Jörn Wulf

Stereotactic Radiotherapy of Targets in the Lung and Liver

Background: Stereotactic irradiation of extracranial targets offers a non-invasive treatment modality for patients with localized tumors, which are not amenable for surgery or other invasive approaches because of age or impaired medical condition. The purpose of the study was the evaluation of the method to achieve local control of irradiated targets in relation to treatment toxicity. Patients and Methods: Irradiation was performed as hyperfractionated treatment in three fractions of 10 Gy each, normalized to the PTV enclosing 65% isodose with patient fixation in a stereotactic body frame. The isocenter was localized by stereotactic coordinates. Targets were circumscribed tumors in the lung (n = 27) and liver (n = 24) not amenable for other treatment modalities: primary lung cancer (n = 12), local recurrences of lung cancer (n = 4), lung metastases (n = 11), liver metastases (n = 23) and one cholangiocellular carcinoma. Median CTV/PTV for targets in the lung was 57/113 cm3 (min/max 5–277 cm3/17–343 cm3) and for targets in the liver 50/102 cm3 (min/max 9–516 cm3/42–772 cm3). Median follow-up for targets in the lung was 8 months (2–33) and 9 months (2–28) for liver targets. Local control was defined as complete or partial remission and stable disease, measured by repeated CT scans after 6 weeks and in 3 months intervals. Treatment toxicity was evaluated according to the WHO score. Results: Crude local control was 85% for pulmonary targets and 83% for hepatic targets. Actuarial local control after 1 and 2 years was 76% and 76% for lung tumors and 76% and 61% for liver tumors. Actuarial overall patient survival was 48% after 1 year and 21% after 2 years for targets in the lung and 71% and 43% for targets in the liver. No acute grade 3–5 side effects were observed. Serious late toxicity occurred in two patients: a chronic ulceration of the esophagus at a target close to the mediastinum after 3 months (grade 3) and fatal bleeding from the pulmonary artery after 9 months (grade 5) in a previously irradiated patient. It remained unclear, whether the bleeding was a side effect of irradiation or due to tumor infiltration. Conclusion: Hypofractionated stereotactic irradiation of targets in the lung and liver is a locally effective treatment with actuarial local control rates of 76% after 1 year and 61–76% after 2 years without relevant acute toxicity. Severe late toxicity did not occur, if targets close to the mediastinum were avoided.Hintergrund: Prüfung eines hypofraktionierten, stereotaktischen Behandlungsansatzes für Bestrahlung lokalisierter Raumforderungen in der Lunge und Leber hinsichtlich lokaler Tumorkontrolle und Nebenwirkungen. Patienten und Methode: Stereotaktische Bestrahlung in drei Fraktionen à 10 Gy, normalisiert auf die PTV-umschließende 65%-Isodose mit Patientenfixierung im stereotaktischen Körperrahmen. Insgesamt wurden 27 Lungentumoren (zwölf primäre und vier lokoregionär rezidivierte Bronchialkarzinome, elf Metastasen) und 24 Lebertumoren (23 Metastasen, ein cholangiozelluläres Karzinom) behandelt. Das CTV/PTV für Lungenherde betrug im Median 57/113 cm3 (min/max 5–277 cm3/17–343 cm3), für Leberherde 50/102 cm3 (min/max 9–516 cm3/42–772 cm3). Die mediane Nachbeobachtungszeit betrug 8 Monate (2–33) für Lungen- und 9 Monate (2–28) für Leberherde. Lokale Kontrolle wurde definiert als computertomographisch komplette oder partielle Remission sowie Wachstumsstopp 6 Wochen sowie in Intervallen von 3 Monaten nach Therapie. Die Nebenwirkungen wurden nach WHO klassifiziert. Ergebnis: Lokale Kontrolle betrug numerisch in der Lunge 85%, in der Leber 83%, aktuarisch in der Lunge 76% nach 1 und 2 Jahren, in der Leber 76% nach 1 Jahr, 61% nach 2 Jahren. Das aktuarische Gesamtüberleben lag nach 1 und 2 Jahren bei Lungenherden bei 48% und 21% bzw. bei Leberherden bei 71% und 43%. Akut traten keine Nebenwirkungen Grad 3–5 auf. Als Spätnebenwirkung wurden eine chronische Ösophagitis (Grad 3) bei einem dicht am Mediastinum gelegenen Tumor sowie eine fatale Blutung aus der Arteria pulmonalis beobachtet, bei der jedoch auch eine tumorbedingte Arrosionsblutung nicht auszuschließen war. Schlussfolgerung: Die stereotaktische Bestrahlung von Lungen- und Leberherden ist eine effektive Bestrahlungsform mit aktuarischen lokalen Kontrollraten bis zu 76% nach 1 Jahr bzw. 61–76% nach 2 Jahren. Die Akuttoxizität war gering; schwere Spätnebenwirkungen traten nicht auf, wenn Zielvolumina in der Nähe des Mediastinums vermieden wurden.

