Cohort Analysis of FISH Testing of CD138+ Cells in Relapsed Multiple Myeloma: Implications for Prognosis and Choice of Therapy
Authors: Smith Dean , Stephenson Clemency , Lach Anna , Chatters Steve , Kempski Helena , Yong Kwee L 
Published: October 2019

Abstract
Introduction:
Interphase FISH on CD138-selected bone marrow cells enables genetic risk stratification in newly diagnosed multiple myeloma (MM), however as MM remains incurable, most centres still treat newly diagnosed MM uniformly, utilising the most active regimens available. At relapse an increasing choice of regimens, coupled with co-morbidities and treatment-emergent toxicities, means no uniform approach is possible. Instead, therapy is tailored to disease and patient related risk factors. In this setting, FISH testing may be particularly useful if not done at diagnosis and to identify progression events that may alter prognosis.
Aim:
To evaluate the outcome of FISH analysis in consecutive patients with relapsed MM undertaken at our centre: success rate, frequency of abnormalities, incidence of progression events and correlation of FISH abnormalities with treatment outcomes.
Methods:
FISH analysis was performed on 192 samples from 154 relapsed patients (2012-13). Plasma cells were selected using magnetic CD138 MicroBeads and interphase FISH carried out using probes as recommended by the EMN (Ross et al, 2012). If patients had no prior results, a full FISH MM panel was performed, using probes for t(4;14), t(14;16), t(11;14), deletion 17p (17p-), Chr 1 abnormalities (1p-/1q+) and deletion 13q (13q-). If patients had been previously tested for an IgH translocation (Tx), a progression event panel was used: 1p-/1q+, 17p- and 13q-. Patients underwent FISH testing prior to starting the next line of therapy.
Results:
79% of samples were successfully analysed, with analysis limited in 16% and failed in 5%. Common reasons for failure were poor quality/aged slides, insufficient material and poor hybridisation. 17% of patients had no cytogenetic abnormality. The most common abnormality was 13q- (43.1%), followed by 1q+ (41.4%), t(11;14) (18.3%), t(4;14) (12.4%), 17p- (12.0%) 1p- (8.9%), and t(14;16) (5.6%)
Progression events were more common in t(14;16) and t(4;14) groups. All patients with t(14;16) and 82% with t(4;14) had an additional genetic lesion. Only 21% of patients with t(11;14) and 54% with no IgH Tx had an additional event. 80 patients (51.3%) had prior FISH results and 13 (16.3%) had developed a new abnormality on the later test. In 9 cases the progression event was 17p-, in 2 it was 1q+ and 2 cases developed 17p- and 1q+. The patients developing 1q+ were previously standard risk, so repeat testing altered risk group. Acquisition of 17p- indicates especially poor outcome, thus in all 13 cases repeat FISH analysis altered risk. Among patients with progression events none harboured t(11;14), 8 (64%) had no IgH Tx, 3 had t(14;16) and 2 had t(4;14).
FISH results were correlated with clinical outcome. Patients were stratified as having high risk genetics [t(4;14), t(14,16), 17p- in ≥50% cells, 1p-/1q+] or standard risk [t(11;14), normal cytogenetics]. 63 (41%) patients were high risk, 83 (54%) standard risk, with no information available for 8 (5%). Both groups had received a median of 2 prior lines of therapy. Response rates (≥PR) to the next line of therapy were similar (60.4% standard risk vs 56.0% high risk). PFS from time of FISH was significantly longer in the standard risk group (9.8 months vs 5.9, p<0.01) as was OS (not reached vs 17.1 months, p<0.01, Fig. 1). In the high risk group, PFS was significantly longer in patients receiving a proteasome inhibitor (PI) as the next line of treatment versus those receiving other therapies (9.6 months vs 4.6, p=0.01) as was OS (not reached vs 9.7 months, p<0.01, Fig. 2). In the standard risk group, PFS was similar if patients received PI or not (9.5 months PI vs 9.8 other) as was OS (not reached both groups, Fig. 2).
Conclusions:
FISH analysis on MM patients at relapse was achievable. 74/154 patients had no prior results and a further 13 developed new poor prognostic markers, thus FISH at relapse provided new information in 56% of patients. Progression events were more common in patients harbouring t(4;14) or t(14;16). FISH at relapse was prognostic with high risk abnormalities associated with significantly shorter PFS and OS. The use of PI appeared to abrogate this poor prognosis, suggesting FISH at relapse could be a predictive and prognostic marker. Given the availability of second generation PI and the option of bortezomib re-treatment, results of FISH testing at relapse could directly influence clinical practice.
Figure 1 Figure 1.
Figure 2 Figure 2.

Disclosures
No relevant conflicts of interest to declare.