Clinical Tumor Volume Research Articles

Advantage of PET/CT in Target Delineation of MRI-negative Cervical Lymph Nodes In Intensity-Modulated Radiation Therapy Planning for Nasopharyngeal Carcinoma.

Introduction: In intensity-modulated radiation therapy (IMRT) planning for nasopharyngeal carcinoma (NPC), cervical lymph nodes (CLNs) that appear negative on magnetic resonance imaging (MRI) scans can be difficult to target. The purpose of this study was to assess the advantage of 18F-fluorodeoxyglucose positron emission tomography with computed tomography (18F-FDG PET/CT) for distinguishing MRI-negative CLNs and the effect of 18F-FDG PET/CT on diagnosis, target delineation, and dose prescription in IMRT planning for NPC.Methods: Thirty-five NPC patients with 37 MRI-negative CLNs underwent 18F-FDG PET/CT imaging before treatment. Ultrasonography-guided fine-needle aspiration cytology (USgFNAC) was performed to examine the pathology of CLNs. The 18F-FDG PET/CT and cytopathological results were compared, and the diagnostic accuracy of 18F-FDG PET/CT was calculated. The cytopathologically confirmed CLNs were delineated and treated as the gross tumor volume of lymph nodes (denoted as GTVnd).Results: Nineteen of the 37 MRI-negative CLNs were positive on 18F-FDG PET/CT, and metastasis was confirmed by USgFNAC in 16 CLNs. Of the remaining 18 18F-FDG PET/CT-negative lymph nodes, metastasis was confirmed in one. The diagnostic accuracy, sensitivity, and specificity of 18F-FDG PET/CT were 89.2%, 94.1%, and 85.0%, respectively. The positive and negative predictive values were 84.2% and 94.4%, respectively. With a median follow-up of 48.3 months, no relapse was observed among the 18F-FDG PET/CT-positive CLNs with metastasis confirmed by USgFNAC and treated as GTVnd.Conclusion: 18F-FDG PET/CT had high accuracy, sensitivity, and specificity for distinguishing MRI-negative CLNs. 18F-FDG PET/CT-positive CLNs could reasonably be categorized as high-risk clinical tumor volume in IMRT planning for NPC.

Dosimetric Implications of Residual Tracking Errors During Robotic SBRT of Liver Metastases

Although the metric precision of robotic stereotactic body radiation therapy in the presence of breathing motion is widely known, we investigated the dosimetric implications of breathing phase-related residual tracking errors. In 24 patients (28 liver metastases) treated with the CyberKnife, we recorded the residual correlation, prediction, and rotational tracking errors from 90 fractions and binned them into 10 breathing phases. The average breathing phase errors were used to shift and rotate the clinical tumor volume (CTV) and planning target volume (PTV) for each phase to calculate a pseudo 4-dimensional error dose distribution for comparison with the original planned dose distribution. The median systematic directional correlation, prediction, and absolute aggregate rotation errors were 0.3mm (range, 0.1-1.3mm), 0.01mm (range, 0.00-0.05mm), and 1.5° (range, 0.4°-2.7°), respectively. Dosimetrically, 44%, 81%, and 92% of all voxels differed by less than 1%, 3%, and 5% of the planned local dose, respectively. The median coverage reduction for the PTV was 1.1% (range in coverage difference, -7.8% to +0.8%), significantly depending on correlation (P=.026) and rotational (P=.005) error.With a 3-mm PTV margin, the median coverage change for the CTV was 0.0% (range, -1.0% to +5.4%), not significantly depending on any investigated parameter. In 42% of patients, the 3-mm margin did not fully compensate for the residual tracking errors, resulting in a CTV coverage reduction of 0.1% to 1.0%. For liver tumors treated with robotic stereotactic body radiation therapy, a safety margin of 3mm is not always sufficient to cover all residual tracking errors. Dosimetrically, this translates into only small CTV coverage reductions.

Survival and Control Prognosticators of Recurrent Gynecological Malignancies of the Pelvis and Para-aortic Region Treated with Stereotactic Body Radiation Therapy.

To define prognostic factors associated with improved survival and local control (LC) for gynecologic cancer recurrences limited to the pelvis and para-aortic (PA) region using stereotactic body radiation therapy (SBRT). Between 2/2008 and 7/2014, 30 women (35 targets) with pelvic or PA recurrence of endometrioid (n = 12), cervical (n = 11), ovarian (n = 3), uterine-serous (n = 2), or carcinosarcoma (n = 2) cancer were treated with SBRT. Eleven recurrences were located in the central pelvis, 11 along the pelvic sidewall (PSW), and 13 in the PA region. Five-year survival for all patients was 42% with a median survival of 43.4 months. Multivariate analysis revealed better performance status (PS), and smaller clinical tumor volume was significant for improved survival (p < 0.05). SBRT is a local therapy for recurrent gynecological malignancies in the pelvis and PA region with curative potential. SBRT is especially effective for LC when targeting PSW or PA recurrence and for patients with a cervical/endometrioid uterine primary. Survival is improved for patients with better PS and smaller recurrence volume prior to SBRT.

