Simultaneous Integrated Boost Intensity-modulated Radiotherapy Research Articles

Simultaneous Integrated Boost Intensity‑Modulated Radiotherapy (SIB‑IMRT) in Nasopharyngeal Cancer

To assess the efficacy and safety of using simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) to treat nasopharyngeal cancer (NPC) in a Caucasian cohort. Outcome was analyzed with respect to dose-volume histogram (DVH) values. Between 03/2002 and 01/2008, 39 NPC patients underwent SIB-IMRT (37 Caucasians; 31 males; mean age 53 years [16-78 years]). 41% presented with WHO (World Health Organization) type 1 unfavorable histology, 85% with stage III/IV disease. 19 patients had total gross tumor volume (GTV) 16-70 cm3 (mean 36 cm3), while 16 had GTV > 70 cm3 (73-217 cm3; mean 115 cm3). All patients with stage II-IV disease received concomitant cisplatin. The prescribed SIB dose delivered to the planning target volume (PTV) was 70 Gy (2.00 Gy/fraction) in 17, 69.6 Gy (2.11 Gy/fraction) in 19, and 66 Gy (2.20 Gy/fraction) in three patients. 3-year local relapse-free, nodal relapse-free, distant metastases-free, disease-free rates and overall survival were 86%, 89%, 85%, 72%, and 85% (median follow-up 30 months [8-71 months]). Histology was a significant prognostic factor concerning overall survival, with worst prognosis in WHO type 1 compared to type 2/3 (75% vs. 93%; p = 0.03). There was a trend in favor of WHO type 2/3 regarding local control (74% vs. 94%; p = 0.052). The PTV DVHs showed a slight left shift compared to reported series. Three patients developed grade 3 late effects (xerostomia [n = 2], dysphagia [n = 1], hearing loss [n = 1]). In comparison with predominantly Asian NPC IMRT series in the literature, chemo-IMRT in the own Caucasian cohort, characterized by less radio-responsive WHO type 1, was equally effective. Treatment tolerance was excellent.

Simultaneous Integrated Boost Intensity-Modulated Radiotherapy in Patients With High-Grade Gliomas

We analyzed outcomes of simultaneous integrated boost (SIB) intensity-modulated radiotherapy (IMRT) in patients with high-grade gliomas, compared with a literature review. Forty consecutive patients (WHO grade III, 14 patients; grade IV, 26 patients) treated with SIB-IMRT were analyzed. A dose of 2.0 Gy was delivered to the planning target volume with a SIB of 0.4 Gy to the gross tumor volume with a total dose of 60 Gy to the gross tumor volume and 50 Gy to the planning target volume in 25 fractions during 5 weeks. Twenty patients received temozolomide chemotherapy. At a median follow-up of 13.4 months (range, 3.7-55.9 months), median survival was 14.8 months. One- and 2-year survival rates were 78% and 65%, respectively, for patients with grade III tumors and 56% and 31%, respectively, for patients with grade IV tumors. Age (≤50 vs. >50), grade (III vs. IV), subtype (astrocytoma vs. oligodendroglioma or mixed), and a Zubrod performance score (0-1 vs. >2) were predictive of survival. Of 25 (63%) patients who had recurrences, 17 patients had local failure, 9 patients had regional failure, and 1 patient had distant metastasis. Toxicities were acceptable. SIB-IMRT with the dose/fractionation used in this study is feasible and safe, with a survival outcome similar to the historical control. The shortening of treatment time by using SIB-IMRT may be of value, although further investigation is warranted to prove its survival advantage.

A Prospective Dosimetric Analysis of Patterns of Failure in Head and Neck Cancer Patients Treated with Parotid Sparing Simultaneous Integrated Boost Intensity-modulated Radiotherapy (SIB-IMRT)

A Prospective Dosimetric Analysis of Patterns of Failure in Head and Neck Cancer Patients Treated with Parotid Sparing Simultaneous Integrated Boost Intensity-modulated Radiotherapy (SIB-IMRT)

