Re-irradiation in clinical practice: Results of an international patterns of care survey within the framework of the ESTRO-EORTC E2-RADIatE platform

Reirradiation Practice in Gynecological Cancer: Insights from a National Survey in Spain

PURPOSE

Given the lack of standardisation in gynecological cancer reirradiation, the Gyneacologial Radiation Oncology (GINECOR) working group on behalf of the Spanish Society of Radiation Oncology (SEOR), works towards to inquire the current state of reirradiation practices among the radiation oncology departments in Spain.

METHODS

An online 37-question survey was sent to all GINECOR members, representing most Spanish centers. The survey addressed general aspects of reirradiation, including experience, reirradiation sites, and techniques used. It included seven clinical case scenarios on reirradiation, and a final section on technical aspects of external beam radiotherapy (EBRT) and brachytherapy (BT) treatment. Descriptive statistics were used for data analysis.

RESULTS

Out of 58 centers, 29 responded, with 51.7% performing ≥ 5 reirradiation cases annually. While most centers offer multiple techniques, only 16/29 have access to BT. For in-field local relapse with surgery contraindicated, 79.3% performed BT in endometrial cancer, but only 27.5% treated with BT in cervical cancer recurrence. In this case, 17.2% used SBRT. For endometrial and cervical cancer, 44.8% and 65.4% of centers prescribed doses based on organ-at-risk tolerance, respectively. For pelvic wall/parametrial in-field relapse, 46.4% of the centres reirradiated with stereotactic body radiotherapy (SBRT), and 32.1% with BT. In nodal reirradiation, SBRT was preferred by 90% of centers. Variability was observed in target volume definitions for EBRT and proton therapy.

CONCLUSIONS

Reirradiation for gynecological cancer remains unstandardized, presenting significant challenges in clinical practice. To improve reirradiation protocols in gynecological cancer, the GINECOR working group is currently conducting a systematic review and formulating Delphi recommendations.

Enhancing Expertise in Reirradiation: Results from a Training Workshop Organized by Unicancer, the Federation of French Cancer Centers

Reirradiation (reRT) is an increasingly significant therapeutic option for managing recurrent cancers. Its implementation requires multidisciplinary expertise to address challenges such as patient selection, cumulative dose management, and advanced imaging integration. Despite its growing use, formal reRT-focused education remains limited. To address this gap, a national workshop was organized to enhance knowledge, promote collaboration, and establish a working group for reRT in France.Conducted in June 2024, the workshop was organized by Unicancer Formation, the training body of Unicancer, the federation of French cancer centers, which is a certified training organization ensuring compliance with national quality standards. The workshop aimed to achieve three core objectives: identifying eligible patients using advanced imaging and artificial intelligence, selecting optimal reRT techniques while addressing dose summation challenges, and fostering research and clinical trial participation. The program combined expert-led lectures, case-based discussions, and group sessions. A roadmap guided the program's structure, with knowledge assessed through pre- and post-training multiple-choice questionnaires (MCQs) on clinical eligibility, dose management, imaging integration, and research development.Among 78 participants (62.7% radiation oncologists, 26.9% physicists, 10.4% radiation therapists), most were senior professionals (69.2%), representing cancer centers (46.2%), liberal practices (30.7%), and university hospitals (17.9%). MCQ scores improved significantly from 5.88 ± 1.29 to 7.74 ± 1.91 (p < 0.0001), with an average gain of 1.86 ± 1.51 points.The workshop significantly improved reRT-related knowledge and demonstrated the value of structured education in standardizing practices. Establishing a national working group lays the groundwork for future collaborative research and clinical advancements in reRT.

Practice Patterns of Reirradiation for Brain and Spinal Tumors-An International Survey From the Reirradiation Collaborative Group (ReCOG)

PURPOSE

An international workshop was convened by the Reirradiation Collaborative Group. We conducted a survey among the invited attendants to assess practice patterns of reirradiation for central nervous system tumors.

