Undergoing Intensity Modulated Radiation Therapy Research Articles

FDG-PET/CT Predicts Outcome in Oropharingeal Carcinoma Patients Undergoing Intensity Modulated Radiation Therapy with Dose Escalation to FDG-avid Tumour Volumes.

To evaluate the predictive value of FDG-PET/CT parameters on outcome of oropharyngeal squamocellular cancer (OSCC) patients undergoing helical tomotherapy (HTT), with dose escalation to FDG-PET/CT positive tumour volumes using the simultaneous integrated boost (SIB) technique. We analysed 41 patients studied by FDG-PET/CT and treated with radical intent between 2005 and 2014 for OSCC. HTT-SIB was delivered in 30 fractions concomitantly: 69 Gy, as SIB, to the PET-positive volume (biological target volume - BTV-PET), both to the primary tumour (T) and lymph nodes (N), 66 Gy to the T and positive N, 54 Gy to the laterocervical nodes at risk. Selected PET parameters were recovered: maximum and mean standardized uptake values (SUVmax and SUVmean, respectively), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) obtained with different thresholds (40-50-60% of the SUVmax) for T and N. The correlation between these parameters and the 3-year overall (OS), cancer specific (CSS), disease free (DFS), local relapse free for T and N (LRFS-T and LRFS-N) and distant metastasis free (DMFS) survivals was investigated. The median follow-up was 37 months (range: 3-125). The 3-year OS, CSS, DFS, LRFST, LRFS-N and DMFS were 86%, 88%, 76%, 83%, 88% and 91%, respectively. BTVT+ N>30.9cc and BTV-T>22.4cc were correlated with CSS (p=0.02) and OS (p=0.006) respectively; TLG-T-60>34.6cc was correlated with CSS (p=0.04) and OS (p=0.01). MTV-T-60>4.4cc could predict a higher risk of relapse/death (CSS: p=0.033; hazard ratio (HR) =10.92; OS: p=0.01; HR=16.4; LRFS-T: p=0.02; HR=13.90; LRFS-T+N: p=0.03; HR=6.50). PET parameters predicted survival outcomes and may be considered in the future in the implementation of more personalized treatment schedules in patients affected by OSCC undergoing radiotherapy. FDG-PET/CT dose escalated HTT-SIB allowed very promising 3-year disease control rates in OSCC patients.

Renal Function Outcomes of High-risk Neuroblastoma Patients Undergoing Radiation Therapy

To analyze the renal function outcomes in patients undergoing radiation therapy for neuroblastoma. The clinical metrics of renal function were analyzed in patients undergoing radiation therapy for high-risk neuroblastoma from 2000 to 2015. The blood urea nitrogen (BUN) and creatinine values before radiation therapy were compared with last available follow-up values and analyzed with the clinical circumstances, including follow-up length, age at primary irradiation, nephrectomy, and radiation technique. The creatinine clearance was estimated using the Shull method. With a median follow-up period of 3.5years, none of the 266 patients studied developed a chronic renal insufficiency. For all patients, the creatinine level increased from 0.44 to 0.51mg/dL and the BUN increased from 10.53 to 15.52mg/dL. Three patients required antihypertensive medication. The patients who underwent intensity modulated radiation therapy did not experience increased creatinine levels during the follow-up period; however, they had a reduced median follow-up length compared with patients treated with anteroposterior/posteroanterior beams (4.7 vs 3.3years). A longer follow-up length was associated with an increased creatinine level. The preradiation therapy creatinine level increased with patient age, similar to that of the last follow-up creatinine level, suggesting that the changes in creatinine could likely be explained by physiologic increases associated with aging rather than radiation-induced renal damage. The creatinine clearance did not decrease in any circumstance. The present cohort had excellent renal outcomes after radiation therapy for neuroblastoma. No patient developed chronic renal insufficiency, and the small increases in BUN and creatinine we observed correlated, as expected, with increases in patient age. The results of the present study revealed a possible advantage for intensity modulated radiation therapy in preserving renal function; however, the follow-up length is a recognized confounding variable. The kidneys are vital structures to consider when planning radiation therapy for neuroblastoma patients, and we have found encouraging evidence that modern techniques to spare them in the setting of multiple treatment-related insults have been successful.

