A total number of 85 out of 207 newly diagnosed WM patients was successfully karyotyped by chromosome banding between 2000 and 2023. The median follow-up period for the entire cohort was 51 (19–81) months.
The cohort of patients that was studied comprised 64 (75.3%) out of the initial 85, due to the loss of 13 patients during follow up, lack of data in 6 cases, and the exclusion of other 2 patients because of cytogenetics being performed after the diagnosis (Table 1). In terms of CBA, 30 out of 64 patients (46.9%) showed an abnormal karyotype with a single chromosome change in 17/30 (56.6%) cases, two abnormalities in 7/30 (23.3%) patients and a CK in 6/30 (20%) patients. Only 2 patients exhibited a karyotype with more than 5 clonal chromosomal aberrations (high-CK). Considering the type of aberrations, structural abnormalities were detected in 13/30 (43.3%) of cases followed by numerical changes in 11/30 (36.6%). Both structural and numerical aberrations were found in a minority of cases, specifically in 6 of 30 (20.0%).
In line with other previously published studies, the most frequent aberration was the deletion of the long arm of chromosome 6 (6q-) in 7/30 (23.3%) patients, followed by the trisomy of the chromosome 3 (+ 3) in 7/30 (23.3%) patients and the deletion of long arm of the chromosome 11 (11q-) detected in 4/30 (13.3%) cases. The loss of Y chromosome (-Y) similarly to the trisomy of the chromosome 18 (+ 18) and to the trisomy of the chromosome 12 (+ 12) was described in 4/30 (13.3%) patients for each reported aberration. (Table 2).
Table 1
Baseline characteristics of WM patients with normal and abnormal karyotype
|
Normal karyotype
n = 34
|
Abnormal karyotype
n = 30
|
P value
|
Age, years, median (IQR)
|
65 (58–70)
|
72 (66–82)
|
0.003
|
CIRS > 6, n (%)
|
15/27 (0.56)
|
16/28 (0.57)
|
1.00
|
ECOG PS ≥ 2, n (%)
|
5/28 (0.18)
|
2/26 (0.08)
|
0.42
|
Hb ≤ 115 g/L, n (%)
|
13/34 (0.38)
|
10/30 (0.30)
|
0.68
|
PLTs ≤ 100 x 109/L, n (%)
|
4/34 (0.12)
|
0/30 (0.00)
|
0.11
|
β2-microglobulin > 3 mg/L, n (%)
|
14/19 (0.74)
|
10/13 (0.77)
|
0.84
|
MC IgM, g/L, median (IQR)
|
12.00 (6.90-20.39)
|
14.65 (8.51–25.75)
|
0.24
|
CRP, mg/L, median (IQR)
|
4.80 (2.90–35.00)
|
5.37 (2.90–10.00)
|
0.80
|
BM infiltration, %, median (IQR)
|
55 (19–76)
|
77 (65–98)
|
0.79
|
Creatinine, micromol/L, median (IQR)
|
75 (63–88)
|
77 (65–98)
|
0.79
|
MYD88L265P, n (%)
|
26/31 (0.84)
|
24/27 (0.89)
|
0.58
|
CXCR4 mut, n (%)
|
5/17 (0.29)
|
2/15 (0.13)
|
0.40
|
IPSSWM
Low, n (%)
Intermediate, n (%)
High, n (%)
|
14/34 (0.42)
10/34 (0.29)
10/34 (0.29)
|
6/30 (0.20)
11/30 (0.37)
13/30 (0.43)
|
0.07
|
Second cancer, n (%)
|
3/34 (0.88)
|
10/30 (0.30)
|
0.03
|
1st line treatment, n (%)
|
26/34 (0.76)
|
18/30 (0.60)
|
0.15
|
Major response rate, n (%)
|
16/26 (0.62)
|
7/18 (0.39)
|
0.13
|
2nd or more treatment lines, n (%)
|
8/34 (0.24)
|
9/30 (0.30)
|
0.56
|
BM: Bone marrow; CIRS: Cumulative Illness Rating Scale; CRP: C-reactive protein ECOG-PS: Eastern Cooperative Oncology Group Performance Status; Hb: Hemoglobin; IPSSWM: International Prognostic Scoring System on Waldenström Macroglobulinemia; IQR: Interquartile range; MC: Monoclonal Component
In the abnormal karyotype subgroup, we observed a higher prevalence of secondary cancers (30.00% vs 8.82%, p = 0.03) and a trend towards a higher IPSSWM score (43.00% vs 29.00%, p = 0.07).
When comparing WM patients with and without cytogenetic abnormalities, no significant correlation was observed between the presence of cytogenetic abnormalities and disease burden, renal impairment, inflammatory phenotype, comorbidity scores, and molecular features. However, we found that WM patients with at least an abnormal clone were older at diagnosis (median age 72 years vs 65 years, p = 0.003). (Table 1)
Moreover, advanced age was also found to correlate with the number of abnormalities since WM patients with CK had a median age significantly higher than that of the subject with 2 or less cytogenetic aberrations (85 vs 66 years, respectively, p < 0.001). Similarly, patients with 2 or more cytogenetic aberrations were older than patients with 0 or 1 alterations (median age 80 vs 66 years, respectively, p < 0.001). (Table 3).
