Ultrahypofractionation in postoperative radiotherapy for breast cancer: A single-institution retrospective cohort series.

BACKGROUND: The 'FAST-forward', study published in April 2020, demonstrated the effectiveness of an extremely hypofractionated radiotherapy schedule, delivering the total radiation dose in five sessions over the course of 1 week. We share our department's experience regarding patients treated with this regimen in real-world clinical settings, detailing outcomes related to short-term toxicity and efficacy. METHODS: A descriptive observational study was conducted on 160 patients diagnosed with breast cancer. Between July 2020 and December 2021, patients underwent conservative surgery followed by a regimen of 26 Gy administered in five daily fractions. RESULTS: The median age was 64 years (range: 43-83), with 82 patients (51.3%) treated for left-sided breast cancer, 77 patients (48.1%) for right-sided breast cancer, and 1 instance (0.6%) of bilateral breast cancer. Of these, 66 patients had pT1c (41.3%), 70.6% were infiltrative ductal carcinomas, and 11.3% were ductal carcinoma in situ. Most tumours exhibited intermediate grade (41.9%), were hormone receptor positive (81.3%), had low Ki-67 (Ki-67 < 20%; 51.9%) and were Her 2 negative (85%). The majority of surgical margins were negative (99.4%). Among the patients, 72.5% received hormonotherapy, and 23.8% received chemotherapy. Additionally, 26 patients (16.3%) received an additional tumour boost following whole breast irradiation (WHBI) of 10 Gy administered in five sessions of 2 Gy over a week. The median planning target volume (PTV) was 899 cm3 (range: 110-2509 cm3). Early toxicity was primarily grade I radiodermatitis, affecting 117 patients (73.1%). During a median follow-up of 15 months (range: 3.9-28.77), only one patient experienced a local relapse, which required mastectomy. CONCLUSIONS: The implementation of this highly hypofractionated regimen in early-stage breast cancer appears feasible and demonstrates minimal early toxicity. However, a more extended follow-up duration would be required to evaluate long-term toxicity and efficacy accurately.

Whole-brain radiation therapy plus simultaneous integrated boost for brain metastases from breast cancers.

Background: The effect of whole-brain radiation therapy (WBRT) plus simultaneous integrated boost (SIB) in brain metastasis from breast cancers has not been demonstrated. Method: In this single-center retrospective study, we reviewed consecutive breast cancer patients who developed brain metastasis and were treated with hypofractionated radiation therapy plus WBRT using intensity-modulated radiation therapy (IMRT)-SIB approaches. We analyzed clinical outcomes, prognostic factors and patterns of treatment failure. Result: A total of 27 patients were eligible for analysis. Four (14.8%) patients achieved clinical complete response and 14 (51.9%) had partial response of brain lesions. The other nine patients were not evaluated for brain tumor response. The median brain progression-free survival was 8.60 (95% CI [6.43-13.33]) months and the median overall survival was 16.8 (95% CI [13.3-27.7]) months. Three patients had in-field failure, five had out-field failure and two had in-field and out-field failure. Conclusion: WBRT plus SIB led to improved tumor control and clinical outcome in breast cancer patients with brain metastasis.

Breast cancer in a transgender man and hypofractionated radiotherapy: A case report and review of literature.

A 77-year-old transgender man (assigned female sex at birth, gender identity male, i.e. female-to-male) was referred for a palpable mass of the right chest wall. Biopsies revealed invasive lobular breast carcinoma. After discussion by a multidisciplinary tumour board meeting, the patient was treated with total mastectomy, adjuvant hypofractionated radiation therapy, and hormone therapy. At 1.5-year follow-up, there was no sign of recurrence or long-term radiation side effects. To our knowledge, this is the first reported case of adjuvant hypofractionated radiation therapy in a transgender patient with breast cancer.

Muscle-invasive bladder cancer in elderly and frail people: Is hypofractionated radiotherapy a feasible approach when no other local options are available?

