Studies on the Quantification of Mutation Resistance to Specific Drug Therapy in Chronic Myeloid Leukemia patients

 

Ankit Darji1*, Praful Bharadia2

1Hemchandracharya North Gujarat University, Patan.

2L.M. College of Pharmacy, Ahmedabad.

*Corresponding Author E-mail: ankitdarji1627@gmail.com

 

ABSTRACT:

Imatinib is a type of protein tyrosine kinase inhibitor which inhibits the constitutive abnormal tyrosine kinase created by the Philadelphia chromosome i.e. the BCR-ABL tyrosine kinase, abnormality in CML patient. The aim of the study is to assess the response of imatinib in CML patients and to observe resistance to imatinib. Study was performed at Ahmedabad, Gujarat, India. Dose of 400, 600, 800 mg of Imatinib was found to be prescribed to all patients during the study. Comparison of laboratory parameters and PCR data were done after measurement by RT-PCR method. Total 256 patients with CML were enrolled in the study. 196 patients had completed study as per protocol. 38 patients were newly diagnosed whereas 158 patients were already diagnosed with CML. 89.29% (n = 175) of patients achieved complete haematological response, Complete MolR were achieved in n = 41 at 6th months, n = 1 at 12th month and 18th month and no patient was found with none CyR out of 196 patients; no patient were found with minimal CyR at 6th month, 2 patient were at 12th month and 3 patients were at 18th month. Mean PCR value (BCR-ABL/ABL ratio) in patient was found 0.245±1.16 at Day 0, 0.824±1.51 at 6th month, 4.086±9.58 at 12th month and 6.713±11.32 at 18th month visit. In conclusion, it was observed that resistance to imatinib might be developed within an average time of 12 months in the patients due to which survival rate was drastically reduced.

 

KEYWORDS: Cancer, CML, Imatinib, BCR-ABL, Mutation, Resistance.

 

 


INTRODUCTION:

Chronic Myeloid Leukemia (CML), also known as chronic granulocytic leukemia (CGL), is a cancer of the white blood cells.1 CML is a clonal bone marrow stem cell disorder in which proliferation of mature granulocytes (neutrophils, eosinophils, and basophils) and their precursors is the main finding. It is a type of myeloproliferative disease associated with a characteristic chromosomal translocation called the Philadelphia chromosome.

 

 

Imatinib is a tyrosine kinase inhibitor that shows promise in CML. The BCR-ABL transcript of CML has tyrosine kinase activity, which is necessary for its ability to cause leukemic transformation. Imatinib is an ABL protein tyrosine kinase inhibitor. Imatinib is available as 100-mg PO capsules or 400-mg PO tablets.2

 

Imatinib is a protein-tyrosine kinase inhibitor that inhibits the BCR-ABL tyrosine kinase, the constitutive abnormal tyrosine kinase created by the Philadelphia chromosome abnormality in CML. It inhibits proliferation and induces apoptosis in bcr-abl positive cell lines as well as fresh leukemic cells from Philadelphia chromosome positive chronic myeloid leukemia. In vivo, it inhibits tumor growth of bcr-abl transfected murine myeloid cells as well as bcr-abl positive leukemia lines derived from CML patients in blast crisis.3,4 The recommended dose of imatinib mesylate is 400 mg/day for adult patients in CML chronic phase and 600 mg/day for CML accelerated phase/blast crisis. The given prescribed dose should be given orally with meal and full glass of water.4,5 Despite imatinib can induce significant HR, CgR and even MolR in CML-CP patients, some patients fail to response optimally to imatinib or progress to advanced disease. In the five-year follow-up of IRIS trial, 6% progressed to advanced disease, 3% had a hematologic relapse and 5% had a loss of MCgR. Moreover, response rate is lower and transient for most patients with advanced phases of CML.6-12 Therefore, studies into the mechanism of imatinib-resistance and the derivation of management strategies are essential to the optimized care of CML.6-12

 

In most patients with acquired imatinib resistance, the BCR-ABL kinase was still activated despite continuation of imatinib treatment. Point mutation of the kinase domain (KD) of BCR-ABL protein was found to be the commonest cause for the failure of inhibition and many different mutations were identified. On the other hand, KD mutation as the cause for primary resistance is much less common.6-12