Head and neck target delineation using a novel PET automatic segmentation algorithm

PurposeTo evaluate the feasibility and impact of using a novel advanced PET auto-segmentation method in Head and Neck (H&N) radiotherapy treatment (RT) planning. MethodsATLAAS, Automatic decision Tree-based Learning Algorithm for Advanced Segmentation, previously developed and validated on pre-clinical data, was applied to 18F-FDG-PET/CT scans of 20 H&N patients undergoing Intensity Modulated Radiation Therapy. Primary Gross Tumour Volumes (GTVs) manually delineated on CT/MRI scans (GTVpCT/MRI), together with ATLAAS-generated contours (GTVpATLAAS) were used to derive the RT planning GTV (GTVpfinal). ATLAAS outlines were compared to CT/MRI and final GTVs qualitatively and quantitatively using a conformity metric. ResultsThe ATLAAS contours were found to be reliable and useful. The volume of GTVpATLAAS was smaller than GTVpCT/MRI in 70% of the cases, with an average conformity index of 0.70. The information provided by ATLAAS was used to grow the GTVpCT/MRI in 10 cases (up to 10.6mL) and to shrink the GTVpCT/MRI in 7 cases (up to 12.3mL). ATLAAS provided complementary information to CT/MRI and GTVpATLAAS contributed to up to 33% of the final GTV volume across the patient cohort. ConclusionsATLAAS can deliver operator independent PET segmentation to augment clinical outlining using CT and MRI and could have utility in future clinical studies.

The Influence of Treatment Energy on Cardiac Devices in Patients Undergoing Intensity Modulated Radiation Therapy (IMRT) for Prostate Cancer

We previously reported an increased risk of a cardiac device malfunction in patients undergoing IMRT for prostate cancer (DiBiase SJ, et al, IJROBP 81; 2011). In that report, high-energy photons were associated with device malfunction. We now review a subsequent cohort of prostate cancer patients who underwent IMRT utilizing low-energy photons to evaluate the influence of energy on cardiac device malfunction. Between 2009 and 2012, 955 patients underwent IMRT for prostate cancer at a single treatment center. Of these 955 patients, 44 patients (4.6%) had cardiac devices (pacemakers and defibrillators). All patients had their cardiac devices interrogated before treatment and at the completion of treatment. Some patients underwent IMRT using 18-MV (high-energy) photons and others underwent IMRT using 6MV (low-energy) photons. The initial group of patients treated from 2009-2011 (Group A) received both low and high-energy photons, and patients treated from 2011-2012 (Group B) received only low-energy photons based on a change in center protocol. A two proportion comparison test was used to check statistical significance of energy type on the development of device malfunction between Group A and Group B. Of the 24 cardiac device patients in Group A who were treated with IMRT utilizing both high-energy and low-energy photons, 6 patients (25%) experienced a device malfunction. Of the 24 patients in Group A, 8 patients received high-energy photons and 16 patients received low-energy photons. Of the 8 patients who received high-energy photons, 6 patients (75%) developed a cardiac malfunction. None of the 16 patients who received low-energy photons experienced a device malfunction. In a subsequent group (Group B) of 20 device patients who underwent low-energy IMRT between 2011 and 2012, none of the Group B patients experienced a cardiac device malfunction. A statistically significant difference at the 5% level was noted between low-energy and high-energy IMRT for developing a cardiac device malfunction (P value = 0.0005). The use of low-energy IMRT appears to reduce the risk of cardiac device malfunction in men undergoing treatment for prostate cancer. Energies above 6MV should be avoided in patients with cardiac devices undergoing IMRT.

Who will benefit most from hydrogel rectum spacer implantation in prostate cancer radiotherapy? A model-based approach for patient selection

