Mean V20 Research Articles

“Field in field” for the treatment of breast cancer with lymph nodes: A comparative study with conventional radiotherapy using wedge filters

Introduction Treatment of breast cancer with lymph nodes (internal mammary and clavicular nodes) is achieved in most of the centers using a conventional radiotherapy based on electron-photon beams with junctions and wedge filters. Wedge filters correct for surface obliquities but do not provide optimal dose homogeneity within the breast volume. This study aims at comparing treatment plans using the ‘‘field in field” technique, equivalent to a ‘‘simplified” intensity modulation with treatment plans using wedge filters. Material and methods This study focused on eight patients (for half of the patients, the internal mammary nodes were included in the breast fields) treated for breast cancer with lymph nodes using wedge filters. For these patients a ‘‘field in field” plan was prepared retrospectively. Patients were positioned supine with ipsilateral arm above the head and head turned to the opposite treatment side. The prescribed dose was 50 Gy to the PTV breast and 46–50 Gy for the lymph nodes. For both technics, after treatment plan optimization, doses delivered to targets, heart and ipsilateral lung are reported. Results For the 8 patients and for the same coverage of breast and lymph nodes PTV, the volume of 105% (52.5 Gy) of the dose remaining in the breast volume was 2.65–24.29 cc (mean 13.9 cc) with the ‘‘field in field” technic and 9.49–231.63 cc (mean 98.5 cc) with wedge filters technic. For ipsilateral lung, the mean dose, V20 and V30 were respectively 15.1–16.6 Gy (average 15.8 Gy), 25.4–27.1 Gy (average 26.1 Gy), and 17.3–19 Gy (mean 17.9 Gy) for both technics. Conclusion For 8 patients, ‘‘field in field” treatment plans showed that remaining volume of 105% of the dose was up to 10 times smaller than using wedge filters treatment plans. This technics allowed reducing significantly overdosage areas and therefore having a better dose homogeneity in the breast.

Rapidarc vs. tomotherapy for the treatment of chestwall and lymph nodes: A comparative study

Introduction Treatment of chestwall with lymph nodes (internal mammary and clavicular nodes) is achieved in most of the centers with conventional radiotherapy using photons and electrons beams with junctions. The aim of this study is to do a dosimetric comparative study between two technics using modulation irradiation: Tomotherapy and Rapid Arc (RA). Material and methods Seven patients (5 left, 2 right) were treated using Tomotherapy. For these patients a RA plan was prepared retrospectively. Patients were positioned supine with two arms above the head. The prescribed dose was 50 Gy for the chestwall and 46–50 Gy for the lymph nodes. Optimisation constraints were increased until the PTV coverage was acceptable. Tomotherapy plans were computed with a 2.5–5 cm collimation and a 0.287 pitch. RA plans were computed using a 5 mmbolus on the chestwall, 2 arcs (60–180°) and a +/-10° collimator rotation. Doses delivered to targets, heart and both lungs are reported. Results For the 7 patients the heart mean dose was 7.1–8.6 Gy (mean 7.5 Gy) with Tomotherapy and 4.4–18.1 Gy (mean 9.9 Gy) for RA. For the ipsilateral lung, the mean dose, V5, V20 and V30 were respectively 10.1–14.7 Gy, 56.4–85.7%, 14.8–25.9% and 6.2–16.6% for Tomotherapy. For RA, these values were 10.5–16.0 Gy, 65.3–96.0%, 14.8–30.0% and 6.2–16.6%. Conclusion For 5/7 patients RA plans were acceptable but the OAR doses were generally higher than Tomotherapy plans (in particular V5 of lungs and lung mean dose). For 2/7 patients (left side) RA plans were not acceptable.

TH-A-116-10: A Dosimetric Comparison Between Volumetric Modulated Arc and 3D Treatment Plans for Synchronous Bilateral Breast Patients Treated with Simultaneous Integrated Boost

