Abstract
Objectives:
The best fractionation for stereotactic body radiotherapy (SBRT) in renal cell carcinoma (RCC) metastases has not been well defined. Additionally, the literature on outcomes using five fraction SBRT in the setting of osseous metastases have not been well reported.
Methods:
39 patients with 69 RCC osseous metastases were treated using five fraction SBRT at single institution using two dose fractionation schemes. Overall survival and local control outcomes of the two fractionation schemes were studied using Kaplan-Meier curves.
Results:
Of the 69 lesions included in the study, 20 were treated with 30 Gy in 5 fractions and 49 were treated with 40 Gy in 5 fractions. The median age of patients at diagnosis was 58.4 years. The one-year local control (LC) rate for all treated lesions was 85.5% (59/69) with a LC of 90% (18/20) for lesions receiving 30 Gy and 83.7% (41/49) in lesions receiving 40 Gy. There was no statistically significant difference in one-year local control rate between the two fractionation schemes (p-value 0.553).
Conclusions:
Patients with osseous RCC metastases undergoing five fraction SBRT had favorable local control outcomes. There was no difference in survival or local control between 40Gy and 30Gy treatment arms.
Keywords: Renal Cell carcinoma, SBRT, radiotherapy, Oligometastatic, Osseous Metastases
INTRODUCTION
Renal Cell Carcinoma (RCC) originates from the renal epithelium and accounts for about 80% of primary renal malignancies.1 According to Surveillance, Epidemiology, and End Results (SEER) database, over 74,000 new cases of RCC were diagnosed in 2019 which accounted for almost 5% of all cancer diagnoses in the United States.2 At diagnosis, about 30% of patients present with metastatic disease while about 30% of patients initially diagnosed with localized disease have a recurrence.3 Metastatic RCC is primarily treated with systemic drug therapy, such as targeted agents and immunotherapy. However, in patients with oligometastatic, oligoprogressive, or disease requiring palliative treatments, ablative-intent radiotherapy has been shown to be successful. Previously, RCC was believed to be a radio-resistant histology with conventional radiotherapy dosing demonstrating little success in the treatment of primary and metastatic disease.4 However, advances in radiation therapy, namely the use of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT), overcomes the conventional dose limitation and have emerged as highly effective localized treatment options for patients with metastatic RCC. Recent studies have demonstrated that SRS and SBRT provide effective pain palliation and local control rates of approximately 90% in the treatment of metastatic RCC.5 For non-intracranial RCC metastases, outcomes of several dose-fractionation strategies have been published, with the most effective regimen remaining unclear. Using fractionated SBRT could potentially increase the therapeutic window to minimize toxicity compared to single fractionated treatments. Two common SBRT treatment schemes for metastatic renal cell carcinoma are 30 Gy in 5 fractions and 40 Gy in 5 fractions. However, little is known about the comparative success of these treatment strategies in terms of local control rates, disease progression (time to next systemic therapy), overall survival, and side-effect profile, all of which are analyzed in this retrospective study. Furthermore, we evaluated if specific treatment dosimetric parameters were associated with improved local control rates, disease progression, and overall survival.
Materials and Methods
A retrospective cohort study was conducted on patients who were treated with 5-fraction SBRT for osseous metastatic RCC between January 2015 and February 2021 at Vanderbilt University Medical Center (VUMC). The study was reviewed and approved by the VUMC Institutional Review Board. We identified eligible consecutive patients from a single radiation oncologist’s patient population using institutional electronic medical record with inclusion criteria consisting of osseous metastatic RCC treated with 5 fraction SBRT with the availability of data to determine radiographic response after treatment. Exclusion criteria included insufficient data in the medical record such as inadequate follow up appointments or imaging.