Background and purposePrevious studies confirmed that implantable rectum spacers (IRS) decreased acute gastro-intestinal (GI) toxicity in a significant percentage of prostate cancer patients undergoing intensity modulated radiation therapy (IMRT). We developed decision rules based on clinical risk factors (CRFs) to select those patients who are expected to benefit most from IRS implantation. Materials and methodsFor 26 patients dose distributions with (IMRT+IRS) and without (IMRT−IRS) IRS were calculated. Validated nomograms based on CRFs and dosimetric criteria (anorectal V40Gy and V75Gy) were used to predict probabilities for grade 2–3 (G2–3) acute GI toxicity, G2–3 late rectal bleeding (LRB), G3 LRB, and G2–3 faecal incontinence (FI) for IMRT+IRS and IMRT−IRS. All permutations of CRFs were generated to identify most benefit scenarios (MBS) in which a predicted toxicity reduction of ⩾5% points in ⩾25% of the cohort was present due to IRS implantation. ResultsIMRT+IRS revealed a significant reduction in V40Gy (p=0.0357) and V75Gy (p<0.0001) relative to IMRT−IRS. For G2-3 acute GI toxicity and G2–3 LRB, the predicted toxicity rates decreased in 17/26 (65%) and 20/26 (77%) patients, and decision rules were derived for 22/32 (69%) and 12/64 (19%) MBS, respectively. From the decision rules, it follows that diabetes status has no impact on G2–3 acute toxicity, and in absence of pre-RT abdominal surgery, the implantation of an IRS is predicted to show no clinically relevant benefit for G2–3 LRB. ConclusionsProstate cancer patients who are expected to benefit most from IRS implantation can be identified prior to IMRT based on their CRFs profile.

Clinical Experience and Evaluation of Patient Treatment Verification With a Transit Dosimeter

To prospectively evaluate a protocol for transit dosimetry on a patient population undergoing intensity modulated radiation therapy (IMRT) and to assess the issues in clinical implementation of electronic portal imaging devices (EPIDs) for treatment verification. Fifty-eight patients were enrolled in the study. Amorphous silicon EPIDs were calibrated for dose and used to acquire images of delivered fields. Measured EPID dose maps were back-projected using the planning computed tomographic (CT) images to calculate dose at prespecified points within the patient and compared with treatment planning system dose offline using point dose difference and point γ analysis. The deviation of the results was used to inform future action levels. Two hundred twenty-five transit images were analyzed, composed of breast, prostate, and head and neck IMRT fields. Patient measurements demonstrated the potential of the dose verification protocol to model dose well under complex conditions: 83.8% of all delivered beams achieved the initial set tolerance level of ΔD of 0±5cGy or %ΔD of 0%±5%. Importantly, the protocol was also sensitive to anatomic changes and spotted that 3 patients from 20 measured prostate patients had undergone anatomic change in comparison with the planning CT. Patient data suggested an EPID-reconstructed versus treatment planning system dose difference action level of 0%±7% for breast fields. Asymmetric action levels were more appropriate for inversed IMRT fields, using absolute dose difference (-2±5cGy) or summed field percentage dose difference (-6%±7%). The invivo dose verification method was easy to use and simple to implement, and it could detect patient anatomic changes that impacted dose delivery. The system required no extra dose to the patient or treatment time delay and so could be used throughout the course of treatment to identify and limit systematic and random errors in dose delivery for patient groups.

Elective Nodal Irradiation and Patterns of Failure in Head and Neck Cancer After Primary Radiation Therapy

The delineation of elective clinical target volumes in head and neck cancer (HNC) is important; however, the extent of lymph node levels necessary to include is debated. A comprehensive analysis of recurrence patterns in a large cohort of patients with HNC was performed, with an emphasis on recurrence in the retropharyngeal region and level IB. From 2005 to 2012, 942 patients with oropharyngeal, hypopharyngeal, laryngeal or oral cavity carcinomas were curatively treated with primary radiation therapy. The median follow-up period was 34months, and 77% of the patients underwent intensity modulated radiation therapy. The retropharyngeal region was only routinely included in cases of involvement of the posterior pharynx wall and level IB only in cases of involvement of the oral cavity. In patients with regional recurrence, the anatomic site of the recurrence was assessed from the surgical descriptions or computed tomography scans and compared with the original radiation treatment plan (available from 2007 onward). The p16 status was available for 282 oropharynx carcinoma cases, with 65% p16-positive. Of the 942 patients, 376 (40%) developed recurrences: 228 (24.2%) local, 123 (13.1%) regional, and 109 (11.6%) distant. In 700 patients with available treatment plans, retropharyngeal and level IB recurrence was observed in 2 and 7 patients, respectively. Eight patients (1.1%) had recurrence in a lymph node level not included in their primary treatment plan. For oropharynx carcinoma, the locoregional control rate (90% vs 70%) but not distant control rate (92% vs 87%), was significantly better in the p16-positive than in the p16-negative patients. Although fewer recurrences developed in the p16-positive group, patients with recurrence of p16-positive tumors were more likely to develop recurrence in distant sites. Retropharyngeal or level IB recurrence after primary HNC radiation therapy is rare. Thus, inclusion of these regions in the elective treatment volumes should be limited to patients with involvement of the posterior pharyngeal wall or oral cavity.

