Christian Harder

RATIONALE FOR USING INVASIVE THERMOMETRY FOR REGIONAL HYPERTHERMIA OF PELVIC TUMORS

PURPOSE Invasive thermometry for regional hyperthermia is time-consuming, uncomfortable, and risky for the patient. We tried to estimate the benefit/cost ratio of invasive thermometry in regional hyperthermia using the radiofrequency system BSD-2000. METHODS AND MATERIALS We evaluated 182 patients with locally advanced pelvic tumors that underwent regional hyperthermia. In every patient a tumor-related temperature measurement point was obtained either by invasive or minimally invasive catheter measurement tracks. In the earlier period for every patient an intratumoral measurement point was decided as obligatory and intratumoral catheters were implanted intraoperatively, CT guided, or under fluoroscopy. In the later period, invasive thermometry often was avoided, if a measurement point in or near the tumor was reached by an endoluminally inserted catheter (rectal, vaginal, cervical, urethral, or vesical). For every patient side effects and complications referred to thermometry were evaluated and compared with the potential benefit of the invasively achieved temperature data. The suitability of endolumimally registered temperatures is analyzed to estimate local feasibility (specific absorption rate achieved) and local effectiveness (thermal parameters correlated with response). RESULTS In 74 of 182 patients invasive thermometry was performed, at most CT-guided for soft tissue sarcomas and rectal recurrences. In 14 of 74 (19%) side effects such as local inflammation, pain, or abscess formation occurred that enforced removal of the catheter. However, local problems were strongly correlated with the dwell time of the catheter and nearly never occurred for dwell times less than 5 days. Fortunately, no fatal complications (e.g., bleeding or perforation) occurred during or after implantation which could be attributed to the invasive thermometry procedure. Endoluminal tumor-related temperature rises per time unit (to estimate power density) were correlated with intratumoral rises at the same patients (where both measurements were available). For a subgroup of patients pooled in two Phase II studies with rectal (n = 37) and cervical (n = 18) carcinomas thermal parameters derived from endoluminal measurements were correlated with response or local control, resp. CONCLUSIONS If a tumor-related endoluminal temperature measurement point is available, additional invasive thermometry gives no further information to improve the power deposition pattern. For primary rectal and cervical cancer, and probably as well for prostate, bladder and anal cancer, endoluminal measurements are suitable to estimate local feasibility and effectiveness. Therefore, invasive thermometry is dispensable in the majority of patients. In some selected cases, temperature measurement in the tumor center is required to estimate the maximum temperature. In those cases, dwell time of catheters should be minimized--and it should be considered to perform invasive thermometry at the beginning (one or two heat treatments).

Temperature data and specific absorption rates in pelvic tumours: predictive factors and correlations

