External-beam Therapy Research Articles

A Comparative Study of Result of Treatment of Cancer Cervix Patients Treated by Two Separate Schedules of Radiotherapy

Background: Cervical cancer is the most common cancer of Bangladeshi women diagnosed mostly (>80%) at stage II and stage III. Rdaiotherapy (both teletherapy and brachytherapy) is the most important modality of treatment at these stages.Objective: To compare the local control, diseases free survival and overall survival between the (cancer cervix) patients treated randomly by two schedules of radiotherapy. Method: From June 1996 to June 2005, patients with histologically confirmed carcinoma cervix (Ca.cervix) were treated by external beam therapy (EBRT) as well as intra cavitery brachytherapy (ICRT) along with concurrent/sequential chemotherapy with cisplatin and 5- Fluorouracil. EBRT was given by cobalt60 teletherapy machine and ICRT by caesium137 low dose rate machine. The patients were divided into two groups according to treatment schedules. Group I: the patients in this group received EBRT in whole pelvis in two steps, first with open field upto 10-20 Gy then by applying midline shield with lead block 30-40Gy in 25-28 total fractions, five days a week; they also received 50-70 Gy to point A by ICRT in 2-4 weekly fractions. Group II: patients in this group received with open field a dose of 45-50Gy in 25-28 fractions, 5 days a week by EBRT and 25-30 Gy at point A by ICRT in 1-2 weekly fractions.Result: In Group I, 96 out of 101 and in Group II, 104 out of 118 patients were eligible for evaluation. In both groups patients were distributed according to stages and age more or less equally; their age range were 30-70 years and mean age was 47.2 years in Group I and age range were 25-80 years and mean age was 46 years in Group II. Squamous cell carcinoma were found (90%) and performance status was WHO grade 0-1 (>75%) in both groups. Local control of disease at 5 years was 65% in group I and 51% in group II. Overall survival at 2 years, 5 years, 7 years and 9 years in group I, was 71%, 64%, 55%, 46% and in group II, 54%,50%, 43%,32% respectively. Distant metastasis occurred in 22% in-group I and 28% in-group II. Lymph node, lung, liver, peritoneum were common site of metastasis. Proctitis, cystitis, vaginal stenosis in group I was 80%, 33% 16% and in Group II 29%, 13% and 5% respectively. Conclusion: External beam therapy and brachytherapy was effective treatment in carcinoma. Cervix in both operable and inoperable stages. In small volume of tumor, both schedules of radiotherapy were more or less equivalent but in bulky diseases Group I schedule that was higher dose by brachytherapy at point A showed better result; though the complication was more DOI: http://dx.doi.org/10.3329/bjog.v25i2.13739 Bangladesh J Obstet Gynaecol, 2010; Vol. 25(2) : 50-58

Is Partial Breast Irradiation a Safe and Effective Treatment Approach for Women with Early-Stage Breast Cancer?

Breast-conserving therapy (BCT) represents the standard care in the management of early-stage breast cancer, because long-term outcomes with breast conservation are comparable with those of mastectomy. Adjuvant radiation therapy remains an essential component of BCT with standard techniques requiring 5–6½ weeks. Accelerated partial breast irradiation (APBI) is a technique developed over the past two decades that enables completion of treatment in one week or less. Review of the expanding literature reveals increasing support for APBI using several techniques, including interstitial brachytherapy, balloon-based brachytherapy, and external beam therapy. Novel treatment strategies, including intraoperative radiation therapy, hypofractionated APBI, and proton therapy, require further results before definitive conclusions can be made. Although there is currently a lack of level I evidence, with the pending publication of multiple phase III trials comparing whole-breast irradiation and APBI, modern treatment incorporating APBI should soon be developed.

Optimization of three dimensional planning dosimetric in breast phantom for match region of supraclavicular and tangential fields

Complex geometry of breast tissue causes perturbation in dose distribution. This problem can beget overdose or under-dose points in match region of three fields. The aim of this study is to create dose homogeneity distribution in match region between tangential and supraclavicular fields (SCF) with Gafchromic external beam therapy (EBT) film. In this study, an anatomical slab phantom was designed with cork lung inhomogeneity and plexiy colored heart part. Conventional and three dimensional (3D) methods were utilized along with Gafchromic EBT film. In asymmetric fields (3D method) much better results in match region were observed (i.e., maximum amount overlap area of 0.43 cm(2), overlap depth of 3.55 cm and an average overlap width of 0.75 cm). This study revealed that EBT film is a proper tool for two dimensional (2D) relative-dose measurements. The study showed difficulties in achieving homogenous dose distribution in match region of tangential and supraclavicular.

