Dosimetric advantages of generalised equivalent uniform dose-based optimisation on dose-volume objectives in intensity-modulated radiotherapy planning for bilateral breast cancer.

OBJECTIVE: We compared and evaluated the differences between two models for treating bilateral breast cancer (BBC): (i) dose-volume-based intensity-modulated radiation treatment (DV plan), and (ii) dose-volume-based intensity-modulated radiotherapy with generalised equivalent uniform dose-based optimisation (DV-gEUD plan). METHODS: The quality and performance of the DV plan and DV-gEUD plan using the Pinnacle(3) system (Philips, Fitchburg, WI) were evaluated and compared in 10 patients with stage T2-T4 BBC. The plans were delivered on a Varian 21EX linear accelerator (Varian Medical Systems, Milpitas, CA) equipped with a Millennium 120 leaf multileaf collimator (Varian Medical Systems). The parameters analysed included the conformity index, homogeneity index, tumour control probability of the planning target volume (PTV), the volumes V(20 Gy) and V(30 Gy) of the organs at risk (OAR, including the heart and lungs), mean dose and the normal tissue complication probability. RESULTS: Both plans met the requirements for the coverage of PTV with similar conformity and homogeneity indices. However, the DV-gEUD plan had the advantage of dose sparing for OAR: the mean doses of the heart and lungs, lung V(20) (Gy), and heart V(30) (Gy) in the DV-gEUD plan were lower than those in the DV plan (p<0.05). CONCLUSIONS: A better result can be obtained by starting with a DV-generated plan and then improving it by adding gEUD-based improvements to reduce the number of iterations and to improve the optimum dose distribution. Advances to knowledge The DV-gEUD plan provided superior dosimetric results for treating BBC in terms of PTV coverage and OAR sparing than the DV plan, without sacrificing the homogeneity of dose distribution in the PTV.

Determination of Au and Pt in titanate nanotube catalysts by photon activation analysis.

This study demonstrated the determination of Au and Pt concentrations in titanate nanotube-supported (abbreviated as TNT-supported) metal catalysts by photon activation and their catalytic activity with respect to metal concentration. An 18MV medical accelerator was used as photon source to activate the metals and generate radionuclides for gamma-ray spectroscopic analysis. Two TNT-supported metal catalysts, namely Au/NaTNT and Pt/MTNT (M=Na(+) and Cs(+)), were prepared and the Au and Pt concentrations and the respective loading efficiencies were determined. The detection sensitivities with respect to the photon activated radionuclides were estimated to select the most sensitive gamma rays for the determination of Au and Pt concentrations. The loading efficiency for Au/NaTNT decreased with increasing Au concentration prepared, while it was almost 100% for Pt loading in Pt/MTNT of various prepared Pt concentrations. The Au/NaTNT containing 2.53 wt% of Au effectively oxidized CO at a much lower reaction temperature than the lower concentration ones. For cinnamaldehyde hydrogenation reaction, the catalytic activity of Pt/TNT with different Pt loadings followed the order of 2.9>2.3>0.9>0.5 wt%. This photon activation technique, with minus interfering radionuclides in the gamma-ray spectra and induced radioactivities in the samples, is perfectly suited to the determination of metal concentrations in TNT-supported catalysts, that might contain considerable amounts of alkali metal ions.

Using medical accelerators and photon activation to determine Sr/Ca concentration ratios in teeth.

This paper describes a photon activation method, studied by using two medical accelerators (energies: 15 and 18 MeV) as photon sources, for determining Sr and Ca levels and Sr/Ca ratios in tooth samples. The radionuclides formed by various photonuclear reactions were measured and identified using a gamma-spectrometry with HPGe detection system. The yields of the corresponding photonuclear reactions and the detection sensitivities for the alkaline earth metals (e.g., Ca, Sr) were surveyed and estimated in relation to the radiation dose. The minimum detectable amount of Sr was estimated to be less than 1 microg g(-1), allowing the Sr/Ca ratios in teeth to be determined conveniently. The Sr/Ca ratios in deciduous and permanent tooth samples obtained from local dental clinics were 0.390 and 0.565 mg g(-1), respectively. This photon activation method of determining Sr/Ca ratio in bones and teeth using medical accelerators for cancer treatment is thought to be useful also in biological and archaeological studies.

Relationship between radioactivity of radium and concentrations of barium and lead in hokutolite.

