NEW YORK (Reuters Health) – The extent of resection and residual volume are independently tied to survival and recurrence after surgery for newly diagnosed glioblastoma, according to a retrospective study.
Gross total resection is associated with prolonged survival with glioblastoma, but it remains unclear whether increasing the extent of resection (EOR) and decreasing residual volume (RV) are linked with prolonged survival or delayed recurrence in patients for whom gross total resection is not possible.
Dr. Alfredo Quinones-Hinojosa and colleagues from Johns Hopkins University in Baltimore, Maryland, sought to determine whether there is an association between EOR and RV with survival and recurrence and, if so, to establish minimum EOR and maximum RV thresholds.
Their study, online November 26 in Neuro-Oncology, included 259 patients over 18 years old who underwent surgery for an intracranial glioblastoma between 2007 and 2011.
At last follow-up, 203 patients (78%) had died after a median survival of 13.4 months. Tumor recurred in 156 patients (60%) after a median progression-free survival (PFS) of 8.9 months.
Overall survival ranged from 79.0% at six months to 19.3% at 24 months, and PFS ranged from 73.3% at six months to 6.6% at 24 months.
EOR and RV were independently associated with overall survival and tumor recurrence. Median survival for patients with more than 70% resection was 14.4 months, compared with 10.5 months for patients with 70% resection or less (p=0.0003). Median PFS was 9.0 months for patients with more than 70% resection, compared with 7.1 months for patients with 70% resection or less (p<0.0001).
Patients with RV less than 5 cm3 survived a median 14.4 months, compared with 10.5 months for patients with more RV (p=0.0003). Median PFS was 9.2 months for patients with less than 5 cm3 RV, compared with only 7.5 months for patients with greater RV (p=0.005).
“More important than EOR is the postoperative RV,” the investigators say. “This is because it makes intuitive sense that patients with the same EOR may have disparate RVs, since EOR is dependent on the preoperative tumor volume.”
“This study showed that while EOR and RV are highly inversely correlated where increased EOR is associated with decreased RV, the inverse relationship was present only 37% of the time,” they explain. “EOR and RV are therefore not correlated in the majority of patients, which places an emphasis on understanding EOR and RV separately.”
The researchers conclude, “This study shows that the minimum EOR and maximum RV associated with survival and recurrence is 70% and 5 cm3, respectively. These thresholds may serve as minimum surgical goals when safe to do so and/or may guide adjuvant therapies.”
“However,” they caution, “it should be noted that there is inherent uncertainty in the tumor volume measurements in this study because calculations are based on 2-dimensional imaging and were further limited by slice thickness.”