AIM: The study aims to report the feasibility and safety of palliative hypofractionated radiotherapy targeting macroscopic bladder tumors in a monocentric cohort of frail and elderly bladder cancer patients not eligible for curative treatments. METHODS: Patients who underwent hypofractionated radiotherapy to the gross disease or to the tumor bed after transurethral resection of bladder tumor from 2017 to 2021 at the European Institute of Oncology IRCCS, were retrospectively considered. Schedules of treatment were 30 and 25 Gy in 5 fractions (both every other day, and consecutive days). Treatment response was evaluated with radiological investigation and/or cystoscopy. Toxicity assessment was carried out according to RTOG/EORTC v2.0 criteria. RESULTS: A total of 16 patients were included in the study, of these 11 received hypofractionated radiotherapy on the macroscopic target volume and five on the tumor bed after transurethral resection of bladder tumor. No grade (G) >2 acute toxicities were described after treatment for both groups. Only one patient in the group receiving radiotherapy on the macroscopic disease reported G4 GU late toxicity. Ten patients had available follow-up status (median FU time 18 months), of them six had complete response, one had stable disease, and three had progression of disease. The overall response rate and disease control rate were 60% and 70%, respectively. CONCLUSION: Our preliminary data demonstrate that palliative hypofractionated radiotherapy for bladder cancer in a frail and elderly population is technically feasible, with an acceptable toxicity profile. These outcomes emphasize the potential of this approach in a non-radical setting and could help to provide more solid indications in this underrepresented setting of patients.

Personalizing Locoregional Therapy in Patients With Breast Cancer in 2024: Tailoring Axillary Surgery, Escalating Lymphatic Surgery, and Implementing Evidence-Based Hypofractionated Radiotherapy.

The management of axillary lymph nodes in breast cancer is continually evolving. Recent data now support omitting axillary lymph node dissection (ALND) in most patients with metastases in up to two sentinel lymph nodes (SLNs) during upfront surgery and those with residual isolated tumor cells after neoadjuvant chemotherapy (NACT). In the upfront surgery setting, ALND is still indicated, however, in patients with clinically node-positive breast cancer or more than two positive SLNs and, after NACT, in case of residual micrometastases and macrometastases. Omission of the sentinel lymph node biopsy (SLNB) can be considered in many postmenopausal patients with small luminal breast cancer, particularly when axillary ultrasound is negative. Several randomized controlled trials (RCTs) are currently aiming at eliminating the remaining indications for ALND and also establishing omission of SLNB in a broader patient population. The movement to deescalate axillary staging is in part because of the association between ALND and lymphedema, which is swelling of an extremity because of lymphatic damage and obstructed lymphatic drainage. To reduce the risk of developing this condition, patients undergoing ALND can undergo reverse mapping of the axilla and immediate reconstruction or bypass of the lymphatics from the involved extremity. Decongestion and compression are the foundation of conservative treatment for established lymphedema, while lymphovenous bypass and lymph node transfer are surgical procedures to address the physiologic dysfunction. Radiotherapy is an essential component of breast locoregional therapy: more than three decades of radiation research has optimized treatment according to patient's risk of local recurrence while substantially reducing the number of treatment visits. High-quality RCTs have shown the efficacy and safety of hypofractionation-more than 2Gy radiation dose per treatment (fraction)-significantly reducing the burden of radiotherapy treatment for many patients with breast cancer. In 2024, guidelines recommend no more than 15-16 fractions for whole-breast and nodal radiotherapy, with some recommending five fractions for whole-breast radiotherapy. In addition, simultaneous integrated boost (SIB) has been shown to be noninferior to sequential boost with regards to ipsilateral breast tumor recurrence with similar or reduced long-term side effects, also reducing overall treatment length. Further RCTs are underway investigating other indications for five fractions, including SIB and regional node irradiation, such that, in future, it may be possible for the majority of breast radiotherapy patients to be treated with a 1-week course. This manuscript serves to outline the latest updates on axillary surgical staging, lymphatic surgery, and evidence-based radiotherapy in the treatment of breast cancer.