Consensus guidelines for postoperative stereotactic body radiation therapy for spinal metastases: results of an international survey.

OBJECTIVE Although postoperative stereotactic body radiation therapy (SBRT) for spinal metastases is increasingly performed, few guidelines exist for this application. The purpose of this study is to develop consensus guidelines to promote safe and effective treatment for patients with spinal metastases. METHODS Fifteen radiation oncologists and 5 neurosurgeons, representing 19 centers in 4 countries and having a collective experience of more than 1300 postoperative spine SBRT cases, completed a 19-question survey about postoperative spine SBRT practice. Responses were defined as follows: 1) consensus: selected by ≥ 75% of respondents; 2) predominant: selected by 50% of respondents or more; and 3) controversial: no single response selected by a majority of respondents. RESULTS Consensus treatment indications included: radioresistant primary, 1-2 levels of adjacent disease, and previous radiation therapy. Contraindications included: involvement of more than 3 contiguous vertebral bodies, ASIA Grade A status (complete spinal cord injury without preservation of motor or sensory function), and postoperative Bilsky Grade 3 residual (cord compression without any CSF around the cord). For treatment planning, co-registration of the preoperative MRI and postoperative T1-weighted MRI (with or without gadolinium) and delineation of the cord on the T2-weighted MRI (and/or CT myelogram in cases of significant hardware artifact) were predominant. Consensus GTV (gross tumor volume) was the postoperative residual tumor based on MRI. Predominant CTV (clinical tumor volume) practice was to include the postoperative bed defined as the entire extent of preoperative tumor, the relevant anatomical compartment and any residual disease. Consensus was achieved with respect to not including the surgical hardware and incision in the CTV. PTV (planning tumor volume) expansion was controversial, ranging from 0 to 2 mm. The spinal cord avoidance structure was predominantly the true cord. Circumferential treatment of the epidural space and margin for paraspinal extension was controversial. Prescription doses and spinal cord tolerances based on clinical scenario, neurological compromise, and prior overlapping treatments were controversial, but reasonable ranges are presented. Fifty percent of those surveyed practiced an integrated boost to areas of residual tumor and density override for hardware within the beam path. Acceptable PTV coverage was controversial, but consensus was achieved with respect to compromising coverage to meet cord constraint and fractionation to improve coverage while meeting cord constraint. CONCLUSIONS The consensus by spinal radiosurgery experts suggests that postoperative SBRT is indicated for radioresistant primary lesions, disease confined to 1-2 vertebral levels, and/or prior overlapping radiotherapy. The GTV is the postoperative residual tumor, and the CTV is the postoperative bed defined as the entire extent of preoperative tumor and anatomical compartment plus residual disease. Hardware and scar do not need to be included in CTV. While predominant agreement was reached about treatment planning and definition of organs at risk, future investigation will be critical in better understanding areas of controversy, including whether circumferential treatment of the epidural space is necessary, management of paraspinal extension, and the optimal dose fractionation schedules.

Development of a Novel Deep Learning Algorithm for Autosegmentation of Clinical Tumor Volume and Organs at Risk in Head and Neck Radiation Therapy Planning

Development of a Novel Deep Learning Algorithm for Autosegmentation of Clinical Tumor Volume and Organs at Risk in Head and Neck Radiation Therapy Planning

The effects of new or worsened postoperative neurological deficits on survival of patients with glioblastoma.

OBJECTIVE An increased extent of resection (EOR) has been shown to improve overall survival of patients with glioblastoma (GBM) but has the potential for causing a new postoperative neurological deficit. To investigate the impact of surgical neurological morbidity on survival, the authors performed a retrospective analysis of the clinical data from patients with GBM to quantify the impact of a new neurological deficit on the survival benefit achieved with an increased EOR. METHODS The data from all GBM patients who underwent resection at the University of Florida from 2010 to 2015 with postoperative imaging within 72 hours of surgery were included in the study. Retrospective analysis was performed on clinical outcomes and tumor volumes determined on postoperative and follow-up imaging examinations. RESULTS Overall, 115 patients met the inclusion criteria for the study. Tumor volume at the time of presentation was a median of 59 cm3 (enhanced on T1-weighted MRI scans). The mean EOR (± SD) was 94.2% ± 8.7% (range 59.9%-100%). Almost 30% of patients had a new postoperative neurological deficit, including motor weakness, sensory deficits, language difficulty, visual deficits, confusion, and ataxia. The neurological deficits had resolved in 41% of these patients on subsequent follow-up examinations. The median overall survival was 13.1 months (95% CI 10.9-15.2 months). Using a multipredictor Cox model, the authors observed that increased EOR was associated with improved survival except for patients with smaller tumor volumes (≤ 15 cm3). A residual volume of 2.5 cm3 or less predicted a favorable overall survival. Developing a postoperative neurological deficit significantly affected survival (9.2 months compared with 14.7 months, p = 0.02), even if the neurological deficit had resolved by the first follow-up. However, there was a trend of improved survival among patients with resolution of a neurological deficit by the first follow-up compared with patients with a permanent neurological deficit. Any survival benefit from achieving a 95% EOR was abrogated by the development of a new neurological deficit postoperatively. CONCLUSIONS Developing a new neurological deficit after resection of GBM is associated with a decrease in overall survival. A careful balance between EOR and neurological compromise needs to be taken into account to reduce the likelihood of neurological morbidity from surgery.

