Jeffrey C. Buchsbaum

Dosimetric Comparison of Involved-Field Three-Dimensional Conformal Photon Radiotherapy and Breast-Sparing Proton Therapy for the Treatment of Hodgkin's Lymphoma in Female Pediatric Patients

PURPOSE To assess the potential reduction in breast dose for young girls with Hodgkins lymphoma (HL) treated with breast-sparing proton therapy (BS-PT) as compared with three-dimensional conformal involved-field photon radiotherapy (3D-CRT). METHODS AND MATERIALS The Clarian Health Cancer Registry was queried for female pediatric patients with the diagnosis of HL who received radiotherapy at the Indiana University Simon Cancer Center during 2006-2009. The original CT simulation images were obtained, and 3D-CRT and BS-PT plans delivering 21 Gy or cobalt gray equivalent (CGE) in 14 fractions were created for each patient. Dose-volume histogram data were collected for both 3D-CRT and BS-PT plans and compared by paired t test for correlated samples. RESULTS The cancer registry provided 10 female patients with Ann Arbor Stage II HL, aged 10-18 years at the time of treatment. Both mean and maximum breast dose were significantly less with BS-PT compared with 3D-CRT: 0.95 CGE vs. 4.70 Gy (p < 0.001) and 21.07 CGE vs. 23.11 Gy (p < 0.001), respectively. The volume of breast receiving 1.0 Gy/CGE and 5.0 Gy/CGE was also significantly less with BS-PT, 194 cm(3) and 93 cm(3), respectively, compared with 790 cm(3) and 360 cm(3) with 3D-CRT (p = 0.009, 0.013). CONCLUSION Breast-sparing proton therapy has the potential to reduce unnecessary breast dose in young girls with HL by as much as 80% relative to involved-field 3D-CRT.

Repetitive Pediatric Anesthesia in a Non-Hospital Setting

PURPOSE Repetitive sedation/anesthesia (S/A) for children receiving fractionated radiation therapy requires induction and recovery daily for several weeks. In the vast majority of cases, this is accomplished in an academic center with direct access to pediatric faculty and facilities in case of an emergency. Proton radiation therapy centers are more frequently free-standing facilities at some distance from specialized pediatric care. This poses a potential dilemma in the case of children requiring anesthesia. METHODS AND MATERIALS The records of the Indiana University Health Proton Therapy Center were reviewed for patients requiring anesthesia during proton beam therapy (PBT) between June 1, 2008, and April 12, 2012. RESULTS A total of 138 children received daily anesthesia during this period. A median of 30 fractions (range, 1-49) was delivered over a median of 43 days (range, 1-74) for a total of 4045 sedation/anesthesia procedures. Three events (0.0074%) occurred, 1 fall from a gurney during anesthesia recovery and 2 aspiration events requiring emergency department evaluation. All 3 children did well. One aspiration patient needed admission to the hospital and mechanical ventilation support. The other patient returned the next day for treatment without issue. The patient who fell was not injured. No patient required cessation of therapy. CONCLUSIONS This is the largest reported series of repetitive pediatric anesthesia in radiation therapy, and the only available data from the proton environment. Strict adherence to rigorous protocols and a well-trained team can safely deliver daily sedation/anesthesia in free-standing proton centers.

Range modulation in proton therapy planning: a simple method for mitigating effects of increased relative biological effectiveness at the end-of-range of clinical proton beams

BackgroundThe increase in relative biological effectiveness (RBE) of proton beams at the distal edge of the spread out Bragg peak (SOBP) is a well-known phenomenon that is difficult to quantify accurately in vivo. For purposes of treatment planning, disallowing the distal SOBP to fall within vulnerable tissues hampers sparing to the extent possible with proton beam therapy (PBT). We propose the distal RBE uncertainty may be straightforwardly mitigated with a technique we call “range modulation”. With range modulation, the distal falloff is smeared, reducing both the dose and average RBE over the terminal few millimeters of the SOBP.MethodsOne patient plan was selected to serve as an example for direct comparison of image-guided radiotherapy plans using non-range modulation PBT (NRMPBT), and range-modulation PBT (RMPBT). An additional plan using RMPBT was created to represent a re-treatment scenario (RMPBTrt) using a vertex beam. Planning statistics regarding dose, volume of the planning targets, and color images of the plans are shown.ResultsThe three plans generated for this patient reveal that in all cases dosimetric and device manufacturing advantages are able to be achieved using RMPBT. Organ at risk (OAR) doses to critical structures such as the cochleae, optic apparatus, hypothalamus, and temporal lobes can be selectively spared using this method. Concerns about the location of the RBE that did significantly impact beam selection and treatment planning no longer have the same impact on the process, allowing these structures to be spared dose and subsequent associated issues.ConclusionsThis present study has illustrated that RMPBT can improve OAR sparing while giving equivalent coverage to target volumes relative to traditional PBT methods while avoiding the increased RBE at the end of the beam. It has proven easy to design and implement and robust in our planning process. The method underscores the need to optimize treatment plans in PBT for both traditional energy dose in gray (Gy) and biologic dose (RBE).