METHODS AND MATERIALS

A web-based survey regarding central nervous system reirradiation was distributed to an international group of radiation oncologists and medical physicists via email.

RESULTS

Sixty-six respondents from 20 countries completed at least one section of the survey. The most important clinical considerations were treatment goal, degree of overlap, and cumulative dose. Among technical challenges, uncertainties in tolerance of organs at risk (OARs), tissue recovery factors (TRFs) and dose accumulation ranked the highest. Most respondents (68%) used a planning OAR volume with 0 to 3 mm margin. Highly conformal radiation techniques were preferred, including stereotactic body radiation therapy for spine (85%), intensity modulated radiation therapy for adult primary brain tumors (93%), and intensity modulated radiation therapy (100%) and proton therapy (83%) for pediatric cases. Most performed dose accumulation (65%) and evaluated cumulative biological (ie, equieffective) dose (88%). Sixty-one percent preferred rigid registration, whereas 35% used deformable registration, most commonly in pediatric cases (67%). The most frequently used α/β value for OARs was 2 Gy (76%). There was no clear consensus on OAR tolerance for any disease site. Different dose metrics were used for evaluation, including Dmax (48%) and D0.1cc (48%). Most (79%) considered time intervals between radiation courses. For adult primary brain tumors and brain metastasis, 50% and 46% recommended against reirradiation within a short interval (3-6 months). Most respondents (52%) used time dependent TRFs.

CONCLUSIONS

Among respondents, there are substantial variations in approaches to reirradiation (eg, addition of systemic therapy) and uncertainties in technical implementation (eg, OAR tolerance, TRF, and dose accumulation). Future collaborative registry-based and prospective studies should help address these uncertainties.

Radiobiologically equivalent deformable dose mapping for re-irradiation planning: Implementation, robustness, and dosimetric benefits

BACKGROUND

Re-irradiation in radiotherapy presents complexities that require dedicated tools to generate optimal re-treatment plans. This study presents a robust workflow that considers fractionation size, anatomical variations between treatments, and cumulative bias doses to improve the re-irradiation planning process.

METHODS

The workflow was automated in MIM® Software and the Elekta© Monaco® treatment planning system. Prior treatment doses are deformably mapped, converted to equivalent dose in 2 Gy fractions (EQD2), and accumulated onto the re-treatment planning CT. Two MIM extensions were developed to estimate voxel-wise dose mapping uncertainties and to convert the cumulative EQD2 into a physical dose distribution equivalent to the re-treatment fractionation size. This dose distribution is used in Monaco as bias to optimize the re-irradiation plan. The workflow was retrospectively tested with data from 14 patients, and the outcomes were compared to the manually optimized plans (MOPs) clinically utilized.

RESULTS

Bias-dose guided plans (BDGPs) demonstrated a median reduction of the critical organ at risk (OAR) cumulative EQD2 metrics of 240 cGy (range: 1909 cGy, -187 cGy, p = 0.002). BDGPs allowed higher target coverage in cases where the MOP approach implied dose de-escalation of the target. The dose mapping uncertainties resulted in OAR cumulative EQD2 metrics increments ranging from 10 cGy to 730 cGy.

CONCLUSIONS

We introduced a re-irradiation planning workflow using commercially available software that accounts for anatomic and fraction size variations and improves planning efficiency. Employing voxel-level bias dose guidance demonstrated OAR-sparing benefits while maximizing prescription dose coverage to targets. The workflow's robustness tools aid informed clinical decision-making.

FLASH proton reirradiation, with or without hypofractionation, reduces chronic toxicity in the normal murine intestine, skin, and bone

BACKGROUND AND PURPOSE

The normal tissue sparing afforded by FLASH radiotherapy is being intensely investigated for potential clinical translation. Here, we studied the effects of FLASH proton radiotherapy (F-PRT) in the reirradiation setting, with or without hypofractionation. Chronic toxicities in three murine models of normal tissue toxicity including the intestine, skin, and bone were investigated.

