2013 Vol. 4, No. 4

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Original Contributions
Abstract:
  Objective  To analyze the effectiveness and prognostic factors of precise radiotherapy for pancreatic cancer.  Methods  Totally 102 patients with pancreatic cancer received precise radiotherapy in our hospital between January 2003 and June 2012, among whom 54 received radical radiotherapy and 48 underwent adjuvant radiotherapy. Three-dimensional conformal radiotherapy (3D-CRT) was performed in 16 cases and intensity-modulated radiotherapy (IMRT) in 86 cases, with a median radiotherapy dose of 50 Gy (1.8~2.2 Gy/fraction). Concurrent capecitabine chemotherapy was carried out in 13 cases.  Results  The average overall survival time (OS) and the average time to progress-free survival (PFS) was (14±1.2) months and (9±1.1) months, respectively. The 1-, 2-, and 5-year survival rates were 63.3%, 22.6%, and 10%, respectively. Grade 3 gastrointestinal toxicity occurred in 5 cases. No grade 3 or 4 hematologic toxicity and grade 4 gastrointestinal toxicity was observed. Univariate analysis showed that weight loss of > 5 kg before treatment (P < 0.0001), T stage (P=0.011), TNM stage (P=0.007), and surgical excision (P=0.001) were significantly associated with OS and PFS. Multivariate analysis showed that surgical excision was a prognostic factor for OS (χ2=5.416, P=0.020).  Conclusions  The precise radiotherapy including 3D-CRT and IMRT can be tolerated with fewer grade 3 and 4 toxicities in pancreatic cancer patients after radical radiotherapy and adjuvant radiotherapy, thus make it feasible for the concurrent chemotherapy and the increase of radiotherapy dose. Surgical excision can improve the OS of pancreatic cancer patients.
Abstract:
  Objective  To observe the early therapeutic effects, toxicities and cosmetic results of whole breast radiotherapy with helical tomotherapy (HT) or fixed-field intensity-modulated radiotherapy (FF-IMRT) in patients with early-stage breast cancer after breast-conserving surgery.  Methods  From September 2012 to March 2013, 24 patients with stage 0-ⅡB breast cancer after breast-conserving surgery were observed. HT and FF-IMRT were applied in 12 patients after breast-conserving surgery, respectively. The radiotherapy schedule was 46-50 Gy/23-25 fractions to the whole breast with a boost to the tumor bed to 60 Gy.Eleven patients (45.8%) received chemotherapy and 18 patients(75%)received endocrine therapy.The targets and the organs-at-risk were evaluated. Toxic and cosmetic results were observed.  Results  Planning target volume(PTV)105% and PTV 110% were significantly less for HT than FF-IMRT (P=0.000, P=0.023). Homogeneity index (P=0.003) and conformity index(P=0.002) were better for HT than FF-IMRT. HT achieved significant decrease in 5 Gy (P=0.002), 20 Gy (P=0.001), and mean dose (P=0.000) for ipsilateral lung. Similar results were obtained for both lungs and heart(all P < 0.05). In the HT group, 10 patients developed grade 1 radiation dermatitis and 2 developed grade 2 radiation dermatitis; in the FF-IMRT group, 11 developed grade 1 radiation dermatitis and 1 developed grade 2 radiation dermatitis. No radiation pneumonitis was observed in all patients. Twelve patients in HT group and 11 patients in FF-IMRT group developed satisfactory cosmetic results (P > 0.05).  Conclusions  Whole breast radiotherapy with HT or FF-IMRT for patients with early-stage breast cancer after breast-conserving surgery can achieve good therapeutic effectiveness, with satisfactory cosmetic results and acceptable toxicities, although the long-term clinical benefits need further observations.
Abstract:
  Objective  To explore the radiosensitivity of different types of cervical cancer cells to different radiation doses and dose rates.  Methods  We established three cell radiosensitivity models with three cervical cancer cell lines:CaSki, HeLa, and SiHa. We then used clonogenic assay to analyze the radiosensitivity of these three cell lines to different radiation doses and dose rates.  Results  The survival fractions at 2 Gy (SF2) were 57.37%, 70.62%, and 74.77% for CaSki, HeLa, and SiHa, respectively (P=0.002). However, the survival fractions did not significantly differ when the three cell lines were treated with dose rates of 200, 400, and 600 cGy/min (P > 0.05).  Conclusions  Among these three cell lines, CaSki has the highest radiosensitivity, followed by HeLa and SiHa. The dose rate used in our experiment showed no effect on the the survival fraction of three cervical cancer cell lines.
