluate the effectiveness and safety of salvage stereotactic ablative body radiotherapy (SABR) for recurrent renal cell carcinoma (RCC) after thermal ablation (TA).

MATERIALS AND METHODS

This study was a multi-institutional retrospective analysis of patients with recurrent RCC following TA who received SABR between 2016 and 2020. The primary study outcome was freedom from local failure, evaluated radiographically based on Response Evaluation Criteria in Solid Tumours (RECIST) v1.1. Distant failure, cancer-specific survival (CSS), overall survival (OS), treatment-related toxicity and renal function changes following SABR were the secondary outcomes. The Kaplan-Meier method was used to estimate freedom from local and distant failure, CSS and OS.

RESULTS

Seventeen patients with 18 biopsy-confirmed RCCs were included, with a median (interquartile range [IQR]) age at time of SABR of 75.2 (72.6-68.7) years, a median (IQR) tumour size of 3.5 (1.9-4.1) cm and follow-up (reverse Kaplan-Meier method) of 3.36 (95% confidence interval [CI] 1.6-4.1) years. Six of the 17 patients had a solitary kidney. Five patients had failed repeat TA prior to SABR. The median (IQR) time from TA procedure to SABR was 3.03 (1.5-5.1) years. No patient experienced local progression, with a local control rate of 100%. Four patients, two with baseline metastatic disease, experienced distant progression. The distant progression-free survival, CSS and OS at 3 years were 72.1% (95% CI 51.9%-100%), 92.3% (95% CI 78.9%-100%) and 82.1% (95% CI 62.1%-100%), respectively. The median (IQR) glomerular filtration rate before SABR was 58 (40-71) mL/min, and at last follow-up, it was 48 (33-57) mL/min. No patient experienced grade 3+ toxicity or went on to develop end-stage renal disease.

CONCLUSION

The results showed that SABR appears to be an effective and safe salvage strategy in patients with recurrent RCC following TA.

Stereotactic ablative radiotherapy for primary kidney cancer - An international patterns of practice survey

Purpose

To conduct an international survey of radiation oncologists treating primary renal cell carcinoma (RCC) with SABR to ascertain the general patterns of SABR use, common dose/treatment/follow-up details, and expected outcomes.

Materials and methods

A 51-question survey was created containing the following themes: prevalence and clinical scenarios in which RCC SABR is used, dose-fractionation schedules, treatment delivery details, follow-up/outcome assessments, and implementation barriers. The survey was distributed widely across multiple influential radiation oncology societies and social media, and ran from January to April 2023.

Results

A total of 255 respondents participated, mostly from academic centers within Europe/North America. Of these, 40 % (n = 102) currently offer SABR (50 % having begun within the last 3 years). Common barriers in non-users included lack of referrals by urologists and lack of supportive practice guidelines. Of respondents who do offer SABR, 77 % treat both small (4 cm or less) and large (>4 cm) renal masses. Dose-fractionation strategies varied from 27-52 Gy (3-5 fractions) for multifraction regimens, and 15-34 Gy for single fractions. Apart from treatment for medically inoperable disease, scenarios in which SABR was likely to be offered were for recurrence post surgery/thermal ablation and for oligometastatic kidney lesions. Uncommon scenarios included RCC with renal vein/inferior vena cava thrombosis, and as cytoreductive therapy in metastatic RCC. Expected local control outcomes were generally above 70 %, higher for small versus large renal masses.

Conclusions

SABR is a relatively newer indication for primary RCC, offered by less than 50% of respondents, with both consistent and variable practice patterns observed.

Stereotactic Body Radiation Therapy for Primary Renal Cell Carcinoma: A Case-Based Radiosurgery Society Practice Guide

Traditionally, renal cell carcinoma (RCC) was considered a radioresistant tumor, thereby limiting definitive radiation therapy management options. However, several recent studies have demonstrated that stereotactic body radiation therapy (SBRT) can achieve high rates of local control for the treatment of primary RCC. In the setting of expanding use of SBRT for primary RCC, it is crucial to provide guidance on practical considerations such as patient selection, fractionation, target delineation, and response assessment. This is particularly important in challenging scenarios where a paucity of evidence exists, such as in patients with a solitary kidney, bulky tumors, or tumor thrombus. The Radiosurgery Society endorses this case-based guide to provide a practical framework for delivering SBRT to primary RCC, exemplified by 3 cases. This article explores topics of tumor size and dose fractionation, impact on renal function and treatment in the setting of a solitary kidney, and radiation's role in the management of inferior vena cava tumor thrombus. Additionally, we review existing evidence and expert opinion on target delineation, advanced techniques such as magnetic resonance imaging guided SBRT, and SBRT response assessment.

Stereotactic Body Therapy for Urologic Cancers-What the Urologist Needs to Know

BACKGROUND

stereotactic ablative body radiotherapy (SABR) is a disruptive radiation therapy technique which is increasingly used for the treatment of urologic cancers. The aim of this narrative review is to provide an overview on the current landscape of SABR in urologic cancers and highlight advancements on the horizon.

METHODS

a narrative review of the contemporary role of SABR in urologic cancers is conducted.

RESULTS

in localised prostate cancer, SABR boasts excellent tumour control and biochemical control, with acceptable GU and GI toxicity. Its comparison to laparoscopic radical prostatectomy is currently ongoing. SABR appears to be practical for metastasis-directed therapy in metastatic prostate cancer, with good local control and a low toxicity profile, either alone or in combination with ADT. In localised RCC, SABR offers adequate local control with a modest impact on renal function in patients unfit for surgical management. Its role in metastatic RCC is much more established, where it has been shown to be superior to conventional radiotherapy. Emerging evidence suggests that SABR has a role in delaying systemic therapy whilst maintaining QOL and overall survival. Intriguingly, in metastatic prostate cancer and metastatic RCC, SABR results in a cytoreductive and immunomodulatory 'abscopal effect', a focus of current investigations.

CONCLUSIONS

SABR has emerged as a safe, effective, and feasible treatment for urologic cancers. Urologists should be aware of its increasing use in localised prostate cancer and metastatic RCC, with good oncological outcomes combined with acceptable toxicity. In addition, SABR holds promise for both metastatic prostate cancer and localised RCC treatment in terms of toxicity and oncological outcomes.