Carbon-11 acetate PET/CT based dose escalated IMRT in prostate cancer

To demonstrate the theoretical feasibility of [(11)C]acetate PET/CT in delineating the malignant intraprostatic lesions (IPL's) in prostate cancer and to use the data in external beam radiotherapy to boost the biologically defined target volume (BTV). Twelve men with intracapsular prostate carcinoma were imaged with [(11)C]acetate PET/CT and the data were used to delineate the BTV. Six dynamic IMRT plans were generated to each patient: a standard IMRT (sIMRT) plan with a 77.9 Gy dose to PTV (prostate gland with a 6-mm margin) and a simultaneous integrated boost IMRT (SIB(IMRT)) plan to deliver 77.9 Gy, 81 Gy, 84 Gy, 87 Gy and 90 Gy to the BTV and 72 Gy to the rest of PTV. To study the theoretical dose escalation based on the delineation of BTV, tumor control probabilities (TCPs) and normal tissue complication probabilities (NTCPs) of bladder and rectum were calculated and compared between the treatment plans. [(11)C]Acetate was used to delineate the IPL's of all 12 patients. With every patient the TCP was increased with SIB(IMRT) without increasing the NTCP of the bladder or rectum. The probability of uncomplicated control (PUC) was increased on average by 28% with the SIB(IMRT) treatment plans. The highest PUC was achieved with an average dose of 82.1 Gy to the BTV. Our study indicates that [(11)C]acetate can be used to define the IPL's and in combination with SIB(IMRT) the defined areas can theoretically be treated to ultra high doses without increasing the treatment toxicity. These results motivate the formal validation of [(11)C]acetate PET for biological dose planning in prostate cancer.

Acute Toxicities Experienced during Simultaneous Integrated Boost Intensity-modulated Radiotherapy in Head and Neck Cancers — Experience from a North Indian Regional Cancer Centre

Aim A prospective study was conducted to assess the feasibility of simultaneous integrated boost intensity-modulated radiotherapy (SIB IMRT) in our setting. Acute toxicities encountered during and immediately after treatment are reported. Materials and methods Acute toxicity data prospectively collected during the treatment of the evaluable 28 patients with two SIB IMRT schedules were analysed. Toxicity was graded using the Common Terminology Criteria for Adverse Events version 3.0 system. Twenty-one patients were treated with the SIB72 schedule, delivering 72, 66 and 57 Gy in 33 fractions to the gross tumour volume, the high-risk clinical target volume and the low-risk clinical target volume, respectively, whereas seven patients were treated with the SIB66 schedule, delivering 66, 60 and 54 Gy in 30 fractions to the above volumes. No chemotherapy was given during the course of treatment. Descriptive analysis of the incidence and actuarial analysis of the duration of toxicities are presented. Results Grade 3 or greater acute mucosal and actinic toxicity were seen 42.9 and 14.3% of the patients, respectively. Mucosal toxicity appeared by the second week in most patients. Atypical patterns of mucositis were encountered, including one patient with prolonged grade 4 mucosal ulceration in the SIB72 schedule. Grade 3 weight loss was seen in 10.57% of patients. Grade 3 pain was seen in 70% and grade 3 dysphagia in 10% during treatment. Conclusion SIB IMRT as used in this study was feasible, although associated with increased rates of mucosal and dermal toxicity.

Evaluation of Spatially Fractionated Radiotherapy (GRID) and Definitive Chemoradiotherapy With Curative Intent for Locally Advanced Squamous Cell Carcinoma of the Head and Neck: Initial Response Rates and Toxicity

To present results and acute toxicity in 14 patients with bulky (>or=6 cm) tumors from locally advanced squamous cell carcinoma of the head and neck who received spatially fractionated radiotherapy (GRID) therapy to the bulky mass followed by concomitant chemoradiotherapy using simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT). GRID therapy to the GTV was delivered by creating one treatment field with a checkerboard pattern composed of open-closed areas using a multileaf collimator. The GRID prescription was 20 Gy in one fraction. Chemotherapy started the day of GRID therapy and continued throughout the course of SIB-IMRT. The SIB-IMRT prescription was 66, 60, and 54 Gy to the planning target volume (PTV), intermediate-risk PTV, and low-risk PTV, respectively, in 30 fractions. With a median follow-up of 19.5 months (range, 2-38 months), the overall control rate of the GRID gross tumor volume was 79% (11 of 14). The most common acute skin and mucosal toxicities were Grade 3 and 2, respectively. For the treatment of locally advanced neck squamous cell carcinoma of the head and neck, GRID followed by chemotherapy and SIB-IMRT is well tolerated and yields encouraging clinical and pathologic responses, with similar acute toxicity profiles as in patients receiving chemoradiotherapy without GRID.

