-
Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer 05/2013; 8(5):e38-40. · 4.55 Impact Factor
-
Acta oncologica (Stockholm, Sweden) 04/2013; 52(3):592-4. · 2.27 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Background. Concurrent chemoradiotherapy (CRT) is the standard of care in patients with limited-stage small cell lung cancer (SCLC). Treatment with conventional x-ray therapy (XRT) is associated with high toxicity rates, particularly acute grade 3+ esophagitis and pneumonitis. We present outcomes for the first known series of limited-stage SCLC patients treated with proton therapy and a dosimetric comparison of lung and esophageal doses with intensity-modulated radiation therapy (IMRT). Material and methods. Six patients were treated: five concurrently and one sequentially. Five patients received 60-66 CGE in 30-34 fractions once daily and one patient received 45 CGE in 30 fractions twice daily. All six patients received prophylactic cranial irradiation. Common Terminology Criteria for Adverse Events, v3.0, was used to grade toxicity. IMRT plans were also generated and compared with proton plans. Results. The median follow-up was 12.0 months. The one-year overall and progression-free survival rates were 83% and 66%, respectively. There were no cases of acute grade 3+ esophagitis or acute grade 2+ pneumonitis, and no other acute grade 3+ non-hematological toxicities were seen. One patient with a history of pulmonary fibrosis and atrial fibrillation developed worsening symptoms four months after treatment requiring oxygen. Three patients died: two of progressive disease and one after a fall; the latter patient was disease-free at 36 months after treatment. Another patient recurred and is alive, while two patients remain disease-free at 12 months of follow-up. Proton therapy proved superior to IMRT across all esophageal and lung dose volume points. Conclusion. In this small series of SCLC patients treated with proton therapy with radical intent, treatment was well tolerated with no cases of acute grade 3+ esophagitis or acute grade 2+ pneumonitis. Dosimetric comparison showed better sparing of lung and esophagus with proton therapy. Proton therapy merits further investigation as a method of reducing the toxicity of CRT.
Acta oncologica (Stockholm, Sweden) 02/2013; · 2.27 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Compare dose distributions for pediatric patients with ependymoma calculated using a Monte Carlo (MC) system and a clinical treatment planning system (TPS).
Plans from ten pediatric patients with ependymoma treated using double scatter proton therapy were exported from the TPS and calculated in our MC system. A field by field comparison of the distal edge (80% and 20%), distal fall off (80% to 20%), field width (50% to 50%), and penumbra (80% to 20%) were examined. In addition, the target dose for the full plan was compared.
For the 32 fields from the 10 patients, the average differences of distal edge at 80% and 20% on central axis between MC and TPS are -1.9 ± 1.7 mm (p < 0.001) and -0.6 ± 2.3 mm (p = 0.13), respectively. Excluding the fields that ranged out in bone or an air cavity, the 80% difference was -0.9 ± 1.7 mm (p = 0.09). The negative value indicates that MC was on average shallower than TPS. The average difference of the 63 field widths of the 10 patients is -0.7 ± 1.0 mm (p < 0.001), negative indicating on average the MC had a smaller field width. On average, the difference in the penumbra was 2.3 ± 2.1 mm (p < 0.001). The average of the mean clinical target volume dose differences is -1.8% (p = 0.001), negative indicating a lower dose for MC.
Overall, the MC system and TPS gave similar results for field width, the 20% distal edge, and the target coverage. For the 80% distal edge and lateral penumbra, there was slight disagreement; however, the difference was less than 2 mm and occurred primarily in highly heterogeneous areas. These differences highlight that the TPS dose calculation cannot be automatically regarded as correct.
