Stereotactic Ablative Body Radiotherapy for Primary Renal Cell Carcinoma in Non-surgical Candidates: Initial Clinical Experience

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.

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.

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.

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.

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 inoperable patients with renal carcinoma

INTRODUCTION

The objective of this study was to analyze the dose-dependent safety profiles of stereotactic body radiation therapy (SBRT) in patients with inoperable small renal cell carcinoma (RCC).

MATERIAL

This is a retrospective study from a single institution including patients with RCC treated between 2011 and 2020 with SBRT on the primary tumor or on a local recurrence after surgery. All patients had been declared inoperable or refused surgery. The patients were divided into two dose level groups: group 1 (BED10<60Gy) and group 2 (BED10≥60Gy). Acute and late toxicities, renal function and local control (LC) were compared between the two groups.

RESULTS

A total of 24 patients were analyzed with an average follow-up of 25.1 months. Nine patients (37%) and three patients (14%) reported grade 1-2 acute and late toxicities, respectively. No grade≥3 acute and late toxicities were observed. There was no significant difference in acute and late toxicities between the two groups (P=0.21 and P=0.27, respectively). There was no significant difference in estimated glomerular filtration rate in the 15 patients, eligible for renal toxicity analysis between the pre-radiation and the 12-month follow-up (P=0.1) and the last follow-up (P=0.06). LC at the last follow-up was noted in 19 out of 23 patients (83%) and was based on imaging acquisition. LC was 77.8% for group 1 and 85.7% for group 2 (P=1.95).

CONCLUSION

Dose escalation was not associated with an increase in acute and late grade≥2 toxicities. There appears to be a trend towards increased LC at higher 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.

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 for kidney cancer. Where do we stand?

At present, surgery is still the gold standard for the local treatment of renal cancer. Nonetheless, in several clinical scenarios, stereotactic body radiation therapy (SBRT) also known as stereotactic ablative body radiotherapy (SABR) is emerging as a highly effective ablative technique in fragile patients and those with significant comorbidities, as well as in cases where percutaneous therapy (cryoablation or radiofrequency) is not viable. However, considering the intrinsic radioresistance of renal tumors, the optimal treatment schemes have not been established. In oligometastatic patients, it has been reported that the control of the oligometastases can be a potentially curable approach. Being a technique than can be administered exclusively or in combination with systemic therapy, treatment individualization based on patient characteristics is key. Another scenario under investigation is oligoprogression, where SBRT offers the possibility of delaying further lines of systemic therapy by eliminating subclones of resistant tumor with ablative doses, with the additional opportunity of stimulating the immune system (immunomodulatory role). In this review, we have conducted an analysis of recently published studies that test the role of this technique in different clinical scenarios of this disease. We have found promising results that make SBRT a potent therapeutic approach with low toxicity. We also comment on ongoing studies that will generate the necessary evidence needed for the implementation of this technique in our daily clinical practice.

Radiation Therapy in the Treatment of Localized and Advanced Renal Cancer

Renal cell carcinoma (RCC) has historically been considered resistant to radiotherapy. However, advances in the field of radiation oncology have led to safe delivery of higher radiation doses through the use of stereotactic body radiotherapy (SBRT) that have shown significant activity against RCC. SBRT has now been shown to be a highly effective modality for management of localized RCC for nonsurgical candidates. Increasing evidence also points to a role for SBRT in the management of oligometastatic RCC as a means for not only providing palliation but prolonging time to progression and potentially improving survival.

Prognostic impact of biologically equivalent dose in stereotactic body radiotherapy for renal cancer

Purpose /Objectives Materials/Methods

The National Cancer Database (NCDB) was queried (2004-2017) for patients with RCC who did not have surgical resection but received definitive SBRT. Kaplan-Meier analysis with log-rank test was used to evaluate overall survival (OS). Univariable (UVA) and multivariable (MVA) analysis were conducted using cox proportional hazard models to determine prognostic factors for OS.

