RT Dose Research Articles

Identification of a Suitable Subgroup for Radiation Dose Escalation in Definitive Concurrent Chemoradiation Therapy for Nonmetastatic Esophageal Squamous Cell Carcinoma.

Dose escalation may only be suitable for some patients with esophageal cancer (EC) undergoing concurrent chemoradiotherapy (CCRT). This study aimed to identify specific subgroups of patients for whom dose escalation was most beneficial. Between January 2008 and December 2022, 187 patients with EC underwent CCRT; 94 patients received high-dose (HD) radiotherapy (RT; >64.8 Gy), and 93 patients received low-dose (LD) RT. We developed a model on the basis of clinical and radiomic features to compare the predicted survival probabilities of patients with EC receiving HD- and LD-RT. Patients suitable for HD-RT could be identified. We validated our findings of a suitable HD subgroup by evaluating the actual overall survival (OS) across different subgroups in the testing set. Our model comprised HD and LD submodels, each predicting patient survival under their respective RT doses. The HD and LD submodels achieved concordance indexes of 0.78 and 0.75 in their respective testing sets. The average areas under the receiver operating characteristic curve over years 1-3 were 0.890 and 0.807 in the HD and LD testing sets, respectively. By comparing patients' predicted survival under HD- and LD-RT in the model, we classified the patients in the testing set into the HD-suitable (HDS) subgroup and the HD-unsuitable subgroup. In the subgroup analysis, HD-RT led to a better OS benefit for the identified HDS subgroup compared with LD-RT (P = .014). Among the HD-treated patients, the HDS subgroup showed better OS than did patients identified as unsuitable (P < .001). We identified a suitable subgroup of patients with EC who might benefit from HD-RT. This model could aid clinicians in prescribing RT doses.

Pneumonitis after normofractionated radioimmunotherapy: a method for dosimetric evaluation

BackgroundPost-Therapy-Pneumonitis (PTP) is a critical side effect of both, thoracic radio(chemo)therapy (R(C)T) and immune checkpoint inhibition (ICI). However, disease characteristics and patient-specific risk factors of PTP after combined R(C)T + ICI are less understood. Given that RT-triggered PTP is strongly dependent on the volume and dose of RT [1], driven by inflammatory mechanisms, we hypothesize that combination therapy of R(C)T with ICI influences the dose-volume-effect correlation for PTP. This study focuses on the development of a method for evaluation of alterations of dosimetric parameters for PTP after R(C)T with and without ICI.Methods and materialsPTP volumes were delineated on the follow-up diagnostic Computed Tomography (CT) and deformably matched to the planning CT for patients with PTP after thoracic R(C)T + ICI or R(C)T. Dose data was converted to 2-Gy equivalent doses (EQD2) and dosimetrically analyzed. Dosimetric and volumetric parameters of the segmented PTP volumes were analyzed. The method was exemplarily tested on an internal patient cohort including 90 patients having received thoracic R(C)T + ICI (39) and R(C)T (51). Thirtytwo patients with PTP were identified for further analysis. Additional data on previous chemotherapy, RT, smoking status and pulmonary co-morbidity were conducted. A matched pair analysis with regard to planning target volumes (PTV) was conducted for curative intended (definitive) and palliative patient cohorts individually.ResultsThe presented method was able to quantify and compare the dosimetric parameters of PTP for the different therapies. For our study group, no significant differences between R(C)T + ICI and R(C)T only was observed. However, the dosimetric analysis revealed large volumetric fractions (55%) of the PTP volumes to be located outside of high dose (EQD2 < 40 Gy) regions for R(C)T + ICI. There was a non-significant trend towards increased area under the curve of the dose volume histogram (AUC) values for R(C)T + ICI compared to R(C)T only (3743.6 Gy∙% vs. 2848.8 Gy∙%; p-value = 0.171). In contrast to the data for the palliative intended treatment group, for definitive R(C)T + ICI, data tended towards increased volumes with higher doses.ConclusionsThe proposed method was capable to quantify dosimetric differences in the dose-volume-effect relationship of PTP for patients with R(C)T + ICI and patients with R(C)T only. In this exploratory analysis, no significant dosimetric differences within PTP volumes for the different groups could be observed. However, our observations suggest, that for safe application of thoracic R(C)T + ICI, further careful investigation of dosimetric prescription and analysis concepts with larger and conformer study groups is recommendable.

Abstract 4137636: Cardiac radiation dose and changes in physical activity and quality of life in patients with locally advanced lung cancer

Background: Physical activity is associated with prognosis in cancer. However, in non-small cell lung cancer (NSCLC), a high cardiovascular (CV) population, the relationships between RT dose, physical activity, and CV patient-reported outcomes remain unclear. We determined the associations between cardiac radiation dose-volume metrics and changes in physical activity and quality-of-life (QoL) in patients treated with definitive chemoradiation. Methods: NSCLC participants treated with chemoradiation were enrolled in a multi-center longitudinal cohort study. Self-reported physical activity via Godin–Shephard Leisure-Time Physical Activity Questionnaire (Godin) and QoL via Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue and Dyspnea Scales were collected at baseline, end of RT, 6, and 12 months post-RT. Changes in Godin and FACIT scores over time were examined using linear mixed-effects models. Multivariable linear regression via generalized estimating equations assessed the associations between: 1) mean heart dose (MHD) and longitudinal changes in physical activity and QoL, and 2) concurrent changes in physical activity and FACIT scores. Results: Across 101 participants, the mean age was 66 years, with 57% male, 66% White, and 25% Black. The median (Q1, Q3) MHD was 10.8 Gy (6.1,16.3). Very low physical activity [9 (0, 25)], high dyspnea [4 (1, 9)], and low fatigue [39 (31,46)] were reported at baseline. With chemoRT, there was a significant worsening of physical activity ( P = 0.03), fatigue ( P &lt; 0.001), and dyspnea ( P &lt; 0.001). Each 1-Gy increase in MHD was associated with a modest decline in physical activity (-0.28; 95% CI -0.53, -0.02, P = 0.03), and higher physical activity was associated with a concurrent decrease in fatigue ( P &lt; 0.001) and dyspnea ( P = 0.007) (Table). Conclusions: In locally advanced NSCLC, physical activity levels prior to RT were very low, and higher cardiac radiation dose was associated with a further decline in physical activity. Increased physical activity was associated with concurrent decreases in fatigue and dyspnea. Strategies to promote physical activity may result in improved QoL in this high CV group.

