乳腺癌保乳术后调强放疗与常规放疗的剂量学比较

 目的　探讨早期乳腺癌保乳术后全乳适形调强放射治疗（IMRT）的剂量学优势。方法　选择10例接受保乳手术的Tis~2N0M0早期乳腺癌病例,其中左侧乳腺癌6例,右侧乳腺癌4例,应用三维治疗计划系统（3D-TPS）为每位患者设计两种全乳放射治疗计划,即切线野常规计划与IMRT计划,处方剂量均为50 Gy／25次。用剂量体积直方图（DVH）来比较两种计划中计划靶体积（PTV）、危及器官（OARS）的剂量学差异。结果　靶区覆盖率在两种计划中相似,分别为97.83 %、97.61 %,与常规计划相比IMRT计划的PTV接受＜95 %处方剂量与＞103 %处方剂量的体积百分比之和（IHI） 从25.42 %减少到2.71 %,PTV接受至少105 %处方剂量照射的体积百分比（V105 %）从25.79 %减少到1.08 %,IMRT计划改善IHI和减少V105 %的平均值,在PTV较大的患者中更明显。左侧乳腺癌患者心脏的平均剂量（Dmean）从6.72 Gy减少到4.95 Gy、心脏接受30 Gy照射的体积百分比（V30）从7.23 %减少到1.04 %。所有患者同侧肺的Dmean从9.19 Gy减少到7.65 Gy、至少接受20 Gy 照射的体积百分比（V20）从22.34 %减少到20.18 %。对侧乳腺Dmean从5.12 Gy减少到3.52 Gy,对侧肺Dmean从2.76 Gy减少到1.79 Gy。右侧患者肝脏Dmean从7.23 Gy减少到1.04 Gy。结论　全乳IMRT的剂量学优势主要是在保证靶区覆盖率的前提下,显著改善了靶区剂量分布的均匀性,并在一定程度上降低OARS的受照剂量与容积,乳房体积大的病例可以通过IMRT获得更好的剂量学结果。     

Comparison of three concomitant boost techniques for early-stage breast cancer

PURPOSE: Whole breast radiotherapy (RT) followed by a tumor bed boost typically spans 5-6 weeks of treatment. Interest is growing in RT regimens, such as concomitant boost, that decrease overall treatment time, lessening the time/cost burden to patients and facilities. METHODS AND MATERIALS: Computed tomography (CT) scans from 20 cases were selected for this retrospective, dosimetric study to compare three different techniques of concomitant boost delivery: (1) standard tangents plus an electron boost, (2) intensity-modulated RT (IMRT) tangents using custom compensators plus an electron boost, and (3) IMRT tangents plus a conformal photon boost. The equivalent uniform dose model was used to compare the plans. RESULTS: The average breast equivalent uniform dose value for the three techniques (standard, IMRT plus electrons, and IMRT plus photons) was 48.6, 47.9, and 48.3, respectively. The plans using IMRT more closely approximated the prescribed dose of 46 Gy to the whole breast. The breast volume receiving >110% of the dose was less with the IMRT tangents than with standard RT (p = 0.037), but no significant difference in the maximal dose or other evaluated parameters was noted. CONCLUSION: Although the IMRT techniques delivered the prescribed dose with better dose uniformity, the small improvement seen did not support a goal of improved resource use.     

早期乳腺癌保乳术后全乳调强放射治疗与常规切线野放疗的剂量学比较

目的探讨早期乳腺癌保乳术后全乳调强放射治疗(intensity-modulated radiotherapy,IMRT)的剂量学优势。方法选择6例接受保乳手术的T1N0M0早期乳腺癌病例,其中左侧乳腺癌4例,右侧乳腺癌2例,应用三维调强治疗计划系统为每例患者设计常规切线野与IMRT2种全乳放射治疗计划,处方剂量均为50Gy/25次。用剂量体积直方图(dose volume histograms,DVH)来比较2种计划中计划靶体积(planning target volume,PTV)、危及器官(organs at risks,OARs)的剂量学差异。结果在2种计划中,95%PTV均接受50Gy,99%PTV均接受95%的处方剂量;但在IMRT计划组V110%(接受大于110%处方剂量体积占PTV的百分比)下降了9.1%(46.3%比37.2%,P<0.05);同侧肺的V20(至少接受20Gy照射的肺体积占同侧肺体积的百分比)下降了7.2%(26.8%比18.0%,P<0.05);同侧肺的V30下降了12.0%(23.2%比11.2%,P<0.05);4例左侧乳腺癌患者的心脏V30下降了3.8%(7.0%比3.2%,P<0.05)。结论全乳IMRT在保证靶区覆盖率的前提下,改善了靶区内剂量的均匀性,降低了危及器官的受照剂量及缩小了危及器官的照射体积,尤其是同侧肺、心脏的照射体积,降低放射性肺炎及心血管事件发生的可能。     

