The correlation between dose of folinic acid and neurotoxicity in children and adolescents treated for osteosarcoma with high-dose methotrexate (HDMTX): a neuropsychological and psychosocial study

A Comprehensive Review of Neuropsychologic Studies Supports the Concept That Adequate Folinic Acid Rescue Prevents Post Methotrexate Neurotoxicity

PURPOSE

To review all studies providing evidence of the correlation between folinic acid (FA) rescue inadequacy and long-term cognitive damage in neuropsychological studies of children with acute lymphoblastic leukemia or osteogenic sarcoma treated under protocols using high-dose methotrexate and FA rescue.

METHODS

A comprehensive literature search was performed of all databases of the Web of Science Citation Index, during 1990-2020, for the terms: neuropsychological, neurocognitive, and cognitive, together with acute lymphoblastic (and lymphocytic) leukemia and osteogenic sarcoma. English-language peer-reviewed articles on neuropsychological assessments of children who had been treated with high-dose methotrexate without irradiation, and which included details of methotrexate and FA schedules, were selected. In addition, a personal database of over 500 reprints of articles from over 130 journals was reviewed on the subjects of methotrexate and FA and their side effects.

RESULTS

Three groups of studies were found and analyzed, with (1) no evidence of cognitive deterioration, (2) evidence of cognitive deterioration, and (3) more than 1 protocol grouped together, preventing separate analysis of any protocols, Protocols without cognitive deterioration reported adequate FA rescue, and those with cognitive deterioration reported inadequate FA rescue.

CONCLUSION

Neuropsychological evaluation supported inadequate FA being the cause of neurocognitive damage after high-dose methotrexate and that adequate FA rescue prevents this complication.

Leucovorin (folinic acid) rescue for high-dose methotrexate: A review

High-dose methotrexate (HDMTX) is active against various malignancies; it possesses serious toxicities and is associated with patient characteristics, dosage regimens, comedications, and physiological status. There are many strategies to overcome HDMTX-induced toxicities, such as hydration, alkalization, leucovorin rescue, and haemodialysis. Leucovorin rescue is a cornerstone for toxicity prevention in HDMTX treatment. However, the leucovorin dose adjustment and the existence of leucovorin overrescue are still controversial. At present, various methods for calculating leucovorin doses in different tumour types have been proposed, including empirical calculations based on MTX plasma concentration, the Bleyer nomogram, and other methods. Nonetheless, leucovorin rescue protocols differ greatly across tumour types and medical institutions. Further studies are needed to investigate the optimal dosage regimen for leucovorin rescue in various tumours using HDMTX.

Neurotoxicity after high-dose methotrexate (MTX) is adequately explained by insufficient folinic acid rescue

PURPOSE

To challenge the view that the dose of folinic acid rescue after high-dose methotrexate (MTX) has no significance in the prevention of neurotoxicity and to present the minority view that neurotoxicity can be prevented by an adequate dose of folinic acid, without compromising treatment results. Several fallacies that led to the misunderstanding of post MTX neurotoxicity are presented.

METHODS

Data mining using search engines was used to find relevant publications, and an e-mail survey of more than 60 authors of articles in this field was performed. All relevant articles identified were read in their entirety.

RESULTS

Examples of clinical studies with neurotoxicity following inadequate rescue are given. Some studies demonstrated no neurotoxicity when adequate doses of folinic acid rescue were started 24-36 h after the start of HDMTX rescue even after mega doses of MTX. Rescue started after 42 h was associated with neurotoxicity except in patients with low serum MTX levels after 24 and 36 h. ALL protocols with neurotoxicity, especially BFM-like protocols, are presented. Protocol is reported in which single protocol changes prevented neurotoxicity.

CONCLUSIONS

From the published data, when folinic acid rescue is given in a sufficiently high enough dose and is started 24-36 h after the beginning of the methotrexate exposure, and virtually all forms of post MTX neurotoxicity can be prevented without compromising therapeutic results.

Factors Affecting the Upper Limit of the Methotrexate (MTX) CSF Levels Achievable in Children With Brain Tumors Treated With High-dose Intravenous MTX

BACKGROUND

Little has been published in the medical literature on serum and cerebrospinal fluid (CSF) methotrexate (MTX) levels in children with brain tumors.

