Acute Lymphoblastic Leukemia After Temozolomide Treatment for Anaplastic Astrocytoma in a Child With a Germline TP53 Mutation

Abstract
We present a case of a 12-year-old female with a germline TP53 mutation who developed anaplastic astrocytoma and subsequently acute lymphoblastic leukemia (ALL) 13 months after starting treatment with temozolomide (TMZ). The patient had no significant family history of malignancy except for her grandfather and his siblings. Although alkylating agents such as TMZ are known to induce secondary hematologic malignancies, this case highlights the potential leukemogenic risk of TMZ, particularly in the context of genetic predisposition.

Key words: alkylating agent; glioma; p53; temozolomide; treatment-related acute leukemia

Introduction
Temozolomide (TMZ) is an oral alkylating agent used in the treatment of gliomas. Its main toxicity is myelotoxicity, but the incidence of grade 3–4 events is less than 10%. Because of its efficacy and tolerability, TMZ has become the first-choice chemotherapy for high-grade gliomas, contributing to prolonged survival. Before TMZ, alkylating agents such as carmustine (BCNU), lomustine (CCNU), nimustine (ACNU), and procarbazine were used as first-line treatments for malignant gliomas. These agents, as well as topoisomerase inhibitors (e.g., etoposide), are well known to induce treatment-related myelodysplastic syndrome (t-MDS), acute myeloid leukemia (AML), or acute lymphoblastic leukemia (ALL) in cancer patients. The development of t-MDS/AML and ALL is related to dose, therapy duration, and patient age.

Since TMZ therapy for gliomas has been introduced after the use of other alkylating agents and has improved survival, treatment-related acute leukemia (t-AL) may be on the rise in patients with gliomas. However, reports of t-AL associated with TMZ are few, and it remains unclear whether TMZ has the same leukemogenic potential as other alkylating agents. Here, we present a case of ALL occurring in a child with anaplastic astrocytoma after TMZ monotherapy, possibly in association with a germline TP53 mutation.

Case Report
A 12-year-old female developed numbness on her right side and was admitted to another hospital. She had no other medical history, but her grandfather had gastric cancer and two of his siblings also had cancer. Brain MRI showed bilateral diffuse infiltrating tumors with contrast enhancement. She was transferred to our hospital and underwent a right frontal lobe biopsy, which confirmed anaplastic astrocytoma.

She started combination treatment with TMZ and local brain radiotherapy. TMZ was administered orally at 75 mg/m² daily for 6 weeks. Local brain radiotherapy was delivered simultaneously at a total dose of 60 Gy in 30 fractions of 2 Gy, limited to the high-intensity region of the brain on T2-weighted MRI. After combined therapy, she started maintenance chemotherapy with TMZ at 150 mg/m² daily for 5 days. One month later, the TMZ dose was increased to 200 mg/m² daily for 5 days every month, and she received eight more cycles of TMZ. Between the fifth and sixth courses, she developed excessive myelosuppression and chemotherapy was suspended for 2 weeks.

Thirty-seven days after the last dose of TMZ, her peripheral blood contained 34% leukemic blasts, and she was referred to the pediatric oncology department. On admission, her white cell count was 4,100/μl, hemoglobin was 12.3 g/dl, and platelet count was 25,000/μl. The differential count showed 46% neutrophils, 4% eosinophils, 4% monocytes, 11% lymphocytes, 3% myelocytes, and 35% leukemic blasts. Serum LDH was 663 U/L. Bone marrow aspiration demonstrated massive infiltration of blast cells (86%). Flow cytometry revealed the blasts were positive for CD10 (78%), CD19 (100%), HLA-DR (100%), CD45 (100%), TdT (85%), and CD34 (24%). Cytogenetic analysis showed no chromosomal abnormality. A diagnosis of precursor B ALL was made.

The patient was treated with induction chemotherapy consisting of prednisolone, vincristine, pirarubicin, and asparaginase. Central nervous system prophylaxis was administered with intrathecal methotrexate, cytarabine, and hydrocortisone. Consolidation therapy was started but soon suspended due to complications. Follow-up MRI during ALL treatment revealed slight brain atrophy and hydrocephalus without evidence of tumor recurrence. She died from pneumonia eight months after the diagnosis of ALL.

DNA sequencing analyses for TP53 were performed on tumor and peripheral blood samples collected during the brain biopsy. A premature stop codon (CGA to TGA at codon 213) was detected in both samples, while immunohistochemistry for p53 protein revealed no positive staining in the tumor tissue.

Discussion
This report presents a case of TMZ-related ALL. This is the second published report of treatment-related ALL in glioma patients treated with TMZ and the first published report of t-AL in children after TMZ treatment for gliomas. The effect of radiotherapy on secondary MDS/AL is considered limited, so this case of ALL is mainly attributed to TMZ treatment and a germline TP53 mutation.

Reports of t-MDS/AML and ALL in glioma patients treated with nitrosoureas such as BCNU, CCNU, and ACNU have been accumulating, but the leukemogenic activity of TMZ has not been fully evaluated. Most t-MDS/AML cases associated with TMZ have involved prior treatment with other alkylating agents. Only four cases of t-MDS/AML and ALL have been reported after chemotherapy with TMZ alone in glioma patients (see Table I).

Secondary leukemia in cancer survivors accounts for 5–10% of all acute leukemias. While secondary MDS/AML are the most frequent, secondary ALL represents about 10% of all secondary leukemia cases. Genetic susceptibility is a possible explanation for ALL development in cancer patients. Heterozygous TP53 mutation results in Li-Fraumeni syndrome, a hereditary predisposition to cancer including astrocytic brain tumors and acute leukemia. However, de novo acute leukemia in Li-Fraumeni syndrome is rare, accounting for only 2.7% of cancers in affected kindreds, and germline TP53 mutations are uncommon in patients with acute leukemia.

Another possibility is that the ALL occurred as a random event. Given the patient’s TP53 germline mutation and family history of cancer, genetic background may have contributed to cancer development. Considering the leukemogenic activity of alkylators and the timing of ALL onset, TMZ may also be a primary factor in this case. TMZ is known to be particularly toxic to lymphocytes, and it is notable that two out of four reported TMZ-related MDS/AML and ALL cases presented as ALL.

The incidence of treatment-related acute leukemia (AL) has been reported in a large prospective study of 1,628 brain tumor patients treated with CCNU. Only 10.9% of participants were followed for more than two years, and only two cases of treatment-related AL were observed among 1,682 patients (0.12%). The median latency between therapy initiation and t-MDS/AML or ALL diagnosis has been reported as 31 months in brain tumor patients and 50–70 months in other malignancies. Thus, the true incidence of treatment-related AL may be higher than reported.

Chamberlain and Raizer reported seven cases of t-MDS/AML during glioma treatment: five patients had been treated with nitrosoureas and TMZ, and two with TMZ alone. These data indicate that combining nitrosourea and TMZ may increase the incidence of alkylator-induced MDS/AML and ALL. However, there is no evidence that TMZ is more likely to induce secondary hematological malignancies than nitrosoureas or that it enhances the leukemogenic activity of other alkylators.

In conclusion, increasing evidence indicates that TMZ may have the same leukemogenic potential as other alkylating agents. Since TMZ has only been approved in the last decade and survival rates in glioma patients have increased, TMZ-related MDS/AML and ALL will likely become more frequent. Although treatment-related ALL is relatively rare among secondary leukemias,TMZ chemical it may become more problematic in glioma patients due to the increased use of TMZ.