Kidney
2026-07-31
IROCK RCC SABR contouring guidelines
ForLocalized RCC treated with SABR, incl. IVC thrombus, recurrence, post-RFA
TL;DRFirst international consensus on target delineation for localized RCC SABR: 16 experts, median DSC 0.85 vs consensus, >0.70 in every case.
The two contested target calls are settled: include the entire tumor thrombus and the entire RFA cavity, and these were also the cases with most variation (DSC 0.85 and 0.75; HD 64.60 mm in Case 1). The 5 mm PTV assumes 4DCT, vacuum cushion, IV contrast and daily CBCT, so a center without those shouldn't copy the margin.
In a medically inoperable localized RCC with IVC tumor thrombus or recurrence after RFA, this supports covering the full thrombus or full ablation cavity in the iGTV; it does not settle the dose or fraction number, which the panel left institution-specific. The longer read
The two contested target calls are settled: include the entire tumor thrombus and the entire RFA cavity, the cases with most variation (DSC 0.85 and 0.75). The 5 mm PTV assumes 4DCT, vacuum cushion, IV contrast and daily CBCT, so it does not transfer unchanged to other workflows.
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Contouring consensus: 16 IROCK radiation oncologists contoured 4 CT-only cases; a STAPLE algorithm produced the 95% consensus contour, refined over 2 online meetings (May and June 2024) until 100% agreement on statements.
Panel eligibility: ≥10 RCC SABR cases treated; 14 of 16 had treated ≥10 pts in the prior 12 months. Cases: >10 cm tumor with IVC thrombus, central tumor at the hilum, post-nephrectomy recurrence, post-RFA residual.
iGTV equals ITV since no microscopic-spread margin is added. Most common PTV: uniform 5 mm on iGTV with supine vacuum cushion, 4DCT, IV contrast and daily CBCT. Participants used 1, 3, or 5 fractions; OAR constraints drawn from FASTRACK-II and AQuOS-II protocols.
Overall median DSC 0.85 (range 0.40-0.95), MDA 2.17 mm, HD 9.00 mm; median DSC >0.70 in every case. Greatest variation in Case 1 (superior thrombus extent) and Case 4 (cavity inclusion).
| Case | Scenario | iGTV recommendation |
|---|---|---|
| 1 | Tumor >10 cm with IVC tumor thrombus | Primary tumor + entire tumor thrombus; exclude bland thrombus |
| 2 | Central tumor abutting renal hilum | All visible tumor, account for internal motion; may extend into hilum |
| 3 | Local recurrence post-nephrectomy | All visible gross tumor; surgical clips need not be included |
| 4 | Residual tumor post-RFA | Visible gross recurrence + entire ablation cavity |
| Case | DSC | MDA (mm) | HD (mm) |
|---|---|---|---|
| 1 | 0.85, 0.79-0.85 | 6.69, 5.88-8.79 | 64.60, 64.44-86.40 |
| 2 | 0.90, 0.84-0.93 | 1.55, 1.00-2.09 | 7.92, 5.35-9.98 |
| 3 | 0.91, 0.88-0.93 | 1.42, 1.18-1.89 | 6.18, 6.00-7.12 |
| 4 | 0.75, 0.60-0.79 | 2.50, 2.12-2.99 | 9.00, 9.00-12.39 |
FASTRACK-II established prospective phase II support for RCC SABR; this document standardizes the target and OAR definitions that trial-era protocols left variable. AQuOS-II is prospectively testing whether ipsilateral parenchyma and hilum contours matter for toxicity.
CT-only images; MRI might have reduced variation. Participants did not recontour after consensus, so the post-consensus agreement is assumed rather than measured.
The guideline chooses OAR priority over coverage and accepts heterogeneous target dose, which trades some target coverage for bowel safety. Whether hilum or cortex sparing reduces renal toxicity remains unanswered and is deliberately left optional.
Expert contouring consensus; agreement metrics measure contour overlap, not outcome. Standardizes target definition for an emerging indication; not validated prospectively.
- Does renal hilum or cortex sparing reduce renal toxicity?
- Patterns of failure with the 5 mm PTV margin
- Does MRI-based contouring reduce target variation?
📚 Sources · 📄 1 paper
2026-05-18 ESTRO Congress 2026
FASTRACK II NCT02613819
ForPrimary RCC ≤10cm, T1b-dominant, medically inoperable or declined surgery
100% at 36, 60, 84 mo
ITT population, RECIST-assessed, median f/u 62 mo
TL;DR100% freedom from local progression at 36, 60, and 84mo after single-fraction 26Gy or 42Gy/3fx SABR in inoperable primary RCC.
The transferable detail is the size-adapted prescription: 26Gy in one fraction under 4cm, 42Gy/3fx above it, with median tumour 46mm and 65% T1b or higher. That is a larger-tumour cohort than most ablation series, and zero local failures out to 84mo supports offering SABR when a 77-year-old is turned down for nephrectomy.
