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Objective:To develop a dose prediction-based quantitative evaluation method of the quality of radiotherapy plans, and to verify the clinical feasibility and clinical value of the method .Methods:The 3D U-Netwas trained using the radiotherapy plans of 45 rectal cancer cases that were formulated by physicists with more than five years of radiotherapy experience. After obtaining 3D dose distribution using 3D U-Net prediction, this study established the plan quality metrics of intensity modulated radiotherapy(IMRT) rectal cancer radiotherapy plans using dose-volume histogram(DVH) indexes of dose prediction. Then, the initial scores of rectal cancer radiotherapy plans were determined.Taking the predicted dose as the optimization goal, the radiotherapy plans were optimized and scored again. The clinical significance of this scoring method was verified by comparing the scores and dosimetric parameters of the 15 rectal cancer cases before and after optimization.Results:The radiotherapy plans before and after optimization all met the clinical dose requirements. The total scores were(77.21±9.74) before optimization, and (88.78±4.92) after optimization. Therefore, the optimized radiotherapy planswon increased scores with a statistically significant difference( t=-4.105, P<0.05). Compared to the plans before optimization, the optimized plans show decreased Dmax of all organs at risk to different extents. Moreover, the Dmax, V107%, and HI of PTV and the Dmax of the bladder decreased in the optimized plans, with statistically significant differences ( t=2.346-5.771, P<0.05). There was no statistically significant difference in other indexes before and after optimization ( P>0.05).The quality of the optimized plans were improved to a certain extent. Conclusions:This study proposed a dose prediction-based quantitative evaluation method of the quality of radiotherapy plans. It can be used for the effective personalized elevation of the quality of radiotherapy plans, which is beneficial to effectively compare and review the quality of clinical plans determined by different physicists and provide personalized dose indicators. Moreover, it can provide great guidance for the formulation of clinical therapy plans.
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Locoregional failure is the most frequent pattern of failure in locally advanced head and neck cancer patients and it leads to death in most of the patients. Second primary tumors occurring in the other head and neck region reach up to almost 40% of long-term survivors. Recommended and preferred retreatment option in operable patients is salvage surgical resection, reporting a 5-year overall survival of up to 40%. However, because of tumor location, extent, and underlying comorbidities, salvage surgery is often limited and compromised by incomplete resection. Reirradiation with or without combined chemotherapy is an appropriate option for unresectable recurrence. Reirradiation is carefully considered with a case-by-case basis. Reirradiation protocol enrollment is highly encouraged prior to committing patient to an aggressive therapy. Radiation doses greater than 60 Gy are usually recommended for successful salvage. Despite recent technical improvement in intensity-modulated radiotherapy (IMRT), the use of concurrent chemotherapy, and the emergence of molecularly targeted agents, careful patient selection remain as the most paramount factor in reirradiation. Tumors that recur or persist despite aggressive prior chemoradiation therapy imply the presence of chemoradio-resistant clonogens. Treatment protocols that combine novel targeted radiosensitizing agents with conformal high precision radiation are required to overcome the resistance while minimizing toxicity. Recent large number of data showed that IMRT may provide better locoregional control with acceptable acute or chronic morbidities. However, additional prospective studies are required before a definitive conclusion can be drawn on safety and effectiveness of IMRT.
