High versus low dose rate intracavitary irradiation for adenocarcinoma of the uterine cervix

Monte Carlo dosimetry of the 60Co sources of a new GZP3 HDR afterloading system

BACKGROUND

The purpose of this work was to obtain the dosimetric parameters of the new GZP3 ⁶⁰Co high-dose-rate afterloading system launched by the Nuclear Power Institute of China, which is comprised of two different ⁶⁰Co sources.

METHODS

The Monte Carlo software Geant4 and EGSnrc were employed to derive accurate calculations of the dosimetric parameters of the new GZP3 ⁶⁰Co brachytherapy source in the range of 0-10 cm, following the formalism proposed by American Association of Physicists in Medicine reports TG43 and TG43U1. Results of the two Monte Carlo codes were compared to verify the accuracy of the data. The source was located in the center of a 30-cm-radius theoretical sphere water phantom.

RESULTS

For channels 1 and 2 of the new GZP3 ⁶⁰Co afterloading system, the results of the dose-rate constant (Λ) were 1.115 cGy h^-1 U^-1 and 1.112 cGy h^-1 U^-1, and for channel 3 they were 1.116 cGy h^-1 U^-1 and 1.113 cGy h^-1 U^-1 according to the Geant4 and EGSnrc, respectively. The radial dose function in the range of 0.25-10.0 cm in a longitudinal direction was calculated, and the fitting formulas for the function were obtained. The polynomial function for the radial dose function and the anisotropy function (1D and 2D) with a [Formula: see text] of 0°-175° and an r of 0.5-10.0 cm were obtained. The curves of the radial function and the anisotropy function fitted well compared with the two Monte Carlo software.

CONCLUSION

These dosimetric data sets can be used as input data for TPS calculations and quality control for the new GZP3 ⁶⁰Co afterloading system.

High dose rate versus low dose rate intracavity brachytherapy for locally advanced uterine cervix cancer

BACKGROUND

This is an updated version of the original Cochrane review published in 2010 (Issue 7).Carcinoma of the uterine cervix is the second most common cancer and the third leading cause of cancer death among women. Radiotherapy has been used successfully to treat cervical cancer for nearly a century. The combination of external beam radiotherapy (EBRT) and intracavity brachytherapy (ICBT) has become a standard treatment for cervical cancer. Whether high dose rate (HDR) or low dose rate (LDR) brachytherapy improves outcomes in terms of local control rates, survival and complications for women with cervical cancer remains controversial.

OBJECTIVES

To assess the efficacy and safety of HDR versus LDR ICBT in combination with EBRT for women with uterine cervical cancer.

SEARCH METHODS

We searched the Cochrane Gynaecological Cancer Group Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 1), MEDLINE (1966 to March 2014), EMBASE (1974 to March 2014), and the Chinese Biomedical Literature Database (CBM) (1978 to March 2014) for relevant original, published trials.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs that compared HDR with LDR ICBT, combined with EBRT, for women with locally advanced uterine cervical cancer.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data using standardised forms. Primary outcome measures included overall survival (OS), relapse-free survival (RFS) and pelvic control rate, while secondary outcomes included rates of recurrence and complications.

MAIN RESULTS

Four studies involving 1265 women met the inclusion criteria. In our meta-analysis to compare HDR and LDR ICBT, the pooled risk ratios (RRs) were 0.95 (95% confidence interval (CI) 0.79 to 1.15), 0.93 (95% CI 0.84 to 1.04) and 0.79 (95% CI 0.52 to 1.20) for 3-, 5- and 10-year overall survival rates respectively; and 0.95 (95% CI 0.84 to 1.07) and 1.02 (0.88 to 1.19) for 5- and 10-year disease-specific survival (DSS) rates respectively. The RR for RFS was 1.04 (95% CI 0.71 to 1.52) and 0.96 (95% CI 0.81 to 1.14) at 3- and 5- years. For local control rates the RR was 0.95 (95% CI 0.86 to 1.05) and 0.95 (95% CI 0.87 to 1.05) at 3- and 5- years; with a RR of 1.09 (95% CI 0.83 to 1.43) for locoregional recurrence, 0.79 (95% CI 0.40 to 1.53) for local and distant recurrence, 2.23 (95% CI 0.78 to 6.34) for para-aortic lymph node metastasis, and 0.99 (95% CI 0.72 to 1.35) for distance metastasis. For bladder, rectosigmoid and small bowel complications, the RR was 1.33 (95% CI 0.53 to 3.34), 1.00 (95% CI 0.52 to 1.91) and 3.37 (95% CI 1.06 to 10.72) respectively. These results indicated that there were no significant differences except for increased small bowel complications with HDRs (P = 0.04).

