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Marciana N. Duma - One of the best experts on this subject based on the ideXlab platform.
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Effect of hypofractionation on the incidental axilla dose during Tangential Field radiotherapy in breast cancer
Strahlentherapie und Onkologie, 2020Co-Authors: Kai J. Borm, Markus Oechsner, Mathias Düsberg, Gabriel Buschner, Weber Wolfgang, Stephanie E. Combs, Marciana N. DumaAbstract:Objective Tangential Field irradiation in breast cancer potentially treats residual tumor cells in the axilla after sentinel lymph node biopsy (SLNB). In recent years, hypofractionated radiotherapy has gained importance and currently represents the recommended standard in adjuvant breast cancer treatment for many patients. So far, the impact of hypofractionation on the effect of incidental lymph node irradiation has not be addressed. Materials and methods Biological effective dose (BED) and tumor control probability (TCP) were estimated for four different hypofractionated radiation schemes (42.50 Gy in 16 fractions [Fx]; 40.05 Gy in 15 Fx; 27 Gy in 5 Fx; and 26 in 5 Fx) and compared to conventional fractionation (50 Gy in 25 Fx). For calculation of BED and TCP, a previously published radiobiological model with an α/β ratio of 4 Gy was used. The theoretical BED and TCP for incidental irradiation between 0 and 100% of the prescribed dose were evaluated. Subsequently, we assessed BED and TCP in 431 axillary lymph node metastases. Results The extent of incidental lymph node irradiation and the fractionation scheme have a direct impact on BED and TCP. The estimated mean TCP in the axillary nodes ranged from 1.5 ± 6.4% to 57.5 ± 22.9%, depending on the patient’s anatomy and the fractionation scheme. Hypofractionation led to a significant reduction of mean TCP of lymph node metastases for all schedules. Conclusion Our data indicate that hypofractionation might affect the effectiveness of incidental radiotherapy in the axilla. This is particularly relevant for patients with positive sentinel lymph nodes who receive SLNB only.
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effect of hypofractionation on the incidental axilla dose during Tangential Field radiotherapy in breast cancer
Strahlentherapie Und Onkologie, 2020Co-Authors: Kai J. Borm, Markus Oechsner, Mathias Düsberg, Gabriel Buschner, Weber Wolfgang, Stephanie E. Combs, Marciana N. DumaAbstract:OBJECTIVE Tangential Field irradiation in breast cancer potentially treats residual tumor cells in the axilla after sentinel lymph node biopsy (SLNB). In recent years, hypofractionated radiotherapy has gained importance and currently represents the recommended standard in adjuvant breast cancer treatment for many patients. So far, the impact of hypofractionation on the effect of incidental lymph node irradiation has not be addressed. MATERIALS AND METHODS Biological effective dose (BED) and tumor control probability (TCP) were estimated for four different hypofractionated radiation schemes (42.50 Gy in 16 fractions [Fx]; 40.05 Gy in 15 Fx; 27 Gy in 5 Fx; and 26 in 5 Fx) and compared to conventional fractionation (50 Gy in 25 Fx). For calculation of BED and TCP, a previously published radiobiological model with an α/β ratio of 4 Gy was used. The theoretical BED and TCP for incidental irradiation between 0 and 100% of the prescribed dose were evaluated. Subsequently, we assessed BED and TCP in 431 axillary lymph node metastases. RESULTS The extent of incidental lymph node irradiation and the fractionation scheme have a direct impact on BED and TCP. The estimated mean TCP in the axillary nodes ranged from 1.5 ± 6.4% to 57.5 ± 22.9%, depending on the patient's anatomy and the fractionation scheme. Hypofractionation led to a significant reduction of mean TCP of lymph node metastases for all schedules. CONCLUSION Our data indicate that hypofractionation might affect the effectiveness of incidental radiotherapy in the axilla. This is particularly relevant for patients with positive sentinel lymph nodes who receive SLNB only.