Hybrid IMRT plans--concurrently treating conventional and IMRT beams for improved breast irradiation and reduced planning time

PURPOSE: To evaluate a hybrid intensity modulated radiation therapy (IMRT) technique as a class solution for treatment of the intact breast. METHODS AND MATERIALS: The following five plan techniques were compared for 10 breast patients using dose-volume histogram analysis: conventional wedged-field tangents (Tangents), forward-planned field-within-a-field tangents (FIF), IMRT-only tangents (IMRT tangents), conventional open plus IMRT tangents (4-field hybrid), and conventional open plus IMRT tangents with 2 anterior oblique IMRT beams (6-field hybrid). RESULTS: The 4-field hybrid and FIF achieved dose distributions better than Tangents and IMRT tangents. The volume of tissue outside the planning target volume receiving > or =110% of prescribed dose was largest for IMRT tangents (average 158 cc) and least for 6-field hybrid (average 1 cc); the FIF and 4-field hybrid were comparable (average 15 cc). Heart volume > or =30 Gy averaged 13 cc for all techniques, except Tangents, for which it was 32 cc. Average total lung volume > or =20 Gy was 7% for all. Contralateral breast doses were < 3% for all. Planning time for hybrid techniques was significantly less than for conventional FIF technique. CONCLUSIONS: The 4-field hybrid technique is a viable class solution. The 6-field hybrid technique creates the most conformal dose distribution at the expense of more normal tissue receiving low dose.     

An improved breast irradiation technique using three-dimensional geometrical information and intensity modulation.

BACKGROUND AND PURPOSE: In spite of the complex geometry of the breast, treatment planning for tangential breast irradiation is conventionally performed using two-dimensional patient anatomy information. The purpose of this work was to develop a new technique which takes the three-dimensional (3D) patient geometry into account. MATERIALS AND METHODS: An intensity-modulated radiotherapy (IMRT) technique was developed based on the division of the tangential fields in four multi-leaf collimator (MLC) shaped segments. The shape of these segments was obtained from an equivalent path length map of the irradiated volume. Approximately 88% of the dose was delivered by two open fields covering the whole treated volume. Dose calculations for the IMRT technique and the conventional technique were performed for five patients, using computer tomography (CT) data and a 3D calculation algorithm. A planning target volume (PTV) and ipsilateral lung volume were delineated in these CT data. RESULTS: All patients showed similar equivalent path length patterns. Analysis of the dose distribution showed an improved dose distribution using the IMRT technique. The dose inhomogeneity in the PTV was 9.0% (range 6.4-11.4%) for the conventional and 7.6% (range 6.5-10.3%) for the IMRT technique. The mean lung dose was reduced for the IMRT technique by approximately 10% compared with the conventional technique. CONCLUSION: A new breast irradiation technique has been developed which improves the dose homogeneity within the planning target volume and reduces the dose to the lung. Furthermore, the IMRT technique creates the possibility to improve the field matching in case of multiple field irradiations of the breast and lymph nodes.     

Combined photon and electron three-dimensional conformal versus intensity-modulated radiotherapy with integrated boost for adjuvant treatment of malignant pleural mesothelioma after pleuropneumonectomy

