Total Planning Target Volume Research Articles

Does transperitoneal minimally invasive radical prostatectomy increase the amount of small bowel receiving salvage radiation?

Transperitoneal minimally invasive radical prostatectomy (MIRP) has become first choice for several urologists and patients dealing with localized prostate cancer. We evaluate the effect of postoperative radiation on the small bowel in patients who underwent extraperitoneal open versus transperitoneal MIRP. We reviewed all patients who received postoperative radiation from 2006 to 2010. Planning target volume (PTV) and surrounding organs, including the small bowel, were delineated. The presence of the small bowel in PTV and its volume in receiving each dose level were analyzed. A total of 122 patients were included: 26 underwent MIRP and 96 underwent open prostatectomy. The median age of patients was 66 years, with median body mass index 27 kg/m(2). The total PTV dose was 66 Gy, with the minimum and maximum doses received by the small bowel 0.4 and 66.4 Gy, respectively. The maximum volume of small bowel that received the safe limit of 40 Gy was 569 cm(3). Of the 26 patients who underwent MIRP, 12 (46%) had small bowel identified inside the PTV compared to 57 (59%) among patients who underwent open prostatectomy (p = 0.228). The mean volume of the small bowel receiving 40 Gy was 26 and 67 cm(3) in open and MIRP groups, respectively (p = 0.006); the incidence of acute complications was the same in both groups. Higher volumes of the small bowel are subjected to significant radiation after MIRP procedures compared to open procedures; however, we could not demonstrate any impact on acute complications. Whether there is a difference in late complications remains to be evaluated.

The efficacy and limitations of stereotactic radiosurgery as a salvage treatment after failed whole brain radiotherapy for brain metastases

The aim of the present study was to evaluate the efficacy and limitations of repeat stereotactic radiosurgery (SRS) salvage for patients with recurrence of brain metastases (BM) after whole brain radiotherapy (WBRT). This is a retrospective, observational, single-center trial analyzing 77 consecutive patients with recurrent BM who were treated primarily with WBRT. All patients underwent SRS as salvage treatment. Median age was 62 years, and median Karnofsky performance status (KPS) was 80. The median interval between the starting date of WBRT and radiosurgery was 10.6 months. One, two and more than two SRS sessions were required in 42, 13 and 22 patients, respectively. The median total planning target volume (PTV) was 8.1 mL and the median dose prescribed was 20 Gy. The median follow-up was 7.7 months. 1- and 2-year neurological death-free survival (NS) rates were 87 and 78 %, respectively. Competing risk analysis demonstrated active extra-central nervous system (CNS) disease [Hazard ratio (HR) 0.236, P = 0.041] and total PTV on initial SRS (≥ 5 mL) (HR 4.22, P = 0.033) to be associated with the NS rate. 1- and 2-year overall survival (OS) rates were 41 and 11 %, respectively. The median OS time was 8.2 months. Active extra-CNS disease (HR 1.94, P = 0.034) and high KPS (≥ 90) (HR 0.409, P = 0.006) were associated with the OS rate. In total, 798 tumors (75 %) in 66 patients (86 %) with sufficient radiological follow-up data were evaluated. 1- and 2-year metastasis local control rates were 76.6 and 57.9 %, respectively. Prescribed dose (≥ 20 Gy) (HR 0.326, P < 0.001), tumor volume (≥ 2 mL) (HR 1.98, P = 0.007) and metastases from breast cancer (HR 0.435, P < 0.001) were independent predictive factors for local tumor control. Repeat salvage SRS for recurrent BM after WBRT appeared to be a safe and effective treatment. In the majority of patients, even those with numerous BM, neurological death could be delayed or even prevented.

Predictors of Weight Loss during Conformal Radiotherapy for Head and Neck Cancers – How Important are Planning Target Volumes?