Wim Duthoy - One of the best experts on this subject based on the ideXlab platform.
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Automatic Generation of a Plan Optimization Volume for Tangential Field Breast Cancer Radiation Therapy
Strahlentherapie und Onkologie, 2005Co-Authors: Koen Vaerenbergh, Werner Gersem, Luc Vakaet, Marc Coghe, Tom Boterberg, Marlies Bakker, Christina Derie, Wouter Willaert, Patricia Seij, Wim DuthoyAbstract:Hintergrund und Ziel: Dosishomogenitität ist eines der Ziele bei der Planung für die Strahlentherapie nach brusterhaltender Operation. Für die dreidimensionale (3-D) Optimierung der Dosisverteilung mit Hilfe serieller CT-Schnitte müssen passende Volumina ermittelt werden. Ziel dieser Studie war, eine computergesteuerte Erstellung des optimierten Planungszielvolumens (POV) und des bestrahlten Volumens (IV) zu entwickeln und ihren Einsatz in einem schnellen Rechner zur Optimierung der Dosishomogenität zu automatisieren. Patienten und Methoden: Die Simulation wurde nach unserem Standardverfahren durchgeführt, bei dem eine Bleikette um die tastbare Brust gelegt wird, um die Festlegung von Gantry-Winkel, Kollimatorwinkel und Feldgrößen für Tangentiale Keilfilterfelder zu erleichtern. In einer Abwandlung des Standardverfahrens wurde ein anterolaterales Röntgenbild aufgenommen, dessen Achse orthogonal zur Zentralebene der beiden Tangentialen Strahlen verläuft. Serielle CT-Schnitte wurden in Behandlungsposition aufgenommen, und mit den geometrischen Daten der drei simulierten Felder erstellte ein Computerprogramm POV und IV. Für jede Patientin wurde die Wichtung für die Strahlenfelder mit und ohne Keilfilter optimiert, indem manuell nach menschlichem Ermessen nur die zentrale Schicht (2-D) bzw. alle CT-Schichten herangezogen wurden (3-D). Alternativ wurde ein Computeralgorithmus eingesetzt, der POV, IV und das bestrahlte Lungenvolumen nach der Methode der Constrained Matrix Inversion (CMI) optimiert. Die so erzielten Dosisverteilungen wurden verglichen. Ergebnisse: Das gesamte Planungsverfahren dauerte durchschnittlich 44 min, von denen < 7 min für menschliche Interaktion benötigt wurden, im Vergleich zu rund 52 Minuten beim Standardverfahren der Universitätsklinik Gent/Belgien. Die Simulationszeit ist um 2–3 min länger. Das Verfahren liefert 3-D-Information über die Dosisverteilung. Dosishomogenität und minimale Dosis innerhalb des POV und maximale Dosis innerhalb des IV unterschieden sich bei den drei Optimierungstechniken nicht signifikant. Schlussfolgerung: Dieses automatisierte Planungsverfahren kann sowohl das Festlegen des klinischen Zielvolumens ersetzen als auch Näherungsmethoden erfahrener Planer. Background and Purpose: Dose homogeneity is one of the objectives during computer planning of postoperative radiotherapy of the conserved breast. For three-dimensional (3-D) optimization of the dose distribution using serial CT scan images, suitable volumes have to be delineated. The purpose of this study was to develop a computer-generated delineation of a plan optimization volume (POV) and an irradiated volume (IV) and to automate their use in a fast dose homogeneity optimization engine. Patients and Methods: Simulation was performed according to our standard procedure which involves the positioning of a lead collar around the palpable breast to facilitate the definition of gantry angle, collimator angle and Field aperture for Tangential wedged photon beams. In a change to the standard procedure an anterolateral radiograph was taken with its axis orthogonal to the central plane of the two Tangential half-beams. Images from a serial CT scan were acquired in treatment position, and the geometric data of the three simulated beams were used by a computer program to generate the POV and IV. For each patient, weights of wedged and unwedged beams were optimized by either human heuristics using only the central slice (2-D), the whole set of CT slices (3-D), or by a computer algorithm using the POV, IV and lung volume with constrained matrix inversion (CMI) as optimization method. The resulting dose distributions were compared. Results: The total planning procedure took, on average, 44 min of which < 7 min were needed for human interactions, compared to about 52 min for the standard planning at Ghent University Hospital, Belgium. The simulation time is increased by 2–3 min. The method provides 3-D information of the dose distribution. Dose homogeneity and minimum dose inside the POV and maximum dose inside the IV were not significantly different for the three optimization techniques. Conclusion: This automated planning method is capable of replacing the contouring of the clinical target volume as well as the trial-and-error procedure of assigning weights of wedged and unwedged beams by an experienced planner.