Abstract:
  Objective  To evaluate the value of computed tomography (CT) image guidance in two-dimensional brachytherapy of cervical cancer.  Methods  A total of 92cervical cancer patients who were treated by Fletcher applicator in our hospital from April to August 2013 were enrolled in this prospective study. CT scan was required for all patients before the performance of first brachytherapy. We measured the length and angle of uterine, recorded the cases of uterus perforation and other poor positions of applicators, and then analyzed by classification.  Results  Among these 92 cases, uterine perforation occurred in 3 cases (3.3%). All these three patients were asymptomatic and the angles of their uteruses were largest among all patients. Twenty-six cases (28.3%) had poor positions of applicators, which included tandems too close to the bottom of uterine and adjacent to small intestine (n=13), tandems deviated from the center of uterine cavity excluding uterine perforation (n=9), and tandems too far away from the bottom of uterine (n=4). In one case, the position of applicator was appropriate, but the uterus was too small and surrounded by sigmoid colon.  Conclusions  Asymptomatic uterine perforation and other poor positions of applicators can be found by CT scan during brachytherapy, which provides useful information for adjusting the performance of two-dimensional brachytherapy. As an easy and convenient technique, it can be widely applied in clinical practice.
Abstract:
  Objective  To compare the radiation doses applied in helical tomotherapy (HT) and fixed-field intensity-modulated radiotherapy (FF-IMRT) for cervical cancer.  Methods  The computed tomography (CT) images of 10 patients with cervical cancer were transferred into the Eclipse planning system. HT and FF-IMRT plans were performed on a TomoTherapy treatment planning system(TPS) and an Eclipse TPS, respectively. Institutional dose-volume constraints used in cervical cancer were kept the same for both techniques. The targets and the organs-at-risk were evaluated.  Results  The coverage of HT planning group and FF-IMRT planning group met the clinical requirements of the prescribed dose. Compared with the FF-IMRT planning group, planning target volume(PTV)95% and PTV100% of HT planning group coverage increased, PTV105% became lower, Dmax and Dmean decreased, conformity index (CI) and homogeneity index (HI) improved(P=0.000). Compared with the FF-IMRT planning group, V40 and Dmax of the bladder reduced by about 7% and 1.7 Gy, respectively(P=0.000); V40 of the rectum reduced by about 8%(P=0.000), V30 and V40 of the small intestine reduced by 4%(P=0.002) and 3%(P=0.000), Dmax reduced by 2 Gy(P=0.000), V30 of the bone marrow increased by 5%(P=0.001), D5 of the femoral heads showed no difference; Dmax of the cauda equine reduced by 2 Gy(P=0.030); V20, V30, and V40 of the body reduced by 2%, 1.3%, 0.6%, respectively(P < 0.01).  Conclusions  HT has superior target HI and CI to the FF-IMRT in patients with cervical cancer, along with decreased high-dose regions in the bladder, rectum, and small intestine. Therefore, HT is feasible for the postoperative treatment of cervical cancer patients.
Abstract:
  Objective  To summarize the experience of using helical tomotherapy (HT) in treating a variety of benign and malignant tumors.  Methods  HT was applied in 33 prostate cancer patients, 23 multiple brain metastases patients, 15 germ cell tumor patients, 24 breast cancer patients, 19 pancreatic cancer patients, and 19 invasive pituitary adenoma patients from September 2012 to July 2013 in Peking Union Medical College Hospital. The results were compared with that of fixed-field intensity-modulated radiotherapy (FF-IMRT).  Results  HT showed remarkable advantaged over the FF-IMRT in terms of the homogeneity and conformity of target, simultaneous integrated boost for different dose levels, protection of risk organs, and radiation field convergence. There was no region of dose below 95% or over 105% of prescription dose in the planning target volume. Isodose line of 80% prescription dose had good conformity. Three to five different dose levels could be achieved for simultaneous integrated boost. Doses of organs-at-risk decreased by 10%-20%. No field convergence was needed, and therefore hot or cold region was eliminated.  Conclusions  HT is remarkably superior to FF-IMRT in the treatment of complex and long targets, simultaneous integrated boost of target, and protection of organs-at-risk. Its roles in treating different diseases need further study.