Hokutolite consists of barite (BaSO(4)) and anglesite (PbSO(4)), and contains significant amounts of radium isotopes as a radioactive mineral. Photon activation and gamma-ray spectrometry were employed to determine Ba, Pb and (226)Ra contents in hokutolite samples and to investigate the correlation between (226)Ra activity and both Ba and Pb content. (226)Ra activity in 30 hokutolite samples were estimated in the range of 40-65Bq/g and was positively related to Ba content (r=0.859, p<0.001), but independent of Pb content (r=-0.236, p=0.217). Experimental results implied that (226)Ra preferably precipitated with Ba over Pb. The (226)Ra activity in hokutolite from the Peitou Hot Spring was experimentally estimated based on the Ba/Pb ratio and expressed as (226)Ra (Bq/g)=14.67 (Ba/Pb)(molar)+14.13.

Treatment outcomes and prognostic factors in patients with supratentorial low-grade gliomas.

Low-grade gliomas account for 10-15% of all adult primary intracranial tumours. Currently, there is no consensus on the treatment strategy for low-grade gliomas. This study was designed to evaluate the treatment outcomes, prognostic factors and radiation-related late complications, as well as to assess whether or not post-operative radiotherapy has benefit on local control and overall survival in this population. We retrospectively reviewed 93 consecutive adult patients with supratentorial low-grade gliomas diagnosed at our institution from July 1985 to December 1997. All patients underwent surgical intervention and 60 of them received post-operative radiotherapy. With a median follow-up of 110 months for surviving patients, the 5-year overall and progression-free survival rates were 57% and 47%, respectively. 46 patients experienced local progression of disease during the follow-up period. In multivariate analysis, age at diagnosis, extent of surgery and post-operative Karnofsky performance status showed independent prognostic significance for progression-free and overall survival rates. Post-operative radiotherapy had independent prognostic value for progression-free survival. This analysis has changed our practice and we suggest that aggressive surgical resection and post-operative radiotherapy might be considered for patients with low-grade gliomas. Further efforts should be made to optimize radiotherapy techniques and to integrate new therapeutic modalities.

Attenuation of radiation dose by the skull base bone in patients with nasopharyngeal carcinoma: clinical importance.

PURPOSE: To measure the degree of attenuation of radiation dose by the skull base bone in patients with nasopharyngeal carcinoma (NPC) and to study its clinical importance. MATERIALS AND METHODS: Isodose distribution in 11 patients with NPC who received bilaterally opposed large-field irradiation (1.8 Gy per fraction) was studied with a three-dimensional treatment planning system with tissue inhomogeneity correction. Also studied were the sites of local tumor recurrence in 37 patients with NPC and skull base destruction (>/=0.5 cm) or intracranial invasion treated with radiation therapy from January 1989 to December 1992. Regression analyses were performed. RESULTS: In the dosimetric study, the low-dose areas (<1.65 Gy) were located at the level of the skull base in all 11 patients. A significantly positive correlation between the maximum width of the skull base bone and the low-dose volume (<1.65 Gy) was demonstrated (P =.003, linear regression). In the clinical study, local tumor recurrence was noted in 18 patients (49%). The sites of local recurrence included skull base in 16 patients (43%) and nasopharynx in six patients (16%). Wider skull base bone was a significant predictor of skull base recurrence after radiation therapy (P =.03, logistic regression). CONCLUSION: Herein demonstrated is the inadequacy of the radiation dose over the skull base due to attenuation by the skull base bone. The relationship between width of skull base bone and skull base tumor recurrence also is established.

Multivariate analysis of pulmonary fibrosis after electron beam irradiation for postmastectomy chest wall and regional lymphatics: evidence for non-dosimetric factors.

BACKGROUND AND PURPOSE: To evaluate the factors associated with pulmonary fibrosis after postmastectomy electron beam irradiation of chest wall and regional lymphatics in patients with breast cancer. MATERIALS AND METHODS: From July 1987 through July 1994, 109 women with stage II and III breast cancer receiving modified radical mastectomies were managed by postoperative electron beam irradiation. Doses of 46 to 50.4 Gy were delivered to the chest wall covered with bolus, internal mammary nodes, supraclavicular nodes and axillary lymph nodes via 12 or 15 MeV single portal electron beam. Seventeen patients received additional 10-16 Gy surgical scar boost via 9 MeV electron beam. Comparison of pre-treatment and post-treatment chest X-ray films were used to monitor the development of pulmonary fibrosis. RESULTS: Only Grade 1 radiation-induced late pulmonary toxicity was noted in 33 patients (29%). Twenty-six patients (24%) developed pulmonary fibrosis under unbolused chest wall. Lung fibrosis under bolused chest wall was noted in 11 patients (10%). Statistical difference (P<0.01) was noted between the incidence of fibrosis in these two sites. In multivariate analysis of lung fibrosis under unbolus-covered chest wall, the independent prognostic factors are low body mass index (BMI) (P<0.01), tamoxifen taking (P=0.03), and no treatment interruption (P=0.03). No independent factor was associated with lung fibrosis under bolus-covered chest wall in multivariate analysis. CONCLUSIONS: In the analysis of pulmonary fibrosis induced by unbolused electron beam, BMI rather than body weight and body height is a strong prognostic factor. Tamoxifen and short overall time can predispose the development of lung fibrosis.

