CT-Myelography for High-Dose Irradiation of Spinal and Paraspinal Tumors with Helical Tomotherapy

Proton Therapy for Spinal Tumors: A Consensus Statement From the Particle Therapy Cooperative Group

PURPOSE

Proton beam therapy (PBT) plays an important role in the management of primary spine tumors. The purpose of this consensus statement was to summarize safe and optimal delivery of PBT for spinal tumors.

METHODS AND MATERIALS

The Particle Therapy Cooperative Group Skull Base/Central nervous system/Sarcoma Subcommittee consisting of radiation oncologists and medical physicists with specific expertise in spinal irradiation developed expert recommendations discussing treatment planning considerations and current approaches in the treatment of primary spinal tumors.

RESULTS

Computed tomography simulation: factors that require significant consideration include (1) patient comfort, (2) setup reproducibility and stability, and (3) accessibility of appropriate beam angles.

SPINE STABILIZATION HARDWARE

If present, hardware should be placed with cross-links well above/below the level of the primary tumor to reduce the metal burden at the level of the tumor bed. New materials that can reduce uncertainties include polyether-ether-ketone and composite polyether-ether-ketone-carbon fiber implants.

FIELD ARRANGEMENT

Appropriate beam selection is required to ensure robust target coverage and organ at risk sparing. Commonly, 2 to 4 treatment fields, typically from posterior and/or posterior-oblique directions, are used.

TREATMENT PLANNING METHODOLOGY

Robust optimization is recommended for all pencil beam scanning plans (the preferred treatment modality) and should consider setup uncertainty (between 3 and 7 mm) and range uncertainty (3%-3.5%). In the presence of metal hardware, use of an increased range uncertainty up to 5% is recommended.

CONCLUSIONS

The Particle Therapy Cooperative Group Skull Base/Central nervous system/Sarcoma Subcommittee has developed recommendations to enable centers to deliver PBT safely and effectively for the management of primary spinal tumors.

Dosimetric analysis on computed tomography myelography based treatment planning in stereotactic body radiotherapy for spinal metastases

This study aimed to quantitatively evaluate the influence of enhanced contrast on the CT myelography image of the spinal cord and/or cauda equina in addition to the target volume in spine SBRT treatment planning. In total, 19 patients who had previously undergone spine SBRT were randomly selected. The rigid image registration accuracy of CT myelography that aligned with the treatment planning CT was evaluated by calculating the normalized mutual information (NMI) and Pearson's correlation coefficient for the vertebral landmarks. At postregistration, the contrast-enhanced region of the CT myelography image was replaced with water-mass density, and the original treatment plan was recalculated on this image. For comparison, the dose was also recalculated on the contrast-enhanced CT myelography images. The NMI and Pearson's correlation coefficients for landmarks were 0.39 ± 0.12 and 0.97 ± 0.04, respectively. The mean D_0.035cc of the spinal cord and/or cauda equina on the CT myelography image with the contrast-enhanced region replaced by water-mass density showed -0.37% ± 0.64% changes compared with that of the treatment planning CT. Conversely, the mean D_0.035cc in contrast-enhanced CT myelography changed by -1.39% ± 0.51%. The percentage change in D_98% for the planning target volume was confirmed to be small by replacing the contrast-enhanced region with water-mass density (p < 0.01). The dose calculation of the target volume, spinal cord, and/or cauda equina using the CT myelography image that replaced the contrast-enhanced region with water-mass density could be a more appropriate procedure with less dose calculation uncertainty.

Evaluation of a proprietary software application for motion monitoring during stereotactic paraspinal treatment

PURPOSE

Stereotactic paraspinal treatment has become increasingly popular due to its favorable clinical outcome. An often-overlooked factor that compromises the effectiveness of such treatment is the patients' involuntary intrafractional motion. This work introduces and validates a proprietary software application that quantifies such motion for accurate patient monitoring during treatment.

METHODS

The software uses a separate full-trajectory cone-beam computed tomography (CBCT) after daily patient setup to establish reference projections. Once treatment starts, the software grabs the intrafraction motion review (IMR) image acquired by TrueBeam via the Varian iTools Capture software and compares it against the corresponding reference projection to instantly determine the 2D shifts of the vertebrae being monitored using the classical downhill simplex optimization method. To evaluate its performance, an anthropomorphic phantom was shifted 0, 0.6, 1.2, 1.8, 2.4, 3.0, and 5 mm in three orthogonal directions, immediately after the full-trajectory CBCT but prior to treatment. Depending on the scenario of shift, a nine-field fixed gantry intensity-modulated radiation therapy (IMRT) plan and/or a four partial-posterior-arcs volume-modulated radiation therapy (VMAT) plan were delivered. For the IMRT plan, three IMR images were acquired sequentially every 200 monitor units (MU) at each treatment angle. For the VMAT plan, one IMR image was acquired every 15° of each arc. For each IMR image, the software-reported 2D shift was compared with the ground truth. Certain tests were repeated with 1°, 2°, and 3° of rotation, pitch, and roll, respectively. Some of these tests were also repeated independently on separate days.

