<p>Background: This is a retrospective study of patients treated with stereotactic body radiation therapy (SBRT) with the stereotactic body frame for centrally located lung tumours. The purpose was to investigate the doses to the different structures of the tracheobronchial tree and to relate these doses to the incidence of atelectasis. The goal was to estimate a tolerance dose for the bronchi. Materials: The patient material consisted of 71 patient treated at the Karolinska University Hospital for a total of 102 tumours between November 1993 and March 2004. The patient group consisted of 36 men and 35 women with a mean age at the treatment of 67 years (range 34-87). The group was a mixture of patients with primary lung cancer and pulmonary metastases. Methods: After rereading and reactivating the dose plans for the patients in the treatment planning system (TPS) the different tracheobronchial structures (trachea, right mainstem bronchus, right superior bronchus, right intermedius bronchus, right medius bronchus, right inferior bronchus, left mainstem bronchus, left superior bronchus, left intermedius bronchus, left inferior bronchus) were outlined. The dose distribution in each structure was calculated and a dose-volume histogram (DVH) was created. Patients were allocated to four groups, i.e. patients with right sided tumours (22), left sided tumours (14), mediastinal tumours (23) and bilateral tumours (10). After that the maximum and mean doses to all structures were analysed. An oncologist reviewed the medical records for the patients and especially looked for atelectasis. The doses were related to the incidence of atelectasis.</p><p>Results and Conclusions: For the patient group with right sided tumours it seems like the maximum doses to the bronchi are higher for the patients with atelectasis in comparison with patients without atelectasis. A better correlation between atelectasis and maximum doses rather than mean doses was observed for these patients. At this moment the results are too preliminary, so it is not possible to suggest a tolerance dose for the bronchi. What can be said is that the maximum doses to the bronchi for patients with right sided tumours without atelectasis are below 250 Gy3 expressed in biologically equivalent dose (BED) with α/β=3Gy, while at least one bronchi structure in the atelectasis patients received a maximum dose above 250 Gy3.</p>

<p>Background: Stereotactic body radiation therapy (SBRT) is a relatively new method which has been employed e.g. in the treatment of liver tumours. Little dosimetric data has been published for SBRT in the liver. The aim of this retrospective study was to quantify the dosimetric parameters that influence the toxicity of the healthy liver, and the effect on the tumour, for SBRT to liver tumours in patients treated at Karolinska University Hospital. A comparison was made to relating published studies.</p><p>Patients and Methods: The patient group to be studied were treated at Karolinska University Hospital for liver metastases with SBRT between July 1993 and October 2004. There were 64 patients treated with 71 treatment plans for 81 tumours. Differential dose volume histograms were collected for the clinical target volume (CTV), the planning target volume (PTV) and the liver excluding the CTV, from all dose plans. Since different fractionation schedules were used, the doses were normalised using the linear quadratic model, to be comparable. The doses to the uninvolved liver were evaluated with the mean liver dose, the Lyman-Kutcher-Burman (LKB) effective volume normal tissue complication probability (NTCP) model as well as the critical volume NTCP-model. A comparison was made to the studies of Dawson et al (2002) and Schefter et al (2005). The doses to the CTV were evaluated using the equivalent uniform dose tumour control probability (TCP) model, and related to target size and date of treatment.</p><p>Results: When the mean doses to the uninvolved liver (the liver volume without tumour tissue) were compared to Dawson and Ten Haken’s results (2005), 20 treatments out of 71 were predicted to give a risk of radiation induced liver disease (RILD) higher than 50%. The effective volume calculations predicted that 18 treatments gave a risk of RILD higher than 50%, when compared to the results of Dawson et al (2002). According to the critical volume model and the parameter values of Schefter et al (2005), our data predict that 10 of the treatments gave a risk of liver function failure, to an unspecified risk level. Treatments of large tumours resulted in higher doses to the liver. The doses to the CTV showed that the maximum prescribed dose decreased with increasing CTV.</p><p>Discussion and Conclusions: An evaluation of clinical data is necessary to make a full analysis of the treatments of this study. Such an analysis is planned for the future.</p>

