Biopsy versus resection in the management of high-grade gliomas in the elderly.

Abstract

We read with interest a recent paper by Almenawer et al.1 The authors performed a meta-analysis on biopsy versus partial versus gross total resection (GTR) in older patients with high-grade gliomas (HGGs). The authors compared patients undergoing overall resection (of any extent) with patients undergoing biopsy and found significantly longer overall survival and progression-free-survival, higher postoperative Karnofsky performance status (KPS), and lower morbidity and mortality. GTR was found to be superior to subtotal resection in terms of overall survival, postoperative KPS, and progression-free survival with no difference in morbidity and mortality. The authors concluded that maximum resections are safe and are associated with longer survival time, delayed tumor progression rates, and improved functional recovery. We would like to commend the authors on their efforts to examine the impact of extent of resection on survival and functional outcomes for elderly patients with HGG. The benefit of maximal resection is uncertain in this age group since older patients tend to have more comorbidities, higher complication rates, and poorer prognosis overall. In addition, fundamental differences in tumor biology may explain some of the correlation between age and outcome.1 However, we have some doubts about the methodology and the conclusions reached by the authors. First, it is quite possible that biopsy was used for diagnostic purposes only in some of the studies included in the meta-analysis. In fact, this was clearly stated in the methods section of 3 studies.2–4 We believe it is not meaningful to include these studies in the meta-analysis since the goal of the paper was to compare outcomes in elderly patients who underwent different extents of resection, not between patients who had surgery versus those who did not. Secondly, the authors admitted that the greatest limitation in their meta-analysis was the inability to account for similar distribution of patient' characteristics. We agree with the authors that variables such as patient age, brain tumor location and size, adjuvant therapy, and preoperative baseline functional status should be taken into account when performing meta-analyses. Without looking at these factors, the conclusion reached (ie, that increasing extents of tumor resection are associated with improved outcomes) suffers from selection bias. However, these variables were presented in such a way in the individual studies that it is almost impossible to incorporate them into the meta-analysis (eg, using meta-regression). Therefore, we attempted to compare age, preoperative KPS, tumor location and size, and adjuvant treatment between biopsy and resection cohorts in the individual studies via qualitative analysis (Table 1). In the 12 studies that separated the age groups for the biopsy and resection patients, 11 reported either a higher proportion of older patients undergoing biopsy,2,5–8 or a higher mean age for the biopsy group.4,9–12 The biopsy group had a lower preoperative KPS score in 5 of the 9 studies that reported this information.2,6,12–14 The resection group was associated with a larger tumor size in the 2 studies that listed tumor size separately for the resection and biopsy groups.8,13 In the 4 studies that compared tumor location between biopsy and resection groups, patients with corpus callosum, deep lesions (eg, brainstem), and bilateral lesions were more likely to undergo biopsy,8,13,15 while endangerment of the eloquent area seemed to play little role in the decision-making process.14 In the 6 studies that reported number of patients receiving chemotherapy in the 2 groups, the proportion of patients receiving chemotherapy was higher in the resection group than that in the biopsy group in all 6 studies,2,10,11,13,14,16 while the proportion of patients receiving radiotherapy was higher in only 4 studies.2,10,11,13 Table 1. Biopsy versus resection in elderly patients with high-grade glioma In summary, even among the elderly, older patients tended to undergo biopsy rather than resection of their HGGs. Tumors located in the corpus callosum, deep lesions, and bilateral lesions were more likely to be biopsied than resected. Elderly patients undergoing resection of their HGG were more likely to receive chemotherapy than those who underwent biopsy. Consequently, the favorable outcomes associated with greater extent of resection in elderly patients may be influenced by the patient selection factors listed above and should be interpreted with caution.