Radiation therapy for lung cancer

Radiation therapy is one of the most important modalities for the treatment of lung cancer. Current progress of radiation therapy in cooperation with the development of physics and biology is remarkable. The techniques of three-dimensional treatment planning and three-dimensional conformal radiotherapy (3D-CRT) have facilitated the use of higher radiation doses. Patients with early-stage non-small cell lung cancer (NSCLC) are candidates for curative surgical resection. However, the number of elderly patients has been increasing, and these patients often have medical contraindications that prevent curative surgery. Recently, several clinical trials on stereotactic body radiotherapy (SBRT) using the 3D-CRT technique for solitary lung tumors have been reported. The local control rate for stage I disease is more than 90%, and survival rates are promising. Now a prospective multi-institutional trial is ongoing to determine whether this modality can become a standard treatment for inoperable patients or an alternative to lobetectomy. For locally advanced NSCLC, unfortunately, recent studies have demonstrated that conventional therapies may have reached a therapeutic plateau. Now several radiation dose escalation studies utilizing conventional fractionation and 3D-CRT techniques are ongoing. The strategies of almost all of these trials are to eliminate elective nodal irradiation and deliver a higher dose of radiation to gross tumor volume while sparing normal tissues. Preliminary experience has resulted in promising survival, but should be developed to integrate into the combined treatment to completely control both local disease and other microscopically involved lesions. The combination of novel chemotherapeutic agents and molecular targeting therapies with radiation therapy is being investigated. Development of molecular imaging techniques is expected to facilitate more selective dose escalation in tumors.     

Conformal radiotherapy and intensity-modulated radiotherapy--clinical data

Conformal radiotherapy (CRT) is based on three hypotheses: (i) a higher rate of local control can improve the survival rate; (ii) dose escalation can increase tumor control; and (iii) CRT allows the delivery of higher doses by decreasing the incidence of late effects. These postulates are now supported by several data. Three-dimensional conformal radiotherapy (3D-CRT) has markedly progressed since its introduction two decades ago. However, there are situations for which 3D-CRT cannot produce a satisfactory treatment plan because of complex target volume shapes or the close proximity of sensitive normal tissues. This is why intensity-modulated radiation therapy (IMRT) was introduced. Its aim is to overcome the limitations of 3D-CRT by adding modulators of beam intensity to beam shaping. IMRT can achieve nearly any dose distribution; however, the role of the planner remains crucial. CRT has been investigated mainly for prostate cancers and head and neck cancers. By and large, the clinical data, although still limited, seem to confirm the advantages of this type of radiotherapy. Dose escalation in prostate cancers improves the local control rate without increasing late effects and for this cancer site IMRT appears to be a significant advance over conventional 3D-CRT. In head and neck cancers the clinical data are still scarce but encouraging. CRT should be investigated in breast cancers with the aim of reducing the incidence of late effects. The available data underline the great potential for major progress in 3D-CRT and IMRT. The techniques are still costly and time consuming, nevertheless they merit investigation since their cost should decrease. Efforts should be concentrated on the specification of robust optimization criteria, taking into account clinical and radiobiological data.     

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.     

The role of intensity-modulated radiotherapy in the treatment of parotid tumors

PURPOSE: To compare intensity-modulated radiotherapy (IMRT) treatment plans with three-dimensional conformal radiotherapy (3D-CRT) plans to investigate the suitability of IMRT for the treatment of tumors of the parotid gland. METHODS AND MATERIALS: One 3D-CRT treatment plan and 10 IMRT treatment plans with differing beam arrangements were produced for each of nine patient data sets. The plans were compared using regret analysis, dose conformity, dose to organs at risk, and uncomplicated tumor control probability (UTCP). RESULTS: The target dose was comparable in the 3D-CRT and IMRT plans, although improvements were seen when seven and nine IMRT fields were used. IMRT reduced the mean dose to the contralateral parotid gland and the maximum doses to the brain and the spinal cord, but increased the ipsilateral lens dose in some cases. Each IMRT arrangement produced a higher UTCP than the 3D-CRT plans; the largest absolute difference was 9.6%. CONCLUSIONS: IMRT is a suitable means for treating cancer of the parotid, and a five-field class solution is proposed. It produced substantial sparing of organs at risk and higher UTCPs than 3D-CRT and should enable dose escalation.     