Methods for Reducing Normal Tissue Complication Probabilities in Oropharyngeal Cancer: Dose Reduction or Planning Target Volume Elimination

Strategies to reduce the toxicities of head and neck radiation (ie, dysphagia [difficulty swallowing] and xerostomia [dry mouth]) are currently underway. However, the predicted benefit of dose and planning target volume (PTV) reduction strategies is unknown. The purpose of the present study was to compare the normal tissue complication probabilities (NTCP) for swallowing and salivary structures in standard plans (70Gy [P70]), dose-reduced plans (60Gy [P60]), and plans eliminating the PTV margin. A total of 38 oropharyngeal cancer (OPC) plans were analyzed. Standard organ-sparing volumetric modulated arc therapy plans (P70) were created and then modified by eliminating the PTVs and treating the clinical tumor volumes (CTVs) only (C70) or maintaining the PTV but reducing the dose to 60Gy (P60). NTCP dose models for the pharyngeal constrictors, glottis/supraglottic larynx, parotid glands (PGs), and submandibular glands (SMGs) were analyzed. The minimal clinically important benefit was defined as a mean change in NTCP of >5%. The P70 NTCP thresholds and overlap percentages of the organs at risk with the PTVs (56-59Gy, vPTV56) were evaluated to identify the predictors for NTCP improvement. With the P60 plans, only the ipsilateral PG (iPG) benefited (23.9% vs 16.2%; P<.01). With the C70 plans, only the iPG (23.9% vs 17.5%; P<.01) and contralateral SMG (cSMG) (NTCP 32.1% vs 22.9%; P<.01) benefited. An iPG NTCP threshold of 20% and 30% predicted NTCP benefits for the P60 and C70 plans, respectively (P<.001). A cSMG NTCP threshold of 30% predicted for an NTCP benefit with the C70 plans (P<.001). Furthermore, for the iPG, a vPTV56 >13% predicted benefit with P60 (P<.001) and C70 (P=.002). For the cSMG, a vPTV56 >22% predicted benefit with C70 (P<.01). PTV elimination and dose-reduction lowered the NTCP of the iPG, and PTV elimination lowered the NTCP of the cSMG. NTCP thresholds and the percentage of overlap of the PTV with organs at risk can predict which patients will benefit and inform future clinical trial design.

WE‐AB‐207B‐04: A Preliminary Investigation of Indicators for Treatment Outcomes of CT Guided Cervical Cancer Brachytherapy

Purpose:To identify indicators for recurrence in cervical cancer patients treated with high‐dose‐rate brachytherapy (HDR‐BT).Methods:A total of 37 biopsy proven uterine cervical cancer patients of stage IB‐IVA treated between 2011 and 2015 were included in this study. All patients were treated with 37.8–52.2Gy of external beam radiotherapy (EBRT) plus 5 × 5.0–6.5Gy of HDR‐BT. Patient age, standard deviation of high‐risk clinical tumor volume (HR‐CTVSD) collected throughout HDR‐BT, and D90 (EQD2, α/β=10Gy) of the HR‐CTV were investigated as potential indicators for local/distant recurrence using ROC analysis. The optimal cutoff value was identified through the Youden index and was subsequently used to obtain a group assignment for all patients. Another two comparing groups were defined per evidence of post‐EBRT tumor shrinkage based on the pre‐HDR MR scan. Kaplan‐Meier curves were generated for recurrence‐free proportions for comparing groups where time was measured from the final HDR treatment date to the date of the final follow‐up exam and compared through Cox regression.Results:Patients had a median follow‐up of 12 months, where 16% had local pelvic recurrence and 16% had distant recurrence. HR‐CTVSD was identified as a statistically significant indicator for recurrence (AUC=0.802, p=0.007) compared to D90 (AUC=0.655, p=0.167) and patient age (AUC=0.683, p=0.103). HR‐CTVSD of 6.26cc was chosen as the optimal cutoff value, which was used as the basis for patient group assignment. Patients with HR‐CTVSD&gt;6.26cc had a hazard ratio of 3.92 (95% CI‐1.37, 11.24; p=0.011) for recurrence compared to HRCTVSD≤ 6.26cc. Patients without evidence of post‐EBRT tumor shrinkage compared to those with had a hazard ratio of 4.28 (95% CI‐1.14, 16.15; p=0.032) for recurrence.Conclusion:HR‐CTVSD was identified as an indicator for recurrence and an optimal value of 6.26cc was established in our study. In addition, patients without evidence of post‐EBRT tumor shrinkage demonstrated an increased recurrence rate.