Long-Term Analysis of NRG Oncology RTOG 0415: A Randomized Phase III Noninferiority Study Comparing Two Fractionation Schedules in Patients With Low-Risk Prostate Cancer.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.NRG Oncology RTOG 0415 is a randomized phase III noninferiority (NI) clinical trial comparing conventional fractionation (73.8 Gy in 41 fractions) radiotherapy (C-RT) with hypofractionation (H-RT; 70 Gy in 28) in patients with low-risk prostate cancer. The study included 1,092 protocol-eligible patients initially reported in 2016 with a median follow-up of 5.8 years. Updated results with median follow-up of 12.8 years are now presented. The estimated 12-year disease-free survival (DFS) is 56.1% (95% CI, 51.5 to 60.5) for C-RT and 61.8% (95% CI, 57.2 to 66.0) for H-RT. The DFS hazard ratio (H-RT/C-RT) is 0.85 (95% CI, 0.71 to 1.03), confirming NI (P < .001). Twelve-year cumulative incidence of biochemical failure (BF) was 17.0% (95% CI, 13.8 to 20.5) for C-RT and 9.9% (95% CI, 7.5 to 12.6) for H-RT. The HR (H-RT/C-RT) comparing biochemical recurrence between the two arms was 0.55 (95% CI, 0.39 to 0.78). Late grade ≥3 GI adverse event (AE) incidence is 3.2% (C-RT) versus 4.4% (H-RT), with relative risk (RR) for H-RT versus C-RT 1.39 (95% CI, 0.75 to 2.55). Late grade ≥3 genitourinary (GU) AE incidence is 3.4% (C-RT) versus 4.2% (H-RT), RR 1.26 (95% CI, 0.69 to 2.30). Long-term DFS is noninferior with H-RT compared with C-RT. BF is less with H-RT. No significant differences in late grade ≥3 GI/GU AEs were observed between assignments (ClinicalTrials.gov identifier: NCT00331773).

Prospective phase II trial of preoperative hypofractionated proton therapy for extremity and truncal soft tissue sarcoma: the PRONTO study rationale and design.

BACKGROUND: Oncologic surgical resection is the standard of care for extremity and truncal soft tissue sarcoma (STS), often accompanied by the addition of pre- or postoperative radiation therapy (RT). Preoperative RT may decrease the risk of joint stiffness and fibrosis at the cost of higher rates of wound complications. Hypofractionated, preoperative RT has been shown to provide acceptable outcomes in prospective trials. Proton beam therapy (PBT) provides the means to decrease dose to surrounding organs at risk, such as the skin, bone, soft tissues, and adjacent joint(s), and has not yet been studied in patients with extremity and truncal sarcoma. METHODS: Our study titled "PROspective phase II trial of preoperative hypofractionated protoN therapy for extremity and Truncal soft tissue sarcOma (PRONTO)" is a non-randomized, prospective phase II trial evaluating the safety and efficacy of preoperative, hypofractionated PBT for patients with STS of the extremity and trunk planned for surgical resection. Adult patients with Eastern Cooperative Group Performance Status ≤ 2 with resectable extremity and truncal STS will be included, with the aim to accrue 40 patients. Treatment will consist of 30 Gy radiobiological equivalent of PBT in 5 fractions delivered every other day, followed by surgical resection 2-12 weeks later. The primary outcome is rate of major wound complications as defined according to the National Cancer Institute of Canada Sarcoma2 (NCIC-SR2) Multicenter Trial. Secondary objectives include rate of late grade ≥ 2 toxicity, local recurrence-free survival and distant metastasis-free survival at 1- and 2-years, functional outcomes, quality of life, and pathologic response. DISCUSSION: PRONTO represents the first trial evaluating the use of hypofractionated PBT for STS. We aim to prove the safety and efficacy of this approach and to compare our results to historical outcomes established by previous trials. Given the low number of proton centers and limited availability, the short course of PBT may provide the opportunity to treat patients who would otherwise be limited when treating with daily RT over several weeks. We hope that this trial will lead to increased referral patterns, offer benefits towards patient convenience and clinic workflow efficiency, and provide evidence supporting the use of PBT in this setting. TRIAL REGISTRATION: NCT05917301 (registered 23/6/2023).

Online Adaptive MR-Guided Ultrahypofractionated Radiotherapy of Prostate Cancer on a 1.5 T MR-Linac: Clinical Experience and Prospective Evaluation.

The use of hypofractionated radiotherapy in prostate cancer has been increasingly evaluated, whereas accumulated evidence demonstrates comparable oncologic outcomes and toxicity rates compared to normofractionated radiotherapy. In this prospective study, we evaluate all patients with intermediate-risk prostate cancer treated with ultrahypofractionated (UHF) MRI-guided radiotherapy on a 1.5 T MR-Linac within our department and report on workflow and feasibility, as well as physician-recorded and patient-reported longitudinal toxicity. A total of 23 patients with intermediate-risk prostate cancer treated on the 1.5 T MR-Linac with a dose of 42.7 Gy in seven fractions (seven MV step-and-shoot IMRT) were evaluated within the MRL-01 study (NCT04172753). The duration of each treatment step, choice of workflow (adapt to shape-ATS or adapt to position-ATP) and technical and/or patient-sided treatment failure were recorded for each fraction and patient. Acute and late toxicity were scored according to RTOG and CTC V4.0, as well as the use of patient-reported questionnaires. The median follow-up was 12.4 months. All patients completed the planned treatment. The mean duration of a treatment session was 38.2 min. In total, 165 radiotherapy fractions were delivered. ATS was performed in 150 fractions, 5 fractions were delivered using ATP, and 10 fractions were delivered using both ATS and ATP workflows. Severe acute bother (G3+) regarding IPS-score was reported in five patients (23%) at the end of radiotherapy. However, this tended to normalize and no G3+ IPS-score was observed later at any point during follow-up. Furthermore, no other severe genitourinary (GU) or gastrointestinal (GI) acute or late toxicity was observed. One-year biochemical-free recurrence survival was 100%. We report the excellent feasibility of UHF MR-guided radiotherapy for intermediate-risk prostate cancer patients and acceptable toxicity rates in our preliminary study. Randomized controlled studies with long-term follow-up are warranted to detect possible advantages over current state-of-the-art RT techniques.