Abstract:
  Objective  To test and assess the output constancy of TomoTherapy HI-ART.  Methods  According to TG-148 of American Association of Physicists in Medicine (AAPM) report and by using A1SL ionization chamber, slab solid water phantom, and cheese phantom, we tested and analyzed the constancy of static output, rotational output, and energy of TomoTherapy HI-ART.  Results  The average output variation was(-0.6±1.1)% for the static condition, and 89.1% of the collected output data were within the action level of ±2%. The average variation of rotational output was (1.0±1.1)%, and 87.1% of the collected data were within ±2%. An average energy variation was (-0.01±1.26)%, and 80% data were within ±1% and 96% data within ±2%, which showed good constancy and reproducibility.  Conclusions  The output constancy of TomoTherapy HI-ART is less stable than conventional Linac, so it is important to test static and rotational output everyday to ensure the accuracy.
Abstract:
  Objective  To investigate the feasibility of two-dimensional ionization chamber array MatriXX for brachytherapy plan verification.  Methods  The well-type ion chamber was used to verify the source activity of 192Ir though the result of 60-second readout by calibration factor. The radioactive source was used to complete the calibration of EBT3 film through the Valencia skin applicator and water equivalent solid phantom. After the dose gray curve was obtained, the percentage depth dose(PDD) curves under Valencia skin applicator was drawn and then applied to calibrate the two-dimensional ionization chamber array MatriXX and get a calibration factor Kuser. The Freiburg Flap applicator with the needle was inserted, and then combined with solid water to build a phantom. After CT scanning, the catheter reconstruction and dose distribution calibration were completed in the treatment planning system (TPS). The planned dose distribution and measurement dose distribution were analyzed by software.  Results  The 192Ir dose distribution under Valencia skin applicator was similar to accelerator beam. The transverse and longitudinal symmetries were 0.17% and 0.16%, respectively. The reference dose was at 3 mm under the applicator surface, and the PDD value at 11.6 mm under the applicator surface was 46.5%. The measured dose distribution and TPS calculated dose plane was compared using gamma analysis method (3 mm/3%). The ratio of pixels within γ ≤ 1 was 97.67%, and the absolute dose measurement and calculation of dose deviation remained in 5%.  Conclusions  MatriXX has good repeatability when used as a brachytherapy dose distribution verification tool. It avoids using film and is more rapid and convenient for brachytherapy dosimetry quality assurance.
Abstract:
  Objective  To explore the necessity of multi-point real-time dose monitoring for total body irradiation.  Methods  Varian 2300 C/D accelerator 6 MV rays were applied on 25 cases ready for bone marrow transplant patients with total body irradiation. Treatment was conducted while using semiconductor dosimeters for multi-point real-time dose monitoring, and the results were monitored and recorded, during which the doses were adjusted to ensure that the radiation dose error was controlled within ±5%.  Results  The measured dose and calculated dose showed large deviations in the first multi-point real-time dose monitoring of all these 25 patients. The median deviations of the head, chest, abdomen, pelvic, thigh, knee, and ankle were 6.10%, -1.30%, 5.90%, 5.05%, -4.00%, 3.05% and 3.30%, respectively. After timely bias adjustment based on the monitoring results, the dose deviations were within ±5% in all patients, and the median deviations of above mentioned points decreased to 0.35%, -1.05%, 0.60%, 0.20%, -2.55%, 1.20% and 0.85%, respectively.  Conclusions  Multi-point real-time dose monitoring is necessary for the quality control of total body irradiation.
