Proton therapy: A therapeutic opportunity for aggressive pediatric meningioma.

Meningiomas are an extremely rare histology among pediatric brain tumors, and there is a shortage of literature on their management. Proton therapy is currently used safely and effectively for many types of both pediatric and adult cancer, and its main advantage is the sparing of healthy tissues from radiation, which could translate in the reduction of late side effects. We review the literature on radiotherapy and proton therapy for pediatric meningiomas and report clinical outcomes for two aggressive pediatric meningiomas we treated with protons. Proton therapy might be a safe and effective therapeutic option for this rare subgroup of tumors.

Management of vertebral radiotherapy dose in paediatric patients with cancer: consensus recommendations from the SIOPE radiotherapy working group.

Inhomogeneities in radiotherapy dose distributions covering the vertebrae in children can produce long-term spinal problems, including kyphosis, lordosis, scoliosis, and hypoplasia. In the published literature, many often interrelated variables have been reported to affect the extent of potential radiotherapy damage to the spine. Articles published in the 2D and 3D radiotherapy era instructed radiation oncologists to avoid dose inhomogeneity over growing vertebrae. However, in the present era of highly conformal radiotherapy, steep dose gradients over at-risk structures can be generated and thus less harm is caused to patients. In this report, paediatric radiation oncologists from leading centres in 11 European countries have produced recommendations on how to approach dose coverage for target volumes that are adjacent to vertebrae to minimise the risk of long-term spinal problems. Based on available information, it is advised that homogeneous vertebral radiotherapy doses should be delivered in children who have not yet finished the pubertal growth spurt. If dose fall-off within vertebrae cannot be avoided, acceptable dose gradients for different age groups are detailed here. Vertebral delineation should include all primary ossification centres and growth plates, and therefore include at least the vertebral body and arch. For partial spinal radiotherapy, the number of irradiated vertebrae should be restricted as much as achievable, particularly at the thoracic level in young children (<6 years old). There is a need for multicentre research on vertebral radiotherapy dose distributions for children, but until more valid data become available, these recommendations can provide a basis for daily practice for radiation oncologists who have patients that require vertebral radiotherapy.

Dosimetric comparison of five different techniques for craniospinal irradiation across 15 European centers: analysis on behalf of the SIOP-E-BTG (radiotherapy working group).

PURPOSE: Conventional techniques (3D-CRT) for craniospinal irradiation (CSI) are still widely used. Modern techniques (IMRT, VMAT, TomoTherapy®, proton pencil beam scanning [PBS]) are applied in a limited number of centers. For a 14-year-old patient, we aimed to compare dose distributions of five CSI techniques applied across Europe and generated according to the participating institute protocols, therefore representing daily practice. MATERIAL AND METHODS: A multicenter (n = 15) dosimetric analysis of five different techniques for CSI (3D-CRT, IMRT, VMAT, TomoTherapy®, PBS; 3 centers per technique) was performed using the same patient data, set of delineations and dose prescription (36.0/1.8 Gy). Different treatment plans were optimized based on the same planning target volume margin. All participating institutes returned their best treatment plan applicable in clinic. RESULTS: The modern radiotherapy techniques investigated resulted in superior conformity/homogeneity-indices (CI/HI), particularly in the spinal part of the target (CI: 3D-CRT:0.3 vs. modern:0.6; HI: 3D-CRT:0.2 vs. modern:0.1), and demonstrated a decreased dose to the thyroid, heart, esophagus and pancreas. Dose reductions of >10.0 Gy were observed with PBS compared to modern photon techniques for parotid glands, thyroid and pancreas. Following this technique, a wide range in dosimetry among centers using the same technique was observed (e.g., thyroid mean dose: VMAT: 5.6-24.6 Gy; PBS: 0.3-10.1 Gy). CONCLUSIONS: The investigated modern radiotherapy techniques demonstrate superior dosimetric results compared to 3D-CRT. The lowest mean dose for organs at risk is obtained with proton therapy. However, for a large number of organs ranges in mean doses were wide and overlapping between techniques making it difficult to recommend one radiotherapy technique over another.

