Postoperative radiotherapy in DBCG during 30 years. Techniques, indications and clinical radiobiological experience.

During the time period 1977-2007 postoperative radiotherapy in DBCG has varied considerably with regard to techniques and indications together with changes in the extent of surgery and adjuvant systemic therapy. The radiation treatment has been developed on the basis of clinical, radiophysical and radiobiological principles, encompassing also practical problems such as available equipment in the different centres and at times lack of sufficient machine capacity. The paper focus especially on the comprehensive work done prior to the DBCG 82 b&c studies, in order to optimize radiotherapy in all aspects prior to the evaluation of the efficacy of this treatment modality. The results from these trials did succeed in clear evidence that radiotherapy has an important role in the multidisciplinary treatment of early breast cancer. In parallel to these studies a new and challenging use of radiotherapy after breast conserving surgery was evaluated in the DBCG TM 82 protocol. The experience obtained with different techniques in this study formed the basis for the current principles of radiotherapy after lumpectomy. Reduction of radiation related morbidity has been a major issue for the DBCG radiotherapy group, and in this aspect several studies, including quality control visits, have been carried out to make the relevant modifications and to evaluate deviations from the guidelines between the centres. The background for the changes in radiotherapy is described for each of the programme periods as well as future perspectives which will include further refinements of the target and adjustments of dose and fractionation in selected patients.

Geometric stability of intracavitary pulsed dose rate brachytherapy monitored by in vivo rectal dosimetry.

BACKGROUND AND PURPOSE: To evaluate geometric stability of applicator and rectum during pulsed dose rate (PDR) intracavitary brachytherapy. PATIENTS AND METHODS: A total of 14 patients with cervical cancer (stages IIB-IVA) were analysed retrospectively. A dose of 10 Gy to point A was prescribed per brachytherapy session, and PDR was given with 1 Gy/pulse, 1 pulse/h, using a ring applicator (Varian). A rectal dosimeter consisting of five diodes spaced by 1.5 cm was routinely placed in the rectum. The diodes detected the progression of each pulse of radiation, as the stepping source was advanced through the applicator. A mathematical model has been developed for spatial analysis of the pattern of the dose readings. The model transforms dose measurement into a quantification of the geometric relationship between rectum diodes and applicator. RESULTS: The model could be used for all treatment sessions, and the relative positions of diodes and applicator were calculated for each pulse of radiation. The SD of displacements during the treatment was below 2.8mm in all directions for all patients. The mean SD in lateral, longitudinal and anterior-posterior directions were 1.2 +/- 0.7, 1.2 +/- 0.7 and 0.9 +/- 0.6 mm, respectively. The mean measurement uncertainty was below 0.8 +/- 0.5 mm in all directions. CONCLUSIONS: A new mathematical method has been developed, enabling us to quantitate and monitor relative positions of applicator and rectal diodes during a PDR treatment. The spatial relation between rectal dosimeter and applicator was very stable during extended PDR treatments suggesting that the geometric stability of PDR treatment is at the same level as the stability reported for HDR brachytherapy.

Comparison of two dose calculation methods applied to extracranial stereotactic radiotherapy treatment planning.

BACKGROUND AND PURPOSE: Lung tissue is a special challenge for a dose calculation algorithm, especially in the case of extracranial stereotactic radiotherapy (ESRT) due to small field sizes in combination with large variations in tissue density. The present study investigates the choice of dose calculation algorithm for 18 patients with a single lung tumor and 8 patients with a single liver tumor. The dose calculation is performed with both the pencil beam convolution algorithm and the collapsed cone convolution algorithm with the same number of monitor units in both cases. In addition, the dose calculation with the collapsed cone convolution algorithm is also performed with modified field sizes in order to match the Planning Target Volume (PTV) peripheral dose of the pencil beam based treatment. RESULTS: For liver tumors, the mean Clinical Target Volume (CTV) dose calculated by the collapsed cone convolution algorithm and the pencil beam convolution algorithm is almost identical. For lung tumors, the mean CTV dose determined by the collapsed cone convolution algorithm differs up to 20%. Plans obtained by the two algorithms have field sizes which differ up to 8mm for the same number of monitor units and minimum dose to the lung PTV. CONCLUSIONS: The choice of dose calculation algorithm can have a large influence on a treatment plan for ESRT of the lungs.

Audit of the radiotherapy in the DBCG 82 b&c trials--a validation study of the 1,538 patients randomised to postmastectomy radiotherapy.

INTRODUCTION: In the DBCG 82 b&c trials 3083 patients with stages II and III breast cancer were randomised to receive postmastectomy radiotherapy (RT) versus no RT in addition to systemic therapy. The study showed a decrease in loco-regional recurrences and an improved survival in patients receiving RT. The aim of the present study was to describe the delivered RT for the 1538 patients who were randomised to RT, and to evaluate the compliance with the RT guidelines. PATIENTS AND METHODS: Basic information about the given RT was recorded in the DBCG data centre. For the current study, missing and additional information was collected from individual RT treatment charts. We defined some criteria for complying with the DBCG RT guidelines regarding target coverage and dose and fractionation and based on that we also defined some criteria for having clinically acceptable RT treatments. RESULTS: Of the 1538 patients, 87% received megavoltage RT, 8% had orthovoltage RT and 5% never began or completed RT. Of the 1341 megavoltage irradiated patients, the guideline compliance regarding target coverage of the axillary/periclaviculary region, internal mammary nodes and chest wall was 88, 79 and 85%, respectively. Only 0, 0.2 and 0.4% did not have clinically acceptable target coverage. The dose and fractionation was according to the guidelines in 96% and none had clinically unacceptable dose and fractionation schedules. CONCLUSION: The guideline compliance for megavoltage RT was high with 88, 79 and 85% complying with the guidelines regarding target coverage of the axillary/periclaviculary region, internal mammary nodes and chest wall, respectively, and with 96% complying with the guidelines regarding dose and fractionation schedules. Less than 1% had clinically unacceptable target coverage and none had unacceptable dose and fractionation schedules.