Cytogenetic profile and risk of transformation to acute myeloid leukemia (AML) in Indonesian patients with myelodysplastic syndrome (MDS): a pilot study

Introduction

Myelodysplastic syndrome (MDS) is a heterogeneous group of myeloid clonal disorders caused by ineffective hematopoiesis or failure of blood cell maturation, resulting in peripheral blood cytopenia and bone marrow failure.¹ Patients with MDS have increased susceptibility to acute myeloid leukemia (AML).² Most MDS cases are de novo or primary, while the remaining 10% are secondary, resulting from prior exposure to radiotherapy or chemotherapy for cancer.³

The reported incidence rate of MDS in the general population is 4.5 per 100,000 people per year, with a higher incidence in men than in women (6.2 vs. 3.3 per 100,000 people per year).⁴ In the United States alone, more than 10.000 new cases are reported annually. Studies have consistently shown that MDS is more commonly diagnosed in patients with advanced age.⁵ More than 80% of patients with MDS were first diagnosed at the age of 60 years, with a median age of 76 years, and only 6% of patients had disease onset under 50 years of age.^6,7 Based on the Surveillance, Epidemiology, and End Results (SEER) Medicare database, the incidence of MDS is as high as 75 per 100,000 persons in the population older than 65.⁸ The incidence of MDS is expected to continue to increase because of the higher incidence of secondary MDS, improved awareness of the disease in the general population and clinicians, and more advanced clinical workups. MDS was more frequent in men than women.⁵ In Asian countries, the incidence of MDS was reported to be 2- to 4-fold lower, and the age of onset was ten years younger than that in Western countries.⁹

MDS is considered a preleukemic condition, in which 30% of patients progress to AML.¹⁰ Age 65 years old and younger, bone marrow blast count >5%, and transfusion dependence were associated with AML transformation.¹¹ Narayanan et al. reported that AML transformation occurred in 10% of MDS patients within six months.¹² The pathophysiology of MDS and its progression to AML involves cytogenetic, genetic, and epigenetic factors.¹³

Cytogenetics plays a vital role in the disease course and management and serves as a diagnostic and prognostic indicator in MDS.¹⁴ Chromosomal karyotype is included in the Revised International Prognostic Scoring System (IPSS-R) as a fundamental factor for predicting the clinical progression of the disease and guiding the management plan.¹⁵ Through the IPSS-R risk group, a clinician can differentiate patients with higher risk, with the treatment goals of delaying AML transformation and improving overall survival.¹⁶ The current standard of management for high-risk patients includes hypomethylating agents, decitabine, azacitidine, and allogeneic stem cell transplants.¹⁷

Cytogenetic abnormalities were abnormal in >50% of the patients at diagnosis.¹⁸ Amplifications, deletions, and translocations were cytogenetic abnormalities found in 50% of primary MDS patients and 80% of secondary MDS patients.¹⁹

Currently, there are no published data regarding the cytogenetic profiles of MDS patients in Indonesia. This study aimed to provide a descriptive overview of patients’ demographic and cytogenetic profiles from the National Cancer Center in Indonesia.

Methods

Results

A total of 28 patients with MDS were included in this study, with a mean age of 66±12 years old.⁴¹ We found that nine patients (32.1%) were below 65 years of age, with the youngest being 25 and the oldest being 85. The majority of the participants were male (n=17; 60.7%), and the sex ratio between men and women was 1.54. Six of the nine patients (66.7%) younger than 65 years of age were male. Two (7.14%) patients were aged < 50 years. The most prevalent MDS type in this study population was MDS-MLD (n=14/28; 50.0%), followed by MDS-SLD (n=7/28; 25.0%) and MDS-EB1 (n=5/28; 17.9%). The flow chart of the study population and additional demographic details are shown in Figure 1 and Table 1 respectively.

Figure 1. Flow chart of study population.

Cytogenetic analysis revealed metaphase in only 14 (50.0%) patients. Due to insufficient metaphase in the sample, cytogenetic grouping could only be done in nine patients (32.1%) (Table 2). There were 4 patients in the intermediate, 3 in the poor, and 2 in the very poor cytogenetic groups. Based on the IPSS-R category, five patients (17.8%) were at high risk, and three patients (10.7%) were categorized as very high risk, while the remaining 20 patients (71.4%) could not be categorized due to the absence of metaphase during cytogenetic analysis.