Purpose: To evaluate dosimetric differences between standard tangential and volumetric modulated arc (VMAT) plans for synchronous bilateral breast patients treated with simultaneous integrated boost (SIB). Methods: For 10 bilateral breast patients we created separate left and right tangential plans and a single VMAT plan encompassing both breasts and tumor beds as target volumes. Patients were prescribed to 50 and 60 Gy in 2 and 2.4 Gy daily fractions to breasts and tumor beds respectively. For 3D plans each breast was planned independently. A sum of the independent plans was generated to ensure no dose overlaps, and for comparison with the VMAT plan. VMAT plans were normalized to 95% dose covering 95% breast volume. Optimization objectives for lungs, heart, and spine were based on QUANTEC data. Conformity index (CI) was calculated for all plans. Data were analyzed using the Mann‐Whitney Rank‐Sum test. Results: Tumor bed and breast coverage was similar for 3D and VMAT plans. However, CI for VMAT was significantly better (p<0.001) for both breast and tumor bed. All organ at risk (OAR) metrics (Mean Lung Dose, V20, V5, maximal heart and spine doses) were significantly better (p<0.001) in the 3D plans. Conclusion: Conformity in VMAT plans was superior to 3D plans, indicating that in 3D plans larger volumes of non‐target tissue received high doses. In addition, VMAT treatment setup is much simpler than for 3D plans, where treatment is delivered sequentially to each breast, necessitating separate setups for each side. Thus, VMAT treatment is faster, and much easier for patients. However, 3D plans are overwhelmingly superior to VMAT in terms of doses to OARs. Thus, possibly because the breast is a peripheral organ, it appears to be a unique site, where OARs are better spared by a ‘simple’ tangential plan rather than a more sophisticated VMAT technique.

TU‐G‐108‐06: Anatomical Localization of Late Rectal Toxicity Predictors in Prostate Radiotherapy

Purpose: To determine dosimetric predictors of late rectal toxicity after prostate radiotherapy, differentiating between dose to rectum and anal canal. Methods: Clinical and 3D dosimetric data for 738 patients were prospectively collected in a clinical trial (TROG 03.04 “RADAR”) of variable‐duration hormone therapy with conformal radiotherapy using rectal DVH constraints of V65&lt;40%, V70&lt;30%, V75&lt;5%. Dose‐volume histograms were generated for whole anorectum, anal canal, rectum and matched to longitudinal toxicity (measured 6‐monthly). Outcome measures were: bleeding, urgency/tenesmus (grade 1+, 2+, 3), pooled Common Toxicity Criteria version 2 proctitis (grade 1+, 2+), incontinence, bowel bother, diarrhea, and anorectal pain. Both prevalence (at 30 months post radiotherapy) and actuarial incidence (time‐to‐failure) endpoints were analyzed. Rectal mean dose and V5–V70 were used as factors in multivariate and univariate logistic regression (prevalence) and Cox proportional hazards (incidence) analyses. Results: Median follow‐up was 6.5 years post‐treatment. Multivariate models produced erratic effect estimates due to multicollinearity arising from constrained DVH shape as mandated by the trial protocol. Univariate analysis identified that pain, pooled proctitis, incontinence were predicted most by anal canal dose. Bleeding and diarrhea were not subvolume dependent. Bowel bother was not associated with any factor. Urgency/tenesmus association with subvolume depended on the outcome grade used. Conclusion: Doses to different subvolumes of the rectum are responsible for different types of toxicity. Different grades of the same toxicity are predicted by different subvolumes and DVH points. For datasets planned with dose constraints, multicollinearity of DVH points limits the usefulness of multivariate analysis. Further work will estimate DVH constraints to limit toxicity, and Lyman model parameters from the same data. Funding: National Health and Medical Research Council (Australian Government), Hunter Prostate Cancer Alliance, Trans‐Tasman Radiation Oncology Group. Conflicts of interest: none declared

SU-E-P-09: Feasibility of Axillary Target Coverage Utilizing High Tangent Prone Breast Radiation

Purpose: To evaluate the ability to treat level I and level II axillary lymph nodes utilizing a high tangent prone breast radiotherapy technique. Methods: Twenty-one patients were treated with whole breast radiation utilizing a prone technique. Retrospectively, axillary nodes were contoured as levels I and low lying level II with the intent of elective nodal coverage. Treatment plans were designed as tangential fields with the superior border set to cover the contoured axillary volume (high tangents). Dose-volume histograms (DVH) were evaluated for axillary, breast, lung and heart (for left breast treatments) coverage. The percent volume receiving greater than or equal to 95% of the prescribed dose (V95) was obtained for the breast and axillary regions. Results: The 95% isodose line encompassed on average 98.0% of breast volumes (range, 93.2 to 100.0%). The mean V95 for the level I and level II axillary regions were 99.5% (range, 98.3 to 100.0%) and 97.4% (range, 92.5 to 100.0%), respectively. The mean percent volume of the ipsilateral lung receiving greater than 20 Gy was 7.7% (range, 4.0 to 13.4%), and the percent volume of the heart receiving greater than 40 Gy was 0.57% (range, 0 to 2.1%). Conclusion: These results imply that prone breast radiation with high tangents is an effective and safe technique for the treatment of level I and level II axilla in addition to breast volumes. With increasing trends to limit axillary dissections in sentinel node positive patients, radiotherapy techniques to adequately cover nodal volumes has become more important. With historic data that suggested lower coverage in a prone position, we present techniques to adequately cover elective nodal volumes with good success.

