Dose constraints in breast cancer radiotherapy. A critical review.

Radiotherapy plays an essential role in the treatment of breast cancer (BC). Recent advances in treatment technology and radiobiological knowledge have a major impact in BC patients with locoregional disease as the majority are now long-term survivors. Over the last three decades, intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and deep inspiration breath-hold (DIBH) techniques, together with the increasing adoption of moderately hypofractionated and ultra-hypofractionated treatment schedules as well as the possibility to offer partial breast radiotherapy to a well-defined patient subset have significantly changed radiotherapy for BC patients. As dose-volume constraints (DVCs) have to be adapted to these new treatment paradigms we have reviewed available evidence-based data concerning dose-constraints for the main organs at risk (OARs) that apply to the treatment of whole breast/chest wall radiotherapy, whole breast/chest wall radiotherapy including regional nodal irradiation (RNI) and partial breast irradiation (PBI), for the most relevant fractionation schedules that have been introduced recently. This narrative review provides a comprehensive summary that may help to harmonize treatment planning strategies.

Fat necrosis after accelerated partial breast irradiation or hypofractionated whole breast irradiation: A case-control study.

PURPOSE: This study aimed to compare the incidence of fat necrosis after accelerated partial breast irradiation (APBI) vs hypofractionated whole breast irradiation (WBI) in patients with early-stage breast cancer. MATERIALS AND METHODS: Data from early-stage breast cancer patients who underwent breast-conserving surgery and adjuvant radiotherapy between 2009 and 2022 were retrospectively collected. Radiation therapy consisted of APBI of 30 Gy in 5 daily fractions (Fx) (delivered in one week, consecutively) to the tumour bed or WBI (42.4 Gy in 16 Fx). Reports on fat necrosis were extracted from yearly mammograms and breast ultrasound imaging. The primary endpoint was the incidence of radiologically detected fat necrosis. RESULTS: A total of 536 patients were included among the APBI and WBI cohorts, with 268 and 268 patients respectively. The three-year Kaplan-Meier actuarial rate of fat necrosis was 32.8% (95% CI: 30.0% - 35.6%) for APBI and 22.3% (95% CI: 19.7% - 24.9%) for WBI patients. Univariate Kaplan-Meier survival analysis revealed a Hazard Ratio of 1.6 [95% CI: 1.1 - 2.2; p = 0.0055] for the fat necrosis rate within the APBI group compared to WBI. Multivariate Cox proportional hazard regression confirmed significant associations between fat necrosis and APBI (HR = 2.2 95% CI: 1.2 - 4.0; p = 0.01). CONCLUSIONS: The occurrence of radiologically diagnosed fat necrosis was higher in the APBI group compared to the WBI. Further investigations aiming to identify a lower-dose schedule with comparable efficacy to 30 Gy in 5 Fx but fewer toxicities, particularly for high-risk patients, are warranted.

Axillary Management in Breast Cancer Patients Undergoing Upfront Surgery: Results from a Nationwide Survey on Behalf of the Clinical Oncology Breast Cancer Group (COBCG) and the Breast Cancer Study Group of the Italian Association of Radiotherapy and Clinical Oncology (AIRO).

BACKGROUND: We assessed the current practice concerning the axillary management of breast cancer (BC) patients undergoing upfront surgery among radiation oncologists (ROs) practising in Italy. METHODS: An online survey via SurveyMonkey (including 21 questions) was distributed amongst ROs in Italy through personal contacts and the Italian Association for Radiotherapy and Clinical Oncology (AIRO) network from August to September 2022. We particularly focused on the emerging omission of axillary lymph node dissection (ALND) in the presence of 1-2 sentinel node-positive patients and the consequent change in the role of regional nodal irradiation (RNI). RESULTS: A total of 101/195 (51% response rate) Italian Radiotherapy Cancer Care Centres answered the survey. With respect to patients with 1-2 sentinel node-positive, the relative proportion of respondents that offer patients ALND a) always, b) only in selected cases, and c) never was 37.6%, 60.4%, and 2.0%, respectively, with no significant geographical (North vs. Centre-South Italy; p = 0.92) or institutional (Academic vs. non-Academic; p = 0.49) differences. Radiation therapy indications varied widely in patients who did not undergo ALND. Among these, about a third of the respondents (17/56, 30.4%) stated that RNI was constantly performed. On the other hand, half of the respondents offered RNI in selected cases, stating that an unfavourable biologic tumour profile and extracapsular nodal extension were considered drivers of their decision. CONCLUSIONS: Results of the present survey show the variability of axillary management offered in clinical practice for BC patients undergoing conserving surgery upfront in Italy. Analysis of these attitudes may trigger the modification of some clinical approaches through multidisciplinary collaboration and create the background for future clinical investigations.

