With the power of the SEER database, data from 3979 patients with anaplastic glioma were included, including 2064 who underwent either biopsy or partial excision and 1915 who underwent GTR, which enabled us to perform multivariable OS and CSS analyses. In the present study, we found a significant association between GTR and prolonged survival. We employed multivariate Cox regression and competing risk models to reduce confounding bias, and our findings remained valid in these multivariate models.
The prognosis for anaplastic glioma remains poor despite combination treatment with surgery, RT, and CT . In our cohort,48.13% of patients with anaplastic glioma underwent complete resection, and our findings were consistent with those of previous studies, in which the percentage ranged from 30-60% in different reported cohorts [5, 17, 18]. Randomized controlled trials (RCTs) have shown that patients with anaplastic glioma are more likely to benefit from postoperative adjuvant treatment [19, 20]. We also found that anaplastic astrocytomas accounted for approximately 54.96% of cases, making them the highest proportion among all patients with anaplastic glioma. Most postoperative patients included in our study had received radiation (76.28%) and CT (70.95%) in both arms. A possible explanation is that AA has a relatively high proportion, while adjuvant RT can improve survival , and CT prolongs survival for cases of AO or AOA [21, 22].
Although improved survival has been correlated with greater extent of resection in anaplastic glioma [12, 18, 23, 24], the longer survival benefit has not yet been determined. Other clinical studies have also suggested that patients with anaplastic glioma might not benefit from surgical resection [9, 10]. Two measures of survival were calculated for each resection group, namely OS and CSS, as each of these measures has unique strengths . Some studies analyzed 5-year OS instead of 10-year OS, and did not assess specific survival. We found that the 5-year and 10-year OS rates of the GTR group (59.9% and 45.0%, respectively) were higher than those of the N-GRT group (44.0% and 29.4%, respectively) (p<0.001). This is consistent with the results of several other studies in which those who underwent GTR exhibited improved survival rates [5, 18]. However, OS analyses after tumor diagnosis may be heavily influenced by competing causes of death; therefore, the CSD rate was analyzed in the present study, taking deaths unrelated to anaplastic glioma and confounding bias into consideration. The 5-year and 10-year CSD rates of the GTR group were lower than those of the N-GRT group in our cohort (p<0.001), whereas the difference in death from other causes between the two groups was similar (p=0.689). After controlling for competitive risk , the extent of resection was not found to be associated with a decreased risk of CSD in patients with metastatic tumor. However, we found that the risk of CSD was higher in the N-GRT group than in the GTR group. We speculated that this might be related to the relatively long survival time of the patients in the present study. The results of our study demonstrated that GTR was associated with increased survival in these patients.
Several studies have analyzed the risk factors associated with survival among patients diagnosed with grade III gliomas, including age, sex, tumor location, histologic type, extent of resection, and postoperative adjuvant therapy   [20, 29, 30]. However, few studies have reported the relationship between CSS and the extent of surgical resection in patients with anaplastic glioma. The GTR group was significantly associated with improved OS (HR: 0.72, 95% CI, 0.65-0.79, < 0.001) and CSS (HR: 0.72, 95% CI, 0.65-0.80, < 0.001) compared with the N-GTR group in the present study.
Interestingly, the association between OS and the extent of resection was stable for other clinical subgroups with respect to age, radiation, and CT. This showed that the extent of resection was positively associated with better OS in younger (HR: 0.65, 95% CI,[0.56-0.76] in N-GTR ) or older individuals (HR: 0.78, 95% CI, [0.70-0.88] in GTR), in those who did not undergo radiation (HR: 0.82, 95% CI, [0.68-0.99] in N-GTR) or in those who did (HR: 0.70, 95% CI, [0.63-0.78] in GTR), and in no-CT groups (HR: 0.76, 95% CI, [0.65-0.90] in N-GTR) or in CT groups (HR: 0.70, 95% CI, [0.62-0.78] in GTR). However, the associations in GTR were not observed in the infratentorial site and histologic type compared with N-GTR (both p for interaction <0.001). A possible explanation is that the aim of the surgical approach should be limited to infratentorial tumors due to the high incidence of surgery-related neurological impairment . The benefit of maximal surgery may be attenuated in patients in AO or AOA-relevant subgroups because of the chemosensitivity of the histologic type . GTR had OS benefits on cases of supratentorial tumors and AA subgroups . The effect of surgical resection in patients with anaplastic glioma should be explored further.
This study had several limitations. First, information on tumor molecular data or patient functional performance, which are factors that affect survival, were missing from the SEER database. Second, the detailed CT regimen and RT dosage were not recorded in the SEER database. Third, EOR threshold values are important for anaplastic gliomas . Fourth, the SEER database does not provide information on disease recurrence or subsequent treatment data.