Inverse planning for combination of intracavitary and interstitial brachytherapy for locally advanced cervical cancer

The main purpose of this study was to compare three different treatment plans for locally advanced cervical cancer: (i) the inverse-planning simulated annealing (IPSA) plan for combination brachytherapy (BT) of interstitial and intracavitary brachytherapy, (ii) manual optimization based on the Manchester system for combination-BT, and (iii) the conventional Manchester system using only tandem and ovoids. This was a retrospective study of 25 consecutive implants. The high-risk clinical target volume (HR-CTV) and organs at risk were defined according to the GEC-ESTRO Working Group definitions. A dose of 6 Gy was prescribed. The uniform cost function for dose constraints was applied to all IPSA-generated plans. The coverage of the HR-CTV by IPSA for combination-BT was equivalent to that of manual optimization, and was better than that of the Manchester system using only tandem and ovoids. The mean V100 achieved by IPSA for combination-BT, manual optimization and Manchester was 96 ± 3.7%, 95 ± 5.5% and 80 ± 13.4%, respectively. The mean D100 was 483 ± 80, 487 ± 97 and 335 ± 119 cGy, respectively. The mean D90 was 677 ± 61, 681 ± 88 and 513 ± 150 cGy, respectively. IPSA resulted in significant reductions of the doses to the rectum (IPSA D2cm3: 408 ± 71 cGy vs manual optimization D2cm3: 485 ± 105 cGy; P = 0.03) and the bladder (IPSA D2cm3: 452 ± 60 cGy vs manual optimization D2cm3: 583 ± 113 cGy; P < 0.0001). In conclusion, combination-BT achieved better tumor coverage, and plans using IPSA provided significant sparing of normal tissues without compromising CTV coverage.

Analyse des résultats d’une série de 20 patients traités par irradiation hypofractionnée en conditions stéréotaxiques par Novalis Tx® pour un cancer bronchopulmonaire non à petites cellules de stade I

PurposeRecent clinical results of dose escalation with stereotactic body radiation therapy to increase local tumour control for patients with stage I non–small-cell lung cancer who either refuse surgery or are medically inoperable resulted in making it a standard treatment in this setting. This treatment technique was implemented at the Paul-Strauss Centre, Strasbourg, in 2010. The objective of this study is to describe and analyze the data of the first 20 treated patients. Patients and methodsFrom October 2010 to May 2012, 20 patients were treated with this technique for T1N0M0 or T2N0M0 lung tumour. The indication was proposed by the multidisciplinary thoracic oncology team meeting, and approved by the technical committee of the Department of Radiotherapy. After the realization of a dosimetric CT Scan (4DCT or three phases – free breathing and deep breath-hold inspiration and expiration) and after performing a (18F)-FDG PET scan in the treatment position, all patients were treated on Novalis Tx® linear accelerator, with arctherapy or modulated intensity radiotherapy (IMRT). A protocol has been defined for the prescribed dose, depending on the size and location of the tumor, central or peripheral. The patients underwent follow-up during treatment and at 1 month, 3–4 months, 6 and 9 months to assess outcomes and toxicities. ResultsThe mean age was 72.6 years (52–89). Seventeen patients had one or more pulmonary comorbidities. The mean delivered dose was 59.9Gy (40–70) in 4Gy to 17.5Gy fractions. The mean gross tumour volume was 14.9mL (median 7.2, 0.9 to 73.5) and the mean planning target volume was 77.8mL (median 49.5; 17–300). The mean initial SUV max was 7.7 (1.8 to 16.7). Dose constraints and planning target volume coverage recommended by the protocol were achieved in the majority of cases. The mean lung V20 was 7.63% (1.2 to 17.7) and the mean dose delivered to the planning target volume was 94.6% (88–99). The duration of treatment was 21 days (median: 23; 8–27), and no change or interruption of prescribed treatment has occurred. Median follow-up was 6.6 months, and crude rates of objective response for patients evaluated were 85% (11/13 patients) at 3 months and 100% at 6 and 9 months. The complete response rate at 3 and 6 months were 0 (0/13 patients) and 50% (5/10 patients). Two patients had metastatic disease in the 6 months following treatment. Concerning pulmonary toxicity at 3 months, 6 patients developed G2 radiation pneumonitis and three patients G3, with positive evolution. ConclusionThe analysis of the results of this series, comparable with those described in literature, shows that lung stereotactic radiotherapy is an effective and well-tolerated treatment for inoperable patients. The extension of the indications could be envisaged based on the results of ongoing trials.