Medical Physics 08/2012; 39(8):4742-7. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Proton therapy is an emerging radiotherapy technology with the potential to improve the therapeutic index in the treatment of lung cancer patients. Since charged particles, such as protons, have a penetration length that can be modified by using different energies, protons offer the clinician the ability to modulate radiation dose deposition along the beam path. This facilitates an increase of the dose to the tumor target while minimizing the volume of normal tissue irradiation. Such precise delivery is particularly relevant in the setting of lung cancer where the targeted tissues are in close proximity to moderately radiation-sensitive organs like the spinal cord, heart, and esophagus, but are also effectively surrounded by the normal lung, which is extremely sensitive to radiation damage. Proton therapy has been investigated for the treatment of surgically curable yet medically inoperable patients as well as patients with regionally advanced disease.
Thoracic Cancer. 05/2012; vol 3(2):109-116.
-
[show abstract]
[hide abstract]
ABSTRACT: The risk of serious late complications in Hodgkin lymphoma (HL) survivors has led to a variety of strategies for reducing late treatment effects from both chemotherapy and radiation therapy. With radiation therapy, efforts have included reductions in dose, reductions in the size of the target volume, and most recently, significant reductions in the dose to nontargeted normal tissues at risk for radiation damage, achieved by using the emerging technologies of intensity-modulated radiation therapy and proton therapy (PT). PT is associated with a substantial reduction in radiation dose to critical organs, such as the heart and lungs, and has the potential to improve not only the therapeutic ratio, but also both event-free and overall survival. This review addresses the rationale and evidence for--and the challenges, cost implications, and future development of--PT as an important part of the treatment strategy in HL.
Oncology (Williston Park, N.Y.) 05/2012; 26(5):456-9, 462-5. · 1.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We investigated the dosimetric impact of proton therapy (PT) on various cardiac subunits in patients with Hodgkin lymphoma (HL).
From June 2009 through December 2010, 13 patients were enrolled on an institutional review board-approved protocol for consolidative involved-node radiotherapy (INRT) for HL. Three separate treatment plans were developed prospectively by using three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and PT. Cardiac subunits were retrospectively contoured on the 11 patients with intravenous-contrast simulation scans, and the doses were calculated for all treatment plans. A Wilcoxon paired test was performed to evaluate the statistical significance (p < 0.05) of 3DCRT and IMRT compared with PT.
The mean heart doses were 21 Gy, 12 Gy, and 8 Gy (relative biologic effectiveness [RBE]) with 3DCRT, IMRT, and PT, respectively. Compared with 3DCRT and IMRT, PT reduced the mean doses to the left and right atria; the left and right ventricles; the aortic, mitral, and tricuspid valves; and the left anterior descending, left circumflex, and right circumflex coronary arteries.
Compared with 3DCRT and IMRT, PT reduced the radiation doses to all major cardiac subunits. Limiting the doses to these structures should translate into lower rates of cardiac toxicities.
International journal of radiation oncology, biology, physics 03/2012; 84(2):449-55. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Organ motion in proton therapy affects treatment dose distribution during both double-scattering (DS) and uniform-scanning (US) deliveries. We investigated the dosimetric impact of target motion using three-dimensional polymer gel dosimeters and a programmable motion platform. A simple one-beam treatment plan with 16 cm range and 6 cm modulation was generated from the treatment planning system (TPS) in both the DS and US modes. One gel dosimeter was irradiated with a stationary DS beam. Two other gel dosimeters were irradiated with the DS and US beams while they moved in the same sinusoidal motion profile using a programmable motion platform. The dose distribution of the stationary DS delivery agreed with the TPS plan. Dosimetric comparisons between DS motion delivery and the MATLAB-based motion model showed insignificant differences. Dose-volume histograms of a cylindrical target volume inside the gel dosimeters showed target coverage degradation caused by motion. A three-dimensional gamma index calculation (3% and 3 mm) confirmed different dosimetric impacts from DS and US with the same target motion. This polymer-gel-dosimeter-based study confirmed the dosimetric impact of intrafraction target motion and its interplay with temporal delivery of different energy layers in US proton treatments.