Evaluation of Volumetric Response Assessment From SABR for Renal Cell Carcinoma

PURPOSE

SABR is increasingly used to treat renal cell carcinoma (RCC). However, the optimal method to assess treatment response is unclear. We aimed to quantify changes in both volume and maximum linear size of tumors after SABR and evaluate the utility of the 2 approaches in treatment response assessment.

METHODS AND MATERIALS

We retrospectively studied patients with RCC treated with SABR at our institution between 2013 and 2020. All available follow-up computed tomography scans were aligned, and tumors were contoured on all scans. Volume and maximum linear size were measured at each follow-up, relative to these measurements at the time of computed tomography simulation.

RESULTS

Twenty-four patients with 25 tumors were included. Median follow-up was 32 months (range, 16-67). Nineteen tumors (76%) had 30% volumetric response at a median time of 7 months after SABR, and 12 tumors (48%) had 30% decrease in maximum linear size at a median time of 16 months. Eighteen tumors (72%) decreased in volume on first follow-up scan and continued to shrink, and 5 tumors (20%) displayed transient growth after SABR (average 24% increase in volume). Compared with T1a tumors, T1b or larger tumors were more likely to have transient growth (8% vs 33%; P = .16) and had higher average relative volume 24 months after SABR (0.47 vs 0.8; P = .022).

CONCLUSIONS

Volume measurement results in more pronounced and earlier change compared with linear size measurement when assessing response to SABR. These findings may provide guidance when assessing treatment response for patients with RCC treated with SABR.

Delta radiomics to track radiation response in lung tumors receiving stereotactic magnetic resonance-guided radiotherapy

Background and purpose

Lung cancer is a leading cause of cancer-related mortality, and stereotactic body radiotherapy (SBRT) has become a standard treatment for early-stage lung cancer. However, the heterogeneous response to radiation at the tumor level poses challenges. Currently, standardized dosage regimens lack adaptation based on individual patient or tumor characteristics. Thus, we explore the potential of delta radiomics from on-treatment magnetic resonance (MR) imaging to track radiation dose response, inform personalized radiotherapy dosing, and predict outcomes.

Materials and methods

A retrospective study of 47 MR-guided lung SBRT treatments for 39 patients was conducted. Radiomic features were extracted using Pyradiomics, and stability was evaluated temporally and spatially. Delta radiomics were correlated with radiation dose delivery and assessed for associations with tumor control and survival with Cox regressions.

Results

Among 107 features, 49 demonstrated temporal stability, and 57 showed spatial stability. Fifteen stable and non-collinear features were analyzed. Median Skewness and surface to volume ratio decreased with radiation dose fraction delivery, while coarseness and 90th percentile values increased. Skewness had the largest relative median absolute changes (22 %-45 %) per fraction from baseline and was associated with locoregional failure (p = 0.012) by analysis of covariance. Skewness, Elongation, and Flatness were significantly associated with local recurrence-free survival, while tumor diameter and volume were not.

Conclusions

Our study establishes the feasibility and stability of delta radiomics analysis for MR-guided lung SBRT. Findings suggest that MR delta radiomics can capture short-term radiographic manifestations of the intra-tumoral radiation effect.

Dose-response of localized renal cell carcinoma after stereotactic body radiation therapy: A meta-analysis

BACKGROUND

Stereotactic ablative radiation therapy (SBRT) is an emerging treatment option for primary renal cell carcinoma (RCC), particularly in patients who are unsuitable for surgery. The aim of this review is to assess the effect of increasing the biologically equivalent dose (BED) via various radiation fractionation regimens on clinical outcomes.

METHODS

A literature search was conducted in PubMed (Medline), EMBASE, and the Cochrane Library for studies published up to October 2023. Studies reporting on patients with localized RCC receiving SBRT were included to determine its effectiveness on local control, progression-free survival, and overall survival. A random effects model was used to meta-regress clinical outcomes relative to the BED for each study and heterogeneity was assessed by I2.

RESULTS

A total of 724 patients with RCC from 22 studies were included, with a mean age of 72.7 years (range: 44.0-81.0). Local control was excellent with an estimate of 99 % (95 %CI: 97-100 %, I2 = 19 %), 98 % (95 %CI: 96-99 %, I2 = 8 %), and 94 % (95 %CI: 90-97 %, I2 = 11 %) at one year, two years, and five years respectively. No definitive association between increasing BED and local control, progression-free survival and overall survival was observed. No publication bias was observed.

CONCLUSIONS

A significant dose response relationship between oncological outcomes and was not identified, and excellent local control outcomes were observed at the full range of doses. Until new evidence points otherwise, we support current recommendations against routine dose escalation beyond 25-26 Gy in one fraction or 42-48 Gy in three fractions, and to consider de-escalation or compromising target coverage if required to achieve safe organ at risk doses.

Stereotactic body radiotherapy for primary renal cell carcinoma: a systematic review and practice guideline from the International Society of Stereotactic Radiosurgery (ISRS)

Surgery is the standard of care for patients with primary renal cell carcinoma. Stereotactic body radiotherapy (SBRT) is a novel alternative for patients who are medically inoperable, technically high risk, or who decline surgery. Evidence for using SBRT in the primary renal cell carcinoma setting is growing, including several rigorously conducted prospective clinical trials. This systematic review was performed to assess the safety and efficacy of SBRT for primary renal cell carcinoma. Review results then formed the basis for the practice guidelines described, on behalf of the International Stereotactic Radiosurgery Society. 3972 publications were screened and 36 studies (822 patients) were included in the analysis. Median local control rate was 94·1% (range 70·0-100), 5-year progression-free survival was 80·5% (95% CI 72-92), and 5-year overall survival was 77·2% (95% CI 65-89). These practice guidelines addressed four key clinical questions. First, the optimal dose fractionation was 25-26 Gy in one fraction, or 42-48 Gy in three fractions for larger tumours. Second, routine post-treatment biopsy is not recommended as it is not predictive of patient outcome. Third, SBRT for primary renal cell carcinoma in a solitary kidney is safe and effective. Finally, guidelines for post-treatment follow-up are described, which include cross-axial imaging of the abdomen including both kidneys, adrenals, and surveillance of the chest initially every 6 months. This systematic review and practice guideline support the practice of SBRT for primary renal cell carcinoma as a safe and effective standard treatment option. Randomised trials with surgery and invasive ablative therapies are needed to further define best practice.