 

Point mutations were found mainly clustered into several regions of the KD: the contact site of imatinib, the P-loop (a.a. 248-256) and the activation loop (a.a.381-402). Point mutation leads to a single amino acid change in the KD and a change in KD conformation. This either impairs binding of imatinib to the contact site or prevent BCR-ABL protein from achieving an inactive conformation to which imatinib exclusively binds.6-12

 

The clinical significance of different point mutations and their drug resistance varies. Studies showed that mutant clone of BCR-ABL positive cells can pre-exist before imatinib treatment and the selective pressure exerted by imatinib may confer growth advantage of the mutant and final emergence of clinical resistance. While several BCR-ABL mutants are still sensitive to higher concentration of imatinib, the mutant T315I (change of threonine to isoleucine at residue 315) is completely resistant due to the interruption of critical contact point to imatinib.6-12

 

Apart from KD mutation, kinase activity of BCR-ABL protein can also be reactivated through over expression of BCR-ABL protein. This can either be due to BCR-ABL gene amplification or an increase in BCR-ABL transcript level. Resistance to imatinib may also due to a reduced intracellular drug concentration. Intracellular concentration of imatinib is determined by the balance of active influx and efflux of drug into or out of the cell.13-15

 

Besides BCR-ABL dependent mechanism of resistance, studies also demonstrate a role for BCR-ABL independent mechanisms in imatinib resistance. The relationship between secondary chromosomal aberrations, clonal evolution and imatinib resistance is poorly understood. Over expression and activation of Src family kinase Lyn in the mediation of drug resistance is recently reported.13-15, 16-25

 

The objective of current study was to quantify the mutation resistance to specific drug therapy in CML patients.

 

MATERIAL AND METHODS:

Study design was drafted, presented and it was approved from institution as well as from institutional ethics committee. Consent was obtained from patient in vernacular language prior to enrollment in study.  Total 256 patients were enrolled from 14 Nov 2014 to 19 Jun 2017. Out of 256 patients enrolled as per eligibility criteria, 196 patients had completed study as per protocol. 

 

Visits as per following:

Visit 1: Day 0 - Screening,

Visit 2: Month 6,

Visit 3: Month 12,

Visit 4: Month 18 – End of Study.

 

Treatment During Study:

Dose of 400mg or 600mg of Imatinib were found to be prescribed to all patients.

 

Prestudy Analysis:

DEMOGRAPHY (Age, sex, height, weight, BMI), MEDICAL HISTORY/CLINICAL EXAMINATION (Any drug/tobacco addiction, food habits, alcohol, Physical examination, Family history, past history), VITAL SIGNS, CLINICAL LABORATORY TESTS (Laboratory tests were done prior to the study during screening for all patients), BLOOD SAMPLE COLLECTION (Blood sample was taken from the CML patients prior to the administration of the next dose).

 

Post Study Procedure:

Laboratory Investigation:

Blood samples were collected from the patient to see the haematological response, cytogenetic response and molecular response, which was correlated to measure resistance of patient with imatinib.

 

RESULT:

Table 1: Patient Characteristics

Characteristics

Number of patients

Total No. of patients enrolled

256

Total No. of patients completed

196

Gender

Male

Female

 

141

55

Age (Mean)

47.07±11.64

Age (Range)

18-69 years

 

Hematologic Response:

In first group patients are divided into complete haematological response and No haematological response. 89.29% (n = 175) of patients achieved complete haematological response and 10.71% (n = 21) did not achieve haematological response.

 

Molecular Response:

(a) Complete molecular response:

In second group, we divided our patients into those with CMolR (n = 41 at 6th months, 01 at 12th month and 18th month) and those without CMolR (n = 124 at 6th months, 182 at 12th month and 194 at 18th month), such that level of BCR-ABL transcripts as the test variable would yield a threshold value for imatinib levels that correlates with a molecular response.

 

(b) Major molecular response:

In third group we divided our patients into those with MMolR (n = 72 at 6th months, 14 at 12th month and 02 at 18th month) and those without MMolR (n = 124 at 6th months, 182 at 12th month and 194 at 18th month), such that level of BCR-ABL transcripts as the test variable would yield a threshold value for imatinib levels that correlates with a molecular response.

