Boost Treatment Plans Research Articles

Dosimetric comparison of five different radiotherapy treatment planning approaches for locally advanced non-small cell lung cancer with sequential plan changes.

The purpose of this study was to compare the dosimetric characteristics of five different treatment planning techniques for locally advanced non-small cell lung cancer (LA-NSCLC) with sequential plan changes. A total of 13 stage III NSCLC patients were enrolled in this study. These patients had both computed tomography (CT) images for initial and boost treatment plans. The latter CT images were taken if tumor shrinkage was observed after 2 weeks of treatment. The prescription dose was 60 Gy/30 Fr (initial: 40 Gy/20 Fr, and boost: 20 Gy/10 Fr). Five techniques (forward-planed 3-dimensional conformal radiotherapy [F-3DCRT] on both CT images, inverse-planned 3DCRT [I-3DCRT] on both CT images, volumetric modulated arc therapy [VMAT] on both CT images, F-3DCRT on initial CT plus VMAT on boost CT [bVMAT], and hybrid of fixed intensity-modulated radiotherapy [IMRT] beams and VMAT beams on both CT images [hybrid]) were recalculated for all patients. The accumulated doses between initial and boost plans were compared among all treatment techniques. The conformity indexes (CI) of the planning target volume (PTV) of the five planning techniques were 0.34 ± 0.10, 0.57 ± 0.10, 0.86 ± 0.08, 0.61 ± 0.12, and 0.83 ± 0.11 for F-3DCRT, I-3DCRT, VMAT, bVMAT, and hybrid, respectively. In the same manner, lung volumes receiving >20 Gy (V20Gy ) were 21.05 ± 10.56%, 20.86 ± 6.45, 19.50 ± 7.38%, 19.98 ± 10.04%, and 17.74 ± 7.86%. There was significant improvement about CI and V20Gy for hybrid compared with F-3DCRT (p < 0.05). The IMRT/VMAT hybrid technique for LA-NSCLC patients improved target CI and reduced lung doses. Furthermore, if IMRT was not available initially, starting with 3DCRT might be beneficial as demonstrated in the bVMAT procedure of this study.

Boost modalities in cervical cancer: dosimetric comparison between intracavitary BT vs. intracavitary + interstitial BT vs. SBRT.

Purpose / objectiveThis study compares the dosimetric plans of three distinct boost modalities in cervical cancer (CC): intracavitary (IC) with tandem/ovoids brachytherapy (BT), IC + interstitial (IS) BT, and Stereotactic-Body-Radiotherapy (SBRT). The aim is to determine the dosimetric impact in terms of target coverage and organ at risk (OAR) doses.Materials and methods24 consecutive IC + IS BT boost treatment plans were retrospectively identified. For each plan included, two additional plans were created: IC-BT and SBRT. Importantly, no planning target volume (PTV) or planning (organ at) risk volume (PRV) margins were generated, therefore all structures were identical for any boost modality. Two different normalizations were performed: (1) Normalization to the target: prescription of 7.1 Gy to the D90% (defined as the minimum dose covering 90%) of the high-risk clinical target volume (HR-CTV); (2) Normalization to the OARs. HR-CTV coverage and OARs sparing were compared. The equivalent doses in 2 Gy fractions (EQD2) of EBRT and BT for CTV-HR and OARs were calculated using the linear-quadratic model with α/β of 10 (EQD210) and 3 (EQD23), respectivelyResultsA total of 72 plans were investigated. In the first normalization, the mean EQD23−D2cc (defined as the minimal dose of the 2 cc) of OAR was significantly higher in the IC-BT plans, and the bladder D2cc hard constraint could not be reached. IC + IS BT leads to a 1 Gy mean absolute decrease of bladder EQD23-D2cc (relative dose: -19%), allowing to reach the hard constraint. SBRT (without PTV) delivers the lowest EQD23-D2cc to the OAR. In the second normalization, IC-BT provides a significantly lower dose to the EQD210-D90% (6.62 Gy) and cannot achieve the coverage goal. SBRT (without PTV) yields the highest dose to the D90% of HR-CTV and a significantly lower EQD210-D50% and D30%.ConclusionThe key dosimetric benefit of BT over SBRT without PTV is a significantly higher D50% and D30% in the HR-CTV, which increases the local and conformal dose to the target. IC + IS BT vs. IC-BT provides significantly better target coverage and a lower dose to the OARs, making it the preferred boost modality in CC.

