Magnetic resonance image-guided radiotherapy assessed in Swedish Västra Götaland region

In Sweden, the County Councils are grouped into six healthcare regions to facilitate cooperation and to maintain a high level of advanced medical care. One of them is the Västra Götaland County Council with its Health Technology Assessment (HTA) Center, which aimed to work for the continuous development of knowledge-based care in the region and ensure that healthcare is supported by science and evaluation. Also, it should follow up on the development of evidence-based healthcare nationally and internationally.

In the middle of May 2020, Västra Götaland HTA-Centre published a health technology assessment on magnetic resonance image-guided radiotherapy (MRgRT) in patients with cancer in thorax, abdomen, pelvis or head and neck that aimed to assess whether the method improves treatment results compared to current methods. Overall survival and health-related quality of life (HRQL) were considered critical outcomes for decision making. In this regard, a systematic literature search was conducted in January 2019 with an update in November 2019 in PubMed, Embase, and the Cochrane Library. The certainty of the evidence was assessed using the GRADE approach.

The following outcomes were reported:

• Critical outcomes:
  • None of the included studies provided comparative data for the critical outcomes overall survival or HRQL
• Important outcomes:
  • Among important outcomes, toxicity, progression-free survival, treatment time, the proportion of cases with replanning of treatment, patient treatment experience, and partial or complete response, only case series were available
  • However, several publications provided within-subject comparisons for the intermediate outcomes organs at risk constraint violation (7 studies) and target coverage (8 studies)
    • Here, the initial non-adapted plan for each patient and the MR-guided adapted plan for the same patient were calculated and compared regarding the calculated target coverage and avoidance of dose to organs at risk
    • These studies had no problems regarding directness, but some limitations in study quality and precision. A key limitation was that the new technique of adaptive MRguidance was the “reference standard” in the comparison, which implies that only differences in favor of the new technique could be detected
    • Accordingly, analyses showed that organs at risk constraints were violated less often in the MR-guided adapted plan than in the non-adapted plans. In the context of the above limitations, it is concluded that MRgRT, when used as reference standard, may be associated with a lower number of organs at risk constraint violations compared to RT without MR-guidance (low certainty of evidence)
    • The same studies also consistently showed better target coverage for the MRgRT than RT without MRguidance. Considering the same limitations as above, it is concluded that MRgRT, when used as the reference standard, may be associated with a higher proportion of treatment sessions reaching planning target volume coverage goals compared to RT without MR-guidance (low certainty of the evidence)

The following conclusions were provided:

• For critical clinical outcomes - overall survival and HRQL - no comparisons of MRgRT with current methods are available. This also holds for the important outcomes toxicity, progression-free survival, treatment time, patient treatment experience and partial or complete response
• For two intermediate endpoints within-subject comparisons of treatment plans based on both methods – using the new technique as reference standard - are available: the new technique may be associated with a higher proportion of treatment sessions reaching target coverage goals and a lower number of treatment sessions with violations of organs at risk constraints. However, the extent of improvement varied substantially between studies, and the certainty of the evidence is low. It remains to be seen, whether, and for which patient population the reported advantage in intermediate endpoints may translate into an improved benefit-risk balance of the new compared to the present technique
• Treatment sessions with MRgRT are presumably 3-4 times longer than with current methods, and the need to stay in the same body position during extended times may be difficult for the elderly as well as patients in pain. Economic aspects including high investment costs and the considerable increase in time and clinical staff needed for MRgRT are further challenges and imply a risk for displacement effects

Full report in English could be found here.

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