The future of neuro-oncology

Time trends in glioblastoma multiforme survival: the role of temozolomide

BACKGROUND

In 2005, maximum safe surgical resection, followed by radiotherapy with concomitant temozolomide (TMZ), followed by adjuvant TMZ became the standard of care for glioblastoma (GBM). Furthermore, a modest, but meaningful, population-based survival improvement for GBM patients occurred in the US between 1999 (when TMZ was first introduced) and 2008. We hypothesized that TMZ usage explained this GBM survival improvement.

METHODS

We used national Veterans Health Administration (VHA) databases to construct a cohort of GBM patients, with detailed treatment information, diagnosed 1997-2008 (n = 1645). We compared survival across 3 periods of diagnosis (1997-2000, 2001-2004, and 2005-2008) using Kaplan-Meier curves. We used proportional hazards models to calculate period hazard rate ratios (HRs) and 95% confidence intervals (CIs), adjusted for demographic, clinical, and treatment covariates.

RESULTS

Survival increased over calendar time (stratified log-rank P < .0001). After adjusting for age and Charlson comorbidity score, for cases diagnosed in 2005-2008 versus 1997-2000, the HR was 0.72 (95% CI, 0.64-0.82; p-trend < .0001). Sequentially adding non-TMZ treatment variables (ie, surgery, radiotherapy, non-TMZ chemotherapy) to the model did not change this result. However, adding TMZ to the model containing age, Charlson comorbidity score, and all non-TMZ treatments eliminated the period effect entirely (HR = 1.01; 95% CI, 0.86-1.19; p-trend = 0.84).

CONCLUSIONS

The observed survival improvement among GBM patients diagnosed in the VHA system between 1997 and 2008 was completely explained by TMZ. Similar studies in other populations are warranted to test the generalizability of our finding to other patient cohorts and health care settings.

Adult glioblastoma multiforme survival in the temozolomide era: a population-based analysis of Surveillance, Epidemiology, and End Results registries

BACKGROUND

Survival after a glioblastoma multiforme (GBM) diagnosis remained static during the several decades before 1999. We hypothesized that the progressive increase in temozolomide use for GBM treatment that began in 1999 in the United States would be paralleled by a corresponding improvement in survival.

METHODS

We included 19,674 GBM cases, ages 20 years or greater, diagnosed 1993 to 2007 in the population-based Surveillance, Epidemiology, and End Results Program database. We used proportional hazards models to calculate calendar period hazard ratios (HR) and 95% confidence intervals (CI), adjusted for demographic covariates. We compared survival across periods using the Kaplan-Meier method.

RESULTS

Starting with cases diagnosed in 1999 to 2001, we observed a progressive decrease in HRs compared with cases diagnosed in 1993 to 1995. The multivariate-adjusted HR for 2005 to 2007 versus 1993 to 1995 was 0.69 (95% CI, 0.65-0.72). Age-stratified analyses revealed that this progressive decrease occurred in all age groups except 80+ years. Two-year survival increased from 7% among cases diagnosed in 1993 to 1995 and 1996 to 1998 to 9% among cases diagnosed in 1999 to 2001, 13% in 2002 to 2004, and 17% in 2005 to 2007. The disparity in survival between young and old patients increased in the temozolomide era, with 2-year survival of 39% among cases diagnosed at ages 20 to 44 years and 1% among cases diagnosed at 80+ years in 2005 to 2007.

CONCLUSIONS

We observed a modest, but meaningful, population-based survival improvement for GBM patients in the United States. Widespread adoption of temozolomide represents the most likely explanation, although other treatment advances, such as increased extent of surgical resection, also may have played a role.