All patients were treated with SBRT using a Truebeam (Varian (Palo Alto, California)) linear accelerator intensity modulated radiotherapy treatment (IMRT) technique by volumetric modulated arc therapy (VMAT). CT simulation scans were performed with appropriate immobilization and motion management techniques per the discretion of the treating physician, typically Vac-Lok (Civco) or VacQfix Vacuum Cushions (QFix) body mold for thoracic, pelvic, or extremity sites, or thermoplastic mask (Civco) for head/neck location and extremity sites. Target delineation of gross tumor volume (GTV), clinical tumor volume (CTV), planning tumor volume (PTV) were determined by a single managing physician with utilization of image registrations from diagnostic imaging including PET/CT, MRI, or CT, as indicated per patient. Treatment with SBRT was performed with daily image guidance by cone-beam CT (CBCT) and 6 degrees-of-freedom table motion. The decision to treat metastases with either 40 Gy in 5 fractions versus 30 Gy in 5 fractions was made by the treating physician without strict criteria dictating which dose fractionation scheme should be used.
Following completion of radiotherapy, patients underwent surveillance diagnostic imaging. Radiographic response was assessed every three months with radiographic disease progression determined by the interpretation of the certified radiologist.
Regarding statistical methods, descriptive statistics were presented as mean (IQR) for continuous variables and count (percentage) for categorical variables. Since one patient could have multiple radiation treatments at different times or sites, a multivariable mixed-effects proportional hazard model was applied on the outcomes of time to recurrence, time to systemic therapy, and time to death outcomes. The main interest of the study, the dose (30 Gy vs 40 Gy), was the main fixed effect in the model, and the patient study identification was the random effect. Given the limited number of observations, two covariates, age at diagnosis and Charlson comorbidity index, were selected as additional fixed effects. R (Version 4.1.3) was used to conduct all analyses and used the mgcv package to conduct the mixed-effects proportional hazard model.6,7
Results
In this study, 39 patients with a total of 69 osseous metastases from RCC were treated with SBRT between January 2015 and February 2021. The study population was predominantly male (n=31). The median age at diagnosis was 58.4 years ranging from age 26.3 to 78.5 years. Thirty-three of the patients had tumor histology clear cell RCC, while the remainder of the patients had non-clear cell RCC (e.g. papillary). The clinical characteristics of the patients in the study are summarized in Table 1. Of the 69 lesions included in the study, 20 were treated with 30 Gy in 5 fractions and 49 were treated with 40 Gy in 5 fractions. Characteristics of the 69 lesions treated in the study are shown in Table 2. The mean size of the PTV for 30Gy and 40Gy cohorts were 170.08 ccs and 149.34ccs respectively.
Table 1:
Clinical characteristics of patient population
| Overall | Missing | |
|---|---|---|
| 39 | ||
| Gender (%) | ||
| Female | 8 (20.5) | 0.0 |
| Male | 31 (79.5) | |
| Age at Initial Diagnosis | ||
| mean (SD) | 57.0 (10.4) | 0.0 |
| median [IQR] | 58.4 [51.7, 63.9] | 0.0 |
| median [range] | 58.4 [26.3, 78.5] | 0.0 |
| Race (%) | ||
| Asian | 1 (2.6) | 0.0 |
| Black or African American | 4 (10.3) | |
| White | 32 (82.1) | |
| Unknown / Not Reported | 2 (5.1) | |
| Ethnicity (%) | ||
| NOT Hispanic or Latino | 37 (94.9) | 2.6 |
| Unknown / Not Reported | 1 (2.6) | |
| NA | 1 (2.6) | |
| Days from Initial to Meta | ||
| mean (SD) | 942.2 (1449.7) | 7.7 |
| median [IQR] | 342.0 [0.0, 973.8] | 7.7 |
| median [range] | 342.0 [0.0, 6169.0] | 7.7 |
| Charlson Comorbidity Index Points | ||
| 6 | 1 (2.6) | 0.0 |
| 7 | 7 (17.9) | |
| 8 | 9 (23.1) | |
| 9 | 12 (30.8) | |
| 10 | 7 (17.9) | |
| 11 | 2 (5.1) | |
| 12 | 1 (2.6) | |
| Histology Type (%) | ||
| Clear Cell | 33 (84.6) | 0.0 |
| Papillary Type 1 | 1 (2.6) | |
| Papillary Type 2 | 1 (2.6) | |
| Chromophobe | 2 (5.1) | |
| Other (cystic-solid, collecting duct, medullary, mucinous tubular, spindle cell, etc) | 2 (5.1) | |
Table 2:
Characteristics of lesions included in study, including location, bony vs. non-bony metastasis, indication for radiotherapy, and previous irradiation.
