Clinical Outcomes After Reirradiation of Paraspinal Tumors

Spinal Reirradiation-Mediated Myelopathy: A Systematic Review and Meta-Analysis

Reirradiation of the spine is carried out in 42% of patients who do not respond to treatment or have recurrent pain. However, there are few studies and data on the effect of reirradiation of the spine and the occurrence of acute and chronic side-effects caused by reirradiation, such as myelopathy, in these patients. This meta-analysis aimed to determine the safe dose in terms of biological effective dose (BED), cumulative dose and dose interval between BED1 and BED2 to decrease or prevent myelopathy and pain control in patients undergoing radiation therapy in the spinal cord. A search was carried out using EMBASE, MEDLINE, PUBMED, Google Scholar, Cochrane Collaboration library electronic databases, Magiran, and SID from 2000 to 2022 to recognise qualified studies. In total, 17 primary studies were applied to estimate the pooled effect size. The random effects model showed that the pooled BED in the first stage, the BED in the second stage and the cumulative BED1 and BED2 were estimated at 77.63, 58.35 and 115.34 Gy, respectively. Studies reported on dose interval. The results of a random effects model showed that the pooled interval was estimated at 13.86 months. The meta-analysis revealed that using appropriate BED1 and/or BED2 in a safe interval between the first and second phases of treatment can have an influential role in preventing or reducing the effects of myelopathy and regional control pain in spinal reirradiation.

Stereotactic Body Radiation Therapy for Spinal Metastases: Tumor Control Probability Analyses and Recommended Reporting Standards

PURPOSE

We sought to investigate the tumor control probability (TCP) of spinal metastases treated with stereotactic body radiation therapy (SBRT) in 1 to 5 fractions.

METHODS AND MATERIALS

PubMed-indexed articles from 1995 to 2018 were eligible for data extraction if they contained SBRT dosimetric details correlated with actuarial 2-year local tumor control rates. Logistic dose-response models of collected data were compared in terms of physical dose and 3-fraction equivalent dose.

RESULTS

Data were extracted from 24 articles with 2619 spinal metastases. Physical dose TCP modeling of 2-year local tumor control from the single-fraction data were compared with data from 2 to 5 fractions, resulting in an estimated α/β = 6 Gy, and this was used to pool data. Acknowledging the uncertainty intrinsic to the data extraction and modeling process, the 90% TCP corresponded to 20 Gy in 1 fraction, 28 Gy in 2 fractions, 33 Gy in 3 fractions, and (with extrapolation) 40 Gy in 5 fractions. The estimated TCP for common fractionation schemes was 82% at 18 Gy, 90% for 20 Gy, and 96% for 24 Gy in a single fraction, 82% for 24 Gy in 2 fractions, and 78% for 27 Gy in 3 fractions.

CONCLUSIONS

Spinal SBRT with the most common fractionation schemes yields 2-year estimates of local control of 82% to 96%. Given the heterogeneity in the tumor control estimates extracted from the literature, with variability in reporting of dosimetry data and the definition of and statistical methods of reporting tumor control, care should be taken interpreting the resultant model-based estimates. Depending on the clinical intent, the improved TCP with higher dose regimens should be weighed against the potential risks for greater toxicity. We encourage future reports to provide full dosimetric data correlated with tumor local control to allow future efforts of modeling pooled data.

DTI and pathological changes in a rabbit model of radiation injury to the spinal cord after 125I radioactive seed implantation

Excessive radiation exposure may lead to edema of the spinal cord and deterioration of the nervous system. Magnetic resonance imaging can be used to judge and assess the extent of edema and to evaluate pathological changes and thus may be used for the evaluation of spinal cord injuries caused by radiation therapy. Radioactive ¹²⁵I seeds to irradiate 90% of the spinal cord tissue at doses of 40–100 Gy (D90) were implanted in rabbits at T₁₀ to induce radiation injury, and we evaluated their safety for use in the spinal cord. Diffusion tensor imaging showed that with increased D90, the apparent diffusion coefficient and fractional anisotropy values were increased. Moreover, pathological damage of neurons and microvessels in the gray matter and white matter was aggravated. At 2 months after implantation, obvious pathological injury was visible in the spinal cords of each group. Magnetic resonance diffusion tensor imaging revealed the radiation injury to the spinal cord, and we quantified the degree of spinal cord injury through apparent diffusion coefficient and fractional anisotropy.