Low‒Dose Cyclophosphamide Enhances the Tumoricidal Effects of 5-Day Spacing Stereotactic Ablative Radiotherapy by Boosting Antitumor Immunity.

To investigate the potential role of low‒dose cyclophosphamide (Cy) as a radiosensitizer by evaluating its impact on the immune response and the abscopal effect of stereotactic ablative radiotherapy (SABR) through preclinical models. CT26 tumors (immunologically hot) and 4T1 tumors (immunologically cold), grown in immunocompetent BALB/c and immunodeficient BALB/c‒nude mice, were irradiated with 20 Gy in two fractions with 5‒day spacing followed by intraperitoneal injections of 9 mg/kg Cy every 3 days. Immunological changes in CT26 tumors caused by the treatments were assessed using flow cytometry. Changes in the expression of HIF‒1α in tumors were also assessed. Splenocytes and bone marrow‒derived dendritic cells (DCs) were exposed to various concentrations of Cy to assess T cell proliferation and DC differentiation. The combination of Cy with RT (RT+Cy) significantly suppressed tumor growth compared to RT alone in immunocompetent mice, while that effect was not observed in immunodeficient mice. Additionally, RT+Cy effectively induced abscopal effects in hot and cold tumors, with increased CD8+ T cells in blood and tumors. Significantly higher expression levels of Granzyme B, IFN‒γ, and TNF‒α were observed in RT+Cy group compared to the RT alone group. In vitro data indicated that low‒dose Cy promotes DC differentiation. Low‒dose Cy suppressed the radiation‒induced upregulation of HIF‒1α in the tumors. Low‒dose Cy enhances tumoricidal effects of 5‒day spacing high‒dose RT by increasing anti-tumor immune responses.

Radiation Dose Be Personalized in Patients With Localized NSCLC and Actionable Genetic Alterations? Insight From a Multicenter Real-World Study

ObjectivesRadiation therapy (RT) is central to the management of unresectable stage I to III NSCLC. Nevertheless, the impact of actionable genetic driver alterations (AGAs) on locoregional control (LRC) from RT remains uncertain. A retrospective, multicenter real-world study was undertaken to determine if common AGAs impact LRC after RT. MethodsPatients who received curative-intent RT for NSCLC between 2018 and 2020 at four centers in the United Kingdom and had available molecular testing were included. Locoregional control was compared in a 1:2 ratio between a group of patients with an AGA and a control group without AGA. Locoregional control was assessed with competing risks analysis and overall survival was analyzed by Cox regression, adjusting for established prognostic clinical factors. ResultsData was collected for 185 eligible patients: 50 with an AGA and 135 without. Baseline characteristics, including patient demographics, tumor features, and treatment details were evenly distributed between the two groups. LRC was similar in the AGA and non-AGA groups (39% versus 34%, hazard ratio = 1.13, 95% confidence interval: 0.61–1.984, p = 0.84). Actionable genetic driver alterations were not associated with LRC according to multivariable regression analysis. Median overall survival was significantly higher in the AGA group (45 mo versus 26 mo, hazard ratio = 0.64, 95% confidence interval: 0.43–0.96, p = 0.044), and all these patients received targeted therapies on relapse. ConclusionLRC was comparable in the AGA and non-AGA groups suggesting that there is no role for personalization of RT dose in patients with AGA. Nevertheless, survival rates were notably higher among patients with AGA, likely owing to the availability of efficacious targeted therapies on relapse.

Salvage Reirradiation with Proton Beam Therapy for Locoregionally Recurrent Non-Small Cell Lung Cancer.

This retrospective study evaluates outcomes of 66 patients who underwent reirradiation (re-RT) with proton beam therapy (PBT) for recurrent non-small cell lung cancer. Toxicity was scored via the CTCAE v5.0, and outcomes estimated using the Kaplan-Meier method, with associations evaluated via Cox proportional hazards and logistic regression analyses. Patients were treated to a median re-RT prescription of 66 Gy/33 fxs (BED10 = 79 Gy; IQR: 71-84 Gy) at an interval of 1.4 years from prior RT. Half (50%) received concurrent chemotherapy. At 14 months follow-up, the median OS and PFS were 5 months (95%CI: 13-17) and 12.5 months (95%CI: 10-15), respectively. On multivariable analysis, a higher RT dose (BED10 > 70 Gy) [HR0.37; 95%CI: 0.20-0.68, p = 0.001] and concurrent chemotherapy (HR0.48; 95%CI: 0.28-0.81, p = 0.007) were associated with improved PFS, while treatment site overlap was adversely associated (HR1.78; 95%CI: 1.05-3.02, p = 0.031). The median PFS for definitive RT with concurrent chemotherapy (n = 28), definitive RT alone (BED10 > 70 Gy) [n = 22], and lower prescription RT (BED10 < 70 Gy) [n = 16] was 15.5 months (95%CI: 7.3-23.7), 14.1 months (95%CI: 10.9-17.3), and 3.3 months (95%CI: 0-12.3), respectively (log-rank, p = 0.006), with corresponding 2-year estimates of 37% (±9), 18% (±8), and 12.5% (±8), respectively. The incidence of Grade 3+ toxicity was 10.5% (6% pulmonary; 3% esophageal; and 1.5% skin), including one Grade 4 bronchopulmonary hemorrhage but no Grade 5 events. Cases with central site overlap had higher composite Dmax to the esophagus (median 87 Gy [IQR:77-90]), great vessels (median 120 Gy [IQR:110-138]), and proximal bronchial tree (median 120 Gy [IQR:110-138]) as compared to other cases (p ≤ 0.001 for all). However, no significant associations were identified with Grade 3+ events. Thoracic re-RT with PBT is an option for recurrent NSCLC with acceptable outcomes and toxicity for select patients. When feasible, higher prescription doses (BED10 > 70 Gy) should be delivered for definitive intent, and concurrent chemotherapy may benefit individual cases.