Incorporating Stereotactic Ablative Radiotherapy into the Multidisciplinary Management of Renal Cell Carcinoma

Stereotactic ablative radiotherapy (SABR) has challenged the conventional wisdom surrounding the radioresistance of renal cell carcinoma (RCC). In the past decade, there has been a significant accumulation of clinical data to support the safety and efficacy of SABR in RCC. Herein, we review the use of SABR across the spectrum of RCC. We performed an online search of the Pubmed database from January 1990 through April 2023. Studies of SABR/stereotactic radiosurgery targeting primary, extracranial, and intracranial metastatic RCC were included. For SABR in non-metastatic RCC, this includes its use in small renal masses, larger renal masses, and inferior vena cava tumor thrombi. In the metastatic setting, SABR can be used at diagnosis, for oligometastatic and oligoprogressive disease, and for symptomatic reasons. Notably, SABR can be used for both the primary renal tumor and metastasis-directed therapy. Management of RCC is evolving rapidly, and the role that SABR will have in this landscape is being assessed in a number of ongoing prospective clinical trials. The objective of this narrative review is to summarize the evidence corroborating the use of SABR in RCC.

Treatment Landscape of Renal Cell Carcinoma

OPINION STATEMENT

The treatment landscape of renal cell carcinoma (RCC) has evolved significantly over the past three decades. Active surveillance and tumor ablation are alternatives to extirpative therapy in appropriately selected patients. Stereotactic body radiation therapy (SBRT) is an emerging noninvasive alternative to treat primary RCC tumors. The advent of immune checkpoint inhibitors (ICIs) has greatly improved the overall survival of advanced RCC, and now the ICI-based doublet (dual ICI-ICI doublet; or ICI in combination with a vascular endothelial growth factor tyrosine kinase inhibitor, ICI-TKI doublet) has become the standard frontline therapy. Based on unprecedented outcomes in the metastatic with ICIs, they are also being explored in the neoadjuvant and adjuvant setting for patients with high-risk disease. Adjuvant pembrolizumab has proven efficacy to reduce the risk of RCC recurrence after nephrectomy. Historically considered a radioresistant tumor, SBRT occupies an expanding role to treat RCC with oligometastasis or oligoprogression in combination with systemic therapy. Furthermore, SBRT is being investigated in combination with ICI-doublet in the advanced disease setting. Lastly, given the treatment paradigm is shifting to adopt ICIs at earlier disease course, the prospective studies guiding treatment sequencing in the post-ICI setting is maturing. The effort is ongoing in search of predictive biomarkers to guide optimal treatment option in RCC.

Clinical outcomes of MR-guided adrenal stereotactic ablative radiotherapy with preferential sparing of organs at risk

Background and purpose

The optimal stereotactic ablative radiotherapy (SABR) doses for adrenal tumors are unknown. Some trials have specified that organ at risk (OAR) dose constraints should take priority over target coverage. We performed a retrospective review of the outcomes of MR-guided adrenal SABR (MRgRT) delivered with OAR sparing.

Materials and methods

Patients who underwent adrenal MRgRT between 2016 and 2023 were identified from our Ethics-approved institutional database. Dose ranged between 8 and 24 Gy per fraction, delivered in 1-5 fractions. A 3 mm margin was added to the breath-hold gross tumor volume (GTV) to derive a PTV. Plan were delivered to an 'optimized' PTV that was generated by excluding any overlap with OARs.

Results

Adrenal SABR was performed in 107 patients (114 metastases). The commonest scheme used 5 fractions of 10 Gy (53.5 %); 82 % of plans delivered a BED10 ≧ 80 Gy. Systemic therapy was administered within 3 months preceding or following SABR in 53.5 % of patients. Grade 3 acute toxicity (CTCAE v5.0) occurred in 0.9 % of patients, and 4.4 % reported late toxicity, consisting of adrenal insufficiency and a vertebral collapse. Median follow-up was 13.8 months (range, 0.0-73.4 months). Local progression occurred in 7.4 % of evaluable patients. PTV underdosage was frequent, with a coverage compromise index (D99/prescription dose) of < 0.90 in 52 % of all plans. Recurrences were independent of the prescription doses.

Conclusion

MRgRT for adrenal metastases is well tolerated with high local control rates despite prioritizing OAR sparing over PTV coverage. Studies using deformable dose accumulation may lead to a better understanding of dose-response relationship with adaptive SABR.

Phase 2 Trial of Stereotactic Ablative Radiotherapy for Patients with Primary Renal Cancer

BACKGROUND

Most renal cell carcinomas (RCCs) are localized and managed by active surveillance, surgery, or minimally invasive techniques. Stereotactic ablative radiation (SAbR) may provide an innovative non-invasive alternative although prospective data are limited.

OBJECTIVE

To investigate whether SAbR is effective in the management of primary RCCs.

DESIGN, SETTING, AND PARTICIPANTS

Patients with biopsy-confirmed radiographically enlarging primary RCC (≤5 cm) were enrolled. SAbR was delivered in either three (12 Gy) or five (8 Gy) fractions.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was local control (LC) defined as a reduction in tumor growth rate (compared with a benchmark of 4 mm/yr on active surveillance) and pathologic evidence of tumor response at 1 yr. Secondary endpoints included LC by the Response Evaluation Criteria in Solid Tumors (RECIST 1.1), safety, and preservation of kidney function. Exploratory tumor cell-enriched spatial protein and gene expression analysis were conducted on pre- and post-treatment biopsy samples.

