Pediatric mature B-cell non Hodgkin lymphoma treatment with LMB-96 protocol. The Children Cancer Hospital Egypt experience

Purpose: Burkitt lymphoma (BL) is a highly aggressive mature B-cell non-Hodgkin lymphoma (NHL) and is the fastest growing human tumor. The outcome of childhood NHL has improved steadily over the past decades through the use of intensive sequential multi-agent chemotherapy regimens. Methods: A retrospective study having all patients 18 years old or younger diagnosed with mature B cell NHL and treated at Children Cancer Hospital Egypt (CCHE). All children were treated according to the modified (LMB 96) protocol during the period between July 2007 and December 2012. Patients were followed up till June 2013. Results: Three hundred and seventy-seven patients were diagnosed with mature B cell NHL and received the LMB96 treatment protocol. The majorities were males (76.4%) with a median age of 5.3 years, and ranged from 0.1-18.0 years. The median follow-up period was 28.2 months (range 0.9-72 months). Burkitt lymphoma was the most predominant pathologic subtype (79.6%, n = 300), and abdominal mass as a primary site was the most common presentation (71.3%). Twenty seven patients (7.2%) were treated as group A, 268 (71.0%) as group B, and 82 (21.8%) patients as high risk group C. Seventy-one (18.8%) patients suffered adverse events. Major adverse events were early deaths in 17 patients (4.5%), death during induction chemotherapy seen in 18 patients (4.7%), and during maintenance therapy in 7 patients (1.8%), tumor progression in 19 patients (5.0%), and relapse in 10 patients (3.7%). Sixty-three patients (16.7%) died during the study period. The main causes of death were tumor lysis syndrome (TLS) in 25.3%, and severe sepsis during chemotherapy in 41.3% of the patients. The 3 years OS and EFS were 83.3% and 80.4% respectively for the whole groups of patients. OS and EFS were 100% for group A, and 87.5%±3.9% and 85.9±4.3% for group B. For group C BM+/CNSpatients, OS was 55.62%±15.8%, and EFS of 53.8%±15.6%. For BM+/CNS+ patients, OS and EFS were 63.2%±21.76% and 57.9%±22.1% respectively. BM-/CNS+ patients had OS 72.4%±18.8% and EFS 67.6%±19.7% at 36 months. Conclusion: TLS and chemotherapy related toxicity remains a major challenge affecting the outcome of pediatric mature B cell NHL. We identified bone marrow involvement as a risk factor affecting treatment outcome. Aggressive supportive care measures are mandatory to avoid unacceptable high toxicity related mortality.


Introduction
Burkitt lymphoma (BL) is a highly aggressive mature B-cell non-Hodgkin lymphoma (NHL) and is the fastest growing human tumor. BL represents 40% of all childhood NHL and 3-4% of all childhood malignancies diagnosed each year in the USA. 1, 2 Its annual incidence in Africa has been estimated at 40-50 per million children younger than 18 years compared to 8 cases per million in France, and 7 per million in The Netherlands. 3 The outcome of childhood NHL has improved steadily over the past decades through the use of intensive sequential multi-agent chemotherapy regimens. In high-income countries, 5-year survival rates reaches 90% in patients treated according to the LMB 96 or BFM protocols [4][5][6][7][8] , while the therapy offered in oncology units in low-income countries is not as aggressive, and outcome is not as good. 9 The aim of the current study is to report the treatment outcome, overall survival (OS) and event free survival (EFS) of patients who received FAB LMB96 protocol at the Pediatric Oncology Department, Children Cancer Hospital-Egypt (CCHE) during a 5.5 years period. Also to report about incidence of tumor lysis syndrome, relapse rate, treatment related mortality and causes of death in these patients.

Methods and Materials
A retrospective study having all pediatric patients diagnosed with mature B cell NHL and treated at CCHE. All children were treated according to the modified (LMB 96) protocol during the period between July 2007 and December 2012, and were followed up till June 2013. Approval by our institutional scientific committee and informed written consent were obtained prior to starting chemotherapy.

Eligibility and risk stratification
Newly diagnosed children and adolescents (<18 years) with mature B-cell NHL were included in our study. Diagnosis was done according to the WHO classification and included Burkitt lymphoma (BL), Burkitt-like lymphoma (BLL), Diffuse large B cell lymphoma (DLBCL), mediastinal large B-cell lymphoma (MLBCL), and mature B-cell neoplasm not otherwise specified (NOS). 10 Staging was performed according to Murphy's classification. 11 Risk classification according to LMB96 protocol was defined as low risk group A with resected stage I and abdominal completely resected stage II; high risk group C with bone marrow disease (25% L3 blasts) or CNS disease defined by one or more of the following: any L3 CSF blast, cranial nerve palsy, clinical spinal cord compression, isolated intracerebral mass, cranial or spinal parameningeal extension; and intermediate risk group B, included all patients not eligible for group A or C. Exclusions to study enrollment included severe immunodeficiency syndromes, HIV positivity, previous malignancy, or prior chemotherapy.

