Bortezomib Overcomes Poor Prognosis Conferred By High Sictp in Untreated Plasma Cell Disorders

Introduction

To date, various biochemical markers of bone remodeling have been investigated in multiple myeloma (MM) patients. Serum C-terminal telopeptide of type I collagen (sICTP) is a well-known biochemical marker of bone remodeling. Although several reports showed the relationship between a high level of sICTP and poor prognosis in MM patients, little is known about the efficacy of bortezomib in high sICTP patients. In this single center retrospective study, we assessed the association between sICTP and the prognosis of plasma cell disorder patients, particularly in patients firstly treated with bortezomib-containing regimen.

Methods

We retrospectively reviewed untreated MM and other plasma cell disorder patients who were diagnosed at The University of Tokyo Hospital between January 2001 and December 2016. The clinical data of patients whose sICTP was measured before the start of first-line therapy were collected. Serum ICTP was measured at diagnosis in 59 patients: 56 patients with MM, 2 patients with plasmacytoma, and 1 patient with light chain amyloidosis. These patients were divided into high sICTP and low sICTP groups according to the median of sICTP level. Additionally, patients firstly treated with bortezomib-containing regimen were divided into two groups according to the median of sICTP level. Overall survival (OS) and bone fracture-free survival (FFS) were calculated from initiation of the first-line therapy using the Kaplan-Meier method and log-rank tests.

Results

In 59 patients, the median age was 65 years (range, 45-85 years) and median follow-up was 387 days (range, 22-2019 days). Thirty-three patients (55.9%) were male and 26 (44.1%) were female. IgG was the most frequent subtype of M-protein (58%), followed by IgA (19%), Bence Jones proteins (19%), and IgE (3%). International scoring system classified 16 (27.1%), 24 (40.7%), and 19 (32.2%) as stage I, II, and III, respectively. Levels of sICTP were high in 31 (52.5%) patients and low in 28 (47.4%) patients. The level of sICTP differed significantly (P<0.01) between the groups ISS stage I, II, and III, and increased parallel with the progression of the disease. Twenty-eight (47.4%) patients were administered bortezomib-containing regimen as first-line therapy, which was consisted of BD (bortezomib + dexamethasone), VCD (bortezomib + cyclophosphamide + dexamethasone), and VMP (bortezomib + melphalan + prednisolone). The remaining 31 (52.5%) patients were administered without proteasome inhibitors as first-line therapy. Nineteen patients (32.2%) achieved at least very good partial response after first-line therapy and 9 (15%) patients fractured after start of first-line therapy.

Median OS for the entire cohort was 1874 days. In the Kaplan-Meier survival analysis, high sICTP (above upper limit: 6.0 mg/l) significantly associated with worse 2-year OS (63% versus 96%, P=0.02) and worse 2-year FFS (51% versus 86%, P=0.04). Serum ICTP may be a useful marker to predict survival and future bone fracture in our cohort, and these results are consistent with previous reports. Interestingly, in the patients firstly treated with bortezomib-containing regimen, the level of sICTP had no effect on 2-year FFS (90% with high sICTP versus 100% with low sICTP, P=0.53) and 2-year OS (95% with high sICTP versus 100% with low sICTP, P=1).

Conclusion

In general, high sICTP is considered to be a poor prognostic factor in MM patients, and similar results were also demonstrated in our cohort. Importantly, our data suggest that bortezomib may overcome poor prognosis conferred by high sICTP in plasma cell disorder patients. Further studies based on more cases are warranted to elucidate the efficacy of bortezomib in high sICTP patients. In addition, further studies on other proteasome inhibitors, such as carfilzomib or ixazomib are also needed.