Nasopharyngeal carcinoma. Treatment planning with IMRT and 3D conformal radiotherapy

The study was undertaken in order to compare dose plans for intensity-modulated radiotherapy (IMRT) with 3D conformal radiotherapy (3D-CRT) dose plans in patients with nasopharyngeal carcinoma (NPC). Clinical data from 20 consecutive patients treated with IMRT are presented. For 11 patients 3D-CRT plans were made and compared to the IMRT plans with respect to doses to the planning target volumes (PTVs) and to organs at risk (OARs). For comparison of the conformation of dose to defined target volumes the conformity index (CI) was used. Target volume coverage and critical organ protection were significantly improved with IMRT compared to 3D-CRT. One-year loco-regional control, distant metastasis-free survival, and overall survival were 79%, 72%, and 80%. Two patients have had recurrence in the clinical target volume (CTV) only and seven patients have relapsed in distant organs and/or in head-and-neck areas outside the target areas. The study confirms that IMRT is superior to 3D-CRT in the treatment of NPC. As locoregional control of NPC improves we are facing an increasing number of recurrences outside the irradiated area.     

乳腺癌保乳术后行IMRT和3D-CRT治疗的剂量学参数及靶区适形度比较

目的:通过配对比较早期乳腺癌保乳术后IMRT和3D-CRT两种放疗技术模式下靶区的适形度和肺组织的受照体积-剂量参数,探索早期乳腺癌保乳术后的最佳放疗模式。方法:选取20例 I-II期（T1-2N0M0）乳腺癌保乳术后行全乳腺放疗者,对同一患者分别设计IMRT和3D-CRT两套放射计划方案,配对分析PTV及PGTVbed靶区剂量分布适形度,患侧肺组织的受照体积-剂量参数,包括V5、V10、V20、V25、V30及肺组织和心脏平均受照剂量。结果:对比3D-CRT,IMRT使肺组织平均受照剂量降低了1.34 Gy,高剂量受照区域V20体积降低了2.89%,V25体积降低了5.57%,V30体积降低了7.45%;同时提高了PTV及PGTVbed靶区内的剂量分布适形度,差异均具有统计学意义（P<0.05）。两组的心脏平均受照剂量分别为（4.01±0.38）Gy和（4.61±0.42）Gy,差异无统计学意义（P>0.05）。结论:在早期乳腺癌保乳术后的辅助放疗中,采用IMRT模式比3D-CRT模式能够获得更好的靶区适形度,靶区内的剂量分布更均匀,有利于提高局控率,同时减少了肺组织的高剂量受照区域和平均受照剂量,对正常肺组织的保护更好,值得临床上应用和推广。     

Gross tumor volume, critical prognostic factor in patients treated with three-dimensional conformal radiation therapy for non-small-cell lung carcinoma.

PURPOSE: Three-dimensional conformal radiation therapy (3D-CRT) has recently become widely available with applications for patients with non-small-cell lung cancer (NSCLC). These techniques represent a significant advance in the delivery of radiotherapy, including improved ability to delineate target contours, choose beam angles, and determine dose distributions more accurately than were previously available. The purpose of this study is to identify prognostic factors in a population of NSCLC patients treated with definitive 3D-CRT. METHODS AND MATERIALS: Between March 1991 and December 1998, 207 patients with inoperable NSCLC were treated with definitive 3D-CRT. Tumor targets were contoured in multiple sections from a treatment planning computed tomography (CT) scan. Three-dimensional treatment volumes and normal structures were reconstructed. Doses to the International Commission on Radiation Units and Measurements (ICRU) reference point ranged from 60 to 83.85 Gy with a median dose of 70 Gy. The median dose inhomogeneity was +/- 5% across planning target volume. Outcome was analyzed by prognostic factors for NSCLC including pretreatment patient and tumor-related factors (age, gender, race, histology, clinical stage, tumor [T] stage, and node [N] stage), parameters from our 3D-CRT system (gross tumor volume [GTV] in cm3), irradiation dose prescribed to isocenter, volume of normal lung exceeding 20 Gy (V20), and treatment with or without chemotherapy. The median follow-up time was 24 months (range, 7.5 months to 7.5 years). RESULTS: One and two-year overall survival rates for the entire group were 59% and 41%, respectively. Overall survival, cause-specific survival, and local tumor control were most highly correlated with the GTV in cm3. On multivariate analysis the independent variable most predictive of survival was the GTV. Traditional staging such as T, N, and overall clinical staging were not independent prognostic factors. Patients receiving ICRU reference doses > or =70 Gy had better local control and cause-specific survivals than those treated with lower doses (p = 0.05). Increased irradiation dose did not improve overall survival. CONCLUSIONS: GTV as determined by CT and 3D-CRT planning is highly prognostic for overall and cause-specific survival and local tumor control and may be important in stratification of patients in prospective therapy trials. T, N, and overall stage were not independent prognostic factors in this population of patients treated nonsurgically. The value of dose escalation beyond 70 Gy should be tested prospectively by clinical trial.     