Prostate Cancer: Do We Always have to Treat for Cure?

In the past 50 years, safer and better tolerated treatments for prostate cancer have emerged. Also, new data from epidemiologic studies show that prostate cancer can shorten the lifespan in certain groups of men [2]. Although contentious, a recent randomised study contends that screening to detect prostate cancer saves lives [3]. As well, the publicised deaths of several prominent politicians and celebrities from prostate cancer helped to push the pendulum towards the early detection and treatment of prostate cancer. This has resulted in an increase in the variety and complexity of treatments for prostate cancer. Surgical techniques have been refined to minimise complications and incorporate robotic devices to improve the removal of the prostate with minimally invasive procedures. Radiation therapy has included novel techniques of implanting minute radioactive isotopes directly into the prostate gland to sterilise the cancer. External beam therapy has evolved to include enhanced precision 3-D shaping, intensity modulation (to assign differential doses to the target), and dose escalation in conjunction with image guidance during radiation delivery to achieve higher kill ratios. Improved medications to deprive prostate cancer of testosterone can be used in combination with the above procedures or as stand alone treatment. New classes of drugs and vaccines are now available to target cancer cells that have become immune to standard hormonal therapy. This abundance of therapeutic modalities has encouraged clinicians to incorporate ever increasingly potent strategies to eradicate prostate cancer. The downsides to this approach are treatment induced sideeffects, and the spiralling costs of health care. A close examination of the natural history of prostate cancer can help achieve a balance in the treatment of this disease as patients actively desire to both eradicate the cancer as well as to limit unpleasant medical consequences [4]. Clearly, treatment is unnecessary for those in whom other health concerns will shorten life before prostate cancer becomes significant. Active surveillance is now increasingly offered to patients with early, slowly progressing cancers who have limited life expectancy, usually less than 5 years [5]. The Prostate Specific Antigen (PSA) is a tumour marker that is widely employed in treatment decisions as it reflects tumour burden and progression. Latterly, it has been used as a surrogate measure of success as it predicts for failure approximately 3 years before the disease is detected by palpation or imaging [6]. While useful, this has given rise to exhaustive efforts to render the PSA undetectable by intensifying treatment. Combined modality therapy, and dose escalation have been proven to eliminate or delay PSA rise after treatment, but with attendant increased morbidity and financial cost. One of the pertinent questions to be debated is whether or not it is necessary to achieve a lifetime of undetectable PSA after the treatment of prostate cancer.

Developing New Small Molecular Drugs for Prostate Cancer Therapy

Most of the early prostate cancer has no obvious symptoms, but its malignancy metastasis will cause largely deaths. The treatment options for patients with prostate cancer include traditional surgery, external beam therapy, hormone therapy, small molecular drug and cryosurgery. It was considered non-traditional treatments also can be used in alternative medicines for prostate cancer therapy. There are well-known molecular mechanisms and their pathogenesis, which provide potential targets for drug screening on the prostate cancer. Currently, natural plant extracts or human tissues active ingredients are widely used for the treatment of cancer. Then isolated effective substances in the extract, and further prepared large amounts of small molecule drugs by chemical synthesis. In this review, we summarized four small molecular drugs, abiraterone, docetaxel, isochaihulactone and butylidenephthalide, and their detailed anti-tumor mechanisms. These indicate that small molecular drug is a very efficient way and can be used for prostate cancer treatment.