SU‐C‐202‐02: A Comprehensive Evaluation of Adaptive Daily Planning for Cervical Cancer HDR Brachytherapy

Purpose:To evaluate adaptive daily planning for cervical cancer patients who underwent high‐dose‐rate intra‐cavitary brachytherapy (HDR‐ICBT).Methods:This study included 22 cervical cancer patients who underwent 5 fractions of HDR ICBT. Regions of interest (ROIs) including high‐risk clinical tumor volume (HR‐CTV) and organs‐at‐risk (OARs) were manually contoured on daily CT images. All patients were treated with adaptive daily plans, which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans were retrospectively generated by applying the first treatment fraction's dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similarity metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity score (JRARM) was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between inter‐fractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon Signed Rank Tests were used to assess adaptive daily plans and single plans by comparing EQD2 D2cc (α/β=3) for OARs.Results:For inter‐fractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM and DSC similarity metrics. Comparisons between paired ROIs showed differences in JRARM scores and DSCs at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found that adaptive daily planning provided lower EQD2 D2cc of OARs than single planning, specifically for the sigmoid (p=0.015).Conclusion:Substantial inter‐fractional organ motion can occur during HDR‐BT, which may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning.

SU‐F‐T‐37: Dosimetric Evaluation of Planned Versus Decay Corrected Treatment Plans for the Treatment of Tandem‐Based Cervical HDR Brachytherapy

Purpose:This study evaluated dosimetric parameters for actual treatment plans versus decay corrected treatment plans for cervical HDR brachytherapy.Methods:125 plans of 25 patients, who received 5 fractions of HDR brachytherapy, were evaluated in this study. Dose was prescribed to point A (ICRU‐38) and High risk clinical tumor volume (HR‐CTV) and organs at risk (OAR) were, retrospectively, delineated on original CT images by treating physician. First HDR plan was considered as reference plan and decay correction was applied to calculate treatment time for subsequent fractions, and was applied, retrospectively, to determine point A, HR‐CTV D90, and rectum and bladder doses.Results:The differences between mean point A reference doses and the point A doses of the plans computed using decay times were found to be 1.05%±0.74% (−2.26% to 3.26%) for second fraction; −0.25%±0.84% (−3.03% to 3.29%) for third fraction; 0.04%±0.70% (−2.68% to 2.56%) for fourth fraction and 0.30%±0.81% (−3.93% to 2.67%) for fifth fraction. Overall mean point A dose difference, for all fractions, was 0.29%±0.38% (within ± 5%). Mean rectum and bladder dose differences were calculated to be −3.46%±0.12% and −2.47%±0.09%, for points, respectively, and −1.72%±0.09% and −0.96%±0.06%, for D2cc, respectively. HR‐CTV D90 mean dose difference was found to be −1.67% ± 0.11%. There was no statistically significant difference between the reference planned point A doses and that calculated using decay time to the subsequent fractions (p&lt;0.05).Conclusion:This study reveals that a decay corrected treatment will provide comparable dosimetric results and can be utilized for subsequent fractions of cervical HDR brachytherapy instead of actual treatment planning. This approach will increase efficiency, decrease workload, reduce patient observation time between applicator insertion and treatment delivery. This would be particularly useful for institutions with limited resources or large patient populations with limited access to care.

Variations in CT determination of target volume with active breath co-ordinate in radiotherapy for post-operative gastric cancer.