Stereotactic radiotherapy of extracranial targets: CT-simulation and accuracy of treatment in the stereotactic body frame.

BACKGROUND AND PURPOSE Evaluation of set-up accuracy and analysis of target reproducibility in the stereotactic body frame (SBF), designed by Blomgren and Lax from Karolinska Hospital, Stockholm. Different types of targets were analyzed for the risk of target deviation. The correlation of target deviation to bony structures was analyzed to evaluate the value of bones as reference structures for isocenter verification. MATERIALS AND METHODS Thirty patients with 32 targets were treated in the SBF for primary or metastatic peripheral lung cancer, liver metastases, abdominal and pelvic tumor recurrences or bone metastases. Set-up accuracy and target mobility were evaluated by CT-simulation and port films. The contours of the target at isocenter level, bony structures and body outline were compared by matching the CT-slices for treatment planning and simulation using the stereotactic coordinates of the SBF as external reference system. The matching procedure was performed by using a 3D treatment planning program. RESULTS Set-up accuracy represented by bony structures revealed standard deviations (SD) of 3.5 mm in longitudinal, 2.2 mm in anterior-posterior and 3.9 mm in lateral directions. Target reproducibility showed a SD of 4.4 mm in longitudinal, 3.4 mm ap and 3.3 mm in lateral direction prior to correction. Correlation of target deviation to bones ranged from 33% (soft tissue targets) to 100% (bones). CONCLUSION A security margin of 5 mm for PTV definition is sufficient, if CT simulation is performed prior to each treatment to correct larger target deviations or set-up errors. Isocenter verification relative to bony structures is only safe for bony targets but not for soft tissue targets.

Impact of target reproducibility on tumor dose in stereotactic radiotherapy of targets in the lung and liver

BACKGROUND AND PURPOSE Previous analyses of target reproducibility in extracranial stereotactic radiotherapy have revealed standard security margins for planning target volume (PTV) definition of 5mm in axial and 5-10mm in longitudinal direction. In this study the reproducibility of the clinical target volume (CTV) of lung and liver tumors within the PTV over the complete course of hypofractionated treatment is evaluated. The impact of target mobility on dose to the CTV is assessed by dose-volume histograms (DVH). MATERIALS AND METHODS Twenty-two pulmonary and 21 hepatic targets were treated with three stereotactic fractions of 10 Gy to the PTV-enclosing 100%-isodose with normalization to 150% at the isocenter. A conformal dose distribution was related to the PTV, which was defined by margins of 5-10mm added to the CTV. Prior to each fraction a computed tomography (CT)-simulation over the complete target volume was performed resulting in a total of 60 CT-simulations for lung and 58 CT-simulations for hepatic targets. The CTV from each CT-simulation was segmented and matched with the CT-study used for treatment planning. A DVH of the simulated CTV was calculated for each fraction. The target coverage (TC) of dose to the simulated CTV was defined as the proportion of the CTV receiving at least the reference dose (100%). RESULTS A decrease of TC to <95% was found in 3/60 simulations (5%) of pulmonary and 7/58 simulations (12%) of hepatic targets. In two of 22 pulmonary targets (9%) and in four of 21 hepatic targets (19%) a TC of <95% occurred in at least one fraction. At risk for a decreased TC <95% were pulmonary targets with increased breathing mobility and hepatic targets with a CTV exceeding 100 cm(3). CONCLUSIONS Target reproducibility was precise within the reference isodose in 91% of lung and 81% of liver tumors with a TC of the complete CTV >or=95% at each fraction of treatment. Pulmonary targets with increased breathing mobility and liver tumors >100 cm(3) are at risk for target deviation exceeding the standard security margins for PTV-definition at least for one fraction and require individual evaluation of sufficient margins.