Definitive treatment of leptomeningeal spinal metastases in children

Uniquely in children, the existence of leptomeningeal spinal metastases does not confer a uniformly grave prognosis. Although the radiation tolerance of the spinal cord is of significant concern in these cases, the chemo‐ and radiosensitivity of these lesions argues for an aggressive approach where possible.

Supine proton beam craniospinal radiotherapy using a novel tabletop adapter

To develop a device that allows supine craniospinal proton and photon therapy to the vast majority of proton and photon facilities currently experiencing limitations as a result of couch design issues. Plywood and carbon fiber were used for the development of a prototype unit. Once this was found to be satisfactory after all design issues were addressed, computer-assisted design (CAD) was used and carbon fiber tables were built to our specifications at a local manufacturer of military and racing car carbon fiber parts. Clinic-driven design was done using real-time team discussion for a prototype design. A local machinist was able to construct a prototype unit for us in <2 weeks after the start of our project. Once the prototype had been used successfully for several months and all development issues were addressed, a custom carbon fiber design was developed in coordination with a carbon fiber manufacturer in partnership. CAD methods were used to design the units to allow oblique fields from head to thigh on patients up to 200 cm in height. Two custom-designed carbon fiber craniospinal tabletop designs now exist: one long and one short. Four are in successful use in our facility. Their weight tolerance is greater than that of our robot table joint (164 kg). The long unit allows for working with taller patients and can be converted into a short unit as needed. An affordable, practical means of doing supine craniospinal therapy with protons or photons can be used in most locations via the use of these devices. This is important because proton therapy provides a much lower integral dose than all other therapy methods for these patients and the supine position is easier for patients to tolerate and for anesthesia delivery. These units have been successfully used for adult and pediatric supine craniospinal therapy, proton therapy using oblique beams to the low pelvis, treatment of various spine tumors, and breast-sparing Hodgkins therapy.

Overcoming the learning curve in supine pediatric proton craniospinal irradiation.

THE PROBLEM Craniospinal irradiation (CSI) is a critically important technique in the treatment of several malignancies, in that coverage of the craniospinal axis contributes to cure in both the definitive [1,2] and salvage [3] settings. Although SI is traditionally described using hotons, theadventofnewprotonceners has opened opportunities for more atients to be treated with proton CSI. Most sources describe CSI perormed in the prone position [4,5]. upine CSI (SCSI) is preferable if ossible because it allows a uniform ource-to-skin distance for the spial field and is technically challengng [6]. Our proton center did not erform craniospinal therapy rouinely before July 2010, and we ished to offer CSI to our patients sing a supine technique. In August 2010, we instituted a peiatric SCSI program. This was in conunction with the development of a roton-specifictabletopattachmentfor atient immobilization [7]. Since that ime, 23 patients have been treated ithSCSI.For thefirst severalpatients, elected staff members received specialzed training and initially performed all CSI procedures, and our implemenation protocol required nursing and adiation oncologist presence in the reatment room for all setup maneuers. Over time, these policies were odified to allow all therapy staff embers to become certified to use the echnique, and physician involvement snowrequiredonlyfor imageapproval efore treatment of each field. Using the data from the Indiana niversity cyclotron control system, nd records of the IU Health Proton herapy Center, it is possible to assess

The Pediatric Proton Consortium Registry: A Multi-institutional Collaboration in U.S. Proton Centers

Abstract Purpose: Survival rates for children with cancer have increased dramatically over several decades, revealing a host of late effects associated with treatment. Proton therapy promises to reduce late effects because of its ability to better localize dose, but the question is by how much? Pediatric health outcomes must be prospectively studied to determine what the margin of benefit is. To facilitate such research, a consortium consisting of pediatric investigators from the US was formed. The goals of the Pediatric Proton Consortium Registry (PPCR) study are to create a comprehensive database of pediatric patients treated with proton radiation therapy in the United States to be used and accessed by participating institutions, to describe the patterns of follow-up at proton facilities, and to describe the acute and late effects in the children treated with proton therapy. Patients and Methods: REDCap is the platform for the ∼600-field database which was designed to capture baseline, treatment, and fo...

