Treatment-related neurotoxicity

Neuroimaging of CNS infection in haematological malignancy: important signs and common diagnostic pitfalls

Patients with haematological malignancy are at increased risk of developing central nervous system (CNS) infections, which are associated with significant morbidity and mortality. Neuroimaging plays a pivotal role in the diagnostic pathway of these patients; however, layers of complexity are added to image interpretation by the heterogeneity in imaging manifestations of haematological malignancies in the CNS, overlapping imaging features of CNS infection, treatment-related parenchymal changes and the presence of intracranial comorbidity. In this article, we review important intracranial findings of CNS infection cases accrued in 1,855 studies over more than a decade at a specialist tertiary centre. We offer schema to identify common and important neuroimaging features, discuss key differential diagnoses and frequent diagnostic pitfalls.

Primary CNS Lymphomas: Challenges in Diagnosis and Monitoring

Primary Central Nervous System Lymphoma (PCNSL) is a rare neoplasm that can involve brain, eye, leptomeninges, and rarely spinal cord. PCNSL lesions most typically enhance homogeneously on T1-weighted magnetic resonance imaging (MRI) and appear T2-hypointense, but high variability in MRI features is commonly encountered. Neurological symptoms and MRI findings may mimic high grade gliomas (HGGs), tumefactive demyelinating lesions (TDLs), or infectious and granulomatous diseases. Advanced MRI techniques (MR diffusion, spectroscopy, and perfusion) and metabolic imaging, such as Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) or amino acid PET (usually employing methionine), may be useful in distinguishing these different entities and monitoring the disease course. Moreover, emerging data suggest a role for cerebrospinal fluid (CSF) markers in predicting prognosis and response to treatments. In this review, we will address the challenges in PCNSL diagnosis, assessment of response to treatments, and evaluation of potential neurotoxicity related to chemotherapy and radiotherapy.

Cognitive and neuroimaging outcomes of different treatment regimens for primary CNS lymphoma

Evaluation of: Doolittle ND, Korfel A, Lubow MA et al. Long-term cognitive function, neuroimaging, and quality of life in primary CNS lymphoma. Neurology 81, 1–9 (2013). This study used a cross-sectional design to assess cognitive function, quality of life and structural brain imaging in primary CNS lymphoma survivors. In total, 80 patients treated with different high-dose methotrexate-based regimens with or without full-dose whole-brain radiotherapy were evaluated at a median of 5.5 years from diagnosis. Survivors treated with high-dose methotrexate-based chemotherapy and whole-brain radiotherapy had lower mean scores on tests of attention, executive function and motor speed, and had more white matter abnormalities on brain imaging in comparison to patients treated with high-dose methotrexate-based regimens without whole-brain radiotherapy. The strengths of the study include the comparisons across treatment modalities and the use of standardized assessment tools. The findings provide further evidence for the increased risk for delayed neurotoxicity following combined modality regimens.

O6-methylguanine-DNA methyltransferase (MGMT) immunohistochemistry as a predictor of resistance to temozolomide in primary CNS lymphoma

Temozolomide, an alkylating agent, has shown promise in treating primary central nervous system lymphoma (PCNSL). The enzyme O(6)-methylguanine-DNA methyltransferase (MGMT) repairs alkylating damage, such as that induced by temozolomide. We hypothesized that MGMT immunohistochemistry would predict resistance to temozolomide in PCNSL. A retrospective study of newly-diagnosed and recurrent PCNSL patients treated at our institution was conducted to study the predictive value of MGMT immunohistochemistry for response to temozolomide. 20 patients who were treated with temozolomide as a single agent were identified during the study time period. 6/20 patients demonstrated a response, corresponding to an objective response rate of 30 % (95 % CI 8-52). Five patients with low MGMT level (<30 %) showed a response to temozolomide. Only one of 10 patients (10 %) with high MGMT level (≥30 %) exhibited a response to temozolomide. Small sample numbers precluded formal statistical comparisons. Two patients with complete response remain alive without progressive disease 6.7 and 7.2 years after temozolomide initiation. Immunohistochemistry can be performed on small biopsies to selectively assess MGMT status in tumor versus surrounding inflammation. MGMT analysis by immunohistochemistry may predict response to temozolomide in PCNSL and should be prospectively investigated.