Objective:To investigate interobserver and inter-CT variations in using the active breath co-ordinate technique in the determination of clinical tumour volume (CTV) and normal organs in post-operative gastric cancer radiotherapy.Methods:Ten gastric cancer patients were enrolled in our study, and four radiation oncologists independently determined the CTVs and organs at risk based on the CT simulation data. To determine interobserver and inter-CT variation, we evaluated the maximum dimensions, derived volume and distance between the centres of mass (CMs) of the CTVs. We assessed the reliability in CTV determination among the observers by conformity index (CI).Results:The average volumes ± standard deviation (cm3) of the CTV, liver, left kidney and right kidney were 674 ± 138 (range, 332–969), 1000 ± 138 (range, 714–1320), 149 ± 13 (range, 104–183) and 141 ± 21 (range, 110–186) cm3, respectively. The average inter-CT distances between the CMs of the CTV, liver, left kidney and right kidney were 0.40, 0.56, 0.65 and 0.6 cm, respectively; the interobserver values were 0.98, 0.53, 0.16 and 0.15 cm, respectively.Conclusions:In the volume size of CTV for post-operative gastric cancer, there were significant variations among multiple observers, whereas there was no variation between different CTs. The slices in which variations more likely occur were the slices of the lower verge of the hilum of the spleen and porta hepatis, then the paraoesophageal lymph nodes region and abdominal aorta, and the inferior vena cava, and the variation in the craniocaudal orientation from the interobserver was more predominant than that from inter-CT.Advances in knowledge:First, this is the first study to evaluate the interobserver and inter-CT variations in the determination of the CTV and normal organs in gastric cancer with the use of the active breath co-ordinate technique. Second, we analysed the region where variations most likely occur. Third, we investigated the influence of interobserver variation on the dose distribution.

Intensity modulated radiation therapy with simultaneous integrated boost based dose escalation on neoadjuvant chemoradiation therapy for locally advanced distal esophageal adenocarcinoma.

To evaluate impact of radiation therapy dose escalation through intensity modulated radiation therapy with simultaneous integrated boost (IMRT-SIB). We retrospectively reviewed the patients who underwent four-dimensional-based IMRT-SIB-based neoadjuvant chemoradiation protocol. During the concurrent chemoradiation therapy, radiation therapy was through IMRT-SIB delivered in 28 consecutive daily fractions with total radiation doses of 56 Gy to tumor and 5040 Gy dose-painted to clinical tumor volume, with a regimen at the discretion of the treating medical oncologist. This was followed by surgical tumor resection. We analyzed pathological completion response (pCR) rates its relationship with overall survival and event-free survival. Seventeen patients underwent dose escalation with the IMRT-SIB protocol between 2007 and 2014 and their records were available for analysis. Among the IMRT-SIB-treated patients, the toxicity appeared mild, the most common side effects were grade 1-3 esophagitis (46%) and pneumonitis (11.7%). There were no cardiac events. The Ro resection rate was 94% (n = 16), the pCR rate was 47% (n = 8), and the postoperative morbidity was zero. There was one mediastinal failure found, one patient had local failure at the anastomosis site, and the majority of failures were distant in the lung or bone. The 3-year disease-free survival and overall survival rates were 41% (n = 7) and 53% (n = 9), respectively. The dose escalation through IMRT-SIB in the chemoradiation regimen seems responsible for down-staging the distal esophageal with well-tolerated complications.

Supraclavicular Nodal Involvement in Breast Cancer: How and When Should We Adapt the RTOG Atlas Guidelines?

The role of regional nodal irradiation (RNI) in breast cancer is evolving. In the current era of 3D treatment planning, it is important to accurately identify target volumes. The Radiation Therapy Oncology Group (RTOG) has outlined guidelines to define target nodal volumes for early stage breast cancer. The aim of this study was to identify whether breast cancer nodal involvement in the supraclavicular region correlated with the clinical tumor volume (CTV) as defined by the RTOG atlas. Thirty-one women with invasive breast carcinoma with supraclavicular nodal involvement were identified for analysis. For each patient, an individual CTV for the supraclavicular nodal region was contoured using the RTOG Breast Cancer Contouring Atlas as a guide. Involved nodes (gross tumor volume, GTV) were contoured independently using information from diagnostic imaging (including computed tomography (CT), positron emission tomography (PET)/CT, or magnetic resonance imaging (MRI). The supraclavicular CTV was compared to the GTVs for pathologic nodes, and each node was assigned a value for complete coverage, partial coverage, or complete discordance. In cases of partial coverage, the degree of coverage was expressed a percentage of the volume of the node which fell within the supraclavicular CTV. Forty-nine supraclavicular lymph nodes were available for comparison to the supraclavicular CTV. 36.7% of the nodes were completely concordant, while 10.2% were completely discordant. For the remaining 53.1% of supraclavicular nodes which were partially covered, the degree of coverage ranged from 4.2% to 96.7%. In the cases where there was discordance, the nodes were located posteriorly and/or laterally to the supraclavicular CTV. Patients with supraclavicular nodal involvement were more likely to have adverse pathologic features, with 13 of 31 (42%) having estrogen/progesterone/Her2-neu negative cancer (triple negative) and 14 of 31 (45%) having estrogen receptor positive tumors with high Ki-67 or Her2-neu positivity (consistent with a luminal B-like tumor). Understanding patterns of supraclavicular nodal failure in breast cancer could help guide prophylactic nodal irradiation, and this study suggests that current RTOG atlas guidelines for the supraclavicular fossa may not extend posteriorly and laterally enough. However, given that broadening coverage may result in increased toxicity, identifying subsets of women at higher risk for failure is of particular importance.

