Validation of MY-RADS response assessment category criteria

Response assessment category (RAC) criteria, based on diffusion-weighted whole-body MRI (DW-MRI) and proposed by the Myeloma Response Assessment and Diagnosis System (MY-RADS) imaging recommendations were able to independently stratify patients with different outcomes, promoting the standardisation in reporting functional imaging response after treatment.

DW-MRI permits calculation of the apparent diffusion coefficient (ADC) and the production of a quantitative ADC map in multiple myeloma (MM) [1]. However, consistent data regarding its prognostic role in the detection of minimal residual disease (MRD) after treatment in MM are lacking. To promote standardisation in response assessment, MY-RADS imaging recommendations were published in 2019 [2]. RAC criteria have been proposed with a 5-point scale ranging from a high probability of complete imaging response (RAC 1) to a high probability of progressive disease after treatment (RAC 5). However, this score still needs to be validated in clinical practice.

Dr Angelo Belotti (ASST Spedali Civili di Brescia, Italy) performed an external validation of RAC criteria according to MY-RADS in newly diagnosed MM patients [3]. They retrospectively analysed outcomes of 60 MM patients (median age 63 years) who underwent DW-MRI evaluation to assess the response past day 100 after autologous stem cell transplantation, before maintenance. Results were correlated with those of MRD assessment by flow cytometry.

Based on imaging, complete response (CR) after transplant was observed in 36 patients (RAC 1: 60%). Some residual disease was identified in 24 patients (RAC 2-4: 40%). After a median of 28 months, progression-free survival was significantly longer in patients with RAC 1 versus RAC ≥2 (HR 0.29; 95% CI 0.10-0.80; P=0.017). Concordance between DW-MRI and flow cytometry results was low (16% both positive, 36% both negative). PFS was significantly better for patients with both RAC 1 and MRD-negative status compared with patients having MRD-positivity based on either or both detection methods (P=0.021; see Figure).

Figure: PFS in separate RAC categories [1]



PFS, progression-free survival; RAC, response assessment category; MRD, minimal residual disease

The current validation of RAC criteria highlights the ability of DW-MRI to stratify patients with different outcomes. The low concordance between DW-MRI response and flow cytometry MRD results suggests that these 2 techniques may be complementary for the definition of response. Their combined use could help clinicians to better refine the prognosis of MM patients.

1. Rasche L, et al. Leukemia. 2019;33:1713-1722.
2. Messiou C, et al. Radiology. 2019;291:5-13.
3. Belotti A, et al. External Validation of Diffusion Weighted Whole Body MRI (DW-MRI) Response Assessment Category (RAC) Criteria Proposed By the Myeloma Response Assessment and Diagnosis System (MY-RADS) Imaging Recommendations: Prognostic Role of Imaging Response after Transplant in Multiple Myeloma and Comparison with MRD Evaluation By Flow Cytometry. 62^nd ASH Annual Meeting, 5-8 December 2020. Abstract 145.

Posted on 18 February 202122 February 2021