Trismus in head and neck cancer patients treated by telecobalt and effect of early rehabilitation measures.

CONTEXT: Trismus is one of the common late side effects of radiotherapy (RT) of head and neck cancers. It occurs in about 30% of patients treated by telecobalt. It, in turn, leads to significant morbidity, including malnutrition, difficulty in speaking, and compromised oral hygiene with severe psychosocial, and economic impacts. AIMS: To determine the prevalence of trismus and its progression in patients who have received radical concurrent chemoradiation for head and neck cancer by telecobalt at our institution. To note the effect of early rehabilitative measures on the severity of trismus and to assess its impact on the quality of life (QOL). SUBJECTS AND METHODS: A total of 47 evaluable patients of head and neck cancer patients treated by telecobalt with radical intent between January 2012 and December 2013 were analyzed and baseline maximal inter-incisal opening (MIO) and MIO at the completion of RT, after 3 months, 6 months, and 1 year, after completion of RT were noted. Grading of trismus was done using Modified Common Toxicity Criteria (CTCAE Version 3.0). QOL assessment was done using European Organization for Research and Treatment of Cancer QLQ-HN35. The time when the rehabilitative measures were started were also noted. STATISTICAL ANALYSIS USED: Chi-square test with Fisher exact probability test and Students t-test. RESULTS: Radiation-induced trismus (RIT) was seen in 31.9%, 34.04%, and 38.39% of cases at 3, 6, and 12 months after completion of RT. Grade II and III trismus accounted for 17.02% and 6.38% at the end of 1 year. Patients who started regular rehabilitative exercises soon, after completion of RT had a better mean MIO as compared to those who were not compliant (32 mm vs. 24 mm at 1 year), and there was a trend toward delayed progression in them. Trismus was also seen to adversely affect QOL of the patients. CONCLUSIONS: RIT is a major cause for late morbidity in patients treated with conventional RT leading to poor QOL. Early rehabilitative measures are useful in preventing progression of trismus.

Monte Carlo Dosimetry of the 60Co BEBIG High Dose Rate for Brachytherapy.

INTRODUCTION: The use of high-dose-rate brachytherapy is currently a widespread practice worldwide. The most common isotope source is 192Ir, but 60Co is also becoming available for HDR. One of main advantages of 60Co compared to 192Ir is the economic and practical benefit because of its longer half-live, which is 5.27 years. Recently, Eckert & Ziegler BEBIG, Germany, introduced a new afterloading brachytherapy machine (MultiSource®); it has the option to use either the 60Co or 192Ir HDR source. The source for the Monte Carlo calculations is the new 60Co source (model Co0.A86), which is referred to as the new BEBIG 60Co HDR source and is a modified version of the 60Co source (model GK60M21), which is also from BEBIG. OBJECTIVE AND METHODS: The purpose of this work is to obtain the dosimetry parameters in accordance with the AAPM TG-43U1 formalism with Monte Carlo calculations regarding the BEBIG 60Co high-dose-rate brachytherapy to investigate the required treatment-planning parameters. The geometric design and material details of the source was provided by the manufacturer and was used to define the Monte Carlo geometry. To validate the source geometry, a few dosimetry parameters had to be calculated according to the AAPM TG-43U1 formalism. The dosimetry studies included the calculation of the air kerma strength Sk, collision kerma in water along the transverse axis with an unbounded phantom, dose rate constant and radial dose function. The Monte Carlo code system that was used was EGSnrc with a new cavity code, which is a part of EGS++ that allows calculating the radial dose function around the source. The spectrum to simulate 60Co was composed of two photon energies, 1.17 and 1.33 MeV. Only the gamma part of the spectrum was used; the contribution of the electrons to the dose is negligible because of the full absorption by the stainless-steel wall around the metallic 60Co. The XCOM photon cross-section library was used in subsequent simulations, and the photoelectric effect, pair production, Rayleigh scattering and bound Compton scattering were included in the simulation. Variance reduction techniques were used to speed up the calculation and to considerably reduce the computer time. The cut-off energy was 10 keV for electrons and photons. To obtain the dose rate distributions of the source in an unbounded liquid water phantom, the source was immersed at the center of a cube phantom of 100 cm3. The liquid water density was 0.998 g/cm3, and photon histories of up to 1010 were used to obtain the results with a standard deviation of less than 0.5% (k = 1). The obtained dose rate constant for the BEBIG 60Co source was 1.108±0.001 cGyh-1U-1, which is consistent with the values in the literature. The radial dose functions were compared with the values of the consensus data set in the literature, and they are consistent with the published data for this energy range.

Technical note: EGSnrc-based dosimetric study of the BEBIG 60Co HDR brachytherapy sources.