AUTHORS' CONCLUSIONS

Since the last version of this review, no new studies were identified for inclusion in this review to provide additional information. This review showed no significant differences between HDR and LDR ICBT when considering OS, DSS, RFS, local control rate, recurrence, metastasis and treatment related complications for women with cervical carcinoma. Due to some potential advantages of HDR ICBT (rigid immobilization, outpatient treatment, patient convenience, accuracy of source and applicator positioning, individualized treatment) we recommend the use of HDR ICBT for all clinical stages of cervix cancer. The overall risk of bias was high for the included studies as many of the items were either of high or unclear risk. The GRADE assessment of the quality of the evidence was low to moderate.

Dosimetric characterizations of GZP6 (60)Co high dose rate brachytherapy sources: application of superimposition method

BACKGROUND

Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications.

MATERIALS AND METHODS

MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron (60)Co and microSelectron(192)Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources.

RESULTS

The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two (60)Co sources are similar to that for the microSelectron(192)Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the (192)Ir source is less steep than both (60)Co source models. In addition, the (60)Co sources are showing more isotropic dose distribution than the (192)Ir source.

CONCLUSIONS

The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.

High dose rate versus low dose rate intracavity brachytherapy for locally advanced uterine cervix cancer

BACKGROUND

Carcinoma of the uterine cervix is the second most common cancer and the third leading cause of cancer death among women. Radiotherapy has been used successfully to treat cervical cancer for nearly a century. The combination of external beam radiotherapy (EBRT) and intracavitary brachytherapy (ICBT) has become a standard treatment modality for cervical cancer. Depending on the difference in dose rate on 'Point A' (located 2 cm above the cervical os and 2 cm lateral to the central axis of the uterus), the ICBT is divided into three modalities: low dose rate (LDR), high dose rate (HDR) and medium dose rate (MDR). Despite the practical advantages of HDR, it is necessary to investigate further the efficacy and safety of HDR brachytherapy compared to LDR brachytherapy. Questions arise as to whether HDR or LDR brachytherapy improves results for patients with cervical cancer in terms of local control rates, survival and complications related to treatment.

OBJECTIVES

To assess the efficacy and safety of HDR- versus LDR-ICBT for patients with uterine cervical cancer.

SEARCH STRATEGY

We searched the Cochrane Gynaecological Cancer Group Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 4), MEDLINE (1966 to November 2009), EMBASE (1974 to November 2009), Chinese Biomedical Literature Database (CBM) (1978 to November 2009) for relevant original, published trials.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs that compared HDR- with LDR-ICBT, combined with EBRT, for patients with locally advanced uterine cervical cancer.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data using standardised forms. Primary outcome measures included overall survival (OS), relapse-free survival (RFS) and pelvic control rate, while secondary outcomes included rates of recurrence and complications.

MAIN RESULTS

Four studies involving 1265 patients met the inclusion criteria. In our meta-analysis to compare HDR and LDR, the pooled RRs were 0.95 (95% CI 0.79 to 1.15), 0.93 (95% CI 0.84 to 1.04) and 0.79 (95% CI 0.52 to 1.20) for 3-, 5- and 10-year overall survival rates; and 0.95 (95% CI 0.84 to 1.07) and 1.02 (0.88 to 1.19) for 5- and 10-year disease-specific survival (DSS) rates. The RR for RFS was 1.04 (95% CI 0.71 to 1.52) and 0.96 (95% CI 0.81 to 1.14) at three and five years. For local control rates the RR was 0.95 (95% CI 0.86 to 1.05) and 0.95 (95% CI 0.87 to 1.05) at three and five years; with a RR of 1.09 (95% CI 0.83 to 1.43) for locoregional recurrence, 0.79 (95% CI 0.40 to 1.53) for local and distance recurrence, 2.23 (95% CI 0.78 to 6.34) for para-aortic lymph node metastasis and 0.99 (95% CI 0.72 to 1.35) for distance metastasis. For bladder, rectosigmoid and small bowel complications, the RR was 1.33 (95% CI 0.53 to 3.34), 1.00 (95% CI 0.52 to 1.91) and 3.37 (95% CI 1.06 to 10.72), respectively. These results indicate that there were no significant differences except for increased small bowel complications with HDR (P = 0.04).