PURPOSE: The optimal technique for postoperative radiotherapy (RT) after extrapleural pleuropneumonectomy (EPP) of malignant pleural mesothelioma (MPM) remains debated. METHODS AND MATERIALS: The data from 8 right-sided and 9 left-sided consecutive cases of MPM treated with RT after radical EPP were reviewed. Of the 17 patients, 8 had been treated with three-dimensional (3D) conformal RT (3D-CRT) and 9 with intensity-modulated RT (IMRT) with 6-MV photons. The clinical outcome and adverse events were assessed. For comparative planning, each case was replanned with 3D-CRT using photons and electrons or with IMRT. Homogeneity, doses to the organs at risk, and target volume coverage were analyzed. RESULTS: Both techniques yielded acceptable plans. The dose coverage and homogeneity of IMRT increased by 7.7% for the first planning target volume and 9.7% for the second planning target volume, ensuring >or=95% of the prescribed dose compared with 3D-CRT (p < 0.01). Compared with 3D-CRT, IMRT increased the dose to the contralateral lung, with an increase in the mean lung dose of 7.8 Gy and an increase in the volume receiving 13 Gy and 20 Gy by 20.5% and 7.2%, respectively (p < 0.01). A negligible dose increase to the contralateral kidney and liver was observed. No differences were seen for the spinal cord and ipsilateral kidney. Two adverse events of clinical relevant lung toxicity were observed with IMRT. CONCLUSION: Intensity-modulated RT and 3D-CRT are both suitable for adjuvant RT. IMRT improves the planning target volume coverage but delivered greater doses to the organs at risk. Rigid dose constraints for the lung should be respected.     

Breast-conserving radiation therapy using combined electron and intensity-modulated radiotherapy technique.

BACKGROUND AND PURPOSE: To explore the feasibility of a multi-modality breast-conserving radiation therapy treatment technique to reduce high dose to the ipsilateral lung and the heart when compared with the conventional treatment technique using two tangential fields. MATERIALS AND METHODS: An electron beam with appropriate energy was combined with four intensity modulated photon beams. The direction of the electron beam was chosen to be tilted 10-20 degrees laterally from the anteroposterior direction. Two of the intensity-modulated photon beams had the same gantry angles as the conventional tangential fields, whereas the other two beams were rotated 15-25 degrees toward the anteroposterior directions from the first two photon beams. An iterative algorithm was developed which optimizes the weight of the electron beam as well as the fluence profiles of the photon beams for a given patient. Two breast cancer patients with early-stage breast tumors were planned with the new technique and the results were compared with those from 3D planning using tangential fields as well as 9-field intensity-modulated radiotherapy (IMRT) techniques. RESULTS: The combined electron and IMRT plans showed better dose conformity to the target with significantly reduced dose to the ipsilateral lung and, in the case of the left-breast patient, reduced dose to the heart, than the tangential field plans. In both the right-sided and left-sided breast plans, the dose to other normal structures was similar to that from conventional plans and was much smaller than that from the 9-field IMRT plans. The optimized electron beam provided between 70 to 80% of the prescribed dose at the depth of maximum dose of the electron beam. CONCLUSIONS: The combined electron and IMRT technique showed improvement over the conventional treatment technique using tangential fields with reduced dose to the ipsilateral lung and the heart. The customized beam directions of the four IMRT fields also kept the dose to other critical structures to a minimum.     

乳腺癌调强放射治疗和常规切线野治疗的三维剂量学研究

背景与目的:乳房保留治疗已在早期乳腺癌患者中逐渐推广应用,其中全乳根治性放疗的标准技术通常采用常规切线野技术。调强放射治疗(intensity-modulatedradiotherapy,IMRT)技术有望在保障相同疗效的同时进一步减少放疗并发症,提高生活质量。本研究利用三维计划系统评价全乳IMRT的剂量学优势与适应证。方法:选择10例接受保乳手术的Tis～2N0M0早期乳腺癌病例,利用三维治疗计划系统为每例患者设计两种全乳放射治疗计划,切线野常规计划与IMRT计划,处方剂量均为5000cGy。用剂量体积直方图(dosevolumehistograms,DVH)来比较各种计划中计划靶体积(planningtargetvolume,PTV)、危及器官(organsatrisks,OARs)的剂量学差异。结果:靶区覆盖率在两种计划中相似,分别为98.3%和97.7%。与常规计划比较,IMRT计划的PTV接受<95%处方剂量与>103%处方剂量的体积百分比之和(inhomogeneityindex,IHI)从29.9%减少到2.9%,PTV接受至少105%处方剂量照射的体积百分比(V105%)从28.2%减少到0.6%;IMRT计划改善IHI和减少V105%的平均值在PTV较大的患者中优势更明显。左侧患者中冠状动脉的最大剂量(Dmax)以及心脏的平均剂量(Dmean)分别从5057.1cGy减少到4832.9cGy和从629.8cGy到450.7cGy;右侧患者肝脏的Dmean从283.9cGy减少到172.0cGy;所有患者中同侧肺的Dmean、至少接受20Gy照射的体积百分比(V20)分别从925.2cGy减少到765.9cGy,从16.0%到15.3%,Dmean与V20的平均值在IMRT计划中减少的百分比在不同射野中心肺厚度(centrallungdistance,CLD)亚组中分别是14.7%与20.9%,7.0%与12.9%;对侧乳腺和对侧肺的Dmean也分别从75.4cGy减少到20.3cGy和从30.9cGy到16.1cGy。结论:全乳IMRT的剂量学优势主要在于保证靶区覆盖率的前提下,显著改善靶区的剂量分布均匀性并一定程度上降低OARs的受照剂量与容积。乳房体积和CLD较大的病例可以通过IMRT技术获得更好的剂量学结果。     

