Katalin Dérczy

Multisegmented tangential breast fields: a rational way to treat breast cancer.

Purpose:Using three-dimensional conformal radiation therapy (3D-CRT) and multisegmented conformal radiation therapy (MS-CRT) for breast cancer treatment, the dose coverage of the planning target volume (PTV) and the radiation burden on the organs at risk (OARs) were evaluated.Material and Methods:3D-CRT and MS-CRT were planned for 436 unilateral breasts (217 left). All patients were treated with MS-CRT between 2005 and 2007. For PTV delineation and beam orientation, supportive structures were applied. The mean PTV was 1,130 cm3 (in ten patients > 2,200 cm3). Three-dimensional planning with weight-optimized medial and lateral open fields at a total dose of 50.4/1.8 Gy was followed by multisegmented planning with a reasonably high-dose-level dose cloud to define the medial subfield, and renewed optimization. This was repeated for the lateral subfield with a final optimization. For PTV coverage evaluation, the ICRU 50 was considered: the PTV portions receiving 95–107%, < 95% and > 107% of the prescribed dose (PTVD95– 107%, PTVD107%), and the PTV maximal dose (PTVDmax). To compare the OAR radiation burdens, the mean doses to the ipsi-/contralateral lung, contralateral breast, and whole heart were documented.Results:The multisegmented plans furnished significantly (p < 0.0001) better target coverage (PTVD95–107% 82.8% vs. 90.9%, PTVD107% 5.9% vs. 0.3% and PTVDmax 56.6 vs. 54.3 Gy). The mean OAR doses remained almost unchanged: ipsilateral lung 10.5 versus 10.4 Gy, contralateral lung 0.4 versus 0.4 Gy, contralateral breast 0.8 versus 0.8 Gy, and whole heart (for left-sided cancers) 4.8 versus 4.8 Gy. The subfields required a mean of 9.8 MU (monitor units), i.e., a mean total 7.6 MU increment. The planning took 10–20 min, and the delivery 5–10 min.Conclusion:MS-CRT is a good alternative to breast intensity-modulated radiation therapy (IMRT) and seems adequate for right-sided cancers, whereas left-sided cancers necessitate a longer follow-up of heart-related side effects before a final assessment.Ziel:Die Erfassung des Planungszielvolumens (PTV) und die Strahlenbelastung der Risikoorgane (OARs) bei dreidimensionaler konformaler Radiotherapie (3D-CRT) oder multisegmentaler konformaler Radiotherapie (MS-CRT) des Mammakarzinoms wurden ausgewertet.Material und Methodik:Dreidimensionale und multisegmentale konformale Bestrahlungspläne wurden für 436 unilaterale (217 linksseitige) Brüste erstellt. Zwischen 2005 und 2007 erhielten alle Patientinnen eine MS-CRT. Zur PTV-Konturierung und Feldausrichtung wurden Hilfsstrukturen angebracht. Das durchschnittliche PTV betrug 1 130 cm3 (bei zehn Patientinnen > 2 200 cm3). Im Anschluss an die dreidimensionale Planung mit optimal gewichteten medialen und lateralen Feldern bis zu einer Gesamtdosis 50,4/1,8 Gy erfolgte die multisegmentale Planung mit einer angemessen hohen Dosiswolke für das mediale Teilfeld und erneuter Optimierung. Dies wurde für das laterale Teilfeld wiederholt und abschließend optimiert. Bei der Beurteilung der PTV-Erfassung wurde der ICRU 50 berücksichtigt: die Anteile des PTV, die 95–107%, < 95% und > 107% der verordneten Dosis erhielten (PTVD95–107%, PTVD107%), sowie das Dosismaximum (PTVDmax). Zum Vergleich der Dosisbelastung der OARs wurden die Durchschnittsdosen der ipsi-/kontralateralen Lungen, der kontralateralen Brust und des Herzen dokumentiert.Ergebnisse:Die multisegmentale Planung erbrachte eine signifikant (p < 0,0001) bessere PTV-Erfassung (PTVD95–107% 82,8% vs. 90,9%, PTVD107% 5,9% vs. 0,3% und PTVDmax 56,6 vs. 54,3 Gy). Die durchschnittlichen OAR-Dosen blieben nahezu unverändert: ipsilaterale Lunge 10,5 versus 10,4 Gy, kontralaterale Lunge 0,4 versus 0,4 Gy, und kontralaterale Brust 0,8 versus 0,8 Gy, Herz (bei linksseitigem Brustkrebs) 4,8 versus 4,8 Gy. Für die Teilfelder wurden durchschnittlich 9,8 MU (Monitoreinheiten) benötigt, d.h. eine Gesamterhöhung um im Mittel 7,6 MU. Die Planungsprozedur dauerte 10–20 min und die Bestrahlung 5–10 min.Schlussfolgerung:Die MS-CRT stellt eine gute Alternative zur intensitätsmodulierten Radiotherapie (IMRT) der Brust dar und scheint sich vor allem bei rechtsseitigem Brustkrebs anzubieten, während bei Befall der linken Mamma aufgrund der kardialen Nebenwirkungen vor einer abschließenden Bewertung eine längere Nachbeobachtung erforderlich ist.

