Concurrent Use of Abemaciclib and Radiotherapy in Metastatic Breast Cancer Patients: A Single-Center Experience.

INTRODUCTION: There is little evidence regarding the safety and efficacy of the combination of abemaciclib plus radiotherapy (RT). The majority of studies investigated the combination of RT with palbociclib or ribociclib reporting that hematological toxicity is common. Given the unique toxicity profile of abemaciclib with greater gastrointestinal toxicity compared to hematological toxicity, we wanted to evaluate the toxicity of the combination with RT in metastatic breast cancer (BC) patients. METHODS: Patients with histologically proven metastatic or locally advanced BC treated with RT and concurrent abemaciclib were selected. Toxicity was assessed according to the NCI-CTCAE V4.0. RESULTS: Thirty-two metastatic sites were treated in 19 patients and analyzed. All patients received abemaciclib during the RT course. A total of 68% of patients received a full dose of abemaciclib during RT. Also, 71.9% of patients received a palliative intent (median dose = 30 Gy, range = 8-30 Gy), and 26.3% were treated for 9 oligo-metastatic or oligo-progressive sites of disease with stereotactic body RT (median dose = 30 Gy, range 21-30 Gy, given in 3-5 fractions). Overall, the rate of G3 toxicity was 15.7%. The rate of G3 hematological toxicity was 10.6% (2/19 patients, one G3 neutropenia and one G3 anemia). No patient presented diarrhea, including those treated for RT sites close to the bowel. One patient developed G3 skin toxicity. Pain significantly improved after RT (mean value NRS pre-RT = 3.9, SD = 3.07; mean value NRS after RT = 0.9, SD = 0.46; p < 0.0001). CONCLUSION: Abemaciclib and concomitant RT seem well tolerated showing acceptable toxicity.

Stereotactic or conventional radiotherapy for macroscopic prostate bed recurrence: a propensity score analysis.

PURPOSE: To assess outcomes between salvage radiation therapy (SRT) with curative intent and stereotactic radiotherapy for macroscopic prostate recurrence (SSRT) after radical prostatectomy (RP). In order to compare these two different options, we compared their outcomes with a propensity score-based matched analysis. METHODS: Data from 185 patients in seven Italian centres treated for macroscopic prostate bed recurrence after RP were retrospectively collected. To make a comparison between the two treatment groups, propensity matching was applied to create comparable cohorts. RESULTS: After matching, 90 patients in the SRT and SSRT groups were selected (45 in each arm). Kaplan-Meier analysis did not show any significant differences in terms of BRFS and PFS between matched populations (p = 0.08 and p = 0.8, respectively). Multivariate models show that treatment was not associated with BRFS, neither in the whole or matched cohort, with HR of 2.15 (95%CI 0.63-7.25, p = 0.21) and 2.65 (95%CI 0.59-11.97, p = 0.21), respectively. In the matched cohort, lower rate of toxicity was confirmed for patients undergoing SSRT, with acute GI and GU adverse events reported in 4.4 versus 44.4% (p < 0.001) and 28.9 versus 46.7% (p = 0.08) of patients, and late GI and GU adverse events reported in 0 versus 13.3% (p = 0.04) and 6.7 versus 22.2% (p = 0.03) of patients, respectively. CONCLUSION: Considering the favourable therapeutic ratio of this approach and the lower number of fractions needed, SSRT should be considered as an attractive alternative to conventional SRT in this setting.

Sequential chemo-hypofractionated RT versus concurrent standard CRT for locally advanced NSCLC: GRADE recommendation by the Italian Association of Radiotherapy and Clinical Oncology (AIRO).