One-week external beam partial breast irradiation: survival and toxicity outcomes.

PURPOSE: According to ASTRO and ESTRO guidelines, external beam Partial Breast Irradiation (PBI) is a valid option for early-stage breast cancer patients. Nevertheless, there is lack of consensus about the best treatment schedule. METHODS: We retrospectively analysed data of female patients treated at our institution from 2013 to 2022 with adjuvant "one-week" partial breast irradiation. Clinical Target Volume (CTV) was an isotropic expansion of 15 mm from the tumour bed (identified as the breast tissue between surgical clips). The treatment schedule was 30 Gy delivered with Volumetric Modulated Arc Therapy in 5 daily fractions. The primary endpoint was Local Control (LC). Disease-Free Survival (DFS), Overall Survival (OS) and safety were secondary endpoints. RESULTS: Three hundred and forty-four patients with a median age of 69 (33-87) years were included in the study. After a median follow-up of 34 (7-105) months, 7 patients (2.0%) developed a local recurrence. Three-year LC, DFS and OS actuarial rates were 97.5% (95% CI 96.2%-98.8%), 95.7% (95% CI 94.2%-97.2%), and 96.9% (95% CI 95.7%-98.1%), respectively. Ten (2.9%) patients experienced grade 2 late toxicities. Five (1.5%) patients reported late cardiac major events. Three (0.9%) late pulmonary toxicities were detected. One hundred and five (30.5%) patients reported fat necrosis. Good or excellent cosmetic evaluation following the Harvard Scale was reported in 252 (96.9%) cases by the physicians, while in 241 (89.2%) cases by the patients. CONCLUSION: "One-week" PBI is effective and safe, and this schedule is a valid option for highly selected early breast cancer patients.

Technological advancements and future perspectives in breast cancer radiation therapy.

INTRODUCTION: Breast cancer is still one of the most common tumors worldwide and radiation therapy has a central role in the oncological pathway. Several technological options are now available with the aim to improve therapeutic index, target definition, and patient selection. AREAS COVERED: In this review, we summarize current available technologies in the management of breast cancer. These advances can support the prescription of postoperative partial breast cancer treatment and preoperative stereotactic partial breast irradiation. Moreover, image-guided radiotherapy is crucial for high-quality radiation treatments. Additionally, the recent development of hybrid magnetic resonance linear accelerator can impact target volume outline procedure, adaptive planning and radiomics. Finally, artificial intelligence represents the new frontier in medicine, supporting clinicians in target definition, patient selection, and treatment planning. EXPERT OPINION: In patients with breast cancer the overall level of evidence about new technologies is still low even if some advances are potentially very interesting to further development.

Overview of the synergistic use of radiotherapy and immunotherapy in cancer treatment: current challenges and scopes of improvement.

INTRODUCTION: Oncological treatments are changing rapidly due to the advent of several targeted anticancer drugs and regimens. The primary new area of research in oncological medicine is the implementation of a combination of novel therapies and standard care. In this scenario, radioimmunotherapy is one of the most promising fields, as proven by the exponential growth of publications in this context during the last decade. AREAS COVERED: This review provides an overview of the synergistic use of radiotherapy and immunotherapy and addresses questions like the importance of this subject, aspects clinicians look for in patients to administer this combined therapy, individuals who would benefit the most from this treatment, how to achieve abscopal effect and when does radio-immunotherapy become standard clinical practice. EXPERT OPINION: Answers to these queries generate further issues that need to be addressed and solved. The abscopal and bystander effects are not utopia, rather physiological phenomena that occur in our bodies. Nevertheless, substantial evidence regarding the combination of radioimmunotherapy is lacking. In conclusion, joining forces and finding answers to all these open questions is of paramount importance.

Moving HER2-low breast cancer predictive and prognostic data from clinical trials into the real world.

