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      In Regard to Kil et al

      letter
      , MD, PhD * , , MD, , MD, , MD, PhD, , MD, PhD, , MD, PhD
      Advances in Radiation Oncology
      Elsevier

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          Abstract

          We read with great interest the article by Kil et al 1 on symptom relief after quad shot (QS) for 2 patients with neglected breast cancer (NBC). Palliative radiation therapy is effective for various symptoms caused by NBC, and as the authors described, it is desirable to use a short-course radiation therapy with a high rate of symptom relief to avoid delaying systemic cancer therapy. However, we believe that further consideration may be necessary to decide the eligibility for QS and single fraction (SF) radiation therapy for NBC. The authors noted that a disadvantage of SF was the high rate of recurring breast symptoms, requiring repeat radiation therapy in 57% of cases. 2 Conversely, the other 43% of cases did not require reirradiation. In QS, up to 3 or 4 courses of radiation therapy can be repeated, and the advantage of QS may be that systemic chemotherapy can be started immediately after the first QS, and the decision to perform a second QS can be made based on the subsequent outcome during the systemic cancer therapy. However, in the 2 cases presented by the authors, 3 repeated courses of radiation therapy were needed, which may not differ from the need for reirradiation in SF. Another concern in selecting QS for NBC is whether QS contributes to maintaining cancer-control effects and reducing side effects. The concept of QS first reported by William was intending to maintain the high level of tumor control assuming an α:β ratio of 10 and reduce the expected late complications assuming an α:β ration of 4. 3 In radiation therapy of NBC, as noted by the authors, the α:β ratios of the breast tissue and breast cancer are low at 2 to 4 and 3, respectively. 4 , 5 Therefore, sufficient tumor control effects might not be expected in NBC as in tumors with high α:β ratios, such as pelvic malignancies and advanced head and neck cancers, for which the efficacy of QS has been reported. 3 , 6 We again appreciate the authors’ great effort toward revealing the usefulness of QS for NBC. Although the rate of repeat radiation therapy is high, we believe that SF is also a good option considering the convenience of a one-time procedure. Further studies regarding the proper use of SF and QS in NBC will be needed in the future. Disclosures The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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          The alfa and beta of tumours: a review of parameters of the linear-quadratic model, derived from clinical radiotherapy studies

          Background Prediction of radiobiological response is a major challenge in radiotherapy. Of several radiobiological models, the linear-quadratic (LQ) model has been best validated by experimental and clinical data. Clinically, the LQ model is mainly used to estimate equivalent radiotherapy schedules (e.g. calculate the equivalent dose in 2 Gy fractions, EQD2), but increasingly also to predict tumour control probability (TCP) and normal tissue complication probability (NTCP) using logistic models. The selection of accurate LQ parameters α, β and α/β is pivotal for a reliable estimate of radiation response. The aim of this review is to provide an overview of published values for the LQ parameters of human tumours as a guideline for radiation oncologists and radiation researchers to select appropriate radiobiological parameter values for LQ modelling in clinical radiotherapy. Methods and materials We performed a systematic literature search and found sixty-four clinical studies reporting α, β and α/β for tumours. Tumour site, histology, stage, number of patients, type of LQ model, radiation type, TCP model, clinical endpoint and radiobiological parameter estimates were extracted. Next, we stratified by tumour site and by tumour histology. Study heterogeneity was expressed by the I2 statistic, i.e. the percentage of variance in reported values not explained by chance. Results A large heterogeneity in LQ parameters was found within and between studies (I2 > 75%). For the same tumour site, differences in histology partially explain differences in the LQ parameters: epithelial tumours have higher α/β values than adenocarcinomas. For tumour sites with different histologies, such as in oesophageal cancer, the α/β estimates correlate well with histology. However, many other factors contribute to the study heterogeneity of LQ parameters, e.g. tumour stage, type of LQ model, TCP model and clinical endpoint (i.e. survival, tumour control and biochemical control). Conclusions The value of LQ parameters for tumours as published in clinical radiotherapy studies depends on many clinical and methodological factors. Therefore, for clinical use of the LQ model, LQ parameters for tumour should be selected carefully, based on tumour site, histology and the applied LQ model. To account for uncertainties in LQ parameter estimates, exploring a range of values is recommended. Electronic supplementary material The online version of this article (10.1186/s13014-018-1040-z) contains supplementary material, which is available to authorized users.
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            Is α/β for breast cancer really low?

            Low α/β ratio for breast cancer has drawn a growing interest for exploring hypofractionation for breast irradiation. This work is to confirm the low α/β ratio based on large randomized clinical trials of breast irradiation. A model based on the generalized linear-quadratic (LQ) model and Poisson statistical model was developed to calculate disease-free survival with consideration of clonogen proliferation during the course of radiation treatment and exponential behavior of survival rate with follow-up time. Outcome data from a series of randomized clinical trials of early-stage breast radiotherapy were fitted to estimate the model parameters. Other clinical outcomes, including treatments with surgery alone or radiotherapy alone were used to validate the model and the estimated parameters. Hypofractionation regimens were proposed based on the newly estimated LQ parameters. Plausible population averaged radiobiologic parameters for breast cancer (95% confidence level) are α/β=2.88 (0.75-5.01) Gy; α=0.08±0.02Gy(-1); potential doubling time T(d)=14.4±7.8day. The analysis of the radiation-alone data suggested an α/β ratio of 3.89±6.25Gy, verifying the low α/β ratio based on the post-lumpectomy irradiation data. The hypofractionation regimens that are equivalent to the conventional regimen of 2.0Gy×25 in 5weeks include 2.26Gy×20, 3.34Gy×10, 4.93Gy×5 or 3.39Gy×10 (BID). The analysis of the available clinical data from multiple institutions support that breast cancer has a low ratio of α/β, encouraging hypofractionated radiotherapy regimens for breast cancer. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.
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              Palliative head and neck radiotherapy with the RTOG 8502 regimen for incurable primary or metastatic cancers.

              To report on our institutional experience of palliative radiotherapy (RT) of cancers in the head and neck by the RTOG 8502 'QUAD SHOT' regimen.
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                Author and article information

                Contributors
                Journal
                Adv Radiat Oncol
                Adv Radiat Oncol
                Advances in Radiation Oncology
                Elsevier
                2452-1094
                15 September 2023
                Sep-Oct 2023
                15 September 2023
                : 8
                : 5
                : 101293
                Affiliations
                [0001]Department of Radiology, Akita University Graduate School of Medicine, Akita, Japan
                Author notes
                [* ]Corresponding author: Yuki Wada, MD, PhD ywada@ 123456med.akita-u.ac.jp
                Article
                S2452-1094(23)00121-5 101293
                10.1016/j.adro.2023.101293
                10504434
                37719310
                cf5ebff1-047e-4f25-b7e1-68ca5ae2a369
                © 2023 The Author(s)

                This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

                History
                : 23 May 2023
                : 23 May 2023
                Categories
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