Treatment
Chemotherapy was given according to the FAB LMB96 protocol Group A Patients assigned to group A received two courses of cyclophosphamide, vincristine, prednisone, and doxorubicin (COPAD) without intrathecal (IT) chemotherapy. 8

Group B
Patients received prophase cyclophosphamide, vincristine, and prednisone (COP), followed by induction chemotherapy consisting of two cycles of vincristine, prednisone, adriamycin, methotrexate, cyclophosphamide and intrathecal injection (COPADM), and two courses of cytarabine, methotrexate (CYM) as consolidation if they were in complete remission (CR) post first course of consolidation Patients with less than a 20% response on day 7 of COP and patients with residual disease after CYM-1 were upgraded to group C starting from CYVE1. 12

Group C
Following prophase COP, patients had induction chemotherapy which consisted of two cycles of COPADM (HD-MTX 8 g/m 2 ) followed by consolidation with 2 cycles of high-dose continuous infusion ofcytarabine plus etoposide (CYVE). Patients with CNS disease received additional IT therapy as well as an additional HD-MTX course between consolidation courses. At last, 4 maintenance cycles, the first consisted of COPADM, followed by three cycles with low dose cytarabine and etoposide (cycles 2 and 4), with the third cycle being similar to the first but without HDMTX and IT. 13

Criteria of response
Complete response (CR) was defined as complete disappearance of all tumor masses, partial response (PR; 20% -99% tumor reduction), no response (NR) or stable disease (SD); <20% tumor reduction. Progressive disease (PD) was > 25% increase in tumor size, while relapse was defined as recurrence of disease at any site after achieving CR. Failure was considered as relapses, deaths and failures to achieve a CR within the time frame.
Unresponsiveness to initial COP in itself was not considered a failure of the treatment strategy. Patients in critical condition (renal failure, sepsis, grade III/IV organ toxicity) were allowed to receive a second course of COP prior to proceeding to induction. 13

Statistical methods
Data was analyzed using the Statistical Package for Social Sciences (SPSS) for Windows package version 15 (SPSS Inc., Chicago, Illinois, USA). Numerical data was presented as mean ± standard deviation (SD), median and range. Qualitative data was presented as numbers and percentages. Kaplan Meier was used to estimate survival and Log rank test for comparison. Overall survival (OS) was defined as the time from diagnosis till the end of the study period or death, while EFS was defined as the minimum period from diagnosis till the occurrence of an event including induction failure, disease progression, relapse, second malignancy, lost FU or death from any cause. A P -value ≤ 0.05 was considered significant.

Results
Patients' characteristics: out of the 530 patients diagnosed with NHL between July 2007 and December 2012, 377 (71.2%) patients had mature B cell NHL and received the LMB96 treatment protocol. There was a significant male predominance with 288 male patients (76.4%) and 89 Females (23.6%). The median age was 5.3 years, and ranged from 0.1-18.0 years. Number of patients varied in age group, with the range from 0 to 4 years being the most common (44.0%).
Demographic characteristics of study patients are summarized in Table 1, while Table 2 shows common sites of CNS involvement.

Volume 3 • Number 2 • 2015
International Journal of Cancer Therapy and Oncology 3 www.ijcto.org   Table 3 shows the major adverse events in studied patients.

Chemotherapy outcome
Following the LMB96 protocol risk stratification, 27 patients (7.2%) treated as group A, 268 patients (71.0%) as group B, and 82 patients (21.8%) in high risk group C.
Group A All 27 patients stratified as group A (7.2%) received chemotherapy successfully, and are alive in CR.

Group B
Two hundred-sixty eight patients were stratified as group B.
Following initial COP course of chemotherapy; 218 (81.3%) had >20% radiologic response and continued on same line. Twelve patients (3.18%) died from severe sepsis and/or TLS during prophase. Twenty eight patients (10.4%) didn't receive COP and started COPAM directly as they were considered to have no bulky tumor (stage II unresected tumor and/or incomplete resection anastomosis of primary intestinal mass). Ten patients (3.7%) had mild to no response defined as less than 20% decrease in the initial tumor volume and were upgraded to group C. Eight patients (2.9%) died from sever sepsis during chemotherapy, 12 (4.4%) progression, and 8 (2.9%) relapses ( Table 3).