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automatic generation of a plan optimization volume for Tangential Field breast cancer radiation therapy
Strahlentherapie Und Onkologie, 2005Co-Authors: Koen Vaerenbergh, Werner Gersem, Luc Vakaet, Marc Coghe, Tom Boterberg, Marlies Bakker, Christina Derie, Wouter Willaert, Patricia Seij, Wim DuthoyAbstract:Dose homogeneity is one of the objectives during computer planning of postoperative radiotherapy of the conserved breast. For three-dimensional (3-D) optimization of the dose distribution using serial CT scan images, suitable volumes have to be delineated. The purpose of this study was to develop a computer-generated delineation of a plan optimization volume (POV) and an irradiated volume (IV) and to automate their use in a fast dose homogeneity optimization engine. Simulation was performed according to our standard procedure which involves the positioning of a lead collar around the palpable breast to facilitate the definition of gantry angle, collimator angle and Field aperture for Tangential wedged photon beams. In a change to the standard procedure an anterolateral radiograph was taken with its axis orthogonal to the central plane of the two Tangential half-beams. Images from a serial CT scan were acquired in treatment position, and the geometric data of the three simulated beams were used by a computer program to generate the POV and IV. For each patient, weights of wedged and unwedged beams were optimized by either human heuristics using only the central slice (2-D), the whole set of CT slices (3-D), or by a computer algorithm using the POV, IV and lung volume with constrained matrix inversion (CMI) as optimization method. The resulting dose distributions were compared. The total planning procedure took, on average, 44 min of which < 7 min were needed for human interactions, compared to about 52 min for the standard planning at Ghent University Hospital, Belgium. The simulation time is increased by 2–3 min. The method provides 3-D information of the dose distribution. Dose homogeneity and minimum dose inside the POV and maximum dose inside the IV were not significantly different for the three optimization techniques. This automated planning method is capable of replacing the contouring of the clinical target volume as well as the trial-and-error procedure of assigning weights of wedged and unwedged beams by an experienced planner.
Dwight E Heron - One of the best experts on this subject based on the ideXlab platform.
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clinical implementation of Tangential Field intensity modulated radiation therapy imrt using sliding window technique and dosimetric comparison with 3d conformal therapy 3dcrt in breast cancer
Medical Dosimetry, 2007Co-Authors: Raj N Selvaraj, Sushil Beriwal, Roya J Pourarian, Ron Lalonde, Alex F Chen, K Mehta, Gwendolyn Brunner, Kathy A Wagner, Dwight E HeronAbstract:Abstract The purpose of this study was to evaluate the clinical implementation of Tangential Field IMRT using sliding window technique and to compare dosimetric parameters with 3-dimensional conformal radiation therapy (3DCRT). Twenty breast cancer patients were randomly selected for comparison of intensity modulated radiation therapy (IMRT)-based treatment plan with 3DCRT. Inverse treatment was performed using the sliding window technique, employing the Eclipse® Planning System (version 7.1.59, Varian, Palo Alto, CA). The dosimetric parameters compared were V95 (the percentage of target volume getting ≥95% of prescribed dose), V105, V110, and dose homogeneity index, DHI (percentage of target volume getting between 95% and 110% of prescribed dose). The mean V95, DHI, V105, and V110 for target volume for IMRT vs. 3D were 90.6% (standard deviation [SD]: 3.2) vs. 91% (SD: 3.0), 87.7 (SD: 6.0) vs. 82.6 (SD: 7.8), 27.3% (SD: 20.3) vs. 49.4% (SD: 14.3), and 2.8 (SD: 5.6) vs. 8.4% (SD: 7.4), respectively. DHI was increased by 6.3% with IMRT compared to 3DCRT (p 5% of prescribed dose with IMRT were reduced by 9.9%, 2.2%, and 35%, respectively. The mean of total monitor units used for IMRT and 3DCRT was about the same (397 vs. 387). The Tangential Field IMRT for intact breast using sliding window technique was successfully implemented in the clinic. We have now treated more than 1000 breast cancer patients with this technique. The dosimetric data suggest improved dose homogeneity in the breast and reduction in the dose to lung and heart for IMRT treatments, which may be of clinical value in potentially contributing to improved cosmetic results and reduced late treatment-related toxicity.
