A total of 600 patients with sLGG were included in the study (Fig. 1), with 445 undergoing surgical treatment alone and 155 undergoing surgical treatment with adjuvant radiotherapy (Tables 1, 2).

Flowchart illustrating the selection of patients from the NCDB database

There was no significant difference in sex distribution between the two groups (p = 0.26), with 247 patients (56%) being male in the surgery alone group compared to 78 patients (50%) in the surgery with adjuvant radiotherapy group. However, patients in the surgery with adjuvant radiotherapy group were significantly older, with a median age of 40.0 years (IQR: 22.5, 57.5) compared to 24.0 years (IQR: 9.0, 46.0) in the surgery alone group (p < 0.001).

Racial and ethnic distributions did not differ significantly between the groups (p = 0.37 and p = 0.65, respectively), with 79% vs. 78% White, 15% vs. 16% Black, 2.7% vs. 4.5% Asian, and 6.3% vs. 7.7% Hispanic among the surgery alone vs. surgery with adjuvant radiotherapy groups. Insurance status did not show any significant difference between the groups (p = 0.10), with most patients having private insurance (65% vs. 57%), followed by Medicaid (18% vs. 18%), and Medicare (8.8% vs. 17%). No differences were found in terms of income quartile distribution (p = 0.28).

In both groups, most patients lived in metropolitan areas (70% vs. 70%), followed by urban (25% vs. 23%), and rural areas (1.1% vs. 1.3), with no significant difference between the groups (p = 0.89). The Charlson-Deyo comorbidity index was similar between the groups (p = 0.25), with most of the patients having a comorbidity index of 0 in the surgery alone group and surgery with adjuvant radiotherapy group (84% vs. 79%).

WHO grade was significantly different between the groups (p < 0.001). In the surgery alone group, 377 patients (85%) had a WHO grade of 1, and 68 patients (15%) had a WHO grade of 2. In the surgery with adjuvant radiotherapy group, 103 patients (66%) had a WHO grade of 1, and 52 patients (34%) had a WHO grade of 2.

Similarly, histological subtypes were significantly different between the groups (p < 0.001). In the surgery alone group, the two most prevalent subtypes were pilocytic astrocytoma with 347 patients (78%) and low-grade astrocytomas of unspecified histology with 69 patients (16%). In the surgery with adjuvant radiotherapy group, the two most prevalent subtypes were also pilocytic astrocytoma with 80 patients (52%) and low-grade astrocytomas of unspecified histology with 47 patients (30%).

There were no significant differences in the extent of surgical resection between the groups (p = 0.13). In the surgery alone group, 16 patients (3.6%) had a gross total resection (GTR), 62 (14%) had a subtotal resection (STR), and 367 (82%) had unspecified extent of resection. In the surgery with adjuvant radiotherapy group, 2 patients (1.3%) had a GTR, 30 (19%) had an STR, and 123 (79%) had unspecified resection.

Adjuvant chemotherapy was administered to 31 patients (7.0%) in the surgery alone group and 35 patients (23%) in the surgery with adjuvant radiotherapy group (p < 0.001). The median number of days from diagnosis to adjuvant chemotherapy was 44.0 days (IQR: 32.0, 80.0) in the surgery alone group and 43.5 days (IQR: 25.0, 102.0) in the surgery with adjuvant radiotherapy group (p = 0.97).

Palliative care was provided to 3 patients (0.7%) in the surgery alone group and 2 patients (1.3%) in the surgery with adjuvant radiotherapy group (p = 0.61). The rate of 10-day unplanned hospital readmission was similar in both surgery alone and surgery with adjuvant radiotherapy groups (3.8% vs. 2.6%; p = 0.32). The 30- and 90-day postoperative mortality rate were 0.9% and 2.5% in the surgery alone group and 0.6% and 3.2% in the surgery with adjuvant radiotherapy group, with no significant differences (p > 0.99 and p = 0.74, respectively).

In the pre-matching cohort, 97 patients (63%) received photon radiotherapy, 50 patients (32%) had an unspecified radiotherapy modality, and 7 patients (4.5%) received proton radiotherapy. The median number of days from diagnosis to radiotherapy was 48.0 days (IQR: 32.5, 74.0). The total radiation dose was 5,040 cGy (IQR: 4,500, 5,040).

In the post-matching cohort, 68 patients (63%) received photon radiotherapy, 33 patients (31%) had an unspecified radiotherapy modality, and 7 patients (6.5%) received proton radiotherapy. The median number of days from diagnosis to radiotherapy was 50.0 days (IQR: 33.3, 79.5). The total radiation dose was 5,040 cGy (IQR: 4,500, 5,040).

On survival analysis, the observed overall 5-year survival rate for the entire cohort reached around 80%, short of 75% at 10-years (Fig. 2). Survival analysis following stratificaiton of the cohort into surgery alone and surgery with adjuvant radiotherapy groups revealed a significantly higher mortality in patients who received adjuvant radiotherapy (p < 0.0001; Fig. 3).

Overall survival among the entire cohort of patients with spinal low-grade gliomas undergoing either surgery alone or surgery with adjuvant radiotherapy

Overall survival among patients with spinal low-grade gliomas undergoing surgery alone versus surgery with adjuvant radiotherapy, prior to propensity score matching

Following propensity score matching to account for potential confounders (Supplementary Figure A and Table A), the difference in overall survival among the groups was no longer significant (p = 0.11; Fig. 4).

Overall survival among patients with spinal low-grade gliomas undergoing surgery alone versus surgery with adjuvant radiotherapy, following propensity score matching