Revised International Staging System (R-ISS) for Transplant-Eligible Multiple Myeloma Patients Risk Stratification

BACKGROUND: In the last decades, multiple myeloma (MM) prognosis has been changing dramatically. Induction with novel agents, followed by high-dose melphalan and autologous hematopoietic stem cell transplantation (aHSCT) is the standard of care for newly diagnosed (ND) and transplant-eligible MM patients (pts). In 2015, a new score was validated [Revised International Staging System (R-ISS)], including data related to high-risk cytogenetic abnormalities (CA) [del(17p) and/or t(4;14) and/or t(14;16)] and serum lactate dehydrogenase (LDH) levels. Few recent studies have supported R-ISS as a reliable prognostic tool for estimating survival in MM pts submitted to aHSCT.

AIMS: To determine whether R-ISS is a valid risk model for predicting progression free survival (PFS) and overall survival (OS) among a cohort of real-life aHSCT pts.

METHODS: We conducted a single center retrospective study of ND symptomatic MM pts treated with novel agents (bortezomib, thalidomide or lenalidomide) undergoing aHSCT between Jan/2007 and Dec/2017. We excluded all pts with no available information about ISS, LDH and CA [detected by fluorescence in situ hybridization (FISH)]. Response to treatment was evaluated according to the International Myeloma Working Group consensus criteria (2016). Statistical analysis was performed using STATA v.14.2 and significant levels were set at p<0.05.

RESULTS:

From the total number of 186 pts submitted to aHSCT, only 81 (45%) pts presented criteria to be included in our analysis; 62% were male, with a median age at aHSCT of 60y (28-70). IgG was the most frequent subtype (59%), followed by IgA (20%). At diagnosis, 38% of pts presented anemia, 14% renal impairment (RI), 20% hypercalcemia, 63% bone disease (BD) and 32% extramedullary disease (EMD). According to ISS, 30 (37%) pts presented stage I, 30 (37%) stage II, and 21 (26%) stage III at diagnosis. There were 38% pts with high-risk CA: 24% with del17p; 19% with t(4;14), and 20% with t(14;16). High LDH levels was seen in 48% of pts. Pts were re-staged at diagnosis according to R-ISS, resulting 17% in stage I, 61% in stage II, and 22% in stage III. Thus, 16 (20%) pts previously categorized as ISS I and 3 (4%) pts as ISS III were re-classified as R-ISS II. Median time from diagnosis to aHSCT was 9.7 months. All pts received induction therapy with novel agents (a bortezomib-based therapy in 89% of pts and an IMID-based in 12%), with 81% of pts responding to first line induction; 19% were refractory. At the time of aHSCT, all pts presented at least on partial response (PR) [62% at least very good partial response (VGPR)], with an increase in the proportion of pts in complete response (CR) from 15% to 20% before and after aHSCT, respectively. Maintenance therapy was performed in 31% of pts (79% thalidomide; 21% lenalidomide).

At a median follow-up of 33.4 months, median OS had not been reached. Two-years OS was 62%. Median PFS from aHSCT was 67.4%.Neither high-risk CA nor high LDH levels individually predicted lower OS and PFS (p=NS). The 2-year OS for R-ISS I, II and III was 86 %, 61% and 44%, and the 2-year PFS was 79 %, 63% and 39%, respectively. In our cohort we observed statistical significance differences between R-ISS I and III at 2 years in what concerns PFS (p=0.025) and OS (p=0.017) . No differences were seen in between other R-ISS categories. When we stratified R-ISS stage II in two subgroups based on the presence or absence of high-risk CA no differences were found. Pts classified as R-ISS III presented anemia (p<0.001) and RI (p=0.001) more frequently, but no differences concerning hypercalcemia, BD or EMD.

CONCLUSIONS: In our real-life cohort, R-ISS at diagnosis was a reliable tool only to predict both OS and PFS between R-ISS I and III and not between other R-ISS subgroups. The main reasons that explain the absence of significance between all R-ISS subgroups were probably the very low number of pts with available cytogenetics compared with the total number of pts submitted to aHSCT in our center and the short follow up of our study. Larger real-life studies with a longer follow up are necessary to determine if R-ISS is a good risk stratification model to applicate to NDMM pts submitted to aHSCT in the era of novel agents.