Japanese nationwide multi-institutional cohort study of prostate cancer brachytherapy with permanent seed implantation.

e16090 Background: Brachytherapy with permanent iodine-125 seed implantation (PI) has been approved in 2003 in Japan. Multi-institutional cohort study (Japanese Prostate Cancer Outcome Study of Permanent Seed Implantation; J-POPS, NCT00534196) assessing the treatment feature, efficacy, safety and health-related quality of life (QOL) has started in July 2005. Six thousand nine hundred and twenty-seven cases were enrolled to this study until December 2010 from 68 institutes around the country, which is approximately 40% of all the cases treated in Japan at that time. Methods: Patient’s background, cancer character, treatment feature such as combined therapy of external beam or hormone, post PI dosimetric information, treatment efficacy with PSA level, voiding symptoms with IPSS and treatment related adverse events according to NCI-CTCAE are investigated. PSA was measured every 3 months and symptoms accompanied to the treatment were assessed 3 to 6 months after the treatment. Backgrounds and treatment assessments of 2,341 patients enrolled in J-POPS during the initial 2 years are evaluated. Results: Patients’ age ranged from 45 to 89 (median 69) year-old and 99.0% of the cases were performance status 0 (ECOG criteria). Family history of prostate cancer was seen in 6.2%. PSA levels on cancer diagnosis were 1.60 to 42.0 (mean 6.80) ng/ml, clinical stage T2a or less was 89.9%, T2b was 5.2%, T2c was 2.9% and T3a-T3b was 0.8%. Gleason score (GS) less than 7 was 56.6%, GS 7 was 39.7%, and GS above 7 was 3.6%. According to NCCN risk classification, 44.2% was classified as low risk, 48.3% as intermediate risk and 5.7% as high risk. Androgen deprivation therapy (ADT) was performed in 48.5% of the patients and 23.4% was combined with external beam radiation therapy (EBRT). CT scan based first post therapeutic month dosimetry revealed that prostatic mean V100 and D90 for the cases treated with seed alone were 94.8% and 160.7 Gy, respectively. As for adequate control of radiation dose at rectum (mean R100 = 0.3 cc) and urethra (mean D5 = 223.4 Gy), high grade toxicities appeared very seldom. Conclusions: Outcomes of J-POPS will produce clinical evidence of PI that can be internationally accepted.

Volumetric‐modulated arc therapy for the treatment of a large planning target volume in thoracic esophageal cancer

Recently, volumetric‐modulated arc therapy (VMAT) has demonstrated the ability to deliver radiation dose precisely and accurately with a shorter delivery time compared to conventional intensity‐modulated fixed‐field treatment (IMRT). We applied the hypothesis of VMAT technique for the treatment of thoracic esophageal carcinoma to determine superior or equivalent conformal dose coverage for a large thoracic esophageal planning target volume (PTV) with superior or equivalent sparing of organs‐at‐risk (OARs) doses, and reduce delivery time and monitor units (MUs), in comparison with conventional fixed‐field IMRT plans. We also analyzed and compared some other important metrics of treatment planning and treatment delivery for both IMRT and VMAT techniques. These metrics include: 1) the integral dose and the volume receiving intermediate dose levels between IMRT and VMATI plans; 2) the use of 4D CT to determine the internal motion margin; and 3) evaluating the dosimetry of every plan through patient‐specific QA. These factors may impact the overall treatment plan quality and outcomes from the individual planning technique used. In this study, we also examined the significance of using two arcs vs. a single‐arc VMAT technique for PTV coverage, OARs doses, monitor units and delivery time. Thirteen patients, stage T2‐T3 N0‐N1 (TNM AJCC 7th edn.), PTV volume median 395 cc (range 281–601 cc), median age 69 years (range 53 to 85), were treated from July 2010 to June 2011 with a four‐field (n=4) or five‐field (n=9) step‐and‐shoot IMRT technique using a 6 MV beam to a prescribed dose of 50 Gy in 20 to 25 F. These patients were retrospectively replanned using single arc (VMATI, 91 control points) and two arcs (VMATII, 182 control points). All treatment plans of the 13 study cases were evaluated using various dose‐volume metrics. These included PTV D99, PTV D95, PTV V9547.5Gy(95%), PTV mean dose, Dmax, PTV dose conformity (Van't Riet conformation number (CN)), mean lung dose, lung V20 and V5, liver V30, and Dmax to the spinal canal prv3mm. Also examined were the total plan monitor units (MUs) and the beam delivery time. Equivalent target coverage was observed with both VMAT single and two‐arc plans. The comparison of VMATI with fixed‐field IMRT demonstrated equivalent target coverage; statistically no significant difference were found in PTV D99 (p=0.47), PTV mean (p=0.12), PTV D95 and PTV V9547.5Gy (95%) (p=0.38). However, Dmax in VMATI plans was significantly lower compared to IMRT (p=0.02). The Van't Riet dose conformation number (CN) was also statistically in favor of VMATI plans (p=0.04). VMATI achieved lower lung V20 (p=0.05), whereas lung V5 (p=0.35) and mean lung dose (p=0.62) were not significantly different. The other OARs, including spinal canal, liver, heart, and kidneys showed no statistically significant differences between the two techniques. Treatment time delivery for VMATI plans was reduced by up to 55% (p=5.8E−10) and MUs reduced by up to 16% (p=0.001). Integral dose was not statistically different between the two planning techniques (p=0.99). There were no statistically significant differences found in dose distribution of the two VMAT techniques (VMATI vs. VMATII) Dose statistics for both VMAT techniques were: PTV D99 (p=0.76), PTV D95 (p=0.95), mean PTV dose (p=0.78), conformation number (CN) (p=0.26), and MUs (p=0.1). However, the treatment delivery time for VMATII increased significantly by two‐fold (p=3.0E−11) compared to VMATI. VMAT‐based treatment planning is safe and deliverable for patients with thoracic esophageal cancer with similar planning goals, when compared to standard IMRT. The key benefit for VMATI was the reduction in treatment delivery time and MUs, and improvement in dose conformality. In our study, we found no significant difference in VMATII over single‐arc VMATI for PTV coverage or OARs doses. However, we observed significant increase in delivery time for VMATII compared to VMATI.PACS number: 87.53.Kn, 87.55.‐x