Universal field matching in craniospinal irradiation by a background-dose gradient-optimized method.

PURPOSE: The gradient-optimized methods are overcoming the traditional feathering methods to plan field junctions in craniospinal irradiation. In this note, a new gradient-optimized technique, based on the use of a background dose, is described. METHODS: Treatment planning was performed by RayStation (RaySearch Laboratories, Stockholm, Sweden) on the CT scans of a pediatric patient. Both proton (by pencil beam scanning) and photon (by volumetric modulated arc therapy) treatments were planned with three isocenters. An 'in silico' ideal background dose was created first to cover the upper-spinal target and to produce a perfect dose gradient along the upper and lower junction regions. Using it as background, the cranial and the lower-spinal beams were planned by inverse optimization to obtain dose coverage of their relevant targets and of the junction volumes. Finally, the upper-spinal beam was inversely planned after removal of the background dose and with the previously optimized beams switched on. RESULTS: In both proton and photon plans, the optimized cranial and the lower-spinal beams produced a perfect linear gradient in the junction regions, complementary to that produced by the optimized upper-spinal beam. The final dose distributions showed a homogeneous coverage of the targets. DISCUSSION: Our simple technique allowed to obtain high-quality gradients in the junction region. Such technique universally works for photons as well as protons and could be applicable to the TPSs that allow to manage a background dose.

Patterns of practice of image guided particle therapy for cranio-spinal irradiation: A site specific multi-institutional survey of European Particle Therapy Network.

PURPOSE: To investigate the current practice patterns in image-guided particle therapy (IGPT) for cranio-spinal irradiation (CSI). METHODS: A multi-institutional survey was distributed to European particle therapy centres to analyse all aspects of IGPT. Based on the survey results, a Delphi consensus analysis was developed to define minimum requirements and optimal workflow for clinical practice. The centres participating in the institutional survey were invited to join the Delphi process. RESULTS: Eleven centres participated in the survey. Imaging for treatment planning was rather similar among the centres with Computed Tomography (CT) being the main modality. For positioning verification, 2D IGPT was more commonly used than 3D IGPT. Two centres performed routinely imaging for plan adaptation, by the rest ad hoc. Eight centres participated in the Delphi consensus analysis. The full consensus was reached on the use of CT imaging without contrast for treatment planning and the role of magnetic resonance imaging (MRI) in target and organs-at-risk delineation. There was an agreement on the necessity to perform patient position verification and correction before each isocentre. The most important outcome was the clear need for standardization and harmonization of the workflow. CONCLUSION: There were differences in CSI IGPT clinical practice among the European particle therapy centres. Moreover, the optimal workflow as identified by experts was not yet reached. There is a strong need for consensus guidelines. The state-of-the-art imaging technology and protocols need to be implemented into clinical practice to improve the quality of IGPT for CSI.

Clinical practice in European centres treating paediatric posterior fossa tumours with pencil beam scanning proton therapy.

BACKGROUND AND PURPOSE: As no guidelines for pencil beam scanning (PBS) proton therapy (PT) of paediatric posterior fossa (PF) tumours exist to date, this study investigated planning techniques across European PT centres, with special considerations for brainstem and spinal cord sparing. MATERIALS AND METHODS: A survey and a treatment planning comparison were initiated across nineteen European PBS-PT centres treating paediatric patients. The survey assessed all aspects of the treatment chain, including but not limited to delineations, dose constraints and treatment planning. Each centre planned two PF tumour cases for focal irradiation, according to their own clinical practice but based on common delineations. The prescription dose was 54 Gy(RBE) for Case 1 and 59.4 Gy(RBE) for Case 2. For both cases, planning strategies and relevant dose metrics were compared. RESULTS: Seventeen (89 %) centres answered the survey, and sixteen (80 %) participated in the treatment planning comparison. In the survey, thirteen (68 %) centres reported using the European Particle Therapy Network definition for brainstem delineation. In the treatment planning study, while most centres used three beam directions, their configurations varied widely across centres. Large variations were also seen in brainstem doses, with a brainstem near maximum dose (D2%) ranging from 52.7 Gy(RBE) to 55.7 Gy(RBE) (Case 1), and from 56.8 Gy(RBE) to 60.9 Gy(RBE) (Case 2). CONCLUSION: This study assessed the European PBS-PT planning of paediatric PF tumours. Agreement was achieved in e.g. delineation-practice, while wider variations were observed in planning approach and consequently dose to organs at risk. Collaboration between centres is still ongoing, striving towards common guidelines.