SU-FF-T-515: NCTP Of Bladder And Rectum : Does Simultaneous Integrated Boost IMRT Score Over Other Techniques

Purpose: The main objective of this study was to analyze the radiobiological effect of different treatment strategies in high risk adenocarcinoma prostate. Method and Materials: Ten cases of high risk adenocarcinoma prostate were selected for this dosimetric study. Four different treatment strategies used for treating prostate cancer were compared. Conventional four‐field box technique covering prostate and nodal volumes followed by three‐field conformal boost (3D+3DCRT), four‐field box technique followed by intensity modulated radiotherapy(IMRT) boost (3D+IMRT), IMRT followed by IMRT boost (IMRT+IMRT) and simultaneous integrated boost IMRT (SIBIMRT) were compared in terms of tumorcontrol probability (TCP) and normal tissue complication probability (NTCP). The dose prescription except for SIBIMRT was 45Gy in 25 fractions for the prostate and nodal volumes in the initial phase and 27Gy in 15 fractions to the prostate in the boost phase. For SIBIMRT, equivalent doses were calculated using biologically equivalent dose (BED) assuming α/β of 1.5Gy with dose prescription of 60.75Gy to GTV and 45Gy to CTV in 25 fractions. IMRT plans were made with 15MV equi‐spaced seven coplanar fields. NTCP was calculated using Lyman‐Kutcher‐Burman (LKB) model. Results: A NTCP of 10.7±0.99%, 8.36±0.66%, 6.72±0.85%,1.45±0.11% for bladder and 14.9±0.99%, 14.04±0.66%, 11.38±0.85%, 5.12±0.11% for rectum was seen with 3D+3DCRT, 3D+IMRT, IMRT+IMRT and SIB‐IMRT respectively. Conclusions: SIBIMRT had the least NTCP over all other strategies with reduced treatment time (3 weeks less). It should be the technique of choice for dose escalation in prostate carcinoma.

Normal tissue complication probability: Does simultaneous integrated boost intensity-modulated radiotherapy score over other techniques in treatment of prostate adenocarcinoma

The main objective of this study was to analyze the radiobiological effect of different treatment strategies on high-risk prostate adenocarcinoma. Ten cases of high-risk prostate adenocarcinoma were selected for this dosimetric study. Four different treatment strategies used for treating prostate cancer were compared. Conventional four-field box technique covering prostate and nodal volumes followed by three-field conformal boost (3D + 3DCRT), four-field box technique followed by intensity-modulated radiotherapy (IMRT) boost (3D + IMRT), IMRT followed by IMRT boost (IMRT + IMRT), and simultaneous integrated boost IMRT (SIBIMRT) were compared in terms of tumor control probability (TCP) and normal tissue complication probability (NTCP). The dose prescription except for SIBIMRT was 45 Gy in 25 fractions for the prostate and nodal volumes in the initial phase and 27 Gy in 15 fractions for the prostate in the boost phase. For SIBIMRT, equivalent doses were calculated using biologically equivalent dose assuming the alpha/beta ratio of 1.5 Gy with a dose prescription of 60.75 Gy for the gross tumor volume (GTV) and 45 Gy for the clinical target volume in 25 fractions. IMRT plans were made with 15-MV equispaced seven coplanar fields. NTCP was calculated using the Lyman-Kutcher-Burman (LKB) model. An NTCP of 10.7 +/- 0.99%, 8.36 +/- 0.66%, 6.72 +/- 0.85%, and 1.45 +/- 0.11% for the bladder and 14.9 +/- 0.99%, 14.04 +/- 0.66%, 11.38 +/- 0.85%, 5.12 +/- 0.11% for the rectum was seen with 3D + 3DCRT, 3D + IMRT, IMRT + IMRT, and SIBIMRT respectively. SIBIMRT had the least NTCP over all other strategies with a reduced treatment time (3 weeks less). It should be the technique of choice for dose escalation in prostate carcinoma.