Outcome of radiotherapy for metastatic neuroblastoma

Background. Neuroblastoma (NB) is a prevalent solid extracranial tumor that primarily affects children. It is the third most common type of cancer in children, following leukemia and brain tumors. Aim. The study aimed to discuss the clinical outcomes after adjuvant radiotherapy to the primary site in case of metastatic NB after good response to chemotherapy. Methods. A retrospective clinical-dosimetric study of 25 patients metastatic NB treated with radiotherapy at Baghdad Radiotherapy and Nuclear Medicine Center, at Baghdad Medical City Complex, Baghdad, Iraq. Data collection begin from December 2023 and March 2024. Data were collected retrospectively with review of records. The following variables were studied: sex, age, date of diagnosis, site of primary tumor, site of metastasis, chemotherapy, surgery, RT, RT sites, doses of RT, fractions of RT, recurrence sites, date of relapse and survival outcome for each patient. Follow-up period include look up to metastasis, site of metastasis, recurrence, site of recurrence and survival rates. Results. In relation to sex, males (14, 56%) were more than females (11, 44%). The mean age of NB cases was 45.64±17.6 months. In NB, suprarenal masses were the most common site of primary in 21 (84%) of patients. The most common site of metastasis of NB was bone marrow in 12 (48). The multi sites of recurrence was the commonest presentation in 48%. The relapse-free survival (RFS) was 22.38 months. 5 out of 25 patients were alive whereas 20 (80%) of cases were dead. The median follow-up time was 6 years, and the OS of NB in this study after optimal treatment was 2.46 years (95%CI= 1.705-3.21) for survivors. The MS was 4.84 years. The OS was 6 yrs for those diagnosed at 2017, 2 yrs for those diagnosed at 2018, 1.5 yrs for those diagnosed at 2019, 1.75 yrs for those diagnosed at 2020, 3 yrs for those diagnosed at 2021 and 1.5 yrs for those diagnosed at 2022. There was a significant difference among doses (Log Rank (Mantel-Cox)= 11.425, p=0.044). Conclusions. This study is the first study in Iraq that examines the clinical results of radiotherapy on the primary site in cases of metastatic neuroblastoma following induction chemotherapy. The suprarenal masses of neuroblastoma are the most often occurring main site. The primary sites of metastases for neuroblastoma (NB) are the bone marrow and bones. Timely detection and proactive treatment of NB can improve overall results. Reoccurrence of skeletal issues and the infiltration of bone marrow are frequently observed. There were no significant differences observed in terms of relapse-free survival and overall survival based on factors such as sex, age, location of the main tumor, chemotherapy, radiation treatment, surgery, and radiation therapy dosages.

Effect of dose to parotid ducts on Sticky Saliva and Xerostomia in radiotherapy of head and neck squamous cell carcinoma

BackgroundRadiotherapy (RT) in head and neck squamous cell cancer (HNSCC) often leads to sticky saliva and xerostomia (SSX). Dose sparing of salivary glands (SG) reduces occurrence of SSX but few studies investigated the relationship between RT dose to SG substructures and SSX. We therefore investigated this hypothesis, focusing on the parotid duct (PD).MethodsRetrospective data was collected from 99 HNSCC patients treated at our center with (chemo-)radiotherapy (CRT). PD and other organs-at-risk (OAR) were (re-)contoured and DVHs were generated without re-planning. SSX was graded according to CTCAE v.4.03 and evaluated at acute, subacute, and two late timepoints.ResultsMost patients presented with loco-regionally advanced disease. In 47% of patients, up-front neck dissection preceded CRT. Weighted mean dose was 28.6 Gy for bilateral parotid glands (PG), and 32.0 Gy for PD. Acute SSX presented as grades 0 (35.3%), I (41.4%), II (21.2%) and III (2.0%). There was no association of OARs and SSX ≥ grade 2 in univariable logistic regression (LR). Multivariable LR showed statistically significant relationship of acute SSX with: PG weighted mean dose (OR 0.84, p = 0.004), contralateral PG mean dose (OR 1.14, p = 0.02) and contralateral PD planning OAR (PD PRV) mean dose (OR 1.84, p = 0.03).ConclusionsThere was an association of acute SSX with dose exposure of PD PRV in multivariable regression, only. Due to statistical uncertainties and the retrospective nature of this analysis, further studies are required to confirm or reject the hypothesis.