Subject(s)
Humans , Clinical Protocols , Comorbidity , Drug Therapy , Head and Neck Neoplasms , Head , Neck , Patient Selection , Prospective Studies , Radiation-Sensitizing Agents , Radiotherapy, Intensity-Modulated , Re-Irradiation , Recurrence , Retreatment , SurvivorsABSTRACT
Objective:To compare the dosimetric differences between volumetric modulated arc radiotherapy with RapidArc and fixed-field intensity modulation radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC), and identify the techniques from which patients of different T stages can gain the maximum benefit. Methods:Sixty non-metastatic patients with NPC were randomly selected. According to the T staging of 2008 Chinese Classification, T1-T2 stage cases were observed in 20 of the 60 patients, whereas T3 and T4 stage cases were seen with 20 patients each. RapidArc and IMRT treatment plans were managed by the Eclipse treatment planning sys-tem of Varian Co., US. The dosimetry of the target volume coverage, organs at risk (OARs), monitor unit (MU) per second, and deliv-ery time were evaluated. Results:Both techniques reached the requirement of clinical treatment. The coverages of planning target vol-ume, conformity index, and homogeneity index were similar. However, the stratified analysis of T staging indicated that RapidArc plans led to an increased dose to the tumor target (P<0.05) and an improved homogeneity index (P=0.059) in the T4 stage cases. RapidArc al-lowed a statistical dose reduction to the OARs, including optic nerves, lens, temporal lobe, V20 of the parotids, larynx, and temporo-mandibular joint (P<0.05). In the T-stage stratified analysis, the D1%and Dmax of brain stem in T1-T3 stages were similar but statistical-ly low in T4 stage in the RapidArc group (P<0.05). Compared with those in IMRT group, the MUs and the delivery time in RapidArc group were reduced by 65%and 63%, respectively. Conclusion:Both RapidArc and IMRT attained the clinical requirement for NPC. RapidArc technique showed improvements in the OARs and reduction in MUs and delivery time. The target volume coverages were similar for T1-T3 stage. However, RapidArc delivered an increased dose to the tumor target in T4 stage cases, and the dose to OARs was reduced.
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Objective To evaluate the dosimetric benefits of intensity-modulated radiotherapy (IMRT) for early stage breast cancer after breast-conserving surgery. Methods Ten patients with stage Tis～2N0M0 breast cancer receiving breast-conserving surgery were selected for the study. Six cases were on the left, four were on the right. A dosimetric comparison of IMRT with conventional wedged tangential technique was performed on each patient using three dimensional treatment planning. The total prescribed dose for both plans was 50 Gy/25 fractions. Dose volume histograms (DVH) were used to compare the planning target volume (PTV) and organs at risks(OARS). Results The PTV coverage in IMRT plan was similar to that of the conventional plan (97.83 % vs 97.61%). A better dose uniformity throughout the whole breast was achieved by IMRT plan. The percentage of PTV receiving less than 95 % prescribed dose and more than 103 % prescribed dose (inhomogeneity index IHI), decreased from 25.42 % to 2.71%: the percentage of PTV receiving more than 105 % prescribed dose (V105 %) decreased from 25.79 % to 1.08 %. A better amelioration of IHI and reduction of V105 % in IMRT plans were observed in the relatively large PTV subgroup. The Dmean and percentage of volume receiving more than 30 Gy (V30) of heart from 6.72 Gy to 4.95 Gy, and from 7.23 % to 1.04 %. the Dmean and percentage of volume receiving more than 20 Gy (V20) of ipsilateral from 9.19 Gy to 7.65 Gy, and from 22.34 % to 20.18 %; the Dmean of contralateral breast decreased from 5.12 Gy to 3.52 Gy;the Dmean of contralateral lung decreased from 2.76 Gy to 1.79 Gy; the Dmean of liver decreased from 7.23 Gy to 1.04 Gy for right side patients. Conclusion Forward planning IMRT based on a standard tangential beam arrangement significantly improves the dose homogeneity throughout the target volume of intact breast and reduces the dose to OARS, especially in patients with large breast volumes who might be proposed as candidates of IMRT for intact breast.
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Objective To compared intensity modulated radiation therapy (IMRT) with conventional radiotherapy(CR) for the left side breast cancer after breast-conserving surgery in regard to the homogeneity of dose in the target area, cardiac dose and irradiation volume in the target area. Methods Thirty-eight patients received inverse planning of IMRT with dynamic multi-leaf collimation (dMLC). Prescription dose was 46Gy in breast volume with X-ray, and added electron boost dose was 14Gy in the tumor bed, with a total dose of 60Gy. Clinical target volume(CTV) and heart were evaluated with dose-volume histograms(DVH) in the two plans, with the t test taken with SPSS 11.0. Results Average received dose of 95% breast volume(D 95) was (4541?34),(4517?62)cGy, volume of 105% of dose prescription(V 105%) was 17.5%?17.6%,29.4%?26.3%, while V 110% was 0.3%?0.8%,3.7%?8.2% with IMRT and CR, respectively. Received 30Gy by the heart(V 30) was 4.6%?4.3%,18.8%?12.2%(P