Aim: The aim of work is to explore a quick, efficient, and effective patient-specific intensity-modulated radiation therapy (IMRT) quality assurance (QA). Materials and Methods: Software tools were developed to extract and analyze the multi-leaf collimator (MLC) leaf positions (LPs) from electronic portal imaging device (EPID) images for Varian C-series machine and TrueBeam, to extract useful data from MLC log file of C-series linear accelerator (LINAC), to extract useful information from the trajectory log binary file of TrueBeam LINAC, to compare LPs derived from EPID images with log file/trajectory log data, and to analyze IMRT treatment files using the MATLAB programming language. The difference in LP determined from the trajectory log and EPID images was proposed for patient-specific QA. Results: It was found that the differences in LP for regular radiation fields generated using stationary leaves are <0.5 mm for all the field sizes while for regular radiation fields generated using the moving leaves are more but <2 mm. The differences in LPs for IMRT field were also determined and found to be <2 mm. Conclusions: The methodology demonstrated can be used for establishing the accuracy of trajectory log data and for independent routine IMRT QA by generating single number like gamma index to indicate pass or fail of an IMRT treatment plan. The QA indices such as numbers of occurrences of ≥2 mm error in LPS are found more than 5% of total number of occurrences; the dosimetric review of planned treatment is advisable.

The hypothesis is that implanted electromagnetic transponders can be used in deep inspiration breath hold RT of lung tumors to improve the accuracy of dose delivery. Patients with primary or metastatic lung tumors were eligible for this prospective IRB-approved protocol under an IDE. Patients had to be able to at minimum hold their breath 5 times for >20 seconds. 3 transponders were implanted by navigational bronchoscopy in ≤2.5mm airways near the tumor. After > 3 days, patients were simulated with a coached DIBH, a free-breathing (FB) and a 4DCT scan for a backup plan. The transponder coordinates, relative to isocenter, were used to gate treatment such that the target had to be within 5 mm of its planned position for dose delivery to occur. For initial setup, a therapist coached the patient to DIBH and adjusted the couch to bring the transponder centroid within 2 mm of the planned position. Patients treated with stereotactic body radiation therapy (SBRT) (n=14) underwent a cone beam-CT (CBCT) in breath-hold position at each treatment. The final setup was determined by a tumor match with the planning scan. An adjustment in the centroid parameters was made if necessary to match the imaging findings. Conventionally fractionated patients (n=4) received a weekly CBCT for tumor match and were on other days set up based on the transponder centroid. All patients received daily orthogonal imaging and were treated in multiple DIBHs. 18 patients were enrolled thus far and 5 have >12 months follow up (median 6.6 months). Only 1/54 transponder was found more peripheral than intended at the time of implantation. No transponder migration or loss was observed. All patients were able to perform reliable DIBH maneuvers throughout treatment. One patient had to interrupt treatment due to a shoulder problem. Another patient had to be instructed to perform chest rather than abdominal breathing to avoid collision with the antenna. CBCTs could be acquired in 1-3 breath-holds. DIBH significantly increased lung volume and decreased PTV volume relative to FB. Lung metrics in DIBH plans were far superior to the FB plans; in 7 patients FB plans could not simultaneously meet the DIBH prescription and satisfy dosimetric constraints. No patients experienced implantation-related toxicity and no unexpected treatment-related toxicities were observed. One patient developed grade 3 pneumonia in the involved right lower lobe 4 months after completion of treatment which was considered to be possibly related to the transponder location. Using implanted transponders to gate DIBH treatments of selected lung tumor patients is clinically feasible and well tolerated. Transponder-guided DIBH resulted in significant benefits in target positioning and monitoring for accurate DIBH treatment delivery and decreased RT dose to organs at risk.