 

Cytogenetic Response:

In the fourth group, we divided our patients into those with none CyR, minimal CyR, minor CyR, partial CyR and complete CyR.

·       No patient was found with none CyR out of 196 patients.

·       No patient were found with minimal CyR at 6th month, 2 patient were at 12th month and 3 patients were at 18th month.

·       No patient were found with minor CyR at 6th month, 2 patient were at 12th month and 3 patients were at 18th month.

·       53 patients were found with partial CyR at 6th month, 119 patients were at 12th month and 150 patients were at 18th month.

·       Whereas 42 patients were found with complete CyR at 6th month, 2 patients were at 12th month and 1 patient were at 18th month.

 

All 196 patients visited site at every 6 months as required for CML patient and recommended by respective treating doctor.

 

Laboratory Value Re-Presented In This Section Are In The Form Of Mean±SD:

Mean Hb value was found 11.5±1.92g/dL at Day 0, 12.0±1.73g/dL at 6th month, 12.5±1.60g/dL at 12th month and 12.7±1.39g/dL at 18th month visit by patients.

 

Mean RBC value was found 4.1±0.79/cmm at Day 0, 4.4±0.71/cmm at 6th month, 4.7±0.69/cmm at 12th month and 4.8±0.61/cmm at 18th month visit by patients.

 

Mean WBC value was found 45170.4±96300.94/cmm at Day 0, 17236.1±28477.32/cmm at 6th month, 12637.8±21387.45/cmm at 12th month and 9997.2±10830.94/cmm at 18th month visit by patients.

Mean Platelets count was found 274770.4±241751.63 /cmm at Day 0, 288515.3±197887.52/cmm at 6th month, 319924.5±186724.88/cmm at 12th month and 321591.8±102412.02/cmm at 18th month visit by patients.

 

Mean blast cells count was found 8.3±13.67% at Day 0, 3.3±3.87% at 6th month, 2.3±4.09% at 12th month and 2.7±3.61% at 18th month visit by patients.

 

Mean promyelocytes value was found 4.7±2.09% at Day 0, 2.8±2.62% at 6th month, 2.4±2.95% at 12th month and 2.3±1.89% at 18th month visit by patients.

 

Mean myelocytes value was found 6.4±4.53% at Day 0, 3.1±2.53% at 6th month, 3.0±2.83% at 12th month and 3.3±2.63% at 18th month visit by patients.

 

Mean metamyelocytes value was found 6.7±3.85% at Day 0, 3.6±3.16% at 6th month, 3.3±3.73% at 12th month and 2.6±2.61% at 18th month visit by patients.

 

Mean band form cells count was found 4.6±2.03% at Day 0, 2.5±1.02% at 6th month and 2.2±1.83% at 12th month visit by patients.

 

Mean neutrophils count was found 54.8±13.63% at Day 0, 53.0±11.51% at 6th month and 45.8±12.59% at 12th month visit by patients.

 

Mean lymphocytes count was found 29.4±15.08% at Day 0, 28.3±12.81% at 6th month and 26.1±14.59% at 12th month visit by patients.

 

Mean monocytes count was found 5.4±2.74% at Day 0, 4.7±2.77% at 6th month and 3.3±2.79% at 12th month visit by patients.

 

Mean eosinophil count was found 3.8±2.89% at Day 0, 3.1±2.69% at 6th month and 2.2±2.14% at 12th month visit by patients.

 

Mean basophils count was found 2.5±3.53% at Day 0, 2.5±11.64% at 6th month and 1.7±2.65% at 12th month visit by patients.

 

Mean normoblast count was found 1.3±0.58/100 WBC at Day 0, 1.8±0.50/100 WBC at 6th month, 1.0±0/100 WBC at 12th month and 2.0±0/100 WBC at 18th month visit by patients.

 

Mean SGPT value was found 23.09±11.33U/L at Day 0, 27.67±14.61U/L at 6th month, 28.08±11.96U/L at 12th month and 29.23±6.93U/L at 18th month visit by patients.

 

Mean creatinine value was found 0.74±0.16mg/dL at Day 0, 0.80±0.35mg/dL at 6th month, 0.81±0.29mg/dL at 12th month and 0.87±0.22mg/dL at 18th month visit by patients.