Role of Surgical Versus Clinical Staging in Chemoradiated FIGO Stage IIB-IVA Cervical Cancer Patients—Acute Toxicity and Treatment Quality of the Uterus-11 Multicenter Phase III Intergroup Trial of the German Radiation Oncology Group and the Gynecologic Cancer Group

The Uterus-11 trial was designed to evaluate the role of surgical staging in patients with cervical cancer before primary chemoradiation therapy (CRT). The present report provides the toxicity data stratified by the treatment arm and technique. A total of 255 patients with carcinoma of the uterine cervix (International Federation of Gynecology and Obstetrics stage IIB-IVA) were randomized to either surgical staging followed by CRT (arm A) or clinical staging followed by CRT (arm B). Patients with para-aortic metastases underwent extended field radiation therapy (RT). Brachytherapy was mandatory. The present report presents the acute therapy-related toxicities stratified by treatment arm and radiation technique. A total of 240 patients were eligible (n=121 in arm A; n=119 in arm B). Of the 240 patients, 236 (98.3%) underwent external beam RT with a median total dose of 50.4 Gy. The mean treatment duration was 53 days. Of the patients, 60% underwent intensity modulated RT (IMRT). A total of 234 patients (97.5%) underwent chemotherapy, and 231 (96.3%) underwent brachytherapy, with a median single dose of 6 Gy covering the tumor to a median nominal total dose of 28 Gy. Treatment was well tolerated, with 0% grade ≥3 genitourinary and gastrointestinal toxicity, 6% grade 3 nausea, 3% grade 3 vomiting, and <2% grade 3 diarrhea. More patients after surgical staging experienced grade 2 anemia (54.3% in arm A vs 45.3% in arm B; P=.074) and grade 2 leukocytopenia (41.4% vs 31.6%; P=.56). Of the patients who received IMRT versus a 3-dimensional technique, 65.3% versus 33.7% presented with grade 2 anemia. Grade 3 gastrointestinal and grade 2 bladder toxicity were significantly reduced with the use of IMRT. The incidence and severity of acute therapy-related toxicity compared favorably with those from other randomized trials. Excellent adherence to treatment and treatment quality was achieved compared with patterns of care analyses. Surgical staging led to a doubled number of patients treated with extended field RT. The question of whether surgical staging is beneficial in the context of primary CRT requires further study.

First Experience With Real-Time EPID-Based Delivery Verification During IMRT and VMAT Sessions

Gantry-mounted megavoltage electronic portal imaging devices (EPIDs) have become ubiquitous on linear accelerators. WatchDog is a novel application of EPIDs, in which the image frames acquired during treatment are used to monitor treatment delivery in real time. We report on the preliminary use of WatchDog in a prospective study of cancer patients undergoing intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) and identify the challenges of clinical adoption. At the time of submission, 28 cancer patients (head and neck, pelvis, and prostate) undergoing fractionated external beam radiation therapy (24 IMRT, 4 VMAT) had ≥1 treatment fraction verified in real time (131 fractions or 881 fields). EPID images acquired continuously during treatment were synchronized and compared with model-generated transit EPID images within a frame time (∼0.1 s). A χ comparison was performed to cumulative frames to gauge the overall delivery quality, and the resulting pass rates were reported graphically during treatment delivery. Every frame acquired (500-1500 per fraction) was saved for postprocessing and analysis. The system reported the mean ± standard deviation in real time χ 91.1% ± 11.5% (83.6% ± 13.2%) for cumulative frame χ analysis with 4%, 4 mm (3%, 3 mm) criteria, global over the integrated image. A real-time EPID-based radiation delivery verification system for IMRT and VMAT has been demonstrated that aims to prevent major mistreatments in radiation therapy.