Purpose/Objective(s)Dose-volume tolerances of the spinal cord in spinal stereotactic radiosurgery (SRS) are difficult to define because complication rates for radiation myelitis are required to be very low. Published reports document cases of myelopathy but do not account for the total number of patients treated at given dose-volume combinations. This study reports spinal cord toxicity from single fraction spinal SRS and presents a comprehensive atlas of complication incidence to identify dose-volume predictors of spinal cord toxicity.Materials/MethodsA prospective database of all patients undergoing single fraction spinal SRS at our institution between 2003 and 2010 was retrospectively reviewed for spinal cord toxicity. Spinal cord toxicity was defined as either clinical myelitis or MRI signal changes from pre- to post-treatment scans abutting the treatment site that were not attributable to tumor progression or other causes. Dose-volume histogram (DVH) atlases were created for these endpoints. Complication rates with 95% confidence limits and probabilities that complication rates were <1% for myelitis and <10% for signal changes were determined as functions of dose and absolute volume.ResultsDVH and myelitis information were available for 221 patients treated to 251 sites (46 cervical, 196 thoracic, and 9 lumbar), and post-treatment signal changes were available for 203 patients. Median follow-up was 15.2 months. The median prescribed dose to the PTV was 24 Gy (range 18-24 Gy). There was one case of radiation myelitis (rate r = 0.4%) with accompanying MRI signal changes. There were 6 cases of signal changes without clinical signs or symptoms of myelopathy (r = 3%). All myelitis or signal changes occurred in patients with maximum cord dose >13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1 cc >10.66, 10, 9, and 8 Gy, respectively. Selected cohort statistics are given in the Table.ConclusionsHigh dose spinal SRS has a <1% rate of clinically apparent myelopathy. Asymptomatic spinal cord signal changes are more common (3%). The following dose volume limits minimize the potential for spinal cord toxicity after SRS: maximum cord dose <13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1cc <10.66, 10, 9, and 8 Gy, respectively.AcknowledgmentOral Scientific Abstract 292; TableStatistics for treatments with DVHs passing below the locations (v,d), chosen just below the Myelitis DVHVol v(cc)Dosed(Gy)#comp#totMyelitisprobr < 1%#comp#totSignal Changes99% conflim on r99% conflim on rprobr < 10%013.330640.0680.490550.0791.000.110.660600.0730.470510.0851.000.2100560.0780.450460.0930.990.590450.0950.380360.1170.98180260.1570.250300.1380.96 Open table in a new tab Purpose/Objective(s)Dose-volume tolerances of the spinal cord in spinal stereotactic radiosurgery (SRS) are difficult to define because complication rates for radiation myelitis are required to be very low. Published reports document cases of myelopathy but do not account for the total number of patients treated at given dose-volume combinations. This study reports spinal cord toxicity from single fraction spinal SRS and presents a comprehensive atlas of complication incidence to identify dose-volume predictors of spinal cord toxicity. Dose-volume tolerances of the spinal cord in spinal stereotactic radiosurgery (SRS) are difficult to define because complication rates for radiation myelitis are required to be very low. Published reports document cases of myelopathy but do not account for the total number of patients treated at given dose-volume combinations. This study reports spinal cord toxicity from single fraction spinal SRS and presents a comprehensive atlas of complication incidence to identify dose-volume predictors of spinal cord toxicity. Materials/MethodsA prospective database of all patients undergoing single fraction spinal SRS at our institution between 2003 and 2010 was retrospectively reviewed for spinal cord toxicity. Spinal cord toxicity was defined as either clinical myelitis or MRI signal changes from pre- to post-treatment scans abutting the treatment site that were not attributable to tumor progression or other causes. Dose-volume histogram (DVH) atlases were created for these endpoints. Complication rates with 95% confidence limits and probabilities that complication rates were <1% for myelitis and <10% for signal changes were determined as functions of dose and absolute volume. A prospective database of all patients undergoing single fraction spinal SRS at our institution between 2003 and 2010 was retrospectively reviewed for spinal cord toxicity. Spinal cord toxicity was defined as either clinical myelitis or MRI signal changes from pre- to post-treatment scans abutting the treatment site that were not attributable to tumor progression or other causes. Dose-volume histogram (DVH) atlases were