Radical prostatectomy versus high dose permanent prostate brachytherapy using iodine-125 seeds for patients with high risk prostate cancer: a matched cohort analysis

To compare the biochemical outcomes reported after radical prostatectomy (RP) versus high dose permanent prostate brachytherapy (HDPPB) using iodine-125 seeds in the treatment of matched high risk prostate cancer (HiPCa). In this retrospective review, 55 HiPCa patients treated between March 2006 and August 2011, who underwent HDPPB using iodine-125 seeds combined with external beam radiation therapy (EBRT) or androgen deprivation therapy (ADT), were compared with 55 HiPCa patients who underwent RP. Patients were matched for age, prostate-specific antigen (PSA), clinical stage, and Gleason scores. The biochemical outcomes after HDPPB and RP were compared via Kaplan-Meier analysis. Of the 110 patients analyzed, the mean ages, PSA, and Gleason biopsy scores were similar between the two cohorts. Among patients who underwent HDPPB, 20 patients (36.4%) had received adjuvant EBRT. Of this subsample, most patients (98.2%) had received adjuvant ADT for 3 months. Among patients with RP, 20 patients (36.4%) had received adjuvant EBRT, whereas 28 patients had received adjuvant ADT. The mean implanted seed numbers were 92.8, the mean D90 was 218.7 Gy, and the mean V100 was 96.1% after HDPPB. With regard to oncological outcomes, biochemical disease-free survival rates were similar between the two cohorts (82.6 vs. 81.1%, p = 0.982). Urethrorectal fistula developed in one patient with HDPPB. RP and HDPPB, using iodine-125 seeds with combined treatment modalities, exhibited similar biochemical recurrence-free survival rates among HiPCa patients. Further prospective studies with greater sample sizes and longer follow-up periods are needed to validate these results.

Focal brachytherapy for selected low-risk prostate cancers: A pilot study

To evaluate the feasibility and the early toxicity of focal brachytherapy in highly selected localized prostate cancer patients. Twenty-one patients underwent a focal brachytherapy between February 2010 and March 2012, representing 3.7% of the cases treated by our group during this period. Patient selection was based on (at least) two series of prostate biopsies and a high-resolution MRI. Only patients with very limited and localized tumors, according to strict criteria, were selected for the procedure. The technique used a real-time procedure with the implantation of free (125)I seeds and dynamic dose calculation. The prescribed dose for the focal volume was 145Gy. The treated volume corresponded to a mean value of 34% of the total prostatic volume (range, 20-48%). For the focal volume, the mean D90 and V100 was 183.2Gy (range, 176-188Gy) and 99.3% (range, 98.8-100%), respectively. The technique was performed in an hour and a half. When compared with a previous cohort treated by whole-prostate brachytherapy, urinary toxicity (International Prostate Symptom Score) was borderline reduced (p= 0.04) at 6 months only, whereas the recovery of the International Index of Erectile Function 5 was better (p= 0.014). The International Continence Score was nil in almost all cases as well as rectal toxicity. Focal treatment by brachytherapy is easily feasible with little acute toxicity. Further investigation is needed to assess the results in terms of tumor control and long-term toxicity.