Moderately hypofractionated proton beam therapy for localized prostate cancer: 5-year outcomes of a phase II trial.

The usefulness of moderately hypofractionated radiotherapy for localized prostate cancer has been extensively reported, but there are limited studies on proton beam therapy (PBT) using similar hypofractionation schedules. The aim of this prospective phase II study is to confirm the safety of a shortened PBT course using 70 Gy relative biological effectiveness (RBE) in 28 fractions. From May 2013 to June 2015, 102 men with localized prostate cancer were enrolled. Androgen deprivation therapy was administered according to risk classification. Toxicity was assessed using Common Terminology Criteria for Adverse Events version 4.0. Of the 100 patients ultimately evaluated, 15 were classified as low risk, 43 as intermediate risk, and 42 as high risk. The median follow-up time of the surviving patients was 96 months (range: 60-119 months). The 5-year cumulative incidences of grade 2 gastrointestinal/genitourinary adverse events were 1% (95% CI: 0.1-6.9) and 4% (95% CI: 1.5-10.3), respectively; no grade ≥ 3 gastrointestinal/genitourinary adverse events were observed. The current study revealed a low incidence of late adverse events in prostate cancer patients treated with moderately hypofractionated PBT of 70 Gy (RBE) in 28 fractions, indicating the safety of this schedule.

Hypofractionated radiotherapy with simultaneous tumor bed boost (Hi-RISE) in breast cancer patients receiving upfront breast-conserving surgery: study protocol for a phase III randomized controlled trial.

BACKGROUND: The effectiveness and safety of moderately hypofractionated radiotherapy (HFRT) in patients undergoing breast-conserving surgery (BCS) has been demonstrated in several pivotal randomized trials. However, the feasibility of applying simultaneous integrated boost (SIB) to the tumor bed and regional node irradiation (RNI) using modern radiotherapy techniques with HFRT needs further evaluation. METHODS: This prospective, multi-center, randomized controlled, non-inferiority phase III trial aims to determine the non-inferiority of HFRT combined with SIB (HFRTsib) compared with conventional fractionated radiotherapy with sequential boost (CFRTseq) in terms of five-year locoregional control rate in breast cancer patients undergoing upfront BCS. A total of 2904 participants will be recruited and randomized in a 1:1 ratio into the HFRTsib and CFRTseq groups. All patients will receive whole breast irradiation, and those with positive axillary nodes will receive additional RNI, including internal mammary irradiation. The prescribed dose for the HFRTsib group will be 40 Gy in 15 fractions, combined with a SIB of 48 Gy in 15 fractions to the tumor bed. The CFRTseq group will receive 50 Gy in 25 fractions, with a sequential boost of 10 Gy in 5 fractions to the tumor bed. DISCUSSION: This trial intends to assess the effectiveness and safety of SIB combined with HFRT in early breast cancer patients following BCS. The primary endpoint is locoregional control, and the results of this trial are expected to offer crucial evidence for utilizing HFRT in breast cancer patients after BCS. TRIAL REGISTRATION: This trial was registered at ClincalTrials.gov (NCT04025164) on July 18, 2019.

10-yr Results of Moderately Hypofractionated Postoperative Radiotherapy for Prostate Cancer Focused on Treatment Related Toxicity.