Abstract P4-15-03: Patterns of relapse following re-irradiation of the breast using partial breast brachytherapy (PBB)

Abstract Purpose: This study is undertaken to evaluate the patterns of relapse among patients with a prior history of irradiation where the RT field included the breast, and who received re-irradiation using PBB for a localized second cancer event in the breast using partial breast. Materials and Methods: Twenty-seven patients were enrolled in an IRB approved study. Nineteen patients had prior history of breast cancer treated with lumpectomy and external beam therapy (ERT), and 8 patients had prior history of mantle RT. All patients underwent lumpectomy with negative margins and received a median dose of 45Gy PBB. The median time interval between the primary breast cancer diagnosis and the second cancer event in the ipsilateral breast is 94-months (range 28-months to 211-months). The median time between mantle RT and the breast cancer is 245 months. Results: At a median follow up of 73 months following lumpectomy and PBB 14.8 % (4/27) patients developed a local recurrence and were salvaged by mastectomy. The 5-year Kaplan Meier local disease-free survival and mastectomy-free survival is 100% and 81%, respectively. Remarkably, one third of patients with prior history of mantle RT developed third primary cancers (pancreas, lung and renal). All patients with the third primary cancers died free of any relapse from the breast cancer. None of the patients with prior history of breast cancer developed a second malignancy, and 3/21 developed distant metastases. Conclusions: In appropriately selected patients with prior history of lumpectomy and ERT for breast cancer we observed a high rate of local control and freedom from mastectomy. Patterns of relapse among patients with prior mantle RT suggest that breast conservation and PBB was appropriate for treating early stage disease. Breast conservation therapy did not have a detrimental effect on breast cancer specific outcome and eventual patient survival. Patients motivated for breast conservation may have an alternative to mastectomy at initial diagnosis. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-15-03.

A Real-time Scintillating Fiber Detector to Improve Patient Safety in External Beam Radiation Therapy

The purpose of this study is to improve patient safety in radiation oncology by implementing real time verification of fluence delivered during external beam radiation therapy using a radiation hard scintillating fiber sensor array architecture and real time data acquisition hardware. Radiation oncology patients undergo highly complicated treatment procedures in which delivered dose should be controlled, recorded, and verified for quality and safety. Currently, radiation treatment cumulative dose is measured prior to delivery, which is not sensitive to temporal variations that could occur during imaging or treatment. Therefore, the actual quality and safety of the radiation therapy procedure is unknown and any deviation from the intended dose cannot be identified, thus cannot be corrected. To address this gap in patient safety, we developed scintillating fiber array sensors with real time data acquisition hardware to implement real time fluence verification of photon and electron beams. These on line detectors can operate on a wide range of clinical devices through modification of sensor element geometry and front end electronics operating parameters. This common technological platform provides a simplified method to construct low cost radiation based modality specific dosimeters. As an example, we developed and tested a scintillating fiber array for linac external beam radiation therapy with plastic encapsulated scintillating fibers and photodetectors integrated in a monolithic configuration. This detector has high speed front end amplifiers for real time acquisition and verification of the pulsed linac output during treatment. We determined the detector sensitivity and linearity response with respect to beam intensity and field size for the clinical range of photon beam energies. The scintillating fiber spatial detection sensitivity is 2.3 mV/mm with a statistical error of 0.5 mV. Fiber linearity response with respect to beam intensity and field size was within 2% for all tested beams. The front end amplifiers have a time response of 250 nsec. The fiber dosimeter has a maximum beam attenuation of 2.4% and is used in an online transmission configuration for in vivo treatment delivery accuracy monitoring. The development of this technology addresses the urgent need for in vivo real time quality assurance of external beam therapy to increase patient safety. The developed linear fiber array has high spatial and temporal resolution to provide accurate dose verification, thus providing therapists real time feedback of external beam treatment fluence with minimum beam attenuation to increase patient safety. Configurations for other external beam treatment devices such as tomotherapy machines could be done with little design modification.

Extended Followup Oncologic Outcome of Randomized Trial Between Cryoablation and External Beam Therapy for Locally Advanced Prostate Cancer (T2c-T3b)