created for these endpoints. Complication rates with 95% confidence limits and probabilities that complication rates were <1% for myelitis and <10% for signal changes were determined as functions of dose and absolute volume. ResultsDVH and myelitis information were available for 221 patients treated to 251 sites (46 cervical, 196 thoracic, and 9 lumbar), and post-treatment signal changes were available for 203 patients. Median follow-up was 15.2 months. The median prescribed dose to the PTV was 24 Gy (range 18-24 Gy). There was one case of radiation myelitis (rate r = 0.4%) with accompanying MRI signal changes. There were 6 cases of signal changes without clinical signs or symptoms of myelopathy (r = 3%). All myelitis or signal changes occurred in patients with maximum cord dose >13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1 cc >10.66, 10, 9, and 8 Gy, respectively. Selected cohort statistics are given in the Table. DVH and myelitis information were available for 221 patients treated to 251 sites (46 cervical, 196 thoracic, and 9 lumbar), and post-treatment signal changes were available for 203 patients. Median follow-up was 15.2 months. The median prescribed dose to the PTV was 24 Gy (range 18-24 Gy). There was one case of radiation myelitis (rate r = 0.4%) with accompanying MRI signal changes. There were 6 cases of signal changes without clinical signs or symptoms of myelopathy (r = 3%). All myelitis or signal changes occurred in patients with maximum cord dose >13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1 cc >10.66, 10, 9, and 8 Gy, respectively. Selected cohort statistics are given in the Table. ConclusionsHigh dose spinal SRS has a <1% rate of clinically apparent myelopathy. Asymptomatic spinal cord signal changes are more common (3%). The following dose volume limits minimize the potential for spinal cord toxicity after SRS: maximum cord dose <13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1cc <10.66, 10, 9, and 8 Gy, respectively. High dose spinal SRS has a <1% rate of clinically apparent myelopathy. Asymptomatic spinal cord signal changes are more common (3%). The following dose volume limits minimize the potential for spinal cord toxicity after SRS: maximum cord dose <13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1cc <10.66, 10, 9, and 8 Gy, respectively.

To report the frequency and magnitude of intrafraction motion (IFM) during treatment with stereotactic body radiation therapy (SBRT) for localized prostate cancer, to quantify the frequency and type of actions necessary to remediate IFM, and to identify risk factors for increased IFM. Forty-six patients treated on a prospective dose escalation protocol using SBRT for localized prostate cancer between 12/09 and 12/11 were analyzed. Twenty-four patients (52%) were low risk group and 23 (48%) were intermediate risk group per the NCCN. Twenty-nine patients (64%) received 3250 cGy and 17 (36%) received 3500 cGy. No patient received androgen deprivation. Simulation was performed with a full bladder after a bowel preparation and placement of rectal and Foley catheters. The CTV was defined as the prostate and seminal vesicles. The PTV margin was 5 mm in all dimensions except 3 mm posteriorly at the rectal interface. Treatment was delivered in 5 fractions given every other day with a full bladder but no bowel preparation nor catheter placement. IFM monitoring was achieved. The action threshold was set at 2 mm in each dimension. Once the action threshold was violated, treatment was held either until the prostate moved back to within range or a patient shift was performed. IFM and the actions taken for its remediation were analyzed using all available data. Univariate analysis was performed to identify clinical predictors for increased intervention for IFM. The mean and median total number of interventions to remediate IFM per fraction was 3.1 (1.2 shifts and 1.9 holds) and 2.8 (1.2 shifts and 1.6 holds). The mean shift was 2.1 mm (range, 0.1 - 10) in the A/P, 2.2 (0.1 - 20) in the R/L, and 1.4 (0.1 - 13) in the S/I dimensions. On univariate analysis, prostate size > 34 cc and treatment time/fraction > 12 minutes were predictive for increased frequency of intervention for IFM. Pre-treatment IPSS, abdominal circumference at isocenter, rectal and bladder volume, and GI/GU toxicity during SBRT were not significant predictors. This is the largest known report quantifying the frequency and magnitude of intrafraction motion management action during SBRT for prostate cancer. Although follow-up is too early to correlate with clinical outcomes, aggressive intrafraction motion management appears necessary to provide adequate localization of the PTV throughout the course of treatment. Patients with prostate glands >34 cc and longer treatment times are at higher risk of requiring interventions for IMF.