PURPOSE: The purpose of this work is to calculate two-dimensional (2D) dose rate distributions around the BEBIG (Eckert & Ziegler, BEBIG GmbH, Germany) models GK60M21 (old) and Co0.A86 (new) 60Co high dose rate brachytherapy sources in an unbounded liquid water phantom. The study includes calculation of absorbed dose to water-kerma ratio D/K around the BEBIG sources and a 60Co point source in water. A comparison is made with previously published data. METHODS: The EGSnrcMP Monte Carlo code system is used to calculate the absorbed dose and water-kerma in water and air-kerma strength in vacuum. EGSnrcMP-based user codes such as EDKnrc, FLURZnrc, and DOSRZnrc are employed in the work. RESULTS: The value of D/K reaches a maximum of 1.040 +/- 0.002 for the 60Co point source (constant between 3.6 and 4.5 mm from the source) and 1.076 +/- 0.002 for the BEBIG sources (constant between 2.6 and 3.2 mm along the transverse axis of the sources). Dose rate data for the new and old sources are comparable to published data for radial distances r > 0.5 cm. Differences up to 9% are observed at points close to the source (r = 0.25 cm). In addition for the new source, compared to previously published data, dose rate data are higher by 14% along the longitudinal axis where the source cable is connected. Dose rate differences on the longitudinal axis (8 = 180 degrees) of this source are explained by varying the length of the simulated source cable. CONCLUSIONS: The 2D rectangular data set calculated in the present work could be considered for quality control on radiotherapy treatment planning systems.

Radiation therapy for incompletely excised grade II canine mast cell tumors.

Forty-five dogs with incompletely excised grade II mast cell tumors were treated with radiation using a cobalt 60 teletherapy unit (15 fractions of 3.2 Gy for a total of 48 Gy). Twenty-four of the dogs underwent prophylactic regional lymph node irradiation. Three (6.7%) dogs had tumor recurrence, two (4.4%) dogs developed metastasis, and 14 (31%) dogs developed a second cutaneous mast cell tumor. No difference in overall survival rate was observed between the dogs receiving and not receiving prophylactic irradiation of the regional lymph node.

Preoperative cobalt60 irradiation delays the healing of rectal anastomoses in rats.

The healing of colorectal anastomoses after irradiation therapy continues to be a major concern. The authors evaluated the healing of rectal anastomoses in a rat model after a preoperative 500-cGy dose of cobalt60 irradiation. Thirty-six male Wistar rats were divided into two equal groups: control (group A), and irradiation group (group B). Group B received a single 500-cGy dose of irradiation, and a rectal resection and end-to-end anastomosis was performed in both groups on the 7th day after irradiation. Parameters of the healing process included bursting pressure and collagen content on the 5th, 7th, and 14th days after surgery. In the irradiation group, the mean bursting pressure on the 5th, 7th, and 14th days was 116, 218, and 273 mmHg, respectively. The collagen content assessed by histomorphometry was 9.0, 20.8, and 32%, respectively. In contrast, the control group had a mean bursting pressure of 175, 225 and 263 mmHg, and a collagen content of 17.8, 28.1, and 32.1%, respectively. The adverse effect of irradiation on healing was detectable only on the 5th postoperative day, as demonstrated by lower bursting pressure (P < 0.013) and collagen content (P < 0.008). However, there was no failure of anastomotic healing such as leakage or dehiscence due to irradiation. We conclude that a single preoperative 500-cGy dose of irradiation delays the healing of rectal anastomosis in rats.

Preoperative cobalt60 irradiation delays the healing of rectal anastomoses in rats

The healing of colorectal anastomoses after irradiation therapy continues to be a major concern. The authors evaluated the healing of rectal anastomoses in a rat model after a preoperative 500-cGy dose of cobalt60 irradiation. Thirty-six male Wistar rats were divided into two equal groups: control (group A), and irradiation group (group B). Group B received a single 500-cGy dose of irradiation, and a rectal resection and end-to-end anastomosis was performed in both groups on the 7th day after irradiation. Parameters of the healing process included bursting pressure and collagen content on the 5th, 7th, and 14th days after surgery. In the irradiation group, the mean bursting pressure on the 5th, 7th, and 14th days was 116, 218, and 273 mmHg, respectively. The collagen content assessed by histomorphometry was 9.0, 20.8, and 32 percent, respectively. In contrast, the control group had a mean bursting pressure of 175, 225 and 263 mmHg, and a collagen content of 17.8, 28.1, and 32.1 percent, respectively. The adverse effect of irradiation on healing was detectable only on the 5th postoperative day, as demonstrated by lower bursting pressure (P < 0.013) and collagen content (P < 0.008). However, there was no failure of anastomotic healing such as leakage or dehiscence due to irradiation. We conclude that a single preoperative 500-cGy dose of irradiation delays the healing of rectal anastomosis in rats.