Overall survival
Some patients died of the disease in the follow up period. The number of evaluated patients was 81, 68, 56, 48, and 36 at 1, 2, 3, 4, and 6 months, respectively. At three and six months after RT, the OS rates were 78% and 56% (Figure 1A). At three and six months after RT, the OS rates were 86% and 79% in patients with stable spine and 76% and 51% in patients with unstable spine, respectively (Figure 1B). There was no association between the OS and SINS (stable (< 7) or unstable (≥7)) (P = 0.97).
Pain response
At each of one to six months, pain disappeared in 50 (62%), 57 (84%), 52 (93%), 47 (98%), and 36 (100%) of patients. There was no patient whose pain was difficult to be controlled by conservative treatment and required surgery.
Radiological assessment
At the beginning of RT, 28, 37, and 16 patients had lytic, mixed, and blastic lesions, respectively. The number of patients with lytic lesion was 26, 15, 4, 2, and 1 at 1, 2, 3, 4, and 6 months, respectively. The number of patients with mixed lesion was 38, 34, 32, 24, and 9 at 1, 2, 3, 4, and 6 months, respectively. The number of patients with blastic lesion was 17, 19, 20, 22, and 26 at 1, 2, 3, 4, and 6 months, respectively.
At the beginning of RT, 4, 50, 22 and 5 patients were > 50% collapse, < 50% collapse, no collapse with > 50% body involved, and no collapse with ≤ 50% body involved, respectively (Table 3). Then, the incidence of VBC at the beginning of RT was 54 patients (67%).
New VBC occurred in 6 patients (7%). It occurred no patient of no collapse with ≤ 50% body involved and 6 patients (27%) of no collapse with > 50% body involved at the beginning of RT. Its degree was less than 50% collapse, which occurred at 1 month after RT without no further collapse. Univariate analysis revealed that BQ (lytic lesion) and PLISE were the risk factors for new VBC (Table 4). Multivariate analysis revealed no factor for new VBC.
In patients of < 50% collapse at the beginning of RT, the collapse progressed in 30 patients (60%) till 1 to 4 months (median 1 month).In six patients the collapse progressed to be > 50% collapse. In patients of > 50% collapse at the beginning of RT, it progressed till 2 months (median 1 month) in 3 patients (75%). The rate of progression of collapse was 35%, 67%, 84%, 92%, and 92% at 1, 2, 3, 4, and 6 months, respectively (Figure 2). Univariate analysis revealed that PLISE was the only risk factor for progression of collapse at one month (Table 5). Multivariate analysis revealed that PLISE was the only risk factor for progression of collapse at one month (RR, 5.4; 95% CI, 1.08 to 27.72; P < 0.05).
At the beginning of RT, spinal deformity (kyphosis) was seen in 6 patients (7%). New deformity (kyphosis) occurred in 3 patients (4%) at 1 month after RT.
At the beginning of RT, destruction of posterolateral elements of the spine was seen in 19 patients (24%); unilateral in 16 patients (20%) and bilateral in 3 patients (4%). In 6 patients, it was repaired by re-calcification after RT.
SINS
The number of patients of stable, potentially unstable, and unstable were 14 (17%), 64 (79%), and 3 (4%), respectively at the beginning of RT. The median SINS was 8 (range, 5–13). There were 14 and 67 patients with stable (< 7) and unstable (≥7), respectively.
The number of patients with stable were 39 (48%), 43 (60%), 44 (77%), 40 (83%), and 33 (92%) at 1, 2, 3, 4, and 6 months after RT, respectively (Table 6). Patients with stable remained stable until last follow-up.
The score of SINS increased in 8 patients (10%) by the progression of the collapse and/or occurrence of deformity. The grade of instability was advanced in all but one patient in whom potentially unstable became unstable (1.2%).
The median SINS were 8, 7, 6, 5, 5, and 4 at the beginning of RT and after 1, 2, 3, 4, and 6 months, respectively, representing a significant decrease over time (P < 0.001) (Figure 3).
Univariate analysis revealed that overall dose (< 30Gy), BQ (lytic lesion), and PLISE were the risk factors for spinal instability at one month (Table 7). Multivariate analysis revealed that PLISE was the only risk factor for spinal instability at one month (RR, 6.3; 95% CI, 1.05 to 37.6; P < 0.05). At one month spinal instability was seen in 89% and 52% of the patients with and without PLISE, respectively, which was significant (P < 0.01).
Case 1
A case of 77 years old female of lung cancer patient is shown in Figure 4. At the beginning of RT, < 50% collapse of vertebral body and destruction of bilateral pedicles was seen, as score of 11 of SINS (Figure 4A, B). At 1 month after RT, pain continued and VBC progressed with occurrence of malalignment (kyphosis). No re-calcification was seen, as score of 13 of SINS (Figure 4C, D). At 2 months after RT, pain disappeared and no re-calcification was seen, as score of 10 of SINS (Figure 4E, F). At 3 months after RT, re-calcification (partial clerosis of initially lytic lesion) was seen in vertebral body as judged to be achieved mixed change. Then, the total SINS score was 9 (Figure 4G, H). At 4 months after RT, complete fill-in and sclerosis of initially lytic was seen in vertebral body, which was judged as achieved blastic change. Blastic change was achieved in both facets. Then, the total SINS score was 5 (Figure 4I, J).