| Overall | 30 Gy in 5 fx | 40 Gy in 5 fx | Missing | |
|---|---|---|---|---|
| 69 | 20 | 49 | ||
| One Year Local Control (%) | ||||
| No | 10 (14.5) | 2 (10.0) | 8 (16.3) | 0.0 |
| Yes | 59 (85.5) | 18 (90.0) | 41 (83.7) | |
| Previously Irradiated (%) | ||||
| No | 66 (95.7) | 19 (95.0) | 47 (95.9) | 0.0 |
| Yes | 3 (4.3) | 1 (5.0) | 2 (4.1) | |
| Disease Status at Radiation (%) | ||||
| Oligo-metastasis without new drug therapy planned | 16 (23.2) | 3 (15.0) | 13 (26.5) | 0.0 |
| Oligo-progressive site on drug therapy | 21 (30.4) | 5 (25.0) | 16 (32.7) | |
| Widespread metastatic disease (>5 disease sites) | 32 (46.4) | 12 (60.0) | 20 (40.8) | |
| Indication for Radiotherapy – Disease Progression (%) | ||||
| No | 10 (14.5) | 6 (30.0) | 4 (8.2) | 0.0 |
| Yes | 59 (85.5) | 14 (70.0) | 45 (91.8) | |
| Radiotherapy Site (%) | ||||
| Bone | 64 (92.8) | 20 (100.0) | 44 (89.8) | 0.0 |
| Other | 5 (7.2) | 0 (0.0) | 5 (10.2) | |
| Number of Fractions (%) | ||||
| 5 | 69 (100.0) | 20 (100.0) | 49 (100.0) | 0.0 |
| Radiation Dose per Fraction (%) | ||||
| 6 | 20 (29.0) | 20 (100.0) | 0 (0.0) | 0.0 |
| 8 | 49 (71) | 0 (0.0) | 49 (100) | |
| Tumor GTV Size (cc) | ||||
| Mean | 51.08 | 48.96 | 53.19 | |
| Median | 25.31 | 27.72 | 24.09 | |
| Standard-error | 9.65 | 11.96 | 12.70 | |
| Tumor PTV Size (cc) | ||||
| Mean | 159.71 | 170.08 | 149.34 | |
| Median | 98.68 | 129.17 | 85.08 | |
| Standard-error | 23.04 | 31.76 | 30.35 | |
| PTV(%vol) receiving 100% Prescription Dose | ||||
| mean (SD) | 85.6 (13.3) | 89.6 (13.0) | 84.1 (13.3) | 1.4 |
| median [IQR] | 89.8 [79.6, 95.7] | 93.5 [87.7, 97.5] | 86.3 [79.2, 95.0] | 1.4 |
| median [range] | 89.8 [32.2, 99.8] | 93.5 [45.8, 99.8] | 86.3 [32.2, 99.7] | 1.4 |
| Age (years) at Radiotherapy | ||||
| mean (SD) | 60.6 (10.0) | 58.3 (9.7) | 61.6 (10.0) | 0.0 |
| median [IQR] | 61.8 [53.4, 68.2] | 61.6 [48.4, 62.3] | 63.6 [54.1, 69.1] | 0.0 |
| median [range] | 61.8 [37.6, 81.8] | 61.6 [41.6, 81.8] | 63.6 [37.6, 77.9] | 0.0 |
| RTOG Toxicity Score | ||||
| mean (SD) | 0.7 (1.1) | 0.5 (1.0) | 0.8 (1.1) | 1.4 |
| median [IQR] | 0.0 [0.0, 1.0] | 0.0 [0.0, 1.0] | 0.0 [0.0, 1.0] | 1.4 |
| median [range] | 0.0 [0.0, 4.0] | 0.0 [0.0, 4.0] | 0.0 [0.0, 4.0] | 1.4 |