INTRODUCTION: Almost 30% of non-small cell lung cancer (NSCLC) patients have locally advanced-stage disease. In this setting, definitive radiotherapy concurrent to chemotherapy plus adjuvant immunotherapy (cCRT + IO) is the standard of care, although only 40% of these patients are eligible for this approach. AIMS: A comparison between cCRT and hypofractionated radiotherapy regimens (hypo-fx RT) with the addition of sequential chemotherapy (sCHT) could be useful for future combinations with immunotherapy. We developed a recommendation about the clinical question of whether CHT and moderately hypo-fx RT are comparable to cCRT for locally advanced NSCLC MATERIALS AND METHODS: The panel used GRADE methodology and the Evidence to Decision (EtD) framework. After a systematic literature search, five studies were eligible. We identified the following outcomes: progression-free survival (PFS), overall survival (OS), freedom from locoregional recurrence (FFLR), deterioration of quality of life (QoL), treatment-related deaths, severe G3-G4 toxicity, late pulmonary toxicity G3-G4, and acute esophageal toxicity G3-G4. RESULTS: The probability of OS and G3-G4 late lung toxicity seems to be worse in patients submitted to sCHT and hypo-fx RT. The panel judged unfavorable the balance benefits/harms. CONCLUSIONS: The final recommendation was that sCHT followed by moderately hypo-fx RT should not be considered as an alternative to cCRT in unresectable stage III NSCLC patients.

18F-choline PET/CT driven salvage radiotherapy in prostate cancer patients: up-date analysis with 5-year median follow-up.

PURPOSE: Salvage radiotherapy is generally considered as the standard treatment for biochemical relapse after surgery. Best results have been obtained with a PSA value < 0.5 ng/ml at relapse, while 60-66 Gy is deemed as standard total dose. Modern imaging, as dynamic-18F-choline PET/CT may identify site of recurrence, allowing dose escalation to a biological target volume. METHODS: Hundred and fifty patients showed a local relapse at dynamic-18F-choline PET/CT at time of biochemical recurrence. High-dose salvage radiotherapy was delivered up to total dose of 80 Gy to 18F-choline PET/CT positive area. Toxicity and relapse-free survival were recorded. RESULTS: Median PSA value at the beginning of salvage radiotherapy was 0.47 ng/ml (range 0.2-17.5 ng/ml). One-hundred and thirty nine patients (93%) completed salvage radiotherapy without interruptions. Acute gastrointestinal grade ≥ 2 toxicity was recorded in 13 patients (9%), acute genitourinary grade ≥ 2 toxicity in 2 patients (1.4%). One patient (0.7%) experienced late gastrointestinal grade 4 toxicity and 2 patients (1.4%) late acute genitourinary grade 3 toxicity. With a median follow-up of 63.5 months, 5 and 7-years relapse-free survival were 70% and 60.7%, respectively. CONCLUSION: With a median follow-up of 5 years the present study confirms that high-dose salvage radiotherapy to a biological target volume is feasible, with low rate of late toxicity and promising activity.

Efficacy of a Propolis-Based Syrup (FARINGEL) in Preventing Radiation-Induced Esophagitis in Locally Advanced Lung Cancer.

AIM: To evaluate the efficacy of a propolis-based syrup, FARINGEL®, in preventing radiation-induced esophagitis in locally advanced lung cancer patients. METHODS: Patients were treated with concurrent chemoradiotherapy (CRT) using involved-field radiotherapy (RT). Every patient received FARINGEL at the beginning of CRT until the first follow-up. The data of the study group were compared with the data of a control group treated without the administration of the syrup. RESULTS: Forty-five patients were enrolled. Forty-one (91.1%) completed the protocol and were evaluable for esophagitis. Grade ≥2 toxicity occurred in 9/41 patients (22%). No differences in overall toxicity were detected between the study group and the control group (n = 55, 60.9 vs. 54.5%; p = ns). Grade 2-3 esophagitis was lower in the study group in comparison with the control group (22 and 38%, respectively), but statistical significance was not reached (p = 0.09). However, the onset of grade ≥2 esophagitis was delayed in the study group compared to the control group, occurring at higher doses of RT (41.8 vs. 25.4 Gy; p < 0.001). Furthermore, the mean number of interruption days for esophagitis was lower in the study group than in the control group (0.6 ± 2.0 vs. 2.1 ± 3.6; p = 0.025). CONCLUSION: FARINGEL was well-tolerated and delayed esophagitis that was induced by CRT for locally advanced lung cancer.