Events, relapses and tumor progression
Seventy-one patients (18.8%) suffered adverse events, 40 (10.6%) in group B, and 31 (8.2%) in group C. There were no events in group A patients. Major adverse events were early deaths in 17 patients (4.5%), death during induction chemotherapy seen in 18 patients (4.7%), death during maintenance therapy in 7 patients (1.8%), tumor progression in 19 patients (5.0%), and relapse in 10 patients (3.7%). Table 3 describes major events according to risk groups.

Discussion
This retrospective study describes the treatment outcome of pediatric patients treated on the LMB-96 in our institute during 5.5 years period. To the best of our knowledge, it's one of the largest single center patient's series in the Middle East region. Mean age of the patients is slightly lower than many previous studies 5,12,14 , but similar to our previous re-port 15 . Age category below 4 years was the most common in the studied group in contrast to other study groups 13,16 , were ages between 5-9 years being the most common, although age is not considered as risk factor 17

. Cairo et al. in 2012
identified advanced stage, increased LDH level > 2 X normal value, mediastinal disease and combined BM + /CNS + as the main risk factors for treatment response. 17 In our study, analysis of prognostic factors including age, gender, upfront tumor resection and CNS status were all statistically insignificance. Nevertheless, BM involvement was found to be associated with lower OS and EFS, but this difference was statistically insignificant probably due to small sample size.
The obvious male predominance observed in the current study is a common finding in pediatric mature B cell NH 5,12,13,[15][16][17][18][19][20] . BL and B-ALL were the predominant pathologic subtype followed by DLBC of the studied patients, but in different ratio, as they represented 5% of the patients compared to 14% 12 , 10% 13 , 11.7% 15 , 14.9% 14 and 31.4% 16 of the patients in different studies. Other rare subtypes observed were PMLBCL and mature B-NHL NOS.
In most studies reporting pediatric mature B cell NHL -including the present one-abdominal mass, stage III, group B were the most common presentation, followed by peripheral lymph enlargement including head and neck regions, mediastinal mass, CNS involvement but with different incidences according to the studies. 5,12,14,[15][16][17]20 In the current study, 15.1% of the patients had laboratory and/or clinical TLS, representing 11.1% of group B and 32.9% of group C patients reflecting its increased incidence in close association with tumor aggressiveness. Management of TLS was done using the administration aggressive hydration and allopurinol as non-recombinant urate oxidase is not available routinely in our country. In previous, studies laboratory TLS incidence ranged from 27% to 42% of the patients 21-24 , although clinical TLS incidence is much lower ranging from 4.4% to 8.4% [21][22][23] .
Low risk group A patients represented 7.2% compared to 71.0% group B and 21.8% for high risk group C patients. In group A patients, incidence is in concordance with Patte et al. 5 , and higher than our previous report 15 , this is probably be due to accumulation of experience and better risk stratification. In group B and C patients, similar incidence was reported in the literature. 5 16 . This could be explained by high rate of chemotherapy related mortality (11.1%), as relapse rate and disease progression in our study (8.7%) were not higher than any study group report. 12,14,16 Fifty percent of group C patients in our study were BM + , while 26% had CNS involvement and 24% were both BM + and CNS + . Similar incidence rate was reported. 5,[13][14][15][16] Our worst results are in high risk group C BM + /CNS -, and BM + /CNS + patients. OS was 55.62%±15.8% and 63.2%±21.76 % respectively, while EFS was 53.8%±15.6% and 57.9%± 22.1% respectively. The sub-group of patients with BM involvement at diagnosis was associated with poor outcome, compared to CNS involvement. To the contrary of most of the studies, combined BM + and CNS + , or those with CNS + disease had the worst outcome 5,13,16,17,[26][27][28][29] and B-ALL had excellent overall survival; 88% 5,13,14,27,28 , and 86.2%+4.0% 16 . This might be due to the fact that patients with BM involvement express more hematologic toxicity and therapy related mortality.
Patte et al. identified CNS involvement as the only prognostic factor in group C patients. 5 Similar conclusion was reported by most of the study groups. 13,14,16,17,25

Conclusion
In conclusion, chemotherapy related toxicity remains a major challenge affecting the outcome of pediatric mature B cell NHL. We identified BM involvement, and treatment related toxicity during prophase/induction period of treatment as risk factors affecting outcome. Aggressive supportive care measures are mandatory to avoid unacceptable high toxicity related mortality.