Impact of small prostate size on postimplant prostate dosimetry: Analysis of a large community database

Achieving high-quality permanent interstitial brachytherapy in smaller prostates is thought to be more difficult than in larger glands. This study evaluates 4547 implants in a large community database to test this hypothesis. From January 2003 to October 2010, 4547 prostate brachytherapy implants from a large community database were analyzed. The cohort was divided into three groups based on size, namely smaller (<30cm(3), n=1301), medium (30-40cm(3), n=1861), and large (>40cm(3), n=1385). Postimplant dosimetry, including D90, V100, and V100 by prostate sector, was performed for each implant. Comparison of mean V100 among small, medium, and larger prostate volume cohorts was performed using a one-way analysis of variance test. For the overall cohort, the D90 was 105% and 104% for monotherapy and boost, respectively. Mean D90 for small prostates was 106% and 104% for monotherapy and boost, respectively. Mean V100 for small prostates was 91.1% and 90.0%, respectively. Coverage for small prostates was as good or slightly better than larger glands. V100 by prostate sector revealed that there were no sectors for which smaller glands had significantly inferior coverage compared with larger glands. Although smaller prostates may in some respects be more technically difficult to implant than larger glands, a review of community-based brachytherapists reveals that with current implant techniques, good quality implants are readily achievable in men with smaller glands.

Predictive Factors for Child-Pugh Score Elevation in Hepatocellular Carcinoma Patients Treated with Conformal Radiation Therapy: Dose-Volume Histogram Analysis

We designed the study to identify the clinical and dose-volumetric parameters associated with the risk of Child-Pugh score elevation in hepatocellular carcinoma patients treated with conformal radiation therapy. All 161 hepatocellular carcinoma patients in the study underwent 4D-computed tomography simulation, and a dose-volume histogram was generated after radiotherapy planning. Patients who had an elevated Child-Pugh (e-CP) score of 2 or more without progressive disease within 3 months were defined as e-CP positive. Twenty-six of 142 patients without progressive disease were e-CP positive. Pretreatment Child-Pugh class, further treatment within 30 days of radiotherapy, lymph node metastasis, mean liver dose, V(20 Gy), V(25 Gy), and V(30 Gy) were significantly correlated with e-CP positivity. The e-CP developed in 13 of 106 patients (12.3%) with V(30 Gy) of ≤28.1% and in 13 of 36 patients (36.1%) with V(30 Gy) >28.1% (P = 0.001). Our data demonstrate that mean liver dose, V(10 Gy), V(20 Gy), V(25 Gy), and V(30 Gy) are independent dose-volumetric predictors for e-CP positivity in hepatocellular carcinoma patients treated with conformal radiation therapy. V(30 Gy) should be limited to less than 28.1% to minimize the risk of e-CP.

Template-Based Inverse PlanningSimulated Annealing for CT-Based High-Dose-Rate Brachytherapy of Cervical Cancer: Feasibility Study

Purpose:To investigate the feasibility of using an inverse planning technique for CT-based ring and tandem high-dose rate brachytherapy of cervical cancer. Methods and Materials:Two patients previously treated with high-dose-rate brachytherapy for cervical cancer were retrospectively identified for this study. Each patient had five intracavitary insertions using CT/MR-compatible tandem and ring applicators. The 6Gy isodose lines from the original clinical plans were converted into a structure set (S6) using MIMvista. Inverse plans were then generated in Oncentra using the inverse planning simulated annealing (IPSA) with S6 as the optimization target. The dose to 0.1cm3, 1cm3, 5cm3 of bladder (DB0.1, DB1, and DB5) and rectum (DR0.1, DR1, DR5) were determined from the dose volume histogram (DVH). Percentage of physician drawn clinical target volume (CTV) and S6 coverage (V100CTV, V100S6) were also recorded. Results:The mean V100%CTV of the original clinical plans and the inverse plans were 88.14% and 87.57%. The mean V100%S6 of the original clinical plans and the inverse plans was 98.68% and 97.00%. The mean dose reduction for DB0.1, DB1 and DB5 were 5.4%, 5.4%, and 4.7%, respectively. The mean dose reduction for DR0.1, DR1 and DR5 were 6.4%, 5.5%, and 4.8%. Conclusions:This work demonstrated the feasibility of this structure-based inverse planning. It can achieve comparable CTV coverage while reducing dose to critical structures. Once template structure set is constructed, this procedure can not only reduce planning time, but improve quality assurance by standardizing the procedure. This approach can be directly extended to other applicator-based brachytherapy procedures.