霍奇金淋巴瘤斗篷野常规放疗与调强放疗计划剂量学研究

目的 对Ⅰ、Ⅱ期霍奇金淋巴瘤斗篷野常规放疗和4种不同设野IMRT计划剂量学进行比较,评估不同照射方法的优缺点.方法 选择10例病理证实的Ⅰ、Ⅱ期淋巴瘤患者行CT定位,用ECLIPS治疗计划系统对每例患者分别作出常规和4种不同布野的IMRT计划,分析各治疗计划PTV的CI、HI、D95、V95、Dmax、Dmean、Dmin,肺V5、V10、V20、V30,脊髓最大受量Dmax.结果 IMRT在PTV靶区剂量、适形性和均匀性方面均优于常规计划.4种IMRT计划之间PTV靶区覆盖、靶区剂量、适形性和均匀性方面相近;肺V30均低于常规放疗,但肺低剂量受照体积较常规放疗高,IMRT子野数越多可能使肺V20、V30越小而V5、V10越大;脊髓Dmax均低于常规放疗计划.结论 IMRT在靶区适形度、均匀性和靶区剂量、保护脊髓、降低肺高剂量受照体积方面均优于常规放疗,但肺低剂量照射体积大于常规放疗,而斗篷野IMRT可考虑选用7个野IMRT计划.     

Intensity-modulated radiotherapy for lymphoma involving the mediastinum

PURPOSE: To determine the feasibility, potential advantage, and indications for intensity-modulated radiotherapy (IMRT) in the treatment of Hodgkin's lymphoma or non-Hodgkin's lymphoma involving excessively large mediastinal disease volumes or requiring repeat RT. METHODS AND MATERIALS: Sixteen patients with Hodgkin's lymphoma (n = 11) or non-Hodgkin's lymphoma (n = 5) undergoing primary radiotherapy or repeat RT delivered via an IMRT plan were studied. The indications for using an IMRT plan were previous mediastinal RT (n = 5) or extremely large mediastinal treatment volumes (n = 11). For each patient, IMRT, conventional parallel-opposed (AP-PA), and three-dimensional conformal (3D-CRT) plans were designed using 6-MV X-rays to deliver doses ranging from 18 to 45 Gy (median, 36 Gy). The plans were compared with regard to dose-volume parameters. The IMRT/AP-PA and IMRT/3D-CRT ratios were calculated for each parameter. RESULTS: For all patients, the mean lung dose was reduced using IMRT, on average, by 12% compared with AP-PA and 14% compared with 3D-CRT. The planning target volume coverage was also improved using IMRT compared with AP-PA but was not different from the planning target volume coverage obtained with 3D-CRT. CONCLUSION: In selected patients with Hodgkin's lymphoma and non-Hodgkin's lymphoma involving the mediastinum, IMRT provides improved planning target volume coverage and reduces pulmonary toxicity parameters. It is feasible for RT of large treatment volumes and allows repeat RT of relapsed disease without exceeding cord tolerance. Additional follow-up is necessary to determine whether improvements in dose delivery affect long-term morbidity and disease control.     

