Prior malignancy impact on survival outcomes of glioblastoma multiforme; population-based study

Glioblastoma multiforme (GBM) patients with a prior malignancy are usually excluded from clinical trials on GBM based on the assumption that this history will affect their survival outcomes. This practice may affect clinical trial accrual and limit the gathering of knowledge essential to the formulation of therapeutic options for this patient population. However, not much is known about the real impact of these prior malignancies on the survival of patients with subsequent GBM. We aimed to investigate the degree of such an impact.

We used the Surveillance, Epidemiology, and End Results (SEER) Program to analyze data of GBM patients diagnosed between 1973 and 2014. We calculated the overall and GBM-specific survival of these patients using the unadjusted Kaplan-Meier test and the multivariable covariate-adjusted Cox models.

Of 51,158 GBM patients, 3,076 had a prior malignancy. The unadjusted Kaplan-Meier test showed worse overall and GBM-specific survivals for patients who had a prior history of cancer. However, after adjusting for age at diagnosis of GBM, sex, race, marital status, and conduction of surgery, multivariable covariate-adjusted Cox models showed that having a prior malignancy did not significantly affect neither overall survival (HR = 1.025, 95%CI = .986 - 1.066, p = .213) nor GBM-specific survival (HR = 1.005, 95%CI = .963 - 1.049, p = .810).

Our findings suggest that the broad practice of excluding patients with a prior history of cancer should be reconsidered as it may adversely affect accrual, trial completion rates, and generalizability of the results.