 

Mean PCR value (BCR-ABL/ABL ratio) was found 0.245±1.16 at Day 0, 0.824±1.51 at 6th month, 4.086±9.58 at 12th month and 6.713±11.32 at 18th month visit by patients.

 

DISCUSSION:

Hematologic Response:

In current study, after 6 month of treatment period, 18.57% (n=154) of CML patient found with complete haemtological response (CHR), whereas after 12 months of treatment, 80.61% of CML patient gave CHR, and 89.29% (n=175) of CML patients achieved complete haematological response after 18 months of treatment period. 10.71% (n=21) CML patients did not achieve haematological response after 18 months of treatment period.

 

According to data presented above, it seems that patient giving a good haematological response to Imatinib treatment.

 

Figure 1: Heamatological Response to Imatinib

 

Molecular Response:

(a) Complete molecular response:

In this group, we categorised patients into those with CMolR (n = 41 at 6th months, 01 at 12th month and 18th month) and those without CMolR (n = 124 at 6th months, 182 at 12th month and 194 at 18th month), such that level of BCR-ABL transcripts as the test variable would yield a threshold value for imatinib levels that correlates with a molecular response.

 

(b) Major molecular response:

In this group, we categorised patients into those with MMolR (n = 72 at 6th months, 14 at 12th month and 02 at 18th month) and those without MMolR (n = 124 at 6th months, 182 at 12th month and 194 at 18th month), such that level of BCR-ABL transcripts as the test variable would yield a threshold value for imatinib levels that correlates with a molecular response.

 

(b) No molecular response:

Out of 196 patients, only 6 (3%) patients did not have any molecular response till 18 months of treatment duration.

 

Figure 2: Molecular Response to Imatinib (After 18 months)

 

Molecular monitoring accomplishes by detecting the presence of BCR-ABL1 mRNA using real-time quantitative polymerase chain reaction (RQ-PCR). Molecular monitoring is capable of detecting low levels of disease and is >3 logs more sensitive than conventional cytogenetics. In addition, the analysis can be performed on peripheral blood samples which makes the process more convenient than bone marrow sampling. Molecular responses are quantified by measuring the reduction in BCR-ABL1 transcripts relative to a standardized baseline.

 

In current study, considering different parameters for considering haematological and molecular response, minimal 175 patients showed compete haematological response whereas 111 patients showed CMR after 18 months of treatment follow up.

 

Cytogenetic Response:

Cytogenetic response was divided into none CyR, minimal CyR, minor CyR, partial CyR and complete CyR.

 

For cytogenetic response, following results were found in current study:

·       No patient was found with none CyR out of 196 patients.

·       No patient were found with minimal CyR at 6th month, 2 patient were at 12th month and 3 patients were at 18th month.

·       No patient were found with minor CyR at 6th month, 2 patient were at 12th month and 3 patients were at 18th month.

·       53 patients were found with partial CyR at 6th month, 119 patients were at 12th month and 150 patients were at 18th month.

·       Whereas 42 patients were found with complete CyR at 6th month, 2 patients were at 12th month and 1 patient were at 18th month.

 

Figure 3: Cytogenetic Response to Imatinib (After 6, 12 and 18 months)

 

As per the current study, it has been observed that most of the patient obligating cytogenetic response to imatinib therapy however in all studies the percentage of response found different. There was not any pattern observed for cytogenetic response to imatinib therapy.

 

Laboratory Values:

Haemoglobin (Hb):

In current study the baseline mean Hb value was found 11.5±1.92g/dL (at Day 0), however due to erythropoietin concomitant treatment, mean Hb found as 12.0±1.73 g/dL at 6th month, 12.5±1.60g/dL at 12th month and 12.7±1.39g/dL at 18th month. Therefore, as per most of the supporting documents, it has been observed that Hb level increases with Imatinib and erythropoietin.

 

There was no major difference observed with age groups i.e. ≤35 years, 36 to 50 years and >50 years of age; with gender groups i.e. Male and Female; with old or newly diagnosed patients.