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Intensity modulated radiation therapy (IMRT) reduces the dose to the contralateral breast when compared to conventional Tangential Fields for primary breast irradiation
Breast Cancer Research and Treatment, 2006Co-Authors: Ajay K. Bhatnagar, E Brandner, Deborah Sonnik, Andrew Wu, Shalom Kalnicki, Melvin Deutsch, Dwight E HeronAbstract:Purpose To determine the dose received by the contralateral breast during primary breast irradiation using IMRT compared to conventional Tangential Field techniques. Methods and materials Between March 2003 and March 2004, 83 patients with breast carcinoma were treated using 6, 10, or mixed 6/18 MV photons (65 with Tangential IMRT technique and 18 with 3-dimensional technique using Tangential Fields with wedges) for primary breast irradiation following breast-conserving surgery. Paired thermoluminescent dosimeters (TLDs) were placed on each patient’s contralateral breast, 4 and 8 cm from the center of the medial border of the Tangential Field. The TLDs were left on the patient during a single fraction and then measured 24 h afterwards. Results The mean dose delivered with photons to the primary breast for all patients was 4999 cGy (SD=52) with a mean single fraction dose of 199 cGy (SD=8). The mean percent of the prescribed dose to the contralateral breast measured at the 4- and 8-cm positions were 7.19% (SD=2.28) and 4.63% (SD=2.12), respectively, for patients treated with IMRT compared to 11.22% (SD=2.73) and 10.70% (SD=3.44), respectively, for the patients treated with conventional Tangential Field techniques. This represented a 36% and 57% reduction at the 4 and 8-cm contralateral positions, respectively, in the mean dose to the contralateral breast using IMRT compared to 3-D technique which was statistically significant (p
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Intensity modulated radiation therapy (IMRT) reduces the dose to the contralateral breast when compared to conventional Tangential Fields for primary breast irradiation.
Breast Cancer Research and Treatment, 2005Co-Authors: Ajay Bhatnagar, E Brandner, Deborah Sonnik, Andrew Wu, Shalom Kalnicki, Melvin Deutsch, Dwight E HeronAbstract:Purpose To determine the dose received by the contralateral breast during primary breast irradiation using IMRT compared to conventional Tangential Field techniques.
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Intensity-modulated radiation therapy (IMRT) reduces the dose to the contralateral breast when compared to conventional Tangential Fields for primary breast irradiation: initial report.