Comparison of Preplanning and Intraoperative Planning for I-125 Prostate Brachytherapy

To compare two widely used permanent prostate brachytherapy techniques, preplanning and intraoperative planning, based on postimplant dosimetry, toxicity and biochemical outcomes. Between 2003 and 2006, 665 men with localized prostate cancer were treated with permanent interstitial implantation. The first 227 consecutive men were treated with the preplanning technique, followed by 438 men treated with the intraoperative technique. Late toxicity was scored by the Common Terminology Criteria for Adverse Events v.4.0. Biochemical failure was defined as a prostate-specific antigen increase of more than 2 ng/ml above the nadir value excluding a benign bounce. Univariate and multivariate analyses were performed to identify the variables associated with biochemical failure-free survival. Postimplant target coverage was similar in the two groups, with a small difference in risk organ doses. Mean V100 was 96.3 vs. 96.7% (P = 0.205), D90 was 119.6 vs. 119.4% (P = 0.884), urethral D10 was 157.5 vs. 146.1% (P = 0.010), rectal V100 was 0.57 vs. 0.43 cc (P = 0.002) in the preplanning and intraoperative planning groups, respectively. Acute and late Grade 3 genitourinary and gastrointestinal toxicities were <1% for both methods. The 5-year biochemical failure-free survival rate was 95.4% for the preplanning and 94.0% for the intraoperative planning group (P = 0.776). Multivariate analysis revealed Gleason score, biopsy positive rate and V100 to be predictors of biochemical failure-free survival, while the planning technique was not significant. This large-scale analysis of high-quality implants revealed similar postimplant dosimetry, toxicity profiles and biochemical failure-free survival for the preplanning and intraoperative planning methods.

Improved tumour control probability with MRI-based prostate brachytherapy treatment planning

Backgroun. Due to improved visibility on MRI, contouring of the prostate is improved compared to CT. The aim of this study was to quantify the benefits of using MRI for treatment planning as compared to CT-based planning for temporary implant prostate brachytherapy. Material and methods. CT and MRI image data of 13 patients were used to delineate the prostate and organs at risk (OARs) and to reconstruct the implanted catheters (typically 12). An experienced treatment planner created plans on the CT-based structure sets (CT-plan) and on the MRI-based structure sets (MRI-plan). Then, active dwell-positions and weights of the CT-plans were transferred to the MRI-based structure sets (CT-planMRI-contours) and resulting dosimetric parameters and tumour control probabilities (TCPs) were studied. Results. For the CT-planMRI-contours a statistically significant lower target coverage was detected: mean V100 was 95.1% as opposed to 98.3% for the original plans (p < 0.01). Planning on CT caused cold-spots that influence the TCP. MRI-based planning improved the TCPs by 6–10%, depending on the parameters of the radiobiological model used for TCP calculation. Basing the treatment plan on either CT- or MRI-delineations does not influence plan quality. Conclusion. Evaluation of CT-based treatment planning by transferring the plan to MRI reveals underdosage of the prostate, especially at the base side. Planning on MRI can prevent cold-spots in the tumour and improves the TCP.

Permanent prostate brachytherapy extracapsular radiation dose distributions: analysis of a multi-institutional database

PurposePeriprostatic brachytherapy doses impact biochemical control. In this study, we evaluate extracapsular volumetric dosimetry following permanent prostate brachytherapy in patients entered in a multi-institutional community database.Material and methodsIn the database, 4547 patients underwent brachytherapy (3094 – 125I, 1437 – 103Pd and 16 – 131Cs). Using the originally determined prostate volume, a 5 mm, 3-dimensional peri-prostatic anulus was constructed around the prostate (except for a 2 mm posterior margin), and evaluated in its entirety and in 90° segments. Prostate dosimetric parameters consisted of a V100 and D90 while the annular dosimetry was reported as a V100.ResultsThe intraprostatic V100 and D90 for 103Pd, and 125I were statistically comparable when stratified by isotope and/or monotherapy vs. boost. The overall mean V100 for the periprostatic annulus was 62.8%. The mean V100 at the base (51.6%) was substantially less than the apex (73.5%) and midgland (65.9%). In addition, for all patients, the anterior V100 (45.7%) was less than the lateral (68.8%) and the posterior (75.0%). The geometric V100 annular differences were consistent when evaluated by isotope. Overall, the V100 was higher in the 125I cohort.ConclusionsThe optimal extracapsular brachytherapy dose and radial extent remains unknown, but will prove increasingly important with reductions and/or elimination of supplemental external beam radiation therapy. The large multi-institutional community database demonstrates periprostatic annular doses that are not as robust as those in selected high volume brachytherapy centers, and may be inadequate for optimal biochemical control following monotherapeutic brachytherapy, especially in higher risk patients.