Results

A total of 344 patients with median age 77 (IQR 70-85) were included in this study. Median BED₃ was 180 Gy (IQR 126.03-233.97). Median OS was 90 months in the highest quartile compared to 36-52 months in the lower three quartiles (p < 0.01). On UVA, the highest BED₃ quartile was a positive prognostic factor (HR 0.67, p < 0.01 CI 0.51-0.91) while age, tumor size, T-stage, metastasis, renal pelvis location, and transitional cell histology were negative factors. On MVA, the highest BED₃ quartile was remained significant (HR 0.69, p = 0.02; CI 0.49-0.95) as a positive factor, while age, metastasis were negative factors.

Conclusion

Higher BED may be associated with improved OS. Prospective investigation is needed to clearly define optimal BED for SBRT used to treat RCC.

Stereotactic Body Radiotherapy for Kidney Cancer: Ready for Prime Time?

The standard treatment for renal cell carcinoma (RCC) is surgery. However, a number of patients will not be candidates for surgical treatment or will reject this therapeutic approach. Therefore, alternative approaches are required. Historically, radiotherapy has been considered an ineffective treatment for RCC due to the radioresistance of renal tumour cells to conventional fractionation and the increased rate of toxicity. Stereotactic body radiotherapy (SBRT) is a radiotherapy technique that provides a non-invasive ablative treatment with remarkable rates of local control in both primary tumours and metastases in several locations, with a low associated morbidity due to the highly conformal dose and the use of image-guided techniques. Current evidence shows that a higher dose per fraction, achieving a higher biological effective dose, can overcome the radioresistance of RCC cells. Therefore, SBRT, as well as the combination of SBRT and new emerging immune therapies, has a potential role in the local treatment of primary RCC and oligometastatic RCC patients.

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 Renal Cell Carcinoma: Oncological and Renal Function Outcomes

AIMS

To evaluate oncological and renal function outcomes of stereotactic body radiotherapy (SBRT) for medically inoperable patients with localised renal cell carcinoma.

MATERIALS AND METHODS

Consecutive patients treated with curative intent SBRT (30-45 Gy in five fractions or 42 Gy in three fractions) were included. Data on local control (Response Evaluation Criteria in Solid Tumors [RECIST] v1.1), distant metastasis, impact on estimated glomerular filtration rate (eGFR) and proportional ipsilateral and contralateral renal functions (measured through renal scans) were collected. Univariate and multivariable analyses were conducted to determine association of variables with oncological and renal function outcomes.

RESULTS

Seventy-four patients were analysed. The median follow-up was 27.8 months (interquartile range 17.6-41.7). Fifty-seven per cent had tumours ≥ T1b. One-, 2- and 4-year cumulative incidence of local failure was 5.85, 7.77 and 7.77%, respectively. The cumulative incidence of distant metastasis at 2 years was 4.24%. On multivariable analysis, a lower planning target volume (PTV) mean dose (P = 0.019) and a larger PTV (P = 0.005) were significantly associated with the risk of developing local failure. A lower PTV maximum dose (P = 0.039) was significantly associated with the risk of developing distant metastasis. The median change in global eGFR (ml/min) from pre-SBRT levels was -7.0 (interquartile range -14.5 to -1.0) at 1 year and -11.5 (interquartile range -19.5 to -4.0) at 2 years. The proportion of ipsilateral (differential) renal function decreased over time from 47% of overall renal function pre-SBRT to 36% at 2 years, whereas the proportion of contralateral renal function correspondingly improved. On multivariable analysis, a higher volume of uninvolved renal cortex (P < 0.0001) was significantly associated with a smaller decrease in eGFR over time.

CONCLUSION

In this large institutional cohort, oncological outcomes of renal cell carcinoma treated with SBRT were favourable and a longitudinal decline in renal function in the ipsilateral kidney and compensatory increase in the contralateral kidney were observed. Clinical and dosimetric factors were significantly associated with oncological and renal function outcomes.