Comparison of treatment plans using intensity-modulated radiotherapy and three-dimensional conformal radiotherapy for paranasal sinus carcinoma

PURPOSE: To compare intensity-modulated radiotherapy (IMRT) treatment planning with three-dimensional conformal radiotherapy (3D-CRT) planning for paranasal sinus carcinoma. MATERIALS AND METHODS: Treatment plans using traditional 3-field technique, 3D-CRT planning, and inverse planning IMRT were developed for a case of paranasal sinus cancer requiring adjuvant radiotherapy. Plans were compared with respect to dose conformality, dose-volume histograms, doses to critical normal tissues, and ease of treatment delivery. RESULTS: The inverse-planned IMRT technique was more conformal around the tumor target volume than conventional techniques. The dose-volume histograms demonstrated significantly better critical normal-tissue sparing with the IMRT plans, while able to deliver a minimum dose of 60 Gy to the clinical tumor volume and 70 Gy to the gross tumor volume. Acute toxicities in our analysis were minimal. CONCLUSIONS: IMRT planning provided improved tumor target coverage when compared to 3D-CRT treatment planning. There was significant sparing of optic structures and other normal tissues, including the brainstem. Inverse planning IMRT provided the best treatment for all paranasal sinus carcinomas, but required stringent immobilization criteria. Further studies are needed to establish the true clinical advantage of this modality.     

三维适形放射治疗局部晚期非小细胞肺癌的临床观察

目的评价放弃选择性区域淋巴结照射的低分割三维适形放射治疗局部晚期非小细胞肺癌的毒性和近期疗效.方法 45例经病理组织学和(或)细胞学确诊的局部晚期非小细胞肺癌患者接受三维适形放射治疗,分割剂量2.5～3 Gy/次,5次/周,放疗总量DT 63～72.5 Gy.靶区仅包括肿瘤原发灶和转移淋巴结,放疗前MVP或CAP方案化疗不超过两个周期.结果总有效率为84.5%.1,2年的局部控制率分别为48.9%和37.8%;1,2年生存率分别为65.4%和42.8%.中位生存期13.1个月.未出现Ⅲ级以上的放射性肺炎和放射性食管炎.7例(15.6%)患者在随访期间出现选择性淋巴结失败.结论三维适形放射治疗局部晚期非小细胞肺癌提高了局部控制率和近期疗效,减轻了放疗的毒副反应.放弃选择性区域淋巴结照射并没有明显增加区域淋巴结的复发率,是实现剂量提升的重要途径.     

Feasibility of using intravenous contrast-enhanced computed tomography (CT) scans in lung cancer treatment planning

Background and purpose

To investigate the feasibility of using intravenous contrast-enhanced computed tomography (CT) scans in 3-dimensional conformal radiotherapy (3D-CRT), stereotactic body radiation therapy (SBRT) and intensity-modulated radiotherapy (IMRT) treatment planning for lung cancers, respectively.

Materials and methods

Twelve patients with bulky lung tumors and 14 patients with small lung tumors were retrospectively analyzed. Each patient took two sets of CT in the same position with active breathing control (ABC) technique before and after intravenous contrast agent (CA) injections. Bulky tumors were planned with 3D-CRT, while SBRT plans were generated for patients with small tumors based on CT scans with intravenous CA. In addition, IMRT plans were generated for patients with bulky tumors to continue on a planning study. All plans were copied and replaced on the scans without intravenous CA. The radiation doses calculated from the two sets of CTs were compared with regard to planning volumes (PTV), the organ at-risk (OAR) and the lungs using Wilcoxon’s signed rank test.