Whole pelvis vs. hemi pelvis elective nodal radiotherapy in patients with PSMA-positive nodal recurrence after radical prostatectomy - a retrospective multi-institutional propensity score analysis

PurposeDespite growing evidence for bilateral pelvic radiotherapy (whole pelvis RT, WPRT) there is almost no data on unilateral RT (hemi pelvis RT, HPRT) in patients with nodal recurrent prostate cancer after prostatectomy. Nevertheless, in clinical practice HPRT is sometimes used with the intention to reduce side effects compared to WPRT. Prostate-specific membrane antigen positron emission tomography / computed tomography (PSMA-PET/CT) is currently the best imaging modality in this clinical situation. This analysis compares PSMA-PET/CT based WPRT and HPRT.MethodsA propensity score matching was performed in a multi-institutional retrospective dataset of 273 patients treated with pelvic RT due to nodal recurrence (214 WPRT, 59 HPRT). In total, 102 patients (51 in each group) were included in the final analysis. Biochemical recurrence-free survival (BRFS) defined as prostate specific antigen (PSA) < post-RT nadir + 0.2ng/ml, metastasis-free survival (MFS) and nodal recurrence-free survival (NRFS) were calculated using the Kaplan-Meier method and compared using the log rank test.ResultsMedian follow-up was 29 months. After propensity matching, both groups were mostly well balanced. However, in the WPRT group there were still significantly more patients with additional local recurrences and biochemical persistence after prostatectomy. There were no significant differences between both groups in BRFS (p = .97), MFS (p = .43) and NRFS (p = .43). After two years, BRFS, MFS and NRFS were 61%, 86% and 88% in the WPRT group and 57%, 90% and 82% in the HPRT group, respectively. Application of a boost to lymph node metastases, a higher RT dose to the lymphatic pathways (> 50 Gy EQD2α/β=1.5 Gy) and concomitant androgen deprivation therapy (ADT) were significantly associated with longer BRFS in uni- and multivariate analysis.ConclusionsOverall, this analysis presents the outcome of HPRT in nodal recurrent prostate cancer patients and shows that it can result in a similar oncologic outcome compared to WPRT. Nevertheless, patients in the WPRT may have been at a higher risk for progression due to some persistent imbalances between the groups. Therefore, further research should prospectively evaluate which subgroups of patients are suitable for HPRT and if HPRT leads to a clinically significant reduction in toxicity.

The Current Position of Postoperative Radiotherapy for Salivary Gland Cancer: A Systematic Review and Meta-Analysis.

Because of the rarity, heterogeneous histology, and diverse anatomical sites of salivary gland cancer (SGC), there are a limited number of clinical studies on its management. This study reports the cumulative evidence of postoperative radiotherapy (PORT) for SGC of the head and neck. A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases between 7th and 10th November 2023. A total of 2962 patients from 26 studies between 2007 and 2023 were included in this meta-analysis. The median RT dose was 64 Gy (range: 56-66 Gy). The median proportions of high-grade, pathological tumor stage 3 or 4 and pathological lymph node involvement were 42% (0-100%), 40% (0-77%), and 31% (0-75%). The pooled locoregional control rates at 3, 5, and 10 years were 92% (95% confidence interval [CI], 89-94%), 89% (95% CI, 86-93%), and 84% (95% CI, 73-92%), respectively. The pooled disease-free survival (DFS) rates at 3, 5, and 10 years were 77% (95% CI, 70-83%), 67% (95% CI, 60-74%), and 61% (95% CI, 55-67%), respectively. The pooled overall survival rates at 3, 5, and 10 years were 84% (95% CI, 79-88%), 75% (95% CI, 72-79%), and 68% (95% CI, 62-74%), respectively. Severe late toxicity ≥ grade 3 occurred in 7% (95% CI, 3-14%). PORT showed favorable long-term efficacy and safety in SGC, especially for patients with high-grade histology. Considering that DFS continued to decrease, further clinical trials exploring treatment intensification are warranted.

PALC-02. PALLIATIVE RADIOTHERAPY FOR HAEMOSTASIS IN CHILDREN WITH CEREBRAL METASTATIC HAEMORRHAGE

Abstract BACKGROUND Among children, bleeding from brain metastases is rare. Bleeding could be caused by: cancer, treatments and chemotherapy/other drugs such as Bevacizumab, NSAIDs and anticoagulants. We report a case of brain RT after metastases bleeding. METHODS A 14-years-old boy with a negative previous medical history presented to the Emergency Department with seizures and loss of consciousness. Full-body CT scan revealed brain and renal haemorrhages and a right testicular lesion. Serum βhCG was 223,773 mIU/mL. Neurosurgical bleeding control and right orchiectomy were performed: the histopathology revealed a metastatic mixed non-seminomatous germ cell neoplasia of the testis. First-line chemotherapy (4 cycles of Cisplatin/Etoposide/Ifosfamide) and second-line treatments (Paclitaxel/Ifosfamide/Cisplatin and Gemcitabine/Paclitaxel/Oxaliplatin) were performed. Suddenly, he presented with left-sided hyposthenia and partial left hemibody seizure. CT scan revealed 2 haemorrhagic brain lesions, one in each hemisphere. Surgery was not feasible. We started anti-oedema and anti-epileptic therapy, and whole brain RT (WBRT, 36 Gy/12 fx, BEDα/β= 10 Gy= 46.8 Gy). After 5 days from the start, RT had a 7-day stop because of acute oedema and clinical deterioration. Fourth-line chemotherapy was administered with CarboPEB (1st of further 4 cycles), and then WBRT was restarted. At the end of WBRT a stereotactic RT boost to both the haemorrhagic lesions was delivered (20 Gy/10 fx, BEDα/β= 10 Gy= 24.0 Gy). As of today, eight months after the end of therapy, the patient is free from disease and βhCG is negative. CONCLUSION Palliative RT in children is a non-conventional indication, but potentially effective at providing rapid haemostasis, especially in selected cases (surgery not feasible/contraindicated, adult-type histologies, …) and it is ensuring a good tumor control and low-grade acute toxicities. Hypofractionation is suggested to balance patient comfort and treatment effectiveness, especially when life expectancy is short. The optimal RT schedule, dose and fractionations need to be further investigated.

