Adults in Norway with diffuse low-grade gliomas who were treated at a hospital advocating early surgical resection had better overall survival than those treated at a hospital advocating “watchful waiting,” according to a report published online Oct. 30 in JAMA.

This finding significantly strengthens the sparse evidence in support of early resection for newly diagnosed diffuse low-grade gliomas, said Dr. Asgeir S. Jakola of the department of neurosurgery, St. Olav’s University Hospital, Trondheim (Norway) and his associates.

Management of these tumors is one of the major controversies in both neurology and oncology today, largely because the effect of surgery on survival is still unclear. The only evidence available until now was based solely on uncontrolled surgical series; some of these have reported that it is safe to withhold surgery until the lesions progress, while others have reported that immediate resection improves survival and delays the time to malignant transformation.

Both patients and physicians are reluctant to undertake immediate surgery when the evidence supporting that strategy has been so tenuous. They also are concerned that the risk of early and aggressive surgery outweighs the benefit, particularly when most patients are capable of normal activity and have a reasonably long life expectancy at diagnosis, the investigators said.

It is unlikely that a randomized, controlled study comparing the two approaches will ever be performed. Dr. Jakola and his colleagues therefore conducted a retrospective, population-based parallel-cohort study at two neurosurgical centers, each of which preferred one of these strategies over the other. Their “natural experiment” was possible because in Norway, there were two such facilities that were relatively close geographically and served a homogenous population. The nationalized health care system distributes training, resources, and personnel equally throughout the country, so the two hospitals were quite similar in other respects. And patient follow-up is 100%.

The 12-year study involved 153 adults with diffuse, histologically verified supratentorial grade I and II tumors diagnosed in 1998-2009, who were followed until death or until April 2011. The median follow-up was 7 years. Gliomas included astrocytomas, oligodendrogliomas, and oligoastrocytomas.

For patients with newly diagnosed low-grade gliomas, hospital A favored biopsy and watchful waiting. The 66 patients treated there typically were followed with MRI at 3 and 6 months, then yearly thereafter. They usually were offered surgical resection, if the lesions grew or showed signs of malignant transformation.

Hospital B favored immediate maximal safe tumor resection for the 87 patients treated there, with MRI follow-up at 6 and 12 months, then annually thereafter. This strategy was not pursued in some patients, however: notably, those who were elderly or had comorbidities and were likely to die from another cause before malignant transformation would take place, and those who had very widespread tumor infiltration that made resection impractical.

The two study groups were well balanced with regard to patient age and comorbidities, and rates of surgical rescue therapy were the same. There also were no differences between the two groups in complications or acquired neurologic deficits.

At the end of the study period, 34 patients (52%) from hospital A had died, compared with only 28 patients (32%) from hospital B. Median survival was 5.9 years at hospital A, but median survival had not yet been reached at hospital B, the researchers said (JAMA 2012;308: [doi:10.1001/jama.2012.12807]).

This survival advantage increased over time. Expected 3-year survival was 70% at hospital A vs. 80% at hospital B; expected 5-year survival was 60% at hospital A vs. 74% at hospital B; and expected 7-year survival was 44% at hospital A vs. 68% at hospital B.

In a post hoc analysis that attempted to account for differences between the two study groups in prognostic factors, the survival benefit for immediate resection remained robust. It also remained robust in another post hoc analysis that examined the subgroup of patients who had the most common glioma, a grade II astrocytoma. Median survival was 5.6 years at the hospital favoring watchful waiting, compared with 9.7 years at the hospital favoring early resection, in this large subgroup of patients.

Based on these findings, hospital A has changed its preferred strategy from watchful waiting to early resection, Dr. Jakola and his associates said.

“Despite the clear survival advantage seen, clinical judgment is still necessary in individual patients with suspected low-grade glioma since results will depend on patient and disease characteristics together with surgical results in terms of resection grades and complication rates,” they added.

One of Dr. Jakola’s associates reported holding stock in Sonowand, manufacturer of the 3-D ultrasound-based imaging system used in one of the study hospitals.