External Beam Radiation Therapy (EBRT) for Neuroendocrine Neoplasms

Disclaimer: The information in this section is for education only and does not represent a standard care pathway or service. These treatments are not suitable for everyone, and careful patient selection by an experienced multidisciplinary team is essential. Always discuss your individual situation with your own specialist team.

External Beam Radiation Therapy (EBRT) is an established medical treatment with roots dating back to the late 19th century, but modern EBRT is far more precise, and new technologies now allow safer treatment of tumours that were previously difficult to target. It uses high‑energy beams to damage cancer cells. The use of the term ‘External Beam Radiation Therapy’ means the same when ‘External Beam Radiotherapy’ is used.

I wrote this blog because there is evidence via some studies (and anecdotally in my patient group) that EBRT has been used to treat patients with NETs (including Grade 3), In Neuroendocrine Neoplasms (NENs), it can be used selectively depending on tumour type, location, grade, and the overall treatment plan. Its use is infrequent indicating patient selection is an important criterion, and perhaps access to treatment is a factor too. It’s not for everyone!

Note: This post only covers EBRT, which uses machines outside the body to target tumours. It should not be confused with Peptide Receptor Radionuclide Therapy (PRRT) which is a totally different type of radiotherapy normally delivered internally via a cannula. You can read more about PRRT by clicking here. Radiation therapy and radiotherapy are largely interchangeable terms, both referring to the use of high-energy radiation to treat cancer, though some distinctions may exist in scope and delivery methods.

How does EBRT work?

To fully understand, it’s important to understand the main 3 layers of EBRT:

– the technique (or ‘type’ of EBRT),
– the platform,
– the imaging guidance.

One of the reasons I include these distinctions is because the these terms get used interchangeably, particularly inside patient support groups (and on medical sites!) where a patient/caregiver uses the technique or the platform in different contexts, i.e. the conversation becomes muddled riddled with ‘synonym soup’.

a. EBRT techniques/types

These describe how the radiation dose is delivered. e.g.

IMRT / VMAT — shape the radiation beam to match the tumour while sparing nearby organs.
Stereotactic Body Radiotherapy (SBRT) — very precise, high‑dose treatment delivered in a small number of sessions. Effective for bone, lung, liver, and some adrenal NETs. You may see this called Stereotactic Ablative Radiotherapy (SABR) outside North America.
Stereotactic Radiosurgery (SRS) – despite the name, this is not surgery. It it stereotactic radiotherapy to the brain.
Adaptive radiotherapy — the plan is adjusted daily based on that day’s anatomy. Useful for tumours that move or sit close to sensitive organs.
IMPT (Intensity‑Modulated Proton Therapy) — the proton‑based equivalent of IMRT, used in selected cases.

These techniques can be delivered on different machines depending on the clinical situation.

**b. EBRT platforms (i.e. the machine that delivers the beam) – (e.g. Varian, Elekta, CyberKnife®, etc.)**

These machines generate and shape the radiation beam. They differ in precision, imaging capability, and suitability for soft‑tissue tumours. They can utilise different techniques/types (examples above) and depending on the platform being used, they can utilise different imaging devices such as X-ray, CT, MRI; e.g.

Conventional LINAC (linear accelerator) The most common radiotherapy machine worldwide. Delivers high‑energy X‑rays (photons). Suitable for many NEN sites, especially bone, lung, and some liver lesions.
CyberKnife® (a robotic LINAC) A trademarked specialised LINAC mounted on a robotic arm. Delivers photon SBRT with sub‑millimetre precision and real‑time X‑ray tracking. Often used for lung, spine, prostate, and selected liver lesions.
MRI‑LINAC (MRI‑guided radiotherapy) Combines a LINAC with real‑time MRI. Allows continuous visualisation of soft tissues and daily adaptive planning. Particularly useful for tumours that move or sit close to sensitive organs — such as pancreatic NENs.
Proton therapy systems Use charged particles (protons) instead of X‑rays. These machines are cyclotrons or synchrotrons, not LINACs. Protons deposit most of their energy at a specific depth (the Bragg peak), reducing dose to surrounding tissues. Best suited to fixed, predictable anatomy (brain, skull base, paediatrics). Less commonly used for ‘mobile’ abdominal organs such as the pancreas, stomach and intestines.

c. Imaging guidance (how the tumour is seen and tracked)

Imaging determines how accurately the tumour can be targeted.

Cone‑beam CT (CBCT) — standard on most LINACs; good for bone and lung but limited for soft‑tissue organs such as the pancreas or bowel.
X‑ray tracking — used by CyberKnife® to follow tumour motion, often with implanted fiducials.
MRI guidance — used on MRI‑LINACs; provides clear soft‑tissue visibility and real‑time tracking. Allows the beam to pause automatically if the tumour moves.

Example – Putting the 3 layers together

SBRT (the technique) delivered on a Varian LINAC (the platform) using cone‑beam CT for daily image guidance (the imaging). See classic example in this picture (credit Macmillan Cancer Support). The platform and imaging is clear, you don’t formally not see the technique/type as that is part of the platform’s programming. p.s. the Cyberknife platform looks totally different as it uses a robotic arm.

External beam radiotherapy — Linear Accelerator (LINAC). Picture credit to Macmillan Cancer Support

Where EBRT fits in NEN treatment

You won’t find much of this in guidelines but there are studies and suggested use in papers. For example, SBRT is not listed as a standard of care in any major NEN guideline, including NCCN, ENETS, NANETS, or ESMO. This is because radiotherapy plays a selective, rather than central, role in NET management. That said, SBRT is mentioned in the NCCN guidelines in several site‑specific contexts, and there is a growing body of NET‑specific evidence supporting its use in carefully chosen situations. Worth pointing out that like many NEN treatments, the use of EBRT has risks as well as benefits and that should be explained by treating specialist.

References:

1. External Beam Radiotherapy in the Treatment of Gastroenteropancreatic Neuroendocrine Tumours: A Systematic Review

2. Several NET Centres discuss the use of EBRT as a treatment e.g. Moffatt – click here

3. Several NET Centres discuss the use of EBRT as a treatment e.g. Roswell Park – click here

3. Some early work on a ‘combo’ treatment using PRRT and EBRT – click here

4. The American Cancer Society (ACS) mentions radiation therapy for Lung NETs as an option for those who can’t have surgery. Click here.

5. Click here to read a previous compilation of EBRT capability by Ronny Allan, particularly emphasising the technique SBRT in Neuroendocrine Neoplasms.

6. Nice overview from Cleveland Clinic – click here

Disclaimer

I am not a doctor or any form of medical professional, practitioner or counsellor. None of the information on my website, or linked to my website(s), or conveyed by me on any social media or presentation, should be interpreted as medical advice given or advised by me.

Neither should any post or comment made by a follower or member of my private group be assumed to be medical advice, even if that person is a healthcare professional. Some content may be generated by AI which can sometimes be misinterpreted. Please check any references attached.

Please also note that mention of a clinical service, trial/study or therapy does not constitute an endorsement of that service, trial/study or therapy by Ronny Allan, the information is provided for education and awareness purposes and/or related to Ronny Allan’s own patient experience. This element of the disclaimer includes any complementary medicine, non-prescription over the counter drugs and supplements such as vitamins and minerals.

General Clinical Trials Disclaimer

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided in the clinical trials document. It’s very important to check the trial inclusion and exclusion criteria before making any contact. If you need questions, the articles here is very useful Questions to Ask About Clinical Trials | Cancer.Net

The inclusion of any trial within this blog should not be taken as a recommendation by Ronny Allan.

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