CT-Guided 125I Seed Interstitial Brachytherapy as a Salvage Treatment for Recurrent Spinal Metastases after External Beam Radiotherapy

The aim of this study is to evaluate the feasibility, safety, and clinical efficacy of CT-guided ¹²⁵I seed interstitial brachytherapy in patients with recurrent spinal metastases after external beam radiotherapy (EBRT). Between August 2003 and September 2015, 26 spinal metastatic lesions (24 patients) were reirradiated by this salvage therapy modality. Treatment for all patients was preplanned using a three-dimensional treatment planning system 3-5 days before ¹²⁵I seed interstitial brachytherapy; dosimetry verification was performed immediately after seed implantation. Median actual D₉₀ was 99 Gy (range, 90-176), and spinal cord median D_max was 39 Gy (range, 6-110). Median local control (LC) was 12 months (95% CI: 7.0-17.0). The 6- and 12-month LC rates were 52% and 40%, respectively. Median overall survival (OS) was 11 months (95% CI: 7.7-14.3); 6-month and 1-, 2-, and 3-year OS rates were 65%, 37%, 14%, and 9%, respectively. Pain-free survival ranged from 2 to 42 months (median, 6; 95% CI: 4.6-7.4). Treatment was well-tolerated, with no radiation-induced vertebral compression fractures or myelopathy reported. Reirradiation with CT-guided ¹²⁵I seed interstitial brachytherapy appears to be feasible, safe, and effective as pain relief or salvage treatment for patients with recurrent spinal metastases after EBRT.

Reirradiation of spinal metastases with intensity-modulated radiation therapy: an analysis of 23 patients

This study aimed to evaluate the efficacy and safety of reirradiation with intensity-modulated radiation therapy (IMRT) for spinal metastases. We retrospectively analyzed 23 patients with spinal metastases who underwent IMRT reirradiation between December 2006 and July 2013. We evaluated the spinal radiation doses during the first and second radiation therapy courses, the interval between the courses, and the clinical outcomes after reirradiation, including skeletal-related events, local control rates (LCRs), overall survival (OS), and toxicities. The median time from the first irradiation to reirradiation was 13 months (range, 2-75 months). The median reirradiation dose delivered to 90% of the planning target volume was 24.5 Gy in 5 fractions (range, 14.7-50 Gy in 3-25 fractions). Nineteen patients experienced pain at reirradiation, and 15 of these attained pain relief. Two of the three patients with paresis in the upper or lower extremities upon initiation of reirradiation demonstrated improvement. Local progression was identified in four patients. The median time to local progression was 37 months. The 1- and 2-year LCRs after reirradiation were 88% and 75%, respectively. The 1- and 2-year OS rates after reirradiation were 45% and 20%, respectively, with a median OS of 12 months. No late toxicities occurred. In conclusion, spinal metastasis reirradiation using IMRT appears safe; pain relief and paresis improvement and/or prevention can be expected, along with a reduced risk of radiation-induced toxicity, especially in the spinal cord.

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.

The role of stereotactic body radiotherapy and stereotactic radiosurgery in the re-irradiation of metastatic spinal tumors

Stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) are advanced radiotherapy delivery techniques that allow for the delivery of high-dose per fraction radiation. Advances in imaging technology and intensity modulation have allowed SRS and SBRT to be used for the treatment of tumors in close proximity to the spinal cord and cauda equina, in particular spinal metastases. While the initial treatment of spinal metastases is often conventional palliative radiotherapy, treatment failure is not uncommon, and conventional re-irradiation may not be feasible due to spinal cord tolerance. SBRT and SRS have emerged as important techniques for the treatment of spinal metastases in the proximity of previously irradiated spinal cord. Here we review the current data on the use of SBRT and SRS spinal re-irradiation, and future directions for these important treatment modalities.