| RTOG Toxicity Score (%) | ||||
| 0 | 41 (59.4) | 13 (65.0) | 28 (57.1) | 1.4 |
| 1 | 13 (18.8) | 4 (20.0) | 9 (18.4) | |
| 2 | 8 (11.6) | 1 (5.0) | 7 (14.3) | |
| 3 | 4 (5.8) | 0 (0.0) | 4 (8.2) | |
| 4 | 2 (2.9) | 1 (5.0) | 1 (2.0) | |
| NA | 1 (1.4) | 1 (5.0) | 0 (0.0) | |
| CTCAE Toxicity Score | ||||
| mean (SD) | 0.6 (1.0) | 0.4 (0.6) | 0.8 (1.1) | 1.4 |
| median [IQR] | 0.0 [0.0, 1.0] | 0.0 [0.0, 1.0] | 0.0 [0.0, 2.0] | 1.4 |
| median [range] | 0.0 [0.0, 4.0] | 0.0 [0.0, 2.0] | 0.0 [0.0, 4.0] | 1.4 |
| CTCAE Toxicity Score (%) | ||||
| 0 | 43 (62.3) | 13 (65.0) | 30 (61.2) | 1.4 |
| 1 | 11 (15.9) | 5 (25.0) | 6 (12.2) | |
| 2 | 10 (14.5) | 1 (5.0) | 9 (18.4) | |
| 3 | 3 (4.3) | 0 (0.0) | 3 (6.1) | |
| 4 | 1 (1.4) | 0 (0.0) | 1 (2.0) | |
| NA | 1 (1.4) | 1 (5.0) | 0 (0.0) | |
The one-year local control (LC) rate for all treated lesions was 85.5% (59/69) with a LC of 90% (18/20) for lesions receiving 30 Gy and 83.7% (41/49) in lesions receiving 40 Gy. There was no statistically significant difference in one-year local control rate between the two fractionation schemes (p-value 0.553). A Kaplan-Meier curve comparing the time to local recurrence for each of the treatment plans is shown in Figure 1. Furthermore, no correlation between one-year local control rate and patient gender (p-value 0.293), age at time of treatment (p-value 0.724), indication for radiotherapy (p-value 0.676), or year of treatment (p-value 0.627) were noted. The mean RTOG toxicity score for lesions receiving 30Gy versus 40Gy were not statistically different with mean toxicity score of 0.5 and 0.7 respectively (p= 0.534). No significant correlation between local-control rate and individual characteristics of the SBRT plan were identified. For example, there was no statistically significant correlation between percent of GTV or PTV receiving 100% of the prescribed dose and one-year local control rate (p-value 0.769 and p-value 0.687 respectively). Additionally, there was no statistical difference in time to next systemic therapy or time to death.
Figure 1:
Kaplan-Meier analysis. Time from initial radiotherapy to local recurrence. No significant difference found between lesions treated with 30Gy/5 fractions vs. 40Gy/5 fractions (p-value 0.553).
