RESUMEN
Objective To use helical tomotherapy ( HT ) for determining the difference between actual doses and planning doses to the target volume and organs at risk ( OARs ) in patients with nasopharyngeal carcinoma receiving radiotherapy, and to provide guidance for the clinical treatment. Methods Localization and delineation of the target volume and OARs were performed by computed tomography ( CT) in 21 patients with nasopharyngeal carcinoma receiving radical radiotherapy using HT. All patients underwent megavoltage CT ( MVCT) scan prior to treatment. The obtained MVCT images were used for dose reconstruction in the adaptive module of HT, in which the actual dose was obtained and the non?image?guided dose was simulated. Each single dose distribution and the corresponding CT image were sent to software MIM6. 0 for superimposition, and the overall dose was obtained. The initial plan, image?guided plan, and non?image?guided plan were named Plan?1, 2, and 3, respectively. The dose distribution in the target volume and OARs was compared between the three plans with t ? test or wilcoxon test . Results Compared with those in Plan?1, the D98 values for the planning gross tumor volume ( PGTV) and planning target volume ( PTV) in Plan?2 were significantly reduced by 1. 16% and 2. 3%, respectively ( P=0. 025;P=0. 043);the volumes of the left and right parotids in Plan?2 were significantly reduced by 46. 0% and 46. 5% on average, respectively ( P=0. 000);the distances between the midline and the center?of?mass for left and right parotids were significantly reduced by 6. 9% and 6. 5%, respectively ( P=0. 000);the V26 and Dmean for both parotid glands were significantly elevated by 32. 8% and 25. 2%, respectively ( P=0. 000) . Compared with those in Plan?1, the D98 values for PGTV, PTV?1, and PTV?2 in Plan?3 were significantly reduced by 2. 0%, 1. 9%, and 2. 4%, respectively ( P=0. 001;P=0. 007;P=0. 036);the V26 and Dmean for both parotid glands in Plan?3 were significantly elevated by 33. 6% and 25. 3%, respectively ( P=0. 000);Dmax to the spinal cord was significantly increased by 6. 9%( P=0. 005) . There was no significant difference in D2 to the spinal cord between Plan?2 and Plan?1( P=0. 392) . Conclusions The doses to both parotid glands increase during HT for nasopharyngeal carcinoma, which is closely associated with the shift of the parotid glands toward the midline. Image?guided radiotherapy does not enhance the dose to the target volume, but reduces the dose to the spinal cord.
RESUMEN
Objective To assess the safety and efficacy of preoperative intensity-modulated radiotherapy(IMRT) with oral capecitabine in patients with locally advanced mid-low rectal cancer using a simultaneous integrated boost (SIB) of tomotherapy.Methods Total 16 patients with resectable locally advanced mid-low rectal cancer (patients with T3 to T4 and/or N ± rectal cancer) were enroll in current study.Patients were received IMRT to 2 dose levels simultaneously (55 and 47.5 Gy in 25 fractions) with concurrent capecitabine 825 mg/m2 twice daily,5 days/week.Total mesorectal excision was performed at 8 to 9 week after the completion of chemoradiation.The primary end point included side effect,the rate of sphinctersparing,postoperative complication and pathological complete response rate (pCR) were observed.Side effects were scored using the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0.Results All patients were received chemoradiotion therapy without any break.Tomotherapy showed superiority with respect to target coverage,homogeneity and conformality.Two patients refused to perform radical surgery because of almost complete primary tumor regression and complete symptom relief after neoadjuvant therapy.Fourteen patients underwent surgical resection and 11 patients (78.6％) underwent sphincter-sparing lower anterior resection.Four patients(28.6％) had a pathological complete response.The incidence of grade 1-2 hematologic,gastro-intestinal toxicities were 62.5％ (10/16) and 18.8％ (3/16).The incidence of grade 3 skin toxicities were 68.8％(10/16).Grade Ⅳ side effect was not observed.Surgical complications (incisional infection on thirteen after surgery) were observed in 1 patient.Conclusion Preoperative simultaneous integrated boost of tomotherapy with concurrent oral capecitabine is safe and well tolerated in patients with a promising local control.However,a larger number of patients and a long follow-up are required to assess its potential superiority.
RESUMEN
Objective To analyze the impact of parotid's position and volume changing on radiation dose for head and neck cancer treated with TomoTherapy.Methods Totally 12 patients with head and neck cancer were treated with TomoTherapy.Before the treatment,the dose distribution was recalculated with MVCT images,which would obtain the parameters of position,volume and actual radiation dose for parotids.Results The volume of parotids in Plan2 was significantly lower than in Plan1,and the percentage reduction was 29.06％ and 31.78％ for left and right parotid,respectively (Z =6.77,3.06,P ＜ 0.05).Distance between the COM (center of mass) of parotids and the midline of body was significantly smaller in Plan2 than in Plan1,and the percentage reduction was 6.72％ and 6.19％ (t =5.14,5.80,P ＜ 0.05) at left and right side,respectively.Average dose and V26 for both parotids were higher than those in Plan1,increasing by an average of 37.74％,25.08％ (Z =-6.03,-5.31,P ＜ 0.05) for left parotid and 30.45％,19.33％ (Z =-5.43,-3.26,P ＜0.05) for right parotid,respectively.Conclusions The actual radiation dose to parotids was significantly increased during the radiation therapy for patients with head and neck cancer.There was a linear correlation between the decrease of distance between the COM of parotids and the midline of body and the percentage increase of parotids' radiation dose.No correlation between the reduction of parotids' volume and dose to parotids.In order to reduce the parotids' radiation dose,modification of treatment plan at the appropriate time is essential.