Extracranial stereotactic radiotherapy: Evaluation of PTV coverage and dose conformity* * This conlribution is dedicaled to Prof. Dr. Jürgen Richter on tbe occasion of his 65th birthday.

During the past few years the concept of cranial stereotactic radiotherapy has been successfully extended to extracranial tumoral targets. In our department, hypofractionated treatment of tumours in lung, liver, abdomen, and pelvis is performed in the Stereotactic Body Frame (ELEKTA Instrument AB) since 1997. We present the evaluation of 63 consecutively treated targets (22 lung, 21 liver, 20 abdomen/pelvis) in 58 patients with respect to dose coverage of the planning target volume (PTV) as well as conformity of the dose distribution. The mean PTV coverage was found to be 96.3% +/- 2.3% (lung), 95.0% +/- 4.5% (liver), and 92.1% +/- 5.2% (abdomen/pelvis). For the so-called conformation number we obtained values of 0.73 +/- 0.09 (lung), 0.77 +/- 0.10 (liver), and 0.70 +/- 0.08 (abdomen/pelvis). The results show that highly conformal treatment techniques can be applied also in extracranial stereotactic radiotherapy. This is primarily due to the relatively simple geometrical shape of most of the targets. Especially lung and liver targets turned out to be approximately spherically/cylindrically shaped, so that the dose distribution can be easily tailored by rotational fields.

3-D conformal treatment of prostate cancer to 74 Gy vs. high-dose-rate brachytherapy boost: A cross-sectional quality-of-life survey

The effects of two modalities of dose-escalated radiotherapy on health-related quality of life (HRQOL) were compared. Forty-one consecutive patients were treated with a 3-D conformal (3-DC) boost to 74 Gy, and 43 with high-dose rate (HDR) brachytherapy boost (2×9 Gy), following 3-D conformal treatment to 46 Gy. Median age was 70 years in both groups, median initial PSA was 7.9 µg/l in 3-DC boost patients and 8.1 µg/l in HDR boost patients. Stage was ≤T2 in 66% and 67% and Gleason score was ≥7 in 52% and 47%, respectively. HRQOL was assessed cross-sectionally using EORTC QLQ-C30 and organ-specific PR25 modules 3 – 32 (median 19) and 4 – 25 (median 14) months after treatment, respectively. Questionnaires were completed by 93% and 97% of patients, respectively. Diarrhea and insomnia scores were significantly increased in both groups. In the PR25 module, scores of 3-DC boost and HDR boost patients for urinary, bowel and treatment-related symptoms were similar. Among responders, 34% of 3-DC boost patients and 86% of HDR boost patients had severe erectile problems. Dose escalation in prostate cancer by either 3-DC boost to 74 Gy or HDR brachytherapy boost appears to result in similar HRQOL profiles.