AUTHORS' CONCLUSIONS

This review showed no significant differences between HDR- and LDR-ICBT when considering OS, DSS, RFS, local control rate, recurrence, metastasis and treatment related complications for women with cervical carcinoma. Due to some potential advantages of HDR-ICBT (rigid immobilization, outpatient treatment, patient convenience, accuracy of source and applicator positioning, individualized treatment) we recommend the use of HDR-ICBT for all clinical stages of cervix cancer.

Technical note: Dosimetric study of a new Co-60 source used in brachytherapy

The purpose of this study is to obtain the dosimetric parameters of a new Co-60 source used in high dose rate brachytherapy and manufactured by BEBIG (Eckert & Ziegler BEBIG GmbH, Germany). The Monte Carlo method has been used to obtain the dose rate distribution in the updated TG-43U1 formalism of the American Association of Physicists in Medicine. In addition, to aid the quality control process on treatment planning systems (TPS), a two-dimensional rectangular dose rate table, coherent with the TG-43U1 dose calculation formalism, is given. These dosimetric data sets can be used as input data of the TPS calculations and to validate them.

Current controversies in high-dose-rate versus low-dose-rate brachytherapy for cervical cancer

The use of brachytherapy in the treatment of cervical cancer has increased worldwide since its initial introduction over 100 years ago. However, certain aspects of the use of high-dose-rate (HDR) versus low-dose-rate (LDR) brachytherapy continue to be controversial, particularly the role of HDR in FIGO Stage III cervical cancer and the use of HDR with concurrent chemotherapy. This study represents a systematic literature review of prospective and retrospective series of patients with cervical carcinoma treated with external-beam radiation (EBRT) followed by either HDR or LDR radiation. The local control rates, survival rates, and treatment-related complications in patients with Stage III cervical cancer treated with HDR or LDR and those treated with concomitant chemotherapy are examined. Patients with Stage III cervical cancer treated with EBRT and brachytherapy have a local control rate of >50% in most series. Randomized prospective and retrospective studies show overall statistically equivalent local control, overall survival, and complication rates between HDR and LDR. However, LDR may be preferable for large, bulky tumors at the time of brachytherapy. Retrospective studies of HDR and concurrent chemotherapy are limited but have demonstrated toxicity rates similar to those with LDR. Selected patients with Stage III cervical carcinoma who have an adequate response to EBRT and concomitant chemotherapy may be treated with HDR brachytherapy. The existing literature shows no significant increase in complications in patients treated with HDR and concurrent chemotherapy; however, sufficient tumor shrinkage prior to HDR and careful monitoring of the dose to the normal tissues are imperative.

Monte Carlo dosimetric study of the BEBIG Co-60 HDR source

Although not as widespread as Ir-192, Co-60 is also available on afterloading equipment devoted to high dose rate brachytherapy, mainly addressed to the treatment of gynaecological lesions. The purpose of this study is to obtain the dosimetric parameters of the Co-60 source used by the BEBIG MultiSource remote afterloader (BEBIG GmbH, Germany) for which there are no dosimetric data available in the literature. The Monte Carlo code GEANT4 has been used to obtain the TG43 parameters and the 2D dose rate table in Cartesian coordinates of the BEBIG Co-60 HDR source. The dose rate constant, radial dose function and anisotropy function have been calculated and are presented in a tabular form as well as a detailed 2D dose rate table in Cartesian coordinates. These dosimetric datasets can be used as input data and to validate the treatment planning system calculations.

Monte Carlo dosimetry of 60Co HDR brachytherapy sources

Monte Carlo based dosimetry is presented for three 60Co HDR sources with a unique configuration of two active pellets in contact or spaced 9 and 11 mm apart. Results are presented in Cartesian "away and along" as well as polar coordinates following the AAPM TG-43 dosimetric formalism. Iso-dose rate contours around the sources in Cartesian coordinates reveal that significant differences between the three source designs exist only close to the source centers where dose rate distributions bear the effect of the unique source configurations. Dose rate constants of all three sources are accurately described by an equation of the form: lambda(cGyh(-1)U(-1))=lambda*pointG(1 cm,90 degrees) = 1.094*G(1 cm,90 degrees) where lambdapoint is the dose rate constant of a bare 60Co point source and G(1 cm,90 degrees) is the "exact" source geometry factor as defined by the TG-43. Radial dose and anisotropy function data extracted using the point source approximated geometry factors are tabulated for all three source designs. Finally, the dependence and variation of the above TG-43 parameters are discussed and it is demonstrated that the dosimetric properties of high-energy photon emitters are largely dependent on radionuclide source distribution.