The system BSD 2000 has been in clinical use for regional hyperthermia for more than 10 years. Several technical details of this hyperthermia system, as well as the results of clinical studies employing this system have been investigated. The intention of this paper is to investigate the correlation between technical efficiency or feasibility of hyperthermia with the BSD 2000, in terms of power densities and temperatures depending upon parameters such as tumour histology, tumour location, patient age, patient sex, and patient cross section. The possible conclusions of predictive factors derived from the above correlations were closely scrutinized. Data acquired from 772 treatment sessions of 190 patients with pelvic tumours, mainly sarcomas and carcinomas of the rectum, cervix, prostate and anus, have been evaluated. For every session, index temperatures T90 (temperature attained at 90% of tumour related measurement points), cumulative minutes for T90 > Tref, tumour related power density (SAR: specific absorption rate, in W/kg) and the effective perfusion Weff (in ml/100 g min) were calculated. Temperatures were measured either invasively or endoluminally. The statistics software SPSS was employed subsequently for univariate, as well as multivariate analyses. The results exhibit that index temperatures mainly depend on the power density SAR and the hyperthermia induced effective perfusion. The total power P (in 100 W) and, complementarily, the relative power density absolute value(SAR) (= SAR/P) seem to have lesser influence. Clear differences between the tumour entities were established regarding their index temperatures and temperature distributions. SAR, Weff and P were correlated with several anatomical, biological and clinical factors. Sessions rendering low index temperatures and SAR values also revealed decreased individual tolerance to the treatment. This clearly displays that power-induced side effects define the limits of the efficiency of regional hyperthermia. Equivalent relationships and correlations are derived from intratumoural and endoluminal thermometry. Individual limitations of regional hyperthermia caused by anatomical, biological and clinical factors are liable to be difficult to overcome with the rather restricted potentials of the BSD 2000 system to control the SAR distribution.The system BSD 2000 has been in clinical use for regional hyperthermia for more than 10 years. Several technical details of this hyperthermia system, as well as the results of clinical studies employing this system have been investigated. The intention of this paper is to investigate the correlation between technical efficiency or feasibility of hyperthermia with the BSD 2000, in terms of power densities and temperatures depending upon parameters such as tumour histology, tumour location, patient age, patient sex, and patient cross section. The possible conclusions of predictive factors derived from the above correlations were closely scrutinized. Data acquired from 772 treatment sessions of 190 patients with pelvic tumours, mainly sarcomas and carcinomas of the rectum, cervix, prostate and anus, have been evaluated. For every session, index temperatures T 90 (temperature attained at 90% of tumour related measurement points), cumulative minutes for T90 > Tref, tumour related power density (SAR: specific absorption rate, in W/kg) and the effective perfusion Weff (inml/100gmin) were calculated. Temperatures were measured either invasively or endoluminally. The statistics software SPSS was employed subsequently for univariate, as well as multivariate analyses. The results exhibit that index temperatures mainly depend on the power density SAR and the hyperthermia induced effective perfusion. The total power P (in 100W) and, complementarily, the relative power density ||SAR|| (= SAR/P) seem to have lesser influence. Clear differences between the tumour entities were established regarding their index temperatures and temperature distributions. SAR, Weff and P were correlated with several anatomical, biological and clinical factors. Sessions rendering low index temperatures and SAR values also revealed decreased individual tolerance to the treatment. This clearly displays that powerinduced side effects define the limits of the efficiency of regional hyperthermia. Equivalent relationships and correlations are derived from intratumoural and endoluminal thermometry. Individual limitations of regional hyperthermia caused by anatomical, biological and clinical factors are liable to be difficult to overcome with the rather restricted potentials of the BSD 2000 system to control the SAR distribution.

Vergleich unterschiedlicher dreidimensionaler Bestrahlungstechniken bei der lokalen Strahlentherapie des Prostatakarzinoms