GUROPA survey: genito-urinary radiation oncology prescription attitudes.

AIMS: To investigate the role of Radiation Oncology in the management of genito-urinary (GU) cancer excluding prostate and penile cancer. METHODS: The questionnaire was focused on the evaluation of the degree of involvement of radiation oncologists in the work-up of bladder, renal cell carcinoma and testicular cancer (TC). RESULTS: Eighty-eight radiation oncologists completed the survey. The majority (85.4%) of participating radiation oncologists were senior consultants (> 5 years of experience). Sixty-four (73.6%) carried out a multidisciplinary tumor board discussion of GU cases, while 23 (26.4%) did not. Seventy-five percent of responders reported that, every year, visited < 50 GU patients (pts), 18.1% visited 50-100 pts and 6.9% visited > 100 pts. Bladder cancer, curative radiotherapy (RT) as part of trimodality approach was claimed to be adopted in less than 10 cases per year. Regarding renal cell carcinoma (RCC) patients, primary tumor directed RT was adopted only in 8 cases (9.4%) in at least 10 pts per year. Palliative RT was more frequent in RCC (48.2%) in over than 10 pts per year. In case of TC, the prescription of RT was limited (< 10 patients per year) due to the low incidence of disease and recent shift to surveillance as a first option in stage I seminoma. CONCLUSIONS: Our survey showed that radiation oncologists are rarely involved in the decision making strategy of GU cancer, despite many clinical trials support RT use. These patients probably deserve a more uniform approach based on updated, detailed and evidence-based recommendations.

Efficacy of stereotactic body radiotherapy in oligorecurrent and in oligoprogressive prostate cancer: new evidence from a multicentric study.

BACKGROUND: The aim of the present study is to evaluate the impact of metastases-directed stereotactic body radiotherapy in two groups of oligometastatic prostate cancer (PC) patients: oligorecurrent PC and oligoprogressive castration-resistant PC (oligo-CRPC). METHODS: Inclusion criteria of the present multicentre retrospective analysis were: (1) oligorecurrent PC, defined as the presence of 1-3 lesions (bone or nodes) detected with choline positron emission tomography or CT plus bone scan following biochemical recurrence; (2) oligo-CRPC, defined as metastases (bone or nodes) detected after a prostatic-specific antigen rise during androgen deprivation therapy (ADT). Primary end points were: distant progression-free survival (DPFS) and ADT-free survival in oligorecurrent PC patients; DPFS and second-line systemic treatment-free survival in oligo-CRPC patients. RESULTS: About 100 patients with oligorecurrent PC (139 lesions) and 41 with oligo-CRPC (70 lesions), treated between March 2010 and April 2016, were analysed. After a median follow-up of 20.4 months, in the oligorecurrent group 1- and 2-year DPFS were 64.4 and 43%. The rate of LC was 92.8% at 2 years. At a median follow-up of 23.4 months, in the oligo-CRPC group 1- and 2-year DPFS were 43.2 and 21.6%. Limitations include the retrospective design. CONCLUSIONS: Stereotactic body radiotherapy seems to be a useful treatment both for oligorecurrent and oligo-CRPC.

Estimation of patient setup uncertainty using BrainLAB Exatrac X-Ray 6D system in image-guided radiotherapy.