Concomitant boost radiation therapy for inoperable non-small-cell lung cancer: preliminary report of a prospective randomized study.

PURPOSE: The radiation therapy results for patients with inoperable non-small-cell lung cancer (NSCLC) have been disappointing. Tumor dose escalation using concomitant boost technique (CBT) has been shown to improve local control in a few prospective studies. This trial was carried out to prospectively assess the radiation response and acute toxicity of CBT in comparison to the conventional treatment technique (CTT). METHODS AND MATERIALS: Ninety-seven consecutive eligible patients were entered in this prospective clinical trial between November 1994 and February 1998. Patients were randomized to receive either CBT (43 patients) or CTT (54 patients) radiation therapy. These patients either refused chemotherapy or were judged as unsuitable for chemotherapy. Patients in the CBT group received 46.8 Gy in 26 fractions using large fields that encompassed the gross and occult disease. A concomitant boost of 18.2 Gy (0.7 Gy per fraction) was delivered to the gross disease using small fields with 1.5-cm margins. The small fields were treated concurrently with the large fields and the total dose to the tumor area was 65 Gy in 26 fractions. Patients in the CTT group received 70.8 Gy in 38 fractions. The acute toxicity between each group was compared. The response rate was analyzed and compared by treatment group, gender, age, stage, histology, initial Karnofsky performance score (KPS), severity of acute toxicity, and maximum body weight loss (MBWL) during treatment course. RESULTS: The demographic parameters such as sex, age, and stage were evenly distributed in each treatment group. The majority of these patients had Stage IIIA and IIIB disease. Overall median treatment times were 39 days for the CBT group of patients and 62 days for the CTT group. No treatment-related mortality was found. There were 2 patients in the CTT group with acute RTOG Grade 3 lung toxicity, and no Grade 3 lung or esophageal toxicity was observed in CBT group. The response rates, assessed by radiographic images, were 69.8% and 48.1% for the CBT and CTT patients, respectively. Univariate and multivariate analysis revealed that patients in the CBT group, patients with better KPS, and patients with more severe acute toxicity had a higher response rate. CONCLUSION: This study demonstrates that concomitant boost radiation therapy is tolerable, and produces a superior response rate than conventional radiation therapy for patients with inoperable NSCLC. The length of treatment was reduced from 38 to 26 treatment days, almost a 30% reduction.

Oral glutamine to alleviate radiation-induced oral mucositis: a pilot randomized trial.

PURPOSE: To evaluate the influence of oral glutamine on radiation-induced oral mucositis in the radiotherapy of head and neck cancer. METHODS AND MATERIALS: From July 1997 through June 1998, 17 patients with head and neck cancer receiving primary or adjuvant irradiation were randomized to either glutamine suspension (16 g in 240 ml normal saline) (n = 8) or placebo (normal saline) (n = 9) arm. Patients were instructed to swish the test solutions (30 ml) four times per day. All patients received half-mouth irradiation at least. Patients were treated 1.8 Gy per fraction daily, 5 days a week. We evaluated the grading of oral mucositis daily fraction at each day of treatment until 45 Gy/25 fractions. World Health Organization (WHO) step analgesic medication and body weight change were compared between the two arms. RESULTS: The duration of objective oral mucositis > or = Grade 1 (p = 0.0097), Grade 2 (p = 0.0232), and Grade 3 (p = 0.0168) was shorter in the glutamine arm. Mean maximum grade of objective oral mucositis was less severe in the glutamine arm (1.6 vs. 2.6) (p = 0.0058). Glutamine did not reduce the duration and severity of subjective oral mucositis except for duration > or = Grade 3 (p = 0.0386). In the analysis of mean maximum WHO step of analgesic medication, there was no statistical difference (p = 0.5374) between the two arms. Mean body weight change was also not significantly different (p = 0.8070). CONCLUSIONS: Oral glutamine may significantly reduce the duration and severity of objective oral mucositis during radiotherapy. It may shorten the duration of > or = Grade 3 subjective mucositis.

