Ongoing MOMENTUM study highlights safety of Elekta Unity MR-Linac

Elekta Mr Linac 1548
Jun 20, 2022 2 minute read

For 1,800 cancer patients and counting, radiotherapy treatment on Elekta Unity has consistently resulted in low rates of side effects.

On behalf of Elekta Unity researchers at eight centers in five countries, University Medical Center Utrecht (UMCU) investigator Jasmijn Westerhoff, MD, recently presented the latest results from the MOMENTUM multi-institutional international registry at ESTRO 2022 in Copenhagen, Denmark.

Jasmijn Westerhoff, MD
Jasmijn Westerhoff, MD

According to the study, of nearly 1,800 cancer patients treated with Elekta Unity, only 1.4 percent experienced any grade 3 radiation-related side effects and none experienced severe radiation side effects (defined as grade 4 or 5) within the first three months post-radiotherapy. In addition, of the subset of approximately 1,000 patients who were treated using the full on-line adaptive workflow (the most personalized form of MR-guided radiation therapy), only 0.4% experienced any Grade 3 toxicity (no Grade 4 or 5).

These results reinforce the findings of the first interim MOMENTUM paper1 that reported on the initial 943 patients treated with Elekta Unity. “Now with almost 1,800 patients treated, we have even larger-scale evidence that acute severe toxicity is uncommon,” Dr. Westerhoff says.

While most of the patients were treated for brain cancers, prostate cancers and oligometastatic disease in lymph node cancers, the MOMENTUM study has accumulated data for over 40 different treatments sites throughout the body (Table 1).

“Our data show that the MR-Linac is being used for a wide variety of indications.”

“Our data show that the MR-Linac is being used for a wide variety of indications,” she says. “As the sample sizes grow for each of these treatment sites, we can begin to make ever more precise estimates of side effect rates for each kind of treatment.”

In addition, rigorously documenting toxicities associated with MR-guided radiation therapy using recognized standard fractionation schedules opens the door for the next phase of the project, which is to use the MOMENTUM study as a platform for evaluating investigational treatment approaches enabled by a high-field MR-Linac.

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“We can start fine-tuning therapies with strategies such as hypofractionation and dose escalation to determine how that will affect toxicity,” Dr. Westerhoff says. “In addition, within MOMENTUM, we are working to expand the study to include new treatment sites and more participating centers, which means considerably more patients will be included. That’s something that is very exciting for the future.”

While the ESTRO abstract reported outcomes from eight institutions, an additional three cancer centers have joined the project.

Table 1. Elekta Unity treatment sites and patients

Treatment Siten = patients
Lymph node233
Liver & intrahepatic ducts108


  1. de Mol van Otterloo SR, Christodouleas JP, Blezer ELA, et al. Patterns of care, tolerability, and safety of the first cohort of patients treated on a novel high-field MR-Linac within the MOMENTUM Study: Initial results from a prospective multi-institutional registry. Int J Radiat Oncol Biol Phys. 2021 Nov 15;111(4):867-875. doi: 10.1016/j.ijrobp.2021.07.003. Epub 2021 Jul 13. PMID: 34265394.

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