Cancer Journal, 2004Co-Authors: Ajay Bhatnagar, E Brandner, Deborah Sonnik, Andrew Wu, Shalom Kalnicki, Melvin Deutsch, Dwight E HeronAbstract:PURPOSE This study was designed to compare the dose received by the contralateral breast during primary breast irradiation using intensity-modulated radiotherapy with the dose received via conventional Tangential Field techniques. METHODS/MATERIALS Between March 2003 and March 2004, 44 patients with breast carcinoma were treated using 6-, 10-, or mixed 6/18-MV photons (36 with Tangential intensity-modulated radiotherapy technique and eight with three-dimensional technique using Tangential Fields with wedges) for primary breast irradiation after breast-conserving surgery. Paired thermoluminescent dosimeters were placed on each patient's contralateral breast, 4 cm from the center of the medial border of the Tangential Field. The thermoluminescent dosimeters were left on the patient during a single fraction and then measured 24 hours later. RESULTS The mean dose delivered with photons to the primary breast for all patients was 4998 cGy [SD = 52], and the mean single fraction dose was 200 cGy [SD = 9]. The mean percent of the prescribed dose to the contralateral breast was 7.74% (SD = 2.35) for patients treated with intensity-modulated radiotherapy, compared with 9.74% [SD = 2.04] for the patients treated with conventional Tangential Field techniques. This represented a 20% reduction in the mean dose to the contralateral breast with the use of intensity-modulated radiotherapy when compared with the dose received via the three-dimensional technique, a result that was statistically significant. CONCLUSION Primary breast irradiation with Tangential intensity-modulated radiotherapy technique significantly reduces the dose to the contralateral breast when compared with conventional Tangential techniques.
Koen Vaerenbergh - One of the best experts on this subject based on the ideXlab platform.
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Automatic Generation of a Plan Optimization Volume for Tangential Field Breast Cancer Radiation Therapy
Strahlentherapie und Onkologie, 2005Co-Authors: Koen Vaerenbergh, Werner Gersem, Luc Vakaet, Marc Coghe, Tom Boterberg, Marlies Bakker, Christina Derie, Wouter Willaert, Patricia Seij, Wim DuthoyAbstract:Hintergrund und Ziel: Dosishomogenitität ist eines der Ziele bei der Planung für die Strahlentherapie nach brusterhaltender Operation. Für die dreidimensionale (3-D) Optimierung der Dosisverteilung mit Hilfe serieller CT-Schnitte müssen passende Volumina ermittelt werden. Ziel dieser Studie war, eine computergesteuerte Erstellung des optimierten Planungszielvolumens (POV) und des bestrahlten Volumens (IV) zu entwickeln und ihren Einsatz in einem schnellen Rechner zur Optimierung der Dosishomogenität zu automatisieren. Patienten und Methoden: Die Simulation wurde nach unserem Standardverfahren durchgeführt, bei dem eine Bleikette um die tastbare Brust gelegt wird, um die Festlegung von Gantry-Winkel, Kollimatorwinkel und Feldgrößen für Tangentiale Keilfilterfelder zu erleichtern. In einer Abwandlung des Standardverfahrens wurde ein anterolaterales Röntgenbild aufgenommen, dessen Achse orthogonal zur Zentralebene der beiden Tangentialen Strahlen verläuft. Serielle CT-Schnitte wurden in Behandlungsposition aufgenommen, und mit den geometrischen Daten der drei simulierten Felder erstellte ein Computerprogramm POV und IV. Für jede Patientin wurde die Wichtung für die Strahlenfelder mit und ohne Keilfilter optimiert, indem manuell nach menschlichem Ermessen nur die zentrale Schicht (2-D) bzw. alle CT-Schichten herangezogen wurden (3-D). Alternativ wurde ein Computeralgorithmus eingesetzt, der POV, IV und das bestrahlte Lungenvolumen nach der Methode der Constrained Matrix Inversion (CMI) optimiert. Die so erzielten Dosisverteilungen wurden verglichen. Ergebnisse: Das gesamte Planungsverfahren dauerte durchschnittlich 44 min, von denen < 7 min für menschliche Interaktion benötigt wurden, im Vergleich zu rund 52 Minuten beim Standardverfahren der Universitätsklinik Gent/Belgien. Die Simulationszeit ist um 2–3 min länger. Das Verfahren liefert 3-D-Information über die Dosisverteilung. Dosishomogenität und minimale Dosis innerhalb des POV und maximale Dosis innerhalb des IV unterschieden sich bei den drei Optimierungstechniken nicht signifikant. Schlussfolgerung: Dieses automatisierte Planungsverfahren kann sowohl das Festlegen des klinischen Zielvolumens ersetzen als auch Näherungsmethoden erfahrener Planer. Background