Inverse treatment planning, image guidance and reproducible patient immobilization have dramatically improved accuracy and precision enabling safe delivery of high dose stereotactic body radiotherapy (SBRT). Despite these improvements, the anatomic proximity of critical organs at risk (OAR) remains a significant challenge to effective dose delivery to the planning target volume (PTV). Temporary organ displacement (TOD) can be achieved by infusing 100 – 300 cc 10% Omnipaque and normal saline solution into a potential space to increase the distance between target volume and OAR for simulation and treatment. In this study, we sought to compare the pre-TOD and post-TOD dose to the displaced critical OAR to quantify potential dosimetric benefit to the intervention. Six patients were treated with SBRT utilizing TOD for kidney (n = 3) and rectum/bowel (n = 3) displacement, at Memorial Sloan-Kettering Cancer Center between 2/24/2010 and 1/18/2011. The median prescribed dose was 2400 cGy in a single fraction (2000 cGy/1 – 3000 cGy/3). TOD was confirmed by conebeam CT image guidance at the time of treatment. To determine the degree of OAR displacement, pre-TOD CT was fused with the post-TOD planning simulation CT. Pre-TOD and post-TOD OARs were contoured and planned with the same stereotactic dose constraints to OARs while maintaining the same PTV coverage. Dmax, D (5 cc), and Dmean for critical OAR were calculated. Pairwise comparison was performed with 2 tailed t test. The mean TOD distance was 9 mm (7 – 13 mm) for kidney and 40 mm (27 – 54 mm) for rectum/bowel. TOD decreased the Dmax from 2245 cGy (93%) to 1737 cGy (71%), p = 0.135; D (5 cc) from 1884 cGy (78%) to 1226 cGy (50%), p = 0.041; and Dmean from 856 cGy (35%) to 528 cGy (22%) p = 0.049. Specifically, kidney TOD decreased Dmax by 210 cGy (83 – 383 cGy), D (5 cc) by 593 cGy (415 – 870 cGy), Dmean by 444 cGy (248 – 780 cGy); and bowel/rectal TOD decreased Dmax by 657 cGy (267 – 1610 cGy), D (5 cc) by 690 cGy (5 – 1425 cGy), Dmean by 269 cGy (49 – 804 cGy). (Sample sizes were too small to analyze for significance) TOD was well tolerated and there were no complications associated with the procedure. TOD appears to be safe. In every case, the use of TOD reduced the dose to critical OARs by 13 – 28%. Given the concern for increased severe late effects when utilizing high dose SBRT, TOD may represent an important method of minimizing toxicity and facilitating dose escalation.

Respiratory motion makes image guided radiation of liver metastases extremely challenging. Respiratory motion can be completely eliminated through the use of general anesthesia with periodic suspension of ventilation while the patient is treated. Mass movement apneic oxygenation is a well established anesthesia technique which, in a properly monitored clinical environment, safely permits cessation of ventilation for extended periods of time . We hypothesized that high dose single fraction radiation would be safe and effective treatment for liver metastasis if image guided techniques were utilized under the condition of zero respiratory motion. Seven patients with solid tumor liver metastases were treated on an IRB approved protocol. Patients were treated at end expiratory apnea under a general anesthetic. All patients had implanted fiducial markers and underwent contrast enhanced cone beam image guided radiotherapy, receiving 2400 cGy in a single fraction. CT PET simulation was performed for every patient. Each patient was followed with serial CT, PET/CT or MRI imaging every 3 months to assess local control. NCI CTC v 3 was used to score toxicity. The median follow-up is 6 months (2-15) and all patients are available for follow-up. All patients tolerated anesthesia and radiotherapy without complication. All patients demonstrated a transient transaminitis. One patient developed a gastric ulcer (grade 2), and one patient complained of significant fatigue after treatment (grade 3). No other treatment related toxicity has been encountered. Every lesion has had at least a partial response to radiation, and one patient has had a complete response. The mean positional drift during treatment was 1.1 mm (range, 0-3.3 mm). High dose radiation can be safely administered during suspended ventilation under carefully controlled conditions of general anesthesia. Toxicity and tumor control in this preliminary report are favorable. Image guided verification has demonstrated that treatment can be given to liver metastases with a high degree of accuracy when respiratory motion is completely eliminated.