Background: Previous data, mostly from clinical trials, reported that HER2-low status is associated with low pathological complete response (pCR), and favourable prognosis. Since these findings suggest the existence of an additional breast cancer subtype, we questioned if the predictive/prognostic value of HER2-low was also relevant in the real world. Methods: Data from non-metastatic breast cancer patients treated with neoadjuvant chemotherapy and surgery (2009-2020) were retrieved from our institutional prospectively-maintained registry. Univariable and multivariable logistic models were implemented to study the association between pCR and baseline HER2 status. Univariable analysis of disease-free survival (DFS) was performed through Kaplan-Meier survival curves and log-rank tests. Results: Starting from a total of 790 consecutive cases, we identified 444 newly-diagnosed breast cancer patients featuring HER2 immunohistochemistry (IHC) 0 (HER2-0, n = 109), and 1 + or IHC 2+/in situ hybridization negative (HER2-low, n = 335) receiving anthracycline and taxane-based regimens in 88.9% of cases. Most of the patients were diagnosed with stage II (67.3%) and there was no difference of disease presentation according to HER2-status. pCR was attained by 71 (16.0%) patients and was significantly associated with increased DFS (p = 0.031). Compared to HER2-0, HER2-low cases were more likely hormone receptor-positive (81.2% vs. 43.1%, p < 0.001), well-differentiated (47.5% vs. 26.6%, p = 0.001), less proliferative (21.5% vs. 8.3%, p = 0.001) and less responsive to treatment (pCR 11.6% vs. 29.4%, p < 0.0001). There was no difference in DFS according to HER2 status, though hormone-receptor (HR) negative/HER2-low cases tended to have a worse prognosis compared to HR-negative/HER2-0. By pCR achievement, 3-years DFS was 87.5.% (75.1-100%) vs. 71.6% (65.9-77.8%) (p = 0.161) in HER2-low and 89.1% (75.8-100%) vs. 72.1% (59.7-87.0%) (p = 0.092) in HER2-0. Conclusion: Our real-world data show that HER2-low breast cancer patients represent roughly a half of the cases treated with neoadjuvant therapy, and have poor treatment response. In absence of pCR, HER2-low breast cancer patients have a dismal prognosis, especially when primary tumor hormone receptor status is negative. Studies are therefore needed to define the biology of these tumors for new therapeutic targets and to incorporate HER2-targeting agents in early-stage treatment.

Hypofractionated proton therapy in breast cancer: where are we? A critical review of the literature.

PURPOSE: To critically review available literature on hypofractionated (≥ 3 Gy/fraction) proton therapy (PT) for breast cancer (BCa). METHODS: A systematic screening of the literature was performed in April 2021 in compliance with the preferred reporting items for systematic reviews and meta-analyses recommendations. All full-text publication written in English were considered eligible. Acute and late toxicities, oncological outcomes and dosimetric features were considered for the analysis. RESULTS: Twelve publications met the inclusion criteria; all studies but one focused on accelerated partial breast irradiation (APBI). Eleven works considered post-operative patients, one referred to ABPI as a curative-intent modality. The dosimetric profile of PT compared favorably with both photon-based 3D conformal and intensity-modulated techniques, while a more extended follow-up is warranted to fully assess both the long-term toxicities and the non-inferiority of oncological outcomes. CONCLUSION: Our work shows that results on PT for BCa are currently only available for APBI applications, with dosimetric analyses demonstrating a clear advantage over both 3D conformal and intensity modulated X-rays techniques, especially when ≥ 2 treatment fields were used. However, further evidence is needed to define whether such theoretical benefit translates into clinical improvements, especially in the long-term.

Hypofractionated whole-breast radiotherapy in large breast size patients: is it really a resolved issue?