RESULTS AND LIMITATIONS

Target accrual was reached with the enrollment of 16 ethnically diverse patients. Radiographic LC at 1 yr was observed in 94% of patients (15/16; 95% confidence interval: 70, 100), and this was accompanied by pathologic evidence of tumor response (hyalinization, necrosis, and reduced tumor cellularity) in all patients. By RECIST, 100% of the sites remained without progression at 1 yr. The median pretreatment growth rate was 0.8 cm/yr (interquartile range [IQR]: 0.3, 1.4), and the median post-treatment growth rate was 0.0 cm/yr (IQR: -0.4, 0.1, p < 0.002). Tumor cell viability decreased from 4.6% to 0.7% at 1 yr (p = 0.004). With a median follow-up of 36 mo for censored patients, the disease control rate was 94%. SAbR was well tolerated with no grade ≥2 (acute or late) toxicities. The average glomerular filtration rate declined from a baseline of 65.6 to 55.4 ml/min at 1 yr (p = 0.003). Spatial protein and gene expression analyses were consistent with the induction of cellular senescence by radiation.

CONCLUSIONS

This clinical trial adds to the growing body of evidence suggesting that SAbR is effective for primary RCC supporting its evaluation in comparative phase 3 clinical trials.

PATIENT SUMMARY

In this clinical trial, we investigated a noninvasive treatment option of stereotactic radiation therapy for the treatment of primary kidney cancer and found that it was safe and effective.

The Judicious Use of Stereotactic Ablative Radiotherapy in the Primary Management of Localized Renal Cell Carcinoma

Localized renal cell carcinoma is primarily managed surgically, but this disease commonly presents in highly comorbid patients who are poor operative candidates. Less invasive techniques, such as cryoablation and radiofrequency ablation, are effective, but require percutaneous or laparoscopic access, while generally being limited to cT1a tumors without proximity to the renal pelvis or ureter. Active surveillance is another management option for small renal masses, but many patients desire treatment or are poor candidates for active surveillance. For poor surgical candidates, a growing body of evidence supports stereotactic ablative radiotherapy (SABR) as a safe and effective non-invasive treatment modality. For example, a recent multi-institution individual patient data meta-analysis of 190 patients managed with SABR estimated a 5.5% five-year cumulative incidence of local failure with one patient experiencing grade 4 toxicity, and no other grade ≥3 toxic events. Here, we discuss the recent developments in SABR for the management of localized renal cell carcinoma, highlighting key concepts of appropriate patient selection, treatment design, treatment delivery, and response assessment.

First UK patient cohort treated with stereotactic ablative radiotherapy for primary kidney cancer

Aims

Stereotactic ablative radiotherapy (SABR) for primary renal cell carcinoma (RCC) is a promising non-invasive ablative treatment option. A prospective interventional clinical trial published showed that treatment was feasible and well tolerated. We present the first single-institution UK cohort of patients with primary RCC receiving protocol-based SABR with prospective follow-up. We also present a protocol that could be used to facilitate more widespread use of the treatment.

Materials and methods

Nineteen biopsy-proven primary RCC patients were treated with either 42 Gy in three fractions on alternate days or 26 Gy in a single fraction based on predefined eligibility criteria using either Linear Accelerator or CyberKnife platform. Prospective toxicity data using CTCAE V4.0 and outcome data such as estimated glomerular filtration rate (eGFR) and tumour response using CT thorax, abdomen and pelvis (CT-TAP) were collected at 6 weeks, 3, 6, 12, 18 and 24 months post treatment.

Results

The 19 patients had a median age of 76 years (interquartile range [IQR] 64-82 years) and 47.4% were males, and they had a median tumour size of 4.5 cm (IQR 3.8-5.2 cm). Single and fractionated treatment was well tolerated and there were no significant acute side effects. The mean drop from baseline in eGFR at 6 months was 5.4 ml/min and that at 12 months was 8.7 ml/min. The overall local control rate at both 6 and 12 months was 94.4%. Overall survival at 6 and 12 months was 94.7% and 78.3%, respectively. After a median follow-up of 17 months, three patients experienced a Grade 3 toxicity, which was resolved with conservative management.

Conclusion

SABR for primary RCC is a safe and feasible treatment for medically unfit patients, which can be delivered in most UK cancer centres using standard Linear Accelerator as well as CyberKnife platforms.

Stereotactic body radiation therapy to the kidney for metastatic renal cell carcinoma: A narrative review of an emerging concept

This narrative review provides a historical overview of cytoreductive nephrectomy for metastatic renal cell carcinoma (mRCC) and examines the safety and therapeutic potential of cytoreductive stereotactic body radiation therapy (SBRT) for mRCC in the modern immunotherapy era. In the last five years, the introduction of immune checkpoint inhibitors for the treatment of mRCC has improved outcomes for patients. This has brought forth new exploration of the role of CN in combination with immunotherapy. Early retrospective evidence suggests that there may be a benefit of deferred CN after immunotherapy (IOT) for de novo mRCC patients. However, there has also been concern regarding the feasibility of surgery after IOT due to inflammation. SBRT may be an appropriate alternative in these circumstances. Since 1999, cytoreductive SBRT has been used for inoperable primary RCC. Several prospective and retrospective studies treating the kidney tumor for localized RCC have shown that this technique is safe and produces favorable and durable local control. SBRT has also exhibited similar effectiveness to CN, while providing additional benefits including noninvasiveness and the ability to treat tumors that can't be treated with nephrectomy or ablation due to size or location. Furthermore, SBRT confers immunostimulatory effects, which are hypothesized to work synergistically with immunotherapy. Clinicians should consider SBRT a safe and reliable alternative to CN for RCC patients. Ongoing studies are exploring the utility of SBRT for treatment of the primary tumor in mRCC patients receiving standard of care immunotherapy.

Stereotactic Body Radiotherapy for Localized Kidney Cancer

PURPOSE OF REVIEW

Stereotactic body radiation therapy (SBRT) is increasingly utilized in the management of localized kidney cancers, particularly for patients who are not surgical candidates. Herein, we provide a narrative review of SBRT in the management of localized kidney cancers.

RECENT FINDINGS

Recent prospective studies and multi-institutional retrospective studies highlight the safety and efficacy of SBRT in the management of renal tumors, a disease previously thought to be radioresistant. Studies have shown that local control is greater than 90% with rare grade 3 or 4 toxicity and no grade 5 toxicity. SBRT can be utilized successfully in the treatment of large kidney tumors (> 5 cm). New techniques such as MRI-guided radiation therapy may further improve the therapeutic ratio. However, randomized clinical trials are necessary to confirm the optimal dosing schedule and compare outcomes with nephrectomy, which remains the standard of care in suitable patients. Advances in SBRT have made this modality a safe and effective treatment option in the management of localized kidney cancers.