Urethral and bladder dose–effect relations for late genitourinary toxicity following external beam radiotherapy for prostate cancer in the FLAME trial

Purpose or objectivesThe FLAME trial (NCT01168479) showed that by adding a focal boost to conventional fractionated EBRT in the treatment of localized prostate cancer, the five-year biochemical disease-free survival increased, without significantly increasing toxicity. The aim of the present study was to investigate the association between radiation dose to the bladder and urethra and genitourinary (GU) toxicity grade ≥2 in the entire cohort. Material and methodsThe dose–effect relations of the urethra and bladder dose, separately, and GU toxicity grade ≥2 (CTCAE 3.0) up to five years after treatment were assessed. A mixed model analysis for repeated measurements was used, adjusting for age, diabetes mellitus, T-stage, baseline GU toxicity grade ≥1 and institute. Additionally, the association between the dose and separate GU toxicity subdomains were investigated. ResultsDose-effect relations were observed for the dose (Gy) to the bladder D2 cm3 and urethra D0.1 cm3, with adjusted odds ratios of 1.14 (95% CI 1.12–1.16, p < 0.0001) and 1.12 (95% CI 1.11–1.14, p < 0.0001), respectively. Additionally, associations between the dose to the urethra and bladder and the subdomains urinary frequency, urinary retention and urinary incontinence were observed. ConclusionFurther increasing the dose to the bladder and urethra will result in a significant increase in GU toxicity following EBRT. Focal boost treatment plans should incorporate a urethral dose-constraint. Further treatment optimization to increase the focal boost dose without increasing the dose to the urethra and other organs at risk should be a focus for future research, as we have shown that a focal boost is beneficial in the treatment of prostate cancer.

Risk estimation of second primary cancers after breast radiotherapy

Aims: There is evidence towards the induction of second primary cancers (SPCs) after breast radiotherapy (RT). Organs, such as the lungs and the esophagus, have been identified as common sites for SPC formation. As a result, the current study investigated the risk of secondary carcinogenesis associated with particular RT techniques for breast cancer; including whole breast, segmented breast, partial breast and mammosite brachytherapy.Methods: In this study, seven breast cancer patients had all major organs contoured on their planning computed tomography (CT) images. Whole breast, segmented breast, accelerated partial breast irradiation (APBI) and mammosite boost treatment plans were generated for each patient using Pinnacle3 treatment planning system. Differential dose-volume histograms were generated for a number of critical structures: bladder, brain and central nervous system (CNS), breast, colon, liver, lung, mouth and pharynx, esophagus, ovary, salivary gland, small intestine, stomach, and uterus. The lifetime attributed risk (LAR) of cancer induction was estimated using the Schneider et al. excess absolute risk models and dose-volume histograms for the above organs.Results: The sites with the highest LAR estimates were the ipsilateral and contralateral lungs, and contralateral breast for all treatment techniques. For all sites, the LAR estimates for the segmented breast and mammosite treatments were lower than those for the whole breast and APBI treatments. For right-sided target volumes the liver also resulted in high LAR estimates, with all techniques having a LAR greater than 20 per 10 000 person-years (PY), except for mammosite with a mean LAR estimate of 13.2 per 10 000 PY. For left-sided target volumes the stomach also resulted in high LAR estimates, with both whole breast and APBI having a LAR greater than 20 per 10 000 PY, and mammosite the lowest with a LAR of 8.3 per 10 000 PY.Conclusion: It is concluded that the lungs and contralateral breast showed high LAR estimates.

Is there a preferred IMRT technique for left-breast irradiation?