The purpose of this study was to evaluate setup uncertainties for brain sites with ExacTrac X-Ray 6D system and to provide optimal margin guidelines. Fifteen patients with brain tumor were included in this study. Two X-ray images with ExacTrac X-Ray 6D system were used to verify patient position and tumor target localization before each treatment. The 6D fusion software first generates various sets of DRRs with position variations in both three translational and three rotational directions (six degrees of freedom) for the CT images. Setup variations (translation and rotation) after correction were recorded and corrected before treatment. The 3D deviations are expressed as mean ± standard deviation. The random error (Σ(σi)), systematic error (µi), and group systematic error (M(µi)) for the different X-ray were calculated using the definitions of van Herk.(1) Mean setup errors were calculated from X-ray images acquired after all fractions. There is moderate patient-to-patient variation in the vertical direction and small variations in systematic errors and magnitudes of random errors are smaller. The global systematic errors were measured to be less than 2.0 mm in each direction. Random component of all patients are smaller ranging from 0.1-0.3 mm small. The safety margin (SM) to the lateral, is 0.5 mm and 2.6 mm for van Herk(1) and Stroom et al.,(2) respectively, craniocaudal axis is 1.5 mm and 3.4 mm, respectively, and with respect to the antero-posterior axis, 2.3 mm and 3.9 mm. Daily X-ray imaging is essential to compare and assess the accuracy of treatment delivery to different anatomical locations.

The first survey on defensive medicine in radiation oncology.

PURPOSE: Defensive Medicine occurs when doctors order tests, procedures, visits or avoid high-risk patients and procedures, primarily to reduce their exposure to malpractice liability. Some medical specialities are at "high-risk" for legal argument, but no data is actually available for radiation oncology. We present here the first survey of radiation oncologists' views regarding malpractice liability and defensive medicine practice. MATERIALS AND METHODS: A three-page questionnaire was sent to 611 active radiation oncologists, members of the Italian Association of Radiation Oncology (AIRO), with questions pertaining to the incidence, nature and causes in their practice of defensive medicine. RESULTS: A total of 361 questionnaires were completed (59 % feedback). Physicians practise defensive medicine by ordering further imaging studies (39 %) or laboratory tests (35 %), referring patients to consultants (43 %) or prescribing additional medication (35 %). Approximately, 70 % declared that the climate of opinion that exists towards doctors is one of the major issues for practising defensive medicine. CONCLUSION: Although radiation oncology is generally considered a "medium/low risk" speciality for defensive medicine, the present survey reflects a widespread use of this behaviour in daily practice. Investigating which radiation oncologist categories are more prone to defensive medical behaviour can be advantageous for implementing programmes aimed at improving awareness of this phenomenon and to increase good clinical practice.

SBRT: A viable option for treating adrenal gland metastases.

The management strategy of adrenal metastases depends on different clinical situations. Adrenal metastasectomy in selected patients with isolated adrenal metastases is considered the treatment of choice, showing prolonged survival compared to chemotherapy alone. More recently, Stereotactic Body Radiation Therapy (SBRT) has emerged as an alternative local ablative treatment modality although limited data are available on the use of SBRT in treating adrenal gland metastases. Preliminary results are, however, encouraging, especially in selected patients with oligometastatic disease. We herewith review and discuss the potential role of SBRT as a local ablative treatment modality for adrenal metastases.

A clinical score, including biohumoral parameters, is a useful pretest index to discriminate pulmonary infections from radiation damage in chemoradiation-treated lung cancer patients.

To obtain an easy and prompt differential diagnosis between lower airways infections and acute radiation pneumonitis in chemoradiation lung cancer patients. From 303 patients treated, only patients with severe pulmonary symptoms were hospitalized. Clinical and radiation scores were calculated evaluating clinical, biohumoral, dosimetric parameters. Out of 36 patients hospitalized, infections and acute radiation pneumonitis were reported in 66.7% and 33.3%, respectively. Patients with clinical score ≥ 2 had an Odds Ratio of 3.4 (1.4-8.3; p = .006) to have infectious pneumonia, while radiation score was not predictive.

Fractionated stereotactic radiosurgery for patients with brain metastases.