Stereotactic Body Radiotherapy for Renal Cell Carcinoma in Patients with Von Hippel-Lindau Disease-Results of a Prospective Trial

Von Hippel-Lindau disease (VHL) is a hereditary disorder associated with malignant tumors including clear cell renal cell carcinoma (ccRCC). Partial nephrectomy is complicated by multilocular tumor occurrence and a high recurrence rate. The aim of this study was to evaluate the potential of stereotactic body radiotherapy (SBRT) as an alternative treatment approach in VHL patients with multiple ccRCC. Patients with VHL and a diagnosis of ccRCC were enrolled. SBRT was conducted using five fractions of 10 Gy or eight fractions of 7.5 Gy. The primary endpoint was local control (LC). Secondary endpoints included alteration of renal function and adverse events. Seven patients with a total of eight treated lesions were enrolled. Median age was 44 years. Five patients exhibited multiple bilateral kidney cysts in addition to ccRCC. Three patients underwent at least one partial nephrectomy in the past. After a median follow-up of 43 months, 2-year LC was 100%, while 2-year CSS, 2-year PFS and 2-year OS was 100%, 85.7% and 85.7%, respectively. SBRT was very well tolerated with no acute or chronic toxicities grade ≥ 2. Mean estimated glomerular filtration rate (eGFR) at baseline was 83.7 ± 13.0 mL/min/1.73 m2, which decreased to 76.6 ± 8.0 mL/min/1.73 m2 after 1 year. Although the sample size was small, SBRT resulted in an excellent LC rate and was very well tolerated with preservation of kidney function in patients with multiple renal lesions and cysts.

The Emerging Role of Radiation Therapy in Renal Cell Carcinoma

Advancements in radiation delivery technology have made it feasible to treat tumors with ablative radiation doses via stereotactic ablative radiation therapy (SAbR) at locations that were previously not possible. Renal cell cancer (RCC) was initially thought to be radioresistant, even considered toxic, in the era of conventional protracted course radiation. However, SAbR has been demonstrated to be safe and effective in providing local control to both primary and metastatic RCC by using ablative radiation doses. SAbR can be integrated with other local and systemic therapies to provide optimal management of RCC patients. We will discuss the rationale and available evidence for the integration and sequencing of SAbR with local and systemic therapies for RCC.

Imaging considerations for thermal and radiotherapy ablation of primary and metastatic renal cell carcinoma

Ablative (percutaneous and stereotactic) thermal and radiotherapy procedures for management of both primary and metastatic renal cell carcinoma are increasing in popularity in clinical practice. Data suggest comparable efficacy with lower cost and morbidity compared to nephrectomy. Ablative therapies may be used alone or in conjunction with surgery or chemotherapy for treatment of primary tumor and metastatic disease. Imaging plays a crucial role in pre-treatment selection and planning of ablation, intra-procedural guidance, evaluation for complications, short- and long-term post-procedural surveillance of disease, and treatment response. Treatment response and disease recurrence may differ considerably after ablation, particularly for stereotactic radiotherapy, when compared to conventional surgical and chemotherapies. This article reviews the current and emerging role of imaging for ablative therapy of renal cell carcinoma.

Role of Imaging in Renal Cell Carcinoma: A Multidisciplinary Perspective

With the expansion in cross-sectional imaging over the past few decades, there has been an increase in the number of incidentally detected renal masses and an increase in the incidence of renal cell carcinomas (RCCs). The complete characterization of an indeterminate renal mass on CT or MR images is challenging, and the authors provide a critical review of the best imaging methods and essential, important, and optional reporting elements used to describe the indeterminate renal mass. While surgical staging remains the standard of care for RCC, the role of renal mass CT or MRI in staging RCC is reviewed, specifically with reference to areas that may be overlooked at imaging such as detection of invasion through the renal capsule or perirenal (Gerota) fascia. Treatment options for localized RCC are expanding, and a multidisciplinary group of experts presents an overview of the role of advanced medical imaging in surgery, percutaneous ablation, transarterial embolization, active surveillance, and stereotactic body radiation therapy. Finally, the arsenal of treatments for advanced renal cancer continues to grow to improve response to therapy while limiting treatment side effects. Imaging findings are important in deciding the best treatment options and to monitor response to therapy. However, evaluating response has increased in complexity. The unique imaging findings associated with antiangiogenic targeted therapy and immunotherapy are discussed. An invited commentary by Remer is available online. Online supplemental material is available for this article. ^©RSNA, 2021.

Patient-reported Quality of Life following Stereotactic Body Radiation Therapy for Primary Kidney Cancer - Results from a Prospective Cohort Study

AIMS

We report on the first prospective series of patient-reported quality of life (QoL) following stereotactic body radiation therapy (SBRT) for primary kidney cancer.

MATERIALS AND METHODS

Patients were treated on a multi-institutional prospective cohort study with 30-42 Gy SBRT in three or five fractions. QoL assessments were carried out using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core-15 Palliative (EORTC-QLQ-C15-PAL), the Functional Assessment of Cancer Therapy-Kidney Symptom Index-19 (FACT FKSI-19) and the EuroQol-5D-3L tools at baseline, 1 week, and 1, 3 and 6 months post-treatment. QoL over time was analysed using linear mixed modelling, pairwise and anchor-based analyses.

RESULTS

Twenty-eight patients were included. No significant reduction in any QoL metric was observed on repeated measures. However, a trend to reduced EORTC global QoL and fatigue was observed at 1 week, with improvement over time in other symptom scores such as pain, appetite and nausea. On pairwise analysis, there were statistically significant reductions in global QoL at 1 week (with subsequent recovery) and dyspnoea at 6 months post-SBRT. Trends to improved pain, appetite and nausea were observed following SBRT. Less than half of patients reported stable or better EORTC global QoL at 1 week. For all other QoL and symptom scales, most patients had reported stable or better scores at all times, with a slight proportional improvement in emotional functioning, nausea, fatigue, pain and appetite, and a slight worsening of physical functioning and dyspnoea over time.

CONCLUSIONS

SBRT results in well-preserved QoL in the weeks to months following treatment for primary kidney cancer.