Results

In comparisons for 3D-CRT plans, CT scans with intravenous CA reduced the mean dose and the maximum dose of PTV with significant differences (p < 0.05) that were within 1.0%. Comparing IMRT and SBRT plans, CT scans with intravenous CA obviously increased the minimum irradiation dose and dose of 95% volume of target received (D₉₅) for targets, respectively (p < 0.05). There was no statistical significance for lung parameters between two sets of scans in SBRT plans and IMRT plans.

Conclusions

The enhanced CT scans can be used for both target delineation and treatment planning in 3D-CRT. The dose difference caused by intravenous CA is small. But for SBRT and IMRT, the minimum irradiation dose in targets may be estimated to be increased up to 2.71% while the maximum dose may be estimated to be decreased up to 1.36%. However, the difference in dose distribution in most cases were found to be clinical tolerable.     

Beam intensity modulation using tissue compensators or dynamic multileaf collimation in three-dimensional conformal radiotherapy of primary cancers of the oropharynx and larynx, including the elective neck

Introduction: The treatment of midline tumors in the head and neck by conventional radiotherapy almost invariably results in xerostomia. This study analyzes whether a simple three-dimensional conformal radiotherapy (3D-CRT) technique with beam intensity modulation (BIM) (using a 10-MV beam of the MM50 Racetrack Microtron) can spare parotid and submandibular glands without compromising the dose distribution in the planning target volume (PTV).

Methods: For 15 T2 tumors of the tonsillar fossa with extension into the soft palate (To) and 15 T3 tumors of the supraglottic larynx (SgL), conventional treatment plans, consisting of lateral parallel opposed beams, were used for irradiation of both the primary tumor (70 Gy) and the elective neck regions (46 Gy). Separately, for each tumor a 3-D conformal treatment plan was developed using the 3-D computer planning system, CadPlan, and Optimize, a noncommercial program to compute optimal beam profiles. Beam angles were selected with the intention of optimal sparing of the salivary glands. The intensity of the beams was then modulated to achieve a homogeneous dose distribution in the target for the given 3D-CRT techniques. The dose distributions, dose–volume histograms (DVHs) of target and salivary glands, tumor control probabilities (TCPs), salivary gland volumes absorbing a biologically equivalent dose of greater than 40 or 50 Gy, and normal tissue complication probabilities (NTCPs) of each treatment plan were computed. The parameters of the 3D-CRT plans were compared with those of the conventional plans.

Results: In comparison with the conventional technique, the dose homogeneity in the target volume was improved by the conformal technique for both tumor sites. In addition, for the SgL conformal technique, the average volumes of the parotid glands absorbing a BED of greater than 40 Gy (V40) decreased by 23%, and of the submandibular glands by 7% (V40) and 6% (V50). Consequently, the average NTCPs for the parotid and submandibular glands were reduced by 7% and 6%, respectively. For the To conformal techniques, the V40 of the parotid glands was decreased on average by 31%, resulting in an average reduction of the NTCP by 49%. Both the average V50 and the NTCP of the submandibular glands were decreased by 7%.

Conclusion: For primary tumors of the oropharynx, the parotid glands could be spared to a considerable degree with the 3D-CRT technique. However, particularly the ipsilateral submandibular gland could not be spared. For primary tumors of the larynx, the 3D-CRT technique allows sparing of all salivary glands to a considerable and probably clinically relevant degree. Moreover, the conformal techniques resulted in an increased dose homogeneity in the PTV of both tumor sites.     

Accelerated partial-breast intensity-modulated radiotherapy results in improved dose distribution when compared with three-dimensional treatment-planning techniques

PURPOSE: To compare dose distribution and normal tissue sparing in partial-breast treatment using three-dimensional conformal radiotherapy (3D-CRT) vs. intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: Sixty-three patients with Tis-1N0M0 breast cancer were treated on a Phase II prospective accelerated partial-breast IMRT protocol at two facilities between April 2004 and January 2006. Fifty-six patients had data sets sufficient to adequately contour all structures. These cases were subsequently replanned with 3D-CRT techniques using the same contours, to compare the dose distribution patterns of 3D-CRT vs. IMRT. RESULTS: The average planning target volume (PTV) to ipsilateral breast (IB) ratio was 24% (range, 7-58%). The average volume of IB receiving 25%, 50%, 75%, and 100% of the prescribed dose was 4.0%, 5.0%, 5.5%, and 10.5% less with IMRT than with 3D (p < 0.01). The dose reduction to normal breast was further improved in the subset of patients whose PTV to IB ratio was >25%, and in patients with contoured breast volume <750 cm(3). No difference was detected in delivery to the lumpectomy cavity or clinical target volume. The PTV volume receiving 95% of the dose was higher in the 3D conformal plans (p < 0.01), but no significant difference was observed in the PTV volume receiving 90% (p = 0.17). The irradiated heart and lung volumes were small with both techniques but also favored IMRT. CONCLUSIONS: In T1N0 patients treated with external beam partial-breast radiotherapy, IMRT improves normal tissue sparing in the ipsilateral breast compared with 3DRT, without compromising dose delivery to the lumpectomy cavity and clinical target volume.     