 

Red Blood Cells:

In the current study the baseline mean RBC value was found 4.1±0.79/cmm (at Day 0), however mean RBC value was found 4.4±0.71/cmm at 6th month, 4.7±0.69/cmm at 12th month and 4.8±0.61/cmm at 18th month visit.

 

No any specific study available which covers change in RBC count however as per current study increase the level of RBC count was observed.

 

There was no major difference observed with age groups i.e. ≤35 years, 36 to 50 years and >50 years of age; with gender groups i.e. Male and Female; with old or newly diagnosed patients.

 

BLASTS:

In this study, mean blast cells count was found 8.3±13.67% at Day 0, 3.3±3.87% at 6th month, 2.3±4.09% at 12th month and 2.7±3.61% at 18th month.

 

In age group between 36 to 50 years, initially blasts count found higher compared to <36 years of age group and >50 years of age group.

 

In female patients, blast cells found higher than in male. Moreover, blast crisis is also observed in female patient after 2 months of treatment where as in male patients blast crisis till 18 months is not observed.

 

In newly diagnosed patients, pattern was found that blasts cells are higher during diagnosis and it decreases with duration of treatment whereas in old diagnosed patients, blasts cells count found near to normal level due to already ongoing treatment however blast crisis may be observed during the study.

 

Figure 4: Hb, RBC and Blasts Value Changes in Response to Imatinib (After 6, 12 and 18 months)

 

White Blood Cells:

In current study, similar type of results were observed that WBC count decreases from baseline to 8 months of treatment period. Mean WBC value was found 45170.4±96300.94/cmm at Day 0, 17236.1±28477.32 /cmm at 6th month, 12637.8±21387.45/cmm at 12th month and 9997.2±10830.94/cmm at 18th month visit by patients. Same has been presented in figure.

 

Figure 5: WBC Value Changes in Response to Imatinib (After 6, 12 and 18 months)

There was no major difference observed with age groups i.e. ≤35 years, 36 to 50 years and >50 years of age; with gender groups i.e. Male and Female; with old or newly diagnosed patients.

 

Platelets:

In the current study, mean Platelets count was found 274770.4±241751.63/cmm at Day 0, 288515.3±197887.52/cmm at 6th month, 319924.5±186724.88/cmm at 12th month and 321591.8±102412.02/cmm at 18th month.

 

Moreover, in the current study, it was observed that in age group ≤35 years, after start of treatment, patient platelets count were decreased but after 6 months it was started increasing. However, in age group 35 to 50 years and >50 years, platelet count was increasing. Same has been presented in figure.

 

When platelets counts compared as per gender, it was observed that in male patients it was slowly increasing however in male patients it was observed that it was slowly increased and later it was decreasing after 12 months of treatment. Same has been presented in figure.

 

In continuation to above observation, it was observed that in old diagnosed patients, the patient’s platelet count was in increasing pattern however in patients who are diagnosed newly in that there was decrease in platelet count in first 6 months, then increase in platelet count from 6th to 12th month and later it was again decreasing pattern from 12th to 18th month of treatment. In conclusion, there might not be any trend for platelets however after extrapolating the study, we can have correlation for the effect of imatinib according to age, gender and duration of CML diagnosis.

 

Basophils:

In current study, mean basophils count was found 2.5±3.53% at Day 0, 2.5±11.64% at 6th month and 1.7±2.65% at 12th month visit by patients.

 

Moreover, in the current study, it was observed that, in age group ≤35 years, basophils count increases intitally and then start to decrease however in other age groups it was continuously decreasing.

 

In both male as well as female, it was observed that basophil count was in decreasing pattern only.

 

However, in old patient diagnosed long back for CML and taking imatinib treatment, basophil count was found lower from initial start of study till end of study however in newly identified patients, it was observed that basophil count was higher and decreases with duration of treatment.

Eosinophil:

In current study, it was observed that mean eosinophil count was found 3.8±2.89% at Day 0, 3.1±2.69% at 6th month and 2.2±2.14% at 12th month in CML patients. On Day 0, maximum Eosinophil counts observed was 15.0%, however after 6 months of Imatinib treatment for CML, eosinophil count decreased to maximum 14.0% whereas after 12 months it was observed as maximum 12.0%.