SU-C-210-06: Quantitative Evaluation of Dosimetric Effects Resulting From Positional Variations of Pancreatic Tumor Volumes

Purpose: The aim of this study is to quantify dosimetric effects resulting from variation in pancreatic tumor position assessed by bony anatomy and implanted fiducial markers Methods: Twelve pancreatic cancer patients were retrospectively analyzed for this study. All patients received modulated arc therapy (VMAT) treatment using fiducial-based Image Guided Radiation Therapy (IGRT) to the intact pancreas. Using daily orthogonal kV and/or Cone beam CT images, the shift needed to co-register the daily pre-treatment images to reference CT from fiducial to bone (Fid-Bone) were recorded as Left-Right (LR), Anterior-Posterior (AP) and Superior-Inferior (SI). The original VMAT plan iso-center was shifted based on KV bone matching positions at 5 evenly spaced fractions. Dose coverage of the planning target volumes (PTVs) (V100%), mean dose to liver, kidney and stomach/duodenum were assessed in the modified plans. Results: A total of 306 fractions were analyzed. The absolute fiducial-bone positional shifts were greatest in the SI direction, (AP = 2.7 ± 3.0, LR = 2.8 ± 2.8, and SI 6.3 ± 7.9 mm, mean ± SD). The V100% was significantly reduced by 13.5%, (Fid-Bone = 95.3 ± 2.0 vs. 82.3 ± 11.8%, p=0.02). This varied widely among patients (Fid-Bone V100% Range = 2–60%), where 33% ofmore » patients had a reduction in V100% of more than 10%. The impact on OARs was greatest to the liver (Fid-Bone= 14.6 vs. 16.1 Gy, 10%), and stomach, (Fid-Bone = 23.9 vx. 25.5 Gy, 7%), however was not statistically significant (p=0.10 both). Conclusion: Compared to matching by fiducial markers, matching by bony anatomy would have substantially reduced the PTV coverage by 13.5%. This reinforces the importance of online position verification based on fiducial markers. Hence, implantation of fiducial markers is strongly recommended for pancreatic cancer patients undergoing intensity modulated radiation therapy treatments.« less

Elevated pretreatment plasma D-dimer levels and platelet counts predict poor prognosis in pancreatic adenocarcinoma.

This retrospective study was conducted to evaluate the prognostic significance of the preoperative plasma D-dimer levels and platelet counts in patients with pancreatic adenocarcinoma. A total of 168 consecutive locally advanced pancreatic adenocarcinoma patients who underwent intensity modulated radiation therapy with or without chemotherapy were enrolled in this study. Plasma D-dimer levels were measured by a latex-enhanced immunoturbidimetric assay. Of the 168 patients enrolled, 106 patients were males and 62 patients were females. There was significant difference between plasma D-dimer levels and clinical responses (P=0.001). The 1-year, 2-year, and 3-year cumulative overall survival rates were 50.6%, 15.0%, and 4.9%, respectively. Plasma D-dimer levels (P<0.001) and platelet counts (P=0.010) were significantly related with overall survival in univariate analysis. The Cox proportional hazards regression indicated that plasma D-dimer levels (P=0.028), platelet counts (P=0.004), and treatment response (P<0.001) were independent prognostic factors for overall survival. Elevated pretreatment plasma D-dimer levels and platelet counts predict poor prognosis in pancreatic adenocarcinoma.

Evaluation of Parotid Gland Dose Rate following Intensity Modulated Radiation Therapy in Head and Neck Cancer

The objective of this study was to identify the effects of dose rate change when planning intensity modulated radiation therapy. The study involved 10 patients with nasopharyngeal carcinoma undergoing intensity modulated radiation therapy among patients with head and neck cancer. Computed tomography images with 3 mm thickness were acquired under the same conditions for all patients, and Eclipse software was used for the treatment planning system. As for the treatment regimen, with an energy of 6 MV, eight irradiation planes, and equal dose volumes were used; different dose rates of 300 monitor unit/min, 400 monitor unit/min, and 500 monitor unit/min were applied, respectively. The mean dose on the parotid gland was calculated through three treatment regimens, and was analyzed using the mean values of 10 patients. The dose in the parotid gland site was verified by use of a 2D diode array. The total monitor unit and irradiation time were compared. As the results of this study in connection to the parotid gland mean dose according to the dose rate change, when the dose volume was changed from 300 monitor unit/min to 400 monitor unit/min and 500 monitor unit/min, the mean dose was increased by 0.8% and 2.0%, and the total monitor unit was also increased by mean 5.4% and 10.6%. Dosimetry of the parotid gland performed by 2D diode array revealed an increasing trend; the difference in the total irradiation time was about 1–2 min and there was no significant change by the dose rate. In conclusion, if applying adequate dose rates set at the time to establish the intensity modulated radiation therapy regimen in the head and neck cancer, it is considered to enable post-radiotherapy adverse effects of the parotid glands.

