PS1424 The CRAB score: a simple prognostic tool in multiple myeloma

Background: Current prognostic scoring systems in multiple myeloma lack consensus and are often clinically impractical. The key diagnostic features known as CRAB; hypercalcaemia (C), renal impairment (R), anaemia (A), and bone lesions (B), are known to represent end organ damage in myeloma. Aims: We aimed to produce a simplified and practical prognostic tool for use in multiple myeloma patients as an alternative to current practice, therefore enabling prognostic guidance to be distributed to a wider group of patients. Since the laboratory tests required to calculate CRAB score are routinely undertaken in clinical practice, we proposed a method of predicting outcome based on these results alone, which has not yet been reported. Methods: We examined a combined database of clinical and survival information for 314 patients from Brighton and Worthing, Sussex, UK, over a 6 year period, who were newly diagnosed with myeloma, and represent real-world clinical experience. To determine the presence of a CRAB feature, the cut-off values previously defined by the International Myeloma Working Group (IMWG) were used; serum calcium >2·75 mmol/L, serum creatinine >177 µmol/L, haemoglobin <100 g/L (or >20 g/L below lower limit of normal), and one or more osteolytic lesion on skeletal radiography, CT, PET-CT or MRI. Patients were stratified into five CRAB score groups by having either 0, 1, 2, 3 or 4 CRAB features at initial presentation, with a score of 0 denoting a diagnosis of smouldering myeloma. We then studied the relationship between CRAB score and overall survival using Kaplan Meier curves plotted by the statistics programme SPSS. Results: Our analysis reveals that each additional CRAB feature confers a stepwise statistically significant poorer outcome in terms of overall survival as shown in Figure 1a. This result was regardless of the treatment regimen the patient received and gave 5-year survival percentages of 81%, 58%, 41%, 22% and 0% for patients with CRAB scores 0–4 respectively. We also found CRAB score to have coherence with the current International Staging System (ISS) scoring system, which combines serum albumin as a measure of general patient health with ß2-microglobulin as a measure of tumour bulk to estimate risk. Cytogenetic data required for the revised ISS score was not undertaken for the majority of patients, highlighting the lack of feasibility of this system in practice, although we did observe higher CRAB scores for those patients identified with poor risk chromosomal abnormalities. A trend for higher ISS score with higher CRAB score was observed, further validating the CRAB scoring system (figure 1b). Image Summary/Conclusion: Our study shows that the CRAB score yields accurate prognostic predictions for patients with newly diagnosed multiple myeloma based on simple clinical criteria. It has more prognostic categories than the currently used ISS score (5 versus 3) and superior clinical utility than expensive and time-consuming cytogenetic-based scoring systems that have been recently described. These results indicate that the CRAB score may provide a useful and reliable tool to guide prognostic evaluation in newly diagnosed myeloma patients, requiring only routine laboratory testing to be undertaken, and therefore greater availability to patients in diverse clinical settings.