Unforeseen cytomegalovirus retinopathy following high dose thiotepa and proton irradiation in a pediatric patient with high-risk medulloblastoma: A case report.

In immunocompetent individuals, cytomegalovirus (CMV) infection is usually mild but may cause severe complications such as retinitis, pneumonitis, and encephalitis in immunocompromised individuals. So far, cases of CMV retinitis in patients with medulloblastoma undergoing chemotherapy and radiotherapy, have not been reported. We herein report the case of a pediatric patient with high-risk medulloblastoma who experienced an unexpected CMV retinopathy and leukoencephalopathy following high dose thiotepa and proton irradiation. The patient underwent a four-course induction therapy (1st cycle: methotrexate and vinorelbine; 2nd cycle: etoposide and hematopoietic stem cells apheresis; 3rd cycle: cyclophosphamide and vinorelbine; 4th cycle: carboplatin and vinorelbine) and then a consolidation phase consisting in high dose thiotepa followed by autologous HSC transplant and proton cranio-spinal irradiation plus boost to the primary tumor site and pituitary site with concomitant vinorelbine. After two months of maintenance treatment with lomustine and vinorelbine, the patient showed complete blindness and leukoencephalopathy. A diagnosis of CMV retinopathy was made and oral valganciclovir was administered. CMV retinopathy was judged to be possibly related to the use of high dose thiotepa worsened by radiotherapy. This case report suggests that in pediatric patients undergoing immunosuppressive chemo-radiotherapy, CMV reactivation should be carefully monitored to prevent serious complications such as retinopathy and visual loss.

Technical challenges in the treatment of mediastinal lymphomas by proton pencil beam scanning and deep inspiration breath-hold.

PURPOSE: To comprehensively describe the treatment of mediastinal lymphoma by pencil beam scanning (PBS) proton therapy. METHODS: Fourteen patients underwent PBS proton treatment in a supine position in deep inspiration breath-hold (DIBH). Three DIBH computed tomography (CT) scans were acquired for each patient to delineate the Internal Target Volume (ITV). Intensity-modulated proton therapy (IMPT) was planned by min-max robust optimization on the ITV, with a 6 mm setup and 3.5% range uncertainties. Robustness analysis was performed and dose coverage was visually inspected on the corresponding voxel-wise minimum map. Layer repainting was set equal to 5 to compensate for cardiac motion. Intra-fraction reproducibility during treatment was assessed by repeated daily DIBH X-ray imaging. Finally, an additional CT was acquired at half treatment to estimate the impact of inter-fraction dosimetric reproducibility. RESULTS: IMPT guaranteed robust mediastinal target coverage and organs-at-risk sparing. However, visual voxel-wise robustness evaluation showed that in five patients a second optimization with focused objectives in the cost-function was necessary to achieve a robust coverage of the target regions at the interface between lungs and soft tissue. In six patients, repainting was not used due to excessive treatment time length and poor patient compliance. Intra-fraction average reproducibility was within 1 mm/1degree. On repeated CT scans, inter-fraction setup errors and/or anatomical changes showed minimal dosimetric differences in CTV coverage. CONCLUSION: IMPT in DIBH is effective and reproducible to treat mediastinal lymphomas. Caution is recommended to guarantee robust dose delivery to high-risk regions at the interface between lungs and soft tissue.