The Role of Daily Adaptive Stereotactic MR-Guided Radiotherapy for Renal Cell Cancer

Simple Summary

Standard treatment for localized renal cell carcinoma (RCC) is surgery. Stereotactic radiotherapy given in a few high dose fractions is a promising treatment for this indication and could be an alternative option for patients unsuitable for surgery. Stereotactic MR-guided radiotherapy (MRgRT) is clinically implemented as a new technique for precise treatment delivery of abdominal tumors, like RCC. In this study, we evaluated the clinical impact of stereotactic MRgRT given in five fractions of 8 Gy and routine plan re-optimization for 36 patients with large primary RCCs. Our evaluation showed good oncological results with minimal side-effects. Even in this group with large tumors, daily plan re-optimization was only needed in a minority of patients who can be identified upfront. This is a favorable result since online MRgRT plan adaptation is a time-consuming procedure. In these patients, MRgRT delivery will be faster, and these patients could be candidates for even less fractions per treatment.

Abstract

Novel magnetic-resonance-guided radiotherapy (MRgRT) permits real-time soft-tissue visualization, respiratory-gated delivery with minimal safety margins, and time-consuming daily plan re-optimisation. We report on early clinical outcomes of MRgRT and routine plan re-optimization for large primary renal cell cancer (RCC). Thirty-six patients were treated with MRgRT in 40 Gy/5 fractions. Prior to each fraction, re-contouring of tumor and normal organs on a pretreatment MR-scan allowed daily plan re-optimization. Treatment-induced toxicity and radiological responses were scored, which was followed by an offline analysis to evaluate the need for such daily re-optimization in 180 fractions. Mean age and tumor diameter were 78.1 years and 5.6 cm, respectively. All patients completed MRgRT with an average fraction duration of 45 min. Local control (LC) and overall survival rates at one year were 95.2% and 91.2%. No grade ≥3 toxicity was reported. Plans without re-optimization met institutional radiotherapy constraints in 83.9% of 180 fractions. Thus, daily plan re-optimization was required for only a minority of patients, who can be identified upfront by a higher volume of normal organs receiving 25 Gy in baseline plans. In conclusion, stereotactic MRgRT for large primary RCC showed low toxicity and high LC, while daily plan re-optimization was required only in a minority of patients.

Proton Therapy for Primary Renal Cell Carcinoma: The First Nationwide Retrospective Study in Japan

BACKGROUND/AIM

This multi-institutional study aimed to investigate the efficacy and feasibility of proton beam therapy (PBT) for renal cell carcinoma (RCC) in Japan.

PATIENTS AND METHODS

The survival, local control, and toxicities in 22 RCC patients treated between 2001 and 2016 at 6 Japanese PBT institutes were analyzed.

RESULTS

The 22 patients comprised 20 men and had a median age of 67 (range=42-88) years. The total irradiation dose was 60-79.6 Gy (relative biological effectiveness). Over a median follow-up of 37 months, the 3-year overall and disease-specific survival rates were 95% and 100%, respectively, and no recurrence occurred. No patient experienced grade 3 or higher adverse events. The serum blood urea nitrogen (p=0.25) and creatinine levels (p=0.95) were not significantly affected, although the mean estimated glomerular filtration rate was reduced by 7.1±11.2 ml/min/1.73 m² Conclusion: Despite the small number of patients, high-dose PBT can control RCC while maintaining their renal function with high probability, and could be and alternative curative therapy especially for inoperable patients.

Adaptive radiosurgery based on two simultaneous dose prescriptions in the management of large renal cell carcinoma brain metastases in critical areas: Towards customization

Background:

The long-term benefits of local therapy in metastatic renal cell carcinoma (mRCC) have been widely documented. In this context, single fraction gamma knife radiosurgery (SF-GKRS) is routinely used in the management of brain metastases. However, SF-GKRS is not always feasible due to volumetric and regional constraints. We intend to illustrate how a dose-volume adaptive hypofractionated GKRS technique based on two concurrent dose prescriptions termed rapid rescue radiosurgery (RRR) can be utilized in this particular scenario.

Case Description:

A 56-year-old man presented with left-sided hemiparesis; the imaging showed a 13.1 cc brain metastasis in the right central sulcus (Met 1). Further investigation confirmed the histology to be a metastatic clear cell RCC. Met 1 was treated with upfront RRR. Follow-up magnetic resonance imaging (MRI) at 10 months showed further volume regression of Met 1; however, concurrently, a new 17.3 cc lesion was reported in the boundaries of the left frontotemporal region (Met 2) as well as a small metastasis (<1 cc) in the left temporal lobe (Met 3). Met 2 and Met 3 underwent RRR and SF-GKRS, respectively.

Results:

Gradual and sustained tumor ablation of Met 1 and Met 2 was demonstrated on a 20 months long follow- up. The patient succumbed to extracranial disease 21 months after the treatment of Met 1 without evidence of neurological impairment post-RRR.

Conclusion:

Despite poor prognosis and precluding clinical factors (failing systemic treatment, eloquent location, and radioresistant histology), RRR provided optimal tumor ablation and salvage of neurofunction with limited toxicity throughout follow-up.

Combination with Stereotactic Body Radiotherapy Offers a Promising Strategy to Overcome Resistance to Immunotherapy in Advanced Renal Cell Cancer

Immunotherapy for renal cell cancer (RCC) has witnessed several developments for more than two decades. Checkpoint inhibitors, including anti-CTLA-4 and anti-PD-1/PD-L1 blockers, have changed the treatment landscape for patients with advanced RCC in the past 3 years. Despite these advances, more than 55% RCC patients become resistant to different immunotherapies without other treatment combination. Among various attempts at overcoming resistance to immunotherapy, stereotactic body radiotherapy (SBRT) has been found to potentiate the activity of immunotherapy agents through several potential mechanisms, including normalization of microvessels to alleviate tumor hypoxia, improvement in efficient delivery of drugs, abundant neoantigen exposure, and recruitment of antitumor immune cells to alter the immunosuppressive tumor microenvironment. Preclinical studies and clinical case reports have predicted that the combination of SBRT, an immunotherapy, may lead to remarkable results. This review aims to provide the biological basis for the feasibility of combining SBRT to overcome immunotherapy resistance and to review the currently available clinical evidence of this combination therapy in patients with advanced RCC.