Stereotactic radiosurgery (SRS) delivered in 2-5 fractions (multi-fraction SRS) has been employed in patients with brain metastases as an alternative to single-fraction SRS with the aim to reduce late radiation-induced toxicity while maintaining high local control rate. In the present study we have evaluated the efficacy and toxicity of multi-fraction SRS in patients with 1-3 brain metastases. Between March 2006 and October 2012, 135 patients (63 men and 72 women) with 171 brain metastases have been treated with multi-fraction SRS (3 × 9 Gy or 3 × 12 Gy). At a median follow-up of 11.4 months, 16 lesions recurred locally. The 1- and 2-year local control rates were 88 and 72 %, respectively. The 1- and 2-year survival rates were 57 and 25 %, and respective distant failure rates were 52 and 73 %. Seventy-eight percent of patients succumbed to their extracranial disease and 22 % died of progressive intracranial disease. Multivariate analysis showed that melanoma histology was predictive of local failure (p = 0.02; HR 6.1, 95 % CI 1.5-24). Specifically, the 1-year local control rates were 68 % for melanoma, 92 % for breast carcinoma, and 88 % for NSCLC, respectively. Stable extracranial disease (p = 0.004) and Karnofsky performance status (p = 0.01) were predictive of longer survival. Radiologic changes suggestive of radionecrosis occurred in 12 (7 %) out of 171 lesions, with an actuarial risk of 9 % at 1 year and 17 % at 2 years, respectively. In conclusion, multi-fraction SRS appears to be an effective and safe treatment modality for brain metastases. It may represent an alternative to single-dose SRS for patients with large lesions or lesions located near critical structures.

Surgical De-Escalation for Re-Excision in Patients with a Margin Less Than 2 mm and a Diagnosis of DCIS.

The current surgical guidelines recommend an optimal margin width of 2 mm for the management of patients diagnosed with ductal carcinoma in situ (DCIS). However, there are still many controversies regarding re-excision when the optimal margin criteria are not met in the first resection. The purpose of this study is to understand the importance of surgical margin width, re-excision, and treatments to avoid additional surgery on locoregional recurrence (LRR). The study is retrospective and analyzed surgical margins, adjuvant treatments, re-excision, and LRR in patients with DCIS who underwent breast-conserving surgery (BCS). A total of 197 patients were enrolled. Re-operation for a close margin rate was 13.5%, and the 3-year recurrence was 7.6%. No difference in the LRR was reported among the patients subjected to BCS regardless of the margin width (p = 0.295). The recurrence rate according to margin status was not significant (p = 0.484). Approximately 36.9% (n: 79) patients had resection margins < 2 mm. A sub-analysis of patients with margins < 2 mm showed no difference in the recurrence between the patients treated with a second surgery and those treated with radiation (p = 0.091). The recurrence rate according to margin status in patients with margins < 2 mm was not significant (p = 0.161). The margin was not a predictive factor of LRR p = 0.999. Surgical re-excision should be avoided in patients with a focally positive margin and no evidence of the disease at post-surgical imaging.

Dynomics: A Novel and Promising Approach for Improved Breast Cancer Prognosis Prediction.

Traditional imaging techniques for breast cancer (BC) diagnosis and prediction, such as X-rays and magnetic resonance imaging (MRI), demonstrate varying sensitivity and specificity due to clinical and technological factors. Consequently, positron emission tomography (PET), capable of detecting abnormal metabolic activity, has emerged as a more effective tool, providing critical quantitative and qualitative tumor-related metabolic information. This study leverages a public clinical dataset of dynamic 18F-Fluorothymidine (FLT) PET scans from BC patients, extending conventional static radiomics methods to the time domain-termed as 'Dynomics'. Radiomic features were extracted from both static and dynamic PET images on lesion and reference tissue masks. The extracted features were used to train an XGBoost model for classifying tumor versus reference tissue and complete versus partial responders to neoadjuvant chemotherapy. The results underscored the superiority of dynamic and static radiomics over standard PET imaging, achieving accuracy of 94% in tumor tissue classification. Notably, in predicting BC prognosis, dynomics delivered the highest performance, achieving accuracy of 86%, thereby outperforming both static radiomics and standard PET data. This study illustrates the enhanced clinical utility of dynomics in yielding more precise and reliable information for BC diagnosis and prognosis, paving the way for improved treatment strategies.

nmCRPC, a look in the continuous care of prostate cancer patients: state of art and future perspectives.

