SABR vs. SBRT: A New Deal for Radiotherapy Beyond Terminology

“Things are themselves and their circumstances. If I remove the circumstances, they cease to be.”

José Ortega y Gasset, Meditations on Quixote (1914)

Radiotherapy is the most effective treatment against cancer after surgery, contributing independently to the cure of approximately 40% of cancers (1). This effectiveness has been recognized almost since the discovery of X-rays, with their use reported just days after their discovery to treat a woman with breast cancer (2). The evolution of radiotherapy as a cancer treatment has been driven by three main pillars of both biological and technological advancement: increasing precision in its delivery, enhancing the administered dose and its biological efficacy, and reducing the total duration of treatment.

Although stereotactic radiotherapy has been known and used for a longer time, particularly in treating intracranial diseases, it was in 2010 that extracranial stereotactic radiotherapy gained formal recognition. This followed the publication of a seminal paper in the red journal, which defined the characteristics of this new approach to radiotherapy, later known as extracranial stereotactic radiotherapy. According to the authors, this is a form of external-beam radiotherapy (EBRT) based on high-precision systems for delivering high doses of radiation to extracranial targets in one or very few fractions, achieving steep dose gradients between the target and surrounding healthy tissues (3).

From that moment this modality of radiotherapy began to be known as SBRT (Stereotactic Body Radiation Therapy) —by analogy with cranial stereotactic radiosurgery techniques— gaining increasing prominence and convincing more oncologists of its safety and efficacy. This advanced form of EBRT represents a step toward precision oncology, echoing the Olympic motto, “Citius, Altius, Fortius” — faster administration, higher precision in target definition, and stronger doses. This progress has been underpinned by critical advancements: the ability to precisely localize the target thanks to imaging innovations, the precision in dose deposition facilitated by volumetric-modulated arc therapy/ intensity- modulated radiation therapy (VMAT/IMRT) and emerging adaptive radiotherapy (ART) techniques, tools to control both patient and tumor motion to reduce geographic errors, and, importantly, the radiobiological rationale for delivering high doses in fewer fractions to mitigate the effects of tumor repopulation (4,5).

However, the significance of stereotactic radiotherapy extends beyond technological refinements and precision in delivery. What makes it a game-changer in oncology are its strengths in cancer treatment: its dual action on the tumor’s cellular component and its supportive microenvironment maximizes tumoricidal effects; its effectiveness in traditionally radioresistant hypoxic regions eliminates even the least sensitive cellular components; and its potential to convert a “cold” (immunoresistant) phenotype into a “hot” (immunosensitive) one synergizes with advanced immunotherapy (6). Currently, SBRT is a standard option for selected cases of lung, kidney, liver, pancreas, and prostate cancers, vertebral metastases, and the radical treatment of oligometastatic disease (7-14). Furthermore, ablative precision treatment is emerging as a key therapeutic option, with consolidation in existing standard indications and expansion into new ones such as breast cancer, head and neck tumors, gynecological malignancies, and advanced polymetastatic disease (15-18).  The synergistic potential of SBRT with advanced therapies, such as immunotherapy is fostering better outcomes (19). Finally, reducing radiotherapy to just 1-3 fractions is now a reality for many tumors, embodying the concept of “cure in a week” with significant social, economic, and personal benefits for patients.

This therapeutic leap transcends technological advancements and focuses on the most critical goal of any treatment: curing the disease. Thus, the term SBRT began to seem insufficient, failing to capture the essential purpose of ars medica — healing. This led to the proposal of the term SABR (Stereotactic Ablative Radiation Therapy), which integrates the concept of ablation, of tumor elimination, of disease eradication, and ultimately, of cure (20). From this point on, a vigorous but metaphorically bloodless debate ensued, with the champions of the SBRT and SABR definitions entrenched in their respective Houses as in a modern Game of Thrones defending their position against the others. While words are important, the inherent circumstances that give them meaning are even more so. To cure sometimes, to relieve often, to comfort always is a statement that all doctors know and should never forget. And beyond the intentions of SBRT advocates, it seems reasonable from a clinical standpoint that SABR offers a more comprehensive definition, encompassing the technological backbone of precision oncology while focusing on the raison d’être of medicine: curing patient.

In conclusion, advocating for the possibility of healing not only through actions but also through words is a desirable aspiration. SABR offers us both: the real option to heal, to cure, to eliminate tumors, and the possibility of expressing it in plain words. But far beyond the terminological debate, it is undeniable that these advanced irradiation techniques are already transforming radiotherapy’s role in cancer treatment. SABR is not the future of radiotherapy, nor merely the present; it represents the dawn of a new deal for cancer cure. This paradigm maximizes the biological power of irradiation, overcomes traditional barriers in radiotherapy (such as distance to treatment centers and treatment-related costs), shortens treatment duration, and streamlines workflows, ensuring timely care for all patients.

Abbreviations

ART – adaptive radiotherapy

EBRT – external-beam radiotherapy

IMRT – intensity-modulated radiation therapy

SABR – Stereotactic Ablative Radiation Therapy

SBRT – Stereotactic Body Radiation Therapy

VMAT – volumetric-modulated arc therapy

Statements

Authors’ contributions: AM, HL and IR contributed equally to this article regarding preliminary idea, development, writing, editing and reviewing the manuscript.

Consent for publication: As the corresponding author, I confirm that the manuscript has been read and approved for submission by all named authors.

Conflict of interests: The authors declare no conflict of interest

Funding Sources: None

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