Not all clinics have breath‐hold radiotherapy available for left‐breast irradiation. However intensity‐modulated radiotherapy (IMRT) has also been advocated as a means of lowering heart doses. There is currently no large‐scale, long‐term follow‐up data after breast IMRT and, since dose distributions may differ from classic tangent‐based radiotherapy, caution is needed to avoid unexpected worsening of the late toxicity profile. We compared four IMRT techniques for free‐breathing left‐breast irradiation. Consistent with the aforementioned concerns, our goal in planning was to prioritize organ at risk (OAR) sparing in a way that mimicked tangent‐based radiotherapy. Ten simultaneous integrated boost treatment plans (PTVelective=15×2.67 Gy;PTVboost=15×3.35 Gy) were created using 1) hybrid‐IMRT (H‐IMRT), 2) full IMRT (F‐IMRT), and 3) volumetric‐modulated arc therapy with two partial arcs (2ARC) and 4) six partial arcs (6ARC). Reduction in OAR mean and low dose was prioritized. End‐points included OAR sparing (e.g., heart, left anterior descending artery [LAD+3 mm], lungs, and contralateral breast) and PTV coverage/dose homogeneity. Under these conditions we found the following: 1) H‐IMRT provided the best mean and low dose OAR sparing, PTVelective coverage (mean V95%=98%),PTVboost coverage (V95%=98%), and PTV homogeneity. However, it delivered most intermediate–high dose to the heart, LAD+3 mm and ipsilateral lung; 2) 6ARC had the best intermediate–high dose sparing, followed by F‐IMRT, but this was at the expense of more dose in the contralateral lung and breast and worse PTV coverage (PTVelective mean V95%=96%/97% and PTVboost mean V95%=91%/96% for 6ARC/F‐IMRT). When trying to spare mean and low dose to OARs, the preferred IMRT technique for left‐breast irradiation without breath‐hold was H‐IMRT. This is currently the standard solution in our institution for left‐breast radiotherapy under free‐breathing and breath‐hold conditions.PACS numbers: 87.53kn, 87.53Jw, 87.55.D‐, 87.55.de, 87.55.dk

Delivering Multiparametric MRI-Guided High-Dose-Rate Brachytherapy Boost in Nonmetastatic Prostate Cancer

In localized prostate cancer, dominant intra-prostatic lesions (DiLs) of gross tumor are thought to drive metastatic potential. Tumour control and overall cancer control may be improved if DiLs are targeted with escalated radiation dose. This pilot study investigated the feasibility of focal high dose rate (HDR) brachytherapy boost in a cohort of patients treated with combined EBRT and HDR brachytherapy. Multi-parametric MRI (mp-MRI) was used and feasibility assessed in terms of (i) whether tumor tissue can be identified using mp-MRI (ii) the focal boost dose that can be delivered to the tumor within normal tissue dose constraints and (iii) treatment related toxicities. Thirty patients were recruited and mp-MRI scans performed in the week before HDR brachytherapy treatment. For focal boost treatment plans, focal-planning target volumes (F-PTVs) were identified which were the visible tumor plus a margin of 4.5mm, constrained to the prostate capsule. F-PTV dose was boosted as much as possible while maintaining standard treatment planning objectives (prescribed dose 15Gy to the whole prostate in one fraction) and normal tissue dose constraints. For the first 15 patients, focal boost treatment plans were produced retrospectively. For the subsequent 15 patients the focal boost treatment was delivered if an F-PTV could be identified from the mp-MRI data. Gastro-intestinal and genitourinary toxicity was recorded using CTCAE v4.0 at 6 weeks and then 3 monthly intervals following treatment. In the retrospective study F-PTVs were identified for all 15 patients and focal boost treatment plans achieved mean F-PTV D90 of 21.4 Gy compared to 17.8 Gy in the delivered treatments. In the subsequent cohort of patients, no tumor was visible in the mp-MRI data for 3 patients, 2 patients were determined to be unfit for surgery after the MRI scan and 2 were unable to have scans for logistical reasons. 8 patients received the focal boost treatment with dose escalated to achieve mean F-PTV D90 of 22.0 Gy. Dose escalation had no impact on urethra D10 (mean 17.1 Gy) and increased rectal D2cc by 3% (to 8.9 Gy). In the patients treated with F-PTV boost no Grade 3 toxicities were seen and 3 of 8 patients had Grade 2 or less toxicity in the first 3 months. Multi-parametric MRI guided HDR prostate brachytherapy tumour boost is feasible. It is possible to identify tumour regions within the prostate in the majority of patients, and to achieve significant increased dose to DiLs without violating urethral and rectal dose constraints or increasing treatment induced toxicities.