To evaluate outcomes in patients with recurrent paraspinal metastases who were re-irradiated with two different schemes of hypo-fractionated, image-guided, intensity-modulated radiation therapy (IG-IMRT). A retrospective analysis was performed on 89 recurrent paraspinal metastases in 86 patients who were re-irradiated with IG-IMRT in 5 daily fractions to a total dose of either 20Gy (n = 34) or 30Gy (n = 55) from August 2001 to August 2008. Institutional practice was 20Gy prior to 01/01/06 and was escalated to 30Gy subsequently. All patients received previous spine radiation (RT) (median dose 30Gy in 10 fractions). Following IG-IMRT, patients underwent dedicated cross-sectional spine imaging and clinic visits every 3 months. Local recurrence (LR) was defined as radiographic progression of disease within the RT field, and functional outcomes were measured by the American Spinal Injury Association (ASIA) impairment score. Treatment characteristics analyzed included total dose (30Gy vs. 20Gy), performance status, surgical decompression prior to 2nd RT, interval between first RT and first failure, tumor histology, and both volume and D95 of the GTV and PTV. To assess for association between treatment characteristics and local control following IG-IMRT, an actuarial cumulative competing risks analysis was performed with death as a competing risk event. Cox proportional hazards regression models were used to investigate predictors for overall survival (OS). Fisher's exact test was used to evaluate association between variables. With a median follow-up of 12.4 months (range 0.2 - 102), 29/34 and 28/55 have died in the 20Gy and 30Gy cohorts, respectively. At one year, the cumulative incidence of LR was 30% and OS survival was 66%. At the time of last follow-up, the ASIA score was stable or improved in 76% of cases. Of treatment characteristics examined for association with local control, only dose (30Gy vs. 20Gy) was statistically significant (p = 0.02, unadjusted HR 0.46, 95% CI 0.24-0.90). Higher dose was also more likely to be associated with a stable or improved ASIA score (88% with 30Gy vs. 59% with 20Gy, p = 0.004). Dose did not significantly impact OS (p = 0.20). There were minimal acute toxicities and no serious late complications including no myelopathy. There are limited treatment options available for patients whose paraspinal metastases recur following an initial course of RT. Re-irradiation with hypo-fractionated IG-IMRT was effective, and a significant dose response for local control was demonstrated. 30Gy resulted in significantly better local control and functional outcomes compared to 20Gy, without greater toxicity. Further dose escalation with IG-IMRT may be warranted.

Stereotactic body radiotherapy (SBRT) is becoming an emerging treatment option for patients with medically inoperable, early stage non-small cell lung cancer (NSCLC). Reports have shown impressive local control rates of up to 95%. There is little data however on using this technology on patients that present with multiple, bilateral tumors. This report reviews our experience in treating bilateral NSCLC with SBRT. Between 2006 and 2008, 8 patients with bilateral NSCLC were treated using SBRT. Seven patients presented with multiple primary lung cancer and one patient with multiple recurrent lung cancer. All patients had biopsy proven NSCLC in both lesions. PET scans were used to confirm the absence of metastatic or mediastinal disease. One patient showed possible mediastinal disease but was negative on biopsy. The mean radiation prescription dose was 4,000 cGy in 4 fractions to each lesion (range, 2,200-4,800 using 1-4 fractions). A dose of 4,800 cGy in four fractions was attempted for patients, but the dose was lowered in many patients to conform to the constraint of total lung V20 < 12%. The mean age of all patients is 82 years (range, 63-91). There were 4 (50%) males and 4 (50%) females. Histologically, 5 (63%) patients had adenocarcinoma and 3 (37%) had squamous cell carcinoma. At the time of this review all patients are still alive with follow-up of 1-15 months. There was 1 local failure in one lesion that occurred 4 months after completing radiation treatment. There were no cases of acute grade 3 or worse toxicity. One patient experienced late grade 3 pulmonary toxicity. Although longer follow-up is needed, preliminary results show that using SBRT for bilateral multiple tumors can be delivered effectively with an acceptable toxicity profile.