INTRODUCTION: To retrospectively report long term outcomes following postoperative hypofractionated radiotherapy (RT) for prostate cancer, emphasizing treatment related toxicity. MATERIAL AND METHODS: Patients for whom adjuvant or salvage RT was indicated after prostatectomy were treated with a course of moderate hypofractionation consisting in the delivery of 62.5 Gy in 25 fractions (2.5 Gy per fraction) on the prostate bed in 5 consecutive weeks (EQD21.5 = 70 Gy) by means of 3D-CRT in most of them. Androgen deprivation therapy (ADT) was allowed at physician's discretion. Patients were evaluated for urinary and rectal complications according to the Common Terminology Criteria for Adverse Events v4 (CTCAE v.4). Overall survival (OS), biochemical recurrence free survival (bRFS), and metastasis-free survival (MFS) were estimated using the Kaplan-Meier method. RESULTS: One hundred and ten patients with a median age of 67 years (range 51-78) were enrolled. The majority of them (82%) had adverse pathologic features only, while 31 (28%) had early biochemical relapse. Median PSA level before RT was 0.12 ng/mL (range 0-9 ng/mL). Median time from surgery was 4 months (range 1-136 months). Twenty-eight patients (25.4%) also received ADT. At a median follow up of 103 months (range 19-138 months), late Grade 3 and Grade 4 rectal toxicity were 0.9% (1 case of hematochezia) and 0.9% (1 case of fistula), respectively, while late Grade 3 GU side effects (urethral stenosis) occurred in 9 cases (8%). No late Grade 4 events were observed, respectively. Ten-year OS, b-RFS and MFS were 77.3% (95%CI: 82.1%-72.5%), 53.3% (95%CI: 59.9%-47.6%), and 76.7% (95%CI: 81.2%-72.2%), respectively. CONCLUSION: Our study provides long term data that a shortened course of postoperative RT is as safe and effective as a long course of conventionally fractionated RT and would improve patients' convenience and significantly reduce RT department workloads.

Assessment of Radiation Induced Pneumonitis and Pericarditis in Patients Undergoing Breast Conservative Treatment Using Hypofractionated Simultaneous Integrated Boost Technique.

INTRODUCTION: To determine the proportion of radiationinduced pneumonitis and pericarditis in patients who have received Hypo-fractionated Radiation along with simultaneous integrated boost technique after breast conservative surgery using a prospective observational study from a tertiary hospital. MATERIALS & METHODS: The incidence of radiationinduced pneumonitis and pericarditis was evaluated in all adult patients with biopsy-proven early-stage unilateral breast cancer who underwent breast-conserving surgery followed by hypo-fractionated radiation with a simultaneous integrated boost technique. Baseline assessments including a six-minute walk test, highresolution computed tomography (HRCT), pulmonary function tests (PFTs), electrocardiography (ECG) and echocardiography (ECHO) were performed. At three months post-radiation treatment, patients underwent follow-up assessments with a six-minute walk test, ECG and ECHO. At six months post-radiation treatment, patients underwent further assessments with a six-minute walk test, ECG, ECHO, PFTs, and HRCT of the thorax. Data analysis was performed using SPSS version 19. RESULTS: Our study investigated the incidence of acute radiation-induced pneumonitis and pericarditis in patients treated with hypofractionated VMAT-SIB technique in 20 eligible early breast cancer patients. The study found that the technique is feasible and achieves encouraging dosimetric parameters, including well achieved ipsilateral lung and heart doses. The reduced treatment time of 3-4 weeks compared to the previous 6-7 weeks with sequential boost was also found to be desirable in resource-constrained settings. The incidence of acute radiation pneumonitis and pericarditis was acceptable and comparable to existing data, with 90% of patients experiencing grade 1 radiation pneumonitis according to CTCAE v5.0. Post-treatment pulmonary function tests showed significant changes, particularly in patients who had received neoadjuvant chemotherapy and nodal irradiation. The six-minute walk test and Borg scale also showed a significant positive correlation with pulmonary function tests. There was no significant pericarditis during the follow-up. The study proposes that the hypofractionated radiotherapy using VMAT-SIB is a suitable alternative to conventional fractionation, with acceptable acute toxicities, but longer follow-up is required to assess the impact on late toxicities. CONCLUSION: Our research has shown that hypofractionated adjuvant radiotherapy with SIB is a safe and feasible treatment for patients with early breast cancer. This treatment method doesn't pose any significant short-term risks to the lungs or heart, and the SIB technique provides better coverage, conformity and sparing of organs at risk. Additionally, patients have reported positive cosmetic outcomes with this treatment. However, to make more accurate conclusions, we need to conduct further studies with larger sample sizes and longer follow-up periods to evaluate the potential longterm side effects of this treatment using VMAT in whole breast radiation.