The cytogenetic profile showed monosomy 7 in six patients. However, it was only found in one metaphase in each patient, so it could not be interpreted as a clonal mutation. Deletion of chromosome 5 (del(5)(q31)), del (16)(q21.1), and del (16)(q11.2) was found in a male patient with MDS-EB1, considered a very poor cytogenetic group, who had AML transformation three months after the diagnosis. The patient died one month after the transformation to AML. In total, three patients developed AML during follow-up.

The 1-year overall survival rate in this study was 64.3%, with 10 of 28 patients deceased. The causes of death were AML (n=3; 30%), COVID-19 (n=3; 30%), bacterial pneumonia (n=2; 20%), cerebrovascular disease (n=1; 10%), and complications of diabetes mellitus (n=1;10%). In the deceased group, the median age of the patients was 69 (55-85) years, with a female-to-male ratio of 1 to 2.6, and the majority of them were MDS-EB1 (40%). The cytogenetic group, which was successfully identified in 9 patients, ranged from high to very high risk. In the surviving group, the median age of the patients was 69 (25-82) years, the female-to-male ratio was 1 to 1.125, and the majority of subjects had MDS-MLD (50.0%). Unfortunately, only three cytogenetic profiles were identified in this group, which indicated a high risk.

Discussion

In this study, more than half of the patients with MDS were male. This finding was in accordance with the epidemiology of MDS in the general population, which showed a global predominance in males globally.^22,23 The sex ratio within our study is within the reported range, which is 1.24-2.125.⁹

We found that almost one-third of our study population was diagnosed under 65 years of age, younger than the general population of MDS patients. Based on the Dutch registry, the median age of the patients with MDS at the first diagnosis was 74.²⁴ In Europe, the reported median age at diagnosis is 76 years.⁶ It has been highlighted that there was a difference in median age between Asian and Western countries, as reported by studies from China and Japan, ranging from 62 to 76 years old.^25,26 The difference in age of onset between Asian and Western countries might be explained by differences in environmental exposure. Genetic factors may also have a significant effect. Less than 10% of the patients were diagnosed under 50 years of age, which was in accordance with a prior study.²⁷

Our data show that the MDS-MLD subtype has the highest frequency among other subtypes, constituting half of the study population. This finding is in accordance with a previous study showing that MDS-MLD was a subtype more represented in Asia, including Japan and China, with 43% and 41.2% of cases, respectively. In contrast, MDS unclassifiable (MDS-U) was ranked as the most prevalent type in Western countries, while the MDS-MLD had a much lower percentage (approximately 7.35%).⁹ Both Japanese and Chinese studies have reported that MDS-EB is the second most prevalent type of EB.^28–30 However, this was not the case in our study population, in which MDS-SLD was the second most common, followed by MDS-EB-1.

We found that most MDS patients in our study sample had high and very high risks. This finding supports the notion that Asian patients have a higher risk of developing high-risk MDS. Two studies reported a higher frequency of intermediate risk and greater risk in Japanese patients than in more prevalent low-risk patients in Germany and Caucasians.^30,31 Jiang et al. also confirmed a similar finding, compiling some Asian and Western studies. The study found that more Asian MDS patients had intermediate-, high-, and very high-risk, while in Western countries, very low- and low-risk patients had a higher distribution. The higher proportion of high-risk cytogenetic abnormalities in Asian patients might explain this finding.⁹