Treatment planning comparison of conventional, 3D conformal, and intensity-modulated photon (IMRT) and proton therapy for paranasal sinus carcinoma

PURPOSE: To determine the potential improvements in patients with paranasal sinus carcinoma by comparing proton and intensity-modulated radiotherapy (IMRT) with conventional and conformal photon treatment planning techniques. METHODS AND MATERIALS: In 5 patients, comparative treatment planning was performed by comparing proton plans and related conventional, conformal, and IMRT photon plans. The evaluations analyzed dose-volume histogram findings of the target volumes and organs at risk (OARs, i.e., pituitary gland, optical pathway structures, brain, nontarget tissue). RESULTS: The mean and maximal doses, dose inhomogeneities, and conformity indexes for the planning target volumes were comparable for all techniques. Photon plans resulted in greater volumes of irradiated nontarget tissues at the 10-70% dose level compared with the corresponding proton plans. The volumes thereby increased by a factor of 1.3-3.1 for conventional, 1.1-3.8 for conformal, and 1.1-3.7 for IMRT. Compared with conventional techniques, conformal and IMRT photon treatment planning options similarly reduced the mean dose to the OARs. The use of protons further reduced the mean dose to the OARs by up to 65% and 62% compared with the conformal and IMRT technique, respectively. CONCLUSION: Compared with conventional treatment techniques, conformal RT and IMRT similarly enabled dose reductions to the OARs. Additional improvements were obtained using proton-based treatment planning modalities.     

乳腺癌保乳术后常规、三维适形及两种调强放疗技术剂量学评估(英文)

Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.     

Does inverse‐planned intensity‐modulated radiation therapy have a role in the treatment of patients with left‐sided breast cancer?

Introduction: The purpose of the study was to determine if multi‐field inverse‐planned intensity‐modulated radiation therapy (IMRT) improves on the sparing of organs at risk (heart, lungs and contralateral breast) when compared with field‐in‐field forward‐planned RT (FiF). Methods: The planning CT scans of 10 women with left‐sided breast cancer previously treated with whole‐breast RT on an inclined breast board with both arms supported above the head were retrieved. The whole breast planning target volume (PTV) was defined by clinical mark‐up and contoured on all relevant CT slices as were the organs at risk. For each patient, three plans were generated using FiF, five‐ and nine‐field inverse‐planned IMRT, all to a total dose of 50 Gy to the whole breast. Mean and maximum doses to the organs at risk and the homogeneity index (HI) of the whole‐breast PTV were compared. Results: The mean heart dose for the FiF plans was 2.63 Gy compared with 4.04 Gy for the five‐field and 4.30 Gy for the nine‐field IMRT plans, with no significant differences in the HI of the whole‐breast PTV in all plans. The FiF plans resulted in a mean contralateral breast dose of 0.58 Gy compared with 0.70 and 2.08 Gy for the five‐ and nine‐field IMRT plans, respectively. Conclusions: FiF resulted in a lower mean heart and contralateral breast dose with comparable HI of the whole‐breast PTV in comparison with inverse‐planned IMRT using five or nine fields.     

Intensity-modulated radiotherapy in patients with locally advanced rectal cancer reduces volume of bowel treated to high dose levels

PURPOSE: To investigate the potential for intensity-modulated radiotherapy (IMRT) to spare the bowel in rectal tumors. METHODS AND MATERIALS: The targets (pelvic nodal and rectal volumes), bowel, and bladder were outlined in 5 patients. All had conventional, three-dimensional conformal RT and forward-planned multisegment three-field IMRT plans compared with inverse-planned simultaneous integrated boost nine-field equally spaced IMRT plans. Equally spaced seven-field and five-field and five-field, customized, segmented IMRT plans were also evaluated. RESULTS: Ninety-five percent of the prescribed dose covered at least 95% of both planning target volumes using all but the conventional plan (mean primary and pelvic planning target volume receiving 95% of the prescribed dose was 32.8 +/- 13.7 Gy and 23.7 +/- 4.87 Gy, respectively), reflecting a significant lack of coverage. The three-field forward planned IMRT plans reduced the volume of bowel irradiated to 45 Gy and 50 Gy by 26% +/- 16% and 42% +/- 27% compared with three-dimensional conformal RT. Additional reductions to 69 +/- 51 cm(3) to 45 Gy and 20 +/- 21 cm(3) to 50 Gy were obtained with the nine-field equally spaced IMRT plans-64% +/- 11% and 64% +/- 20% reductions compared with three-dimensional conformal RT. Reducing the number of beams and customizing the angles for the five-field equally spaced IMRT plan did not significantly reduce bowel sparing. CONCLUSION: The bowel volume irradiated to 45 Gy and 50 Gy was significantly reduced with IMRT, which could potentially lead to less bowel toxicity. Reducing the number of beams did not reduce bowel sparing and the five-field customized segmented IMRT plan is a reasonable technique to be tested in clinical trials.     