Impact of Dose to the Bladder Trigone on Long-Term Urinary Function After High-Dose Intensity Modulated Radiation Therapy for Localized Prostate Cancer

To determine the potential association between genitourinary (GU) toxicity and planning dose-volume parameters for GU pelvic structures after high-dose intensity modulated radiation therapy in localized prostate cancer patients. A total of 268 patients who underwent intensity modulated radiation therapy to a prescribed dose of 86.4Gy in 48 fractions during June 2004-December 2008 were evaluated with the International Prostate Symptom Score (IPSS) questionnaire. Dose-volume histograms of the whole bladder, bladder wall, urethra, and bladder trigone were analyzed. The primary endpoint for GU toxicity was an IPSS sum increase ≥10 points over baseline. Univariate and multivariate analyses were done by the Kaplan-Meier method and Cox proportional hazard models, respectively. Median follow-up was 5years (range, 3-7.7years). Thirty-nine patients experienced an IPSS sum increase ≥10 during follow-up; 84% remained event free at 5years. After univariate analysis, lower baseline IPSS sum (P=.006), the V90 of the trigone (P=.006), and the maximal dose to the trigone (P=.003) were significantly associated with an IPSS sum increase ≥10. After multivariate analysis, lower baseline IPSS sum (P=.009) and increased maximal dose to the trigone (P=.005) remained significantly associated. Seventy-two patients had both a lower baseline IPSS sum and a higher maximal dose to the trigone and were defined as high risk, and 68 patients had both a higher baseline IPSS sum and a lower maximal dose to the trigone and were defined as low risk for development of an IPSS sum increase ≥10. Twenty-one of 72high-risk patients (29%) and 5 of 68 low-risk patients (7%) experienced an IPSS sum increase ≥10 (P=.001; odds ratio 5.19). The application of hot spots to the bladder trigone was significantly associated with relevant changes in IPSS during follow-up. Reduction of radiation dose to the lower bladder and specifically the bladder trigone seems to be associated with a reduction in late GU toxicity.

The Residual Setup Errors of Different IGRT Alignment Procedures for Head and Neck IMRT and the Resulting Dosimetric Impact

To assess residual setup errors during head and neck radiation therapy and the resulting consequences for the delivered dose for various patient alignment procedures. Megavoltage cone beam computed tomography (MVCBCT) scans from 11 head and neck patients who underwent intensity modulated radiation therapy were used to assess setup errors. Each MVCBCT scan was registered to its reference planning kVCT, with seven different alignment procedures: automatic alignment and manual registration to 6 separate bony landmarks (sphenoid, left/right maxillary sinuses, mandible, cervical 1 [C1]-C2, and C7-thoracic 1 [T1] vertebrae). Shifts in the different alignments were compared with each other to determine whether there were any statistically significant differences. Then, the dose distribution was recalculated on 3 MVCBCT images per patient for every alignment procedure. The resulting dose-volume histograms for targets and organs at risk (OARs) were compared to those from the planning kVCTs. The registration procedures produced statistically significant global differences in patient alignment and actual dose distribution, calling for a need for standardization of patient positioning. Vertically, the automatic, sphenoid, and maxillary sinuses alignments mainly generated posterior shifts and resulted in mean increases in maximal dose to OARs of >3% of the planned dose. The suggested choice of C1-C2 as a reference landmark appears valid, combining both OAR sparing and target coverage. Assuming this choice, relevant margins to apply around volumes of interest at the time of planning to take into account for the relative mobility of other regions are discussed. Use of different alignment procedures for treating head and neck patients produced variations in patient setup and dose distribution. With concern for standardizing practice, C1-C2 reference alignment with relevant margins around planning volumes seems to be a valid option.