Validation of the Radiation Dose Volume Response Model for Locally Advanced Rectal Cancer After Preoperative Chemoradiation and the New Implication for Disease Prognosis

Tumor regression after the preoperative chemoradiation therapy (CRT) is prognostic significance for locally advanced rectal cancer. Our goal is to validate the prior reported radiation dose-volume-response model for locally advanced rectal cancer after preoperative chemoradiation and find its new prognostic implication. The study began with a cohort of 50 patients who had locally advanced low rectal cancer and received long-course neoadjuvant 5-FU based chemoradiation therapy followed by surgery of total mesorectal excision. The parameters of the radiation dose-volume-response model included accumulated radiation dose to primary tumor, clinical nodal (cN) status and primary tumor volume. We evaluated the goodness of fit of the model with the pathological tumor regression grading (TRG 1-5) and compared its accuracy with prior reported TRG prediction parameters as age, gender, clinical tumor (cT) stage and cN stage. The median follow-up time of this cohort was 36.5 months. The pathological complete response (pCR), T downstaging, and N downstaging rate were 18%, 64%, and 48%, respectively. The model-predicted probability of at least grade TRG 1 response (TRP_TRG1) ranged from 3.2% to 28.8% (median: 16.6%). The mean TRP_TRG1 of patients with pathological TRG1, TRG2, and TRG3/4 were 22%, 18.9% and 15.7%, respectively (p=0.033). Furthermore, if we assumed the TRP_TRG1 of 22% as the cut-off value, the pCR rate of subgroups with TRP_TRG1 > 22% and TRP_TRG1 < 22% were 41.7% and 10.5%, respectively (p=0.027). The TRP_TRG1 was the only significant factor among these clinical parameters including age, cT, cN, and radiation dose to predict pCR in this cohort. After univariate analysis, we identified that the subgroup with TRP_TRG1 > 16.6% and pathological TRG2/3/4 (SG1) had poor disease-free survival (DFS) than the rest patients in this cohort (39.8% vs. 65.7%; p=0.001). Multivariate analysis also revealed SG1 and cN stage both had independent significant impact on DFS. The mathematic model incorporating cN stage, radiation dose, and primary tumor volume provides a feasible and accurate way to predict the rectal tumor response after CRT. The subgroup which did not achieve the model-predicted tumor regression had poor prognosis, and the identification of this subgroup might help the selection of patients required for further adjuvant treatment.

Diffusion-weighted magnetic resonance imaging during radiotherapy of locally advanced cervical cancer – treatment response assessment using different segmentation methods

ABSTRACTBackground. Diffusion-weighted magnetic resonance imaging (DW-MRI) and the derived apparent diffusion coefficient (ADC) value has potential for monitoring tumor response to radiotherapy (RT). Method used for segmentation of volumes with reduced diffusion will influence both volume size and observed distribution of ADC values. This study evaluates: 1) different segmentation methods; and 2) how they affect assessment of tumor ADC value during RT.Material and methods. Eleven patients with locally advanced cervical cancer underwent MRI three times during their RT: prior to start of RT (PRERT), two weeks into external beam RT (WK2RT) and one week prior to brachytherapy (PREBT). Volumes on DW-MRI were segmented using three semi-automatic segmentation methods: “cluster analysis”, “relative signal intensity (SD4)” and “region growing”. Segmented volumes were compared to the gross tumor volume (GTV) identified on T2-weighted MR images using the Jaccard similarity index (JSI). ADC values from segmented volumes were compared and changes of ADC values during therapy were evaluated.Results. Significant difference between the four volumes (GTV, DWIcluster, DWISD4 and DWIregion) was found (p < 0.01), and the volumes changed significantly during treatment (p < 0.01). There was a significant difference in JSI among segmentation methods at time of PRERT (p < 0.016) with region growing having the lowest JSIGTV (mean± sd: 0.35 ± 0.1), followed by the SD4 method (mean± sd: 0.50 ± 0.1) and clustering (mean± sd: 0.52 ± 0.3). There was no significant difference in mean ADC value compared at same treatment time. Mean tumor ADC value increased significantly (p < 0.01) for all methods across treatment time.Conclusion. Among the three semi-automatic segmentations of hyper-intense intensities on DW-MR images implemented, cluster analysis and relative signal thresholding had the greatest similarity to the clinical tumor volume. Evaluation of mean ADC value did not depend on segmentation method.

Single-isocenter hybrid IMRT plans versus two-isocenter conventional plans and impact of intrafraction motion for the treatment of breast cancer with supraclavicular lymph nodes involvement.