Treatment planning with protons for pediatric retinoblastoma,medulloblastoma, and pelvic sarcoma: How do protons compare with other conformal techniques?

PURPOSE: To calculate treatment plans and compare the dose distributions and dose-volume histograms (DVHs) for photon three-dimensional conformal radiation therapy (3D-CRT), electron therapy, intensity-modulated radiation therapy (IMRT), and standard (nonintensity modulated) proton therapy in three pediatric disease sites. METHODS AND MATERIALS: The tumor volumes from 8 patients (3 retinoblastomas, 2 medulloblastomas, and 3 pelvic sarcomas) were studied retrospectively to compare DVHs from proton therapy with 3D-CRT, electron therapy, and IMRT. In retinoblastoma, several planning techniques were analyzed: A single electron appositional beam was compared with a single 3D-CRT lateral beam, a 3D-CRT anterior beam paired with a lateral beam, IMRT, and protons. In medulloblastoma, three posterior fossa irradiation techniques were analyzed: 3D-CRT, IMRT, and protons. Craniospinal irradiation (which consisted of composite plans of both the posterior fossa and craniospinal components) was also evaluated, primarily comparing spinal irradiation using 3D-CRT electrons, 3D-CRT photons, and protons. Lastly, in pelvic sarcoma, 3D-CRT, IMRT, and proton plans were assessed. RESULTS: In retinoblastoma, protons resulted in the best target coverage combined with the most orbital bone sparing (10% was the mean orbital bone volume irradiated at > or =5 Gy for protons vs. 25% for 3D-CRT electrons, 69% for IMRT, 41% for a single 3D lateral beam, 51% for a 3D anterolateral beam with a lens block, and 65% for a 3D anterolateral beam without a lens block). A single appositional electron field was the next best technique followed by other planning approaches. In medulloblastoma, for posterior fossa and craniospinal irradiation, protons resulted in the least dose to the cochlea (for only posterior fossa irradiation at > or =20 Gy, 34% was the mean cochlear volume irradiated for protons, 87% for IMRT, 89% for 3D-CRT) and hypothalamus-pituitary axis (for only posterior fossa irradiation at > or =10 Gy, 21% was the mean hypothalamus-pituitary volume irradiated for protons, 81% for IMRT, 91% for 3D-CRT); additional dose reductions to the optic chiasm, eyes, vertebrae, mandible, thyroid, lung, kidneys, heart, and liver were seen. Intensity-modulated radiotherapy appeared to be the second best technique for posterior fossa irradiation. For spinal irradiation 3D-CRT electrons were better than 3D-CRT photons in sparing dose to the thyroid, heart, lung, kidney, and liver. With pelvic sarcoma, protons were superior in eliminating any dose to the ovaries (0% of mean ovarian volume was irradiated at > or =2 Gy with protons) and to some extent, the pelvic bones and vertebrae. Intensity-modulated radiotherapy did show more bladder dose reduction than the other techniques in pelvic sarcoma irradiation. CONCLUSIONS: In the diseases studied, using various techniques of 3D-CRT, electrons, IMRT, and protons, protons are most optimal in treating retinoblastomas, medulloblastomas (posterior fossa and craniospinal), and pelvic sarcomas. Protons delivered superior target dose coverage and sparing of normal structures. As dose-volume parameters are expected to correlate with acute and late toxicity, proton therapy should receive serious consideration as the preferred technique for the treatment of pediatric tumors.     