RESUMEN
Objective:To compare bone marrow-sparing intensity-modulated radiotherapy(BMS-IMRT)with conventional (four-field box[3DCRT]and anteroposterior-posteroanterior[CRT])techniques in the treatment of cervical cancer.Methods:For a cohort of 10 patients,BMS-IMRT,3DCRT and CRT planning were designed.The prescribed dose was 45Gy/1.8Gy/25f,95%of the planning target volume received this dose.Doses were computed with a commercially available TPS.Plans were compared according to dose-volume histogram (DVH)analysis in terms of PTV homogeneity and conformity indices(HI and CI)as well as OARs dose and volume parameters.Results:BMS-IMRT had an advantages over 3DCRT and CRT in terms of CI,but inferior to the latter two for HI.BMS-IMRT was superior to 3DCRT in reducing the dose to PBM,small bowel,bladder and rectum.Compared with CRT,BMS-IMRT reduced the volume irradiated to the doses from 30Gy to 40Gy,but increased the volume irradiated to the low doses from 5Gy to 20Gy.In addition,BMS-IMRT reduced the volume of small bowel,bladder,rectum at nearly all dose levels.Conclusion:BMS-IMRT reduced irradiation of PBM compared with 3DCRT technique.Compared with CRT technique,BMS-IMRT reduced the volume of PBM irradiated to high doses.Therefore,for patients with cervical cancer after hysterectomy,BMS-IMRT might reduce acute hematologic toxicity(HT)compared with conventional techniques.
RESUMEN
Objective: To compare inverse three-dimensional conformal radiotherapy (Inv 3D-CRT) and intensity modulated ra-diotherapy (IMRT) for non-small cell lung cancer. Methods: For a cohort of 10 patients, Inv 3D-CRT and three groups of IMRT plannings were designed for per patient. The prescribed dose was 60 Gy/2 Gy/30f, 95% of the planning target volume received this dose. Dose was computed with a commercially available TPS using convolution/superposition (CS) algorithm. Plans were compared according to the PTV_(95)V_(20) ratio (PTV_(95)V_(20)) and D_(max)-D_(min). Results: Compared with Inv 3D-CRT, the PTV_(95)V_(20) ratio of three groups of IMRT increased by 1.08 (P = 0.014), 0.72 (P = 0.089) and 0.42 (P = 0.318), respectively. Conclusions: For NSCLC, IMRT can reduce the dose to the lungs compared with inverse 3D-CRT by improving the conformity of the plan and is worth spreading in clinical work.
RESUMEN
Objective To compare bone marrow-sparing intensity-modulated radiotherapy (BMS-IMRT) with conventional intensity-modulated radiotherapy (IMRT) without considering pelvic bone marrow (PBM) as a planning constraint in the treatment of cervical cancer after hysterectomy. Methods BMS-IM-RT and IMRT planning were separately designed in a cohort of 10 patients with cervical cancer after hysterec-tomy. The prescribed dose was 95% planning target volume receiving 45 Gy/25 f. A commercially available TPS with convolution/superposition (CS) algorithm was used for dose calculation. Plans were compared ac-cording to dose-volume histogram (DVH) analysis in terms of PTV homogeneity (HI), conformity index (CI) as well as dose and volume parameters of organ at risks (OARs). Results BMS-IMRT was better than IMRT in terms of CI, but inferior to the latter for HI. When compared with IMRT, V_5, V_(10), V_(20), V_(30) and V_(40) of PBM in BMS-IMRT were reduced by 1.81% ,8.61% ,31.81% ,29.50% and 28.29%, respec-tively. No statistically significant differences were found between BMS-IMRT and IMRT for dose distritutions of the small bowel, bladder or rectum. Conclusions For patients with cervical cancer after hysterectomy, BMS-IMRT can reduce the PBM volume irradiated by low dose, which may reduce acute hematologic toxici-ties.
RESUMEN
Objective To study the effect of the location and volume of tumors on the normal lung dose-volume parameters for lung cancer. Methods An sphere with a diameter of 2 cm made of tissue-equiv-alent material used for simulating tumor was inserted into the superior lobe, middle lobe, inferior lobe of the right lung, and superior lobe, inferior lobe of the left lung of the Rando phantom, respectively. 5-field sIM-RT plans were designed. The prescribed dose was 60 Gy/2 Gy/30 f, and 99% of the planning target volume received this dose. Dose-volume parameters of normal lung tissue including V_5, V_(10), V_(20), V_(30), V_50 and mean lung dose were analyzed and compared. Results For the dose-volume parameters, the diameter and the po-sition of the tumor have a significant effect (P < 0.05). With the diameter expanding from 2 cm to 3 cm,the parameters associated with tumor in various lobes increased by a range between 3.83%-125.38%,while the parameters linked with tumor in different lobes increased by a range between 10.46%-51.46% with the diameter expanding from 3 cm to 4 cm. Conclusions Location and diameter of sphere-like tumor have obvious effect on dose-volume parameters. Knowing about the degree of influence will help oncologists and physicists to evaluate treatment planning better and reduce radiation pneumonitis.