Is multibeam IMRT better than standard treatment for patients with left-sided breast cancer?

PURPOSE: When treatment intent is to include breast and internal mammary lymph nodes (IMNs) in the clinical target volume (CTV), a significant volume of the heart may receive radiation, which may result in late morbidity. The value of conformal intensity-modulated radiation therapy (IMRT) to avoid heart dose was studied. METHODS AND MATERIALS: Breast, IMNs, and normal tissues were contoured for 30 consecutive patients previously treated with RT after lumpectomy for left-sided breast cancer. Eleven-beam, conformal, inverse-planned IMRT plans were developed and compared with best standard plans. Conformity Index (CI), Homogeneity Index (HI), and doses to normal tissues were compared. RESULTS: Intensity-modulated RT significantly improved (two-sided paired t test) HI (0.95 vs. 0.74), CI (0.91 vs. 0.48), volume of the heart receiving more than 30 Gy (V30-heart) (1.7% vs. 12.5%), and volume of lung receiving more than 20-Gy (V20-left lung) (17.1% vs. 26.6%), all p < 0.001. The mean Healthy Tissue Volume (HTV = CT set - PTV) dose was similar between IMRT and best standard plans (6.0 and 6.9 Gy, respectively), but IMRT increased the volume of normal tissues receiving low-dose RT: V5-right lung (13.7% vs. 2.0%), V5-right breast (29.2% vs. 7.9%), and V5-HTV (31.7% vs. 23.6%), all p < 0.001. IMRT plans were generated in less than 60 min and treatment delivered in approximately 20 min, suggesting that this technique is clinically applicable. CONCLUSIONS: IMRT significantly improved conformity and homogeneity for plans when the breast + IMNs were in the CTV. Heart and lung volume receiving high doses were decreased, but more healthy tissue received low doses. A simple algorithm based on amount of heart included in the standard plan showed limited ability to predict the benefit from IMRT.     

Optimisation of radiotherapy for carcinoma of the parotid gland: a comparison of conventional, three-dimensional conformal, and intensity-modulated techniques.

BACKGROUND AND PURPOSE: To compare external beam radiotherapy techniques for parotid gland tumours using conventional radiotherapy (RT), three-dimensional conformal radiotherapy (3DCRT), and intensity-modulated radiotherapy (IMRT). To optimise the IMRT techniques, and to produce an IMRT class solution. MATERIALS AND METHODS: The planning target volume (PTV), contra-lateral parotid gland, oral cavity, brain-stem, brain and cochlea were outlined on CT planning scans of six patients with parotid gland tumours. Optimised conventional RT and 3DCRT plans were created and compared with inverse-planned IMRT dose distributions using dose-volume histograms. The aim was to reduce the radiation dose to organs at risk and improve the PTV dose distribution. A beam-direction optimisation algorithm was used to improve the dose distribution of the IMRT plans, and a class solution for parotid gland IMRT was investigated. RESULTS: 3DCRT plans produced an equivalent PTV irradiation and reduced the dose to the cochlea, oral cavity, brain, and other normal tissues compared with conventional RT. IMRT further reduced the radiation dose to the cochlea and oral cavity compared with 3DCRT. For nine- and seven-field IMRT techniques, there was an increase in low-dose radiation to non-target tissue and the contra-lateral parotid gland. IMRT plans produced using three to five optimised intensity-modulated beam directions maintained the advantages of the more complex IMRT plans, and reduced the contra-lateral parotid gland dose to acceptable levels. Three- and four-field non-coplanar beam arrangements increased the volume of brain irradiated, and increased PTV dose inhomogeneity. A four-field class solution consisting of paired ipsilateral coplanar anterior and posterior oblique beams (15, 45, 145 and 170 degrees from the anterior plane) was developed which maintained the benefits without the complexity of individual patient optimisation. CONCLUSIONS: For patients with parotid gland tumours, reduction in the radiation dose to critical normal tissues was demonstrated with 3DCRT compared with conventional RT. IMRT produced a further reduction in the dose to the cochlea and oral cavity. With nine and seven fields, the dose to the contra-lateral parotid gland was increased, but this was avoided by optimisation of the beam directions. The benefits of IMRT were maintained with three or four fields when the beam angles were optimised, but were also achieved using a four-field class solution. Clinical trials are required to confirm the clinical benefits of these improved dose distributions.     

