Low-grade central nervous system tumors

Impact of temozolomide chemotherapy on seizure frequency in patients with low-grade gliomas

OBJECT

Seizures occur in approximately 80% of patients with low-grade gliomas (LGGs). The majority of patients are treated with anticonvulsant monotherapy; however, many patients require multidrug therapy, or their seizures are refractory to antiepileptic drugs altogether. The oral alkylating agent temozolomide has emerged as a potential initial treatment option for LGG. A few reports suggest an association between temozolomide and reduced seizure frequency in patients with intractable epilepsy.

METHODS

Using their clinical database, the authors identified adult patients whose LGGs were treated using temozolomide as the initial antineoplastic therapy at the University of Virginia Health System. As a control group, the authors assessed patients whose LGGs were under observation. All patients had seizure disorders that were treated with anticonvulsants. Seizure frequency in patients with intractable epilepsy was analyzed before and after treatment with temozolomide. Age at diagnosis, sex, antiepileptic drugs, pathological subtype, surgical treatment, and follow-up until progression were also assessed. Interval seizure frequency was meticulously analyzed at each neurooncology clinic visit. A meaningful difference in seizures was defined as a reduction in seizure frequency of greater than 50% per month.

RESULTS

Thirty-nine patients were identified in the temozolomide cohort and 30 patients in the control cohort. The median age at diagnosis was 46 years for the former cohort and 41.5 years for the latter. The median length of follow-up was 39 months for the temozolomide group and 37 months for the control group. There was a significant difference in reduced seizure frequency between patients receiving temozolomide (59%) and those who did not receive temozolomide (13%, p < 0.001). Seven patients (18%) in the temozolomide group displayed this improvement independent of antiepileptic drug adjustment compared with no patient in the control group (p < 0.001).

CONCLUSIONS

The authors' data suggest that a subset of patients with LGGs experience improvement in seizure frequency during treatment with temozolomide independent of antiepileptic drug adjustment. This decrease in seizure frequency appears independent of the natural history of seizures in patients whose tumors are under observation. Consequently, seizures in patients with LGGs may be better controlled with the combination of AEDs and temozolomide.

Health-related quality of life aspects in patients with low-grade glioma

Standard therapeutic options for brain tumors include surgery, radiotherapy, and chemotherapy. Unfortunately, these same therapies pose risks of neurotoxicity, the most common long-term complications being radiation necrosis, chemotherapy-associated leukoencephalopathy, and cognitive deficits. Currently, there is no consensus on the treatment strategy for these tumors. Because of the relatively slow growth rate of low-grade gliomas, patients have a relatively long expected survival. Compared to traditional outcome measures like (progression-free) survival, evaluation of health-related quality of life may be time-consuming and burdensome for both the patient and the doctor. Besides, given the relatively low incidence of brain tumors and the ultimately fatal outcome of the disease, the interest in HRQOL emerged relatively late in these patients. Moreover, the notion that the disease itself may affect the patient's ability to judge his or her own functioning may hinder the use of patient self-reported measures. The studies presented in this chapter describe outcomes of both single dimensional and multidimensional methods of studying HRQOL. Although only few studies incorporated HRQOL as outcome measure, most studies have embraced the notion that an accurate assessment of HRQOL must be based on patient self-report. HRQOL instruments from other cancer groups are adapted for use with brain tumor patients. The multidimensional scales used to study changes in HRQOL studies in brain tumor patients provide a more comprehensive view of what is important to the patient concerning living with their disease and receiving treatment. In future trials, more sensitive measures of long-term cognitive, functional, and HRQOL outcomes on LGG patients at important time points over the disease trajectory are needed to better understand the changing needs that take place over time.

Characterization of low-grade gliomas using RGB color maps derived from ADC histograms

PURPOSE

To use normalized apparent diffusion coefficient (nADC) histograms from patients with grade II oligodendroglioma (OD) and astrocytoma (AC) to generate RGB color maps that emphasize the differences between normal-appearing white matter (NAWM), oligo-like, and astro-like regions.

MATERIALS AND METHODS

NAWM and nonenhancing lesion (NEL) ADC values from 19 ODs and 11 ACs were summed to generate oligo-like (red), NAWM (green), and astro-like (blue) nADC histograms. These nADC histograms were then used to map nADC values to an RGB matrix.

RESULTS

Color maps of oligodendroglial tumor regions were generally visualized in pink, while color maps of astrocytic tumor regions showed various shades of blue. This technique was also applied to 23 patients with the more mixed subtype, oligoastrocytoma (OA), which showed a mixture of both blue and pink, which in many cases appeared to bleed into each other and were blotchy.

CONCLUSION

This technique allows for the visualization of biologically different regions within the whole tumor mass, which may aid in directing image-guided biopsies. This can be used to ensure that the biopsy is directed to regions that can more accurately define the dominant tumor characteristics.

Apparent diffusion coefficient and fractional anisotropy of newly diagnosed grade II gliomas

Distinguishing between low-grade oligodendrogliomas (ODs) and astrocytomas (AC) is of interest for defining prognosis and stratifying patients to specific treatment regimens. The purpose of this study was to determine if the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) from diffusion imaging can help to differentiate between newly diagnosed grade II OD and AC subtypes and to evaluate the ADC and FA values for the mixed population of oligoastrocytomas (OA). Fifty-three patients with newly diagnosed grade II gliomas were studied using a 1.5T whole body scanner (23 ODs, 16 ACs, and 14 OAs). The imaging protocol included post-gadolinium T1-weighted images, T2-weighted images, and either three and/or six directional diffusion imaging sequence with b = 1000 s/mm(2). Diffusion-weighted images were analyzed using in-house software to calculate maps of ADC and for six directional acquisitions, FA. The intensity values were normalized by values from normal appearing white matter (NAWM) to generate maps of normalized apparent diffusion coefficient (nADC) and normalized fractional anisotropy (nFA). The hyperintense region in the T2 weighted image was defined as the T2All region. A Mann-Whitney rank-sum test was performed on the 25th, median, and 75th nADC and nFA among the three subtypes. Logistic regression was performed to determine how well the nADC and nFA predict subtype. Lesions diagnosed as being OD had significantly lower nADC and significantly higher nFA, compared to AC. The nADC and nFA values individually classified the data with an accuracy of 87%. Combining the two did not enhance the classification. The patients with OA had nADC and nFA values between those of OD and AC. This suggests that ADC and FA may be helpful in directing tissue sampling to the most appropriate regions for taking biopsies in order to make a definitive diagnosis.

Low‐Grade Gliomas in Adults

Low-grade gliomas are a heterogeneous group of neoplasms usually encountered in younger patient populations. These tumors represent a unique challenge because most patients will survive a decade or more and may be at a higher risk for treatment-related complications. Clinical observations over the years have identified a subset of low-grade gliomas that tends to manifest more aggressive clinical behavior and require earlier, more aggressive intervention. Clinical and molecular parameters may allow better assessment of prognosis and application of risk-adjusted management strategies that may include resection, radiation, or chemotherapy. Improved methods of long-term cognitive and functional assessment are desperately needed in this patient population.