In a medically inoperable or surgery-declining patient with a primary RCC up to 10cm, including T1b and larger where thermal ablation is a poor fit, this supports SABR as a durable local option; it does not speak to the operable patient, where nephrectomy remains untested against it. The longer read
The transferable detail is the size-adapted prescription: 26Gy single fraction under 4cm, 42Gy/3fx above it, in a cohort with median tumour 46mm and 65% at least T1b. Zero local failures to 84mo supports offering SABR when the patient is turned down for nephrectomy; bowel toxicity (two colonic obstructions) sets the technical ceiling.
This is the non-surgical arm of the small-renal-mass conversation getting real prospective follow-up, at a median tumour of 46mm where thermal ablation performs worst. It changes what you can tell a high-risk or surgery-declining patient at referral; it does not test SABR against partial nephrectomy in an operable patient, which remains unstudied.
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Non-randomised phase 2, eight hospitals in Australia and the Netherlands, run by TROG and ANZUP. Enrolment July 28 2016 to Feb 27 2020; 71 enrolled, one withdrew consent before treatment. This report is the pre-planned final follow-up at a median of 62 months (IQR 60-72).
Histologically confirmed primary RCC, medically inoperable, high risk, or declined surgery, ECOG ≤2, tumours ≤10 cm, N0-N1. Median age 77 years (70-82), 49 (70%) male. Median tumour size 46 mm (37-55), with 39 (56%) T1b, six (9%) T2a and one (1%) T3a.
Size-adapted prescription: 26 Gy in a single fraction for tumours ≤4 cm, 42 Gy in three fractions 48 h apart for tumours >4 cm. Histological confirmation was required before treatment, so this is a biopsy-proven cohort rather than a radiographic-diagnosis one.
Primary: freedom from local progression by RECIST, assessed in the intention-to-treat population, as was safety.
100% local control at 36, 60 and 84 months, with no local recurrences and no cancer-related deaths reported in the cohort.
Seven (10%) patients had at least one treatment-related grade 3 event within 9 months: pain in four (6%), nausea and vomiting in three (4%), colonic obstruction in two (3%), diarrhoea in one (1%). No grade 4 events and no treatment-related deaths; no new long-term safety signals emerged with extended follow-up.
A 100% point estimate in 70 pts carries a wide confidence bound that the headline hides, and RECIST is an imperfect local-control instrument after ablative RT, where a treated mass commonly persists without viable tumour. Renal function trajectory, the endpoint that actually competes with nephrectomy, is not reported in this source.
Prior SABR evidence in primary RCC was retrospective and pooled, so a prospective multicentre dataset at 84 months is the new contribution rather than the effect size itself. Comparison to partial nephrectomy and thermal ablation remains indirect: no randomised trial has run, and this cohort was selected against surgery by definition.
The finding that transfers is durability at a tumour size where thermal ablation performs worst, with a median of 46 mm and 65% at least T1b. What it does not settle is whether SABR is a choice rather than a fallback, which needs a randomised or matched comparison in operable pts, with renal function as a co-primary.
Single-arm phase 2, N=70, inoperable or surgery-declining pts only. No randomised comparator vs partial nephrectomy or thermal ablation. Maturity gate holds despite 62mo f/u.
- SABR vs partial nephrectomy in operable pts
- Renal function trajectory after SABR vs nephrectomy
- SABR vs thermal ablation in T1b tumours
📚 Sources · 📄 1 paper
Abstract
2026-05-17 ESTRO Congress 2026
RCC SBRT (5-year local control)
ForPrimary RCC treated with SBRT; stage and operability not stated in source
TL;DR100% local control at 5 years for RCC treated with SBRT, per a conference slide; no N, dose, or CI in source.
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Not reported in source. The tweet gives a 5-year local control figure with no study type, N, institution, or registry identifier, so design cannot be inferred.
SBRT to primary RCC; dose, fractionation, number of fractions, and target definition are not reported in source. These are the parameters that gate transfer to practice, and none are available here.
100% local control at 5 years as stated in the source tweet. No confidence interval, no n-at-risk, and no statement of whether this is a Kaplan-Meier estimate or a crude proportion.
Beyond the missing design, the specific risk is effective follow-up: a medically inoperable RCC cohort loses pts to non-cancer death well before 5y, so a 100% figure can rest on very few pts at risk. Local control definition (RECIST-style size change vs absence of growth vs biopsy) is also unstated and swings the estimate.
Single tweet with one number, no N, design, dose, or LC definition. Cannot judge whether the 100% figure reflects efficacy or short effective follow-up.
- Dose and fractionation behind the reported 5-year local control
- Local control definition and n-at-risk at 5 years
- SBRT vs partial nephrectomy in operable primary RCC
📚 Sources · 🐦 1 tweet
These results are so impressive!! 💯 local control at 5 years for RCC treated with SBRT@DrRanaMcKay @AdityaBagrodia @DrTylerStewart @DrYukselUrun @OncoAlert https://t.co/fUB3airM5g
— Tyler Seibert MD PhD (@TylerSbrt) May 17, 2026