Changes in neurocognitive functioning and quality of life in adult patients with brain tumors treated with radiotherapy

This review aims to summarize what is currently known about neurocognitive outcome and quality of life in patients with brain tumors treated with radiotherapy. Whether potential tumor-controlling benefits of radiotherapy outweigh its potential toxicity in the natural history of brain tumors is a matter of debate. This review focuses on some of the adult main brain tumors, for which the issue of neurocognitive decline has been thoroughly studied: low-grade gliomas, brain metastases, and primary central nervous system lymphomas. The aims of this review are: (1) the analysis of existing data regarding the relationship between radiotherapy and neurocognitive outcome; (2) the identification of strategies to minimize radiotherapy-related neurotoxicity by reducing the dose or the volume; (3) the evidence-based data concerning radiotherapy withdrawal; and (4) the definition of patients subgroups that could benefit from immediate radiotherapy. For high grade gliomas, the main findings from literature are summarized and some strategies to reduce the neurotoxicity of the treatment are presented. Although further prospective studies with adequate neuropsychological follow-up are needed, this article suggests that cognitive deficits in patients with brain tumor have a multifactorial genesis: radiotherapy may contribute to the neurocognitive deterioration, but the causes of this decline include the tumor itself, disease progression, other treatment modalities and comorbidities. Treatment variables, such as total and fractional dose, target volume, and irradiation technique can dramatically affect the safety of radiotherapy: optimizing radiation parameters could be an excellent approach to improve outcome and to reduce neurotoxicity. At the same time, delayed radiotherapy could be a valid option for highly selected patients.

Survival among patients with primary central nervous system lymphoma, 1973-2004

Primary central nervous system lymphoma (PCNSL) is a rare non-Hodgkin's lymphoma that occurs in immunocompetent and human immunodeficiency virus (HIV) patients. Despite treatment advances, previous reports have produced conflicting information about survival trends over time. Using the Surveillance, Epidemiology, and End Results (SEER) data, 2,557 patients diagnosed with PCNSL between 1973 and 2004 were identified and classified by HIV status. Potential predictors of survival were evaluated using log-rank tests. Hazard ratios and 95% confidence intervals (CIs) were computed using a Cox proportional hazards regression model. The cohort included 1,732 (67.7%) HIV-negative patients and 825 (32.3%) HIV-positive patients. Median overall survival was 12 months (95% CI 10, 13) among HIV-negative patients. In this group, median survival increased over time, from 7.5 months (95% CI 6, 14) for patients diagnosed in the 1970s, to 14 months (95% CI 11, 20) for patients diagnosed in the 2000s. Independent predictors of mortality included older age (hazard ratio [HR] 1.03 [95% CI 1.02, 1.03]), earlier year of diagnosis (HR 0.98 [95% CI 0.98, 0.99]), male sex (HR 1.20 [95% CI 1.08, 1.34), married status (HR 0.70 [95% CI 0.63, 0.78]), and receipt of radiation therapy (HR 0.69 [95% CI 0.61, 0.77]). HIV positivity was a powerful adverse prognostic factor in the overall cohort (HR 4.55 [95% CI 4.01, 5.16]). Despite treatment advances, survival among PCNSL patients in the United States remains poor. However, in the subset of PCNSL patients who are HIV-negative, survival has improved over time.