The purpose of this study was to evaluate the impact of breast size on acute and late side effects in breast cancer (BC) patients treated with hypofractionated radiotherapy (Hypo-RT). In this study we analyzed patients over 50 years with a diagnosis of early BC, candidate for Hypo-RT after conservative surgery. Acute and late skin toxicities were evaluated in accordance with the RTOG scale. Multivariable logistic analysis was performed using dosimetric/anatomical factors resulted associated with toxicity outcome in univariable analysis. Among patients treated between 2009 and 2015, 425 had at least 5 years of follow-up. At RT end, acute skin toxicity ≥ G2 and edema ≥ G2 occurred in 88 (20.7%) and 4 (0.9%) patients, respectively. The multivariable analysis showed association of skin toxicity with boost administration (p < 0.01), treated skin area (TSA) receiving more than 20 Gy (p = 0.027) and breast volume receiving 105% of the prescription dose (V105%) (p = 0.016), but not breast size. At 5 years after RT, fibrosis ≥ G1 occurred in 89 (20.9%) patients and edema ≥ G1 in 36 (8.5%) patients. Fibrosis resulted associated with breast volume ≥ 1000 cm3 (p = 0.04) and hypertension (p = 0.04). As for edema, multivariable logistic analysis showed a correlation with hypertension and logarithm of age, but not with boost administration. Breast volume had an unclear impact (p = 0.055). A recurrent association was found between acute and late toxicities and breast V105%, which is correlated with breast size. This may suggest that a more homogenous RT technique may be preferred for patients with larger breast size.

Implant risk failure in patients undergoing postmastectomy 3-week hypofractionated radiotherapy after immediate reconstruction.

AIM: To evaluate reconstruction failure (RF) rate in patients receiving implant-based immediate breast reconstruction (IBR) and hypofractionated (HF) postmastectomy radiation therapy (PMRT). MATERIALS AND METHODS: Stage II-III breast cancer patients, treated with HF-PMRT using intensity modulated radiotherapy were stratified in two groups according to IBR: single-stage direct-to-implant (DTI-group) and two-stage expander and implant (TE/I-group). Irradiated patients were matched with non-irradiated ones who underwent the same IBR during the same period. Prescription dose was 40.05 Gy/15 fractions to chest wall and infra/supraclavicular nodal region. Primary endpoint was RF defined as the need of major revisional surgery (MaRS) for implant removal or conversion to autologous reconstruction. Secondary endpoint was the rate of minor revisional surgeries (MiRS) including implant repositioning or substitution with another implant. RESULTS: One hundred and seven irradiated patients (62 in TE/I-group, 45 in DTI-group) were matched with 107 non-irradiated subjects. Median follow-up was 4.2 years (0.1-6.1) In the TE/I setting, MaRS was performed in 8/62 irradiated patients (12.9%) of the irradiated TE/I group compared to 1/62 (1.6%) non-irradiated subjects (p = 0.015). In the DTI setting, MaRs occurred in 3/45 irradiated patients (6.7%) compared to 1/45 non-irradiated ones (2.2%) (p = 0.35). Overall MaRS rate was 10.3% in the irradiated group. MiRS was performed in 35.6% and 31.1% of the irradiated and non-irradiated DTI-groups (p = 0.65), respectively, and in 12.9% and 8.1% of the irradiated and non-irradiated TE/I groups (p = 0.38), respectively. CONCLUSIONS: Compared to the non-irradiated counterparts, the TE/I group showed higher rate of RF, while no statistically significant difference was observed for the DTI group. The use of hypofractionation and IMRT to implant-based IBR did not seem to increase the risk of RF which appeared to be in line with the literature.

Predictors of positive axillary non-sentinel lymph nodes in breast cancer patients with positive sentinel lymph node biopsy after neoadjuvant systemic therapy.

AIM: To assess the rate of positive non-sentinel lymph nodes (non-SLNs) after neoadjuvant systemic therapy (NAST) in breast cancer (BC) following positive sentinel lymph node biopsy (SLNB). MATERIALS AND METHODS: From institutional database, 265 consecutive patients receiving NAST for cT1-3, any N, M0 BC between 2001 and 2018 were identified. Patients presented clinically negative axilla before surgery and were candidate for SLNB. Following metastatic SLNB, completion axillary lymph node dissection (AxLND) was performed. Non-SLNs rate was investigated using multivariate (MV) logistic regression models. The distribution of non-SLNs across the axilla was observed. RESULTS: Positive non-SLNs were found in 62.3% of cases and showed no correlation with SLN metastasis size. At MV, statistically significant variables associated with non-SLNs were older age (p = 0.025), clinically positive lymph nodes (p = 0.002), SLN extracapsular extension (ECE, p = 0.001), and higher ratio of positive SLNs/total SLNs (p = 0.016). ECE and higher nodal ratio were independent predictors of III axillary level positivity. By categorizing patients in intermediate- and high-risk groups using the study variables, positive non-SLNs were found in the range of 23-56% across the three axillary levels, rates which did not support radiotherapy volume de-escalation. The III axillary level lower involvement (6.3%) was better identified with the RAPCHEM trial criteria based on the ypN status after AxLND. CONCLUSIONS: Involved non-SLNs rate following positive SLNB after NAST is nearly double the rate observed after primary surgery, supporting some intervention on the axilla. If AxLND is limited to I and II level, the involvement of the III level up to 31% of the cases seems to require some additional treatment, while the omission in selected cases needs further investigation.