Non-metastatic castration resistant prostate cancer (nmCRPC) is a clinical setting defined as confirmed rising levels of PSA in patients treated with ADT but without detectable metastases on conventional imaging with computerized tomography (CT) and technetium-99 m scintigraphy. Men with nmCRPC and a PSA doubling time (PSADT) ≤ 10 months are considered at high risk of rapidly developing metastases with a consequent possible impact on survival. Three recent phase III trials have demonstrated, in this setting, the efficacy of adding a next-generation androgen receptor targeted agent (ARTA) to ADT in respect to ADT only, in delaying the development of metastases (metastasis-free survival, MFS) and prolong overall survival. The magnitude of clinical benefit of these agents was even more meaningful if considering the low incidence of drug related adverse events. Our review described the latest advances in the management of nmCRPC, deriving from the pivotal clinical trials, SPARTAN, PROSPER and ARAMIS, in order to support clinicians to optimally manage these patients. Of note, the emergence of novel, more accurate, next-generation imaging techniques (including Ga PSMA-PET/CT), as well as eventual future tumor biomarkers, is modifying the entity and definition of the nmCRPC setting, with a consequent impact on patient's diagnosis and management.

Preventing Cardiotoxicity in Personalized Breast Irradiation.

BACKGROUND: This study aims to assess the benefit of a deep inspiration breath hold (DIBH) over the standard irradiation technique, and eventually to identify anatomical and/or treatment preplanning characteristics correlated with the LAD dose. METHODS: Patients with left-sided breast cancer undergoing whole breast radiotherapy with DIBH were analyzed. All patients included in the analysis had plans in DIBH and free-breathing (FB). Receiving operating characteristics (ROC analysis) were used to identify the cut-off point of parameters to predict the LAD maximum dose > 10 Gy and LAD mean dose > 4 Gy, and the areas under the curve (AUCs) were computed. Post-test probability has been performed to evaluate the effect of parameters' combination. RESULTS: One hundred ninety-seven patients were analyzed. The LAD dose was significantly reduced in DIBH plans with the maximum and mean dose reduced by 31.7% (mean value 3.5 Gy vs. 4.8 Gy, p ≤ 0.001) and 28.1% (mean value 8.2 Gy vs. 12.8 Gy, p ≤ 0.001) in DIBH plans compared to FB plans. The strongest predictor of the LAD dose (maximum > 10 Gy and mean > 4 Gy) was the minimum distance of LAD from tangent open fields. Other parameters were lung volume and heart volume (LAD Dmax > 10 Gy) and lung volume, heart volume, and breast separation (LAD Dmean > 4 Gy). CONCLUSION: The dosimetric advantage of DIBH is clear in all patients and DIBH should always be preferred.

V5 and High Sensitivity Cardiac Troponin T for Early Detection of Cardiac Toxicity During Left Breast Cancer Irradiation.

