The characteristics of CALR mutations in myeloproliferative neoplasms: a clinical experience from a tertiary care center in Qatar and a literature review

Figures & data

Table 1. Baseline characteristics of patients with CALR mutation in myeloproliferative neoplasm

Characteristic	CALR Mutated MPN Patients (N = 50), n (%)
Male Gender	38 (76%)
Age At Diagnosis
<40 years	16 (32%)
40–60 years	24 (48%)
>60 years	10 (20%)
Weight (kg, mean)	77.5
Height (cm, mean)	169.9
Ethnicity
Asian	15 (30%)
Black/African	6 (12%)
White	2 (4%)
Arabs	27 (54%)
Comorbid Medical Conditions
Diabetes mellitus	9 (18%)
Hypertension	18 (36%)
Obesity	11 (22%)
Cigarette Smoking	5 (10%)
Baseline Blood Works Results
Hemoglobin (Median, IQR)	13.05 (11.7-14.28)
WBCs (Median, IQR)	8.20 (5.98-10.30)
Platelets (Median, IQR)	850.00 (525.25-1120.25)
LDH (Median, IQR)	214.00 (177.00-317.00)
Molecular Tests
CALR type 1	24 (48%)
CALR type 2	21 (42%)
Other CALR	5 (10%)
JAK2 (with other CALR)	1 (2%)
MPL (with CALR type 1)	1 (2%)
Diagnosis
preMF	9 (18%)
ET	31 (62%)
PMF	10 (20%)
Treatment
Hydroxyurea	22 (44%)
JAK2 inhibitors	6 (12%)
Anagrelide	1 (2%)
Antiplatelet (Aspirin or Clopidogrel)	36 (72%)
Progression
MF (carrying CALR 1 mutations)	4 (8%)
AML (carrying CALR 2 mutations)	1 (2%)
ALL	0
CML	0
Complications
VTE	3 (6%)
Stroke	2 (4%)
Cardiac ischemic events	4 (8%)
Abdominal veins thrombosis	3 (6%)
Hemorrhage	1 (2%)
Secondary malignancy (carrying CALR type 1 mutations)	3 (6%)
Mortality (carrying CALR type 2 mutation)	1 (2%)

CALR: Calreticulin; MPN: Myeloproliferative Neoplasm; kg: Kilogram; cm: Centimeter; IQR: Interquartile Range; WBC: White Blood Cell; LDH: Lactate Dehydrogenase; JAK2: Janus kinase 2; MPL: Myeloproliferative Leukemia virus oncogene; pre-MF: Prefibrotic Myelofibrosis; ET: Essential Thrombocytopenia; P/MF: Primary/Myelofibrosis; AML: Acute Myeloid Leukemia; ALL: Acute Lymphocytic Leukemia; CML: Chronic Myeloid Leukemia; VTE: Venous Thromboembolism

Table 2. Association between Different CALR Mutations and Baseline Characteristics of Patients.

Characteristics	CALR Mutations			P Value
	Type 1 (n = 24), n (%)	Type 2 (n = 21), n (%)	Other (n = 5), n (%)
Male Gender	19 (79.2)	14 (66.7)	4 (80.0)	0.602
Age Group
Below 40	5 (20.8)	9 (42.8)	2 (40.0)	0.396
40–60	10 (41.6)	12 (50.0)	2 (40.0)	0.884
Above 60	7 (29.2)	2 (9.5)	1 (20.0)	0.259
Arab Ethnicity	12 (50.0)	14 (66.7)	1 (20.0)	0.082
Comorbid Medical Conditions
Diabetes mellitus	3 (12.5)	5 (23.8)	1 (20.0)	0.611
Hypertension	11 (45.8)	7 (33.3)	0 (0)	0.143
Obesity	2 (8.3)	7 (33.3)	2 (40.0)	0.077
Cigarette Smoking	4 (16.7)	1 (4.8)	0 (0)	0.304
Baseline Blood Works Results
Hemoglobin (Median, IQR)	11.8 (2.7)	13.4 (3.2)	13.95 (1.6)	0.323
WBCs (Median, IQR)	6.45 (2.8)	8.3 (5.2)	7.0 (3.6)	0.557
Platelets (Median, IQR)	713.0 (363.0)	874.0 (673.0)	1062.5 (738)	0.673
LDH (Median, IQR)	207.5 (281.0)	221.0 (80.0)	180.5 (232.0)	0.464
Molecular Tests
JAK2	0 (0)	0 (0)	1 (20.0)	0.010
MPL	1 (4.2)	0 (0)	0 (0)	0.575
Diagnosis
preMF	3 (12.5)	4 (19.1)	2 (40.0)	0.501
ET	16 (66.7)	12 (57.1)	3 (60.0)	0.928
PMF	5 (20.8)	5 (23.8)	0 (0)	0.484
Treatment
Hydroxyurea	8 (33.3)	11 (52.4)	3 (60.0)	0.329
JAK2 inhibitors	3 (12.5)	3 (14.3)	0 (0)	0.673
Anagrelide	1 (4.2)	0 (0)	0 (0)	0.575
Aspirin	14 (58.3)	15 (71.4)	3 (60.0)	0.844
Clopidogrel	2 (8.3)	0 (0)	2 (40.0)	0.012
Progression
MF	4 (16.7)	0 (0)	0 (0)	0.095
AML	0 (0)	1 (4.8)	0 (0)	0.494
ALL	-	-	-	N/A
CML	-	-	-	N/A
Complications
VTE	1 (4.2)	2 (9.5)	0 (0)	0.630
Stroke	0 (0)	2 (9.5)	0 (0)	0.237
Cardiac ischemic events	1 (4.2)	1 (4.8)	2 (40.0)	0.021
Abdominal veins thrombosis	2 (8.4)	0 (0)	1 (20.0)	0.078
Hemorrhage	1 (4.2)	0 (0)	0 (0)	0.575
Secondary malignancy	3 (12.5)	0 (0)	0 (0)	0.750
Mortality	0 (0)	1 (4.8)	0 (0)	0.494