The purpose of this study was to compare the single‐isocenter, four‐field hybrid IMRT with the two‐isocenter techniques to treat the whole breast and supraclavicular fields and to investigate the intrafraction motions in both techniques in the superior direction. Fifteen breast cancer patients who underwent lumpectomy and adjuvant radiation to the whole breast and supraclavicular (SCV) fossa at our institution were selected for this study. Two planning techniques were compared for the treatment of the breast and SCV lymph nodes. The patients were divided into three subgroups according to the whole breast volume. For the two‐isocenter technique, conventional wedged or field‐within‐a‐field tangents (FIF) were used to match with the same anterior field for the SCV region. For the single‐isocenter technique, four‐field hybrid IMRT was used for the tangent fields matched with a half blocked anterior field for the SCV region. To simulate the intrafraction uncertainties in the longitudinal direction for both techniques, the treatment isocenters were shifted by 1 mm and 2 mm in the superior direction. The average breast clinical tumor volume (CTV) receiving 100% (V100%) of the prescription dose (50 Gy) was 99.3%±0.5% and 96.4%±1.2% for the for two‐isocenter and single‐isocenter plans (p<0.05), respectively. The breast CTV receiving 95% of the prescription dose (V95%) was close to 100% in both techniques. The average breast CTV receiving 105% (V105%) of the prescription dose was 32.4%±19.3% and 23.8%±13.3% (p=0.08). The percentage volume of the breast CTV receiving 110% of the dose was 0.4%±1.2% in the two‐isocentric technique vs. 0.1%±0.2% in the single‐isocentric technique. The average uniformity index was 0.91±0.02 vs. 0.91±0.01 in both techniques (p=0.04), but had no clinical impact. The percentage volume of the contralateral breast receiving a dose of 1 Gy was less than 2.3% in small breast patients and insignificant for medium and large breast sizes. The percentage of the total lung volume receiving g>20 Gy (V20Gy) and the heart receiving >30 Gy (V30Gy) were 13.6% vs. 14.3% (p=0.03) and 1.25% vs. 1.2% (p=0.62), respectively. Shifting the treatment isocenter by 1 mm and 2 mm superiorly showed that the average maximum dose to 1 cc of the breast volume was 55.5±1.8 Gy and 58.6±4.3 Gy in the two‐isocentric technique vs. 56.4±2.1 Gy and 59.1±5.1 Gy in the single‐isocentric technique (p=0.46, 0.87), respectively. The single‐isocenter technique using four‐field hybrid IMRT approach resulted in comparable plan quality as the two‐isocentric technique. The single‐isocenter technique is more sensitive to intrafraction motion in the superior direction compared to the two‐isocentric technique. The advantages of the single‐isocenter include elimination of isocentric errors due to couch and collimator rotations and reduction in treatment time. This study supports consideration of a single‐isocenter four‐field hybrid IMRT technique for patients undergoing breast and supraclavicular nodal irradiation.PACS number: 87.55.D, 87.55.de, 87.55.dk,

SU‐E‐T‐79: A Study of the Effect of Clinical Tumor Volume Displacement On the Dosage of Post Modified Radical Mastectomy Intensity‐Modulated Radiation Therapy Plans for Left‐Sided Breast Cancer

Purpose:To explore the effect of clinical tumor volume (CTV) displacement on the dosage of intensity‐modulated radiation therapy (IMRT) plans for left‐sided breast cancer after modified radical mastectomy.Methods:We created 2 sets of IMRT plans based on PTV0.5 and PTV0.7 (with CTV displacement of 0.5cm and 0.7cm respectively) for each of the ten consecutive left‐sided breast cancer patients after modified radical mastectomy, and compared the difference in PTV coverage and organ at risk (OAR) sparing between the two groups. And then, we compared the difference in PTV coverage in IMRT plans based on PTV0.5 between the group with properly estimated CTV displacement (presuming the actual CTV displacement was 0.5cm) and the one with underestimated CTV displacement (presuming the actual CTV displacement was 0.7cm). The difference in results between the corresponding two groups was compared using paired‐sample t‐test. P values less than 0.05 were considered statistically significant.Results:IMRT plans derived from PTV0.5 had more homogenous PTV coverage, and less heart, left lung, right breast, right lung, left humeral head and B‐P radiation exposure, as well as less total Mu as compared with the ones stemmed from PTV0.7 (all p&lt;0.05). IMRT plans with appropriate estimation of CTV displacement had better PTV coverage compared with the ones with underestimated CTV displacement (all p&lt;0.01).Conclusion:The IMRT plans with smaller CTV displacement in post modified radical mastectomy radiotherapy for left‐sided breast cancer has dosimetrical advantages over the ones with larger CTV displacement. Underestimation of CTV displacement can lead to significant reduction of PTV coverage. Individually quantifying and minimizing CTV displacement can significantly improve PTV coverage and OAR (including heart and left lung) sparing.This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)

Validity of high intensive focused ultrasound in the treatment of uterus myoma and adenomyoma in Hebei Province: a report of 166 cases