RESULTS

Based on the group of tests that involved only the IMRT delivery, the maximum standard deviation of the software-reported shifts for each set of three IMR images was 0.16 mm, with 95th percentile at 0.02 mm. For translational shift, the maximum registration error was 0.44 mm, with 95th percentile at 0.23 mm. Left unaccounted for, rotation and pitch degraded the registration accuracy mainly in the longitudinal direction, while roll degraded it mainly in the lateral direction. The degradation of registration accuracy is positively related to the degree of rotation, pitch, and roll. The maximum registration errors under 3° rotation, pitch, and roll were 2.97, 1.44, 2.72 mm, respectively. Based on the group of tests that compared IMRT delivery with VMAT delivery, the registration errors slightly increased as magnitude of shifts increased; however, they were well under the 0.5-mm threshold. No significant differences in registration errors were observed between IMRT and VMAT deliveries. In addition, the variation in registration errors among different days was limited for both IMRT and VMAT deliveries.

CONCLUSIONS

Our proprietary software has high repeatability, both intrafractionally and interfractionally, and high accuracy in registering IMR images with the reference projections for motion monitoring, regardless of the magnitude of shifts or treatment delivery technique. Rotation, pitch, and roll degrade registration accuracy and need to be accounted for in the future work.

Practice Building: Achieving Growth Through Computed Tomographic Myelography-Based Stereotactic Body Radiation Therapy for Spinal Metastases

Stereotactic body radiation therapy (SBRT) is as an effective method to treat spinal metastases. Imaging is a critical component in the workup of patients who undergo stereotactic radiation treatment. Computed tomographic myelography may be more accurate than magnetic resonance imaging in the delineation of neural elements during SBRT. The task we faced was to offer a standardized method to rapidly and safely obtain high-quality computed tomographic myelography as part of a robust spine SBRT program. In detailing our experience, we support the greater, active participation of radiologists in the multidisciplinary care of patients with spinal metastases, while encouraging other radiologists to foster similar collaborations at their own institutions.

A validated survival score for breast cancer patients with metastatic spinal cord compression

BACKGROUND

To create a validated scoring system predicting survival of breast cancer patients with metastatic spinal cord compression (MSCC).

PATIENTS AND METHODS

Of 510 patients, one half were assigned to either the test or the validation group. In the test group, eight pretreatment factors (age, performance status, number of involved vertebrae, ambulatory status, other bone metastases, visceral metastases, interval from cancer diagnosis to radiotherapy of MSCC, time of developing motor deficits) plus the radiation regimen were retrospectively investigated. Factors significantly associated with survival in the multivariate analysis were included in the scoring system. The score for each factor was determined by dividing the 6-month survival rate (%) by ten. The total score was the sum of the scores for each factor.

RESULTS

In the multivariate analysis of the test group, performance status, ambulatory status, other bone metastases, visceral metastases, interval from cancer diagnosis to radiotherapy of MSCC, and time of developing motor deficits were significant for survival and included in the score. Total scores ranged from 30 to 50 points. In the test group, the 6-month survival rates were 12% for 30-35 points, 41% for 36-40 points, 74% for 41-45 points, and 98% for 46-50 points (p < 0.0001). In the validation group, the 6-month survival rates were 14%, 46%, 77%, and 99%, respectively (p < 0.0001).

CONCLUSION

The survival rates of the validation group were similar to the test group. Therefore, this score was reproducible and can help when selecting the appropriate radiotherapy regimen for each patient taking into account her survival prognosis.

Metastatic spinal cord compression in patients with cancer of unknown primary. Estimating the survival prognosis with a validated score

BACKGROUND

This study aimed to create and validate a survival score for patients with metastatic spinal cord compression (MSCC) from cancer of unknown primary.

PATIENTS AND METHODS

The entire cohort (n = 182) was divided into a test group (n = 91) and a validation group (n = 91). In the test group, eight pretreatment factors including age, gender, Eastern Cooperative Oncology Group performance status (ECOG-PS), number of involved vertebrae, ambulatory status, other bone metastases, visceral metastases, and time of developing motor deficits were retrospectively analyzed.

RESULTS

The score included the prognostic factors that were significant for survival in the multivariate analysis (ECOG-PS, ambulatory status, visceral metastases, time of developing motor deficits). The score for each factor was determined by dividing the 6-month survival rate by 10. Prognostic scores represented the sum of the scores for the four factors and ranged from 5 to 20 points. The 6-month survival rates were 5% for < 14 points, 41% for 14-16 points, and 92% for > 16 points (p < 0.001). In the validation group, the 6-month survival rates were 7%, 38%, and 91% (p < 0.001).

CONCLUSION

This survival score can be considered valid and reproducible, since the survival rates of the validation group were comparable to those of the test group. This score can help when selecting the individual treatment and when counseling patients and relatives.

A survival score for patients with metastatic spinal cord compression from prostate cancer

BACKGROUND

This study aimed to develop and validate a survival scoring system for patients with metastatic spinal cord compression (MSCC) from prostate cancer.