Chi-square analysis and Kruskal-Wallis test were applied at alpha = 0.05. CALR: Calreticulin; IQR: Interquartile Range; WBC: White Blood Cell; LDH: Lactate Dehydrogenase; JAK2: Janus kinase 2; MPL: Myeloproliferative Leukemia virus oncogene; pre-MF: Prefibrotic Myelofibrosis; ET: Essential Thrombocytopenia; P/MF: Primary/Myelofibrosis; AML: Acute Myeloid Leukemia; ALL: Acute Lymphocytic Leukemia; CML: Chronic Myeloid Leukemia; VTE: Venous Thromboembolism

Table 3. Summary of Major CALR Studies.

Study	Population Size	CALR Patients Demographics	CALR Prevalence	Clinical Phenotype	Thrombotic Complications	Hematologic Transformation	Survival and Follow-up Duration
Klampfl et al, 2013 [6]	311 ET & 203 MF	-	25% of ET and 35% of MF had CALR mutation. Among CALR mutations, type 1 and type 2 percentages were 53% and 31.7%, respectively.	ET with CALR mutation had ↓ Hgb, ↓ WBC, &↑ Plt at diagnosis than mutated JAK2. MF with CALR mutation had ↓ WBC, &↑ Plt then mutated JAK2.	ET with CALR mutation had a lower risk of thrombosis than mutated JAK2.	-	CALR mutation had a more prolonged overall survival than mutated JAK2.
Nangalia et al, 2013 [19]	151 ET & MF	-	CALR mutations were found in 70-84% of MPNs.	MPN with CALR mutation had ↑ Plt & ↓ Hgb than mutated JAK2.	-	ET with CALR mutation had a significantly higher incidence of transformation to MF than mutated JAK2.	There were no significant differences in rates of survival.
Rumi et al, 2013 [11]	717 ET	ET with CALR mutation patients were significantly younger and had more males compared to those with JAK2-mutated ET. CALR-1 patients were younger than CALR-2.	24.5% of ET had CALR mutation. Among CALR mutations, type 1, type2, and others percentages were 46%, 38%, and 16%, respectively.	ET with CALR mutation had ↓ Hgb, ↓ WBC, ↑ Plt, &↑ serum EPO, then mutated JAK2. CALR-1, compared to CALR-2, had ↓ Hgb, ↓ WBC, ↓ frequency of splenomegaly, & ↓ LDH, ↑Plt, ↑ serum EPO, & ↑ CD34 count.	ET with CALR mutation had a lower risk of thrombosis at diagnosis than mutated JAK2.	No significant difference in myelofibrotic transformation was noted, and no polycythemic transformation was observed in CALR-mutated. Patients.	CALR-mutated PMF, but not ET, had better overall survival than JAK2. The median follow-up period was 5.2 years (range 0–32 years)
Andrikovics et al, 2014 [9]	289 ET & 99 PMF	CALR-mutated patients were younger compared to those with JAK2-mutation	50% and 32% of MPN carried type 1 and type 2 CALR, respectively. 33% of ET and 25% of MF had CALR mutation.	CALR mutation had ↑ Plt than mutated JAK2.	ET with CALR mutation had a lower risk of venous thrombosis than mutated JAK2.	ET with CALR mutation had a higher risk of progression than mutated JAK2.	CALR-mutated PMF, but not ET, had better overall survival than JAK2.
Li et al., 2014 [13]	357 Chinese patients with PMF	CALR-mutated patients were younger compared to those with JAK2-mutation	21% of PMF had CALR mutation. 32% and 64% of CALR mutations were type-1 and type-2, respectively.	PMF with CALR type 2 mutation had ↓ Hgb, ↓ WBC, abnormal platelet levels (<100 × 109/L, or >450 x 109/L), & no splenomegaly compared to mutated JAK2.	-	-	Type 2 CALR-mutated, but not type 1, PMF had significantly shorter survival compared with JAK2 mutations. The median follow-up period was 28 months (range 1-385).
Rotunno et al, 2014 [14]	576 ET	CALR-mutated patients were preferentially males compared with JAK2 mutation.	15.5% of ET had CALR mutation	ET with CALR mutation had ↓ Hgb, ↓ WBC, & ↑ Plt than mutated JAK2.	ET with CALR mutation had a lower risk of thrombosis than mutated JAK2.	CALR mutation had no impact on transformation to post-ET Myelofibrosis	CALR mutation had no impact on survival. Median follow-up was 71.9 months (range, 2–257 months)
