Evaluation of Volumetric Response Assessment From SABR for Renal Cell Carcinoma

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.

Delayed Abscopal Response 3 Years After Robotic Stereotactic Body Radiation Therapy for Renal Cell Carcinoma: A Case Report

BACKGROUND

Renal cell carcinoma (RCC) is the most common malignant tumor of the kidney in adults, with poor prognosis in advanced or metastatic stages. Although traditionally considered radioresistant, RCC has shown a promising response to stereotactic body radiation therapy (SBRT), which not only offers local tumor control but may also induce an abscopal effect, resulting in regression of distant metastases.

CASE

A 54-year-old male with a history of right RCC underwent radical nephrectomy in 2000, followed by partial nephrectomy for a left kidney recurrence in 2005. In 2011, imaging revealed a second recurrence in the left kidney. In 2013, after declining further surgery, he was treated with SBRT for the recurrent left renal lesion. Follow-up imaging revealed a stable renal mass and a solid right lung nodule. Retrospective analysis of prior imaging suggested the presence of pulmonary metastases concurrent with the renal recurrence. The pulmonary nodule progressively enlarged until November 2016 but then spontaneously regressed by November 2017 without any additional systemic or local interventions, and remained stably reduced in size thereafter. Serial imaging from 2018 showed no evidence of new metastatic disease, and the left renal lesion exhibited partial regression. The pulmonary metastasis remained stable, consistent with the occurrence of an abscopal effect that persisted for 3 years. The patient ultimately passed away in 2024 from unrelated causes.

CONCLUSION

This case demonstrates the potential of SBRT to induce a systemic abscopal response in metastatic RCC, with sustained control of pulmonary metastasis over 3 years. The findings suggest that SBRT may play a critical role in managing metastatic RCC, warranting further research into its synergy with immunotherapy for long-term therapeutic benefit.

Metastasis-directed therapy in oligometastatic and oligoprogressive renal cell carcinoma

PURPOSE OF REVIEW

This review addresses the evolving role of metastasis-directed therapy (MDT) in the management of oligometastatic and oligoprogressive renal cell carcinoma (RCC). With advances in both surgical techniques and stereotactic ablative radiotherapy (SABR), it is timely to explore how MDT can improve patient outcomes in these distinct disease states. The review highlights the potential of MDT to delay systemic therapy and improve quality of life while noting the lack of randomized clinical trial data guiding its use.

RECENT FINDINGS

Recent literature emphasizes the outcomes of MDT, including metastasectomy and SABR, in managing oligometastatic and oligoprogressive RCC. Key studies suggest that MDT may prolong progression-free survival and delay systemic therapy. SABR has demonstrated high local control rates and manageable toxicity, offering a less invasive alternative to surgery. Despite these findings, there remains uncertainty about MDT's long-term impact on overall survival due to the absence of prospective randomized trials.

SUMMARY

MDT holds promise in treating RCC by offering symptom relief, improving quality of life, and potentially delaying systemic therapy. However, the long-term benefits, particularly regarding survival outcomes, remain unclear. Further research, including prospective trials, is needed to better define the role of MDT in clinical practice, particularly in the absence of clear guidelines for patient selection.

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.