Adjuvant chemotherapy following concurrent chemoradiation (CRT) in patients with high-risk early-stage cervical carcinoma following radical hysterectomy: Results of NRG oncology/RTOG 0724/GOG-0724.

5504 Background: To assess the efficacy of adjuvant systemic chemotherapy following CRT for patients (pts) with high-risk early-stage cervical carcinoma. Methods: Pts with clinical stage IA2, IB, or IIA cervical carcinoma with at least one of the following high-risk features after radical hysterectomy: positive pelvic nodes, positive parametrium, and/or positive para-aortic nodes were stratified by intention to use brachy (yes v no), RT (Standard v IMRT); and RT dose (45 v 50.4 Gy) then randomized 1:1 to CRT or CRT and 4 cycles of adjuvant chemotherapy with paclitaxel and carboplatin (CRT + chemo). Primary endpoint was disease-free survival (DFS: death, local or regional failure, or distant mets). Reported secondary endpoints are OS (death due to any cause) and AEs (CTCAEv4). Sample size was 235 pts (50 DFS events, HR=0.47, corresponding to an increase in 4-year DFS from 80% to 90% for the CRT + chemo arm, 80% power, 1-sided log-rank α=0.05). Multivariable analysis (MVA) used Cox regression models. Results: From 9/16/2009 to 3/2/2022, this phase III international trial enrolled 236 pts, with 212 eligible/analyzed (109 CRT and 103 CRT + chemo). Median age was 46 yrs (min-max: 25-77) and median follow-up for all pts was 4.5 yrs (min-max: 0.02-12.8). Fifty-one percent of pts identified as white, 39% as Asian, and 6% Black. Most pts had squamous cell carcinoma (76%), with 18% adenocarcinoma and 5% adenosquamous. 56% of pts had open radical hysterectomy, 23% laparoscopic, and 22% robotic. Most pts had stage IB (87%) and 74% had positive pelvic nodes. Four (4%) pts on the CRT arm and 1 (1%) patient on CRT + chemo did not receive RT. The median (min-max) RT dose delivered was 50.4 Gy (7.2-60.4). Four pts (2 on each arm) did not receive concurrent cisplatin and 27 (26%) pts did not receive adjuvant carboplatin and paclitaxel on the CRT + chemo arm. Grade 3 and 4 events occurred in 36% and 7% of CRT pts; 44% and 21% in the CRT + chemo arm. There were 50 failures, 26 and 24 on the CRT and CRT + chemo arms, respectively, with 4-yr DFS estimates of 76% (90% CI: 69%, 83%) and 77% (90% CI: 70%, 84%) for the CRT and CRT + chemo arms, respectively (HR=1.05 [90% CI: 0.65, 1.68], p=0.56). Thirty-seven of 50 first failures were distant [74%], 20 (40%) and 17 (34%) in CRT and CRT + chemo arms, respectively. On MVA, factors that were statistically significant for worse DFS were receiving vaginal brachy (p&lt;0.0001), RT dose ≥50 Gy (p=0.0021), and adenocarcinoma histology (p=0.03). Pts receiving brachy had close or positive margins. The estimated 4-yrs OS is 87% (90% CI: 82%, 93%) and 89% (90% CI: 84%, 94%) for the CRT and CRT +chemo arms, respectively (HR=0.91 [90% CI: 0.49 to 1.69]; 1-sided log-rank p=0.40). Conclusions: The addition of systemic chemotherapy following CRT didn't improve DFS or OS in cervical cancer patients with high-risk factors after radical hysterectomy. Clinical trial information: NRG Oncology/RTOG 0724/GOG-0724.

TTCC-2022-01: Niraparib and dostarlimab in locally-advanced head and neck squamous cell carcinoma treated with (chemo) radiotherapy (RADIAN).

TPS6125 Background: The prognosis of locally-advanced head and neck squamous cell carcinoma (LA-HNSCC) remains poor, with a 60% 5-year overall survival (OS) rate despite curative-intent therapies. Treatment intensification strategies with antiPD-(L)1 agents given concurrently to (chemo)radiotherapy (CRT) have failed to improve survival. New radiosensitizing agents such as PARP inhibitors have shown encouraging results in early studies, and are of special interest in cisplatin-unfit patients (pts) (Moutafi et al. 2021). Beyond radiation sensitization, PARP inhibition is predicted to trigger immune responses via STING pathway activation, and synergize with anti-PD-(L)1 agents (Sen T et al., 2019). We hypothesize that niraparib will enhance antitumor immune responses when combined with dostarlimab before and after definitive CRT and will boost RT response ultimately leading to higher disease-free survival (DFS). Methods: Trial design: RADIAN is an investigator-initiated, multi-center, non-randomized two-cohort phase 1b study of niraparib and dostarlimab in LA-HNSCC pts candidates for CRT (cohort A) or RT alone (cohort B – cisplatin unfit). Dostarlimab 500mg is given intravenously 3 weeks(w) before RT and then q/3w starting w4 post-RT for up to 14 cycles. Niraparib 200 or 300mg is given orally once daily 1w after dostarlimab until start of CRT (cohort A) or continuously until last dose of RT (Cohort B) and then continuously in 3w cycles from w4 post-RT for up to a year (14 cycles). Intensity-modulated RT (70 Grays:2Gray/fraction) and high-dose cisplatin are given as per standard-of-care. Study procedures include collection of baseline archival or fresh tumor sample for molecular profiling, PD-L1 expression and immunophenotyping; serial blood samples for circulating tumor (ct) DNA and clinical/endoscopic photographs of the tumor (baseline, pre-niraparib, pre-RT, 12w post-RT, end-of treatment, and at progression). Imaging and follow-up procedures are conducted as per standard-of-care. Key eligibility criteria: untreated, stage III to IVB laryngeal, hypopharyngeal, HPV-negative oropharyngeal SCC (stage III only if HPV-positive), and stage IVB oral cavity SCC as per TNM 8th edition;adequate organ function; no autoimmune disorders; no immunosuppressive therapy. Study objectives: primary objective is to evaluate 1-year disease free survival. Secondary objectives: safety/tolerability including RT delay/completion; locoregional and distant control, event-free survival, OS and ctDNA dynamics correlation with efficacy endpoints. Sample size: 32 evaluable pts for correlative studies are planned for enrollment (16/cohort). It is expected that experimental treatment will provide an increase of efficacy of 0.64 in terms of HR (1-year DFS of 75.9 % in cohort A and 68.2% in cohort B). Study activation: Nov 11th 2023, with 2 pts enrolled as of Feb 6th 2024. Clinical trial information: NCT05784012 .