Toxicity and Clinical Results after Proton Therapy for Pediatric Medulloblastoma: A Multi-Centric Retrospective Study.

Medulloblastoma is the most common malignant brain tumor in children. Even if current treatment dramatically improves the prognosis, survivors often develop long-term treatment-related sequelae. The current radiotherapy standard for medulloblastoma is craniospinal irradiation with a boost to the primary tumor site and to any metastatic sites. Proton therapy (PT) has similar efficacy compared to traditional photon-based radiotherapy but might achieve lower toxicity rates. We report on our multi-centric experience with 43 children with medulloblastoma (median age at diagnosis 8.7 years, IQR 6.6, M/F 23/20; 26 high-risk, 14 standard-risk, 3 ex-infant), who received active scanning PT between 2015 and 2021, with a focus on PT-related acute-subacute toxicity, as well as some preliminary data on late toxicity. Most acute toxicities were mild and manageable with supportive therapy. Hematological toxicity was limited, even among HR patients who underwent hematopoietic stem-cell transplantation before PT. Preliminary data on late sequelae were also encouraging, although a longer follow-up is needed.

Usefulness of 18f-FDG PET-CT in Staging, Restaging, and Response Assessment in Pediatric Rhabdomyosarcoma.

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Despite clinical advances, subsets of these patients continue to suffer high morbidity and mortality rates associated with their disease. Following the European guidelines for 18F-FDG PET and PET-CT imaging in pediatric oncology, the routine use of 18F-FDG PET-CT may be useful for patients affected by rhabdomyosarcoma, in staging, in the evaluation of response to therapy, and for restaging/detection of relapse. The European Pediatric Protocols are very old, and for staging and restaging, they recommend only radionuclide bone scan. The 18F-FDG PET-CT exam is listed as an optional investigation prescribed according to local availability and local protocols in the investigations panel required at the end of the treatment. We present two cases highlighting the usefulness of 18F-FDG PET-CT in managing pediatric patients affected by rhabdomyosarcoma, providing some bibliographic references.

An advanced junction concept in pediatric craniospinal irradiation by proton pencil beam scanning.

PURPOSE: To present an advanced junction concept in craniospinal irradiation (CSI) by proton pencil beam scanning (PBS). MATERIALS AND METHODS: In PBS CSI, whole brain irradiation (WBI) is commonly delivered by opposed lateral-beams, whereas spine irradiation is delivered by posterior entrances. Since lateral-beams would cross a large portion of the patient at the shoulder level, the junction between WBI and spine irradiation cannot extend below that level, thus the size of the lateral-beams needs to be limited and the number of required isocenters can increase. To overcome such limitation, a pseudo-junction was introduced below the posterior fossa, to turn in this region the WBI beam arrangement to a single posterior beam pointed at the same isocenter, that was matched to the posterior spinal beam more caudally, below shoulder level, in the true-junction. After assessing robustness of the technique to range and setup uncertainties, twenty-three treated patients were reviewed to estimate the percentage that might benefit of being treated by two instead of three isocenters. RESULTS: Target coverage at the junction levels resulted robust, with D95% > 95% on pseudo-junction and D95% > 90% on the true-junction. By the advanced junction concept, 91% of patients might by treated with only two isocenters, whereas, by the conventional method, 83% of patients required three isocenters. CONCLUSION: With the presented junction concept the number of isocenters can be reduced, with a consequent relevant reduction of treatment time, which is particularly valuable in the management of pediatric patients under anesthesia.

Patterns of proton therapy use in pediatric cancer management in 2016: An international survey.