MATERIALS AND METHODS

In studies of the intestine, single-dose irradiation was performed with 12 Gy of standard proton RT (S-PRT), followed by a second dose of 12 Gy of F-PRT or S-PRT. Additionally, a hypofractionation scheme was applied in the reirradiation setting (3 x 6.4 Gy of F-PRT or S-PRT, given every 48 hrs). In studies of skin/bone of the murine leg, 15 Gy of S-PRT was followed by hypofractionated reirradiation with F-PRT or S-PRT (3 x 11 Gy).

RESULTS

Compared to reirradiation with S-PRT, F-PRT induced less intestinal fibrosis and collagen deposition that was accompanied by significantly increased survival rate, demonstrating its protective effects on intestinal tissues in the reirradiation setting. In previously irradiated leg tissues, reirradiation with hypofractionated F-PRT created transient dermatitis that fully resolved in contrast to reirradiation with hypofractionated S-PRT. Lymphedema was also alleviated after a second course of radiation with F-PRT, along with significant reductions in the accumulation of fibrous connective tissue in the skin, compared to mice reirradiated with S-PRT. The delivery of a second course of fractionated S-PRT induced tibial fractures in 83.3% of the mice, whereas only 20% of mice reirradiated with F-PRT presented with fractures.

CONCLUSION

These studies provide the first evidence of the sparing effects of F-PRT in the setting of hypofractionated reirradiation. The results support FLASH as highly relevant to the reirradiation regimen where it exhibits significant potential to minimize chronic complications for patients undergoing RT.

Iron Oxide Nanoparticles as Enhancers for Radiotherapy of Tumors

This research aimed to evaluate the potency of preparation based on heparinized iron oxide nanoparticles (hIONPs) in combination with radiation therapy, including magnetic delivery via the applied magnetic field (AMF), in sarcoma and cervical cancer models. For in vitro studies, cells of rhabdomyosarcoma (RD), fibrosarcoma (HT1080), and cervical cancer (HeLa S3) were treated with hIONPs and analyzed for survival rate and hIONP uptake. Then, cell morphology, cell cycle, increase of reactive oxygen species, mitochondria depolarization, and ability to form colonies were assessed for combined treatment (hIONPs + 3Gy). For in vivo research, hIONPs were administered once in the hybrids of CBAxC57Bl/6j mice, grafted with sarcoma (S37) and cervical cancer (CC5) strains. The ultimate in vivo treatment modes were: (1) i.v. hIONPs (14 μg/kg) + 5 Gy; (2) i.v. hIONPs (14 μg/kg) + AMF + 5 Gy; and (3) i.t. hIONPs (2,8 μg/kg) + 5 Gy. The overall survival rates, increase in life expectancy, inhibition of tumor growth (tumor growth inhibition), and degree of inhibition (T/C) were determined, and pathomorphological changes were assessed in experimental groups. The combined treatment in vitro (hIONPs + 3Gy) promotes multiple tumor cell death with high-severity peroxide effects compared with other groups. The sarcoma cells were more sensitive than cervical cancer cells. For in vivo, an enhancing effect was revealed by the combination of radiotherapy and magnetic-delivered hIONPs. For S37 tumor, the treatment regimen was characterized as having a high antitumor effect, ≪++++ ≫, with a 20% cure rate of mice. For the CC5 tumor, the effect was accompanied by the inhibition of tumor growth, an increase in the life expectancy of animals, and was characterized as a significant antitumor effect, ≪+++/++ ≫. From the data obtained, it can be concluded that the radiosensitizing potential of hIONPs may be taken as a basis of combined radiation treatment protocols.