Prospective evaluation of quality of life after permanent prostate brachytherapy with I-125: Importance of baseline symptoms and of prostate-V150

BACKGROUND AND PURPOSE Detailed knowledge of quality of life (QoL) after permanent I-125 brachytherapy may aid in counselling patients with early-stage prostate cancer. MATERIALS AND METHODS Seventy-four consecutive patients with low-risk prostate cancer were asked to complete the EORTC QLQ-C30 questionnaire with the prostate-specific PR25 module before implant, four weeks and one year after implant (response rates 97%, 88% and 89%, respectively). Implant characteristics were correlated with QoL scores. RESULTS Global QoL was stable from pre-treatment to one year after implant and similar to age-adjusted scores of healthy controls. Significant changes versus baseline in QLQ-C30 domains were worsened social function at four weeks, increased constipation at four weeks and at one year and improved emotional function at one year. PR25 urinary symptoms were significantly increased at four weeks and, despite some improvement, at one year; bowel symptoms were slightly increased. Both types of symptoms were most strongly related with pre-treatment symptom scores. Prostate-V150 was the only implant parameter significantly associated with both urinary and bowel symptoms at four weeks and one year. CONCLUSIONS Limiting the high-dose subvolume in the prostate may be beneficial to reduce urinary and bowel symptoms but the major determinant of symptoms after I-125 implant is the baseline symptom level.

Target motion measurement without implanted markers and its validation by comparison with manually obtained data

For an effective radiotherapy the exact tumor location must be determined. The localization has to take into account patients setup position as well as internal organ motion. Among the different localization methods, the use of a computer tomography (CT) scanner in the therapy room has been proposed recently. Achieving a CT with the patient on the therapy couch, a patients treatment position is captured. We present a method to locate tumor considering internal organ motion and displacements due to respiration. We tested the method with prostate and lung patients. The method found the most probable tumor position as well as, for high-mobility tumors located in the lung, its trajectory during the respiratory cycle. The results of this novel method were validated by comparison with manually determined target position.

Positional variability of a tandem applicator system in HDR brachytherapy for primary treatment of cervix cancer. Analysis of the anatomic pelvic position and comparison of the applicator positions during five insertions.