Abstract:
  Objective  To investigate the distribution and antimicrobial resistance of clinical bacterial isolates from medical wards in Peking Union Medical College Hospital (PUMCH) between January 1, 2011 and December 31, 2012.  Methods  A total of 2767 non-duplicate clinical isolates were collected. Disc diffusion test (Kirby-Bauer method) and automated systems were employed to study the antimicrobial resistance. The data were analyzed by WHONET 5.6 software according to Clinical and Laboratory Standards Institute (CLSI) 2012 breakpoints.  Results  Of the 2767 clinical isolates, gram-negative organisms and gram-positive cocci accounted for 65.3%(n=1807) and 34.7% (n=960), respectively. The 10 most common organisms isolated were Pseudomonas aeruginosa (11.5%), Escherichia coli (11.2%), Staphylococcus aureus (10.1%), Klebsiella pneumoniae (9.7%), Acinetobacter baumannii (9.4%), coagulase-negative staphylococci (5.0%), Enterobacter cloacae (4.1%), Enterococcus faecalis (3.8%), Xanthomonas maltophilia (3.6%), and Enterococcus faecalis (3.4%). Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase negative Staphylococcus(MRCNS) accounted for 33.8% and 75.8%, respectively. The resistance rates of methicillin-resistance strains to β-lactams and other antimicrobial agents were much higher than those of methicillin-susceptive strains including methicillin-susceptible Staphylococcus aureus (MSSA)and methicillin-susceptive coagulase-negative Staphylococcus (MSCNS). In addition, 87.2% of MRSA strains were still susceptible to trimethoprim-sulfamethoxazole, while 84.2% of MRCNS strains were susceptible to rifampin. No staphylococcal strains were resistant to vancomycin, teicoplanin, or linezolid. The resistance rates of E. faecalis strains to most of the drugs tested were much lower than those of E. faecium. However, the resistance rate of the E. faecium to chloramphenicol was only 4.7%. Several strains of both E. faecium and E. faecalis were found resistant to vancomycin. Most of the vancomycin-resistant strains were van-A and van-B types based on their phenotypes. No linezolid-resistant strains were found. Extended spectrum β-lactamases(ESBLs)-producing strains accounted for 66.5%, 32.6%, and 30.5% in E. coli, Klebsiella spp (K.pneumoniae and K. oxytoca), and P. mirabilis, respectively. The resistant rates of ESBLs-producing strains were all higher than the corresponding non-ESBLs-producing strains. The Enterbacteriaceae strains were still highly susceptible to carbapenems, with an overall resistance rate of only 0.9%-2.9%. Only one pan-resistant strain of K. pneumoniae (0.4%, 1/267)was identified. The resistance rates of P. aeruginosa to imipenem and meropenem were 23.4% and 17.4%, respectively. However, the P.aeruginosa isolates showed the lowest resistant rate (6.6%) to amikacin. Also, 56.8% and 57.5% of A. baumannii were resistant to imipenem and meropenem. A. baumannii isolates showed the lowest resistant rates 42.1% and 24.0%, respectively, to cefoperazone-sulbactam and minocycline. The prevalences of pan-resistant strains of A. baumannii and P. aeruginosa were 35.9% and 1.6%, respectively. The detection rate of β-lactamase in H. influenzae was 19.4%. More than 94% of S. pneumoniae strains were resistant to erythromycin and clindamycin.  Conclusion  Regular monitoring of the bacterial resistance to antibiotics is useful to guide the rational use of antimicrobial agents.
Abstract:
  Objective  To observe the effectiveness of free internal limiting membrane flap transplantation for unclosed idiopathic macular holes.  Methods  Three consecutive cases of idiopathic macular hole were included in the study. All the three eyes had undergone vitrectomy and internal limiting membrane peeling previously but the macular holes were not closed. Free internal limiting membrane flap transplantation was performed for all three cases. Fundus examination and optical coherence tomography were used to observe whether the macular holes were closed after the operation.  Results  Macular holes were closed in all three cases, and the situation was stable during the follow-up period of 10 months to 1 year. No complication was recorded.  Conclusions  The described free internal limiting membrane flap transplantation technique is helpful in treating unclosed idiopathic macular holes after initial surgery. Long-term studies in larger sample are needed to further evaluate the efficacy and safety of this technique.
Abstract:
  Objective  To compare the difference of central corneal thickness (CCT) before and after mydriasis measured with A-ultrasound pachymetry and Pentacam three-dimensional anterior segment analysis system.  Methods  From August 2011 to November 2011, the CCT of 130 eyes from 65 adult patients with myopia in Peking Union Medical College Hospital were measured with A-ultrasound pachymetry and Pentacam Scheimpflug system before and after mydriasis using compound tropicamide eye drops.  Results  The CCT values obtained with A-ultrasound pachymetry before and after mydriasis were (536.70±39.60)μm and (548.31±39.22)μm, respectively. The value after mydriasis was significantly higher than that before mydriasis (P=0.000). The CCT values obtained with Pentacam three-dimensional anterior segment analysis system before and after mydriasis were (539.57±39.73)μm and (545.99±39.47)μm, respectively. The value after mydriasis was also significantly higher than that before mydriasis (P=0.000). CCT value obtained with Pentacam three-dimensional anterior segment analysis system was significantly higher than A-ultrasound pachymetry before mydriasis (P=0.000); however, there was no significant difference in CCT between the two methods after mydriasis (P=0.081).  Conclusions  Values of CCT measured after mydriasis are higher than before mydriasis. Therefore, the values of CCT measured before mydriasis may be more accurate, which can help to provide a better option for choosing operative methods and evaluating the safety of refractive surgery.
2013, 4(4): 345-349. doi: 10.3969/j.issn.1674-9081.2013.04.001
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