Static versus dynamic intensity-modulated radiotherapy: Profile of integral dose in carcinoma of the nasopharynx

This study is aimed to evaluate the impact of static and dynamic intensity modulated radiotherapy (IMRT) delivery techniques planned with Eclipse TPS on the integral dose to the healthy normal tissue surrounding the tumor-bearing area and to the volume receiving doses < 5 Gy in patients with carcinoma nasopharynx treated with Simultaneous Integrated Boost IMRT (SIB-IMRT). Ten patients with carcinoma nasopharynx were chosen for this dosimetric study. IMRT plans were generated with 6X using dynamic multileaf collimator (DMLC) and static multileaf collimator (SMLC) with 5, 10 and 15 intensity levels (L). Integral dose, volume receiving 5 Gy, number of monitor units (MU) is compared against DMLC. The mean difference in the MU delivered per fraction between 5, 10 and 15 L SMLC and DMLC was −13.25% (P < 0.001, with paired t test), −11.82% (P < 0.001) and −10.81% (P < 0.001), respectively. The mean difference in the integral dose with 5, 10 and 15 L compared to DMLC was −2.96% (P < 0.001), −2.67% (P = 0.016) and −0.39% (P = 0.430), respectively. However, the difference in low-dose volume (V5Gy) was statistically insignificant with mean difference of 0.60% (P = 0.23), 1.18% (P = 0.017) and 1.70% (P = 0.078), respectively for 5, 10 and 15 L compared to DMLC. Our results show that while choosing the IMRT delivery technique using conventional MLC the concerns about integral dose and volume receiving very low doses such as 5 Gy can be ignored.

Impact of the Width of Multileaf Collimator on Simultaneous Integrated Boost Intensity-modulated Radiotherapy for Prostate Cancer

Impact of the Width of Multileaf Collimator on Simultaneous Integrated Boost Intensity-modulated Radiotherapy for Prostate Cancer

TU‐D‐AUD B‐04: A Dosimetric Comparison of Simultaneous Integrated Breast Radiotherapy Using 3D Conformal, IMRT and Tomotherapy Techniques

Purpose: The dosimetric characteristics of simultaneous integrated boost (SIB) breast radiotherapy techniques utilizing 3D‐conformal (3DSIB), linac‐based intensity modulation (IMRT) and Tomotherapy (TOMO) were compared. The SIB techniques were compared to conventional whole breast irradiation (WBI). Method and Materials: Fifteen patients were included in the study. The SIB treatments (3DSIB, IMRT and TOMO) delivered 45Gy(25×1.8Gy) to the whole breast minus the boost bed, PTV(Breast‐Boost), and concurrently delivered 60Gy(25×2.4Gy) to the tumor bed, PTV(Boost). The WBI treatment delivered 45Gy(25×1.8Gy) the whole breast, PTV(Breast), followed by 20Gy(10×2Gy) to PTV(Boost). The WBI and SIB treatment were planned to deliver equivalent dose to the targets. Statistical significance between dosimetric parameters was determined using Wilcoxon signed‐ranks. The dosimetric data were compiled to form population dose volume histograms which display the mean value and 1σ uncertainty. Dose homogeneity was quantified by the parameter D95%−5%, representing the percent difference in dose covering 95% of the target minus the dose covering 5% of the target. Results: Using the D95%−5% parameter the PTV(Breast‐Boost) volume received a more homogeneous dose using TOMO(14.3%) compared to 3DSIB(25.1%), IMRT(27.1%) and WBI(44.7%). The PTV(Boost) volume received a morehomogeneous dose using non‐intensity modulated techniques, WBI(6.9%) and 3DSIB(7.0%), compared to IMRT(11.6%) and TOMO(12.0%). The mean percent volume of ipsilateral lung that received ⩾20Gy was smaller using IMRT(15.8%) compared to 3DSIB(17.7%), TOMO(17.1%) and WBI(19.0%). For left‐sided breast cancer patients, the mean percent volume of heart that received ⩾35Gy was less for intensity modulated SIB techniques, IMRT(0.1%) and TOMO(0.2%), than 3DSIB(4.4%), and WBI(6.2%). The contralateral breast received a smaller mean dose using IMRT(0.39Gy) compared to WBI(0.81Gy), 3DSIB(0.67Gy) and TOMO(1.28Gy). Conclusion: IB techniques delivered a more homogenous dose to the PTV(Breast‐Boost) volume, while non‐intensity modulated techniques delivered a more homogeneous dose to the PTV(Boost) volume. Intensity modulated SIB techniques (IMRT and TOMO) decreased the heart dose relative to 3DSIB.