Conkiss: conformal kidneys sparing 3D noncoplanar radiotherapy treatment for pancreatic cancer as an alternative to IMRT.

When treating pancreatic cancer using standard (ST) 3D conformal radiotherapy (3D-CRT) beam arrangements, the kidneys often receive a higher dose than their probable tolerance limit. Our aim was to elaborate a new planning method that--similarly to IMRT--effectively spares the kidneys without compromising the target coverage. Conformal kidneys sparing (CONKISS) 5-field, noncoplanar plans were compared with ST plans for 23 consecutive patients retrospectively. Optimal beam arrangements were used consisting of a left- and right-wedged beam-pair and an anteroposterior beam inclined in the caudal direction. The wedge direction determination (WEDDE) algorithm was developed to adjust the adequate direction of wedges. The aimed organs at risk (OARs) mean dose limits were: kidney <12 Gy, liver <25 Gy, small bowels <30 Gy, and spinal cord maximum <45 Gy. Conformity and homogeneity indexes with z-test were used to evaluate and compare the different planning approaches. The mean dose to the kidneys decreased significantly (p < 0.05): left kidney 7.7 vs. 10.7 Gy, right kidney 9.1 vs. 11.7 Gy. Meanwhile the mean dose to the liver increased significantly (18.1 vs. 15.0 Gy). The changes in the conformity, homogeneity, and in the doses to other OARs were not significant. The CONKISS method balances the load among the OARs and significantly reduces the dose to the kidneys, without any significant change in the conformity and homogeneity. Using 3D-CRT the CONKISS method can be a smart alternative to IMRT to enhance the possibility of dose escalation.

A Pelvic Phantom for Modeling Internal Organ Motions

A pelvic phantom was developed for use in testing image-guided radiation therapy (IGRT) and adaptive applications in radiation therapy (ART) with simulating the anterior-posterior internal organ motions during prostate radiotherapy. Measurements could be done with an ionization chamber (IC) in the simulated prostate. The rectum was simulated by air-equivalent material (AEM). The volume superior to the IC placement was considered as the bladder. The extension of AEM volume could be varied. The vertical position of the IC placement could be shifted by ± 1 cm to simulate the prostate motion parallel to the changes in bladder volume. The reality of the simulation was inspected. Three-millimeter-slice-increment computed tomography (CT) scans were taken for irradiation planning. The structure set was adapted to the phantom from a treated patient. Planning target volume was delineated according to the RTOG 0126 study. IMRT and 3D conformal radiation therapy (3D-CRT) plans were made. Prostate motion and rectum volume changes were simulated in the phantom. IC displacement was corrected by phantom shifting. The delivered dose was measured with IC in 7 cases using intensity-modulated radiation therapy (IMRT) and 3D-CRT fractions, and single square-shaped beams: anteroposterior (AP), posteroanterior (PA), and lateral (LAT). Variations from the calculated doses were slightly below 1% at IMRT and around 1% at 3D-CRT; below 4.5% at square AP beam; up to 9% at square PA beam; and around 0.5% at square LAT beam. Other authors have already shown that by using planning systems and ultrasonic and cone beam CT guidance, correction of organ motions in a real patient during prostate cancer IGRT does not have a significant dosimetric effect. The inspection of our phantom--as described here-ended with similar results. Our team suggested that our model is sufficiently realistic and can be used for IGRT and ART testing.