ZielVier verschiedene SD-Bestrahlungstechniken wurden hinsichtlich der Dosishomogenität im Targetvolumen und der Dosis-Volumen-Belastung der Risikoorgane in AbhÄngigkeit vom Tumorstadium untersucht.Patienten und MethodeBei 17 Patienten wurden eine 3D-Rotations-, Vier-Felder-, Fünf-Felder- und Sechs-Felder-Technik erstellt. Sechs Patienten wiesen ein Stadium T1N0M0, sieben Patienten ein Stadium T2N0M0 und vier Patienten ein Stadium T3N0M0 auf. Dosiert wurde auf den Referenzpunkt im Isozentrum (100%). Die 95%-Isodose mu\te das Planungszielvolumen umschlie\en. Es wurden bei allen Techniken Multileaf-Kollimatoren verwendet und Dosis-Volumen-Histogramme für das Planungszielvolumen und die Risikoorgane (Blase, Rektum, Hüftköpfe) erstellt und miteinander verglichen. Der Vergleich erfolgte jeweils bei 33%, 50% und 66% Volumen des jeweiligen Risikoorgans.ErgebnisseHinsichtlich der Dosishomogenität im Targetvolumen zeigte sich kein Unterschied. Eine signifikante Differenz wurde bei der Blasenbelastung zwischen der Sechs-Felder- und der Vier-Felder-Technik nur bei 50% Volumenanteil (p = 0,034), zwischen Sechs-Felder- und Rotationstechnik sowie zwischen Fünf-Felder- und Rotationstechnik bei allen Volumenanteilen gesehen. Bei der Belastung des Rektums ergab sich eine signifikante Differenz zwischen der Sechs- und der Vier-Felder-Technik bei T1- und T2-Tumoren sowohl bei 50% (p = 0,033) als auch bei 66% (p = 0,011). Bei den T3-Tumoren ergaben sich hinsichtlich der Rektumbelastung keine signifikanten Unterschiede. Die beste Schonung der Hüftköpfe wurde durch die Rotationstechnik erzielt.Schlu\folgerungBei der kleinvolumigen Bestrahlung der Prostata ist bei T1/2-Tumoren durch die Sechs-Felder-Technik die beste Schonung von Rektum und Blase zu erzielen, bei grö\erem Planungszielvolumen und bei Einschlu\ der SamenblÄschen sollten andere Techniken, wie zum Beispiel eine dreidimensional geplante Vier-Felder-Technik, zur besseren Schonung der Risikoorgane angewendet werden.AbstractPurposeFour different three-dimensional planning techniques for localized radiotherapy of prostate cancer were compared with regard to dose homogeneity within the target volume and dose to organs at risk, dependent upon tumor stage.Patients and MethodsSix patients with stage T1, 7 patients with stage T2 and 4 patients with stage T3 were included in this study. Four different 3D treatment plans (rotation, 4-field, 5-field and 6-field technique) were calculated for each patient. Dose was calculated with the reference point at the isocenter (100%). The planning target volume was encompassed within the 95% isodose surface. All the techniques used different shaped portal for each beam. Dose volume histograms were created and compared for the planning target volume and the organs at risk (33%, 50%, 66% volume level) in all techniques.ResultsThe 4 different three-dimensional planning techniques revealed no differences concerning dose homogeneity within the planning target volume. The dose volume distribution at organs at risk show differences between the calculated techniques. In our study the best protection for bladder and rectum in stage T1 and T2 was achieved by the 6-field technique. A significant difference was achieved between 6-field and 4-field technique only in the 50% volume of the bladder (p = 0.034), between the 6-field and rotation technique (all volume levels) and between 5-field and rotation technique (all volume levels). In stage T1, T2 6-field and 4-field technique in 50% (p = 0.033) and 66% (p = 0.011) of the rectum volume. In stage T3 a significant difference was not observed between the 4 techniques. The best protection of head of the femur was achieved by the rotation technique.ConclusionIn the localized radiotherapy of prostate cancer in stage T1 or T2 the best protection for bladder and rectum was achieved by a 3D-planned conformai 6-field technique. If the seminal vesicles have been included in the target volume and in the case of large planning target volume other techniques should be taken for a better protection for organs at risk e. g. a 3D-planned 4-field technique box technique.PURPOSE Four different three-dimensional planning techniques for localized radiotherapy of prostate cancer were compared with regard to dose homogeneity within the target volume and dose to organs at risk, dependent upon tumor stage. PATIENTS AND METHODS Six patients with stage T1, 7 patients with stage T2 and 4 patients with stage T3 were included in this study. Four different 3D treatment plans (rotation, 4-field, 5-field and 6-field technique) were calculated for each patient. Dose was calculated with the reference point at the isocenter (100%). The planning target volume was encompassed within the 95% isodose surface. All the techniques used different shaped portal for each beam. Dose volume histograms were created and compared for the planning target volume and the organs at risk (33%, 50%, 66% volume level) in all techniques. RESULTS The 4 different three-dimensional planning techniques revealed no differences concerning dose homogeneity within the planning target volume. The dose volume distribution at organs at risk show differences between the calculated techniques. In our study the best protection for bladder and rectum in stage T1 and T2 was achieved by the 6-field technique. A significant difference was achieved between 6-field and 4-field technique only in the 50% volume of the bladder (p = 0.034), between the 6-field and rotation technique (all volume levels) and between 5-field and rotation technique (all volume levels). In stage T1, T2 6-field and 4-field technique in 50% (p = 0.033) and 66% (p = 0.011) of the rectum volume. In stage T3 a significant difference was not observed between the 4 techniques. The best protection of head of the femur was achieved by the rotation technique. CONCLUSION In the localized radiotherapy of prostate cancer in stage T1 or T2 the best protection for bladder and rectum was achieved by a 3D-planned conformal 6-field technique. If the seminal vesicles have been included in the target volume and in the case of large planning target volume other techniques should be taken for a better protection for organs at risk e. g. a 3D-planned 4-field technique box technique.