DISCUSSION
Multiple recently published studies have demonstrated the significant benefit to localized therapy for oligometastatic RCC using ablative-intent SBRT in the treatment of metastases with improvements in overall survival, progression free survival, and local control in the setting of acceptable treatment toxicity.8–11 Furthermore, when specifically discussing treatment for oligometastatic RCC, studies suggest benefit of ablative SBRT with improved outcomes.12,13 In oligometastatic RCC patients who have prolonged survival, the importance of local control and decreasing morbidity of disease progression is even more pronounced. Recent data has shown that ablative radiotherapy can delay the need to initiate or switch systemic therapies for oligometastatic RCC patients. In a phase II study evaluating 30 patients with oligometastatic RCC who underwent SBRT to all sites of metastatic disease, patients were maintained off systemic drug therapy with 1 year PFS of 64% and median PFS of 22.7 months.14 In a phase II study evaluating patients with oligoprogressive RCC, the treatment of oligoprogressive RCC with SBRT in 37 patients who were previously on a tyrosine kinase inhibitor (TKI) and subsequently continued on same systemic therapy following radiotherapy had a median time to change in systemic therapy of 12.6 months, 1 year OS of 92%, and no grade 3 or higher SBRT related toxicity.15 Given the suggested benefits for OS, PFS, LC, and delayed time for use of next-line systemic drug therapy, SBRT has shown to be a treatment modality that warrants further investigation to potentially be used in first-line therapy as an alternative or in combination with systemic therapy for patients with oligometastatic or oligoprogressive RCC.
While the benefits of SBRT for metastatic RCC are evident, the exact dose and fractionation of radiotherapy for osseous RCC metastases that provides highest local control with acceptable toxicity remains unclear. Recently, there has been data published that suggests superiority in regard to local control using single fraction versus multifraction SBRT.16 In a secondary analysis of a prospective study of 47 spinal metastases treated with SBRT, 1-year and 2-year local control rates for single fraction versus multifraction SBRT were 95% vs 71% and 86% versus 55%, respectively.16 Other studies have investigated if a threshold biological effective dose (BED) can have effects on clinical outcomes. In one study, a BED of >80 Gy using a linear-quadratic model alpha/beta ratio of 7 for RCC showed improved local control for bony RCC metastases.17 A retrospective review of 175 metastatic RCC lesions treated with SBRT found that LC was improved when 99% of the target volume received a dose greater than BED of 98.7, which is equivalent to 30 Gy in 5 fractions (alpha/beta ratio of 2.63).18 It remains unclear if different sites of metastases, for example pulmonary versus osseous metastases, require increased BED to maintain high local control. In a retrospective analysis of 181 metastatic RCC lesions, no significant benefit in LC was identified with dose escalation or difference in LC based on different sites of metastases.19
We observed high rates of one-year local control of 85.5% for patients undergoing 5-fraction SBRT for osseous metastases from RCC. When compared to previously published literature for local control of SBRT for RCC, our study compares favorably to single fraction SBRT, which questions the superiority in regard to local control using single fraction versus multifraction SBRT. Although treatment protocols favoring higher total radiation doses (e.g., 40 Gy) for the treatment of these metastases have been more commonly used in recent years at our institution, we found no statistically significant difference between low dose (30 Gy) and high dose (40 Gy) treatment plans in one-year local control rate. These treatment plans did not differ significantly in side-effect profile. Most patients in each group experienced either zero side-effects or RTOG grade 1 toxicities such as mild skin erythema.
Potential limitations of the study include study size and diversity of the patient population. Thirty-nine patients with a total of 69 lesions were included in the study. More lesions in the study received radiation doses of 40 Gy (n=49) compared to 30 Gy (n=20), which may have resulted in difficulty in identifying statistically significant differences between the two treatment protocols. The study population was predominantly male (n=33) and white (n=31), which raises concerns as to the generalizability of the study to a more diverse patient group.
CONCLUSION
In a single institution retrospective cohort study, our study demonstrates the efficacy of five fraction SBRT in the treatment of osseous metastatic RCC with favorably local control rates and low toxicity. No statistical benefit in local control was found with dose escalation. Further prospective randomized data is needed to further evaluate fractionation schemes.
Acknowledgements:
The authors thank Guozhen Luo MS for technical assistance in radiation physics and dosimetry. The project described was supported by CTSA award No. UL1 TR002243 from the National Center for Advancing Translational Sciences. Its contents are solely the responsibility of the authors and do not necessarily represent official views of the National Center for Advancing Translational Sciences or the National Institutes of Heal
Footnotes
Declarations:
Ethics approval and consent to participate/publish:
Competing interests: The authors declare they have no financial or non-financial interests to disclose.
