Table 2.
Temporal Trends
| 2012 | 2013 | 2014 | 2015 | 2016 | 2017a | Totalb, N (%) | |
|---|---|---|---|---|---|---|---|
| Number of cases | 114 | 129 | 117 | 101 | 98 | 61 | 642 |
| Age-standardized incidence rate | 0.8 | 0.9 | 0.8 | 0.7 | 0.7 | — | 0.8 |
| Norway | 1.0 | 1.2 | 0.9 | 0.7 | 0.6 | — | 0.9 |
| Sweden | 0.7 | 0.8 | 0.8 | 0.7 | 0.7 | — | 0.8 |
| Preoperative work-up | |||||||
| MR spectroscopy | 36 (32) | 49 (38) | 40 (34) | 31 (31) | 39 (40) | 36 (59) | 244 (38) |
| Amino acid PET | 9 (8) | 6 (5) | 5 (4) | 7 (7) | 8 (8) | 1 (2) | 37 (6) |
| Preoperative DTI and/or fMRIc | 33 (55) | 41 (57) | 39 (56) | 33 (55) | 44 (76) | 33 (73) | 231 (61) |
| Neuropsychological assessment | 3 (3) | 6 (5) | 8 (7) | 12 (12) | 16 (16) | 17 (28) | 64 (10) |
| Initial surgical strategies | |||||||
| Watch-and-scan | 17 (15) | 25 (19) | 22 (19) | 14 (14) | 16 (16) | 8 (13) | 109 (17) |
| Resection within 3 monthsd | 63 (55) | 77 (60) | 65 (56) | 53 (52) | 48 (49) | 33 (54) | 347 (54) |
| Resection within 6 monthse | 77 (68) | 86 (67) | 77 (66) | 71 (70) | 62 (63) | 40 (66) | 422 (66) |
| Intraoperative techniques | |||||||
| Mapping or awake surgeryf | 15 (35) | 25 (45) | 32 (67) | 26 (63) | 31 (74) | 24 (71) | 157 (58) |
| Diagnosis | |||||||
| Astrocytoma | 49 (43) | 68 (53) | 56 (48) | 59 (58) | 52 (53) | 35 (57) | 330 (51) |
| Oligodendroglioma | 32 (28) | 39 (30) | 39 (33) | 27 (27) | 44 (45) | 26 (43) | 215 (33) |
| Oligoastrocytoma | 33 (29) | 22 (17) | 22 (19) | 15 (15) | 2 (2) | 0 (0) | 97 (15) |
| Molecular classificationg | 39 (34) | 37 (29) | 42 (36) | 48 (48) | 67 (68) | 53 (87) | 297 (46) |
| Adjuvant therapy | |||||||
| Early RT + CHT | 28 (25) | 28 (22) | 26 (22) | 19 (19) | 24 (24) | 25 (41) | 154 (24) |
| Early RT + PCV | 5 (4) | 4 (3) | 10 (9) | 10 (10) | 13 (13) | 10 (16) | 54 (8) |
| Surgical resection within 6 months, followed by early RT + CHT | 15 (13) | 20 (16) | 19 (16) | 11 (11) | 15 (15) | 17 (28) | 97 (15) |
| Surgical resection within 6 months, followed by early RT + PCV | 2 (2) | 2 (2) | 7 (6) | 3 (3) | 7 (7) | 8 (13) | 29 (5) |
Abbreviations: CHT, chemotherapy; DLGG, diffuse low-grade glioma; DTI, diffusion tensor imaging; fMRI, functional magnetic resonance imaging; IDH, isocitrate dehydrogenase; PCV, procarbazine, lomustine, and vincristine; PET, positron emission tomography; RT, radiotherapy; TMZ, temozolomide.
aThree centers did not register patients in 2017, and incidence rates were therefore not calculated for 2017.
bYear of primary surgery was missing in 22 cases, and the sum of cases may therefore not add up to 100% of the total case volume in the study period.
cWithin cases located in presumed eloquent brain regions as evaluated from preoperative structural MRI.
dSurgical resection within 3 months from when a DLGG was radiologically suspected.
eSurgical resection within 6 months from when a DLGG was radiologically suspected.
fMapping or awake surgery performed during primary resections in presumed eloquent locations (n = 270).
gMutational status of both IDH and 1p/19q assessed.