 

Figure 6: Monocyte, Basophils and Eosinophil Value Changes in Response to Imatinib (After 6, 12 and 18 months)

 

There was no major difference observed with age groups i.e. ≤35 years, 36 to 50 years and >50 years of age; with gender groups i.e. Male and Female; with old or newly diagnosed patients.

 

Metamyelocytes:

In current study also, the mean metamyelocytes value was found 6.7±3.85% at Day 0, 3.6±3.16% at 6th month, 3.3±3.73% at 12th month and 2.6±2.61% at 18th month. It was observed continuous decrease of metamyelocytes counts with imatinib treatment.

 

There was no major difference observed with age groups i.e. ≤35 years, 36 to 50 years and >50 years of age; with gender groups i.e. Male and Female; with old or newly diagnosed patients.

 

Myelocytes:

In current study, it was observed that after imatinib treatment start, myelocytes count decreased till 12 months and later it was observed that myelocytes count start increasing. It can be considered that initial decrease in myelocytes were due to response to treatment however due to drug resistance/not response to treatment, myelocytes count starts increasing. The lab report found were: Mean myelocytes value 6.4±4.53% at Day 0, 3.1±2.53% at 6th month, 3.0±2.83% at 12th month and 3.3±2.63% at 18th month.

 

It has been found that in age group ≤35, myelocytes count was higher and it decreases with treatment however after 6 month it starts increasing and drastic rise in myelocytes occurs after 12 months of treatment period.

There was a significant difference found in gender male/female for myelocytes. In female it is observed that myelocytes decreases with duration of treatment however in male it decreases till 6 months and again start increasing after 6 month of treatment. Same has been presented in figure.

 

In newly diagnosed patients with CML, it has been observed that myelocytes count was continuously decreasing however in old CML patients, there was no any pattern observed. In old CML patients, it was found increase/decrease with duration of treatment. Same has been presented in figure.

 

Promyelocytes:

In current study, mean promyelocytes value was found 4.7±2.09% at Day 0, 2.8±2.62% at 6th month, 2.4±2.95% at 12th month and 2.3±1.89% at 18th month which shows decrease in promyelocytes count with duration of treatment.

 

In age group ≤35 years, promyelocytes count initially increases and after 6 month of treatment it starts decreasing however in age groups >35 years, promyelocytes count decreases with duration of treatment. It has been presented in figure.

 

There was no any significant difference found in patients male and female patients. Moreover, there was no any significant pattern observed in patient already diagnosed with CML (old patients in study) whereas there was decrease in promyelocytes count in newly diagnosed patients with CML.

 

Band Form Cells:

In current study, it was found that band form cells were higher during initial diagnosis however after start of Imatinib treatment band form cells decreases with duration of treatment.

 

In age group ≤35 years age, Band form cells count decreases initially however after 6 months of treatment it start increasing. Whereas in other age groups there was decrease in band form cells after treatment with Imatinib. It has been presented in figure.

 

There was no any significant difference found between both the genders i.e. male and female.

 

In patients newly diagnosed with CML, the band form cells counts decreases with duration of treatment however in old diagnosed patients, initially band form cells count decrease and after 6 month of treatment period it starts increasing. Graphical presentation for the same has been found as per figure.

 

Figure 7: Myelocytes, Promyelocytes, Metamyelocytes and Band form cells Value Changes in Response to Imatinib (After 6, 12 and 18 months)

 

Neutrophils:

In current study, mean neutrophils count was found 54.8±13.63% at Day 0, 53.0±11.51% at 6th month and 45.8±12.59% at 12th month.

 

There was no major difference observed with age groups.

 

There was no major difference observed with gender differences i.e. between male and female patients.

 

As per graphical presentation below, in newly diagnosed patients, neutrophils count increases initially and then after starts decreasing however in previously diagnosed patients, neutrophils count decreases continuously. Same has been presented in figure.

 

Lymphocytes:

In current study, mean lymphocytes count was found 29.4±15.08% at Day 0, 28.3±12.81% at 6th month and 26.1±14.59% at 12th month.

 

It has been observed that, in age group ≤35 years of age, initially lymphocytes count increases and later on it starts decreasing where as in age group 36 to 50 years and >50 years, the lymphocytes counts decreases i.e. immune system decreases for all age group more than 36 years. Same has been presented in figure.