The Predictive Value of Degree of PTV-OAR Overlap on Achieving Parotid Dose Constraints in Head and Neck Simultaneous Integrated Boost-Intensity Modulated Radiation Therapy (SIB-IMRT)

The Predictive Value of Degree of PTV-OAR Overlap on Achieving Parotid Dose Constraints in Head and Neck Simultaneous Integrated Boost-Intensity Modulated Radiation Therapy (SIB-IMRT)

Simultaneous-integrated boost intensity-modulated radiation therapy (SIB-IMRT) in the treatment of early-stage left-sided breast carcinoma

We assessed the feasibility and impact of simultaneous-integrated boost intensity-modulated radiation therapy (SIB-IMRT) in the treatment of left breast carcinoma and compared target coverage and normal tissue doses with SIB-IMRT and 3-dimensional (3D) conformal RT using opposed tangential fields. For each of 10 patients with early-stage left-sided invasive breast carcinoma, 5 plans were generated; the first 4 were 3D conformal opposed tangential fields—2 with wedges, 2 with compensators and either photon or electron boost. A dose of 50.4 Gy in 28 fractions was prescribed to the left breast and an additional 16 Gy in 8 fractions to the lumpectomy bed. When compared to the tangential plans, SIB-IMRT maintained coverage (V 95%) to the left breast and lumpectomy bed without significantly increasing the left breast maximum dose. SIB-IMRT was able to reduce the lung mean dose, maximum dose, and the V 20 by 55–104 cGy, 983–1298 cGy ( p < 0.001), and 3.7–4.4%, respectively. In addition, SIB-IMRT reduced the maximum heart dose by 1032–1173 cGy and contralateral breast dose was increased (although p = NS). The mean and maximum dose to the unspecified tissues was also significantly reduced by 81–88 cGy and 516–942 cGy, respectively. SIB-IMRT resulted in a significant improvement in target dose conformality by up to 67%. Our findings that SIB-IMRT could improve dose conformality, reduce total treatment times, and reduce some of the normal structure doses presents it as an alternative technique for adjuvant breast radiotherapy; however this needs to be studied further in the clinic setting.

SU‐FF‐T‐361: Planning Study of Intensity‐Modulated and 3D Conformal Radiotherapy of Whole Pelvis Including Inguinal Lymphatics: Radiobiological Considerations for Designing New Fractionation Schemes

Purpose: To examine the possibility of using “simultaneous integrated boost” intensity‐modulated radiotherapy (SIB‐IMRT), for the management of pelvic malignancies, with potential clinical advantage for simultaneous delivery of high doses to the primary disease and lower doses to the subclinical disease or electively treated regions.Method and Materials: For this study, a sample patient diagnosed with anal cancer was randomly selected from our database. Four treatment plans were developed: (1) the 3D conformal plan for initial pelvis/inguinal node irradiation and subsequent conventional 3D boost to the primary tumor, (2) conventional 3D initial pelvis/inguinal node irradiation and subsequent IMRT boost plan, (3) Two‐phase IMRT plan for initial pelvis/inguinal node irradiation and subsequent IMRT boost plan, (4) A single‐phase SIB‐IMRT plan to deliver simultaneous boost. DVHs for the target volumes were transformed into equivalent uniform dose (EUD) using the LQ model to evaluate relative merits of these plans using tumor control probability (TCP), and normal tissue complication probability (NTCP) for normal tissues.Results: We have found that dose distributions for SIB‐IMRT are similar in conformality to dose distributions when IMRT is divided into a large‐field phase and a boost phase. As shown in Fig. 1(a–d), both techniques produce significantly superior dose distributions compared to those obtained with 3DCRT as well as to dose distributions obtained using conventional beams for the large‐field phase followed by IMRT boost phase. We also found that normal tissues outside the target volume receive significantly lower dose due to higher dose conformality of IMRT plans (Table 1). Conclusions: SIB‐IMRT offers unique ability to produce highly conformal dose distributions with better sparing of organs at risk, with more efficient delivery, and shorter treatment duration. This new modality also facilitates the prospect of dose escalation to highly advanced tumors for better radiobiological effectiveness potentially leading to improved outcome.