The Effect of Image Guidance on Dose Distributions in Breast Boost Radiotherapy

AimsTo determine the effect of image-guided radiotherapy on the dose distributions in breast boost treatments. Materials and methodsComputed tomography images from a cohort of 60 patients treated within the IMPORT HIGH trial (CRUK/06/003) were used to create sequential and concomitant boost treatment plans (30 cases each). Two treatment plans were created for each case using tumour bed planning target volume (PTV) margins of 5 mm (achieved with image-guided radiotherapy) and 8 mm (required for bony anatomy verification). Dose data were collected for breast, lung and heart; differences with margin size were tested for statistical significance. ResultsA median decrease of 29 cm3 (range 11–193 cm3) of breast tissue receiving 95% of the prescribed dose was observed where image-guided radiotherapy margins were used. Decreases in doses to lungs, contralateral breast and heart were modest, but statistically significant (P < 0.01). Plan quality was compromised with the 8 mm PTV margin in one in eight sequential boost plans and one third of concomitant boost plans. Tumour bed PTV coverage was <95% (>91%) of the prescribed dose in 12 cases; in addition, the required partial breast median dose was exceeded in nine concomitant boost cases by 0.5–3.7 Gy. ConclusionsThe use of image guidance and, hence, a reduced tumour bed PTV margin, in breast boost radiotherapy resulted in a modest reduction in radiation dose to breast, lung and heart tissues. Reduced margins enabled by image guidance were necessary to discriminate between dose levels to multiple PTVs in the concomitant breast boost plans investigated.

Multi-parametric MRI-guided focal tumor boost using HDR prostate brachytherapy: A feasibility study

This study investigates the feasibility of delivering focal boost dose to tumor regions, identified with multi-parametric MRI, in high-dose-rate prostate brachytherapy. T2-weighted, diffusion-weighted, and dynamic-contrast-enhanced MRI were acquired the day before treatment and analyzed retrospectively for 15 patients. Twelve patients had hormone therapy before the MRI scan. The tumor was delineated on MRI by a radiologist and registered to treatment planning transrectal ultrasound images. A margin based on analysis of delineation and registration uncertainties was applied to create a focal boost planning target volume (F-PTV). Delivered treatment plans were compared with focal boost plans optimized to increase F-PTV dose as much as allowed by urethral and rectal dose constraints. Tumors were delineated in all patients with volumes 0.4-23.0cc. The margin for tumor delineation and image registration uncertainties was estimated to be 4.5mm. For F-PTV, the focal boost treatment plans increased median D90 from 17.6 to 20.9Gy and median V150 from 27.3% to 75.9%. MRI-guided high-dose-rate prostate brachytherapy focal tumor boost is feasible-tumor regions can be identified even after hormone therapy, and focal boost dose can be delivered without violating urethral and rectal dose constraints.

SU-E-T-714: Analysis of Two Overall Biological Effective Dose (OBED) Calculation Methods and Their Impact On the Accurate Determination of the Maximum Biological Effective Dose (BED) in Multi-Phase Treatment Plans

