GLIOMA SURVIVAL

The survival of adult patients with grade II and III gliomas has significantly improved during the past decade, according to research published online July 1 in Neuro-Oncology Practice.

The study represents the largest population-based assessment of overall survival and changes in practice patterns for low-grade gliomas.

"The study demonstrated that the median survival of patients afflicted with low-grade gliomas increased from 44 months (in 1999) to 57 months (in 2010). This is the first time that such increased survival has been reported," commented senior author Clark Chen, MD, PhD, of the Division of Neurosurgery, University of California, San Diego.

Low-grade gliomas are slow-growing brain tumors that are commonly found in young adults and often prove deadly. Because they are relatively rare, the disease remains understudied, according to Dr Chen.

Surgery remains the cornerstone of treatment for grade I, II, and III gliomas and is typically curative for grade I tumors. No consensus exists as to the standard of care for low-grade gliomas. Treatment decisions about radiation therapy, type of surgery, and what type of chemotherapy, if any, "vary widely" among clinicians, Dr Chen said.

Dr Chen and colleagues used data from the Surveillance, Epidemiology and End Results (SEER) database, which is run by the National Cancer Institute and represents about 28% of the US population.

The team found that 2497 (7.97%) grade I, 4113 (13.13%) grade II, 2755 (29.89%) grade III, and 21,962 (70.11%) grade IV gliomas were diagnosed from 1999 to 2010. Using time-trend analyses, they looked at overall survival, radiation treatment, and the extent of surgical resection.

Results showed an overall mortality of 5.86% for grade I, 51.18% for grade II, 67.4% for grade III, and 85.85% for grade IV gliomas. Overall survival for patients with grade I gliomas stayed about the same from 1999 to 2010. Overall survival improved, however, from 44 to 57 months in grade II gliomas, and from 15 to 24 months in grade III gliomas.

After adjusting for variables such as age, ethnicity, marital status, sex, tumor size, tumor location, extent of surgical resection, and radiation treatment, the differences in survival remained significant.

Use of temozolomide (Temodar, Merck Sharp & Dohme Corp) (TMZ) increased after 2005, when a landmark article about the efficacy of TMZ in grade II and III tumors appeared in the New England Journal of Medicine (N Engl J Med. 2005;352:987-996). After 2005, analyses showed that patients with grade II or grade III gliomas experienced statistically significant decreases in death (grade II: 2005-2007, P = .07; 2008-2010, P = .01; grade III: 2005-2007 and 2008-2010, P < .0001 for both).

"Notably, the median survival improved significantly in the time period after the use of the chemotherapy, temozolomide (1999-2004), relative to the period prior to temozolomide use (2005- 2010)," Dr Chen said, "These results suggest that the use of temozolomide is a likely contributor to the increased survival trend."

Dr Chen added a proviso, however. Although the "majority" of patients with low-grade gliomas may benefit from temozolomide, some studies suggest that the drug can induce more aggressive growth in a subset of low-grade gliomas, he cautioned.

"There is a critical need to develop molecular tools that afford the identification of this subset of patients and personalize oncologic care through precision medicine," Dr Chen emphasized.

After 2005, use of radiation statistically decreased in patients with grade II gliomas but stayed about the same for those with grade III disease. This change may have coincided with results of the European randomized control study EORTC 22845, published in 2005 (Lancet. 2005;36:985-990), which showed no significant improvement in survival when radiation was given at diagnosis instead of at disease progression.

Despite "substantial literature" suggesting that complete excision of low-grade gliomas can improve patient survival, the study found that "only about a third" of US patients underwent complete surgical resection, Dr Chen pointed out.

This number stayed about the same during the past decade, suggesting that there may be room for "meaningful gains" for improving outcomes using complete surgical resection, Dr Chen and colleagues write.

Extent of surgical resection and radiation therapy are "not likely" to have contributed to the overall improved survival for patients with grade II or III tumors, they explain. Instead, they point to general improvements in neuro-oncologic standard of care, the effectiveness of temozolomide for some patients, improved neuroimaging, and better understanding of the efficacy of radiation therapy.

The authors report no relevant financial relationships.

Neurooncology Pract. Published online July 1, 2015. Abstract