We assessed and compared the survival outcomes between cryoablation and external beam radiation therapy in patients with locally advanced prostate cancer (cT2c-cT3b). Patients with locally advanced prostate cancer, recruited from 1999 to 2002, were randomized to primary cryoablation or external beam radiotherapy. All patients received neoadjuvant hormonal therapy for 3 months before and 3 months after the procedures. Patients underwent followup transrectal ultrasound guided biopsy (at 3, 6, 12, 18 and 24 months for cryoablation, and at 18 and 24 months for external beam radiotherapy) and as clinically indicated thereafter. Biochemical failure was based on the Phoenix criterion (prostate specific antigen nadir +2 ng/dl). A total of 62 patients completed the trial. Median followup was 105.2 months (SD ±35.8). Accrual was limited due to newer data favoring longer neoadjuvant hormonal therapy and higher external beam radiotherapy dose for locally advanced prostate cancer. There was a greater reduction in prostate volume in the cryoablation group after intervention (-54% vs -34%, p ≤0.01). Disease specific survival and overall survival were comparable between the groups. However, the 8-year biochemical disease-free survival rate was significantly lower in the cryoablation group (17.4% vs 59.1%) (p = 0.01). This randomized trial with median followup approaching 9 years showed that cryoablation was inferior in attaining biochemical disease-free survival in patients with locally advanced prostate cancer (cT2c-T3). Cryoablation may be more suited for less bulky prostate cancer. Longer duration neoadjuvant hormonal therapy or a multimodal approach may provide optimal biochemical disease-free survival in this patient population.

SU-E-T-233: Evaluation of Superficial Doses for Postmastectomy Radiotherapy.

To measure and to evaluate the surface and superficial doses for patients requiring postmastectomy radiotherapy (PMRT) with different treatment techniques. An elliptic cylinder cork and super-flab boluses were used to simulate the lung and the chest wall, respectively. Sets of CT images with chest wall thicknesses of 5, 8, 10, 13, and 15 mm were acquired. Hypothetical clinical target volumes were outlined and modified to fit a margin of 1 -3 mm away from the surface. The planning target volume was initially created by expanding an isotropic 3 mm margin from CTV and then a margin of 1-3 mm was shrunk from the phantom surface. Treatment techniques using a pair of tangential wedged fields (TWF) and 4-field IMRT were designed with a prescribed fraction dose (Dp) of 180 cGy. Superficial dose profiles around the phantom circumference at depths of 0, 1, 2, 3, and 5 mm were obtained for each treatment technique using radiochromic external beam therapy (EBT) films. The TWF plans show a dose buildup about 3 mm at the median and lateral tangential incident regions with a surface dose of about 52% of Dp. Dose profiles were more uniform in the PTV region for the 4-F IMRT plans. Most of the PTV region had doses higher than 94% of Dp at depths larger than 1 mm. The mean surface dose was about 65% of Dp for the 4-F IMRT plans. The maximum dose for the 4-F IMRT plans was less than 118.4% of Dp. The dose variations caused by the oblique incidence and a thin chest wall are modulated and reduced in the IMRT plans. More uniform dose distributions within the PTV are obtained with the 4-F IMRT plans.

Surface and superficial dose dosimetric verification for postmastectomy radiotherapy

In patients given postmastectomy radiotherapy (PMRT), the chest wall is a very thin layer of soft tissue with a low-density lung tissue behind. Chest wall treated in this situation with a high-energy photon beam presents a high dosimetric uncertainty region for both calculation and measurement. The purpose of this study was to measure and to evaluate the surface and superficial doses for patients requiring PMRT with different treatment techniques. An elliptic cylinder cork and superflab boluses were used to simulate the lung and the chest wall, respectively. Sets of computed tomography (CT) images with different chest wall thicknesses were acquired for the study phantom. Hypothetical clinical target volumes (CTVs) were outlined and modified to fit a margin of 1–3 mm, depending on the chest wall thickness, away from the surface for the sets of CT images. The planning target volume (PTV) was initially created by expanding an isotropic 3-mm margin from the CTV, and then a margin of 3 mm was shrunk from the phantom surface to avoid artifact-driven results in the beam-let intensity. Treatment techniques using a pair of tangential wedged fields (TWFs) and 4-field intensity-modulated radiation therapy (IMRT) were designed with a prescribed fraction dose (Dp) of 180 cGy. Superficial dose profiles around the phantom circumference at depths of 0, 1, 2, 3, and 5 mm were obtained for each treatment technique using radiochromic external beam therapy (EBT) films. EBT film exhibits good characteristics for dose measurements in the buildup region. Underdoses at the median and lateral regions of the TWF plans were shown. The dose profiles at shallow depths for the TWF plans show a dose buildup about 3 mm at the median and lateral tangential incident regions with a surface dose of about 52% of Dp. The dose was gradually increased toward the most obliquely tangential angle with a maximum dose of about 118% of Dp. Dose profiles were more uniform in the PTV region for the 4-F IMRT plans. Most of the PTV region had doses >94% of Dp at depths >1 mm. The mean surface dose was about 65% of Dp for the 4-F IMRT plans. The maximum dose for the 4-F IMRT plans was <118.4% of Dp. The application of added bolus has to consider the treatment technique, tumor coverage, and possible skin reactions. For PMRT, if the chest surface and wall are treated adequately, at least 3 mm bolus should be added to the chest wall when tangential beams and 6-MV photon energy are arranged. However, when the surface and superficial regions are not high-risk areas, an IMRT plan with tangential beams and 6-MV photon energy can provide uniform dose distributions within the PTV, spare the skin reaction, and deliver sufficient doses to the chest wall at depths >1 mm.