Purpose: To evaluate the accuracy of calculating the overall biological effective dose (OBED) distribution of multi‐phase treatment plans by summing up the physical doses of the individual beam configurations prior their conversion to BED. Methods: MATLAB 2010a was used to calculate the OBED using the dose distribution matrices of a patients initial and boost treatment plans from Pinnacle. The OBED was calculated using two different methods. Method ‐ A adds the physical doses from the initial and boost treatment plans, and then converts those values into BED to produce an approximate OBED. Method‐B converts the physical doses for each plan into BED before adding them to produce the true OBED. The latter method uses the true mathematical approach and hence will be used as reference when comparing the results acquired by the two methods. Mathematically, if the average dose per fraction ( ADPF) for the initial ( ADPF1 ) and boosting ( ADPF2) plans are equal, then the approximate OBED should be equal to the true OBED. However, the larger the difference between the ADPFs is, the larger the difference between the OBEDs will be. Results: ADPF1 was 1.59 Gy and ADPF2 was 1.34 Gy hence the percent difference between the OBEDs was −0.09 ± 0.09 percent. The average, maximum, and minimum values within the OBED for method‐A were 56.6 Gy, 67.2 Gy, and 53.2 Gy while those values within the OBED for method B were 56.7 Gy, 67.3 Gy, and 53.3 Gy. Conclusion: Method ‐ A can produce accurate approximations to the true OBED if the ADPF of each plan is approximately equal. This leads to an accurate determination of the maximum BED limit when optimizing multiphase treatment plans. Current treatment planning systems do not have the capability to perform calculations based on method‐B, but using the dose volume histograms, method‐A can be performed manually.

SU-E-T-460: Isoeffective Dose Display (EQD2) for Composite Plan of Radiosurgery and Conventional 3D Radiotherapy.

Direct addition of doses between plans with different fractionation fails to provide accurate dose-response information to anticipate clinical outcome. To combine different fractionation patterns, first-order biological model correction for dose-rate must be included. Moreover, 3-D isoeffect patterns of the combined doses must be displayed so that overlap area to elegant volumes can be avoided. The linear quadratic (LQ) model and biologically effective dose (BED) method were used to produce a combined plan in equivalent 2 Gy fractions (EQD2) for radiosurgery and conventional 3D radiotherapy. For patients with multiple courses of radiotherapy, dose distributions of the prior and boost treatment plans were converted to BED. The fraction size specified by the prescription was applied globally for each BED calculation, α/β ratio of 10 and 2.5 was used for early and late effect, respectively. Image registration with CT or MR was performed for initial and boost plans. The registration information was applied to dose distributions to obtain the composite EQD2. As a demonstration of this method, two patients were selected who had combined treatments from substantially different modalities. A patient with liver cancer initially received radiotherapy of 30 Gy/10 Fx and re-irradiation with CyberKnife radiosurgery (15 Gy/1 Fx). The combined plan showed that the PTV received EQD2 of 63.8 Gy. Another patient had brain metastasis treated with GammaKnife of 18 Gy (50% isodose) followed by conventional 3D whole brain radiation of 30 Gy/10 Fx. The minimal combined tumor EQD2 was 74.5 Gy. Early and late calculated responses showed that all critical organ doses were within tolerance. For patients receiving radiation with different fractionation schemes, combined isoeffective dose distributions were calculated and displayed. In both cases, crucial information regarding 3-D dose distributions assisted the physicians in determining whether tolerance limits of overlap areas of retreated critical structures were preserved.

Improved Normal Tissue Sparing in Head and Neck Radiotherapy Using Biological Cost Function Based-IMRT

Intensity-modulated radiotherapy (IMRT) has reduced the impact of acute and late toxicities associated with head and neck radiotherapy. Treatment planning system (TPS) advances in biological cost function based optimization (BBO) and improved segmentation techniques have increased organ at risk (OAR) sparing compared to conventional dose-based optimization (DBO). A planning study was undertaken to compare OAR avoidance in DBO and BBO treatment planning. Simultaneous integrated boost treatment plans were produced for 10 head and neck patients using both planning systems. Plans were compared for tar get coverage and OAR avoidance. Comparisons were made using the BBO TPS Monte Carlo dose engine to eliminate differences due to inherent algorithms. Target coverage (V95%) was maintained for both solutions. BBO produced lower OAR doses, with statistically significant improvement to left (12.3%, p = 0.005) and right parotid mean dose (16.9%, p = 0.004), larynx V50 Gy (71.0%, p = 0.005), spinal cord (21.9%, p < 0.001) and brain stem dose maximums (31.5%, p = 0.002). This study observed improved OAR avoidance with BBO planning. Further investigations will be undertaken to review any clinical benefit of this improved planned dosimetry.