To explore the validity of high intensive focused ultrasound (HIFU) in the treatment of uterus myoma and adenomyoma. A total of 166 patients with uterus myoma and adenomyoma received HIFU treatment from July 2011 to November 2013 at our hospital. The follow-ups were conducted at 1, 3, 6 month post-treatment. Their status of clinical symptoms, tumor volume, blood flow and efficacy of HIFU were evaluated. Menstrual blood decreased after treatment. The levels of hemoglobin all returned to normal in anemic patients and dysmenorrhea showed great improvement. Ultrasound showed that uterine ablation lesions significantly diminished after treatment. The effective rate was 71.8% at 1 month, 86.1% at 3 month and 95.4% at 6 month post-treatment and blood flow within ablation lesions decreased after treatment. None of unacceptable side effects occurred. HIFU treatment of uterus myoma and adenomyoma is both feasible and safe with fewer side effects.

Novel high dose rate lip brachytherapy technique to improve dose homogeneity and reduce toxicity by customized mold.

Purpose/ObjectivesThe purpose of this study is to describe a novel brachytherapy technique for lip Squamous Cell Carcinoma, utilizing a customized mold with embedded brachytherapy sleeves, which separates the lip from the mandible, and improves dose homogeneity.Materials and methodsSeven patients with T2 lip cancer treated with a “sandwich” technique of High Dose Rate (HDR) brachytherapy to the lip, consisting of interstitial catheters and a customized mold with embedded catheters, were reviewed for dosimetry and outcome using 3D planning. Dosimetric comparison was made between the “sandwich” technique to “classic” – interstitial catheters only plan. We compared dose volume histograms for Clinical Tumor Volume (CTV), normal tissue “hot spots” and mandible dose. We are reporting according to the ICRU 58 and calculated the Conformal Index (COIN) to show the advantage of our technique.ResultsThe seven patients (ages 36–81 years, male) had median follow-up of 47 months. Four patients received Brachytherapy and External Beam Radiation Therapy, 3 patients received brachytherapy alone. All achieved local control, with excellent esthetic and functional results. All patients are disease free.The Customized Mold Sandwich technique (CMS) reduced the high dose region receiving 150% (V150) by an average of 20% (range 1–47%), The low dose region (les then 90% of the prescribed dose) improved by 73% in average by using the CMS technique. The COIN value for the CMS was in average 0.92 as opposed to 0.88 for the interstitial catheter only. All differences (excluding the low dose region) were statistically significant.ConclusionThe CMS technique significantly reduces the high dose volume and increases treatment homogeneity. This may reduce the potential toxicity to the lip and adjacent mandible, and results in excellent tumor control, cosmetic and functionality.

RT-13 * OPTIMIZING RADIATION THERAPY FOR GLIOBLASTOMA PATIENTS: A COMPARATIVE STUDY OF USING DIFFERENT MRI MODALITIES TO MINIMIZE RADIATION INJURY

Glioblastoma multiforme is the most common and lethal primary malignant brain tumor and radiation therapy is considered the standard of care in the adjuvant setting. Current radiation treatment planning guidelines recommend FLAIR MRI sequence with a 2 cm margin to encompass the subclinical tumor spread. However, the FLAIR modality extensively visualizes the surrounding edema, possibly leading to unnecessary radiation toxicity to healthy brain tissue. We hypothesize that we can optimize radiation therapy by using alternative MRI modalities or by decreasing clinical tumor volume margins to minimize toxicity without compromising accurate tumor targeting. We retrospectively collected data for 21 patients with pathology confirmed recurrence and created radiation treatment plans using ADC, ADC without FLAIR shine-through (ADCst), DWI, T1, and FLAIR. For the FLAIR both a 1 cm and 2 cm margin was used (FLAIR1 and FLAIR2). Boolean operators were used to calculate the accuracy of targeting tumor recurrence and excessive radiation volume compared to the standard FLAIR2 treatment plan. All MRI modalities had complete coverage of the recurrent tumor and the mean differences in accuracy between the different MRI modalities and FLAIR2 was not significant. However, there was a significant reduction in the excessive radiation volume compared to FLAIR2. ADCst had a 51.3% reduction, DWI 42.3%, T1 42.6%, and FLAIR1 44.6% reduction of excessive radiation volume compared to FLAIR2 (p < 0.05). ADC did not have a significant reduction of excessive radiation volume compared to FLAIR2. Our data support the hypothesis that using MRI modalities other than the standard FLAIR or decreasing the margin by 1cm may optimize radiation therapy for GBM patients by reducing unnecessary radiation dose to healthy brain tissue without compromising accuracy. By using new MRI modalities in radiation treatment planning or modifying clinical tumor volume margins we can decrease radiation toxicity to patients to improve their quality of life.