Among patients with a normal karyotype, 26 out of 34 (76%) required treatment whereas among those with an altered karyotype 18 out of 30 (60%) needed therapy. The criteria for initiating first-line therapy were evenly distributed between the two groups. Anemia, hyperviscosity, and neuropathy were the most prevalent causes in our population (Table 1).
The number of subsequent lines of therapy administered after the first one was also similar between the two groups. Conventional chemoimmunotherapy was the most frequent type of treatment administered. Bruton Tyrosine Kinase (BTK) inhibitors were used at similar frequencies in the two groups and major response after the first line of therapy was achieved in 4 out of 5 cases.
Major response rate to first line therapy tended to be higher in the normal karyotype subgroup although statistical significance was not reached (62% vs 39%, p = 0.13). No substantial differences were seen in disease progression rate after first line therapy (20% vs 23.5%) during the entire follow up period. The percentage of death events was superior in patients with abnormal cytogenetics when compared to those with a normal karyotype (8/30 [27%] and 4/34 [12%], respectively). Of the patients for whom the cause of death was well-established two died due to secondary cancers in abnormal karyotype subgroup, while in the other subgroup three patients died due to sepsis and one due to lymphoma transformation.
Table 2
Summary of cytogenetic analysis
Cytogenetic feature
|
Frequency (%)
|
Karyotype
|
Abnormal
|
30/64 (46.9%)
|
Normal
|
34/60 (56.6%)
|
Number of aberrations in the karyotype
|
1
|
17/30 (56.6%)
|
2
|
7/30 (23.3%)
|
≥ 3 (complex and high-complex)
|
6/30 (20.0%)
|
Type of aberrations in the karyotype
|
Numerical only
|
11/30 (36.6%)
|
Structural only
|
13/30 (43.3%)
|
Numerical and structural
|
6/30 (20.0%)
|
Recurrent aberrations in the karyotype (in more than 3 cases)
|
Deletion 6q
|
7/30 (23.3%)
|
Trisomy 3/partial + 3
|
7/30 (23.3%)
|
Deletion 11q
|
4/30 (13.3%)
|
Trisomy 12/partial + 12
|
4/30 (13.3%)
|
Trisomy 18
|
4/30 (13.3%)
|
Loss of Y
|
4/30 (13.3%)
|
Table 3
Median age at diagnosis according to the karyotype
Subgroups
|
Median age at diagnosis, years (IQR)
|
P value
|
Abnormal karyotype
|
72 (66–82)
|
0.003
|
Normal karyotype
|
65 (58–70)
|
≥ 2 cytogenetic aberrations
|
80 (72–84)
|
< 0.001
|
< 2 cytogenetic aberrations
|
66 (59–72)
|
Complex karyotype
|
85 (83–87)
|
< 0.001
|
No complex karyotype
|
66 (59–73)
|
IQR = interquartile range |
When performing survival analyses, we found that WM patients with cytogenetic aberrations displayed inferior median overall survival (mOS) compared to those with a normal karyotype (76.1 vs 167.7 months, respectively [p value = 0.01]) and similar trend were noted for the median progression free survival (mPFS) in the two subgroups with (65.8 vs 117.8 months, respectively [p value = 0.01]). (Fig. 1A and 1B). Furthermore, the PFS curves diverged even more after 40 months. Additionally, no clinical and biochemical features related to WM disease were distributed differently between the groups beyond this time point.
WM patients with ≥ 2 chromosome changes exhibited an inferior mOS compared to those with 1 or 0 abnormalities (52.3 vs 167.7 months, respectively [p value = 0.02]) and a trend towards an inferior mPFS was also observed (52.3 vs 108.9 months, respectively [p value = 0.06]). The same held true for cases with or without CK. In fact, the CK subgroup exhibited significantly shorter mOS (52.3 vs 167.7 months respectively [p value = 0.004]) and mPFS (38.6 vs 108.9 months, respectively [p value < 0.001]). (Table 4).
As mentioned above, the described difference in terms of survival outcomes was maintained even with the increase of the number of aberrations (Fig. 1C, 1D, 1E, 1F). A univariate Cox proportional hazard regression analysis was conducted, examining various features. None of the considered variables (disease burden, renal impairment, inflammatory phenotype, comorbidity scores, and molecular features) were found to have a significant correlation with the observed differences in survival outcomes, thus suggesting an independent role of cytogenetic abnormalities in determining inferior outcomes in WM patients.
Table 4
Overall and progression free survival outcomes according to the karyotype
Subgroups
|
Median OS (months)
|
HR (CI 95%)
|
P value
|
Median PFS
(months)
|
HR (CI 95%)
|
P value
|
Normal karyotype
|
76.1
|
4.35 (1.27–14.86)
|
0.01
|
65.8
|
2.90 (1.24–6.83)
|
0.01
|
Abnormal karyotype
|
167.7
|
117.8
|
≥ 2 cytogenetic aberrations
|
52.3
|
5.28 (1.15–24.31)
|
0.02
|
52.3
|
2.69 (0.92–7.81)
|
0.06
|
< 2 cytogenetic aberrations
|
167.7
|
108.9
|
Complex karyotype
|
52.3
|
9.14 (1.56–26.11)
|
0.004
|
38.6
|
6.05 (1.85–19.79)
|
< 0.001
|
No complex karyotype
|
167.7
|
108.9
|
HR = Hazard Ratio; CI 95% = 95% confidence interval; OS = Overall Survival; PFS = Progression Free Survival