IMRT in Hypopharyngeal Tumors

Intensity-modulated radiation therapy (IMRT) data on hypopharyngeal cancer (HC) are scant. In this study, the authors report on early results in an own HC patient cohort treated with IMRT. A more favorable outcome as compared to historical data on conventional radiation techniques was expected. 29 consecutive HC patients were treated with simultaneous integrated boost (SIB) IMRT between 01/2002 and 07/2005 (mean follow-up 16 months, range 4-44 months). Doses of 60-71 Gy with 2.0-2.2 Gy/fraction were applied. 26/29 patients were definitively irradiated, 86% received simultaneous cisplatin-based chemotherapy. 60% presented with locally advanced disease (T3/4 Nx, Tx N2c/3). Mean primary tumor volume measured 36.2 cm(3) (4-170 cm(3)), mean nodal volume 16.6 cm(3) (0-97 cm(3)). 2-year actuarial local, nodal, distant control, and overall disease-free survival were 90%, 93%, 93%, and 90%, respectively. In 2/4 patients with persistent disease (nodal in one, primary in three), salvage surgery was performed. The mean dose to the spinal cord (extension of > 5-15 mm) was 26 Gy (12-38 Gy); the mean maximum (point) dose was 44.4 Gy (26-58.9 Gy). One grade (G) 3 dysphagia and two G4 reactions (laryngeal fibrosis, dysphagia), both following the schedule with 2.2 Gy per fraction, have been observed so far. Larynx preservation was achieved in 25/26 of the definitively irradiated patients (one underwent a salvage laryngectomy); 23 had no or minimal dysphagia (G0-1). Excellent early disease control and high patient satisfaction with swallowing function in HC following SIB IMRT were observed; these results need to be confirmed based on a longer follow-up period. In order to avoid G4 reactions, SIB doses of < 2.2 Gy/fraction are recommended for large tumors involving laryngeal structures.

WE-D-224A-08: Monte Carlo Dose Verification of Prostate Patients Treated with Simultaneous Integrated Boost IMRT

Purpose: To evaluate the dosimetric accuracy of Superposition/Convolution (SC) and Monte Carlo (MC) calculated dose distributions for simultaneous integrated boost (SIB) prostate cancerintensity modulated radiotherapy(IMRT) compared to experimental (film) measurements and the implications for clinical treatments.Method and Materials: Twenty prostate patients treated with in‐house SIB‐IMRT protocol were selected. SC‐based plans used for treatment were reevaluated with EGS4‐based MC calculations for treatment verification. Accuracy was evaluated with‐respect‐to film‐based dosimetry. Comparisons used γ‐index, DTA, and superimposed dose distributions. The treatment plans were also compared based on dose‐volume indices for targets and critical structures. Results: Flat‐phantom comparisons demonstrated that the MC algorithm predicted measurements better than the SC algorithm (%γ>1 8.4% for MC vs. 18.3% for SC). The average PTVprostate D98 and PTVnodes D95 indices agreement between SC and MC was 1.2%±1.1 (range: −38%, ±0.1%) and 1.6%±1.5 (range: 3.6%, 0.6%) respectively. For rectum, the average differences in SC and MC calculated D50 ranged from −3.6% to 3.4%. There were up to 34.3%±42.5 (range: 0.2%, 115%) differences between SC and MC calculated average D50 index for small bowel. This large deviation is due to large differences in small bowel volume within the treatment field and small bowel dose for each patient. For femurs, the differences in average D50 reached up to 9.6%±4.5 (range: 1.2%, 14.5%). Conclusion:MC agrees better with film measurements than SC. Although on average SC‐calculated doses agreed with MC calculations within the targets within 2%, there were deviations >10% for some patient's treatment plans. The major source of these deviations may be due to the inaccuracies in fluence prediction model for SC calculation. The use of SC may compromise the clinical outcome of patients and MC‐based IMRT would be beneficial for IMRT plan optimization. (Supported by NIH‐R0198524).