PATIENTS AND METHODS

Of 436 patients, 218 patients were assigned to the test group and 218 patients to the validation group. Eight potential prognostic factors (age, performance status, number of involved vertebrae, ambulatory status, other bone metastases, visceral metastases, interval from cancer diagnosis to radiotherapy of MSCC, time developing motor deficits) plus the fractionation regimen were retrospectively investigated for associations with survival. Factors significant in the multivariate analysis were included in the survival score. The score for each significant prognostic factor was determined by dividing the 6-month survival rate (%) by 10. The total score represented the sum of the scores for each factor. The prognostic groups of the test group were compared to the validation group.

RESULTS

In the multivariate analysis of the test group, performance status, ambulatory status, other bone metastases, visceral metastases, and interval from cancer diagnosis to radiotherapy were significantly associated with survival. Total scores including these factors were 20, 21, 22, 24, 26, 28, 29, 30, 31, 32, 33, 35, 37, or 39 points. In the test group, the 6-month survival rates were 6.5% for 20-24 points, 44.6% for 26-33 points, and 95.8% for 35-39 points (p < 0.0001). In the validation group, the 6-month survival rates were 7.4%, 45.4%, and 94.7%, respectively (p < 0.0001).

CONCLUSIONS

Because the survival rates of the validation group were almost identical to the test group, this score can be considered valid and reproducible.

Prognostic factors in a series of 504 breast cancer patients with metastatic spinal cord compression

BACKGROUND

This study was performed to identify new significant prognostic factors in breast cancer patients irradiated for metastatic spinal cord compression (MSCC).

PATIENTS AND METHODS

The data of 504 patients with breast cancer patients with MSCC were retrospectively analyzed with respect to posttreatment motor function, local control of MSCC, and survival. The investigated potential prognostic factors included age, Eastern Cooperative Oncology Group (ECOG) performance score, number of involved vertebrae, other bone metastases, visceral metastases, pretreatment ambulatory status, interval from cancer diagnosis to radiotherapy of MSCC, time developing motor deficits before radiotherapy, and the radiation schedule.

RESULTS

On multivariate analysis, better functional outcome was associated with ambulatory status prior to RT (estimate - 1.29, p < 0.001), no visceral metastases (estimate - 0.52, p = 0.020), and slower development of motor deficits (estimate + 2.47, p < 0.001). Improved local control was significantly associated with no other bone metastases (risk ratio (RR) 4.33, 95% confidence interval (CI) 1.36-14.02, p = 0.013) and no visceral metastases (RR 3.02, 95% CI 1.42-6.40, p = 0.005). Improved survival was significantly associated with involvement of only 1-2 vertebrae (RR 1.27, 95% CI 1.01-1.60, p = 0.044), ambulatory status before radiotherapy (RR 1.75, 95% CI 1.23-2.50, p = 0.002), no other bone metastases (RR 1.93, 95% CI 1.18-3.13, p = 0.009), no visceral metastases (RR 7.60, 95% CI 5.39-10.84, p < 0.001), and time developing motor deficits before radiotherapy (RR 1.55, 95% CI 1.30-1.86, p < 0.001).

CONCLUSION

Several new independent prognostic factors were identified for treatment outcomes. These prognostic factors should be considered in future trials and may be used to develop prognostic scores for breast cancer patients with MSCC.

Do elderly patients benefit from surgery in addition to radiotherapy for treatment of metastatic spinal cord compression?

BACKGROUND

Treatment of elderly cancer patients has gained importance. One question regarding the treatment of metastatic spinal cord compression (MSCC) is whether elderly patients benefit from surgery in addition to radiotherapy? In attempting to answer this question, we performed a matched-pair analysis comparing surgery followed by radiotherapy to radiotherapy alone.

PATIENTS AND METHODS

Data from 42 elderly (age > 65 years) patients receiving surgery plus radiotherapy (S + RT) were matched to 84 patients (1:2) receiving radiotherapy alone (RT). Groups were matched for ten potential prognostic factors and compared regarding motor function, local control, and survival. Additional matched-pair analyses were performed for the subgroups of patients receiving direct decompressive surgery plus stabilization of involved vertebrae (DDSS, n = 81) and receiving laminectomy (LE, n = 45).

RESULTS

Improvement of motor function occurred in 21% after S + RT and 24% after RT (p = 0.39). The 1-year local control rates were 81% and 91% (p = 0.44), while the 1-year survival rates were 46% and 39% (p = 0.71). In the matched-pair analysis of patients receiving DDSS, improvement of motor function occurred in 22% after DDSS + RT and 24% after RT alone (p = 0.92). The 1-year local control rates were 95% and 89% (p = 0.62), and the 1-year survival rates were 54% and 43% (p = 0.30). In the matched-pair analysis of patients receiving LE, improvement of motor function occurred in 20% after LE + RT and 23% after RT alone (p = 0.06). The 1-year local control rates were 50% and 92% (p = 0.33). The 1-year survival rates were 32% and 32% (p = 0.55).

CONCLUSION

Elderly patients with MSCC did not benefit from surgery in addition to radiotherapy regarding functional outcome, local control of MSCC, or survival.