Normal Tissue Complication Probability Analysis of Acute Gastrointestinal Toxicity in Cervical Cancer Patients Undergoing Intensity Modulated Radiation Therapy and Concurrent Cisplatin

To test the hypothesis that increased bowel radiation dose is associated with acute gastrointestinal (GI) toxicity in cervical cancer patients undergoing concurrent chemotherapy and intensity-modulated radiation therapy (IMRT), using a previously derived normal tissue complication probability (NTCP) model. Fifty patients with Stage I-III cervical cancer undergoing IMRT and concurrent weekly cisplatin were analyzed. Acute GI toxicity was graded using the Radiation Therapy Oncology Group scale, excluding upper GI events. A logistic model was used to test correlations between acute GI toxicity and bowel dosimetric parameters. The primary objective was to test the association between Grade ≥2 GI toxicity and the volume of bowel receiving ≥45 Gy (V(45)) using the logistic model. Twenty-three patients (46%) had Grade ≥2 GI toxicity. The mean (SD) V(45) was 143 mL (99). The mean V(45) values for patients with and without Grade ≥2 GI toxicity were 176 vs. 115 mL, respectively. Twenty patients (40%) had V(45) >150 mL. The proportion of patients with Grade ≥2 GI toxicity with and without V(45) >150 mL was 65% vs. 33% (p = 0.03). Logistic model parameter estimates V50 and γ were 161 mL (95% confidence interval [CI] 60-399) and 0.31 (95% CI 0.04-0.63), respectively. On multivariable logistic regression, increased V(45) was associated with an increased odds of Grade ≥2 GI toxicity (odds ratio 2.19 per 100 mL, 95% CI 1.04-4.63, p = 0.04). Our results support the hypothesis that increasing bowel V(45) is correlated with increased GI toxicity in cervical cancer patients undergoing IMRT and concurrent cisplatin. Reducing bowel V(45) could reduce the risk of Grade ≥2 GI toxicity by approximately 50% per 100 mL of bowel spared.

放射線治療部門におけるスタッフ・新人技師による患者Setup Errorの統計学的有意差解析

We verified the setup error (SE) in two persons' radiation therapist's team, which consist of staff and new face. We performed the significance test for SE by the staff group and the new face group.One group consists of four staff therapists with at least 5 to 30 years of experience. The other group consists of new face radiation therapists that have 1 to 1.5 years of experience. Analyzed were 53 patients diagnosed with pelvic cancer (seven patients who underwent 3 dimensional conformal radiation therapy (3DCRT) and 46 patients who underwent intensity modulated radiation therapy (IMRT). Image verification was 1460 times. It was performed through setup verification by cone beam computed tomography (CBCT), and we measured SE of four directions (lateral, long, vertical, 3D). We performed the student's t-test to get the difference of the average error between the staff group and the new face group.The results of significance tests show that there is no difference between SE in the staff group and the new face group in radiotherapy.

SU‐E‐T‐34: Time Series Analysis of Skin Reactions during Heck and Neck IMRT

Purpose: To quantitatively characterize the time sequence of skin erythema in head and neck patients undergoing intensity modulated radiation therapy (IMRT) treatments using optical reflectance spectroscopy. The overall goal is to identify patients who will develop extreme skin responses earlier than is possible by visual inspection alone. Methods: Ten (10) patients undergoing IMRT for the treatment of head and neck cancers were followed throughout the course of their intervention. Daily spectral skin reflectance measurements were made in order to track changes in the tissue optical properties. Weekly thermoluminescent detector (TLD) readings were performed in the measurement area to verify the dose calculated by the treatment planning system. Patients also completed a weekly questionnaire on factors that may have affected their skin reaction, and were visually inspected by a radiation oncologist.Results: The data were fit by a 2‐component principle component analysis (PCA) model. The preliminary results show that absorbed dose is the largest contributor to changes in the spectral reflectance and that those changes are seen primarily at wavelengths above 600 nm. Differences among patient skin responses were seen and accounted for in the model Conclusions: The PCA model indicates that it may be possible to predict a patientˈs spectral skin reflectance measurement on the final day of treatment given an initial spectrum and the dose. Therefore, further analysis of the data may yield a method of determining patient reactions before visible signs are detected.Partial funding through Varian, Inc. and the Natural Sciences and Engineering Research Council of Canada.