Postoperative radiotherapy for supratentorial malignant gliomas.

From January 1988 to December 1996, sixty-five patients with histologically confirmed supratentorial malignant gliomas were treated with postoperative radiation therapy in our department. They were subjected to this analysis according to different clinical and pathologic parameters. The overall 1-year, 2-year survival rate was 57% and 23%, respectively. With univariate analysis, age, postoperative Karnofsky performance status, duration of symptoms, multiplicity of lesions and the extent of surgery were identified as significant prognostic factors. With multivariate analysis, postoperative Karnofsky performance status and the extent of surgery continued to show independent prognostic significance on overall survival.

Radiation therapy in primary central nervous system lymphoma.

BACKGROUND: Treatment of primary central nervous system lymphoma (PCNSL) in Chinese individuals has rarely been reported. Therefore, this article presents our experience in managing PCNSL with radiotherapy. METHODS: A thorough review was made of the medical records of 13 patients diagnosed with PCNSL at Kaohsiung Chang Gung Memorial Hospital from 1988 through 1997. The clinical characteristics, treatment modalities, and results were analyzed as well. RESULTS: Thirteen patients diagnosed with PCNSL were identified, of which 10 cases originated in the brain whereas three were of spinal origin. Seven of the patients were man and six were women, with a mean age of 54.9 +/- 13.1 years (range 29 to 74 years). Diffuse large cell lymphoma (11 cases) was the most common histology. Limb weakness (11 cases) and headache (7 cases) were the most common complaints at presentation. Nine patients received radiation therapy alone and four patients received radiation therapy plus chemotherapy after surgical resection or biopsy. Follow-up computed tomography (CT) scans 3 to 4 months after the completion of radiotherapy revealed that nine patients (69%) had a complete response and four (31%) had a partial response. Local recurrence occurred in five patients (56%) treated with radiation therapy alone and in one patient (25%) treated with combined modalities. The overall actuarial survival rate was 54% at 2 years and 27% at 5 years. CONCLUSION: Results in this study indicate that the initial response to radiotherapy is satisfactory. However, a local relapse frequently occurs. Future considerations should focus on new modes of treatment, such as three-dimensional conformal radiation therapy for dose escalation or a combination of chemotherapy and radiotherapy.

Postoperative radiotherapy in early stage carcinoma of the uterine cervix: treatment results and prognostic factors.

PURPOSE: The objective was to investigate the effect of pathologic parameters and other variables on treatment outcome for patients with International Federation of Gynecology and Obstetrics (FIGO) stage IB, IIA cervical carcinoma, as well as to assess the morbidities attributable to radical surgery combined with postoperative radiotherapy. MATERIALS AND METHODS: Between January 1980 and June 1994, 179 women with FIGO stage IB, IIA carcinoma of the uterine cervix were treated with radical hysterectomy and postoperative irradiation. The median follow-up of alive patients was 6.8 years. All patients received 44-60 Gy external irradiation. One hundred fifty-nine patients received 3-10 Gy intracavitary brachytherapy. The data were analyzed for overall survival, disease-free survival, pelvic control, and treatment-related complications. RESULTS: The 5-year overall survival rate, disease-free survival rate, and pelvic control rate for the 179 patients were 72, 74, and 90%, respectively. The 5-year overall survival rate was 81% for patients without pelvic lymphadenopathy and 53% for those with pelvic lymphadenopathy (P = 0.0000). Other independent prognostic factors for overall survival included tumor differentiation and the interval between operation and initiation of radiotherapy. For the endpoint of disease-free survival, pelvic lymph node status, tumor differentiation, the duration of interruption of radiotherapy, and the interval between operation and radiotherapy were of independent prognostic significance. As pelvic control was concerned, the 5-year pelvic control rate was 90% and only the duration of interruption of radiotherapy was noted as an independent predictor of pelvic control. Distant metastases were noted in 43 patients (24%); the most common sites were lung (10%), liver (6%), and bone (6%). The overall 5-year intestinal and urinary complication-free rate was 66 and 82%, respectively. The overall incidence of grade 3 or above late rectal and urinary sequelae was 10%. For patients sustaining leg lymphedema after radiotherapy, there was higher incidence of severe leg cellulitis which warranted antibiotics treatment. CONCLUSION: These prognostic factors should be considered in patient counseling and treatment planning. Based on these factors, a more aggressive treatment to improve survival in these subsets of high-risk patients might be justified. New therapeutic regimens and modalities aimed to overcome treatment failure should be investigated.