Availability of data and materials:
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
REFERENCES:
- 1.Escudier B, Porta C, Schmidinger M, Rioux-Leclercq N, Bex A, Khoo V, Grünwald V, Gillessen S, Horwich A, ESMO Guidelines Committee. Electronic address: clinicalguidelines@esmo.org. Renal cell carcinoma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up†. Ann Oncol. 2019. May 1;30(5):706–720. [DOI] [PubMed] [Google Scholar]
- 2.Padala SA, Barsouk A, Thandra KC, Saginala K, Mohammed A, Vakiti A, Rawla P, Barsouk A. Epidemiology of Renal Cell Carcinoma. World J Oncol. 2020. Jun;11(3):79–87. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Altoos B, Amini A, Yacoub M, Bourlon MT, Kessler EE, Flaig TW, Fisher CM, Kavanagh BD, Lam ET, Karam SD. Local Control Rates of Metastatic Renal Cell Carcinoma (RCC) to Thoracic, Abdominal, and Soft Tissue Lesions Using Stereotactic Body Radiotherapy (SBRT). Radiat Oncol. 2015. Oct 28;10:218. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Spyropoulou D, Tsiganos P, Dimitrakopoulos FI, Tolia M, Koutras A, Velissaris D, Lagadinou M, Papathanasiou N, Gkantaifi A, Kalofonos H, Kardamakis D. Radiotherapy and Renal Cell Carcinoma: A Continuing Saga. In Vivo. 2021. Jun;35(3):1365–1377. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Rühle A, Andratschke N, Siva S, Guckenberger M. Is there a role for stereotactic radiotherapy in the treatment of renal cell carcinoma? Clin Transl Radiat Oncol. 2019. Sep;18:104–112. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.R Core Team. R: A Language and Environment for Statistical Computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2022. Available from: https://www.R-project.org/ [Google Scholar]
- 7.Wood SN. Generalized Additive Models: An Introduction with R, Second Edition [Internet]. Chapman and Hall/CRC; 2017. [cited 2022 Jun 26]. Available from: https://www.routledge.com/Generalized-Additive-Models-An-Introduction-with-R-Second-Edition/Wood/p/book/9781498728331 [Google Scholar]
- 8.Palma DA, Olson R, Harrow S, Gaede S, Louie AV, Haasbeek C, Mulroy L, Lock M, Rodrigues GB, Yaremko BP, Schellenberg D, Ahmad B, Griffioen G, Senthi S, Swaminath A, Kopek N, Liu M, Moore K, Currie S, Bauman GS, Warner A, Senan S. Stereotactic ablative radiotherapy versus standard of care palliative treatment in patients with oligometastatic cancers (SABR-COMET): a randomised, phase 2, open-label trial. Lancet. 2019. 18;393(10185):2051–2058. [DOI] [PubMed] [Google Scholar]
- 9.Palma DA, Olson R, Harrow S, Gaede S, Louie AV, Haasbeek C, Mulroy L, Lock M, Rodrigues GB, Yaremko BP, Schellenberg D, Ahmad B, Senthi S, Swaminath A, Kopek N, Liu M, Moore K, Currie S, Schlijper R, Bauman GS, Laba J, Qu XM, Warner A, Senan S. Stereotactic Ablative Radiotherapy for the Comprehensive Treatment of Oligometastatic Cancers: Long-Term Results of the SABR-COMET Phase II Randomized Trial. J Clin Oncol. 2020. Sep 1;38(25):2830–2838. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Mercier C, Claessens M, Buys MSc A, Gryshkevych S, Billiet C, Joye I, Van Laere S, Vermeulen P, Meijnders P, Löfman F, Poortmans P, Dirix L, Verellen D, Dirix P. Stereotactic Ablative Radiation Therapy to All Lesions in Patients With Oligometastatic Cancers: A Phase 1 Dose-Escalation Trial. Int J Radiat Oncol Biol Phys. 2021. Apr 1;109(5):1195–1205. [DOI] [PubMed] [Google Scholar]