Gisslinger et al, 2014 [20]	115 ET & 85 pre-MF	-	18% of ET and 39% of pre-MF had CALR mutations	-	-	-	CALR-mutated pre-MF, but not ET, had better overall survival than JAK2. Such a striking difference was not seen at the time of transformation into overt Myelofibrosis.
Chen et al, 2014 [15]	147 ET	CALR-mutated patients were younger compared to those with JAK2-mutation	22.5% of ET had CALR mutations. 54.5%, 27.3%, and 6.1% of CALR mutations were type-1, type-2, and type-3, respectively.	ET with CALR mutation had ↓ WBC, & ↑ Plt then mutated JAK2.	ET with CALR mutation had a lower risk of thrombosis than mutated JAK2.	CALR-mutated patients had 3.3% post-ET MF Transformation.	CALR-mutated ET had a favorable impact on thrombosis-free survival (TFS) than JAK2.
Al Assaf et al, 2015 [16]	160 ET	CALR-mutated patients were younger compared to those with JAK2-mutation. CALR type 1 is strongly associated with male gender compared to the JAK2.	63.7% of double-negative and 56% of JAK-negative ET were CALR positive. 60.3% and 31% of double-negative ET CALR were type 1 and type 2, respectively. 34%, 17%, and 5% of JAK2-negative ET CALR were type-1, type-2, and other types, respectively.	ET with CALR mutation had ↓ Hgb, ↓ WBC, & ↑ Plt than mutated JAK2.	CALR mutation had no impact on thrombotic complications.	ET with CALR mutation had a higher risk of progression to MF than mutated JAK2.	CALR-mutated ET had better overall survival than JAK2, in particular patients of age 60 years or younger.
Pietra et al, 2016 [17]	908 ET & 374 PMF	CALR-mutated ET was younger compared to those with JAK2-mutation.	24% of ET and 26% of PMF had CALR mutation. 65%, 32%, and 3% of CALR mutations were type-1 like, type-2 like, and others, respectively.	CALR type 1-like mutations were mainly associated with a Myelofibrosis phenotype, while CALR type 2 was preferentially associated with the ET phenotype.	Despite higher platelet count, CALR type 2 mutation in ET had a lower risk of thrombosis than mutated JAK2 or type 1-like CALR mutation.	ET with type 1-like CALR mutations were mainly associated with a significantly higher risk of myelofibrotic transformation but no impact on leukemic transformation.	Type 1-like CALR-mutated PMF, but not ET, had better overall survival than JAK2. The median follow-up period was 4.7 years (range 0–31 years).
Kong et al, 2016 [22]	3,141 ET and 1,605 PMF (Meta-analysis)	-	19% of ET and 22% of PMF had CALR mutation.	-	-	ET with CALR mutations had a slight trend toward fibrotic transformation but no impact on leukemic transformation.	-
Tefferi et al, 2017 [18]	709 PMF	CALR type 1 is associated with male gender. Type 2 is associated with younger age.	16% and 3.4% of PMF carried CALR type 1-like and CALR type 2-like mutations, respectively.	PMF with CALR type 2-like mutation had ↓ Hgb, ↑ WBC, ↑ Plt, & ↑ circulating blasts than mutated JAK2.	-	CALR mutation did not impact the progression rate to Myelofibrosis or the risk of leukemic transformation. CALR mutations had the lowest red cell transfusion need.	CALR-mutated PMF, but not ET, had better overall survival than JAK2. The median follow-up period was 3.5 years.
Kim et al, 2022 [21]	510 ET & MF	-	6.2% of ET and 3.3% of PMF had CALR mutation. 49% and 51% of CALR mutations were type 1-like and type 2-like, respectively.	CALR type 1-like mutations were associated with a Myelofibrosis phenotype (↓ Hgb & ↓ Plt), while CALR type 2-like was associated with ET phenotype (↑ Plt & ↑ ANC).	Despite higher platelet counts, CALR type 2 mutation in ET had no thrombotic events.	-	-