Background: This is a retrospective study of patients treated with stereotactic body radiation therapy (SBRT) with the stereotactic body frame for centrally located lung tumours. The purpose was to investigate the doses to the different structures of the tracheobronchial tree and to relate these doses to the incidence of atelectasis. The goal was to estimate a tolerance dose for the bronchi. Materials: The patient material consisted of 71 patient treated at the Karolinska University Hospital for a total of 102 tumours between November 1993 and March 2004. The patient group consisted of 36 men and 35 women with a mean age at the treatment of 67 years (range 34-87). The group was a mixture of patients with primary lung cancer and pulmonary metastases. Methods: After rereading and reactivating the dose plans for the patients in the treatment planning system (TPS) the different tracheobronchial structures (trachea, right mainstem bronchus, right superior bronchus, right intermedius bronchus, right medius bronchus, right inferior bronchus, left mainstem bronchus, left superior bronchus, left intermedius bronchus, left inferior bronchus) were outlined. The dose distribution in each structure was calculated and a dose-volume histogram (DVH) was created. Patients were allocated to four groups, i.e. patients with right sided tumours (22), left sided tumours (14), mediastinal tumours (23) and bilateral tumours (10). After that the maximum and mean doses to all structures were analysed. An oncologist reviewed the medical records for the patients and especially looked for atelectasis. The doses were related to the incidence of atelectasis. Results and Conclusions: For the patient group with right sided tumours it seems like the maximum doses to the bronchi are higher for the patients with atelectasis in comparison with patients without atelectasis. A better correlation between atelectasis and maximum doses rather than mean doses was observed for these patients. At this moment the results are too preliminary, so it is not possible to suggest a tolerance dose for the bronchi. What can be said is that the maximum doses to the bronchi for patients with right sided tumours without atelectasis are below 250 Gy3 expressed in biologically equivalent dose (BED) with α/β=3Gy, while at least one bronchi structure in the atelectasis patients received a maximum dose above 250 Gy3.

Background: Stereotactic body radiation therapy (SBRT) is a relatively new method which has been employed e.g. in the treatment of liver tumours. Little dosimetric data has been published for SBRT in the liver. The aim of this retrospective study was to quantify the dosimetric parameters that influence the toxicity of the healthy liver, and the effect on the tumour, for SBRT to liver tumours in patients treated at Karolinska University Hospital. A comparison was made to relating published studies. Patients and Methods: The patient group to be studied were treated at Karolinska University Hospital for liver metastases with SBRT between July 1993 and October 2004. There were 64 patients treated with 71 treatment plans for 81 tumours. Differential dose volume histograms were collected for the clinical target volume (CTV), the planning target volume (PTV) and the liver excluding the CTV, from all dose plans. Since different fractionation schedules were used, the doses were normalised using the linear quadratic model, to be comparable. The doses to the uninvolved liver were evaluated with the mean liver dose, the Lyman-Kutcher-Burman (LKB) effective volume normal tissue complication probability (NTCP) model as well as the critical volume NTCP-model. A comparison was made to the studies of Dawson et al (2002) and Schefter et al (2005). The doses to the CTV were evaluated using the equivalent uniform dose tumour control probability (TCP) model, and related to target size and date of treatment. Results: When the mean doses to the uninvolved liver (the liver volume without tumour tissue) were compared to Dawson and Ten Haken’s results (2005), 20 treatments out of 71 were predicted to give a risk of radiation induced liver disease (RILD) higher than 50%. The effective volume calculations predicted that 18 treatments gave a risk of RILD higher than 50%, when compared to the results of Dawson et al (2002). According to the critical volume model and the parameter values of Schefter et al (2005), our data predict that 10 of the treatments gave a risk of liver function failure, to an unspecified risk level. Treatments of large tumours resulted in higher doses to the liver. The doses to the CTV showed that the maximum prescribed dose decreased with increasing CTV. Discussion and Conclusions: An evaluation of clinical data is necessary to make a full analysis of the treatments of this study. Such an analysis is planned for the future.