Reirradiation with Proton Therapy for Recurrent Gliomas

Abstract Purpose: To evaluate the effectiveness and tolerance of reirradiation with proton therapy (PT) in patients with recurrent gliomas. Patients and Methods: Between 2005 and 2012, 20 patients with recurrent gliomas were irradiated with proton therapy at the Indiana University Health Proton Therapy Center. Three had low-grade gliomas (LGGs, World Health Organization grade I/II), 4 had grade III, and 13 had glioblastoma (GBM, World Health Organization grade IV). The median time interval between initial radiation and reirradiation was 17.4, 62.8, and 15.3 months for LGG, grade III gliomas, and GBMs, respectively. The median dose delivered was 30, 59.4, and 54 Gy (RBE) for the low-grade, grade III, and grade IV tumors, respectively. Results: The median follow-up time from reirradiation was 8.3 months (range, 1.4 to 25.3), and 30% of the patients were alive at time of follow-up evaluation. Only 1 patient with an LGG had died. Median overall survival (OS) from the time of the original pathologic diagnosis ...

Technique for sparing previously irradiated critical normal structures in salvage proton craniospinal irradiation

BackgroundCranial reirradiation is clinically appropriate in some cases but cumulative radiation dose to critical normal structures remains a practical concern. The authors developed a simple technique in 3D conformal proton craniospinal irradiation (CSI) to block organs at risk (OAR) while minimizing underdosing of adjacent target brain tissue.MethodsTwo clinical cases illustrate the use of proton therapy to provide salvage CSI when a previously irradiated OAR required sparing from additional radiation dose. The prior radiation plan was coregistered to the treatment planning CT to create a planning organ at risk volume (PRV) around the OAR. Right and left lateral cranial whole brain proton apertures were created with a small block over the PRV. Then right and left lateral “inverse apertures” were generated, creating an aperture opening in the shape of the area previously blocked and blocking the area previously open. The inverse aperture opening was made one millimeter smaller than the original block to minimize the risk of dose overlap. The inverse apertures were used to irradiate the target volume lateral to the PRV, selecting a proton beam range to abut the 50% isodose line against either lateral edge of the PRV. Together, the 4 cranial proton fields created a region of complete dose avoidance around the OAR. Comparative photon treatment plans were generated with opposed lateral X-ray fields with custom blocks and coplanar intensity modulated radiation therapy optimized to avoid the PRV. Cumulative dose volume histograms were evaluated.ResultsTreatment plans were developed and successfully implemented to provide sparing of previously irradiated critical normal structures while treating target brain lateral to these structures. The absence of dose overlapping during irradiation through the inverse apertures was confirmed by film. Compared to the lateral X-ray and IMRT treatment plans, the proton CSI technique improved coverage of target brain tissue while providing the least additional radiation dose to the previously irradiated OAR.ConclusionsProton craniospinal irradiation can be adapted to provide complete sparing of previously irradiated OARs. This technique may extend the option of reirradiation to patients otherwise deemed ineligible for further radiotherapy due to prior dose to critical normal structures.

Dosimetric comparison between proton and photon beams in the moving gap region in cranio-spinal irradiation (CSI)

Abstract Purpose. To investigate the moving gap region dosimetry in proton beam cranio-spinal irradiation (CSI) to provide optimal dose uniformity across the treatment volume. Material and methods. Proton beams of ranges 11.6 cm and 16 cm are used for the spine and the brain fields, respectively. Beam profiles for a 30 cm snout are first matched at the 50% level (hot match) on the computer. Feathering is simulated by shifting the dose profiles by a known distance two successive times to simulate a 2 × feathering scheme. The process is repeated for 2 mm and 4 mm gaps. Similar procedures are used to determine the dose profiles in the moving gap for a series of gap widths, 0–10 mm, and feathering step sizes, 4–10 mm, for a Varian iX 6MV beam. The proton and photon dose profiles in the moving gap region are compared. Results. The dose profiles in the moving gap exhibit valleys and peaks in both proton and photon beam CSI. The dose in the moving gap for protons is around 100% or higher for 0 mm gap, for both 5 and 10 mm feathering step sizes. When the field gap is comparable or larger than the penumbra, dose minima as low as 66% is obtained. The dosimetric characteristics for 6 MV photon beams can be made similar to those of the protons by appropriately combining gap width and feathering step size. Conclusion. The dose in the moving gap region is determined by the lateral penumbras, the width of the gap and the feathering step size. The dose decreases with increasing gap width or decreasing feathering step size. The dosimetric characteristics are similar for photon and proton beams. However, proton CSI has virtually no exit dose and is beneficial for pediatric patients, whereas with photon beams the whole lung and abdomen receive non-negligible exit dose.