CALR: Calreticulin; MPN: Myeloproliferative Neoplasm; ET: Essential Thrombocytopenia; P/MF: Primary Myelofibrosis; Hgb: Hemoglobin; WBC: White Blood Cell; Plt: Platelet; JAK2: Janus kinase 2; EPO: erythropoietin; pre-MF: Prefibrotic Myelofibrosis; ANC: Absolute Neutrophilic Count

Klampfl T, Gisslinger H, Harutyunyan AS, et al. Somatic mutations of Calreticulin in myeloproliferative neoplasms. N Engl J Med. 2013;369(25):2379–2390. doi:10.1056/NEJMoa1311347.

 PubMed Web of Science ®Google Scholar

Taher A, Yassin MA, Hou XZ, et al. Impact of myeloproliferative neoplasms (MPNs) on health-related quality of life (HRQOL) and medical resource utilization: results from the MERGE registry. Blood. 2018;132:4311, doi:10.1182/blood-2018-99-113248

 Web of Science ®Google Scholar

Tvorogov D, Thompson-Peach CA, Foßelteder J, et al. Targeting human CALR-mutated MPN progenitors with a neoepitope-directed monoclonal antibody. EMBO Rep. 2022;23(4). doi:10.15252/embr.202152904

 PubMed Web of Science ®Google Scholar

Andrikovics H, Krahling T, Balassa K, et al. Distinct clinical characteristics of myeloproliferative neoplasms with calreticulin mutations. Haematologica. 2014;99(7):1184.

 PubMed Web of Science ®Google Scholar

Li B, Xu J, Wang J, et al. Calreticulin mutations in Chinese with primary myelofibrosis. Haematologica. 2014;99(11):1697–1700. doi:10.3324/haematol.2014.109249

 PubMed Web of Science ®Google Scholar

Allahverdi N, Yassin M, Ibrahim M. Environmental factors, lifestyle risk factors, and host characteristics associated with Philadelphia negative myeloproliferative neoplasm: a systematic review. Cancer Control. 2021;28:107327482110468, doi:10.1177/10732748211046802

 Web of Science ®Google Scholar

Gisslinger H, Thiele J, Gisslinger B, et al. Calreticulin mutation status predicts improved disease outcome in prefibrotic primary myelofibrosis but not in WHO-defined essential thrombocythemia. Blood. 2014;124(21):3167, doi:10.1182/blood.V124.21.3167.3167

 Web of Science ®Google Scholar

Chen CC, Gau JP, Chou HJ, et al. Frequencies, clinical characteristics, and outcome of somatic CALR mutations in JAK2-unmutated essential thrombocythemia. Ann Hematol 2014;93(12):2029–2036. doi:10.1007/s00277-014-2151-8

 PubMed Web of Science ®Google Scholar

Al Assaf C, Van Obbergh F, Billiet J, et al. Analysis of phenotype and outcome in essential thrombocythemia with CALR or JAK2 mutations. Haematologica. 2015;100(7):893–897. doi:10.3324/haematol.2014.118299

 PubMed Web of Science ®Google Scholar

Pietra D, Rumi E, Ferretti VV, et al. Differential clinical effects of different mutation subtypes in CALR-mutant myeloproliferative neoplasms. Leukemia. 2016;30(2):431–438. doi:10.1038/leu.2015.277

 PubMed Web of Science ®Google Scholar

Kong H, Liu Y, Luo S, et al. Frequency of calreticulin (CALR) mutation and Its clinical prognostic significance in essential thrombocythemia and primary myelofibrosis: a meta-analysis. Internal Medicine (Tokyo, Japan). 2016;55:1977–1984. doi:10.2169/internalmedicine.55.6214

 PubMed Web of Science ®Google Scholar

Tefferi A, Wassie EA, Guglielmelli P, et al. Type 1 versus Type 2 calreticulin mutations in essential thrombocythemia: a collaborative study of 1027 patients. Am J Hematol 2014;89(8):E121–E124. doi:10.1002/ajh.23743

 PubMed Web of Science ®Google Scholar

Kim HY, Han Y, Jang JH, et al. Effects of CALR-mutant type and burden on the phenotype of myeloproliferative neoplasms. Diagnostics (Basel, Switzerland). 2022;12(11):2570, doi:10.3390/diagnostics12112570

 PubMedGoogle Scholar

Data availability statement

All data generated or analyzed during this study are included in this article. Further enquiries can be directed to the corresponding author.