Breast cancer patient perspective on opportunities and challenges of a genetic test aimed to predict radio-induced side effects before treatment: Analysis of the Italian branch of the REQUITE project.

AIM: To explore breast cancer patient's perspective on future genetic testing for prediction of toxicity after breast radiotherapy (RT). MATERIALS AND METHODS: The study involved patient enrolled in the Italian branch of the REQUITE project conducted at the National Cancer Institute in Milan. Semi-structured interviews were conducted within one month from the end of radiotherapy treatment by two radiation oncologists and a radiotherapy technician previously trained by a clinical psychologist with experience in the oncology field. Semi-structured interviews are characterized by a set of pre-defined questions and developed ad hoc by researchers in Leicester within the REQUITE project. The interview questions investigated interest in undergoing the genetic test and expectations on its usefulness and disadvantages. RESULTS: Eighteen interviews were conducted and analysed. Forty-five initial codes were combined into nine themes which were then clustered in two main macro-areas (i) Opportunities and (ii) Challenges. Overall, all patients understand the aim of the genetic test and considered its intrinsic opportunity to make the physician more confident with the treatment. Regarding side effects, most of patients felt prepared to RT but not without fear. Many women considered important to have the largest and reliable information, also about negative experiences. Prevailing emotions were anxiety and fear but not connected to genetic test's result. CONCLUSIONS: A genetic test could be an opportunity because generate knowledge and give patients a dynamic role in the decision-making approach. Prediction of single patient radiosensitivity before RT could prompt suggestion to entail a more and more tailored radiation treatment in the era of personalized approach.

Comparing hypofractionated and conventionally fractionated whole breast irradiation for patients with ductal carcinoma in situ after breast conservation: a propensity score-matched analysis from a national multicenter cohort (COBCG-02 study).

BACKGROUND AND PURPOSE: Randomized trials confirmed the efficacy and the safety of hypofractionated whole breast irradiation (HF-WBI) in patients with early-stage breast cancer. However, the role of HF-WBI in patients with DCIS after breast conserving surgery has not yet been clearly established in prospective randomized trials. The aim of this study was to evaluate if HF-WBI can be considered comparable to conventionally fractionated (CF)-WBI in DCIS patients. MATERIALS AND METHODS: The analysis included DCIS patients from four Italian centers treated with CF-WBI 50 Gy/25 fractions or HFRT 40.5 Gy/15 fractions, without tumor bed boost. A propensity score matching (PSM) analysis was performed using a logistic regression that considered age, grading, presence of necrosis, resection margin status and adjuvant endocrine therapy. RESULTS: Five hundred twenty-seven patients was included (367 in the CF-WBI-group and 160 in the HR-WBI group). After 1:1 matching, 101 patients were allocated to the CF-WBI-group and 104 to the HF-WBI group. No correlation was observed between the type of RT schedule and LRFS (HR 1.68, 95% CI 0.82-3.45; p = 0.152). After PSM, no statistical difference was observed between the two RT group (HR 1.11, 95% CI 0.40-3.04; p = 0.833), with 3- and 5-years LRFS rates of 100% and 97.9% for CF-WBI and 95.6% and 94% for HF-WBI. CONCLUSION: A short course of radiation therapy seems to be comparable to CF-WBI in terms of clinical outcomes. These data support the use of hypofractionated schedules in DCIS patients, but considering the remaining uncertainties.

Long-term standard sentinel node biopsy after neoadjuvant treatment in breast cancer: a single institution ten-year follow-up.

