New proofs supporting the efficacy of radiation therapy for kidney cancer 

February is the month when Cancer research UK raises awareness about kidney cancer. In 2020 over 400 000 people were diagnosed with this disease, and almost 180 000 died, worldwide. In the UK, there are over 13 000 new cases each year, on average, and almost 5000 lost lives. The peak incidence is from 65 to 74 years, so these patients frequently have other chronic health issues (1,2). As a result, supplementary challenges arise in the management of the disease.

The main treatment modality for non-metastatic patients is surgery, whenever feasible. However, the NCCN guidelines mention that Stereotactic Body Radiation Therapy (SBRT) may be considered for medically inoperable patients with stage I kidney cancer (better supported by current data) or with stage II/III kidney cancer (evidence still limited). Tumors that are limited to the kidney, have the maximum dimension less than 7 cm, and have not spread to the lymph nodes, are considered to be stage I (3).

Changing odds for radiation therapy in kidney cancer

A recent study shows very promising results for this category of patients. The multicentric phase II Trial of Focal Ablative STereotactic RAdiotherapy for Cancers of the Kidney (FASTRACK II) coordinated by the TransTasman Radiation Oncology Group (TROG) investigated the efficacy of SBRT for primary kidney cancer in patients who were inoperable or declined surgery.

Kidney cancer was traditionally considered “radioresistant”, due to suboptimal results of irradiation when using conventional fractionation (1.8 – 2 Gy/ fraction). However, the  SBRT has a stronger impact, due to different underlying biological processes that are triggered by high doses per fraction.

Throughout the lifetime of the trial, both local control and cancer-specific survival were 100%. Freedom from distant failure at 1 and 3 years was 99% and overall survival at 1 and 3 years were 99% and 82%, respectively. Grade 1 or 2 adverse effects were reported in 73% of the participants, grade 3 in 10%, and 16% had no treatment-related toxicity. The renal function had a mild impairment in the first 2 years and remained constant thereafter (4).

Safety matters

Apart from the excellent oncologic outcomes, the tolerability of the treatment and the limited kidney toxicity is important. Traditionally, when surgery was not possible, the only options for a local treatment were thermal ablations (either by heat or freezing). However, these procedures are invasive and can have significant local morbidity.

Previous data on SBRT efficacy for kidney cancer came from retrospective data or smaller single institution studies. If multiple clinics are involved in clinical trials, a relevant number of cases can be included faster. Advantages of multicentric trials come with some challenges, too. In order to have comparable results, the differences in the treatment received by all patients have to be as low as possible. Contouring, dose calculation, dose delivery and motion management have to be in line with the established protocol. For example, the detailed protocol of the FASTRACK II trial was published in 2018, including  target volume contouring, dose prescription, dose-volume constraints for the organs at risk, treatment planning, delivery and verification (5). In the 2023 abstract presenting the results it was mentioned that 14.3% of cases required resubmission for protocol deviation, and that final protocol compliance was 99.3% (4). This information underlines the importance of avoiding variations that can introduce bias in interpreting the data.

A helping hand for quality assurance

Inter-observer variability in contouring becomes a source of systematic errors, so quality assurance protocols are implemented to minimize the risk. An interesting review analyzed data coming from 5 clinical trials and found that major deviations in target volume delineation were found in up to 13.4% of RT plans (6). However, the numbers can be higher, since unacceptable contouring variations were sometimes communicated together with other types of protocol deviations.

Treating patients by using SBRT and hypofractionation leads to the need of higher treatment precision and subsequently a careful plan evaluation, where contouring plays an important role.

Fortunately, AI-based solutions can improve the homogeneity of treatments within clinical trials and in daily clinical practice. New evidence and treatment techniques emerge from both prospective and retrospective analyses. Treatment standardization, including contouring, will increase the quality of data coming from such studies and will allow more efficient updates in technology and recommendations.

Multiple evaluations came to the same conclusion: when using AI-based automatic predictions for contouring, the inter-observer variability decreases (7-9).  MVision AI offers a comprehensive set of more than 250 structures used in the radiation oncology practice (organs, lymph node regions and anatomical landmarks). Starting the contouring process with these fastly-delivered volumes increases efficiency and consistency. The unique guideline-based approach and the combined set of MVision AI’s Contour+, Guide and Verify, enables the radiation oncology team to provide excellent quality in the treatment planning process. 


  1. Kidney cancer statistics.
  2. Kidney cancer statistics.
  3. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) Kidney Cancer Version 2.2024 — January 3, 2024.
  4. S. Siva, et al. TROG 15.03/ANZUP International Multicenter Phase II Trial of Focal Ablative STereotactic RAdiotherapy for Cancers of the Kidney (FASTRACK II). International Journal of Radiation Oncology*Biology*Physics. Vol 117, Issue 2, Supplement, 2023,
  5. Siva S, Chesson B, Bressel M, et al. TROG 15.03 phase II clinical trial of Focal Ablative STereotactic Radiosurgery for Cancers of the Kidney – FASTRACK II. BMC Cancer. 2018;18(1):1030. Published 2018 Oct 23. doi:10.1186/s12885-018-4916-2
  6. Cox S, Cleves A, Clementel E, Miles E, Staffurth J, Gwynne S. Impact of deviations in target volume delineation – Time for a new RTQA approach?. Radiother Oncol. 2019;137:1-8. doi:10.1016/j.radonc.2019.04.012
  7. Strolin S, Santoro M, Paolani G, et al. How smart is artificial intelligence in organs delineation? Testing a CE and FDA-approved Deep-Learning tool using multiple expert contours delineated on planning CT images. Front Oncol. 2023;13:1089807. Published 2023 Mar 2. doi:10.3389/fonc.2023.1089807
  8. Turcas A, Leucuta D, Balan C, et al. Deep-learning magnetic resonance imaging-based automatic segmentation for organs-at-risk in the brain: Accuracy and impact on dose distribution. Phys Imaging Radiat Oncol. 2023;27:100454. Published 2023 Jun 6. doi:10.1016/j.phro.2023.100454
  9. Kiljunen T, Akram S, Niemelä J, et al. A Deep Learning-Based Automated CT Segmentation of Prostate Cancer Anatomy for Radiation Therapy Planning-A Retrospective Multicenter Study. Diagnostics (Basel). 2020;10(11):959. Published 2020 Nov 17. doi:10.3390/diagnostics10110959

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