PURPOSE: To facilitate the initiation of observational studies on late effects of proton therapy in pediatric patients, we report on current patterns of proton therapy use worldwide in patients aged less than 22 years. MATERIALS & METHODS: Fifty-four proton centers treating pediatric patients in 2016 in 11 countries were invited to respond to a survey about the number of patients treated during that year by age group, intent of treatment, delivery technique and tumor types. RESULTS: Among the 40 participating centers (participation rate: 74%), a total of 1,860 patients were treated in 2016 (North America: 1205, Europe: 432, Asia: 223). The numbers of patients per center ranged from 1 to 206 (median: 29). Twenty-four percent of the patients were <5 years of age, and 50% <10 years. More than 30 pediatric tumor types were identified, mainly treated with curative intent: 48% were CNS, 25% extra-cranial sarcomas, 7% neuroblastoma, and 5% hematopoietic tumors. About half of the patients were treated with pencil beam scanning. Treatment patterns were broadly similar across the three continents. CONCLUSION: To our knowledge, this survey provides the first worldwide assessment of proton therapy use for pediatric cancer management. Since previous estimates in the United States and Europe, CNS tumors remain the cancer types most commonly treated with protons in 2016. However, the proportion of extra-cranial tumors is growing worldwide. The typically low numbers of patients treated in each center indicate the need for international research collaborations to assess long-term outcomes of proton therapy in pediatric patients.

SIOPE - Brain tumor group consensus guideline on craniospinal target volume delineation for high-precision radiotherapy.

OBJECTIVE: To develop a consensus guideline for craniospinal target volume (TV) delineation in children and young adults participating in SIOPE studies in the era of high-precision radiotherapy. METHODS AND MATERIALS: During four consensus meetings (Cambridge, Essen, Liverpool, and Marseille), conventional field-based TV has been translated into image-guided high-precision craniospinal TV by a group of expert paediatric radiation oncologists and enhanced by MRI images of liquor distribution. RESULTS: The CTVcranial should include the whole brain, cribriform plate, most inferior part of the temporal lobes, and the pituitary fossa. If the full length of both optic nerves is not included, the dose received by different volumes of optic nerve should be recorded to correlate with future patterns of relapse (no consensus). The CTVcranial should be modified to include the dural cuffs of cranial nerves as they pass through the skull base foramina. Attempts to spare the cochlea by excluding CSF within the internal auditory canal should be avoided. The CTVspinal should include the entire subarachnoid space, including nerve roots laterally. The lower limit of the spinal CTV is at the lower limit of the thecal sac, best visible on MRI scan. There is no need to include sacral root canals in the spinal CTV. CONCLUSION: This consensus guideline has the potential to improve consistency of craniospinal TV delineation in an era of high-precision radiotherapy. This proposal will be incorporated in the RTQA guidelines of future SIOPE-BTG trials using CSI.

Supine craniospinal irradiation in pediatric patients by proton pencil beam scanning.

BACKGROUND AND PURPOSE: Proton therapy is the emerging treatment modality for craniospinal irradiation (CSI) in pediatric patients. Herein, special methods adopted for CSI at proton Therapy Center of Trento by pencil beam scanning (PBS) are comprehensively described. MATERIALS AND METHODS: Twelve pediatric patients were treated by proton PBS using two/three isocenters. Special methods refer to: (i) patient positioning in supine position on immobilization devices crossed by the beams; (ii) planning field-junctions via the ancillary-beam technique; (iii) achieving lens-sparing by three-beams whole-brain-irradiation; (iv) applying a movable-snout and beam-splitting technique to reduce the lateral penumbra. Patient-specific quality assurance (QA) program was performed using two-dimensional ion chamber array and γ-analysis. Daily kilovoltage alignment was performed. RESULTS: PBS allowed to obtain optimal target coverage (mean D98%>98%) with reduced dose to organs-at-risk. Lens sparing was obtained (mean D1∼730cGyE). Reducing lateral penumbra decreased the dose to the kidneys (mean Dmean<600cGyE). After kilovoltage alignment, potential dose deviations in the upper and lower junctions were small (average 0.8% and 1.2% respectively). Due to imperfect modeling of range shifter, QA showed better agreements between measurements and calculations at depths >4cm (mean γ>95%) than at depths<4cm. CONCLUSIONS: The reported methods allowed to effectively perform proton PBS CSI.