BACKGROUND/AIM: The high sensitivity cardiac troponin T (Hs-cTnT) is a myocardial damage biomarker that could have a predictive value in patients who undergo radiotherapy for left sided breast cancer. The aim of this study was to evaluate the early effect of left whole breast radiotherapy (WB-RT) on serum Hs-cTnT levels and its correlation with pre-existing factors. PATIENTS AND METHODS: The study was conducted from December 2017 to May 2018. Forty-five patients with early stage left-sided breast cancer who received adjuvant breast hypofractionated RT without prior chemotherapy were included. Serum levels of Hs-cTnT were obtained before, weekly during RT, and within one week after the end of treatment. Considering the physiological variations of serum levels, an increase in Hs-cTnT (∆Hs-cTnT) of more than 30% from the baseline value was chosen as a threshold. The main cardiovascular risk factors were recorded. Dose volume histograms (DVHs) were used to provide a quantitative analysis for the whole heart, left ventricle, and left anterior descending artery (LAD). RESULTS: Twelve of 45 patients (26.6%) showed a ∆Hs-cTnT ≥30%. The maximum Hs-cTnT level was recorded in the last week of treatment. ∆Hs-cTnT was strongly associated with heart V5 (p=0.05) and hypertension (p=0.05). Multivariate analysis confirmed the importance of the heart V5 and correlated with ∆Hs-cTnT. CONCLUSION: The increase in Hs-cTnT serum levels during adjuvant WB-RT suggested a correlation with the cardiac radiation dose in chemotherapy-naive breast cancer patients. A longer follow-up is needed to correlate Hs-cTnT values with cardiac events.

Matching BRCA and prostate cancer in a public health system: Report of the Italian Society for Uro-Oncology (SIUrO) consensus project.

The recent approval of PARP inhibitors for the treatment of metastatic -castration-resistant prostate cancer (mCRPC) patients with BRCA mutations firstly introduced the possibility of proposing a targeted treatment in this disease. However, the availability of this therapeutic option raises a number of questions concerning the management of prostate cancer in everyday clinical practice: the timing and method of detecting BRCA mutations, the therapeutic implications of the detection, and the screening of the members of the family of a prostate cancer patient with a BRCA alteration. These challenging issues led the Italian Society for Uro-Oncology (SIUrO) to organise a Consensus Conference aimed to develop suggestions capable of supporting clinicians managing prostate cancer patients. The present paper described the development of the statements discussed during the consensus, which involved all of the most important Italian scientific societies engaged in the multi-disciplinary and multi-professional management of the disease.

BOMB trial: First results of stereotactic radiotherapy to primary breast tumor in metastatic breast cancer patients.

Aim: A prospective dose escalation trial was developed to evaluate the maximum tolerated dose of stereotactic body radiotherapy (SABRT) to primary breast cancer in stage IV disease. The aim of the present report was to describe safety and outcome of the first dose level cohort of patients. Material and methods: Patients with histologically confirmed diagnosis of invasive breast carcinoma (biological immuno-histochemical profile: luminal and/or HER2 positive) and distant metastatic disease not progressing after 6 months of systemic therapy with a tumor CT or 5FDG-PET detectable were deemed eligible. The starting dose was 40 Gy in 5 fractions (level 1) because this dose proved to be safe in previous dose-escalation trial on adjuvant stereotactic body radiotherapy. The maximum dose level was chosen as 45 Gy in 5 fractions. Dose limiting toxicity was any grade 3 or worse toxicity according to CTCAE v.4. Time-to-event Keyboard (TITE-Keyboard) design (Lin and Yuan, Biostatistics 2019) was used to find the maximum tolerated dose (MTD). MTD was the dose of radiotherapy associated with a ≤ 20% rate pre-specified treatment-related dose-limiting toxicity (DLT). Results: To date 10 patients have been treated at the starting dose level. Median age was 80 years (range 50-89). 7 patients had a luminal disease, while 3 patients had an HER2 positive disease. No patient suspended ongoing systemic treatment. No protocol defined DLTs were observed. Grade 2 skin toxicity occurred in 4 patients with diseases located close to or involving the skin. Median follow-up was 13 months and all 10 patients were evaluable for response: 5 achieved a complete response, 3 achieved a partial response and 2 showed a stable disease, all with a clinical benefit (resolution of skin retraction, bleeding and pain). The mean reduction in the sum of the largest diameters of target lesions was of 61.4% (DS=17.0%). Conclusions: SABR to primary breast cancer seems feasible and is associated with symptoms reduction. Continued accrual to this study is needed to confirm the safety and assess the MTD. Clinical trial registration: ClinicalTrials.gov, identifier NCT05229575.