Safety and Efficacy of Stereotactic Ablative Radiation Therapy for Renal Cell Cancer: 24-Month Results of the RSR1 Phase 1 Dose Escalation Study

PURPOSE

Stereotactic body radiation therapy (SBRT) has become a new therapeutic option for primary renal cell carcinoma. However, treatment doses lack consistency in the literature. The primary objective of this study was to determine the maximum tolerated dose for renal cancer SBRT.

METHODS AND MATERIALS

This phase 1 multicentric dose-escalation study assessed 4 dose levels: 8 Gy × 4, 8 Gy × 5, 10 Gy × 4, and 12 Gy × 4. The primary objective of this study was to determine the maximal tolerated dose, defined by the occurrence of dose-limiting toxicity was defined as any acute side effect of grade ≥4 based on the Common Terminology Criteria for Averse Events, version 4.0.

RESULTS

From October 2010 to September 2017, 13 patients were enrolled. The median follow-up was 23 months. There was no dose-limiting toxicity in our study, and the highest dose was reached successfully. No acute or late toxic effects above grade 2 were seen. There was no significant alteration of renal function after treatment. At 24 months, 2 patients had partial response and the others had stable disease.

CONCLUSIONS

After 24 months of follow-up, no dose-limiting toxicity was seen at any of the prescribed dose levels in our study. The findings suggest that our last dose level of 48 Gy in 4 12-Gy fractions can be considered safe and can be used in further studies.

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.

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.

Stereotactic Body Radiotherapy for Frail Patients with Primary Renal Cell Carcinoma: Preliminary Results after 4 Years of Experience

Simple Summary

Surgical therapy is currently the standard of care for the treatment of primary renal cell carcinoma (RCC). Alternative strategies such as stereotactic body radiotherapy (SBRT) have emerged as potentially curative treatment approaches. In this study, we show a promising short-term local control effect of SBRT in the management of primary RCC. The treatment was well tolerated with no high-grade side effects. The main advantages are the outpatient management without anesthesia and the non-invasive approach. Thus, SBRT appears to be a promising alternative to surgery, or ablative therapy, to treat primary RCC in patients with poor physical health. Future studies are needed to definitively assess the place of SBRT in the RCC treatment portfolio.

Abstract

Introduction: The aim of this study was to report the oncological outcomes and toxicity of stereotactic body radiotherapy (SBRT) to treat primary renal cell carcinoma (RCC) in frail patients unfit for surgery or standard alternative ablative therapies. Methods: We retrospectively enrolled 23 patients who had SBRT for primary, biopsy-proven RCC at our tertiary center between October 2016 and March 2020. Treatment-related toxicities were defined using CTCAE, version 4.0. The primary outcome was local control which was defined using the Response Evaluation Criteria in Solid Tumors. Results: The median age, Charlson score and tumor size were 81 (IQR 79–85) years, 7 (IQR 5–8) and 40 (IQR 28–48) mm, respectively. The most used dose fractionation schedule was 35 Gy (78.3%) in five or seven fractions. The median duration of follow-up for all living patients was 22 (IQR 10–39) months. Local recurrence-free survival, event-free survival, cancer-specific survival and overall survival were 96 (22/23), 74 (18/23), 96 (22/23) and 83% (19/23), respectively. There were no grade 3–4 side effects. No patients required dialysis during the study period. No treatment-related deaths or late complications were reported. Conclusion: SBRT appears to be a promising alternative to surgery or ablative therapy to treat primary RCC in frail patients.

Adaptive Magnetic Resonance-Guided Stereotactic Body Radiotherapy: The Next Step in the Treatment of Renal Cell Carcinoma

Adaptive MR-guided radiotherapy (MRgRT) is a new treatment paradigm and its role as a non-invasive treatment option for renal cell carcinoma is evolving. The early clinical experience to date shows that real-time plan adaptation based on the daily MRI anatomy can lead to improved target coverage and normal tissue sparing. Continued technological innovations will further mitigate the challenges of organ motion and enable more advanced treatment adaptation, and potentially lead to enhanced oncologic outcomes and preservation of renal function. Future applications look promising to make a positive clinical impact and further the personalization of radiotherapy in the management of renal cell carcinoma.