In Response to "Acute Oral Mucositis During Hypo-Fractionated Radiation in Squamous Cell Carcinoma of Oral Cavity".

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Systematic Review of Hypofractionated Radiation Therapy for the Treatment of Oesophageal Squamous Cell Carcinoma and Oesophageal Adenocarcinoma.

BACKGROUND AND AIM: There has been limited progress made in improving the suboptimal outcomes delivered by conventionally fractionated radiotherapy (RT) for oesophageal adenocarcinoma (OAC) and squamous cell carcinoma (OSCC). A greater biological effect may be achieved using hypofractionated RT (HFRT), though the toxicity, tolerability and efficacy of this approach in OAC and OSCC is uncertain. METHODS: A systematic literature review was carried out in accordance with Preferred Reporting Items for Systematic Reviews guidance. Medline, EMBASE, PubMed, Cochrane, CINAHL, Scopus and Web of Science databases were searched for terms relating to HFRT (>2.4Gy per fraction) for OAC or OSCC. All relevant clinical studies published between January 2000 and April 2023 were included. Study quality was assessed using predefined criteria. RESULTS: Ninety-six studies were screened and 20 subsequently included, together incorporating 1208 patients. Fourteen studies focussed on neoadjuvant or definitive treatment. These were predominantly retrospective (n = 10, 71%) though two (n = 2, 14%) early phase trials were identified. Most focussed on OSCC (n = 7, 47%) or mixed OSCC/OAC (n = 6, 43%) populations. Four (28.6%) included a conventionally fractionated chemoradiotherapy (CRT) comparator, against which median overall (mOS) and progression free survival outcomes from HFRT did not differ. Reported mOS for HFRT ranged between 29-36 months at 2.5-3.125Gy per fraction (total dose 50-60Gy) for OAC and OSCC combined. Toxicity and tolerability with HFRT was comparable with conventionally fractionated CRT up to, but not exceeding, 5Gy. Three (50%) of the six palliative-intent studies were early phase trials and most (n = 4, 67%) focussed on OAC and OSCC. Response rates with HFRT in the palliative setting were 63.6-88.0%. CONCLUSION: These data provide evidence in OAC/OSCC for promising efficacy and an acceptable toxicity profile for moderately HFRT, alone or with concurrent chemotherapy. These data should prompt prospective, randomised comparisons of HFRT and conventionally fractionated CRT and single-modality RT schedules. REGISTRATION DETAILS: PROSPERO; CRD42023457791.

Fraction Dose Escalation of Hypofractionated Radiotherapy with Concurrent Chemotherapy and Subsequent Consolidation Immunotherapy in Locally Advanced Non-Small Cell Lung Cancer: A Phase I Study.

PURPOSE: This phase I trial aimed to determine the maximum tolerated fraction dose (MTFD) of hypofractionated radiotherapy (hypo-RT) combined with concurrent chemotherapy and subsequent consolidation immune checkpoint inhibitors (cICI) for patients with locally advanced non-small cell lung cancer. PATIENTS AND METHODS: Split-course hypo-RT and hypoboost combined with concurrent chemotherapy was administered at three dose levels (DL), using a stepwise dose-escalation protocol. The sophisticated esophagus-sparing technique was implemented to restrict the dose to the esophagus. Patients who did not experience disease progression or unresolved ≥grade 2 (G2+) toxicities after RT received cICI. Each DL aimed to treat six patients. The MTFD was defined as the highest DL at which ≤2 patients of the six who were treated experienced treatment-related G3+ toxicity and ≤1 patient experienced G4+ toxicity within 12 months post-RT. RESULTS: Eighteen patients were enrolled, with six patients in each DL. All patients completed hypo-RT and concurrent chemotherapy, and 16 (88.9%) received at least one infusion of cICI, with a median of 10 infusions. Within the 12-month assessment period, one patient in DL1 experienced G3 pneumonitis, and one patient in DL3 developed G3 tracheobronchitis. The MTFD was not reached. The objective response rate was 100%. With a median follow-up of 20.9 months, the 1-year overall survival and progression-free survival rates were 94.4% and 83.3%, respectively. CONCLUSIONS: Utilizing the split-course hypo-RT and hypoboost approach, a fraction dose of 5 Gy to a total dose of 60 Gy, combined with concurrent chemotherapy and subsequent cICI, was well tolerated and yielded a promising objective response rate and survival outcomes.