The potential benefit of swallowing sparing intensity modulated radiotherapy to reduce swallowing dysfunction: An in silico planning comparative study

PurposeTo apply recently developed predictive models for swallowing dysfunction to compare the predicted probabilities of swallowing dysfunction for standard intensity modulated radiotherapy (ST-IMRT) and swallowing sparing IMRT (SW-IMRT). Materials and methodsThirty head and neck cancer patients who previously underwent radiotherapy for the bilateral neck were selected for this study. For each patient, ST-IMRT and SW-IMRT simultaneous integrated boost treatment plans were created. ST-IMRT treatment plan optimisation aimed at obtaining adequate target volume coverage and sparing of the parotid and submandibular glands as much as possible. Objectives for SW-IMRT were similar, with additional objectives to spare the organs at risk related to swallowing dysfunction (SWOARs). Dose-volume data with ST-IMRT and SW-IMRT and normal tissue complication probabilities for physician-rated and patient-rated swallowing dysfunction were calculated with recently developed predictive models. ResultsAll plans had adequate target volume coverage and dose to critical organs was within accepted limits. Sparing of parotid glands was similar for ST-IMRT and SW-IMRT. With SW-IMRT, the mean dose to the various SWOARs was reduced. Absolute dose values and dose reductions with SW-IMRT differed per patient and per SWOAR and depended on N stage and tumour location. The mean reduction in predicted physician-rated Radiation Therapy Oncology Group (RTOG) grade 2–4 swallowing dysfunction was 9% (range, 3–20%). Mean reductions of the probability of patient-rated moderate to severe complaints with regard to the swallowing of solid food, soft food, liquid food and choking when swallowing were 8%, 2%, 1% and 1%, respectively. ConclusionsNew predictive models for swallowing dysfunction were applied to show potential reductions in physician and patient-rated swallowing dysfunction with IMRT that was specifically optimised to spare SWOARs.

Planning the breast boost: How accurately do surgical clips represent the CT seroma?

Background and purpose To measure the distance between surgical clips and edge of CT-defined seroma in a coronal plane in women who have undergone wide local excision of breast cancer and to evaluate dosimetric coverage of CT-defined boost volumes by conventional clip-based electron fields. Materials and methods Planning CT images of 30 lumpectomy cavities from 30 patients were reviewed. All seroma cavities had at least 4 clips and Cavity Visualization Score ⩾3. Distances between clips and seroma edge ( D c–s) were measured at the radial margins for each patient. Clips-based electron fields were generated by including all the clips with 2 cm margin in the coronal plane and three-dimensional conformal radiotherapy plans (3D-CRT) were devised based on CT tumor beds (CT-TBs). The parameters of dose–volume histogram between the two boost treatment plans were analyzed. Results The mean seroma edge extended beyond the clips by 0.3–0.5 cm. In all 120 D c–ss, 76.7% were ⩽0.5 cm, 8.3% were >1 cm and 15% were between 0.5 and 1 cm. Twenty patients (20/30) had D c–smax (The maximal D c–s of each patient) > 0.5 cm and 7 patients had D c–smax > 1 cm. With the electron fields, only 46.7% (14/30) had D 90 (The minimal dose received by 90% of the planning target volume (PTV)) > 90% and geographical miss (any portion of the PTV receiving <50% of the prescribed dose) was found in 36.7% (11/30). D c–smax > 0.5 cm was associated with D 90 < 90% ( P < 0.001) and >1 cm was associated with geographic miss ( P = 0.001). Conclusions Surgical clips are not always consistent with the edge of seroma. Electron boost field based on clips leads to insufficient dose coverage to the CT-TB. 3D-CRT planning should be considered to ameliorate the dose coverage to the tumor bed.