Purpose/Objective: Background: Stereotactic radiosurgery (SRS) utilizing high dose single fraction radiation has been shown to be very effective in the management of intracranial metastases. Image guided techniques were developed to deliver precise high dose intensity modulated radiotherapy using image guided techniques (IG IMRT) in a single fraction to metastatic lesions of the spinal column. Clinical outcomes are presented. Materials/Methods: Methods: Thirty three oligometastatic patients with lesions metastatic to the spinal column were immobilized in a non invasive cradle. No patient had undergone prior treatment to the region of interest, including surgery or prior radiotherapy. IMRT was utilized to provide spinal cord dose-sparing treatment plans (dmax < 1000 cGy) while delivering 1800–2400 cGy to the lesion (median 2100 cGy) in a single fraction set to a single isocenter. Two dimensional and/or three dimensional (cone beam CT) image guided verification was performed immediately before and after the administration of radiation to verify patient positioning and isocenter setup. Each patient was followed every three months with clinical and radiographic (including MRI) assessment. No patient has been lost to follow up. Results: The non invasive cradle coupled with IG IMRT provided set errors ± 1 mm. The median maximum dose (dmax) to the Gross Tumor Volume (GTV) and spinal cord was 2640 cGy and 1042 cGy respectively. The median average cord dose was 434 cGy (range 345–768 cGy). With a median follow up of 7 months (range 3–20 months), 97% of patients have demonstrated durable radiographic control and palliation of presenting symptoms. Overall survival is 100%. No significant treatment related toxicity has been encountered, including no myelopathy or radiculopathy. Conclusions: Conclusion: High dose single fraction IG IMRT is safe and effective. Treatment precision approaches that expected from fixed frame SRS for intracranial metastases. Patients have demonstrated high rates of local control, effective palliation and minimal toxicity, providing proof of principle that tumorcidal doses of radiation can be safely delivered in a single fraction in very close proximity to the spinal cord using image guided treatment techniques.

The proximity of the spinal cord to primary tumors of the spine has limited the dose of radiation that can be safely administered when conventional radiotherapy techniques are used. Precision image guided intensity modulated radiotherapy (IG IMRT) was used to treat these lesions to high dose while respecting spinal cord tolerance. Sixteen patients with primary spine tumors (12 sarcomas, 3 chordomas, 1 other) were treated to a median dose of 7000 cGy in 35 fractions (5580–7020 cGy) by placing them in a noninvasive cradle that provided less than 2mm of set up error. All patients were treated on isocentric linear accelerators. Spinal cord doses were restricted to < 5400 cGy. All patients had gross disease which involved the spinal canal and were not surgical candidates. No patient was lost to follow up, and MRI imaging was obtained every 3–4 months in conjunction with clinical assessment. Kaplan Meir statistics were utilized for actuarial analysis. Median follow up was 21 months (4–42 months). Median age was 55 years. All patients presented with pain, and although all patients reported palliation of pain at the time of first follow up, 71 % of patients continued to report pain relief at the time of last follow up. Of the 6 patients who initially reported weakness, 4 enjoyed normal strength at the time of last follow up. Radiographic freedom from progression was 78 %. No cases of radiation myelopathy or radiculopathy have been encountered. IG IMRT coupled with reliable immobilization can safely treat paraspinal lesions to 70 Gy in multiple fractions without the use of modified linear accelerators. High doses of radiation appear to be effective in the management of tumors traditionally thought to be radioresistant

OBJECTIVE Radioresistant paraspinal tumors may benefit from conformal treatment techniques such as intensity-modulated radiotherapy (IMRT). Local tumor control and long-term palliation for both primary and metastatic tumors may be achieved with IMRT while reducing the risk of spinal cord toxicity associated with conventional radiotherapy techniques. In this article, we report our initial clinical experience in treating 16 paraspinal tumors with IMRT in which the planning target volume was 2 mm or greater from the spinal cord. METHODS IMRT was administered by using a linear accelerator mounted with a multileaf collimator. Two immobilization body frames developed at Memorial Sloan-Kettering Cancer Center were used for patients with and without spinal implants. During a 30-month period, 16 patients underwent IMRT for metastatic