Significant reductions in heart and lung doses using deep inspiration breath hold with active breathing control and intensity-modulated radiation therapy for patients treated with locoregional breast irradiation

PURPOSE: To evaluate the heart and lung sparing effects of moderate deep inspiration breath hold (mDIBH) achieved using an active breathing control (ABC) device, compared with free breathing (FB) during treatment with deep tangents fields (DT) for locoregional (LR) irradiation of breast cancer patients, including the internal mammary (IM) nodes (IMNs). To compare the DT-mDIBH technique to other standard techniques and to evaluate the dosimetric effect of intensity-modulated radiation therapy (IMRT). METHODS AND MATERIALS: Fifteen patients (9 left-sided and 6 right-sided lesions) with Stages 0-III breast cancer underwent standard FB and ABC computed tomographic (CT) scans in the treatment position. A dosimetric planning study was performed. In FB, the 9 left-sided patients were planned with a 5-field technique where electron fields covering the IM region were matched to shallow tangents using wedges (South West Oncology Group [SWOG] protocol S9927 technique A). This method was compared with a 3-field DT technique covering the breast and the IMNs (SWOG S9927 technique B). Compensation with IMRT was then compared with wedges for each technique. For the 15 total patients, dosimetric planning using DT with IMRT was then reoptimized on the mDIBH CT data set for comparison. Dose-volume histograms for the clinical target volume (CTV) (including the IMNs), planning target volume (PTV), ipsilateral and contralateral breast, and organs at risk (OAR) were analyzed. In addition, normal tissue complication probabilities (NTCP) for lung and heart, mean lung doses, and the number of monitor units (MUs) for a 1.8 Gy fraction were compared. RESULTS: For the 9 left-sided patients, the mean percentage of heart receiving more than 30 Gy (heart V30) was lower with the 5-field wedged technique than with the DT wedged technique (6.8% and 19.1%, respectively, p < 0.004). For the DT technique, the replacement of wedges with IMRT slightly diminished the mean heart V30 to 16.3% (p < 0.51). The introduction of mDIBH to the DT-IMRT technique reduced the heart V30 by 81% to a mean of 3.1% (p < 0.0004). Compared with 5-field IMRT, DT-IMRT with mDIBH reduced the heart V30 for 6 of the 9 patients, entirely avoiding heart irradiation in 2 of these 6 patients. For DT-IMRT, mDIBH reduced the mean lung dose and NTCP to levels obtained with the 5-field IMRT technique. For the 15 patients planned with DT-IMRT in FB, the use of mDIBH reduced the mean percentage of both lungs receiving more than 20 Gy from 20.4% to 15.2% (p < 0.00007). With DT-IMRT, more than 5% of the contralateral breast received more than 10 Gy for 6 of the 9 left-sided patients in FB, 3 of those 9 patients in mDIBH, and only 1 of those 9 patients planned with 5 fields. The mean % of the PTV receiving more than 55 Gy (110% of the prescribed dose) was 36.4% for 5-field wedges, 33.4% for 5-field IMRT, 28.7% for DT-wedges, 12.5% for DT-IMRT, and 18.4% for DT-IMRT mDIBH. The CTV remained covered by the 95% isodose in all the DT plans but one (99.1% of the volume covered). DT-wedges required more MUs than DT-IMRT (mean of 645 and 416, respectively, p < 0.00004). CONCLUSION: mDIBH significantly reduces heart and lung doses when DT are used for LR breast irradiation including the IMNs. Compared with shallow tangents matched with electrons, DT with mDIBH reduces the heart dose (in most patients) and results in comparable lung toxicity parameters, but may increase the dose to the contralateral breast. IMRT improves dose homogeneity, slightly reduces the dose to the heart, and diminishes the number of MUs required.