Abstract 1473: Nanocoated brachytherapy spacers eluting radiosensitizers for biological in situ image-guided radiation therapy of prostate cancer

Abstract The overall goal of this project is to develop means to locally radio-sensitize the prostate to enable prostate cancer (PCa) cure with the use of lower radiation doses, thereby leading to less rectal toxicity. This new approach for chemoradiation therapy (CRT), termed Biological In-Situ Image Guided Radiation Therapy BIS-IGRT, involves the coating of spacers routinely used during prostate I-125-based brachytherapy with radiosensitizing drugs (e.g. docetaxel DTX for PCa). This approach provides localized in-situ delivery of the sensitizer to the tumor and avoids the toxicity associated with current systemic delivery of radiosensitizers. BIS-IGRT adds radiosensitization capability to the standard brachytherapy procedure and with minimal additional inconvenience to the patient. Current CRT with adjuvant systemic chemotherapy does not provide the sustained delivery and drug concentration needed for efficient radiosensitization. Thereby BIS-IGRT improves the therapeutic ratio of radiation therapy without introducing additional patient interventions over current brachytherapy procedures. We have established the following: 1. We have shown through modeling that drug distributions can be achieved that can lead to increased efficiency of image-guided brachytherapy (drug-coated spacers) or image guided external beam therapy (drug-coated fiducials). 2. Doxorubicine-coated fiducials (Dox/PLGA-PEG/CHIT) show release characteristics over 40 days in aqueous media, which is tailored to the time scales required for BIS-IGRT. The cytotoxicity of Dox/ PLGA-PEG NP is comparable to that of free Dox, so that there is no reduction of activity upon encapsulation in the NP. 3. Localized bolus injection of dye-loaded PLGA-PEG nanoparticles (NPs) distributes within 24 hours throughout the tumor, indicating that the sustained release from coated brachytherapy spacers has the potential to achieve the desired biological dose-painting of the tumor. BIS-IGRT could proffer radiation oncologists and medical physicists with a new treatment option for substantially enhancing therapeutic ratio and boosting cure rate for the hundreds of thousands of Americans diagnosed with prostate cancer each year. This new treatment approach would be of crucial benefit for patients with local relapse who require salvage radiotherapy but have reached their radiotherapy normal tissue dose limits. BIS-IGRT can still be accompanied by IV administration of chemotherapeutics, particularly for micro-metastasis, so that existing therapeutic approaches are not compromised. In addition BIS-IGRT could potentially become a mainstream treatment for patients newly diagnosed with prostate or other cancers, where radiation therapy is a common treatment modality. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1473. doi:1538-7445.AM2012-1473