and primary tumors. Eleven patients were treated for symptomatic recurrences after undergoing surgery and prior external beam radiotherapy, and one patient was treated after undergoing radiotherapy for a metastatic pancreatic gastrinoma with overlapping ports to the spine. Four patients with primary tumors were treated after primary resection that resulted in positive histological margins. Twelve patients were symptomatic with pain, functional radiculopathy, or both. Tumoral doses were determined on the basis of the relative radiosensitivity of tumors. Patients with metastatic tumors were administered a median tumoral dose of 20 Gy in four to five fractions and a spinal cord maximum dose of 6.0 Gy in addition to the full tolerance dose administered in previous radiation treatments. The primary tumors were delivered a median dose of 70 Gy in 33 to 37 fractions and a spinal cord maximum dose of 16 Gy. The median tumoral volume was 7.8 cm3. RESULTS Of the 15 patients who underwent radiographic follow-up, 13 demonstrated either no interval growth or a reduction in tumor size in a median follow-up period of 12 months (range, 2–23 mo). Two patients, one with a thoracic chondrosarcoma and one with a chordoma, showed tumor progression 1 year after undergoing IMRT. Pain symptoms improved in 11 of 11 patients, and 4 of 4 patients had significant improvement in their functionally significant radiculopathy and/or plexopathy. Pain relief was durable in all patients except the two with tumor progression. No patient showed signs or symptoms of radiation-induced myelopathy, radiculopathy, or plexopathy, including 12 patients with a median follow-up of 18 months. CONCLUSION IMRT was effective for treating pain and improving functional radiculopathy in patients with metastatic and primary tumors. Although long-term tumor control is not established in this study, high-dose tumoral irradiation can be performed without causing radiation myelopathy in more than 1 year of follow-up.

Therapeutic doses of radiation for paraspinal tumors are often limited by the dose-related tolerance of the spinal cord. Intensity-modulated radiation therapy (IMRT) is an advanced form of three-dimensional conformal radiation therapy that provides improved coverage of tumor volumes while reducing the radiation dose to the spinal cord. Computer-controlled multileaf collimation provides high conformality, which makes it feasible to treat tumors of any shape, even those that are wrapped around the spinal cord. The use of a newly developed, noninvasive body frame, the capability of fusing computerized tomography and magnetic resonance images, and on-line portal films provide precise target immobilization and target identification. In this paper the authors discuss their preliminary experience in six cases in which IMRT was used to treat paraspinal lesions in patients who harbored locally recurrent tumors and/or tumors that previously received the maximum doses of radiation that could be tolerated by the spinal cord.

Treatment of retinoblastoma dates back to the first reported (and unsuccessful) enucleation in 1767. Over 200 years later, enucleation is a far more humane and common procedure, yet brachytherapy is often the treatment of choice for small to medium-size tumors offering both function-preservation and good survival-rates (usually employing Co/sup 60/, Ir/sup 192/ and I/sup 125/). Use of Ru/sup 106//Rh/sup 106/(T/sub 1/2 /=1 y; a/spl tilde/Emax=3.54 MeV) for ocular applicators offers the dosimetric advantage of more rapid dose fall-off and reduced risk of cataracts and optic nerve injury. Ru/sup 106//Rh/sup 106/ plaques are therefore suitable for treatment of small tumors, especially in pediatric patients where radiation sensitivity of retinoblastoma is well documented. The authors present dose measurements and Monte-Carlo simulation of the dose distribution for a 14 mm applicator, and compare them with I/sup 125/ plaques. Depth dose and transverse profile distributions were calculated via numerical integration. Beta dose as a function of radial distance from a point source was obtained from the beta dose kernels of Simpkin and Mackie, which are applicable to several beta isotopes and energies. The authors assumed the source was uniformly distributed over the applicator-surface, which was divided into approximately 10/sup 6/ segments. Numerical integration of the kernel was performed over a 1 mm dose-grid. Measurements were performed using both Scanditronix 'stereotactic-field diode' in water phantom, and radiochromic film in water equivalent phantom. Manufacturer specifications are based on measurements with a relatively large detector, and thus have a /spl plusmn/30% uncertainty. In contrast, both measurements as well as the Monte Carlo simulation are in good agreement, and clinically usable.