AimsNutritional compromise is common during high dose radiotherapy (RT) or chemoradiotherapy (CRT) for head and neck cancers. We aimed to identify the factors that determine nutritional outcome for head and neck cancer patients during radiotherapy. MethodsData from 103 patients with head and neck cancer treated with highly conformal radiotherapy to doses of 60 Gy or more in 30–33 fractions in the adjuvant or definitive setting was analyzed. All patients received complex 3D conformal radiotherapy (3DCRT) or intensity modulated radiotherapy (IMRT). Patients received regular nutritional counseling and need-based interventions. Their weight was recorded at the beginning and end of radiotherapy. Using univariate and multivariate models we tested possible predictors of weight loss of >5% and NG tube requirement. ResultsThe mean weight loss was 3.8%. The incidence of weight loss >5% was 37.9% and NG tube placement was 24.3%. The factors significantly associated with >5% weight loss in the univariate analysis were tumor site (oro-hypopharyngeal vs. others), definitive vs. adjuvant RT; prescription dose of >60 Gy vs. 60 Gy; CRT vs. RT alone; prescription dose planning target volume (PTV) volume >235 cc and total PTV volume >615 cc. Age, sex, T stage, N stage and modality (3DCRT/IMRT) were not significant. In multivariate analysis, the total PTV volume, prescription dose PTV volume and use of chemotherapy were significant after controlling for other factors. Patients could be risk stratified based on the use of CRT and large PTV volumes. Patients with none, one or both factors had a likelihood of >5% weight loss of 0%, 30.3%, and 56.9% (p < 0.001) and likelihood of NG tube placement of 5.3%, 15.2% and 37.3% (p = 0.007). ConclusionsIt is possible to predict weight loss and NG tube requirements from disease and treatment related factors. PTV volumes are important predictors of nutritional compromise. Risk stratification may enable more focused counseling and identification of patients who require preventive interventions.

Evaluation of inter-fraction and intra-fraction errors during volumetric modulated arc therapy in nasopharyngeal carcinoma patients

BackgroundThis prospective study was conducted to evaluate inter- and intra-fraction errors in nasopharyngeal carcinoma (NPC) patients undergoing volumetric modulated arc therapy (VMAT) using cone-beam computed tomography (CBCT) and to thus obtain planning target volume (PTV) margins to effectively guide treatment in the future.MethodsFifteen NPC patients scheduled to undergo VMAT were prospectively enrolled in the study. For each patient, three CBCT scans were obtained; one after daily conventional positioning, one after online correction with 2 mm tolerance and one after 1 week of VMAT delivery. The scans were registered to the planning CT to determine the inter- and intra-fraction errors. Patient positioning errors were analyzed for time trends over the course of radiotherapy. PTV margins were calculated from the systematic (Σ) and random (σ) errors.ResultsThe average absolute values of the pre-correction, post-correction and intra-fraction errors (in order) were 1.1, 0.6 and 0.4 mm in the medial–lateral (ML) direction, 1.2, 0.7 and 0.5 mm in the superior–inferior (SI) direction and 1.1, 0.7 and 0.5 mm in the anterior–posterior (AP) direction. The corresponding Σ were 1.0–1.4 mm, 0.4–0.5 mm and 0.2–0.4 mm, while the corresponding σ were 0.7–0.8 mm, 0.6–0.7 mm and 0.5–0.6 mm. With time, gradual increases in both the inter- and intra-fraction three-dimensional displacements were observed (P = 0.019 and P = 0.044, respectively). The total PTV margins accounting for pre-correction and intra-fraction errors were 3.4–4.1 mm and those accounting for post-correction and intra-fraction errors were 1.7–2.2 mm.ConclusionsCBCT is an effective modality to evaluate and improve the accuracy of VMAT in NPC patients. Inter- and intra-fraction three-dimensional displacements increased as a function of time during the course of radiotherapy. In our institution, we recommend a PTV margin of 5 mm for NPC patients undergoing VMAT without CBCT and 3 mm for those treated with rigorous daily CBCT scans.

Impacts of HER2-overexpression and molecular targeting therapy on the efficacy of stereotactic radiosurgery for brain metastases from breast cancer

Advances in chemotherapy for breast cancer (BC) have prolonged overall survival, especially for patients with human epidermal growth factor receptor-2 (HER2) positive cancer. We evaluated the effectiveness and limitations of stereotactic radiosurgery (SRS) for brain metastases (BM) from BC in conjunction with molecular targeting chemotherapy. Outcomes were retrospectively reviewed in 80 consecutive patients who underwent gamma knife SRS for BM from BC between January 2009 and February 2012. The overall survival (OS), neurological death-free survival (NS) and local tumor control endpoints were calculated, and prognostic factors were investigated using proportional hazards models. In 40 patients with HER2-overexpression, treatment results were compared between two sub-groups: lapatinib-based therapy (24 patients) versus non-lapatinib-based therapy (16 patients). The rates of 1- and 2-year OS after SRS were 50 and 26 %, respectively. The median survival time (MST) was 11.4 months. HER2-overexpression (P < 0.001), recursive partitioning analysis class (P = 0.018) and total planning target volume on initial SRS (P = 0.004) were associated with OS. The MSTs in HER2-positive and -negative patients were 16.6 and 7.1 months, respectively (P = 0.001). The rates of 1- and 2-year NS were 90 and 78 %, respectively. The rates of 1- and 2-year local tumor control were 84 and 70 %, respectively. Factors associated with local tumor control included lesion volume (P < 0.001) and peripheral dose (P = 0.003). In sub-analysis of patients with HER2-overexpression, lapatinib-based chemotherapy was also associated with better local tumor control (P = 0.002). The 1-year local tumor control rate of the lapatinib group was significantly better than that of the non-lapatinib group (86 vs. 69 %, P < 0.001). SRS is a safe and effective management option for selected patients with BM from BC. Patients with HER2-overexpressing tumors were found to be a distinct subgroup for which a longer survival time can be expected. Synergistic anti-tumor effects of lapatinib on BM in conjunction with SRS were suggested.