Physics in Medicine and Biology 02/2012; 57(3):649-63. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To compare three-dimensional conformal proton radiotherapy (3DCPT), intensity-modulated photon radiotherapy (IMRT), and 3D conformal photon radiotherapy (3DCRT) to predict the optimal RT technique for retroperitoneal sarcomas.
3DCRT, IMRT, and 3DCPT plans were created for treating eight patients with retroperitoneal or intra-abdominal sarcomas. The clinical target volume (CTV) included the gross tumor plus a 2-cm margin, limited by bone and intact fascial planes. For photon plans, the planning target volume (PTV) included a uniform expansion of 5 mm. For the proton plans, the PTV was nonuniform and beam-specific. The prescription dose was 50.4 Gy/Cobalt gray equivalent CGE. Plans were normalized so that >95% of the CTV received 100% of the dose.
The CTV was covered adequately by all techniques. The median conformity index was 0.69 for 3DCPT, 0.75 for IMRT, and 0.51 for 3DCRT. The median inhomogeneity coefficient was 0.062 for 3DCPT, 0.066 for IMRT, and 0.073 for 3DCRT. The bowel median volume receiving 15 Gy (V15) was 16.4% for 3DCPT, 52.2% for IMRT, and 66.1% for 3DCRT. The bowel median V45 was 6.3% for 3DCPT, 4.7% for IMRT, and 15.6% for 3DCRT. The median ipsilateral mean kidney dose was 22.5 CGE for 3DCPT, 34.1 Gy for IMRT, and 37.8 Gy for 3DCRT. The median contralateral mean kidney dose was 0 CGE for 3DCPT, 6.4 Gy for IMRT, and 11 Gy for 3DCRT. The median contralateral kidney V5 was 0% for 3DCPT, 49.9% for IMRT, and 99.7% for 3DCRT. Regardless of technique, the median mean liver dose was <30 Gy, and the median cord V50 was 0%. The median integral dose was 126 J for 3DCPT, 400 J for IMRT, and 432 J for 3DCRT.
IMRT and 3DCPT result in plans that are more conformal and homogenous than 3DCRT. Based on Quantitative Analysis of Normal Tissue Effects in Clinic benchmarks, the dosimetric advantage of proton therapy may be less gastrointestinal and genitourinary toxicity.
International journal of radiation oncology, biology, physics 01/2012; 83(5):1549-57. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Proton therapy can deliver a more conformal dose distribution than photon radiation and may allow safe dose escalation in stage III lung cancer. Early outcomes are presented here for patients who received proton therapy with concurrent chemotherapy for non-small-cell lung cancer (NSCLC).
Nineteen patients with regionally advanced NSCLC were treated with concurrent chemotherapy (carboplatin and paclitaxel [n = 18]) and proton therapy from August 2008 to April 2010 either with (n = 7) or without (n = 12) induction chemotherapy. Eighteen patients had stage III NSCLC, and 1 patient had stage IIB disease. The median proton therapy dose was 74 cobalt gray equivalent (CGE) in 2 CGE fractions with 18 patients who received ≥70 CGE. Twelve patients also received selective nodal proton therapy to the adjacent uninvolved nodal regions, with a median dose of 40 CGE (range, 40-46 CGE). The patients were routinely evaluated for treatment-related toxicity and disease progression every 3 months, with a history, physical, and computed tomography or positron emission tomography-computed tomography.
The median follow-ups for living patients were 15 and 16 months (range, 7-26 months), respectively. Nonhematologic and hematologic acute grade 3+ toxicity (<90 days) developed in 1 and 4 patients, respectively. Two of 16 patients assessable for late toxicity (≥90 days) developed a significant grade 3+ nonhematologic late toxicity, whereas 1 patient developed a grade 3+ hematologic late toxicity. Local progression was the site of first relapse in one patient.
Mediastinal proton therapy with concomitant chemotherapy was associated with acceptable toxicity. Although encouraging, longer follow-up with more patients is needed to confirm the long-term efficacy of this treatment.