Proton radiotherapy for pediatric tumors: review of first clinical results.

Radiation therapy is a part of multidisciplinary management of several childhood cancers. Proton therapy is a new method of irradiation, which uses protons instead of photons. Proton radiation has been used safely and effectively for medulloblastoma, primitive neuro-ectodermal tumors, craniopharyngioma, ependymoma, germ cell intracranial tumors, low-grade glioma, retinoblastoma, rhabdomyosarcoma and other soft tissue sarcomas, Ewing's sarcoma and other bone sarcomas. Moreover, other possible applications are emerging, in particular for lymphoma and neuroblastoma. Although both photon and proton techniques allow similar target volume coverage, the main advantage of proton radiation therapy is to sparing of intermediate-to-low-dose to healthy tissues. This characteristic could translate into clinical reduction of side effects, including a lower risk for secondary cancers. The following review presents the state of the art of proton therapy in the treatment of pediatric malignancies.

Spot-scanning proton radiation therapy for pediatric chordoma and chondrosarcoma: clinical outcome of 26 patients treated at paul scherrer institute.

PURPOSE: To evaluate the clinical results of fractionated spot-scanning proton radiation therapy (PT) in 26 pediatric patients treated at Paul Scherrer Institute for chordoma (CH) or chondrosarcoma (CS) of the skull base or axial skeleton. METHODS AND MATERIALS: Between June 2000 and June 2010, 19 CH and 7 CS patients with tumors originating from the skull base (17) and the axial skeleton (9) were treated with PT. Mean age at the time of PT was 13.2 years. The mean prescribed dose was 74 Gy (relative biological effectiveness [RBE]) for CH and 66 Gy (RBE) for CS, at a dose of 1.8-2.0 Gy (RBE) per fraction. RESULTS: Mean follow-up was 46 months. Actuarial 5-year local control (LC) rates were 81% for CH and 80% for CS. Actuarial 5-year overall survival (OS) was 89% for CH and 75% for CS. Two CH patients had local failures: one is alive with evidence of disease, while the other patient succumbed to local recurrence in the surgical pathway. One CS patient died of local progression of the disease. No high-grade late toxicities were observed. CONCLUSIONS: Spot-scanning PT for pediatric CH and CS patients resulted in excellent clinical outcomes with acceptable rates of late toxicity. Longer follow-up time and larger cohort are needed to fully assess tumor control and late effects of treatment.

Proton radiotherapy for high-risk pediatric neuroblastoma: early outcomes and dose comparison.

PURPOSE: To report the early outcomes for children with high-risk neuroblastoma treated with proton radiotherapy (RT) and to compare the dose distributions for intensity-modulated photon RT (IMRT), three-dimensional conformal proton RT (3D-CPT), and intensity-modulated proton RT to the postoperative tumor bed. METHODS AND MATERIALS: All patients with high-risk (International Neuroblastoma Staging System Stage III or IV) neuroblastoma treated between 2005 and 2010 at our institution were included. All patients received induction chemotherapy, surgical resection of residual disease, high-dose chemotherapy with stem cell rescue, and adjuvant 3D-CPT to the primary tumor sites. The patients were followed with clinical examinations, imaging, and laboratory testing every 6 months to monitor disease control and side effects. IMRT, 3D-CPT, and intensity-modulated proton RT plans were generated and compared for a representative case of adjuvant RT to the primary tumor bed followed by a boost. RESULTS: Nine patients were treated with 3D-CPT. The median age at diagnosis was 2 years (range 10 months to 4 years), and all patients had Stage IV disease. All patients had unfavorable histologic characteristics (poorly differentiated histologic features in 8, N-Myc amplification in 6, and 1p/11q chromosomal abnormalities in 4). The median tumor size at diagnosis was 11.4 cm (range 7-16) in maximal dimension. At a median follow-up of 38 months (range 11-70), there were no local failures. Four patients developed distant failure, and, of these, two died of disease. Acute side effects included Grade 1 skin erythema in 5 patients and Grade 2 anorexia in 2 patients. Although comparable target coverage was achieved with all three modalities, proton therapy achieved substantial normal tissue sparing compared with IMRT. Intensity-modulated proton RT allowed additional sparing of the kidneys, lungs, and heart. CONCLUSIONS: Preliminary outcomes reveal excellent local control with proton therapy for high-risk neuroblastoma, although distant failures continu to occur. Dosimetric comparisons demonstrate the advantage of proton RT compared with IMRT in this setting, allowing more conformal treatment and better normal tissue sparing.