Virtuelle Simulation@@@Virtual simulation — First clinical results in patients with prostate cancer: Erste klinische Ergebnisse bei Patienten mit Prostatakarzinom

AIM Investigation of options of virtual simulation in patients with localized prostate cancer. PATIENTS AND METHODS Twenty-four patients suffering from prostate cancer were virtual simulated. The clinical target volume was contoured and the planning target volume was defined after CT scan. The isocenter of the planning target volume was determined and marked at patients skin. The precision of patients marking was controlled with conventional simulation after physical radiation treatment planning. RESULTS Mean differences of the patients mark revealed between the 2 simulations in all room axes around 1 mm. The organs at risk were visualized in the digital reconstructed radiographs. CONCLUSIONS The precise patients mark of the isocentre by virtual simulation allows to skip the conventional simulation. The visualisation of organs at risk leeds to an unnecessarily of an application of contrast medium and to a further relieve of the patient. The personal requirement is not higher in virtual simulation than in conventional CT based radiation treatment planning.ZusammenfassungZielUntersuchung von Optionen der virtuellen Simulation bei Patienten mit lokal begrenztem Prostatakarzinom.Patienten und Methode24 Patienten mit einem lokal begrenzten Prostatakarzinom wurden virtuell simuliert. Nach dem Bestrahlungsplanungs-CT erfolgte die Konturierung des Klinischen Zielvolumens und des Planungszielvolumens sowie die Bestimmung des geometrischen Isozentrums, das auf der Haut markiert wurde. Nach Erstellung des Bestrahlungsplanes wurde die Genauigkeit der Markierung des Isozentrums am konventionellen Simulator überprüft.ErgebnisseDie Markierung des Isozentrums an den Patienten erfolgte mit einer mittleren Abweichung von 1 mm in allen drei Ebenen. Auf den digital rekonstruierten Simulationsaufnahmen werden alle vorher konturierten Strukturen wie Zielvolumina und Risikoorgane dargestellt.SchlußfolgerungenAufgrund der Präzision der Markierung des Isozentrums kann bei Einsatz der virtuellen Simulation bei Patienten mit einem lokal begrenzten Prostatakarzinom auf die konventionelle Simulation verzichtet werden. Die Darstellung der Risikoorgane in den digital rekonstruierten Simulationsaufnahmen ermöglicht den Verzicht auf die Kontrastmittelapplikation bei der Simulation und führt zu einer weiteren Entlastung für den Patienten. Der personelle Aufwand ist im Vergleich zur konventionellen CT-gestützten Bestrahlungsplanung nicht höher.AbstractAimInvestigation of options of virtual simulation in patients with localized prostate cancer.Patients and MethodsTwenty-four patients suffering from prostate cancer were virtual simulated. The clinical target volume was contoured and the planning target volume was defined after CT scan. The isocenter of the planning target volume was determined and marked at patient’s skin. The precision of patients marking was controlled with conventional simulation after physical radiation treatment planning.ResultsMean differences of the patient’s mark revealed between the 2 simulations in all room axes around 1 mm. The organs at risk were visualized in the digital reconstructed radiographs.ConclusionThe precise patient’s mark of the isocentre by virtual simulation allows to skip the conventional simulation. The visualisation of organs at risk leeds to an unnecessarity of an application of contrast medium and to a further relieve of the patient. The personal requirement is not higher in virtual simulation than in conventional CT based radiation treatment planning.