1128 AFRICAN-AMERICAN MEN WITH LOW RISK PROSTATE CANCER MODERN TREATMENT AND OUTCOME TRENDS

You have accessJournal of UrologyProstate Cancer: Localized V1 Apr 20121128 AFRICAN-AMERICAN MEN WITH LOW RISK PROSTATE CANCER MODERN TREATMENT AND OUTCOME TRENDS Augustine Obirieze, MBBS, MPH Ambria Moten, BS Delenya Allen, andMD, MPH Chiledum AhaghotuMD, FACS Augustine ObiriezeAugustine Obirieze Washington, DC More articles by this author , Ambria MotenAmbria Moten Washington, DC More articles by this author , Delenya AllenDelenya Allen Washington, DC More articles by this author , and Chiledum AhaghotuChiledum Ahaghotu Washington, DC More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.1237AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES To investigate the clinical characteristics and treatment patterns for African-American men with low risk prostate cancer using a national, population-based dataset. METHODS We conducted a retrospective review of the Surveillance Epidemiology and End Results database for the period 2004-2008. African-American men aged 40 years or older with low risk prostate cancer (stage T2a or lower, a PSA level ≤ 10ng/mL, and a Gleason score of 6 or lower) were identified. We reviewed all recorded treatment modalities. Definitive treatment was defined as having either a radiation therapy (external beam therapy, and/or radioisotope/radioactive implant as listed in SEER), prostatectomy (radical, or local excision) or targeted prostate cryoablation. Chi square test was used for bivariate analysis of categorical variables. RESULTS A total of 7,246 patients met our inclusion criteria. The majority of the patients were less than 65 years at diagnosis (59%), had PSA level between 4.1-6.9 ng/mL (57.31%), and Gleason score of 6 (96.25%). 74% received definitive treatment, comprising radiation therapy alone (47%), prostatectomy alone (25.24%), prostate cryoablation alone (0.87%), and prostatectomy with radiotherapy (0.66%). Of those who received radiation therapy, most received external beam (61.92%). Among those who had prostatectomy and available information on tumor size (71% unknown), 56.3% had clinically relevant tumor size (> 1cm). Patients who did not receive definitive treatment were more likely to be 75 years or older (13.88% vs 5.44%, p-value<0.001). Cancer-specific mortality was higher for those who did not receive definitive treatment (0.45% vs 0.18%, p-value=0.045). Similar findings were seen with overall mortality (7.92% vs 2.86%, p-value<0.001), the highest noted in patients 75 and older (18.63% vs 5.50%). CONCLUSIONS Using a large, modern cohort of African-American men with early-onset, low-risk prostate cancer, our study revealed that the majority of these patients received definitive treatment; and of those who did, most received radiotherapy. Based on the available data, the majority of the patients who underwent prostatectomy had pathologically significant tumor volume. Those who received definitive treatment had significantly less cancer-specific and overall mortality irrespective of age. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e457 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Augustine Obirieze Washington, DC More articles by this author Ambria Moten Washington, DC More articles by this author Delenya Allen Washington, DC More articles by this author Chiledum Ahaghotu Washington, DC More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Quality Assurance Peer Review Chart Rounds in 2011: A Survey of Academic Institutions in the United States

In light of concerns regarding the quality of radiation treatment delivery, we surveyedthe practice of quality assurance peer review chart rounds at American academic institutions. An anonymous web-based survey was sent to the chief resident of each institution across the United States. The response rate was 80% (57/71). The median amount of time spent per patient was 2.7minutes (range, 0.6-14.4). The mean attendance by senior physicians and residents was 73% and 93%, respectively. A physicist was consistently present at peer review rounds in 66% of departments. There was a close association between attendance by senior physicians and departmental organization: in departments with protected time policies, good attendance was 81% vs. 31% without protected time (p = 0.001), and in departments that documented attendance, attending presence was 69% vs. 29% in departments without documentation (p<0.05). More than 80% of institutions peer review all external beam therapy courses; however, rates were much lower for other modalities (radiosurgery 58%, brachytherapy 40%-47%). Patient history, chart documentation, and dose prescription were always peer reviewed in >75% of institutions, whereas dosimetric details (beams, wedges), isodose coverage, intensity-modulated radiation therapy constraints, and dose-volume histograms were always peer reviewed in 63%, 59%, 42%, and 50% of cases, respectively. Chart rounds led to both minor (defined as a small multileaf collimator change/repeated port film) and major (change to dose prescription or replan with dosimetry) treatment changes. Whereas at the majority of institutions changes were rare (<10% of cases), 39% and 11% of institutions reported that minor and major changes, respectively, were made to more than 10% of cases. The implementation of peer review chart rounds seems inconsistent across American academic institutions. Brachytherapy and radiosurgical procedures are rarely reviewed. Attendance by senior physicians is variable, but it improves when scheduling clashes are avoided. The potential effect of a more thorough quality assurance peer review on patient outcomes is not known.