and Purpose: Dose homogeneity is one of the objectives during computer planning of postoperative radiotherapy of the conserved breast. For three-dimensional (3-D) optimization of the dose distribution using serial CT scan images, suitable volumes have to be delineated. The purpose of this study was to develop a computer-generated delineation of a plan optimization volume (POV) and an irradiated volume (IV) and to automate their use in a fast dose homogeneity optimization engine. Patients and Methods: Simulation was performed according to our standard procedure which involves the positioning of a lead collar around the palpable breast to facilitate the definition of gantry angle, collimator angle and Field aperture for Tangential wedged photon beams. In a change to the standard procedure an anterolateral radiograph was taken with its axis orthogonal to the central plane of the two Tangential half-beams. Images from a serial CT scan were acquired in treatment position, and the geometric data of the three simulated beams were used by a computer program to generate the POV and IV. For each patient, weights of wedged and unwedged beams were optimized by either human heuristics using only the central slice (2-D), the whole set of CT slices (3-D), or by a computer algorithm using the POV, IV and lung volume with constrained matrix inversion (CMI) as optimization method. The resulting dose distributions were compared. Results: The total planning procedure took, on average, 44 min of which < 7 min were needed for human interactions, compared to about 52 min for the standard planning at Ghent University Hospital, Belgium. The simulation time is increased by 2–3 min. The method provides 3-D information of the dose distribution. Dose homogeneity and minimum dose inside the POV and maximum dose inside the IV were not significantly different for the three optimization techniques. Conclusion: This automated planning method is capable of replacing the contouring of the clinical target volume as well as the trial-and-error procedure of assigning weights of wedged and unwedged beams by an experienced planner.
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automatic generation of a plan optimization volume for Tangential Field breast cancer radiation therapy
Strahlentherapie Und Onkologie, 2005Co-Authors: Koen Vaerenbergh, Werner Gersem, Luc Vakaet, Marc Coghe, Tom Boterberg, Marlies Bakker, Christina Derie, Wouter Willaert, Patricia Seij, Wim DuthoyAbstract:Dose homogeneity is one of the objectives during computer planning of postoperative radiotherapy of the conserved breast. For three-dimensional (3-D) optimization of the dose distribution using serial CT scan images, suitable volumes have to be delineated. The purpose of this study was to develop a computer-generated delineation of a plan optimization volume (POV) and an irradiated volume (IV) and to automate their use in a fast dose homogeneity optimization engine. Simulation was performed according to our standard procedure which involves the positioning of a lead collar around the palpable breast to facilitate the definition of gantry angle, collimator angle and Field aperture for Tangential wedged photon beams. In a change to the standard procedure an anterolateral radiograph was taken with its axis orthogonal to the central plane of the two Tangential half-beams. Images from a serial CT scan were acquired in treatment position, and the geometric data of the three simulated beams were used by a computer program to generate the POV and IV. For each patient, weights of wedged and unwedged beams were optimized by either human heuristics using only the central slice (2-D), the whole set of CT slices (3-D), or by a computer algorithm using the POV, IV and lung volume with constrained matrix inversion (CMI) as optimization method. The resulting dose distributions were compared. The total planning procedure took, on average, 44 min of which < 7 min were needed for human interactions, compared to about 52 min for the standard planning at Ghent University Hospital, Belgium. The simulation time is increased by 2–3 min. The method provides 3-D information of the dose distribution. Dose homogeneity and minimum dose inside the POV and maximum dose inside the IV were not significantly different for the three optimization techniques. This automated planning method is capable of replacing the contouring of the clinical target volume as well as the trial-and-error procedure of assigning weights of wedged and unwedged beams by an experienced planner.