Individual Sensitivity for Radiotherapy-related Adverse Tissue Reactions in Patients Treated Twice for Metachronous Cancers

The role of genetics in susceptibility to radiotherapy-induced toxicities is unclear. A strong impact of genetics should cause correlated toxicities in patients with metachronous double radiotherapy. We ascertained information about demographics, lifestyle, radiotherapy and early toxicities in irradiated tissues for a retrospective cohort of 98 patients from 2 hospitals who underwent two metachronous radiotherapeutic treatments (2000-2022) of different anatomical regions. European Organisation for Research and Treatment of Cancer/Radiation Therapy Oncology Group (EORTC/RTOG) toxicity scores per organ system were combined to a single mean score. We considered as genetic component the variation of toxicity not explained by radiation dose to the tumor, age at radiotherapy, sex, smoking status, and surgery. Variance components of toxicity were evaluated by ordinal logistic regression with random intercept. Common site combinations were breast/contralateral breast (N = 16), breast/endometrium (N = 6), and cervix/breast (N = 5). Mean toxicity over exposed tissues was 0.70 (range, 0-3). Prescribed radiation dose was significantly associated with mean toxicity, with a 5% (95% CI 3-8) increase of the odds for a higher toxicity level per Gy. Sex, surgery, age and smoking were not. There was no genetic contribution to risk of toxicities after adjustment. Toxicity levels were not more similar within patients than between patients, suggesting a negligible impact of genotype on radiotherapy-related toxicities.

Ongoing prospective studies on reirradiation: A systematic review of a clinical trials database

INTRODUCTION

Reirradiation has gained increasing interest, as advances in systemic therapy increase the survival of patients with cancer, and modern radiation techniques allow more precise treatments. However, high-quality prospective evidence on the safety and efficacy of reirradiation to guide clinical practice remains scarce. This systematic review evaluates ongoing prospective studies on reirradiation to identify research gaps and priorities.

METHODS

A systematic review of ClinicalTrials.gov was conducted on July 11, 2024, using search terms related to reirradiation. Inclusion criteria were prospective studies that were "recruiting," "not yet recruiting," or "active, not recruiting." Studies with published results, retrospective, and in-silico studies were excluded. The review followed PRISMA 2020 guidelines and recommendations for systematic searches of clinical trial registries.

RESULTS

Among 1026 identified studies, 307 were screened, 99 were included. Fourty (40%) focused on central nervous system (CNS), 23 (23%) head and neck, and 17 (17%) on pelvic reirradiation. Most studies (90%) were interventional, with 32 (32%) phase II and 4 (4%) phase III trials. Sixteen trials were randomized (RCTs), including the 4 phase III trials for recurrent glioblastoma, rectal and nasopharyngeal cancer. Ten dose escalation trials focus on recurrent prostate, rectal, and non-small cell lung cancer as well as glioma. Modern high-precision radiotherapy techniques were frequently used, with 21 (21%) studies using stereotactic radiotherapy and 17 (17%) using particle therapy. Combinations with systemic therapies were investigated in 41 (41%) studies.

CONCLUSION

Ongoing studies most frequently focus on CNS, head and neck, and pelvic reirradiation. There remains a critical need for RCTs, in particular for lung, breast, and gynecological cancers. Dose escalation trials, application of precision radiation techniques and combinations with modern systemic therapy may help define the optimal multimodality treatment schedules.

FCB-CHOPS: An Evolution of a Commonly Used Acronym for Evaluating Radiation Treatment Plans

Checklists have been used across many fields as a systematic framework to reduce human error and improve safety. In radiation oncology, the CB-CHOP acronym was previously developed as a tool to aid physicians in assessing the quality of radiation treatment plans for approval. This manuscript updates the acronym for the modern era with the addition of F and S to create FCB-CHOPS: fusion, contours, beams, coverage, heterogeneity, organs at risk, prescription, and dose summation. These 2 additions reflect the evolution and importance of image fusion to aid in the delineation of targets and organs at risk and dose summation to reflect the increased incidence of reirradiation and the need to consider prior treatment courses in the final plan evaluation. Utilization of this and similar checklists is critical in maintaining high-quality and safe radiation oncology treatments.

Reirradiation in Paediatric Tumours of the Central Nervous System: Outcome and Side Effects After Implementing National Guidelines

AIMS

Reirradiation is becoming more frequently used in paediatric tumours of the central nervous system (CNS). To fill the void of clinical guidelines, the Swedish Working Group of Paediatric Radiotherapy compiled consensus guidelines on reirradiation in 2019. The aim of this study was to evaluate the outcome of children reirradiated for CNS tumours since implementing the guidelines.

