Clinical Study of the Necessity of Replanning Before the 25th Fraction During the Course of Intensity-Modulated Radiotherapy for Patients With Nasopharyngeal Carcinoma

Department of Radiation Oncology, Taizhou Hospital, Wenzhou Medical College, Taizhou, Zhejiang, China.
International journal of radiation oncology, biology, physics (Impact Factor: 4.26). 02/2010; 77(2):617-21. DOI: 10.1016/j.ijrobp.2009.08.036
Source: PubMed

ABSTRACT To quantify the target and normal structures on dose distributing variations during intensity-modulated radiotherapy (IMRT) and to assess the value of replanning for nasopharyngeal carcinoma (NPC) patients.
Twenty-eight NPC patients treated with IMRT were recruited. The IMRT was delivered in 33 fractions, to 70 to 76Gy, to the gross tumor volume (GTV). Before the 25th fraction of IMRT, a new simulation computed tomography (CT) scan was acquired for all patients. According to the dose constraint criterion in the Radiation Therapy Oncology Group (RTOG) 0225 protocol, the replanning was generated on the new simulation CT. With the Quality Assessment Center of a CORVUS 6.3 treatment planning system, a phantom plan was generated for each patient by applying the beam configurations of the initial plan to the anatomy of the new simulation CT. The dose-volume histograms of the phantom plan were compared with the replanning.
The percentage of prescription dose delivered to the clinical target volume (CTV1) was significantly increased by 4.91% +/- 10.89%, whereas the maximum dose to the spinal cord, mean dose to the left parotid, and V30 to the right parotid were significantly decreased by 5.00 +/- 9.23Gy, 4.23 +/- 10.03Gy, and 11.47% +/- 18.89% respectively in the replanning, compared with the phantom plan (p < 0.05). Based on the dose constraint criterion in the RTOG0225 protocol, 50% of phantom plans (14/28) were out of limit for the dose to the normal critical structures, whereas no plan was out of limit in replanning (p < 0.001).
Replanning for patients with NPC before the 25th fraction during IMRT helps to ensure adequate dose to the target volumes and safe doses to critical normal structures.