Optimization of conformal thoracic radiotherapy using cone-beam CT imaging for treatment verification

PURPOSE: Megavoltage cone-beam computed tomography (MVCBCT) has been proposed for treatment verification in conformal radiotherapy. However, the doses required for such imaging may compromise the quality of the delivered dose distribution. The present paper explores the effect of cone-beam imaging on dose homogeneity and critical organ dose and the use of our new tool, adapted intensity-modulated radiation therapy (AIMRT). METHODS AND MATERIALS: Three types of treatment plans were devised (3D-CRT [three-dimensional conformal radiotherapy], IMRT [intensity-modulated radiotherapy], and AIMRT) based on 4 patients with thoracic malignancies. MVCBCT fields were then integrated into the plans. The MVCBCT technique used 21 imaging portals at 10 degrees intervals. The MVCBCT apertures were shaped to conform to the planning target volume with a 6-mm margin. In a second set of plans, the field size was expanded by a further 2 cm. The unoptimized MVCBCT dose distribution was incorporated into the IMRT plan using AIMRT. RESULTS: Normal-tissue complication probability with MVCBCT is acceptable for all plans at the 66.6 Gy level, but exceeds tolerance for both 3D-CRT alone and 3D-CRT with MVCBCT at higher doses. In contrast, the use of AIMRT planning with MVCBCT allowed safe dose escalation to 85 Gy. Expanding the MVCBCT aperture provided better anatomic visibility with an acceptable lung dose. The results using IMRT with MVCBCT fell between the values measured for 3D-CRT and AIMRT with MVCBCT. CONCLUSION: The present study is the first to demonstrate that MVCBCT can be incorporated into 3D-CRT and IMRT planning with minimal effect on planning target volume homogeneity and dose to critical structures. This paves the way for highly conformal radiotherapy at greater doses delivered with increased confidence and safety.     

Ⅰ期睾丸精原细胞瘤术后三维适形放疗与常规放疗的剂量学对比分析

目的 比较睾丸精原细胞瘤术后行三维适形放疗（3D CRT）与传统放疗照射靶区及周围正常组织的剂量学差异。方法 对12例确诊的Ⅰ期睾丸精原细胞瘤患者经腹股沟高位睾丸切除术后行术后放疗。利用治疗计划系统（TPS） 为每例患者设计3D-CRT计划和虚拟常规计划（VCP）。应用剂量体积直方图（DVH）比较两种治疗计划的靶区适形度指数（CI）、不均匀性指数（HI）和正常组织受量。结果 3D-CRT计划的CI及HI均优于VCP计划,CI值分别为0.88±0.06和0.82±0.05,HI值分别为0.15±0.03和0.29±0.11（P＜0.05）。3D-CRT计划的照射体积（IV）显著低于VCP计划,分别为（5268.20±1018.60）cm³和（5970.24±1471.49）cm³（P＜0.05）。3D-CRT计划的小肠平均剂量以及V15低于VCP计划（P＜0.05）,睾丸的平均剂量低于VCP计划（P＜0.05）。结论 常规照射野是根据患者的骨性标志确定下来,未必适应于每个患者,3D-CRT更加个体化。此外3D-CRT在靶区覆盖率、剂量适形度及剂量均匀性方面均优于虚拟常规计划,同时降低了小肠低剂量照射体积和睾丸的散射剂量,这些剂量学方面的优势能否转换成临床受益还需要进一步临床验证。     

Potential outcomes of modalities and techniques in radiotherapy for patients with hypopharyngeal carcinoma.

BACKGROUND AND PURPOSE: To determine potential improvements in treatment outcome for patients with hypopharyngeal carcinoma, T4N0M0, using proton and intensity modulated photon radiotherapy (IMRT) compared to a standard 3D conformal radiotherapy treatment (3D-CRT) in terms of local tumour control probability, TCP, and normal tissue complication probability (NTCP) for the spinal cord and the parotid glands using. PATIENTS AND METHODS: Using the three-dimensional treatment-planning system, Helax-TMS, 5 patients were planned with protons, IMRT, and 3D-CRT plans. The prescribed dose used was 30 fractions x 2.39 Gy for the protons and IMRT and 35 fractions x 2.00 Gy for 3D-CRT. The treatment plans were evaluated using dose volume data and dose response models were used to calculate TCP and NTCP. The target volumes were delineated to spare the parotid glands. A dose escalation was made for protons and IMRT using NTCP constraints to the spinal cord. RESULTS: On average, protons and IMRT increase TCP by 17% compared to 3D-CRT. For the spinal cord NTCP values are zero for all methods and patients. Average NTCP values for the parotid glands were >90% for 3D-CRT and significantly lower for protons and IMRT varying from 43-65%. The average parotid gland dose was 33 Gy for the protons, 38 Gy for IMRT and 48 Gy for 3D-CRT. CONCLUSIONS: Protons and IMRT gave a significant TCP increase compared to 3D-CRT while no significant difference between protons and IMRT was found. Protons generally show lower non-target tissue doses, which indicates a possibility for further dose escalation. Large individual dose differences between protons and IMRT for parotid glands indicate that some patients may benefit more from protons and others from IMRT.     

