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Equivalent Biological Effective Dose (BEDeq) Modeling of Tumor Control Probability in Partial Breast Irradiation
Proceedings of the 47th Annual ASTRO Meeting
The P value for association with fully invasive disease was highly significant using Fisher’s exact test. The pathology of the breast-cancer-associated HBP1 variants showed both node-negative and node-positive breast cancers. Lastly, the impact of abrogating HBP1 function on tumorigenic potential and invasiveness was investigated. An RNAi-mediated knockdown of the HBP1 gene in breast cancer cells resulted in increased anchorage-independent growth and increased invasiveness--consistent with a possible role in invasive breast cancer. Conclusions: Together, our clinical and molecular studies implicate that HBP1 in regulating both proliferation and invasiveness. The clinical correlation to invasive breast cancer suggests that HBP1 may be an excellent candidate marker in an ill-defined breast cancer transition between ductal invasiveness and lymph node involvement.
2037
Equivalent Biological Effective Dose (BEDeq) Modeling of Tumor Control Probability in Partial Breast Irradiation
S.C. Lymberis, B.S. Rosenstein, G. Jozsef, S.C. Formenti, J. DeWyngaert Radiation Oncology, New York University, NYC, NY Purpose/Objective: A variety of Partial Breast Irradiation (PBI) Protocols have been developed to treat the original tumor bed with a margin, including brachytherapy and external beam 3D-CRT. In our study we performed biologically effective dose (BEDeq) analysis of interstitial, Mammosite Balloon brachytherapy, and external beam techniques utilized at William Beaumont and New York University comparing the integral dose of both the planning target volume (PTV) and normal breast. Materials/Methods: Since the commonly used linear-quadratic (L-Q) model does not allow for modeling of dose gradients within the breast volume, we utilized a technique reported by Dale et al. (IJROBP, 1997) which enables the comparison of equivalent biologically effective dose (BEDeq) of the partial breast volume irradiated. The BEDeq model was used to compare the radiobiological consequences of dose gradients in both brachytherapy and 3D-CRT external beam PBI techniques. Results: Modeling of BEDeq across PBI techniques was used to predict tumor control probability and is shown in Table below. Excluding interstitial implant, BEDeq tumor control values are largely comparable between mammosite, and external beam PBI techniques. Dosimetric data derived from published reports of the different techniques demonstrate that with brachytherapy, a larger volume of breast is exposed to lower doses of radiation therapy. Additionally, in 3D-CRT External beam techniques result in a higher integral dose to the ipsilateral breast. Conclusions: While the BEDeq tumor control values are comparable across different techniques of partial breast radiation, nevertheless there are distinct dosimetric outcomes in regards to breast volume radiated. In external beam PBI, the variation in dose with in the target volume is small, while in brachytherapy there is great variation of dose with in the target volume. Biological endpoints including tumor control, normal tissue fibrosis and risk of carcinogenesis are likely to be influenced by these differences. Dosimetric Analysis of PBI Techniques: BEDeq Values for Tumor Control and Percent Breast Volume Receiving Percent Prescription Dose
2038
Photodynamic Therapy for Salvage of Radiation Failure in Breast Cancer 1
C. Sibata, R. Allison,1 G. Downie,3 C. Childs,3 R. Cuenca2 Radiation Oncology, East Carolina University, Greenville, NC, 2Surgery, East Carolina University, Greenville, NC, 3 Medicine, East Carolina University, Greenville, NC 1
Purpose/Objective: Breast cancer patients who experience chest wall recurrence often can be salvaged by radiation. However, for those patients who re-recur, therapeutic options are limited. Photodynamic therapy is an oncologic treatment employing a photosensitizer that accumulates in malignant tissue that is then locally activated by light. This creates a cytotoxic/vasculotoxic photodynamic reaction which can be tumorcidal. We examined the potential role of PDT in patients who had failed radiation for chest wall recurrence. Materials/Methods: A total of 20 women (age 41– 81) with biopsy proven re-recurrence of breast cancer to the chest wall, who had failed salvage external beam radiation, underwent PDT. All patients had failed within the radiation portals. Prior radiation
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The P value for association with fully invasive disease was highly significant using Fisher’s exact test. The pathology of the breast-cancer-associated HBP1 variants showed both node-negative and node-positive breast cancers. Lastly, the impact of abrogating HBP1 function on tumorigenic potential and invasiveness was investigated. An RNAi-mediated knockdown of the HBP1 gene in breast cancer cells resulted in increased anchorage-independent growth and increased invasiveness--consistent with a possible role in invasive breast cancer. Conclusions: Together, our clinical and molecular studies implicate that HBP1 in regulating both proliferation and invasiveness. The clinical correlation to invasive breast cancer suggests that HBP1 may be an excellent candidate marker in an ill-defined breast cancer transition between ductal invasiveness and lymph node involvement.
