PB2149 NUMBER OF INVOLVED BONE REGIONS IS A SIMPLE AND USEFUL PREDICTIVE MARKER OF EARLY DISEASE PROGRESSION AND DEATH IN NEWLY DIAGNOSED MULTIPLE MYELOMA PATIENTS

Background: The number or size of focal lesions (FL) on whole‐body magnetic resonance imaging (MRI) or positron emission tomography integrated with computed tomography (PET‐CT) was shown to be associated with poor prognosis in multiple myeloma (MM) patients. However, it is complicated to determine the number or amount of FL on MRI or PET‐CT imaging and patients cannot always undergo such medical imaging examination at diagnosis for many reasons. Therefore, developing simple method to estimate the amount of tumor burden from imaging data may be useful to predict prognosis of MM patients under various conditions. Aims: The aim of this study was to assess whether the number of involved bone regions at diagnosis could become a predictive marker of disease progression and survival in newly diagnosed MM patients. Methods Clinical and imaging data of patients newly diagnosed with MM and immediately treated with chemotherapy from January 2013 to August 2018 at the institution were evaluated retrospectively. All imaging data had been interpretated by experienced radiologists. Each bone lesion was sorted according to 8 anatomical regions: skull, rib including clavicula, scapula, sternum, spine, ilium, upper limb, and lower limb. Factors associated with progression‐free survival (PFS) or overall survival (OS) were statistically analyzed using log‐rank test and Cox regression model. Results: Eighty‐three evaluated patients had a median age of 69 years old (yo) (range: 45‐92). 9% of them were classified as revised International Staging System (R‐ISS) stage 3. As imaging tools for evaluation of bone disease, CT and additional skeletal x‐ray were conducted in all cases, MRI (of not the whole‐body, usually of the spine) in 80%, PET‐CT in 45% and bone scintigraphy in 16%. Median number of involved bone regions was 2 (range: 0‐8). 9% of patients had no bone disease and 46% had bone lesions in at least 3 different regions. The most involved region was spine (77%) following rib (46%), ilium (38%), lower limb (27%), sternum (26%), skull (24%), upper limb (21%), and scapula (13%). Only 3 patients had extramedullary disease (EMD). 95% of patients were initially treated with therapeutic regimen containing bortezomib or lenalidomide, 34% combined with radiation, and 6% followed by surgery. Autologous transplantation was performed in only 11 patients (13%). With a median follow‐up of 26 months (range: 0‐72 months), 2‐year PFS and OS for all patients were 48% and 78%, respectively. The presence of bone lesions in at least 3 regions (PFS; P =. 035, OS; P =. 018), advanced age (>65 yo, PFS; P =. 039, >74 yo, OS; P =. 007), low hemoglobin level (<10 g/dL, PFS; P =. 030, OS; P =. 058), decreased renal function (creatinine clearance <40 ml/min, PFS; P =. 032, OS; P =. 017), high collected serum calcium level (>11 mg/dL, PFS; P =. 020, OS; P =. 027), R‐ISS stage 3 (PFS; P =. 002, OS; P =. 004) and EMD (PFS; P =. 023, OS; P <. 0001) adversely affected both PFS and OS. In a multivariate analysis, the presence of bone lesions in at least 3 regions (HR: 2.74, P =. 004), advanced age (>65 yo, HR: 3.05, P =. 002) and EMD (HR: 33.0, P =. 029) were significantly associated with inferior PFS. Also the presence of bone lesions in at least 3 regions (HR: 3.04, P =. 025) and EMD (HR: 51.7, P =. 004) were independent risk factors in OS. Summary/Conclusion: Our results suggest that the presence of bone lesions in at least 3 different regions at diagnosis is a beneficial factor for predicting early progression and death, which can be easily evaluated using conventional imaging system at almost any institutions.