INTRODUCTION: In patients with positive lymph nodes (cN+) prior to neoadjuvant treatment (NAT), which convert to a clinically negative axilla (cN0) after treatment, the use of sentinel node biopsy (SNB) is still debatable, since the false-negative rate (FNR) is significantly high (12.6-14.2%). The objective of this retrospective mono-institutional study, with a long follow-up, aimed to evaluate the outcome in patients undergoing NAT who remained or converted to cN0 and received SNB independent of target axillary dissection (TAD) or the removal of at least 3 sentinel nodes (SNs). METHODS: This study analyzed 688 consecutive cT1-3, cN0/1/2 patients, operated at the European Institute of Oncology, Milan, from 2000 to 2015 who became or remained cN0 after NAT and underwent SNB with a least one SN found. Axillary dissection (AD) was not performed if the SN was negative. Nodal radiotherapy (RT) was not mandatory. RESULTS: Axillary failure occurred in 1.8% of the initially cN1/2 patients and in 1.5% of the initially cN0 patients. After a median follow-up of 9.2 years (IQR 5.3-12.3), the 5- and 10-year overall survival (OS) were 91.3% (95% CI, 88.8-93.2) and 81.0% (95% CI, 77.2-84.2) in the whole cohort, 92.0% (95% CI, 89.0-94.2) and 81.5% (95% CI, 76.9-85.2) in those initially cN0, 89.8% (95% CI, 85.0-93.2) and 80.1% (95% CI, 72.8-85.7) in those initially cN1/2. CONCLUSION: The 10-year follow-up confirmed our preliminary data that the use of standard SNB is acceptable in cN1/2 patients who become cN0 after NAT and will not translate into a worse outcome.

Phase II prospective trial "Give Me Five" short-term high precision radiotherapy for early prostate cancer with simultaneous boost to the dominant intraprostatic lesion: the impact of toxicity on quality of life (AIRC IG-13218).

As part of the AIRC IG-13218 (NCT01913717), we analyzed data from patients with low- and intermediate-risk prostate cancer treated with extreme hypofractionated radiotherapy (RT) and simultaneous boost to the intraprostatic lesion. The aim of the study is to identify clinically meaningful information through the analysis of validated questionnaires testing gastrointestinal (GI) and genitourinary (GU) RT-related toxicity and their impact on quality of life (QoL). At the end of RT treatment, clinical assessment and prostate-specific antigen (PSA) measurements were performed every 3 months for at least 2 years and GI and GU toxicities were evaluated contextually. QoL of enrolled patients was assessed by International Prostate Symptoms score (IPSS), European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30), EORTC QLQ prostate specific (QLQ-PR25), and sexual activity by International Index of Erectile Function (IIEF-5). Patients' score changes were calculated at the end of RT, at one month after RT and at 12 and 24 months. Sixty-five prospectively enrolled patients were analyzed. Extensive analysis of different QoL assessments showed that patients' tolerance was satisfactory across all the considered time points, with no statistically significant change of QoL from baseline compared to that before RT. Overall survival and biochemical progression-free survival at 2-years were of 98% and 97%, respectively. Despite the toxicity of extreme hypofractionation was low and tumor control was encouraging, a longer follow-up is necessary to confirm our findings. The increasing dose to the dominant intraprostatic lesion does not worsen the RT toxicity and consequently does not affect patients' QoL, thus questioning the possibility of an even more escalated treatment.

Hypofractionated irradiation in 794 elderly breast cancer patients: An observational study.

To assess the efficacy, and the acute and late toxicity of hypofractionated radiotherapy (Hypo-RT), and the impact of age and comorbidities on disease progression and death in elderly breast cancer (BC) patients. Women aged ≥65 years who received Hypo-RT (42.4 Gy in 16 fractions, plus a boost for high-risk patients) were considered for the present analysis. Competing risk analysis was used to estimate the 5-year cumulative incidence of BC progression and BC-related death, calculating the adjusted subhazard ratios (SHR) with 95% confidence intervals (95%CI) in relation to age, hypertension-augmented Charlson Comorbidity Index (hCCI), tumor characteristics, and chemotherapy. The sample included 794 patients with a median age of 74 years (range 65-91 years). At the baseline, 70% of these patients had at least one comorbidity. With a median follow-up of 48.3 months, the 5-year cumulative incidence of BC progression and BC-related death was 6.7% (95%CI 4.8%-9.2%) and 2.3% (95%CI 1.2%-3.9%), respectively. Old age (≥80 years) and a high burden of comorbidity (hCCI ≥ 2) were independently associated with BC progression. Hypo-RT is safe in elderly BC patients, but age and comorbidities influence BC progression. Further studies are warranted.

HALFMOON TomoTherapy (Helical ALtered Fractionation for iMplant partial OmissiON): implant-sparing post-mastectomy radiotherapy reshaping the clinical target volume in the reconstructed breast.