Second primary squamous cell cancers in the HPV de-escalation Quarterback Trials.

e18049 Background: Patients with HPV oropharyngeal cancer (HPVOPC) have a cure rate approaching 90%, and will live for decades with the sequelae of therapy. Trials evaluating treatments for HPVOPC select patients by p16 status rather than using more accurate molecular testing; a fraction of these patients, approaching 5%, are HPV16 negative. Recurrent cancers are often not tested molecularly and may not be tested for p16. Applying molecular diagnostics for HPV at diagnosis and relapse can avoid significant mis-assignment, mistreatment, and inaccurate results in clinical trials. We reviewed and report results from the Quarterback Trials (QT) where molecular testing confirmed HPV status at diagnosis and recurrence. Methods: Patients entered on the QT were required to have &lt; 20 py smoking history, not be active smokers, have non-metastatic locally advanced disease, and have a molecularly confirmed HPV status, including genotype (PCR based DNA Sequencing). Subjects were treated with TPF chemotherapy for 3 cycles and patients with an adequate response were eligible for de-escalation of chemoradiotherapy (CRT) to 5600 cGy (RD). The first 20 patients were randomized to standard dose (SD) 7000 cGy (8) or RD (12). Patients who withdrew from the study or had an inadequate response to TPF, were treated with SD. Patients were monitored for recurrent disease by routine surveillance with physical examination and PET scan. Recurrences were confirmed with tissue biopsy. We performed a retrospective analysis of 2nd in-field primaries (SP) and compared them to local regional recurrences (LRF) in the entire eligible population. Results: 62 patients were consented on to the QTs. 2 patients failed screening and are not considered any further. 14 patients received 7000 cGy: 8/14 were randomized to SD, 5/14 had an inadequate response to TPF and 1/14 patient withdrew consent. One patient randomized to SD withdrew consent and stopped CRT at 5200cGy. There were 7 HPV+ LRF: (1 SD and 6 RD); and 4 molecularly documented in-field non-HPV SP squamous cell cancers: 2/14 SD (14%) and 2/46 RD (4%). 1 of 4 SP tumors was p16+; all were molecularly negative for HPV and had documented p53 mutations. Median time to LRF was 8 mo. (4-49) and 66 mo. (35-84) for SP. Median survival after LRF is 11 (4-72+) and after SP 18+ (3-36+). 4/11 (36%) of post treatment local regional squamous cancer events were not HPV related. Conclusions: Non-HPV SP SCC were not rare events in this documented HPV+, non-smoking population. SP were more common in the SD than the RD treated patients suggesting an RT dose dependency and causality, although other biologic explanations are possible. SP will increase and be a major cause of mortality in this population indicating a need for awareness during surveillance. p16 is inaccurate for determining HPV16 status at diagnosis and recurrence in HPV critical clinical trials and in-field cancer events should be molecularly assessed to determine if they are LRF or SP.

A phase II trial of reirradiation combined with pembrolizumab in patients with locoregional inoperable recurrence or second primary squamous cell carcinoma of the head and neck (HNSCC).