Robotic stereotactic ablative radiotherapy for renal cell carcinoma in patients with impaired renal function

Background

Robotic stereotactic ablative radiotherapy (SABR) is currently under investigation as a noninvasive treatment option for patients with renal cell carcinoma (RCC). For radiation therapy of RCC, tumor motion and the need for high ablative doses while preserving the remaining renal parenchyma is a challenge. We aimed to analyze the safety and efficacy of robotic radiosurgery in RCC in a specific difficult subgroup of patients with impaired renal function.

Methods

We retrospectively identified all patients with RCC, treated with robotic SABR and motion compensation in our institution between 2012 and 2017. Either single fraction SABR of 24 or 25 Gy or 3 fractions of 12 Gy prescribed to the 70% isodose line was applied. Local control, overall survival, radiation side effects were evaluated together with renal function and tumor motion.

Results

We analyzed data of 13 lesions treated in 10 patients with clear cell RCC and a mean age of 70.5 ± 13.6 years (range: 48–87). Prior to SABR, 8 patients underwent previous complete and/or partial nephrectomy, 7 patients presented with chronic kidney disease ≥ stage 3. The median of minimum, mean and maximum planning target volume doses were 23.2, 29.5 and 35.0 Gy for single fraction and 24.4, 42.5 and 51.4 Gy for the three fractions regime. Persistent local control by robotic SABR was achieved in 9 out of 10 patients (92.3% of all lesions) within a median follow-up period of 27 month (range: 15–54). One patient underwent nephrectomy due to progressive disease and sufficient renal function of the contralateral kidney. Renal function remained stable with a mean estimated glomerular filtration rate (eGFR) of 51.3 ± 19.7 ml/min at baseline and 51.6 ± 25.8 ml/min at follow-up. The largest respiratory-induced tumor motion was seen in superior-inferior direction, compensated by the CyberKnife with mean targeting errors of maximal 2.2 mm.

Conclusions

Robotic SABR is technically feasible for the treatment of RCC in preexisting kidney disease with good local tumor control at about 2 years follow-up. Robotic SABR with motion tracking offers a valid treatment option for patients, who are at increased risk for progression to end-stage renal disease due to partial nephrectomy or ablative techniques.

Is there a role for stereotactic radiotherapy in the treatment of renal cell carcinoma?

Renal cell carcinoma (RCC) has traditionally been regarded as radioresistant tumor based on preclinical data and negative clinical trials using conventional fractionated radiotherapy. However, there is emerging evidence that radiotherapy delivered in few fractions with high single-fraction and total doses may overcome RCC s radioresistance. Stereotactic radiotherapy (SRT) has been successfully used in the treatment of intra- and extracranial RCC metastases showing high local control rates accompanied by low toxicity. Although surgery is standard of care for non-metastasized RCC, a significant number of patients is medically inoperable or refuse surgery. Alternative local approaches such as radiofrequency ablation or cryoablation are invasive and often restricted to small RCC, so that there is a need for alternative local therapies such as stereotactic body radiotherapy (SBRT). Recently, both retrospective and prospective trials demonstrated that SBRT is an attractive treatment alternative for localized RCC. Here, we present a comprehensive review of the published data regarding SBRT for primary RCC. The radiobiological rationale to use higher radiation doses in few fractions is discussed, and technical aspects enabling the safe delivery of SBRT despite intra- and inter-fraction motion and the proximity to organs at risk are outlined.

Imaging Advances in the Management of Kidney Cancer

New developments in cross-sectional imaging, including contrast-enhanced ultrasound, dual-energy computed tomography, multiparametric magnetic resonance imaging, single-photon emission computed tomography, and positron emission tomography, together with novel application of existing and novel radiotracers, have changed the landscape of renal mass characterization (ie, virtual biopsy) as well as the detection of metastatic disease, prognostication, and response assessment in patients with advanced kidney cancer. A host of imaging response criteria have been developed to characterize the response to targeted and immune therapies and correlate with patient outcomes, each with strengths and limitations. Recent efforts to advance the field are aimed at increasing objectivity with quantitative techniques and the use of banks of imaging data to match the vast genomic data that are becoming available. The emerging field of radiogenomics has the potential to transform further the role of imaging in kidney cancer management through eventual noninvasive characterization of the tumor histology and genetic microenvironment in single renal masses and/or metastatic disease. We review of the effect of currently available imaging techniques in the management of patients with kidney cancer, including localized, locally advanced, and metastatic disease.

Diffusion weighted and dynamic contrast enhanced MRI as an imaging biomarker for stereotactic ablative body radiotherapy (SABR) of primary renal cell carcinoma

Purpose

To explore the utility of diffusion and perfusion changes in primary renal cell carcinoma (RCC) after stereotactic ablative body radiotherapy (SABR) as an early biomarker of treatment response, using diffusion weighted (DWI) and dynamic contrast enhanced (DCE) MRI.

Methods

Patients enrolled in a prospective pilot clinical trial received SABR for primary RCC, and had DWI and DCE MRI scheduled at baseline, 14 days and 70 days after SABR. Tumours <5cm diameter received a single fraction of 26 Gy and larger tumours received three fractions of 14 Gy. Apparent diffusion coefficient (ADC) maps were computed from DWI data and parametric and pharmacokinetic maps were fitted to the DCE data. Tumour volumes were contoured and statistics extracted. Spearman’s rank correlation coefficients were computed between MRI parameter changes versus the percentage tumour volume change from CT at 6, 12 and 24 months and the last follow-up relative to baseline CT.

Results

Twelve patients were eligible for DWI analysis, and a subset of ten patients for DCE MRI analysis. DCE MRI from the second follow-up MRI scan showed correlations between the change in percentage voxels with washout contrast enhancement behaviour and the change in tumour volume (ρ = 0.84, p = 0.004 at 12 month CT, ρ = 0.81, p = 0.02 at 24 month CT, and ρ = 0.89, p = 0.001 at last follow-up CT). The change in mean initial rate of enhancement and mean Ktrans at the second follow-up MRI scan were positively correlated with percent tumour volume change at the 12 month CT onwards (ρ = 0.65, p = 0.05 and ρ = 0.66, p = 0.04 at 12 month CT respectively). Changes in ADC kurtosis from histogram analysis at the first follow-up MRI scan also showed positive correlations with the percentage tumour volume change (ρ = 0.66, p = 0.02 at 12 month CT, ρ = 0.69, p = 0.02 at last follow-up CT), but these results are possibly confounded by inflammation.