- 11.Chalkidou A, Macmillan T, Grzeda MT, Peacock J, Summers J, Eddy S, Coker B, Patrick H, Powell H, Berry L, Webster G, Ostler P, Dickinson PD, Hatton MQ, Henry A, Keevil S, Hawkins MA, Slevin N, van As N. Stereotactic ablative body radiotherapy in patients with oligometastatic cancers: a prospective, registry-based, single-arm, observational, evaluation study. Lancet Oncol. 2021. Jan;22(1):98–106. [DOI] [PubMed] [Google Scholar]
- 12.Magné N, Latorzeff I. Oligometastatic renal cell carcinoma: radiotherapy as a new standard of care? Lancet Oncol. 2021. Dec;22(12):1644–1645. [DOI] [PubMed] [Google Scholar]
- 13.Kothari G, Foroudi F, Gill S, Corcoran NM, Siva S. Outcomes of stereotactic radiotherapy for cranial and extracranial metastatic renal cell carcinoma: a systematic review. Acta Oncol. 2015. Feb;54(2):148–157. [DOI] [PubMed] [Google Scholar]
- 14.Tang C, Msaouel P, Hara K, Choi H, Le V, Shah AY, Wang J, Jonasch E, Choi S, Nguyen QN, Das P, Prajapati S, Yu Z, Khan K, Powell S, Murthy R, Sircar K, Tannir NM. Definitive radiotherapy in lieu of systemic therapy for oligometastatic renal cell carcinoma: a single-arm, single-centre, feasibility, phase 2 trial. Lancet Oncol. 2021. Dec;22(12):1732–1739. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Cheung P, Patel S, North SA, Sahgal A, Chu W, Soliman H, Ahmad B, Winquist E, Niazi T, Patenaude F, Lim G, Heng DYC, Dubey A, Czaykowski P, Wong RKS, Swaminath A, Morgan SC, Mangat R, Keshavarzi S, Bjarnason GA. Stereotactic Radiotherapy for Oligoprogression in Metastatic Renal Cell Cancer Patients Receiving Tyrosine Kinase Inhibitor Therapy: A Phase 2 Prospective Multicenter Study. Eur Urol. 2021. Dec;80(6):693–700. [DOI] [PubMed] [Google Scholar]
- 16.Ghia AJ, Chang EL, Bishop AJ, Pan HY, Boehling NS, Amini B, Allen PK, Li J, Rhines LD, Tannir NM, Tatsui CE, Brown PD, Yang JN. Single-fraction versus multifraction spinal stereotactic radiosurgery for spinal metastases from renal cell carcinoma: secondary analysis of Phase I/II trials. J Neurosurg Spine. 2016. May;24(5):829–836. [DOI] [PubMed] [Google Scholar]
- 17.Amini A, Altoos B, Bourlon MT, Bedrick E, Bhatia S, Kessler ER, Flaig TW, Fisher CM, Kavanagh BD, Lam ET, Karam SD. Local control rates of metastatic renal cell carcinoma (RCC) to the bone using stereotactic body radiation therapy: Is RCC truly radioresistant? Pract Radiat Oncol. 2015. Dec;5(6):e589–e596. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Wang CJ, Christie A, Lin MH, Jung M, Weix D, Huelsmann L, Kuhn K, Meyer J, Desai N, Kim DWN, Pedrosa I, Margulis V, Cadeddu J, Sagalowsky A, Gahan J, Laine A, Xie XJ, Choy H, Brugarolas J, Timmerman R, Hannan R. Safety and Efficacy of Stereotactic Ablative Radiation Therapy for Renal Cell Carcinoma Extracranial Metastases. Int J Radiat Oncol Biol Phys. 2017. May 1;98(1):91–100. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Singh R, Ansinelli H, Sharma D, Jenkins J, Davis J, Sharma S, Vargo JA. Stereotactic body radiation therapy (SBRT) for metastatic renal cell carcinoma: A multi-institutional experience. J Radiosurg SBRT. 2020;7(1):29–37. [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.