6049 Background: Better outcomes are needed for patients (pts) with locoregional inoperable recurrence or second primary HNSCC after prior radiation therapy. Methods: We conducted a phase II single arm trial of hyperfractionated reirradiation (ReRT, 1.2 Gy BID for total 60Gy to gross disease + margin without elective nodal radiation) plus pembrolizumab (P) (200mg q3 weeks starting day 1 of ReRT). P was continued until confirmed CR or if no CR, until disease progression or up to 24 months. All pts underwent a 3 month post ReRT PET/CT and subsequently CT neck/chest after every 3rd cycle of P. Pts included had: Locoregional recurrence or second primary HNSCC (excluding skin or salivary), were unresectable or not willing to undergo resection, one RT course completed at least 6 months prior, with &gt;50% tumor volume treated at doses &gt;45Gy, ECOG PS 0-1, a target lesion by RECIST, no distant metastasis, and no prior anti-PD-1/PD-L1. Primary endpoint was PFS, and the hypothesis was that the median PFS would increase from the historical control of 8 months (mo) to 12 mo, α=0.05, power 78%, n=48. Secondary endpoints: ORR by RECIST, OS, toxicity, QOL (EORTC). The Kaplan-Meier method was used to estimate PFS and OS. Results: In the 48 evaluable pts, median age was 65.5 (range 44-79), 62.5% male. Primary site: hypopharynx (8.3%), larynx (6.3%), nasopharynx (10.4%), oral cavity (43.7%), oropharynx (31.3%, one HPV+ pt). Median doses of P was 8, median RT dose was 60 Gy and 20.8% received proton RT, remainder IMRT. Median follow up was 49.1 months. The median PFS was 8.3 mo (95%CI 5.5-10.3), and median OS was 13.8 mo (95% CI 9.5-21.8). 1 and 3-year PFS were 28.9% and 22.3% respectively, and for OS 54.2% and 25.7%, respectively. 42 pts were evaluable for response and the ORR was 54.8% (33.3% CR, 21.4%PR), 21.4% SD, 23.8% PD. In an exploratory analysis, the median PFS was 13.8 mo (95% CI 9.1-NR) and the median OS was 57.8 mo (19.6-NR) in patients that had a response (CR/PR, n=23), with a 1 and 3-year PFS of 51.8% and 42.4%, respectively, and for OS 78.3% and 51.7%, respectively. All patients had at least one treatment related AE (TRAE), defined as possibly, probable, or definitely related to treatment. 39% of pts had a G3 TRAE and the most common ones were: aspiration, dehydration, anemia, dysphagia, dyspnea. 4 patients had a G5 TRAE (found down deceased, epistaxis, aspiration pneumonia, iRAE pneumonitis). Conclusions: Our prospective trial uniquely evaluated ReRT plus pembrolizumab in patients with locoregional recurrence/second primary HNSCC that did not undergo salvage surgery. The primary endpoint of PFS was not improved compared to historical control. PD-L1 biomarker analysis is ongoing and will be reported subsequently. Clinical trial information: NCT02289209 .

Abstract PO4-22-03: Intensity Modulated Proton Therapy (IMPT) for the Definitive Adjuvant Management of Women with Breast Cancer: A Single Institutional Experience of 5-Year Oncologic Outcomes

Abstract Purpose: There is limited data reporting the oncologic outcomes of breast cancer patients treated definitively with adjuvant proton beam therapy. Here we report a single institutional experience of oncologic outcomes, treating a predominantly vulnerable breast cancer patient population and compare these to historical standards primarily utilizing photon therapy. Materials and Methods: Unver IRB approval, we retrospectively reviewed 453 definitively treated breast cancer patients from 2016 – 2023 using adjuvant IMPT as part of their cancer care. Patients with recurrent disease, receiving re-irradiation, and those with less than 1-year of follow up were excluded from this analysis. Patients were treated with surgery and systemic therapies as per standards of care. Radiation therapy was administered using pencil beam scanning IMPT with daily image guidance. χ2 and Mann-Whitney U tests were performed to determine differences between select variables. Kaplan-Meier analysis and Cox proportional hazard models were used to analyze overall survival (OS). Results: With a median follow up of 22 months for the entire cohort, 453 patients were treated at XXXX as part of definitive adjuvant management for their breast cancer. Nearly 30% of patients self-identified as black (n=135), average patient age was 54 and 56% (n=255) self-identified as being married with approximately 25% (n=109) of patients having Medicare/Medicaid insurance. 198 patients (43.8%) had an intact breast and the remainder mastectomy of which 37.4% had reconstruction at the time of their radiation. 229 patients (50.7%) received neoadjuvant chemotherapy while 55 patients (12%) received concurrent chemotherapy which was either her2+ directed or Xeloda. The number of patients (%) corresponding to the AJCC 8th edition anatomical staging is as follows: Stage 0: 12 (2.7%); Stage I: 91 (20.1%); Stage 2: 197 (43.6%); Stage 3: 152 (33.6%). Median RT dose delivered for patients receiving comprehensive treatment was 50.4 Gy with 81% of patients receiving a boost to either scar, lumpectomy cavity and/or LN regions. Median RT dose delivered for patients receiving whole breast radiation was 42.56 Gy with a 10 Gy lumpectomy cavity boost. 5-yr OS by stage was 0: 100%; stage I: 98.8%; stage 2: 93.5%; stage 3: 90.8%. Five-year OS for black, white and other race patients were 85.3%, 95.8% and 96%, respectively (White as Ref: HR 3.176, 95% CI: 1.313-7.681, p=0.010 for black patients). For the entire cohort, patients with triple negative disease had a 5-yr OS of 80.4% (HR: 4.33, 95% CI 1.87-10.04, p&amp;lt; 0.001) and there was no difference in OS when insurance status was considered (p=0.378). Conclusions: To the best of our knowledge this represents the largest series of definitively treated breast cancer patients utilizing adjuvant proton therapy and the 5-year OS rates in our analysis coincide with published standards1. Results from the on-going randomized RADCOMP study will provide further guidance as to which patients benefit the most from proton therapy and will further support equivalent oncological outcomes when compared to photon therapy. 1. Weiss A, Chavez-MacGregor M, Lichtensztajn DY, et al. Validation study of the American Joint Committee on Cancer eighth edition prognostic stage compared with the anatomic stage in breast cancer. JAMA Oncol. 4(2):203-209, 2018. Citation Format: Elizabeth Nichols, Gurbani Singh, Desiree Lejano, Sarah McAvoy, Mark Mishra, Melissa Vyfhuis. Intensity Modulated Proton Therapy (IMPT) for the Definitive Adjuvant Management of Women with Breast Cancer: A Single Institutional Experience of 5-Year Oncologic Outcomes [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-22-03.