Conclusion

DWI and DCE MRI parameters show potential as early response biomarkers after SABR for primary RCC. Further prospective validation using larger patient cohorts is warranted.

Pooled analysis of stereotactic ablative radiotherapy for primary renal cell carcinoma: A report from the International Radiosurgery Oncology Consortium for Kidney (IROCK)

BACKGROUND

Stereotactic ablative radiotherapy (SABR) is an emerging therapy for primary renal cell carcinoma. The authors assessed safety, efficacy, and survival in a multi-institutional setting. Outcomes between single-fraction and multifraction SABR were compared.

METHODS

Individual patient data sets from 9 International Radiosurgery Oncology Consortium for Kidney institutions across Germany, Australia, the United States, Canada, and Japan were pooled. Toxicities were recorded using Common Terminology Criteria for Adverse Events, version 4.0. Patient, tumor, and treatment characteristics were stratified according to the number of radiotherapy fractions (single vs multiple). Survival outcomes were examined using Kaplan-Meier estimates and Cox proportional-hazards regression.

RESULTS

Of 223 patients, 118 received single-fraction SABR, and 105 received multifraction SABR. The mean patient age was 72 years, and 69.5% of patients were men. There were 83 patients with grade 1 and 2 toxicity (35.6%) and 3 with grade 3 and 4 toxicities (1.3%). The rates of local control, cancer-specific survival, and progression-free survival were 97.8%, 95.7%, and 77.4%, respectively, at 2 years; and they were 97.8%, 91.9%, and 65.4%, respectively, at 4 years. On multivariable analysis, tumors with a larger maximum dimension and the receipt of multifraction SABR were associated with poorer progression-free survival (hazard ratio, 1.16 [P < .01] and 1.13 [P = .02], respectively) and poorer cancer-specific survival (hazard ratio, 1.28 [P < .01] and 1.33 [P = .01], respectively). There were no differences in local failure between the single-fraction cohort (n = 1) and the multifraction cohort (n = 2; P = .60). The mean ( ± standard deviation) estimated glomerular filtration rate at baseline was 59.9 ± 21.9 mL per minute, and it decreased by 5.5 ± 13.3 mL per minute (P < .01).

CONCLUSIONS

SABR is well tolerated and locally effective for treating patients who have primary renal cell carcinoma and has an acceptable impact on renal function. An interesting observation is that patients who receive single-fraction SABR appear to be less likely to progress distantly or to die of cancer. Cancer 2018;124:934-42. © 2017 American Cancer Society.

Renal Cell Carcinoma: Alternative Nephron-Sparing Treatment Options for Small Renal Masses, a Systematic Review

BACKGROUND

The standard treatment of T1 renal cell carcinoma (RCC) is (partial) nephrectomy. For patients where surgery is not the treatment of choice, for example in the elderly, in case of severe comorbidity, inoperability, or refusal of surgery, alternative treatment options are available. These treatment options include active surveillance (AS), radiofrequency ablation (RFA), cryoablation (CA), microwave ablation (MWA), or stereotactic body radiotherapy (SBRT). In the present overview, the efficacy, safety, and outcome of these different options are summarized, particularly focusing on recent developments.

MATERIALS AND METHODS

Databases of MEDLINE (through PubMed), EMBASE, and the Cochrane Library were systematically searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The search was performed in December 2016, and included a search period from 2010 to 2016. The terms and synonyms used were renal cell carcinoma, active surveillance, radiofrequency ablation, microwave ablation, cryoablation and stereotactic body radiotherapy.

RESULTS

The database search identified 2806 records, in total 73 articles were included to assess the rationale and clinical evidence of alternative treatment modalities for small renal masses. The methodological quality of the included articles varied between level 2b and level 4.

CONCLUSION

Alternative treatment modalities, such as AS, RFA, CA, MWA, and SBRT, are treatment options especially for those patients who are unfit to undergo an invasive treatment. There are no randomized controlled trials available comparing surgery and less invasive modalities, leading to a low quality on the reported articles. A case-controlled registry might be an alternative to compare outcomes of noninvasive treatment modalities in the future.

Stereotactic ablative radiation therapy in renal cell carcinoma: From oligometastatic to localized disease

Renal Cell Carcinoma (RCC) has historically been considered a radioresistant cancer, and radiotherapy was usually delivered with a palliative goal. Stereotactic ablative radiotherapy (SABR) allows the delivery of high doses on small treatment volumes in a safe and effective way, thus opening the doors to new applicationsof radiotherapy both in the treatment of the primary and oligometastasic disease. Aim of the current review is to explore the state of art of SABR in the therapeutic approach to RCC.

Radiotherapy for renal cell carcinoma: renaissance of an overlooked approach

Conventional radiotherapy previously had a limited role in the definitive treatment of renal cell carcinoma (RCC), owing to the disappointing outcomes of several trials and the perceived radioresistance of this type of cancer. In this context, radiotherapy has been relegated largely to the palliation of symptoms in patients with metastatic disease, with variable rates of response. Following the availability of newer technologies that enable safe delivery of high-dose radiotherapy, stereotactic ablative radiotherapy (SABR) has become increasingly used in patients with RCC. Preclinical evidence demonstrates that RCC cells are sensitive to ablative doses of radiotherapy (≥8-10 Gy). Trials in the setting of intracranial and extracranial oligometastases, as well as primary RCC, have demonstrated excellent tumour control using this approach. Additionally, an awareness of the capacity of high-dose radiation to stimulate antitumour immunity has resulted in novel combinations of SABR with immunotherapies. Here we describe the historical application of conventional radiotherapy, the current biological understanding of the effects of radiation, and the clinical evidence supporting the use of ablative radiotherapy in RCC. We also explore emerging opportunities to combine systemic targeted agents or immunotherapies with radiation. Radiotherapy, although once an overlooked approach, is moving towards the forefront of RCC treatment.