Purpose:Evaluation of the inter- and intraindividual applicator variability of multiple high-dose-rate (HDR) brachytherapy applications for primary treatment of cancer of the uterine cervix.Material and Methods:Retrospective analysis of 460 pairs of orthogonal X-ray films for conventional treatment in 92 patients with five intrauterine applications using an HDR tandem applicator. Measurement of the position of the applicator origin relative to a bony reference system in three dimensions. Evaluation of the differences of the applicator position in all 460 applications (interindividual variability), of the five applications in a single patient (intraindividual variability) and of the intraindividual variability relative to the applicator position at the first application.Results:The position of the applicator origin in the pelvis ranged from 23 mm cranial and 55 mm caudal to the top of femoral heads, 23 mm right and 27 mm left to the pelvic midline, and 6–53 mm dorsal to the mid of the femoral heads. Standard deviation (SD) of interindividual applicator variability was 12.9 mm (minimum/maximum –55/+23 mm, mean –13.6 mm) in longitudinal, 5.1 mm (–27/+23 mm, mean 1.6 mm) in lateral, and 7.6 mm (6/53 mm, mean 26 mm) in anterior-posterior [AP] direction. SD of intraindividual variability was 5.5 mm (–21/+23 mm, mean 0 mm) in longitudinal, 2.5 mm (–17/+19 mm, mean 0 mm) in lateral, and 4.2 mm (–15/+18 mm, mean 0 mm) in AP direction compared to intraindividual variability relative to the first insertion with an SD of 8.9 mm (–23/+36 mm, mean 2.8 mm) in longitudinal, 4.0 mm (–11/+23 mm, mean 0 mm) in lateral, and 6.8 mm (–27/+17 mm, mean –0.8 mm) in AP direction.Conclusion:Intraindividual applicator variability is significantly smaller than interindividual variability. Applicator-related procedures such as midline shielding or dose matching of tele- and brachytherapy should be performed with information on at least one individual applicator position.Ziel:Evaluation der inter- and intraindividuellen Applikatorvariabilität im Verlauf von fünf HDR-(„high-dose-rate“-)Brachytherapie-Einlagen bei der Primärbehandlung des Zervixkarzinoms.Material und Methodik:Retrospektive Analyse von 460 orthogonalen Röntgenaufnahmen zur konventionellen Bestrahlungsplanung bei 92 Patientinnen mit jeweils fünf intrauterinen Einlagen eines Ring-Stift-Applikators. Dreidimensionale Lagebestimmung des Applikatorursprungs relativ zu einem knöchernen Referenzsystem im Becken. Vergleich der Applikatorposition bei allen 460 Applikationen (interindividuelle Variabilität), der fünf Applikatorpositionen bei jeder einzelnen Patientin (intraindividuelle Variabilität) sowie der intraindividuellen Lagevariabilität relativ zur Lage bei der ersten Applikation.Ergebnisse:Die anatomische Lage des Applikatorursprungs im Becken variierte zwischen 23 mm kranial und 55 mm kaudal des Femurkopfes, 23 mm rechts und 27 mm links der Beckenmittellinie sowie 6–53 mm dorsal der Hüftkopfmitte. Die Standardabweichung (SD) der interindividuellen Applikatorvariabilität betrug 12,9 mm (Minimum/Maximum –55/+23 mm, Mittelwert [MW] –13,6 mm) in longitudinaler, 5,1 mm (–27/+23 mm, MW 1,6 mm) in lateraler und 7,6 mm (6/53 mm, MW 26 mm) in anterior-posteriorer (a.p.) Richtung. Während die SD der intraindividuellen Variabilität mit 5,5 mm (–21/+23 mm, MW 0 mm) in longitudinaler, 2,5 mm (–17/+19 mm, MW 0 mm) in lateraler und 4,2 mm (–15/+18 mm, MW 0 mm) in a. p. Richtung deutlich niedriger lag, betrug sie intraindividuell relativ zur Applikatorposition bei der ersten Einlage 8,9 mm (–23/+36 mm, MW 2,8 mm) in longitudinaler, 4 mm (–11/+23 mm, MW 0 mm) in lateraler und 6,8 mm (–27/+17 mm, MW –0,8 mm) in a. p. Richtung.Schlussfolgerung:Die intraindividuelle Lagevariabilität des Applikators ist deutlich geringer als die interindividuelle Variabilität. Daher sollten applikatorbezogene Prozeduren wie das Stellen eines Mittelblocks oder ein Matching der Dosisverteilungen aus Tele- und Brachytherapie auf Grundlage der Kenntnis zumindest einer individuellen Applikatorposition durchgeführt werden.

Outcome of Postoperative Treatment for Rectal Cancer UICC Stage II and III in Day-to-Day Clinical Practice