Normal Tissue Complication Probability Analysis of Acute Gastrointestinal Toxicity in Cervical Cancer Patients Undergoing Intensity Modulated Radiation Therapy and Concurrent Cisplatin

Previous studies have identified correlations between acute gastrointestinal (GI) toxicity and the volume of bowel receiving 45 Gy (V45) in women undergoing intensity modulated radiation therapy (IMRT) for gynecologic cancers. The applicability of existing NTCP models to women undergoing IMRT with concurrent cisplatin, however, is unclear; therefore, we applied NTCP analysis to a cohort of cervical cancer patients undergoing concurrent chemotherapy and IMRT. Fifty patients with FIGO stage IB-IIIB cervical cancer received either definitive (n = 38) or adjuvant (n = 12) IMRT (45-50.4 Gy/fraction) and concurrent weekly cisplatin (40 mg/m2) between 2006 and 2010. Bowel V45 was measured in ccs. Acute GI toxicity was graded using the Radiation Therapy Oncology Group scale, excluding nausea and/or emesis. Both logistic regression and Logit models (i.e., Probability of Toxicity = 1 / (1 + (V / V45)k), where V and k are fitted parameters), were used to estimate correlations between acute GI toxicity and bowel V45. Forty-six percent of patients had grade ≥ 2 GI toxicity. The mean (SD) V45 was 143 cc (99). The mean V45 for patients with and without grade ≥ 2 toxicity were 176 vs. 115 cc, respectively. Forty percent of patients had V45 > 150 cc. Grade ≥ 2 GI toxicity for patients with and without V45 > 150 cc was 65% vs. 33% (chi-square, p = 0.027). On logistic regression adjusting for age, the odds ratio estimate for V45, per 100 cc, was 2.19 (95% CI 1.04-4.63, p = 0.044). With the Logit model, parameter estimates V and k were 144 cc (95% CI, 59-231) and 1.06 (95% CI, -0.07 - 2.20), respectively. Our results support the hypothesis that increasing bowel V45 is correlated with increased GI toxicity in cervical cancer patients undergoing IMRT and concurrent cisplatin. Estimates from the Logit model agreed fairly well with those of previous studies. Reducing bowel V45 by 100 cc could reduce the risk of grade ≥ 2 GI toxicity by approximately 50%. Further studies in larger samples are needed to validate the previously derived NTCP model in this population.

Head and Neck Cancer (HNC) Patients Undergoing Intensity Modulated Radiation Therapy (IMRT) Have Fewer Subsequent Days of Hospitalization (DOH) than Do Patients Undergoing Conventional Radiation Therapy (CRT) in the SEER-Medicare Linked Database

Treatment with IMRT has demonstrated to improve the quality of life and salivary function of patients with HNC compared to CRT. However, there is little other information about the comparative effectiveness of IMRT versus CRT for HNC. Therefore, we used the National Cancer Institute's Surveillance, Epidemiology and End Results - Medicare linked database for patients over the age of 65 treated from 2002-2005 to analyze DOH for patients who received IMRT or CRT for HNC.

SU‐GG‐T‐175: Dosimetric Evaluation of the Use of Air or Water Filled Endorectal Balloons for Prostate IMRT Patients

Purpose: Prostate cancer patients undergoing intensity modulated radiation therapy (IMRT) are typically treated without endorectal balloon in our clinic. On occasion, there is a clinical need to use endorectal balloons. The purpose of this study is to evaluate the dosimetric advantages and disadvantages of using water or air in endorectal balloons. Materials and Methods: In an IRB approved protocol, water filled endorectal balloons were inserted into the rectum of 7 prostate patients. The patients were imaged in the supine position with full bladder and endorectal balloon. The Pinnacle treatment planning system (TPS) was used for planning. The prostate, seminal vesicles, rectum, anterior rectal wall and bladder were contoured on all patients. A second plan was generated by converting the water into air by overriding the density of the water. Dose distributions and dose volume histograms were evaluated. To verify Pinnacle dose computation at the rectum‐prostate (air‐tissue) interface, the treatment plans were recomputed using Monte Carlo for the air balloons. Monitor units required to deliver the two plans were also compared. Results: Mean dosimetric parameters for air vs water were; Rectum: V70 ‐ 9.7% vs 11.6%; V60 ‐ 17.3% vs 17.2%; V40; V40 ‐ 34.7% vs 30.9%; Bladder: V70 ‐ 6.5% vs 6.4%; Maximum dose: 8003 cGy vs 7953 cGy. Mean monitor units for the air vs water plans were 803 MU vs 710 MU. Conclusions: The dosimetric parameters for rectum and bladder for air and water balloons were similar (&lt;5%) indicating that either could potentially be used. The water‐filled balloon plans required significantly less MU's as compared to the air balloons and required less planning time to meet dosimetric criteria and constraints when compared to air‐filled endorectal balloons. Monte Carlo calculations agreed better with Pinnacle water balloon plans than air balloon plans.