Clinical Lung Cancer 01/2012; 13(5):352-8. · 2.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To compare the dose reduction to organs at risk (OARs) with proton therapy (PT) versus three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in patients with mediastinal Hodgkin lymphoma (HL) enrolled on a Phase II study of involved-node radiotherapy (INRT).
Between June 2009 and October 2010, 10 patients were enrolled on a University of Florida institutional review board-approved protocol for de novo "classical" Stage IA-IIIB HL with mediastinal (bulky or nonbulky) involvement after chemotherapy. INRT was planned per European Organization for Research and Treatment of Cancer guidelines. Three separate optimized plans were developed for each patient: 3D-CRT, IMRT, and PT. The primary end point was a 50% reduction in the body V4 with PT compared with 3D-CRT or IMRT.
The median relative reduction with PT in the primary end point, body V4, was 51% compared with 3D-CRT (p = 0.0098) and 59% compared with IMRT (p = 0.0020), thus all patients were offered treatment with PT. PT provided the lowest mean dose to the heart, lungs, and breasts for all 10 patients compared with either 3D-CRT or IMRT. The median difference in the OAR mean dose reduction with PT compared with 3D-CRT were 10.4 Gy/CGE for heart; 5.5 Gy/CGE for lung; 0.9 Gy/CGE for breast; 8.3 Gy/CGE for esophagus; and 4.1 Gy/CGE for thyroid. The median differences for mean OAR dose reduction for PT compared with IMRT were 4.3 Gy/CGE for heart, 3.1 Gy/CGE for lung, 1.4 Gy/CGE for breast, 2.8 Gy/CGE for esophagus, and 2.7 Gy/CGE for thyroid.
All 10 patients benefitted from dose reductions to OARs with PT compared with either 3D-CRT or IMRT. It is anticipated that these reductions in dose to OAR will translate into lower rates of late complications, but long-term follow-up on this Phase II INRT study is needed.
International journal of radiation oncology, biology, physics 10/2011; 83(1):260-7. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The purpose of this study was to determine the potential benefit of proton radiation therapy over photon radiation therapy in patients with unresectable stage III non-small-cell lung cancer.
Optimized 3-dimensional conformal photon (3DCRT), intensity-modulated radiation therapy (IMRT) and proton therapy (PT) plans were generated for 8 consecutive patients with unresectable stage III non-small-cell lung cancer using the same target goals and normal tissue constraints. The radiation exposure to non-targeted normal structures, including lung, bone marrow, esophagus, heart, and spinal cord, were compared. Photon doses are expressed in gray (Gy). Proton doses are expressed in cobalt gray equivalents (CGE).
In all patients, 3DCRT, IMRT, and PT plans, achieved the dose goals for the target volumes. Compared with the 3DCRT plans, proton plans offered a median 29% reduction in normal lung V(20) Gy (CGE), a median 33% reduction in mean lung dose (MLD), and a median 30% reduction in the volume of bone marrow receiving a dose of 10 Gy (CGE). Compared with the IMRT plans, the proton plans offered a median 26% reduction in normal lung V(20) Gy (CGE), a median 31% reduction in MLD, and a median 27% reduction in the volume of bone marrow receiving a dose of 10 Gy (CGE).
By reducing the volumes of normal structures irradiated, protons can potentially improve the therapeutic index for patients with unresectable stage III non-small-cell lung cancer receiving combined radiation therapy and chemotherapy.
Clinical Lung Cancer 07/2011; 12(4):252-7. · 2.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Stereotactic body radiotherapy (SBRT) has gained popularity in the treatment of early-stage non-small-cell lung cancer (NSCLC) because of its ability to deliver conformal radiation doses to small targets. However, photon-based SBRT (xSBRT) is associated with significant grade 3+ toxicities. In this study, we compare xSBRT treatment plans with proton-based SBRT (pSBRT) to determine whether dose to normal structures could be reduced if SBRT was delivered with protons.