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.

Radiation Therapy for Patients with Advanced Renal Cell Carcinoma

Stereotactic radiosurgery and stereotactic body radiation therapy (SBRT) have led to a resurgence of the use of radiotherapy in the management of advanced renal cell carcinoma (RCC). These techniques provide excellent local control and palliation of metastatic sites of disease with minimal toxicity. Additionally, SBRT to the primary tumor may be efficacious and well tolerated in select patients that are not surgical candidates. Emerging data suggest that SBRT may potentiate the immune response, and current and future study will evaluate if SBRT can improve survival outcomes in patients with metastatic RCC.

Stereotactic Body Radiotherapy for Stage I Renal Cell Carcinoma: National Treatment Trends and Outcomes Compared to Partial Nephrectomy and Thermal Ablation

PURPOSE

To assess use of stereotactic body radiotherapy (SBRT) for stage I renal cell carcinoma (RCC) and compare outcomes with thermal ablation and partial nephrectomy (PN).

MATERIALS AND METHODS

The 2004-2015 National Cancer Database was investigated for histopathologically proven stage I RCC treated with PN, cryoablation, radiofrequency (RF) or microwave (MW) ablation, or SBRT. Patients were propensity score-matched to account for potential confounders, including patient age, sex, race, comorbidities, tumor size, histology, grade, tumor sequence, administration of systemic therapy, treatment in academic vs nonacademic centers, treatment location, and year of diagnosis. Overall survival (OS) was evaluated with Kaplan-Meier plots, log-rank tests, and Cox proportional hazards models.

RESULTS

A total of 91,965 patients were identified (SBRT, n = 174; PN, n = 82,913; cryoablation, n = 5,446; RF/MW ablation, n = 3,432). Stage I patients who received SBRT tended to be older women with few comorbidities treated at nonacademic centers in New England states. After propensity score matching, a cohort of 636 patients was obtained with well-balanced confounders between treatment groups. In the matched cohort, OS after SBRT was inferior to OS after PN and thermal ablation (PN vs SBRT, hazard ratio [HR] = 0.29, 95% confidence interval [CI] 0.19-0.46, P < .001; cryoablation vs SBRT, HR = 0.40, 95% CI 0.26-0.60, P < .001; RF/MW ablation vs SBRT, HR = 0.46, 95% CI 0.31-0.67, P < .001). Compared with PN, neither cryoablation nor RF/MW ablation showed significant difference in OS (cryoablation vs PN, HR = 1.35, 95% CI 0.80-2.28, P = .258; RF/MW ablation vs PN, HR = 0.64, 95% CI 0.95-2.55, P = .079).

CONCLUSIONS

Current SBRT protocols show lower OS compared with thermal ablation and PN, whereas thermal ablation and PN demonstrate comparable outcomes.

Safety of radiotherapy for hemodialysis patients with cancer

BACKGROUND

The number of hemodialysis (HD) patients is increasing worldwide, and they are at a higher risk of cancer than the general population. Because HD patients are more likely to have inflammation, radiotherapy (RT)-induced adverse effects (AEs) are theoretically expected to be worse for HD patients. Since only a few reports have been published on this subject, we aimed to evaluate the tolerability of RT in HD patients.

METHODS

We retrospectively analyzed AEs related to RT for HD patients. Our study included patients from three institutions treated between January 2007 and July 2017. The patient eligibility criteria were (i) receipt of maintenance HD 2-3 times per week for end-stage renal disease prior to the start of RT and (ii) pathologically confirmed malignancies. The endpoints were acute and late non-hematologic AEs.