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Available from: Wei Wang, Aug 17, 2015
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    • "However, the increased conformity of IMPT may come at the cost of higher sensitivity to treatment uncertainties, as accurately positioning the Bragg peak is dependent on the accuracy of the computed tomography (CT) derived 3D stopping power map of the patient. The significant volumetric changes observed during fractionated radiation therapy of H & N cancer (Barker et al 2004) alongside positioning uncertainties have led investigators to recommend repeated CT scanning for dose recalculation during IMRT (Wang et al 2010) and more recently for IMPT (Kraan et al 2013). This entails a heavier workload at the CT scanner, additional appointments for the patient and may not capture patient positioning differences between the CT and treatment couches. "
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    ABSTRACT: The ability to perform dose recalculation on the anatomy of the day is important in the context of adaptive proton therapy. The objective of this study was to investigate the use of deformable image registration (DIR) and cone beam CT (CBCT) imaging to generate the daily stopping power distribution of the patient. We investigated the deformation of the planning CT scan (pCT) onto daily CBCT images to generate a virtual CT (vCT) using a deformable phantom designed for the head and neck (H & N) region.
    Physics in Medicine and Biology 12/2014; 60(2):595-613. DOI:10.1088/0031-9155/60/2/595 · 2.76 Impact Factor
    • "It also showed increase in dose to normal structure. There are few studies on repeat scan and replanning in IMRT,[2678] and till date there is no criteria for repeat scan and replanning during radiotherapy. "
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    ABSTRACT: Anatomical changes can occur during course of head-and-neck (H and N) radiotherapy like tumor shrinkage, decreased edema and/or weight loss. This can lead to discrepancies in planned and delivered dose increasing the dose to organs at risk. A study was conducted to determine the volumetric and dosimetric changes with the help of repeat computed tomography (CT) and replanning for selected H and N cancer patients treated with IMRT plans to see for these effects. In 15 patients with primary H and N cancer, a repeat CT scan after 3(rd) week of radiotherapy was done when it was clinically indicated and then two plans were generated on repeat CT scan, actual plan (AP) planned on repeat CT scan, and hybrid plan (HP), which was generated by applying the first intensity-modulated radiation therapy (IMRT) plan (including monitoring units) to the images of second CT scan. Both plans (AP and HP) on repeat CT scan were compared for volumetric and dosimetric parameter. The mean variation in volumes between CT and repeat CT were 44.32 cc, 82.2 cc, and 149.83 cc for gross tumor volume (GTV), clinical target volumes (CTV), and planning target volume (PTV), respectively. Mean conformity index and homogeneity index was 0.68 and 1.07, respectively for AP and 0.5 and 1.16, respectively for HP. Mean D95 and D99 of PTV was 97.92% (standard deviation, SD 2.32) and 93.4% (SD 3.75), respectively for AP and 92.8% (SD 3.83) and 82.8% (SD 8.0), respectively for HP. Increase in mean doses to right parotid, left parotid, spine, and brainstem were 5.56 Gy (Dmean), 3.28 Gy (Dmean), 1.25 Gy (Dmax), and 3.88 Gy (Dmax), respectively in HP compared to AP. Repeat CT and replanning reduces the chance of discrepancies in delivered dose due to volume changes and also improves coverage to target volume and further reduces dose to organ at risk.
    Journal of Medical Physics 07/2014; 39(3):164-8. DOI:10.4103/0971-6203.139005
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    • "It has been recognized that most patients with head and neck cancers receiving radiotherapy experience changes in anatomical structures mainly due to shrinkage of primary tumors, metastatic nodal masses, and body contour caused by profound body weight loss [7,11-14]. In the present study, we assessed the relationship between CTV reduction and original GTV or pre-treatment BMI and found a positive correlation between CTV reduction and BMI. "
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    ABSTRACT: Replanning in intensity-modulated radiotherapy (IMRT) has been reported to improve quality of life and loco-regional control in patients with nasopharyngeal cancer (NPC). Determination of the criteria for replanning is, however, urgently needed. We conducted a prospective study to determine when and for what type of patients is replanning preferred through weekly repeat computed tomography (CT) imaging during the course of IMRT. We recruited 20 patients who were diagnosed as having loco-regionally advanced, non-metastatic stage III or IVa NPC and treated with concurrent platinum-based chemoradiotherapy (CRT) using IMRT. Patients received CT simulation (sim-CT) and plain magnetic resonance imaging (MRI) plus diffusion-weighted imaging (DWI) weekly for five consecutive weeks. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated and recorded weekly based on the CT-CT fusion. The relationship between GTV/CTV reduction and clinical characteristics of the patients were assessed using Pearson correlation test. GTV and CTV decreased during the treatment by 36.03 mL (range, 10.91--98.82 mL) and 76.79 mL (range, 33.94--125.14 mL), respectively, after 25 fractions of treatment. The percentage reductions from their initial volume were 38.4% (range, 25.3--50.7%) and 11.8% (range, 6.7--18.3%), respectively. The greatest reductions in GTV and CTV were observed at the fourth week (i.e., upon completion of 20 fractions), compared to pre-treatment sim-CT. Weight loss and CTV reduction were significantly correlated with pre-treatment body mass index (BMI ) (r = 0.58, P = 0.012, and r = 0.48, P = 0.046, respectively). However, no significant correlation was observed between CTV reduction and initial tumor volume. In addition, GTV reduction was not significantly correlated with pre-treatment tumor volume (P = 0.65), but negatively correlated with pre-treatment tumor apparent diffusion coefficient (ADC) values (r = -0.46, P = 0.042). Our results indicate that the most appropriate replanning time is after 20 fractions of treatment, and pre-treatment BMI and ADC are potential predictive factors for the determination of replanning during IMRT.
    BMC Cancer 11/2013; 13(1):548. DOI:10.1186/1471-2407-13-548 · 3.36 Impact Factor
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