Eight patients with medically inoperable, peripherally located stage I NSCLC were treated with xSBRT to 48 Gy in 4 12-Gy fractions. These patients were retrospectively re-planned using the same treatment volumes with 3-dimensional conformal double-scatter proton therapy. A Wilcoxon paired test compared dosimetric parameters between the plans for each patient.
Compared with xSBRT there was a dosimetric improvement with pSBRT for these volumes: lung V5 (median difference [MD]=10.4%, p=0.01); V10 (MD=6.4%, p=0.01); V20 (MD=2.1%, p=0.01); V40 (MD=1.5%, p=0.05); and mean lung dose (MD=2.17 Gy, p=0.01). There were also benefits (p=<0.05) in D0.1cm3 and D5cm3 with pSBRT to the heart, esophagus, and bronchus.
In a dosimetric comparison between photon and proton-based SBRT, protons resulted in lower doses to critical organs at risk and a smaller volume of non-targeted normal lung exposed to radiation (V5, V10, V20, and V40). The clinical significance and relevance of these dosimetric improvements remain unknown.
Radiotherapy and Oncology 10/2010; 97(3):425-30. · 5.58 Impact Factor
-
Leukemia & lymphoma 08/2010; 51(8):1559-62. · 2.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To compare dose distributions in targeted tissues (prostate, seminal vesicles, pelvic regional nodes) and nontargeted tissues in the pelvis with intensity-modulated radiotherapy (IMRT) and forward-planned, double-scattered, three-dimensional proton radiotherapy (3D-PRT).
IMRT, IMRT followed by a prostate 3D-PRT boost (IMRT/3D-PRT), and 3D-PRT plans were created for 5 high-risk prostate cancer patients (n = 15 plans). A 78-CGE/Gy dose was prescribed to the prostate and proximal seminal vesicles and a 46-CGE/Gy was prescribed to the pelvic nodes. Various dosimetric endpoints were compared.
Target coverage of the prostate and nodal planning target volumes was adequate for all three plans. Compared with the IMRT and IMRT/3D-PRT plans, the 3D-PRT plans reduced the mean dose to the rectum, rectal wall, bladder, bladder wall, small bowel, and pelvis. The relative benefit of 3D-PRT (vs IMRT) at reducing the rectum and rectal wall V5-V40 was 53% to 71% (p < 0.05). For the bladder and bladder wall, the relative benefit for V5 to V40 CGE/Gy was 40% to 63% (p < 0.05). The relative benefit for reducing the volume of small bowel irradiated from 5 to 30 CGE/Gy in the 3D-PRT ranged from 62% to 69% (p < 0.05). Use of 3D-PRT did not produce the typical low-dose "bath" of radiation to the pelvis seen with IMRT. Femoral head doses were higher for the 3D-PRT.
Use of 3D-PRT significantly reduced the dose to normal tissues in the pelvis while maintaining adequate target coverage compared with IMRT or IMRT/3D-PRT. When treating the prostate, seminal vesicles, and pelvic lymph nodes in prostate cancer, proton therapy may improve the therapeutic ratio beyond what is possible with IMRT.