RESULTS

The study included 56 patients. The most common histology was head and neck cancer (23%), followed by lung cancer (14%) and prostate cancer (11%). The median radiation dose was 60 (range, 12-93.8) Gy at an equivalent dose in 2-Gy fractions (EQD2). The RT completion rate was 96%. Patients had a median follow-up period after RT of 9.1 (range 0.5-98.1) months. Grade 3 or worse acute and late AEs were noted in 6 (11%) and 3 (7%) patients, respectively. In the acute phase, 2 patients had grade 5 AEs, both of which were infections.

CONCLUSION

Our results suggest that RT for HD patients is clinically tolerable. However, some patients can experience severe infections related to treatment.

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.

Treating the Chameleon: Radiotherapy in the management of Renal Cell Cancer

PURPOSE

To review the role of radiotherapy (RT) in the treatment of renal cell cancer (RCC) in the curative and palliative setting.

CONTENT

Details related to the clinical outcomes of primary, preoperative, postoperative and palliative RT are discussed, along with a presentation of the established role of surgery and systemic therapy. An overview of data derived from mono- and multi-institutional trials is provided.

CONCLUSION

Radiotherapy has been shown to provide good symptom palliation and local control in RCC depending on the dose that can be delivered. There is emerging data suggesting that with the use of high-precision RT methods the indication spectrum of RT can be exploited covering different clinical situations particularly for unresectable local recurrences and oligometastatic disease.

Stereotactic body radiation therapy (SBRT) on renal cell carcinoma, an overview of technical aspects, biological rationale and current literature

BACKGROUND

Stereotactic body radiotherapy (SBRT) is characterized by the delivery of high doses of ionizing radiation in few fractions. It is highly effective in achieving local control, and, due to the high biological effective dose administered, it seems to overcome the radioresistance of renal cell carcinoma (RCC). Thus, SBRT could constitute a treatment option for the management of localized RCC in patients who are not surgical candidates. In this paper, we report an overview about data from the current evidence about SBRT in patients affected by localized RCC.

MATERIALS AND METHODS

A non-systematic review was performed, including data from both retrospective and prospective studies focusing on the use of SBRT for localized RCC and its biological rationale. Furthermore, ongoing trials on this issue are reported.

CONCLUSION

Currently, SBRT might be considered a treatment alternative in inoperable patients affected by primary RCC. Currently, dose-escalation to 48 Gy in 3-4 fractions are effective and well tolerated. Emerging role of immune therapies in RCC patients warrant further studies to explore interactions between SBRT and immune response.

TROG 15.03 phase II clinical trial of Focal Ablative STereotactic Radiosurgery for Cancers of the Kidney - FASTRACK II

Background

Stereotactic ablative body radiotherapy (SABR) is a non-invasive alternative to surgery to control primary renal cell cancer (RCC) in patients that are medically inoperable or at high-risk of post-surgical dialysis. The objective of the FASTRACK II clinical trial is to investigate the efficacy of SABR for primary RCC.

Methods

FASTRACK II is a single arm, multi-institutional phase II study. Seventy patients will be recruited over 3 years and followed for a total of 5 years. Eligible patients must have a biopsy confirmed diagnosis of primary RCC with a single lesion within a kidney, have ECOG performance ≤2 and be medically inoperable, high risk or decline surgery. Radiotherapy treatment planning is undertaken using four dimensional CT scanning to incorporate the impact of respiratory motion. Treatment must be delivered using a conformal or intensity modulated technique including IMRT, VMAT, Cyberknife or Tomotherapy. The trial includes two alternate fractionation schedules based on tumour size: for tumours ≤4 cm in maximum diameter a single fraction of 26Gy is delivered; and for tumours > 4 cm in maximum diameter 42Gy in three fractions is delivered. The primary outcome of the study is to estimate the efficacy of SABR for primary RCC. Secondary objectives include estimating tolerability, characterising overall survival and cancer specific survival, estimating the distant failure rate, describing toxicity and renal function changes after SABR, and assessment of cost-effectiveness of SABR compared with current therapies.