Superconductivity in Medicine

Superconductivity is playing an increasingly important role in advanced medical technologies. Compact superconducting cyclotrons are emerging as powerful tools for external beam therapy with protons and carbon ions, and offer advantages of cost and size reduction in isotope production as well. Superconducting magnets in isocentric gantries reduce their size and weight to practical proportions. In diagnostic imaging, superconducting magnets have been crucial for the successful clinical implementation of magnetic resonance imaging. This article introduces each of those areas and describes the role which superconductivity is playing in them.

Urethral Sparing Intensity Modulated Radiation Therapy (US-IMRT) Is Not Shown To Improve Urinary Quality of Life (QOL) in Low Risk Prostate Cancer (PCa): Results of a Randomized Phase II Trial

Low-risk PCa patients have excellent outcomes, with treatment selection often determined by patient preference and perceived impact of treatment modality on QOL. Acute urinary symptoms are common during external beam therapy, while chronic symptoms have been linked to urethral dose. Since most low risk PCa occurs in the peripheral zone, we hypothesized that US-IMRT could improve urinary toxicity while maintaining biochemical control.

Early Toxicity Results with 3-D Conformal External Beam Therapy (CEBT) from the NSABP B-39/RTOG 0413 Accelerated Partial Breast Irradiation (APBI) Trial

Early Toxicity Results with 3-D Conformal External Beam Therapy (CEBT) from the NSABP B-39/RTOG 0413 Accelerated Partial Breast Irradiation (APBI) Trial

The effect of metallic implants on radiation therapy in spinal tumor patients with metallic spinal implants

The aim of this study was to evaluate the effect of metallic implants on the dose calculation for radiation therapy in patients with metallic implants and to find a way to reduce the error of dose calculation. We made a phantom in which titanium implants were inserted into positions similar to the implant positions in spinal posterior/posterolateral fusion. We compared the calculated dose of the treatment planning systems with the measured dose in the treatment equipment. We used 3 kinds of computed tomography (CT) (kilovoltage CT, extended-scaled kilovoltage CT, and megavoltage CT) and 3 kinds of treatment equipment (ARTISTE, TomoTherapy Hi-Art, and Cyberknife). For measurement of doses, we used an ionization chamber and Gafchromic external beam therapy film. The absolute doses that were measured using an ionization chamber at the isocenter in the titanium phantom were on average 1.9% lower than those in the reference phantom (p = 0.002). There was no statistically significant difference according to the kinds of CT images, the treatment equipment, and the size of the targets. As the distance from the surface of the titanium implants became closer, the measured doses tended to decrease (p < 0.001), and this showed a statistically significant difference among the kinds of CT images: the effect of metallic implants was less in the megavoltage CT than in the kilovoltage CT or the extended-scaled kilovoltage CT. The error caused by the titanium implants was beyond a clinically acceptable range. To reduce the error of dose calculation, we suggest that the megavoltage CT be used for planning. In addition, it is necessary to consider the distance between the titanium implants and the targets or the organs at risk to prescribe the dose for the target and the dose constraint for the organs at risk.

Local recurrences in cervical cancer patients in the setting of image-guided brachytherapy: A comparison of spatial dose distribution within a matched-pair analysis