Background and Purpose:Radiochemotherapy (RChT) as adjuvant treatment for rectal cancer UICC stage II/III has been recommended by the National Cancer Institute (NCI) since 1991 and in Germany since 1994. Quality and results of postoperative treatment in day-to-day clinical practice in a complete region are evaluated retrospectively in a multi-institutional approach.Patients and Methods:534 patients from six institutions treated between 1993 and 1998 were evaluated. The institutions covered a complete region with radiotherapeutic care. Patients were staged as follows: UICC I 1%, II 28%, III 69%, and IV 2%. 92% received RChT, 8% radiotherapy (RT) alone. Median follow-up of patients was 47 months (17–91 months).Results:Only about 37% of expected patients were referred for postoperative treatment. The 5-year actuarial rate was as follows: local control 75% (63–84%), freedom from distant metastases 56% (44–63%), disease-free survival (DFS) 53% (42–59%), and overall survival (OS) 53% (45–64%). In multivariate analysis, local control was significantly influenced by T- and N-category, tumor grading, and RChT instead of RT alone. 6% (2–11%) of patients showed involved resection margins, in 33% of patients categorized pN0 less than the required twelve lymph nodes were examined, both leading to a significant decrease of local control.Conclusion:While the quality of adjuvant treatment followed consensus guidelines, the number of referred patients which was lower as expected and the inferior treatment results as compared to randomized studies indicate that the consensus recommendations for adjuvant treatment have not been fully accepted. Instead of patient referral according to UICC stage, patient selection by the surgeons has been performed according to individual risk factors. Efforts have to be made not only to improve treatment results in randomized studies but also to transfer and control these standards in daily practice.Hintergrund und Ziel:Die adjuvante Radiochemotherapie (RChT) des Rektumkarzinoms im UICC-Stadium II/III wird seit 1991 vom National Cancer Institute (NCI) und in Deutschland seit 1994 als Standard empfohlen. Die Qualität und Ergebnisse der postoperativen Therapie in der täglichen klinischen Praxis wurden flächendeckend retrospektiv untersucht.Patienten und Methodik:Insgesamt wurden 534 Patienten aus sechs Institutionen ausgewertet, die zwischen 1993 und 1998 behandelt wurden. Die beteiligten Kliniken versorgten strahlentherapeutisch flächendeckend den gesamten nordfränkischen Raum. Die Stadienverteilung der Patienten war: UICC I 1%, II 28%, III 69% und IV 2%. 92% erhielten eine RChT, 8% eine alleinige Strahlentherapie (RT). Die mediane Nachbeobachtungszeit der Patienten betrug 47 Monate (17–91 Monate).Ergebnisse:Nur etwa 37% der epidemiologisch erwarteten Patienten wurden entsprechend der Konsensvereinbarung einer postoperativen Therapie zugewiesen. Die Qualität der adjuvanten Therapie entsprach den gültigen Standards. Nach 5 Jahren betrugen die aktuarische lokale Kontrolle 75% (63–84%), die Freiheit von Fernmetastasen 56% (44–63%), das krankheitsfreie Überleben 53% (42–59%) und das Gesamtüberleben 53% (45–64%). Die lokale Kontrolle wurde in der multivariaten Analyse signifikant durch die pT-und pN-Kategorie, das Tumorgrading und eine RChT anstelle einer alleinigen RT beeinflusst. Bei 6% (2–11%) aller Patienten war nicht in sano (R1/2) reseziert worden; bei 33% der pN0 kategorisierten Tumoren wurden weniger als die geforderten zwölf Lymphknoten untersucht; beides führte zu einer signifikant reduzierten lokalen Kontrolle.Schlussfolgerung:Der niedrige Anteil an der adjuvanten Therapie zugewiesenen Patienten sowie die im Vergleich zu randomisierten Studien ungünstigeren Ergebnisse weisen auf die Auswahl eines Risikokollektivs hin. Anstelle einer stadienbezogenen Zuweisung scheint eine Auswahl mit individueller Risikoabschätzung durch den Chirurgen bevorzugt zu werden. Neben Therapieverbesserungen durch randomisierte Studien sollten ebenso Anstrengungen zur Übertragung dieser Ergebnisse in die flächendeckende Praxis unternommen werden.

Positional Variability of a Tandem Applicator System in HDR Brachytherapy for Primary Treatment of Cervix Cancer