The emerging role of IG-IMRT for palliative radiotherapy: a single-institution experience

Many modern radiotherapy centers now have image-guided intensity-modulated radiotherapy (ig-imrt) tools available for clinical use, and the technique offers many options for patients requiring palliative radiotherapy. We describe a single-institution experience with ig-imrt for short-course palliative radiotherapy, highlighting the unique situations in which the technique can be most effectively used.

Workshop report: A practical approach and general principles of re-irradiation for in-field cancer recurrence

In-field cancer recurrence after previous adjuvant or radical radiotherapy presents particularly challenging clinical issues to the oncologists. A Canadian pattern of practice survey showed a wide range of approaches in treatment intent, planning and dose fractionation. A workshop on re-irradiation was conducted at the 2009 Canadian Association of Radiation Oncology annual scientific meeting, under the guidance of the Symptom Control Committee, in an effort to promote a uniform approach among radiation oncologists in their approach to re-irradiation. The workshop has made various recommendations in an effort to bring consistency among radiation oncologists across Canada to their approach towards re-irradiation.

Impact of dose on local failure rates after image-guided reirradiation of recurrent paraspinal metastases

PURPOSE

To examine the impact of dose on local failure (LF) rates in the re-treatment of recurrent paraspinal metastases with image-guided intensity-modulated radiotherapy (IG-IMRT).

METHODS AND MATERIALS

The records of patients with in-field recurrence after previous spine radiation (median dose, 30 Gy) who received salvage IG-IMRT with either five 4-Gy (20-Gy group, n = 42) or five 6-Gy (30-Gy group, n = 55) daily fractions between January 2003 and August 2008 were reviewed. Institutional practice was 20 Gy before April 2006, when it changed to 30 Gy. A total of 47 cases (48%) were treated adjuvantly, after surgery to decompress epidural disease. LF after IG-IMRT was defined radiographically.

RESULTS

The median follow-up was 12.1 months (range, 0.2-63.6 months). The 1-year cumulative incidences of LF after 20 Gy and 30 Gy IG-IMRT were 45% and 26%, respectively (p = 0.04). Of all treatment characteristics examined (20-Gy vs. 30-Gy dose group, dose to 95% of the planned and gross target volume, tumor size, histology, receipt of surgery, and interval between first and second radiation), only dose group had a significant impact on actuarial LF incidence (p = 0.04; unadjusted HR, 0.51; 95% CI, 0.27-0.96). There was no incidence of myelopathy.

CONCLUSIONS

A significant decrease in LF after IG-IMRT with five 6-Gy fractions compared with five 4-Gy fractions was observed without increased risk of myelopathy. Until prospective data comparing stereotactic hypofractionated and single-fraction regimens become available, when reirradiating recurrent paraspinal metastases with IG-IMRT, administration of five 6-Gy daily fractions is reasonable.

Rapid palliative radiotherapy: comparing IG-IMRT with more conventional approaches

Purpose: To assess the efficiency of an integrated imaging, planning, and treatment delivery system to provide image-guided intensity-modulated radiotherapy (IG-IMRT) for patients requiring palliative radiotherapy (PRT).

Methods: Between December 2006 and May 2008, 28 patients requiring urgent PRT were selected to undergo single-session megavoltage computed tomography (MV-CT) simulation, IMRT treatment planning, position verification and delivery of the first faction of radiotherapy on a helical Tomotherapy® unit. The time required to complete each step was recorded and compared to our standard approach of using either fluoroscopic or CT-based simulation, simplified treatment planning and delivery on a megavoltage unit.

Results: Twenty-eight patients were treated with our integrated IG-IMRT protocol. The median age was 72 years, with 61% men and 39% women. The indications for PRT were: painful bone and soft tissue metastasis (75%); bleeding lesions (14%); and other reasons (11%). The areas treated included the following: hip and/or pelvis (42%); spine (36%); and other areas (21%). The most commonly used dose prescription was 20 Gy in five fractions. Average times for the integrated IG-IMRT processes were as follows: image acquisition, 15 minutes; target delineation, 16 minutes; IMRT treatment planning, 9 minutes; treatment position verification, 10 minutes; and treatment delivery, 12 minutes. The average total time was 62 minutes compared to 66 minutes and 81 minutes for fluoroscopic and CT-simulation-based approaches, respectively. The IMRT dose distributions were also superior to simpler plans.