This study identified one subject with del(5q) and classified it as the MDS-MLD subtype. Del(5q) cytogenetics was associated with a good prognosis and was found to be twice as frequent in Asian patients, with a 4.63% prevalence than in Western countries (8.81%). The most common chromosomal abnormality in MDS is the deletion of the long arm of chromosome 5 (5q), which is found in up to 15% of diagnosed cases.^32,33 del(5q) is more prevalent in Western patients with MDS than in Asian patients. Patients with isolated del(5q) are known to be lenalidomide-responsive, which results in a better prognosis. Anomaly of chromosome 7, either monosomy or deletion of 7q, is reported in approximately 10% of de novo MDS cases and up to 50% of therapy-related MDS cases. Monosomy 7 is correlated with worse prognosis and decreased overall survival in patients with MDS. In addition, there are hundreds of variants of cytogenetic abnormalities that have rarely been reported in MDS patients, such as -X, 3q abnormalities, +13/del(13q), i(17q), +21/-21. In a German study, rare chromosomal abnormalities occurred in less than 2% of patients with MDS. Additionally, we found del(20q) in one patient, although it was not a clonal mutation. Del(20q) is more prevalent in Asian patients than in Western patients, along with trisomy 8.

The underlying cytogenetic discrepancy between Asian and Western countries remains unknown, but it is thought to explain the severity of MDS in Asian patients. Although the incidence of MDS is lower in Asia, very high-risk, high-, and intermediate-risk groups, based on IPSS-R scores, are more prevalent than in Western countries, which reported more MDS patients in very low- and low-risk groups. The MDS-RS, MDS-del(5q), and MDS-U subtypes are more common in Western countries. In contrast, MDS-SLD, MDS-MLD, and MDS-EB are more common in Asian countries.

Several comorbidities have been found to influence disease risk factors, such as congestive heart failure and chronic obstructive pulmonary disease, which are associated with shorter survival. Disease prognosis varies, ranging from indolent to progressive disease.³⁴ The median overall survival in patients with MDS is only 5 years, which is considered to have a poor prognosis.

On average, 30% of patients with MDS develop transformation to AML during the course of the disease. In this study, the rate of AML transformation was 10.7% in one year. This finding is lower than that reported by Vamsi et al., who reported that AML transformation during a 1-year follow-up was 26.9% in higher-risk MDS patients, which were patients with intermediate IPSS-R prognostic risk or greater.¹⁶ Another study with eight years of follow-up reported AML transformation in 13.9% of MDS patients, with a median of 5 (1-23) months.³⁵ It has been reported that approximately 10-35% of MDS cases evolve into acute leukemia during the disease course. The IPSS-R scoring system was used to estimate the risk of AML transformation five years after diagnosis.

Based on the survival outcome, the overall survival rate in this study population was 64.3%; compared with other studies, the overall 3-year survival rate was 32%.³⁶ Regarding MDS type, MDS-EB1 was reported as the most prevalent diagnosis in the ceased group. This finding supports previous studies reporting that MDS-EB has the worst prognosis among the other types, with a higher risk of AML transformation and shorter median survival, with 16 and 9 months for MDS-EB and MDS-EB2, respectively.³⁷

To the best of our knowledge, this is the first cytogenetic profiling study conducted in Indonesia. In MDS patients, metaphase cytogenetics is used to identify chromosomal abnormalities in approximately 50% of patients.³² However, a limitation of our study is that most of the cytogenic samples had no metaphase, and the cytogenetic profile could only be found in suboptimal amounts (<10 metaphases) of patients (28.57%). It is recommended that when an abnormal result is obtained at diagnosis, at least 20 metaphases should be analyzed.³⁸ Lower metaphase is related to a higher chance of missing small clones.³⁹ Another issue is that we did not identify somatic mutations in the patients and thus could not evaluate the role of somatic mutations.

Considering that karyotyping in MDS therapeutic plans and prognosis has a significant influence, further evaluation is needed throughout the cytogenetic analysis process, from transportation and processing of samples, in which errors could occur at any point. A study from India reported that half of the culture failures occurred in samples processed for 24 hours and above. Technical errors include aged samples, low and high cell counts, the volume of the sample, and the culture technique.⁴⁰ It should also be noted that cytogenetic testing is not routinely performed in Indonesia.

Conclusion

MDS is heterogeneous in clinical manifestation and molecular etiology, with AML transformation as one of the final endpoints in the clinical course. Our study observed that MDS-EB was the subtype with the highest risk of AML transformation. Further studies with a larger sample size and modern cytogenetic methods, such as conventional FISH and spectral karyotyping, should be conducted to confirm the findings of this study.