Discussion

The present study design allows for multicentre prospective validation of the efficacy of SABR for primary RCC that has been observed from prior single institutional and retrospective series. The study also allows assessment of treatment related toxicity, overall survival, cancer specific survival, freedom from distant failure and renal function post therapy.

Trial registration

Clinicaltrials.govNCT02613819, registered Nov 25th 2015.

Utilization of radiotherapy and stereotactic body radiation therapy for renal cell cancer in the USA

AIM

This study evaluated national practice patterns of cT1N0M0 renal cell cancer, with a focus on stereotactic body radiation therapy (SBRT) utilization.

METHODS

The National Cancer Database was queried (2004-2013) for patients with newly-diagnosed cT1a/bN0M0 renal cell cancer that received definitive treatment. Temporal trends in utilization were tabulated.

RESULTS

Altogether, 138,495 patients met inclusion criteria; 13,725 (9.9%) patients received ablative therapy, 57,924 (41.8%) partial nephrectomy, 67,168 (48.5%) radical nephrectomy and 308 (0.2%) external beam radiation therapy (EBRT). The proportion of EBRT that was SBRT increased substantially from 25% in 2004 to 95.4% in 2013, with a sharp inflection point from 2005 to 2006.

CONCLUSION

SBRT utilization has sharply risen over time; in most recent years, the vast majority of EBRT is delivered in the form of SBRT.

Evaluation of kidney motion with and without a pneumatic abdominal compression belt: Considerations for stereotactic radiotherapy

INTRODUCTION

The optimal delivery of stereotactic radiotherapy for kidney tumours requires an effective motion management strategy. This study assessed the effectiveness of a pneumatic abdominal compression belt in reducing kidney motion during free breathing.

METHODS

Thirteen patients, with four-dimensional computed tomography (4DCT) of the abdomen in free breathing with and without a pneumatic abdominal compression belt, were retrospectively reviewed. Points of Interest (POI) were placed on each kidney to determine the greatest magnitude of displacement in all directions.

RESULTS

Without compression, all patients had >5.0 mm motion in the craniocaudal (CC) direction in at least one kidney. Median CC excursion of the left superior pole was reduced with compression from 8.0 mm (range 2.0 mm-18.0 mm) to 4.0 mm (range 2.0 mm-10.0 mm, P = 0.047) and right superior pole from 10.0 mm (range 4.0 mm-16.0 mm) to 6.0 mm (range 2.0 mm-10.0 mm, P=value 0.051). A benefit was less evident for the left and right inferior poles with median CC excursion of 6.0 mm versus 4.0 mm and 5.0 mm versus 4.0 mm without and with compression, respectively. Median displacement in the anteroposterior direction (≤3.2 mm) and lateral directions (≤1.3 mm) was similar for left and right kidneys and not significantly altered by compression. Overall, seven patients had kidney motion reduced by >5.0 mm with two reduced by 10.0 mm.

CONCLUSION

A pneumatic abdominal compression belt reduced kidney motion by >5.0 mm in seven of thirteen patients. The relative benefit is patient and location specific and should be assessed on an individual basis.

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.

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.

Role of Radiotherapy in the Treatment of Renal Cell Cancer: Updated and Critical Review

Purpose

The growing incidence of renal cell carcinoma (RCC) raises many questions about the management of these patients. The late clinical presentation, the presence of locally advanced or metastatic disease at diagnosis, the difficulty of radical surgical excision, and radioresistance make it one of the more challenging tumors to treat. The primary objective of this article is to propose an updated and critical review of the role of radiotherapy (RT) in the treatment of RCC.

Methods

This literature review is based on data from meta-analyses and randomized, prospective, and retrospective studies. We collected reports from 1970 to the present about preoperative RT, postoperative RT, stereotactic body RT, radiosurgery, and intraoperative RT in locally advanced renal cancer and in metastatic diseases.

Results

We emphasize the progress made in RT technology that allowed the creation of a more personalized and focused treatment with a minimum rate of complications.

Conclusions

In the coming years, new studies will be published to confirm and increase the indications for use of RT.