The deep inspiration breath hold technique using Abches reduces cardiac dose in patients undergoing left-sided breast irradiation

PurposeWe explored whether the deep inspiration breath hold (DIBH) technique using Abches during left-sided breast irradiation was effective for minimizing the amount of radiation to the heart and lung compared to free breathing (FB).Materials and MethodsBetween February and July 2012, a total of 25 patients with left-sided breast cancer underwent two computed tomography scans each with the DIBH using Abches and using FB after breast-conserving surgery. The scans were retrospectively replanned using standardized criteria for the purpose of this study. The DIBH plans for each patient were compared with FB plans using dosimetric parameters.ResultsAll patients were successfully treated with the DIBH technique using Abches. Significant differences were found between the DIBH and FB plans for mean heart dose (2.52 vs. 4.53 Gy), heart V30 (16.48 vs. 45.13 cm3), V20 (21.35 vs. 54.55 cm3), mean left anterior descending coronary artery (LAD) dose (16.01 vs. 26.26 Gy, all p < 0.001), and maximal dose to 0.2 cm3 of the LAD (41.65 vs. 47.27 Gy, p = 0.017). The mean left lung dose (7.53 vs. 8.03 Gy, p = 0.073) and lung V20 (14.63% vs. 15.72%, p = 0.060) of DIBH using Abches were not different significantly compared with FB.ConclusionWe report that the use of a DIBH technique using Abches in breathing adapted radiotherapy for left-sided breast cancer is easily feasible in daily practice and significantly reduces the radiation doses to the heart and LAD, therefore potentially reducing cardiac risk.

Stereotactic Body Radiation Therapy Can Be Used Safely to Boost Residual Disease in Locally Advanced Non-Small Cell Lung Cancer: A Prospective Study

To report the results of a prospective, single-institution study evaluating the feasibility of conventional chemoradiation (CRT) followed by stereotactic body radiation therapy (SBRT) as a means of dose escalation for patients with stage II-III non-small cell lung cancer (NSCLC) with residual disease. Patients without metastatic disease and with radiologic evidence of limited residual disease (≤5 cm) within the site of the primary tumor and good or complete nodal responses after standard CRT to a target dose of 60 Gy were considered eligible. The SBRT boost was done to achieve a total combined dose biological equivalent dose >100 Gy to the residual primary tumor, consisting of 10 Gy × 2 fractions (20 Gy total) for peripheral tumors, and 6.5 Gy × 3 fractions (19.5 Gy total) for medial tumors using the Radiation Therapy Oncology Group protocol 0813 definitions. The primary endpoint was the development of grade ≥3 radiation pneumonitis (RP). After a median follow-up of 13 months, 4 patients developed acute grade 3 RP, and 1 (2.9%) developed late and persistent grade 3 RP. No patients developed grade 4 or 5 RP. Mean lung dose, V2.5, V5, V10, and V20 values were calculated for the SBRT boost, and none were found to significantly predict for RP. Only advancing age (P=.0147), previous smoking status (P=.0505), and high CRT mean lung dose (P=.0295) were significantly associated with RP development. At the time of analysis, the actuarial local control rate at the primary tumor site was 82.9%, with only 6 patients demonstrating recurrence. Linear accelerator-based SBRT for dose escalation of limited residual NSCLC after definitive CRT was feasible and did not increase the risk for toxicity above that for standard radiation therapy.

Differences in dose-volumetric data between the analytical anisotropic algorithm and the x-ray voxel Monte Carlo algorithm in stereotactic body radiation therapy for lung cancer

The objective of this study was to evaluate the differences in dose-volumetric data obtained using the analytical anisotropic algorithm (AAA) vs the x-ray voxel Monte Carlo (XVMC) algorithm for stereotactic body radiation therapy (SBRT) for lung cancer. Dose-volumetric data from 20 patients treated with SBRT for solitary lung cancer generated using the iPlan XVMC for the Novalis system consisting of a 6-MV linear accelerator and micro-multileaf collimators were recalculated with the AAA in Eclipse using the same monitor units and identical beam setup. The mean isocenter dose was 100.2% and 98.7% of the prescribed dose according to XVMC and AAA, respectively. Mean values of the maximal dose (Dmax), the minimal dose (Dmin), and dose received by 95% volume (D95) for the planning target volume (PTV) with XVMC were 104.3%, 75.1%, and 86.2%, respectively. When recalculated with the AAA, those values were 100.8%, 77.1%, and 85.4%, respectively. Mean dose parameter values considered for the normal lung, namely the mean lung dose, V5, and V20, were 3.7Gy, 19.4%, and 5.0% for XVMC and 3.6Gy, 18.3%, and 4.7% for the AAA, respectively. All of these dose-volumetric differences between the 2 algorithms were within 5% of the prescribed dose. The effect of PTV size and tumor location, respectively, on the differences in dose parameters for the PTV between the AAA and XVMC was evaluated. A significant effect of the PTV on the difference in D95 between the AAA and XVMC was observed (p = 0.03). Differences in the marginal doses, namely Dmin and D95, were statistically significant between peripherally and centrally located tumors (p = 0.04 and p = 0.02, respectively). Tumor location and volume might have an effect on the differences in dose-volumetric parameters. The differences between AAA and XVMC were considered to be within an acceptable range (<5 percentage points).