1566: Intensification of RT dose, rather than, chemotherapy, in Total Neoadjuvant Therapy for rectal cancer

1566: Intensification of RT dose, rather than, chemotherapy, in Total Neoadjuvant Therapy for rectal cancer

1293: Immunotherapy-related hypothyroidism on head and neck cancer: impact of RT dose to the thyroid gland

1293: Immunotherapy-related hypothyroidism on head and neck cancer: impact of RT dose to the thyroid gland

ImmunoChemoradiation for Non-Small Cell Lung Cancer: A Meta-Analysis of Factors Influencing Survival Benefit in Combination Trials

PurposeAdding immune checkpoint blockade (ICB) to concurrent chemoradiotherapy (cCRT) has improved overall survival (OS) for inoperable locally advanced non-small cell lung cancer (LA-NSCLC). Trials of cCRT-ICB are heterogeneous for factors such as tumor stage and histology, PDL1 status and cCRT-ICB schedules. We therefore aimed to determine the ICB contribution to survival across studies and identify factors associated with survival gain. Methods and materialsData were collated from cCRT-ICB clinical studies published 2018-2022 which treated 2196 NSCLC patients (99% stage III). Associations between 2-year OS and ICB, CRT, patient and tumor factors were investigated using meta-regression. A published model of survival following RT or CRT was extended to include ICB effects. The model was fitted simultaneously to the cCRT-ICB data and data previously compiled for RT/CRT treatments alone. The net ICB contribution (‘OS gain’) and its associations with factors were described by fitted values of ICB terms added to the model. Statistical significance was determined by likelihood-ratio testing. ResultsThe gain in 2-year OS from ICB was 9.9% overall (95% CI: 7.6%, 12.2%; p=0.018). Both OS gain and 2-year OS itself rose with increasing planned ICB duration (p=0.008, 0.002 respectively) and with tumor PDL1 ≥1% (p=0.034, 0.023). Fitted OS gains were also greater for patients with stage IIIB/C disease (p=0.021). OS gain was not associated with tumor histology, patient performance status, RT dose, ICB drug type (anti-PDL1 vs anti-PD1) or whether ICB began concurrently with or after cCRT. ConclusionFitted gains in 2-year OS due to ICB were higher in cohorts with greater fractions of stage IIIB/C patients and patients with tumor PDL1 ≥1%. OS gain was also significantly higher in a single cohort with a planned ICB duration of two years rather than one, but was not associated with whether ICB treatment began during vs after CRT.

Co-relation of Portal Vein Tumour Thrombus Response With Survival Function Following Robotic Radiosurgery in Vascular Invasive Hepatocellular Carcinoma

Purpose or ObjectiveProspective evaluation of stereotactic body radiotherapy (SBRT) with Robotic Radiosurgery in hepatocellular carcinoma patients with macrovascular invasion (HCC-PVT). Materials and MethodsPatients with inoperable HCC-PVT, good performance score (PS0-1) and preserved liver function (up to Child Pugh B7) were accrued after ethical and scientific committee approval [CTRI: 2022/01/050234] for treatment on Robotic Radiosurgery (M6) and planned with Multiplan (iDMS V2.0). Triple-phase contrast computed tomography (CT) scan was done for contouring and gross tumor volume (GTV) included contrast enhancing mass within main portal vein and adjacent parenchymal disease. Dose prescription was as per risk stratification protocol (22- 50Gy in 5 fractions) while achieving the constraints of mean liver dose <15Gy, 800 cc liver <8Gy and the duodenum max of <24 Gy). Response assessment done at 2 months follow up for recanalization. Patient and treatment related factors evaluated for influence in survival function. ResultsBetween Jan 2017 till May 2022, 317 consecutive HCC with PVT patients were screened and 219 patients were accrued [male 92%, CP score 5-7 90%, mean age 63 years (38-85yrs), CLIP <3: 84 (40%), 3-6 117 (56%), infective etiology 9.5%, Performance status (PS) 0-37%; 1-56%]. Among 209 consecutive patients after accrual SBRT treatment done (10 patients were excluded after accrual due to ascites and decompensation), 139 were evaluable for response assessment (>2 mo follow up). At mean follow up of 10.2 months (SD 8.43), 88 (63%) patients expired and 51 (36%) were alive. 82 (59%) patients had recanalization of PVT (response), 57 (41%) pts did not recanalize, 28 (17%) had progressive disease had progressive/metastatic disease prior to response evaluation (<2 months). Mean overall survival in responders and non-responders were 18.4 (SE 2.52) and 9.34 month (SE 0.81) respectively (p<0.001). Mean survival in patients with PS0, PS1 and PS2 were 17, 11.7 and 9.7 months (p- 0.019) respectively. Overall survival (OS) in partial recanalization, bland thrombus and complete recanalization was 12.4, 14.1, 30.3 months respectively (p-0.002). Adjuvant sorafenib, Barcelona Clinic Liver Classification (BCLC) stage, gender, age, RT dose did not influence response to treatment. Recanalization rate was higher in good PS patients (p-0.019). OS in patients with response to treatment, no response to treatment, fit but not accrued and not suitable patients were 18.4, 9.34, 5.9, 2.6 months respectively (p-<0.001). 36/139 patients (24%) had RILD [10 (7.2%) had Classic Radiation induced liver disease (RILD) & 26 (19%) had non-classic RILD]. Derangement in Child Pugh Score (CP score change) by more than 2 was seen in 30 (24%) within 2-month period after Robotic Radiosurgery. 18 (13%) had unplanned admissions, two patients required embolization due to fiducial related bleeding, 20 (14%) had ascites of which 9 (6%) patients required abdominocentesis. ConclusionPVT response or recanalization after SBRT is a statistically significant prognostic factor for survival function in HCC-PVT.