Proton radiotherapy for pediatric Ewing's sarcoma: initial clinical outcomes.

PURPOSE: Proton radiotherapy (PT) has been prescribed similarly to photon radiotherapy to achieve comparable disease control rates at comparable doses. The chief advantage of protons in this setting is to reduce acute and late toxicities by decreasing the amount of normal tissue irradiated. We report the preliminary clinical outcomes including late effects on our pediatric Ewing's sarcoma patients treated with PT at the Francis H. Burr Proton Therapy Center at Massachusetts General Hospital (Boston, MA). METHODS AND MATERIALS: This was a retrospective review of the medical records of 30 children with Ewing's sarcoma who were treated with PT between April 2003 and April 2009. RESULTS: A total of 14 male and 16 female patients with tumors in several anatomic sites were treated with PT at a median age of 10 years. The median dose was 54 Gy (relative biological effectiveness) with a median follow-up of 38.4 months. The 3-year actuarial rates of event-free survival, local control, and overall survival were 60%, 86%, and 89%, respectively. PT was acutely well tolerated, with mostly mild-to-moderate skin reactions. At the time of writing, the only serious late effects have been four hematologic malignancies, which are known risks of topoisomerase and anthracyline exposure. CONCLUSIONS: Proton radiotherapy was well tolerated, with few adverse events. Longer follow-up is needed to more fully assess tumor control and late effects, but the preliminary results are encouraging.

Combined 18F-FDG-PET/CT imaging in radiotherapy target delineation for head-and-neck cancer.

PURPOSE: To evaluate the effect of the use of (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) in radiotherapy target delineation for head-and-neck cancer compared with CT alone. METHODS AND MATERIALS: A total of 38 consecutive patients with head-and-neck cancer were included in this study. The primary tumor sites were as follow: 20 oropharyngeal tumors, 4 laryngeal tumors, 2 hypopharyngeal tumors, 2 paranasal sinuses tumors, 9 nasopharyngeal tumors, and 1 parotid gland tumor. The FDG-PET and CT scans were performed with a dedicated PET/CT scanner in one session and then fused. Subsequently, patients underwent treatment planning CT with intravenous contrast enhancement. The radiation oncologist defined all gross tumor volumes (GTVs) using both the PET/CT and CT scans. RESULTS: In 35 (92%) of 38 cases, the CT-based GTVs were larger than the PET/CT-based GTVs. The average total GTV from the CT and PET/CT scans was 34.54 cm(3) (range, 3.56-109) and 29.38 cm(3) (range, 2.87-95.02), respectively (p < 0.05). Separate analyses of the difference between the CT- and PET/CT-based GTVs of the primary tumor compared with the GTVs of nodal disease were not statistically significant. The comparison between the PET/CT-based and CT-based boost planning target volumes did not show a statistically significant difference. All patients were alive at the end of the follow-up period (range, 3-38 months). CONCLUSION: GTVs, but not planning target volumes, were significantly changed by the implementation of combined PET/CT. Large multicenter studies are needed to ascertain whether combined PET/CT in target delineation can influence the main clinical outcomes.