Conclusions: PRT with an integrated IG-IMRT approach is efficient and convenient for patients, and has potential for future applications such as single-fraction radiotherapy.

Low rate of thoracic toxicity in palliative paraspinal single-fraction stereotactic body radiation therapy

BACKGROUND

There has been an increase in the utilization of single-fraction stereotactic body radiation therapy (SBRT) to treat thoracic structures, but there have been few reports describing toxicity outcomes with this treatment.

METHODS

We evaluated 119 sites (114 patients) with no prior history of thoracic radiation were treated from 10/1/2003 to 10/27/2008 with single-fraction SBRT to thoracic structures. The median dose to the gross tumor volume was 2400 cGy (range 1800-2400 cGy), as was the median dose to the planning target volume (range 1600-2400 cGy). A detailed review of thoracic toxicities was performed to include pneumonitis or Grade 2 or higher esophageal and bronchial toxicity. In addition, we retrospectively contoured the esophagus and bronchus of 48 patients treated in 2004-2005, prior to the establishment of dose constraints to determine the range of doses that these structures received.

RESULTS

Of the contoured patients, the median dose to the hottest 1cc (D1cc) of the esophagus was 1250 cGy (range 158-2572 cGy). The median bronchial D1cc was 1101 cGy (range 260-2211 cGy). At a median follow-up of 11.6 months, there were seven Grade 2 or higher esophageal toxicities, including one Grade 3 and one Grade 4 toxicities. There were two bronchial toxicities, one Grade 2 and one Grade 3. There were no cases of pneumonitis.

CONCLUSIONS

High-dose single-fraction SBRT is well tolerated to the thoracic region, with most patients tolerating high doses to central structures without significant toxicity.

A REVIEW OF IMAGE-GUIDED INTENSITY-MODULATED RADIOTHERAPY FOR SPINAL TUMORS

OBJECTIVE

A new paradigm for the radiotherapeutic management of paraspinal tumors has emerged. Intensity-modulated radiotherapy (IMRT) has gained wide acceptance as a way of delivering highly conformal radiation to tumors. IMRT is capable of sparing sensitive structures such as the spinal cord of high-dose radiation even if only several millimeters away from the tumor. Image-guided treatment tools such as cone beam computed tomography coupled with IMRT have reduced treatment errors associated with traditional radiotherapy, making highly accurate and conformal treatment feasible.

METHODS

This review discusses the physics of image-guided radiotherapy, including immobilization, the radiobiological implications of hypofractionation, as well as outcomes. Image-guided technology has improved the accuracy of IMRT to within 2 mm of error. Thus, the marriage of image guidance with IMRT (IG IMRT) has allowed the safe treatment of spinal tumors to a high dose without increasing the risk of radiation-related toxicity. With the use of near real-time image-guided verification, very-high-dose radiation has been given for tumors in standard fractionation, hypofractionated, and single fraction schedules to doses beyond levels traditionally believed safe in terms of spinal cord tolerance.

RESULTS

Clinical results, in terms of treatment-related toxicity and tumor control, have been very favorable. With follow-up periods extending beyond 30 months, tumor control rates with single fraction IG IMRT (1800–2400 cGy) are in excess of 90%, regardless of histology, and without serious sequelae such as radiation myelopathy. Patients also report correspondingly high rates of palliation. Excellent results, both in terms of tumor control and minimal toxicity, have been consistently reported in the literature.

CONCLUSION

IG IMRT represents a significant technological advance. Paraspinal IG IMRT is proof of principle, making it possible to give very-high-dose radiation within close proximity to the spinal cord. By reducing treatment-related uncertainties, margins around tumors can be shortened, thereby reducing the volume of normal tissue that must be irradiated to tumoricidal doses, reducing the likelihood of toxicity. Similarly, higher doses of radiation can be administered safely, improving the likelihood of eradication. Dose escalation can be done to increase the likelihood of tumor cell kill without increasing the dose given to nearby sensitive structures.