Customized Computed Tomography-Based Boost Volumes in Breast-Conserving Therapy: Use of Three-Dimensional Histologic Information for Clinical Target Volume Margins

To determine the difference in size between computed tomography (CT)-based irradiated boost volumes and simulator-based irradiated volumes in patients treated with breast-conserving therapy and to analyze whether the use of anisotropic three-dimensional clinical target volume (CTV) margins using the histologically determined free resection margins allows for a significant reduction of the CT-based boost volumes. The CT data from 49 patients were used to delineate a planning target volume (PTV) with isotropic CTV margins and to delineate a PTV(sim) that mimicked the PTV as delineated in the era of conventional simulation. For 17 patients, a PTV with anisotropic CTV margins was defined by applying customized three-dimensional CTV margins, according to the free excision margins in six directions. Boost treatment plans consisted of conformal portals for the CT-based PTVs and rectangular fields for the PTV(sim). The irradiated volume (volume receiving > or =95% of the prescribed dose [V(95)]) for the PTV with isotropic CTV margins was 1.6 times greater than that for the PTV(sim): 228 cm(3) vs. 147 cm(3) (p < .001). For the 17 patients with a PTV with anisotropic CTV margins, the V(95) was similar to the V(95) for the PTV(sim) (190 cm(3) vs. 162 cm(3); p = NS). The main determinant for the irradiated volume was the size of the excision cavity (p < .001), which was mainly related to the interval between surgery and the planning CT scan (p = .029). CT-based PTVs with isotropic margins for the CTV yield much greater irradiated volumes than fluoroscopically based PTVs. Applying individualized anisotropic CTV margins allowed for a significant reduction of the irradiated boost volume.

Dosimetric comparison of intensity-modulated, conformal, and four-field pelvic radiotherapy boost plans for gynecologic cancer: a retrospective planning study

PurposeTo evaluate intensity-modulated radiation therapy (IMRT) as an alternative to conformal radiotherapy (CRT) or 4-field box boost (4FB) in women with gynecologic malignancies who are unsuitable for brachytherapy for technical or medical reasons.MethodsDosimetric and toxicity information was analyzed for 12 patients with cervical (8), endometrial (2) or vaginal (2) cancer previously treated with external beam pelvic radiotherapy and a CRT boost. Optimized IMRT boost treatment plans were then developed for each of the 12 patients and compared to CRT and 4FB plans. The plans were compared in terms of dose conformality and critical normal tissue avoidance.ResultsThe median planning target volume (PTV) was 151 cm3 (range 58–512 cm3). The median overlap of the contoured rectum with the PTV was 15 (1–56) %, and 11 (4–35) % for the bladder. Two of the 12 patients, both with large PTVs and large overlap of the contoured rectum and PTV, developed grade 3 rectal bleeding. The dose conformity was significantly improved with IMRT over CRT and 4FB (p ≤ 0.001 for both). IMRT also yielded an overall improvement in the rectal and bladder dose-volume distributions relative to CRT and 4FB. The volume of rectum that received the highest doses (>66% of the prescription) was reduced by 22% (p < 0.001) with IMRT relative to 4FB, and the bladder volume was reduced by 19% (p < 0.001). This was at the expense of an increase in the volume of these organs receiving doses in the lowest range (<33%).ConclusionThese results indicate that IMRT can improve target coverage and reduce dose to critical structures in gynecologic patients receiving an external beam radiotherapy boost. This dosimetric advantage will be integrated with other patient and treatment-specific factors, particularly internal tumor movement during fractionated radiotherapy, in the context of a future image-guided radiation therapy study.

Importance of 3D conformal percutan and brachytherapy treatment planning based on CT and MRI examinations in treatment of oral cavity tumors

AIM: The importance of 3D conformal percutan and brachytherapy treatment planning based on CT and MRI examinations in treatment of oral cavity tumors. Introducing of the planning procedure and the selection aspects. METHOD: We present the treatment planning based on CT and MRI slices of an oral cavity tumor. The percutan or interstitial boost follow the percutan irradiation of the involved regions and lymph nodes, regarding to the target volume and the critical organs. RESULT: Our ADAC 3D planning system gives us the possibility to add the first line and the boost treatment plans, to determine and compare the dose distribution within the planned target volume and the radiation load of the critical organs. CONCLUSION: The comparative 3D radiation planning system allows higher local dose escalation required for the effective radiation treatment of oral cavity tumors with maximal protection of the surrounding healthy tissues.