Radiotherapy of liver malignancies. From whole liver irradiation to stereotactic hypofractionated radiotherapy

AIMS AND BACKGROUND: Until recently radiotherapy of hepatic malignancies has played a limited role due to the well-known limited radiotolerance of the liver. The aim of this paper is to review the available data on the risk of radiation-induced liver disease (RILD) and to define the modern role of radiotherapy in the management of patients with metastatic or primary liver malignancies. METHODS: The advent of three-dimensional conformal treatment planning with dose-volume histogram analysis has made the study of partial liver irradiation possible. Limited portions of the liver may withstand high doses of radiation with minimal risk of RILD. Patients with solitary unresectable liver tumors may be treated with high-dose radiotherapy with curative intent. Recently, the feasibility of stereotactically guided treatment techniques with a single fraction or few treatment sessions has been explored in numerous institutions. RESULTS: The radiation tolerance of the whole liver found by several investigations is in the order of approximately 30 Gy, which seriously restricts its clinical application. The role of whole liver irradiation therefore appears of limited benefit in the palliation of patients with multiple liver metastases. The use of three-dimensional conformal techniques has made partial liver irradiation possible to doses in the 70-80 Gy range with conventional fractionation. At least two published series have reported improved local control and survival rates with dose escalation with three-dimensional conformal radiotherapy in patients with unresectable liver metastases. Similar outcomes have been recently reported with single dose (or hypofractionated) stereotactic radiotherapy both in metastatic and primary hepatic malignancies with minimal morbidity. Accurate target delineation and treatment reproducibility are the key to the success of this novel treatment approach, and specific treatment planning techniques and patient setup procedures must be developed to implement it. CONCLUSIONS: Stereotactic high-dose radiotherapy is technically feasible for the treatment of inoperable liver malignancies, with the potential of high local control and low morbidity. Definitive evidence on the clinical advantages of this technique over other more established treatments can only be gathered from well-designed clinical studies.     

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.     

Dose and volume reduction for normal lung using intensity-modulated radiotherapy for advanced-stage non-small-cell lung cancer

PURPOSE: To investigate dosimetric improvements with respect to tumor-dose conformity and normal tissue sparing using intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3D-CRT) for advanced-stage non-small-cell lung cancer (NSCLC). METHODS AND MATERIALS: Forty-one patients with Stage III-IV and recurrent NSCLC who previously underwent 3D-CRT were included. IMRT plans were designed to deliver 63 Gy to 95% of the planning target volume using nine equidistant coplanar 6-MV beams. Inverse planning was performed to minimize the volumes of normal lung, heart, esophagus, and spinal cord irradiated above their tolerance doses. Dose distributions and dosimetric indexes for the tumors and critical structures in both plans were computed and compared. RESULTS: Using IMRT, the median absolute reduction in the percentage of lung volume irradiated to >10 and >20 Gy was 7% and 10%, respectively. This corresponded to a decrease of >2 Gy in the total lung mean dose and of 10% in the risk of radiation pneumonitis. The volumes of the heart and esophagus irradiated to >40-50 Gy and normal thoracic tissue volume irradiated to >10-40 Gy were reduced using the IMRT plans. A marginal increase occurred in the spinal cord maximal dose and lung volume >5 Gy in the IMRT plans, which could be have resulted from the significant increase in monitor units and thus leakage dose in IMRT. CONCLUSION: IMRT planning significantly improved target coverage and reduced the volume of normal lung irradiated above low doses. The spread of low doses to normal tissues can be controlled in IMRT with appropriately selected planning parameters. The dosimetric benefits of IMRT for advanced-stage non-small-cell lung cancer must be evaluated further in clinical trials.