Dosimetric effects of air pocket sizes in MammoSite treatment as accelerated partial breast irradiation for early breast cancer

MammoSite brachytherapy system has been used as one of the accelerated partial breast irradiation (APBI) techniques since 2002. The clinical results from several clinical institutions had shown comparable treatment efficacy, cosmesis, and toxicity to other APBI techniques. During MammoSite treatment, air cavities had been one of the primary issues causing treatment cancellation or delay. With the tolerance of the air volume less than 10% of the total Planning Target Volume (PTV) set, there is still no data available to show the actual dose delivered to the breast tissue with the existence of the air pocket. In this paper, Monte Carlo N‐Particle version 5 (MCNP5) was used to model a hypothesis MammoSite phantom with different sizes of air pockets, and compared to the calculation results from the treatment planning system (TPS) without heterogeneous corrections. It was found that without heterogeneous corrections, the difference between the TPS and MCNP5 calculations in the air cavity surface doses and PTV point doses can be up to 2.02% and 3.61%, respectively, using the balloon and air pocket size combinations calculated in this paper. Based on the distance from the point of interest to the balloon surface, an approximate dose can be calculated using the linear relationship found in this study. These equations provide a quick and simple way to predict the actual dose delivered to the breast soft tissue located within the PTV. With the equation applied to the dose from the TPS, the dose error caused by the air pocket during MammoSite treatment can be reduced to a minimum.PACS number: 87.53.Jw

Intensity-modulated radiotherapy with a belly board for rectal cancer

Intensity-modulated radiotherapy (IMRT) techniques can reduce the irradiated small bowel volume in rectal cancer patients, but combined use of IMRT and a belly board is yet to be reported on for rectal cancer patients. The aim of this study was to determine whether additional use of a belly board reduced the irradiated small bowel volume observed using IMRT alone in rectal cancer patients. Twenty patients scheduled to receive preoperative radiotherapy for rectal cancer underwent two series of CT scans, with and without a belly board. IMRT planning was performed using 6-MV photon beams and seven equispaced fields. The bladder, small bowel, and planning target volume (PTV) were analyzed for doses between 10% and 100% of the prescribed dose at 10% intervals. Data were analyzed using Wilcoxon signed rank tests. There were no significant differences between patients undergoing IMRT with a belly board and those without a belly board in terms of total small bowel volumes, bladder, and PTV (p=0.571, p=0.841, and p=0.870, respectively). Statistical analysis showed that the irradiated small bowel volume with a belly board was smaller than that without a belly board (p<0.05 at 20-100% dose levels), with the mean relative reduction in the irradiated small bowel volume being 37.8+/-32.8%. IMRT with a belly board is more effective than IMRT alone in reducing the irradiated small bowel volume. These findings suggest that the use of a belly board with IMRT may reduce small bowel complications in preoperative radiotherapy.

The dosimetric consequences of inter-fractional patient movement on conventional and intensity-modulated breast radiotherapy treatments

Background and purpose: A method has been developed to enable a comparison to be made between the effects of movement on conventional tangential breast treatments and intensity-modulated treatments delivered using compensators. Materials and methods: The effects of set-up error and organ motion were studied for a set of six patients. Images were taken of these patients over the course of their treatment and conventional wedged and compensated treatment plans were designed for each. Dose-volume statistics were used to evaluate each of the treatment plans by examining the volume outside the dose range 95–105%. To assess the effects of movement alone, the volume change from day 1 was also calculated. Results: Thirty-six estimated CT-sets were available for evaluation. Measurements of breast volume showed the volume to increase to a peak between fraction 4 and 8 and then decrease back below the initial volume. The standard treatment was found to yield 29/36 plans (81%) with greater than 5% volume outside the dose range 95–105%. For the compensated plans this dropped to 11/36 plans (31%). The analysis of the volume changes from day 1 showed that for both standard and compensated treatments 7/30 plans (23%) had an increase in volume outside the dose range 95–105% of greater than 5% of the total planning target volume. Conclusions: The compensated treatment is more susceptible to patient movement. However, the actual volume of tissue outside 95–105% dose is less when compared to standard treatment implying the compensated treatment is still superior.