 

There was no major difference observed with gender groups i.e. Male and Female.

 

In newly diagnosed patients, it has been observed that due to imatinib treatment, lymphocytes count increases i.e. immune system increases whereas in patients diagnosed from long time who are already on imatinib treatment, in such patient’s immune system (lymphocytes count) decreases. Same has been presented in figure.

 

Figure 8: Neutrophils, Lymphocytes and SGPT Value Changes in Response to Imatinib (After 6, 12 and 18 months)

 

Normoblast:

The change in value of normoblast from baseline to 18th Months were: Mean normoblast count was found 1.3±0.58/100 WBC at Day 0, 1.8±0.50/100 WBC at 6th month, 1.0±0/100 WBC at 12th month and 2.0±0/100 WBC at 18th month.

 

There was no any significant relation or change in normoblast count after treatment with imatinib observed. No particular relation with different age group, change in gender and newly or already diagnosed patients were observed.

 

SGPT and Creatinine:

Mean SGPT value was found 23.09±11.33U/L at Day 0, 27.67±14.61U/L at 6th month, 28.08±11.96U/L at 12th month and 29.23±6.93U/L at 18th month visit of patients.

 

Mean creatinine value was found 0.74±0.16mg/dL at Day 0, 0.80±0.35mg/dL at 6th month, 0.81±0.29mg/dL at 12th month and 0.87±0.22mg/dL at 18th month visit of patients.

 

There were no significant difference in SGPT and Creatinine depending on age group of the patient.

 

SGPT level was increases with treatment duration however the SGPT level was high in male compared to female patients. Similar result was observed in creatinine level.

 

In newly diagnosed patients, after start of treatment with Imatinib, a drastic rise in SGPT level was observed which leads to decrease however in old patients, SGPT increases with duration of treatment. There was no significant difference observed in creatinine level in new or already diagnosed patients.

 

Polymerases Chain Reaction:

In current study performed, Mean PCR value (BCR-ABL/ABL ratio) was found 0.245±1.16 at Day 0, 0.824±1.51 at 6th month, 4.086±9.58 at 12th month and 6.713±11.32 at 18th month.

 

Figure 9: PCR Value Changes in Response to Imatinib (After 6, 12 and 18 months)

 

Reverse transcriptase polymerase chain reaction (RT-PCR) chosen as the method of choice to determine the transcript variant of BCR-ABL, is one of the most sensitive methods for this purpose.67

 

Similarly, there was no any gender effect on PCR value. PCR value increase with duration of treatment.

 

Moreover, there was no any effect on PCR value due to whether patient is newly diagnosed or already diagnosed with CML. PCR value increase with duration of treatment.

 

Product Limit Survival Estimate:

Among patients presenting in AP, survival has improved significantly by year of therapy. The estimated 8-year survival rate has increased from less than 20% before 1990, to 45% in the years 1991-2000, to 75% since 2001. This suggests the strong impact of imatinib therapy in AP-CML and the need to develop new “AP” criteria that predict for a very short survival.62

 

Figure 10: Product Limit Survival Estimate to Imatinib (After 6, 12 and 18 months)

In current study, it has been observed that the survival rate was decreasing with increase duration of treatment which also confirms either of two reasons as per following:

 

1    Either patient is not taking medication,

2    Or patient is getting resistance from the treatment

 

It has been found from many literature from other countries that CML patient get resistance to Imatinib after 12 to 18 months. Similar type of result was found in current study from western region population that patients getting resistance after app. 12 months of treatment due to which survival rate was drastically decreased.

 

CONCLUSION:

The most common mechanism of relapse for CML patients treated with Imatinib is the appearance of point mutations in the BCR-ABL oncogene that confer resistance to the drug. From the study, it was observed that resistance to imatinib might be developed within an average time of 12 months in the patients due to which survival rate was drastically reduced.

 

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

 

REFERENCES:

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Received on 01.07.2020           Modified on 08.09.2020

Accepted on 19.10.2020         © RJPT All right reserved

Research J. Pharm. and Tech. 2021; 14(8):4092-4100.

DOI: 10.52711/0974-360X.2021.00709