2037
Equivalent Biological Effective Dose (BEDeq) Modeling of Tumor Control Probability in Partial Breast Irradiation
S.C. Lymberis, B.S. Rosenstein, G. Jozsef, S.C. Formenti, J. DeWyngaert Radiation Oncology, New York University, NYC, NY Purpose/Objective: A variety of Partial Breast Irradiation (PBI) Protocols have been developed to treat the original tumor bed with a margin, including brachytherapy and external beam 3D-CRT. In our study we performed biologically effective dose (BEDeq) analysis of interstitial, Mammosite Balloon brachytherapy, and external beam techniques utilized at William Beaumont and New York University comparing the integral dose of both the planning target volume (PTV) and normal breast. Materials/Methods: Since the commonly used linear-quadratic (L-Q) model does not allow for modeling of dose gradients within the breast volume, we utilized a technique reported by Dale et al. (IJROBP, 1997) which enables the comparison of equivalent biologically effective dose (BEDeq) of the partial breast volume irradiated. The BEDeq model was used to compare the radiobiological consequences of dose gradients in both brachytherapy and 3D-CRT external beam PBI techniques. Results: Modeling of BEDeq across PBI techniques was used to predict tumor control probability and is shown in Table below. Excluding interstitial implant, BEDeq tumor control values are largely comparable between mammosite, and external beam PBI techniques. Dosimetric data derived from published reports of the different techniques demonstrate that with brachytherapy, a larger volume of breast is exposed to lower doses of radiation therapy. Additionally, in 3D-CRT External beam techniques result in a higher integral dose to the ipsilateral breast. Conclusions: While the BEDeq tumor control values are comparable across different techniques of partial breast radiation, nevertheless there are distinct dosimetric outcomes in regards to breast volume radiated. In external beam PBI, the variation in dose with in the target volume is small, while in brachytherapy there is great variation of dose with in the target volume. Biological endpoints including tumor control, normal tissue fibrosis and risk of carcinogenesis are likely to be influenced by these differences. Dosimetric Analysis of PBI Techniques: BEDeq Values for Tumor Control and Percent Breast Volume Receiving Percent Prescription Dose
2038
Photodynamic Therapy for Salvage of Radiation Failure in Breast Cancer 1
C. Sibata, R. Allison,1 G. Downie,3 C. Childs,3 R. Cuenca2 Radiation Oncology, East Carolina University, Greenville, NC, 2Surgery, East Carolina University, Greenville, NC, 3 Medicine, East Carolina University, Greenville, NC 1
Purpose/Objective: Breast cancer patients who experience chest wall recurrence often can be salvaged by radiation. However, for those patients who re-recur, therapeutic options are limited. Photodynamic therapy is an oncologic treatment employing a photosensitizer that accumulates in malignant tissue that is then locally activated by light. This creates a cytotoxic/vasculotoxic photodynamic reaction which can be tumorcidal. We examined the potential role of PDT in patients who had failed radiation for chest wall recurrence. Materials/Methods: A total of 20 women (age 41– 81) with biopsy proven re-recurrence of breast cancer to the chest wall, who had failed salvage external beam radiation, underwent PDT. All patients had failed within the radiation portals. Prior radiation
S253