Kai J. Borm - One of the best experts on this subject based on the ideXlab platform.
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Effect of hypofractionation on the incidental axilla dose during Tangential Field radiotherapy in breast cancer
Strahlentherapie und Onkologie, 2020Co-Authors: Kai J. Borm, Markus Oechsner, Mathias Düsberg, Gabriel Buschner, Weber Wolfgang, Stephanie E. Combs, Marciana N. DumaAbstract:Objective Tangential Field irradiation in breast cancer potentially treats residual tumor cells in the axilla after sentinel lymph node biopsy (SLNB). In recent years, hypofractionated radiotherapy has gained importance and currently represents the recommended standard in adjuvant breast cancer treatment for many patients. So far, the impact of hypofractionation on the effect of incidental lymph node irradiation has not be addressed. Materials and methods Biological effective dose (BED) and tumor control probability (TCP) were estimated for four different hypofractionated radiation schemes (42.50 Gy in 16 fractions [Fx]; 40.05 Gy in 15 Fx; 27 Gy in 5 Fx; and 26 in 5 Fx) and compared to conventional fractionation (50 Gy in 25 Fx). For calculation of BED and TCP, a previously published radiobiological model with an α/β ratio of 4 Gy was used. The theoretical BED and TCP for incidental irradiation between 0 and 100% of the prescribed dose were evaluated. Subsequently, we assessed BED and TCP in 431 axillary lymph node metastases. Results The extent of incidental lymph node irradiation and the fractionation scheme have a direct impact on BED and TCP. The estimated mean TCP in the axillary nodes ranged from 1.5 ± 6.4% to 57.5 ± 22.9%, depending on the patient’s anatomy and the fractionation scheme. Hypofractionation led to a significant reduction of mean TCP of lymph node metastases for all schedules. Conclusion Our data indicate that hypofractionation might affect the effectiveness of incidental radiotherapy in the axilla. This is particularly relevant for patients with positive sentinel lymph nodes who receive SLNB only.
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effect of hypofractionation on the incidental axilla dose during Tangential Field radiotherapy in breast cancer
Strahlentherapie Und Onkologie, 2020Co-Authors: Kai J. Borm, Markus Oechsner, Mathias Düsberg, Gabriel Buschner, Weber Wolfgang, Stephanie E. Combs, Marciana N. DumaAbstract:OBJECTIVE Tangential Field irradiation in breast cancer potentially treats residual tumor cells in the axilla after sentinel lymph node biopsy (SLNB). In recent years, hypofractionated radiotherapy has gained importance and currently represents the recommended standard in adjuvant breast cancer treatment for many patients. So far, the impact of hypofractionation on the effect of incidental lymph node irradiation has not be addressed. MATERIALS AND METHODS Biological effective dose (BED) and tumor control probability (TCP) were estimated for four different hypofractionated radiation schemes (42.50 Gy in 16 fractions [Fx]; 40.05 Gy in 15 Fx; 27 Gy in 5 Fx; and 26 in 5 Fx) and compared to conventional fractionation (50 Gy in 25 Fx). For calculation of BED and TCP, a previously published radiobiological model with an α/β ratio of 4 Gy was used. The theoretical BED and TCP for incidental irradiation between 0 and 100% of the prescribed dose were evaluated. Subsequently, we assessed BED and TCP in 431 axillary lymph node metastases. RESULTS The extent of incidental lymph node irradiation and the fractionation scheme have a direct impact on BED and TCP. The estimated mean TCP in the axillary nodes ranged from 1.5 ± 6.4% to 57.5 ± 22.9%, depending on the patient's anatomy and the fractionation scheme. Hypofractionation led to a significant reduction of mean TCP of lymph node metastases for all schedules. CONCLUSION Our data indicate that hypofractionation might affect the effectiveness of incidental radiotherapy in the axilla. This is particularly relevant for patients with positive sentinel lymph nodes who receive SLNB only.