PurposeIt has been shown that a cumulative dose of ⩾87Gy (EQD2) of external beam radiotherapy (EBRT) and image guided adaptive brachytherapy (IGABT) to the high risk clinical target volume (HR CTV) confer a local control rate >95% in locally advanced cervical cancer. This study examines the dose distribution within the HR CTV and intermediate (IR) CTV in patients with cervical cancer treated with definitive EBRT +/− concomitant chemotherapy and MRI-based IGABT between patients with local recurrence (LR) and patients in continuous complete local remission (CCLR). Material and methodsFrom 1998 to 2010, 265 patients were treated with definitive EBRT +/− concomitant chemotherapy and IGABT. Twenty-four LRs were documented. For the statistical analysis all patients with LR were matched to patients in CCLR from our database according to the following criteria: FIGO stage, histology, lymph node status, tumour size and chemotherapy.DVH parameters (D50, D90, D98, D100) were reported for HR CTV and IR CTV. In order to report the minimum dose in the region where the recurrence occurred, the HR CTV/IR CTV were divided into four quadrants on transversal planes. The minimum dose at the HR CTV/IR CTV contour was measured (within the corresponding quadrant closest to the LR) in the treatment planning system. A mean minimum point dose (MPD) was calculated by averaging these measurements on four consecutive slices at the level of the recurrence for each of the 4 brachytherapy fractions. EQD2 doses were calculated by summation of all BT and external beam therapy fractions.For each matched patient in the control group the measurements were performed on the same quadrant and at the same level. ResultsSufficient image data were available for 21 LRs. Eight central failures and 13 non-central failures were observed. The mean D90 and D100 for HR CTV were 77Gy and 61Gy for patients with LR and 95Gy and 71Gy for patients in CCLR, respectively (p<0.01). The MPD for HR CTV was 72Gy for patients in the LR arm and 99Gy for patients in the CCLR arm (p<0.01). In the LR arm seven patients had a D90 for HR CTV ⩾87Gy, however, in only three patients the MPD was ⩾87Gy. ConclusionThis study demonstrated significant differences in local outcome according to the delivered dose. In 85% of the LRs systematic low dose regions with less than 87Gy were found at HR CTV contour. Systematic low dose regions leading to local recurrence could be detected even if a D90 HR CTV ⩾87Gy was applied. In addition to DVH parameters, inspection of the spatial dose distribution remains a key point in dose prescription.

Dependence of intrafraction motion on fraction duration for pediatric patients with brain tumors

The purpose of this study was to quantify the intrafraction motion of pediatric patients with brain tumors during radiation therapy and investigate any correlation between motion, use of general anesthesia, and daily treatment duration. 100 pediatric patients with a mean age of 8.5 years (range: 1.0 to 17.8) were included in this prospective study. Forty‐one patients required general anesthesia during treatment, mean age 4.8 years; 59 patients did not, mean age 11.2 years. Each patient had an intracranial tumor and was treated in the supine position with a thermoplastic facemask and headrest for immobilization. A pretreatment localization CBCT was acquired for each treatment fraction and a post‐treatment CBCT was acquired every other fraction. If the magnitude of the patient's position pre‐CBCT offset was ≥2 mm, the position was corrected. The difference between the patient's position based on the post‐CBCT and the assumed position at the start of treatment (either the pre‐CBCT offset if the magnitude was < 2 mm, or 0 offset due to correction) was determined and labeled intrafraction motion. Correlations between daily treatment duration and intrafraction motion were examined. There was an average of 14.2 post‐CBCTs acquired per patient. The magnitude of the mean intrafraction motion was 1.2±0.8 mm for patients requiring general anesthesia, and 1.5±1.2 mm for those without (p<0.001). The mean offset in each direction was less than 0.5 mm for both cohorts. There was no correlation between daily treatment duration and the magnitude of intrafraction motion. The intrafraction motion of pediatric patients undergoing external beam therapy for intracranial tumors is small, < 2 mm, and is independent of the daily treatment duration.PACS number: 87.53.Jw

TH-C-301-05: Practical Medical Physics Session

Among dosimetry tools radiographic films have the unique advantage of providing the capability for dose measurements at very high spatial resolution; and between dosimetry films, radiochromic films are particularly advantageous for their versatility. Thus radiochromic films can be handled in light, easily cut to any size and shape, bent to conform to curved surfaces and immersed in water. All these attributes are embodied in the GAFCHROMIC® family of dosimetry films as used in a broad spectrum of medical applications including external beam therapy, brachytherapy, machine quality assurance and radiology. Current trends in external beam therapy are towards ever more precise treatment protocols with less dose fractionation. Both these factors increase the importance of pre‐treatment validation of treatment plans and place a high and increasing value on those measurement techniques that are able to deliver the ability for excellent resolution in the spatial frequency and dose domains. The talk will show, by example, the range of medical applications covered by radiochromic dosimetry films. It will demonstrate how the attributes of these films are being used to advantage in a full spectrum of radiotherapy applications. The presentation will finish by introducing another advantage of radiochromic film and showing the benefit of multi‐channel film dosimetry as a means for improving the integrity of dose measurements by separating dose‐independent artifacts and removing them from the response measurement.