Therapeutic challenges in primary CNS lymphoma

Optimum treatment for patients with primary CNS lymphoma remains challenging because there have not been any large randomised clinical trials of this rare tumour. Drugs used in treating systemic non-Hodgkin lymphoma have mostly proven ineffective because of difficulties crossing the blood-brain barrier. The recognition of the efficacy of high-dose methotrexate was a substantial therapeutic breakthrough and further advances, such as the development of polychemotherapy regimens, have built on this. Whole-brain radiotherapy can consolidate response to chemotherapy, but the associated toxic effects of chemoradiation can be unacceptable. Other effective approaches include disruption of the blood-brain barrier and the use of high-dose chemotherapy. Recently, there have been attempts to optimise multi-drug chemotherapy regimens by focusing on improving survival and reducing toxic effects. A promising area of research is the incorporation of novel targeted drugs into standard treatment frameworks. In the future, greater cooperation between research groups should hopefully lead to further therapeutic advances.

Comparison of oxaliplatin- and cisplatin-induced painful peripheral neuropathy in the rat

Although platinum-based cancer chemotherapies produce painful peripheral neuropathy as dose-limiting side effects, there are important differences in the pain syndromes produced by members of this class of drugs. In the rat, cisplatin-induced hyperalgesia has latency to onset of 24 to 48 hours, is maximal by 72 to 96 hours, and is attenuated by inhibitors of caspase signaling but not by inhibitors of the mitochondrial electron transport chain (mETC) and antioxidants. In contrast, oxaliplatin-induced mechanical hyperalgesia is already present by 5 minutes and peaks by 20 minutes. Whereas oxaliplatin hyperalgesia persists for weeks, starting around day 10 to 15, its severity decreases to a lower 2nd plateau level. The rapid-onset 1st plateau in oxaliplatin-induced hyperalgesia was characterized by prominent cold allodynia and in contrast to cisplatin was attenuated by inhibitors of the mETC and antioxidants but not inhibitors of caspase signaling. However, tested later during the 2nd plateau, it was characterized by less intense hyperalgesia and no cold allodynia and was attenuated by inhibitors of caspase signaling as well as by inhibitors of the mETC and by antioxidants.

PERSPECTIVE

The findings of this study distinguish between the neuropathic pain syndromes produced by members of a single chemical class of anticancer drugs and suggest that the underlying mechanisms of various forms of peripheral neuropathy may be different. Further, it defines the need for selective therapy for different types of neuropathy.

Implications of the blood–brain barrier in primary central nervous system lymphoma

✓ The optimal treatment of primary central nervous system lymphoma (PCNSL), a rare form of extranodal non-Hodgkin lymphoma, has yet to be defined. Whole-brain radiation therapy (WBRT) has limited efficacy as a single therapeutic modality and is associated with a high risk of delayed neurotoxicity. Methotrexate-based chemotherapy regimens yield poor drug penetration across the blood–brain barrier (BBB), thus necessitating administration of high doses with the concomitant risk of increased systemic and neurological toxicity. Combined-modality therapy (WBRT plus chemotherapy) can improve response and survival rates, yet it is associated with a high risk of neurotoxicity. The aim of chemotherapy in conjunction with BBB disruption is to maximize drug delivery to the brain and improve the agent's efficacy, while preserving neurocognitive function and minimizing systemic toxicity. Methotrexate-based chemotherapy regimens administered in conjunction with BBB disruption have shown promising results in PCNSL. Animal models of central nervous system lymphoma and drug neurotoxicity offer new possibilities to study the effects of various treatments on PCNSL and normal brain and can also help understand biological and pathophysiological aspects of this disease. Because the intact BBB is even less permeable to antibodies than it is to drugs, preclinical and clinical studies of monoclonal antibody delivery (for example, rituximab and 90Y ibritumomab tiuxetan) to the brain in conjunction with BBB disruption offer a new possibility to make these novel treatments more efficient against PCNSL. Regarding the evaluation of more sensitive and specific diagnostic imaging tools, iron oxide–based contrast agents for magnetic resonance imaging have shown promise for better differentiation of PCNSL from other white matter diseases.