International journal of radiation oncology, biology, physics 08/2009; 75(4):994-1002. · 4.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The purpose of this study is to accurately estimate the difference between the planned and the delivered dose due to respiratory motion and free breathing helical CT artefacts for lung IMRT treatments, and to estimate the impact of this difference on clinical outcome. Six patients with representative tumour motion, size and position were selected for this retrospective study. For each patient, we had acquired both a free breathing helical CT and a ten-phase 4D-CT scan. A commercial treatment planning system was used to create four IMRT plans for each patient. The first two plans were based on the GTV as contoured on the free breathing helical CT set, with a GTV to PTV expansion of 1.5 cm and 2.0 cm, respectively. The third plan was based on the ITV, a composite volume formed by the union of the CTV volumes contoured on free breathing helical CT, end-of-inhale (EOI) and end-of-exhale (EOE) 4D-CT. The fourth plan was based on GTV contoured on the EOE 4D-CT. The prescribed dose was 60 Gy for all four plans. Fluence maps and beam setup parameters of the IMRT plans were used by the Monte Carlo dose calculation engine MCSIM for absolute dose calculation on both the free breathing CT and 4D-CT data. CT deformable registration between the breathing phases was performed to estimate the motion trajectory for both the tumour and healthy tissue. Then, a composite dose distribution over the whole breathing cycle was calculated as a final estimate of the delivered dose. EUD values were computed on the basis of the composite dose for all four plans. For the patient with the largest motion effect, the difference in the EUD of CTV between the planed and the delivered doses was 33, 11, 1 and 0 Gy for the first, second, third and fourth plan, respectively. The number of breathing phases required for accurate dose prediction was also investigated. With the advent of 4D-CT, deformable registration and Monte Carlo simulations, it is feasible to perform an accurate calculation of the delivered dose, and compare our delivered dose with doses estimated using prior techniques.
Physics in Medicine and Biology 07/2006; 51(11):2763-79. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In radiotherapy practice, one often needs to compare two dose distributions. Especially with the wide clinical implementation of intensity-modulated radiation therapy, software tools for quantitative dose (or fluence) distribution comparison are required for patient-specific quality assurance. Dose distribution comparison is not a trivial task since it has to be performed in both dose and spatial domains in order to be clinically relevant. Each of the existing comparison methods has its own strengths and weaknesses and there is room for improvement. In this work, we developed a general framework for comparing dose distributions. Using a new concept called maximum allowed dose difference (MADD), the comparison in both dose and spatial domains can be performed entirely in the dose domain. Formulae for calculating MADD values for various comparison methods, such as composite analysis and gamma index, have been derived. For convenience in clinical practice, a new measure called normalized dose difference (NDD) has also been proposed, which is the dose difference at a point scaled by the ratio of MADD to the predetermined dose acceptance tolerance. Unlike the simple dose difference test, NDD works in both low and high dose gradient regions because it considers both dose and spatial acceptance tolerances through MADD. The new method has been applied to a test case and a clinical example. It was found that the new method combines the merits of the existing methods (accurate, simple, clinically intuitive and insensitive to dose grid size) and can easily be implemented into any dose/intensity comparison tool.
Physics in Medicine and Biology 03/2006; 51(4):759-76. · 2.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To investigate the feasibility and the advantages of a portal-imaging mode on a medical accelerator, consisting of a thin low-Z bremsstrahlung target and a thin Gd2O2S/film detector, for patient imaging.
The international code of practice for high-energy photon dosimetry was used to calibrate dosimetry instruments for the imaging beam produced by 4.75 MeV electrons hitting a 6mm thick aluminium target. Images of the head and neck of a humanoid phantom were taken with a mammography film system and the dose in the phantom was measured with TLDs calibrated for this beam. The first head and neck patient images are compared with conventional images (taken with the treatment beam on a film radiotherapy verification detector). Visibility of structures for six patients was evaluated.
Images of the head and neck of a humanoid phantom, taken with both imaging systems showed that the contrast increased dramatically for the new system while the dose required to form an image was less than 10(-2)Gy. The patient images taken with the new and the conventional systems showed that air-tissue interfaces were better defined in the new system image. Anatomical structures, visible on both films, are clearer with the new system. Additionally, bony structures, such as vertebrae, were clearly visible only with the new system. The system under evaluation was significantly better for all features in lateral images and most features in anterior images.
This pilot study of the new portal imaging system showed the image quality is significantly improved.
Radiotherapy and Oncology 08/2005; 76(1):63-71. · 5.58 Impact Factor
