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

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.

Breaking barriers: Stereotactic ablative proton and photon radiation therapy for renal cell carcinoma with extensive metastases: A case report

Patients with advanced renal cancer (RCC) often have limited success with systemic therapy due to tumor heterogeneity. However, stereotactic ablative radiotherapy (SABR) has been shown to have a beneficial therapeutic effect for oligometastatic disease when used early. Despite this, current guidelines recommend the use of tyrosine kinase inhibitors (TKIs) as the first-line therapeutic agent for patients with recurrent or metastatic kidney cancer. Additionally, there is limited data on the combination of systemic treatment and SABR for extensive metastatic RCC due to concerns about high toxicity. Proton therapy offers a promising treatment option as it emits energy at a specific depth, generating high target doses while minimizing damage to normal tissue. This allows for precise treatment of various tumor lesions. In this case report, we describe a high-risk 65-year-old male with extensive pleural and thoracic lymph node metastases and 2 bone metastases of clear cell renal cancer. While the targeted therapy and immunotherapy effectively treated the bone metastases, it was not effective in treating the chest metastases, including the pleural and lymph node metastases. Thus, the patient received full-coverage radiotherapy with photon for primary renal tumor and intensity-modulated proton therapy (IMPT) for thoracic metastases. The patient showed no evidence of disease for 1 year after the initial radiotherapy, and no severe SABR-related adverse effects were observed until now. The combination of targeted therapy and immunotherapy with full-coverage radiotherapy may be a promising treatment option for selected patients with extensive metastatic renal cancer, especially as proton therapy allows for more precise control of the beam and minimal damage to normal tissue. This case has motivated us to investigate the potential advantages of administering proton therapy concurrently with systemic therapy in the management of metastatic renal cell carcinoma patients.

Proton beam therapy for muscle-invasive bladder cancer: A systematic review and analysis with Proton-Net, a multicenter prospective patient registry database

To assess the safety and efficacy of proton beam therapy (PBT) for muscle-invasive bladder cancer (MIBC), we examined the outcomes of 36 patients with MIBC (cT2-4aN0M0) who were enrolled in the Proton-Net prospective registry study and received PBT with concurrent chemotherapy from May 2016 to June 2018. PBT was also compared with X-ray chemoradiotherapy in a systematic review (X-ray (photon) radiotherapy). The radiotherapy consisted of 40-41.4 Gy (relative biological effectiveness (RBE) delivered in 20-23 fractions to the pelvic cavity or the entire bladder using X-rays or proton beams, followed by a boost of 19.8-36.3 Gy (RBE) delivered in 10-14 fractions to all tumor sites in the bladder. Concurrently, radiotherapy was given with intra-arterial or systemic chemotherapy of cisplatin alone or in combination with methotrexate or gemcitabine. Overall survival (OS), progression-free survival (PFS) and local control (LC) rates were 90.8, 71.4 and 84.6%, respectively, after 3 years. Only one case (2.8%) experienced a treatment-related late adverse event of Grade 3 urinary tract obstruction, and no severe gastrointestinal adverse events occurred. According to the findings of the systematic review, the 3-year outcomes of XRT were 57-84.8% in OS, 39-78% in PFS and 51-68% in LC. The weighted mean frequency of adverse events of Grade 3 or higher in the gastrointestinal and genitourinary systems was 6.2 and 2.2%, respectively. More data from long-term follow-up will provide us with the appropriate use of PBT and validate its efficacy for MIBC.

A Retrospective Study of Renal Growth Changes after Proton Beam Therapy for Pediatric Malignant Tumor

The purpose of this study was to analyze renal late effects after proton beam therapy (PBT) for pediatric malignant tumors. A retrospective study was performed in 11 patients under 8 years of age who received PBT between 2013 and 2018. The kidney was exposed in irradiation of the primary lesion in all cases. Kidney volume and contour were measured on CT or MRI. Dose volume was calculated with a treatment-planning system. The median follow-up was 24 months (range, 11-57 months). In irradiated kidneys and control contralateral kidneys, the median volume changes were -5.63 (-20.54 to 7.20) and 5.23 (-2.01 to 16.73) mL/year; and the median % volume changes at 1 year were -8.55% (-47.52 to 15.51%) and 9.53% (-2.13 to 38.78%), respectively. The median relative volume change for irradiated kidneys at 1 year was -16.42% (-52.21 to -4.53%) relative to control kidneys. Kidneys irradiated with doses of 10, 20, 30, 40, and 50 GyE had volume reductions of 0.16%, 0.90%, 1.24%, 2.34%, and 8.2% per irradiated volume, respectively. The larger the irradiated volume, the greater the kidney volume was lost. Volume reduction was much greater in patients aged 4-7 years than in those aged 2-3 years. The results suggest that kidneys exposed to PBT in treatment of pediatric malignant tumor show continuous atrophy in follow-up. The degree of atrophy is increased with a higher radiation dose, greater irradiated volume, and older age. However, with growth and maturation, the contralateral kidney becomes progressively larger and is less affected by radiation.

Carbon-ion radiotherapy for urological cancers

Carbon-ions are charged particles with a high linear energy transfer, and therefore, they make a better dose distribution with greater biological effects on the tumors compared with photons and protons. Since prostate cancer, renal cell carcinoma, and retroperitoneal sarcomas such as liposarcoma and leiomyosarcoma are known to be radioresistant tumors, carbon-ion radiotherapy, which provides the advantageous radiobiological properties such as an increasing relative biological effectiveness toward the Bragg peak, a reduced oxygen enhancement ratio, and a reduced dependence on fractionation and cell-cycle stage, has been tested for these urological tumors at the National Institute for Radiological Sciences since 1994. To promote carbon-ion radiotherapy as a standard cancer therapy, the Japan Carbon-ion Radiation Oncology Study Group was established in 2015 to create a registry of all treated patients and conduct multi-institutional prospective studies in cooperation with all the Japanese institutes. Based on accumulating evidence of the efficacy and feasibility of carbon-ion therapy for prostate cancer and retroperitoneal sarcoma, it is now covered by the Japanese health insurance system. On the other hand, carbon-ion radiotherapy for renal cell cancer is not still covered by the insurance system, although the two previous studies showed the efficacy. In this review, we introduce the characteristics, clinical outcomes, and perspectives of carbon-ion radiotherapy and our efforts to disseminate the use of this new technology worldwide.