Table 2.
Treatment characteristics of the study population
| Parameter | n (%) |
|---|---|
| SABR dose and fractionation | |
| 50 Gy in 5 fractions | 28 (36.8) |
| 50 Gy in 4 fractions | 18 (23.9) |
| 54 Gy in 3 fractions | 8 (10.5) |
| 60 Gy in 5 fractions | 6 (7.9) |
| 60 Gy in 3 fractions | 5 (6.6) |
| 48 Gy in 4 fractions | 5 (6.6) |
| Other | 6 (7.9) |
| Total SABR dose (Gy) | |
| Median | 50 |
| Range | 30–60 |
| SABR dose group | |
| ≥60 Gy | 12 (15.8) |
| 50–59 Gy | 55 (72.4) |
| 40–49 Gy | 8 (10.5) |
| <40 Gy | 1 (1.3) |
| Biologically effective dose* (Gy) | |
| Median | 112.5 |
| Range | 72–180 |
| Biologically effective dose group | |
| <100 Gy | 3 (3.9) |
| 100–129 Gy | 53 (69.7) |
| 130–149 Gy | 7 (9.2) |
| ≥150 Gy | 13 (17.1) |
| Receipt of PCI † | |
| Yes | 17 (23.0) |
| No | 53 (71.6) |
| Unknown | 4 (5.4) |
| Receipt of chemotherapy | |
| Yes | 45 (59.2) |
| No | 27 (35.5) |
| Unknown, but most likely‡ | 4 (5.3) |
| Type of chemotherapy | |
| Cisplatin/etoposide | 28 (57.1) |
| Carboplatin/etoposide | 19 (38.8) |
| Other/unknown | 2 (4.1) |
| Cycles of chemotherapy | |
| 1 | 3 (6.1) |
| 2 | 4 (8.2) |
| 3 | 4 (8.2) |
| 4 | 30 (61.2) |
| 6 | 4 (8.2) |
| 8 | 1 (2.0) |
| Unknown | 3 (6.1) |
| Timing of chemotherapy | |
| After SABR | 33 (67.3) |
| Before SABR | 12 (24.5) |
| Before SABR or concurrently | 2 (4.1) |
| Before SABR, concurrently, or after SABR | 1 (2.0) |
| Unknown | 1 (2.0) |
| Primary tumor response § | |
| Complete response | 19 (25.0) |
| Partial response | 29 (38.2) |
| Stable | 13 (17.1) |
| Progression | 3 (3.9) |
| Unknown | 12 (15.8) |
| Size of residual lesion (cm) | |
| Median | 1.3 |
| Range | 0.4–3.5 |
| SUVmax of residual lesion | |
| Median | 1.9 |
| Range | 0–6.1 |
Abbreviations: SABR = stereotactic body radiation therapy; PCI = prophylactic cranial irradiation; SUVmax = maximum standardized uptake value.
*
Assuming an α/β ratio of 10.
†
PCI, when delivered, was administered at a dose of 25 Gy in 10 fractions in all cases.
‡
In these patients, chemotherapy was most probably administered but could not be corroborated definitively owing to loss of follow-up.
§
In accordance with Response Evaluation Criteria in Solid Tumors.