Purpose:Evaluation of the inter- and intraindividual applicator variability of multiple high-dose-rate (HDR) brachytherapy applications for primary treatment of cancer of the uterine cervix.Material and Methods:Retrospective analysis of 460 pairs of orthogonal X-ray films for conventional treatment in 92 patients with five intrauterine applications using an HDR tandem applicator. Measurement of the position of the applicator origin relative to a bony reference system in three dimensions. Evaluation of the differences of the applicator position in all 460 applications (interindividual variability), of the five applications in a single patient (intraindividual variability) and of the intraindividual variability relative to the applicator position at the first application.Results:The position of the applicator origin in the pelvis ranged from 23 mm cranial and 55 mm caudal to the top of femoral heads, 23 mm right and 27 mm left to the pelvic midline, and 6–53 mm dorsal to the mid of the femoral heads. Standard deviation (SD) of interindividual applicator variability was 12.9 mm (minimum/maximum –55/+23 mm, mean –13.6 mm) in longitudinal, 5.1 mm (–27/+23 mm, mean 1.6 mm) in lateral, and 7.6 mm (6/53 mm, mean 26 mm) in anterior-posterior [AP] direction. SD of intraindividual variability was 5.5 mm (–21/+23 mm, mean 0 mm) in longitudinal, 2.5 mm (–17/+19 mm, mean 0 mm) in lateral, and 4.2 mm (–15/+18 mm, mean 0 mm) in AP direction compared to intraindividual variability relative to the first insertion with an SD of 8.9 mm (–23/+36 mm, mean 2.8 mm) in longitudinal, 4.0 mm (–11/+23 mm, mean 0 mm) in lateral, and 6.8 mm (–27/+17 mm, mean –0.8 mm) in AP direction.Conclusion:Intraindividual applicator variability is significantly smaller than interindividual variability. Applicator-related procedures such as midline shielding or dose matching of tele- and brachytherapy should be performed with information on at least one individual applicator position.Ziel:Evaluation der inter- and intraindividuellen Applikatorvariabilität im Verlauf von fünf HDR-(„high-dose-rate“-)Brachytherapie-Einlagen bei der Primärbehandlung des Zervixkarzinoms.Material und Methodik:Retrospektive Analyse von 460 orthogonalen Röntgenaufnahmen zur konventionellen Bestrahlungsplanung bei 92 Patientinnen mit jeweils fünf intrauterinen Einlagen eines Ring-Stift-Applikators. Dreidimensionale Lagebestimmung des Applikatorursprungs relativ zu einem knöchernen Referenzsystem im Becken. Vergleich der Applikatorposition bei allen 460 Applikationen (interindividuelle Variabilität), der fünf Applikatorpositionen bei jeder einzelnen Patientin (intraindividuelle Variabilität) sowie der intraindividuellen Lagevariabilität relativ zur Lage bei der ersten Applikation.Ergebnisse:Die anatomische Lage des Applikatorursprungs im Becken variierte zwischen 23 mm kranial und 55 mm kaudal des Femurkopfes, 23 mm rechts und 27 mm links der Beckenmittellinie sowie 6–53 mm dorsal der Hüftkopfmitte. Die Standardabweichung (SD) der interindividuellen Applikatorvariabilität betrug 12,9 mm (Minimum/Maximum –55/+23 mm, Mittelwert [MW] –13,6 mm) in longitudinaler, 5,1 mm (–27/+23 mm, MW 1,6 mm) in lateraler und 7,6 mm (6/53 mm, MW 26 mm) in anterior-posteriorer (a.p.) Richtung. Während die SD der intraindividuellen Variabilität mit 5,5 mm (–21/+23 mm, MW 0 mm) in longitudinaler, 2,5 mm (–17/+19 mm, MW 0 mm) in lateraler und 4,2 mm (–15/+18 mm, MW 0 mm) in a. p. Richtung deutlich niedriger lag, betrug sie intraindividuell relativ zur Applikatorposition bei der ersten Einlage 8,9 mm (–23/+36 mm, MW 2,8 mm) in longitudinaler, 4 mm (–11/+23 mm, MW 0 mm) in lateraler und 6,8 mm (–27/+17 mm, MW –0,8 mm) in a. p. Richtung.Schlussfolgerung:Die intraindividuelle Lagevariabilität des Applikators ist deutlich geringer als die interindividuelle Variabilität. Daher sollten applikatorbezogene Prozeduren wie das Stellen eines Mittelblocks oder ein Matching der Dosisverteilungen aus Tele- und Brachytherapie auf Grundlage der Kenntnis zumindest einer individuellen Applikatorposition durchgeführt werden.