METHODS

Matched 24-hour serum and CSF MTX levels were studied after 113 treatments in 35 brain tumors patients.

RESULTS

A correlation between the 24-hour serum levels of MTX and MTX dosage was observed after 113 treatments in all 35 patients (r=0.39, P<0.001) but no statistical difference was found between CSF MTX levels in the irradiated and nonirradiated groups (P=0.12). Nonirradiated children received a lower dose of MTX (12.3±4.8 cf 14.8±3.7) (P=0.002). The 24-hour MTX CSF levels of these 2 groups were also found to be different (the nonirradiated group 7.6±9.8 cf 12.5±0.15.3). Using the Levene test for variances we found that these variances were not equal and therefore we used the Welch test which resulted in a P-value of 0.04. However, when an analysis of covariance was performed looking at evidence of CSF disease and MTX dose the radiation difference was no longer significant (P=0.15). The 24-hour CSF MTX levels in children without evidence of active CSF disease were consistently lower than those with active disease using a mixed-model analysis (P=0.002). Although a 24-hour CSF MTX level of at least 1 μM was observed after infusions of >5 g/m MTX in previously irradiated children and after infusion of ≥10 g/m in nonirradiated children this difference did not reach statistical significance. CSF MTX levels plateau at doses of MTX 15 g/m putting in doubt the value of administering even higher doses of MTX.

CONCLUSIONS

The 24-hour MTX CSF levels are higher in patients with active CSF disease. Doses of <10 gm/m in children with brain tumors may not achieve a guaranteed 24-hour MTX CSF level of 1 μM. There may be little value in a given dose of >15 g/m MTX as CSF levels plateau at this dose.

How long can folinic acid rescue be delayed after high-dose methotrexate without toxicity?

To determine the optimal time of folinic acid rescue after methotrexate (MTX) treatment in patients with ALL, we selected and evaluated relevant studies that included doses, rescue delay, and side effects. Rescue at 42-48 hours resulted in considerable toxicity, except when low doses of MTX were used (1 g/m(2)) or serum MTX levels remained consistently low at 24, 30, and 36 hours. Rescue started at 30-36 hours was safe. In the absence of evidence that later rescue improves prognosis, we suggest that folinic acid rescue (105 mg/m(2)) be started no later than 36 hours from the start of MTX (5-6 g/m(2)).

Challenging the clinical relevance of folinic acid over rescue after high dose methotrexate (HDMTX)

THE HYPOTHESIS

The use of adequate folinic acid rescue (in clinically relevant doses) after high dose methotrexate will prevent neurotoxicity without reducing treatment results.

METHODS

A literature search was performed to test the hypothesis that no evidence for the existence of folinic acid over-rescue of high-dose methotrexate (MTX) in clinically relevant situations exists (evidence that too much folinic acid reduced cure rate).

EMPIRICAL DATA

Examples of folinic acid over-rescue after lower doses of MTX were found and has been cited as evidence of over rescue of high dose MTX. Mega doses of folinic acid, used when toxic levels of MTX occurred, also could neutralize the MTX effect. Data were found to support the contention that higher levels of MTX require disproportionally higher folinic acid doses for rescue. Careful examination of the available studies after HDMTX yielded more convincing alternative explanations for reduction in cure rate than over rescue. Little convincing evidence for the existence of over rescue after HDMTX was found.

DISCUSSION

The rescue of high-dose MTX with an appropriate dose of folinic acid that can prevent toxicity, especially neurotoxicity, was not shown to reduce the therapeutic effect. No evidence was found that higher doses of folinic acid after high dose MTX reduces the therapeutic effect.

CONSEQUENCES OF THE HYPOTHESIS

Acceptance of the hypothesis can prevent harm being caused (especially brain damage) by reversing the trend of dose reduction in FA rescue. The recognition that the use of higher folinic acid doses is safe, can prevent neurotoxicity, and does not reduce prognosis has important implications for the development of effective non toxic treatment protocols.