Interest in Stereotactic Ablative Radiotherapy (SABR) is currently high. Following a four-year commissioning through evaluation (CtE) programme, NHS England have announced that SABR will now be routinely commissioned for oligometastases, establishing it as a standard of care. I wanted to take this opportunity to update the Medical Oncology community on the current indications and evidence for SABR, and the GenesisCare SABR clinical strategy.
What is SABR?
SABR, also known as Stereotactic Body Radiotherapy(SBRT), uses very high doses of radiotherapy delivered very accurately in a small number of fractions (typically 1-8). This increases the likelihood of ablating the treatment target. Safe and effective delivery of SABR requires the use of modern image guidance techniques and specially trained treatment staff. Most SABR treatments can be delivered using a modern conventional linear accelerator (as with standard radiotherapy). More recent technology developments provide additional value in certain cases. For example,the MR Linac offers greater soft tissue resolution,dynamic tumour tracking, and the ability to adapt the treatment plan to daily changes in tumour and normal tissue anatomy, increasing the accuracy of delivery.
Clinical use of SABR
SABR is the established standard of care for patients withearly stage non-small cell lung cancer who are unfit for, ordecline, surgery. The CHISEL trial1 has confirmedsuperiority over conventionally fractionated radiotherapy(CFR). There is a very large international experience ofusing SABR to treat organ-confined prostate cancer, witha 10 year follow up reported from some centres. The recent HYPO2 and PACE3 trial publications have shown equivalence between SABR and CFR with regard to 5-year failure free survival and acute toxicity respectively. SABR has also been used to treat primary hepatocellular carcinoma (HCC) in the UK as part of the NHS CtE programme, with some excellent results seen, as well as offering an entirely non-invasive and ablative approach for patients with inoperable or locally recurrent pancreatic cancer.
The use of SABR to treat oligometastatic disease (up to 3-5 metastases) is rising steadily. The number of publications has increased year on year since 2005, and we now have randomised evidence of benefit in this patient group. The SABR-COMET study 4 demonstrated improved overall survival with the addition of SABR to standard of care (median OS 28 months vs 41 months),across a range of different tumour types. An update from the STOMP trial at this year’s GU ASCO5 has shown that SABR increased the five-year androgen deprivation therapy (ADT) free survival from 8% to 34%, when compared to surveillance, in men with oligometastatic prostate cancer. In this way, the ablation of oligometastases can delay exposing men to the side effects of long-term ADT.
There is also growing evidence for the use of SABR in“oligoprogressive” disease. This refers to patients with more widespread metastases previously under control with systemic therapy, and now progressing at up to three sites. Treating the sites of progression can allow continuation of the current systemic therapy, delaying the need to switch to the next line of treatment. There is particular interest in this approach for patients well established on systemic targeted therapy orimmunotherapy agents.
Click here for free access to the long term follow up data from the SABR-COMET trial, showing a significant overall survival benefit for SABR in oligometastic disease#
SABR at GenesisCare
The GenesisCare SABR strategy is focused upon increasing patients’ access to SABR and ensuring high quality treatment, aligned to international best practice,across the GenesisCare network.
We have a national SABR Reference Group and Advisory Team which has written evidence-based treatment protocols and runs a twice-weekly virtuale MDT for review of prospective SABR cases. The team also runs training workshops to enable the credentialing of Clinical Oncologists new to SABR and provides peer review of the first few cases for these Consultants.
How to refer a patient for SABR
Refer to any clinical oncology colleague at your local GenesisCare centre with the appropriate credentialing.Your centre manager will be able to provide a list of SABR approved Consultants.
You can refer these cases in the same process if your local centre also delivers Complex SABR. Otherwise you can refer to a centre delivering Complex SABR via the SABR Coordinator, Lisa Meade, firstname.lastname@example.org, 07391392605
Clinical Director – Stereotactic Radiotherapy GenesisCare