PURPOSE: To report the dosimetric feasibility of the radiation technique HALFMOON (Helical ALtered Fractionation for iMplant partial OmissiON) for post-mastectomy radiation therapy (PMRT) in intermediate-high-risk breast cancer patients with implant-based immediate breast reconstruction, where the clinical target volume (CTV) does not include the whole implant (implant-sparing approach). METHODS: In the HALFMOON technique, the CTV consisted of skin, subcutaneous tissues, and pectoralis major muscle, excluding the implant, chest wall muscles, and rib plane. The HALFMOON plans were compared with conventionally contoured CTV plans, in which the whole implant, chest wall muscles, and ribs plane were included in the CTV, in a ratio 1:3. All patients underwent hypofractionated treatment of 40.05 Gy/15 fractions, using helical Tomotherapy®. RESULTS: Eighteen patients undergoing HALFMOON technique were compared to 54 subjects treated with conventionally contoured CTV plans. No difference was found in the planning target volume coverage between the two groups. Conversely, a statistically relevant dose reduction in HALFMOON patients was observed for ipsilateral lung (D15%, p < 0.0001; D20%, p < 0.0001; D35%, p = 0.003), contralateral lung (D20%, p = 0.048), contralateral breast (D15%, p = 0.031; D20%, p = 0.047), and stomach (Dmean, p = 0.011). Regarding the implant, V90% and D50% decreased by 46% and 8%, respectively, in the HALFMOON plans (p < 0.0001). CONCLUSION: The HALFMOON approach is technically feasible and resulted in high-dose conformity of the target with a significant reduction of radiation dose delivered to implant and other organs. A clinical study is needed to assess the impact on reconstruction cosmetic outcome and local control.

Interobserver variability (between radiation oncologist and radiation therapist) in tumor bed contouring after breast-conserving surgery.

PURPOSE: To examine interobserver variability between the radiation oncologist (RTO) and the radiation therapist (RTT) in delineating the tumor bed (TB) in early breast cancer (BC). METHODS: We retrospectively analyzed patients who received a radiotherapy boost to the TB. In a first group, the clinical target volume (CTV) for the boost was the surgical bed, defined by using surgical clips. In a second group, the CTV was defined by identifying a seroma cavity or a metallic find on the scar. These contours were compared in terms of volume, number of slices, and Dice similarity coefficient (DSC). RESULTS: Forty patients were assessed: 20 had surgical clips (group 1) while the other 20 had none (group 2). There was no difference in the number of slices contoured by the 2 operators for group 1, but a statistically significant difference emerged in the volumes: the RTT identified a TB that was a mean 45% smaller than the one identified by the RTO. Random differences were found between the 2 operators for group 2. The TBs delineated for this group were significantly larger (P<0.05) than those identified by the RTT for group 1. The mean Dice value between the RTO's and the RTT's TBs was 0.69±0.07 (range 0.53-0.81) for group 1 and 0.37±0.18 (range 0-0.58) for group 2 (P<0.05). CONCLUSIONS: This study showed that the use of clips coincided with less interoperator variability. With appropriate training, the RTT may play an important part in the multidisciplinary radiotherapy team.

Radiotherapy with the anti-programmed cell death ligand-1 immune checkpoint blocker avelumab: acute toxicities in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is clinically the most aggressive breast cancer (BC) subtype. There is an urgent need for effective therapies for patients with TNBC. Recent findings confirm the important role of factors related to the immune system in the clinical outcome and response to treatment of TNBC patients. Avelumab selectively binds to PDL1, and competitively blocks its interaction with anti-programmed death 1 (anti-PD-1) antibodies. Unlike anti-PD-1 antibodies, which target T-cells, avelumab targets tumor cells, and is therefore expected to have fewer side effects, including a lower risk of Immune-Related Adverse Events (irAEs). Uncertainties remain regarding a potential synergy resulting in increased toxicities by combining radiotherapy and immune-checkpoint inhibitors (ICIs). Effects of concomitant ICIs with thoracic radiotherapy on pulmonary toxicities is not currently known. There are no published data available on the effects of combining anti-PD-L1 with adjuvant radiotherapy (RT) for BC in a clinical setting. We reported a preliminary experience on the first patient treated at the National Cancer Institute of Milan with the association of avelumab and concomitantly RT for TNBC.