MATERIAL AND METHODS

All children in Sweden who were reirradiated for CNS tumours between 2019 and 2023 were retrospectively analysed. Data were collected on patient and treatment characteristics, outcome, and severe side effects. Radiation treatment plans were reviewed, and cumulative doses to organs at risk at reirradiation were extracted following rigid registration.

RESULTS

Thirty-one patients (male 55%, female 45%) were included, and the median age at start of reirradiation was 10.2 years. The median time between primary irradiation and reirradiation was 19 months (range 2-141). The most common treatment intent at reirradiation was palliative (68%), followed by curative (32%). With a median follow-up of 8.5 months (range 0-49), the median overall survival from the end of reirradiation was 11.4 months. In the 8 patients where the treatment goal at reirradiation was symptom relief, 6 patients (75%) had relief of symptoms. The median cumulative near maximum doses (D2%) to the brain, brainstem, and chiasm/optic nerves were 71 GyEQD2 (range 44-102), 72 GyEQD2 (range 0-94), and 40 GyEQD2 (range 0-76), respectively. Following reirradiation, only 2 patients had grade ≥3 side effects. One with transient neurological deficit and one with rapid onset of blindness that persisted.

CONCLUSION

The implementation of national guidelines has harmonised the way paediatric patients are reirradiated for CNS tumours in Sweden. A structured follow-up shows that severe side effects are rare despite high cumulative doses to organs at risk, and that reirradiation can offer relief of symptoms and/or local control for selected patients.

Reirradiation of bone metastasis: A narrative review of the literature

Patients with bone metastasis are prevalent among those receiving palliative radiotherapy (RT), with approximately 20 % requiring reirradiation (reirradiation). The goal of bone reirradiation may be local control (oligoreoccurrence or oligoprogression of a previously treated lesion or in a previous treatment field) or symptomatic (threatening or painful progression). Published data on bone reirradiation indicate almost two-thirds of overall pain response. The primary organ at risk (especially for spine treatment) is the spinal cord. The risk of radiation myelitis is<1 % for cumulative doses of<50Gy. Intensity-modulated RT (IMRT) and stereotactic RT (SRT) appear to be safer than three-dimensional RT (3DRT), although randomized trials comparing these techniques in reirradiation are lacking. Reirradiation requires multidisciplinary assessment. Alternative treatments for bone metastases (surgery, interventional radiology, etc.) must be considered. Patients should have a performance status≤2, with at least a 1-month interval between treatments. The planning process involves reviewing previous RT plans, cautious dose adjustments, and precise target delineation and dose distribution to minimize toxicity. Cumulative dosimetry, patient consent, and vigilant post-treatment monitoring and dose reporting are crucial.

Criteria for Re-Irradiation

BACKGROUND

The treatment options for patients with progressive malignant tumors despite primary radiotherapy are often limited. In selected cases, re-irradiation can be offered. This article concerns the selection criteria and results of re-irradiation for certain types of cancer.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, with particular attention to glio - blastoma, head and neck tumors, and prostatic carcinoma.

RESULTS

The published studies of re-irradiation are few in number and often of limited methodological quality. For glioblastoma, a randomized controlled trial (RCT) found that adding re-irradiation to treatment with bevacizumab yielded no significant improvement in either median progression-free survival or median overall survival (hazard ratio [HR] 0.73; p = 0.05 and HR 0.98; p = 0.46, respec - tively). Re-irradiation is a treatment option for locoregional recurrences of head and neck tumors after primary radiotherapy, but it carries a risk of serious side effects. For unresectable recurrences of nasopharyngeal carcinoma, an RCT has shown that hyperfractionated re-irradiation is more effective than normofractionated re-irradiation (overall survival: HR 0.54, p = 0.014). For locally recurrent prostatic carcinoma after radiotherapy, re-irradiation can yield good oncologic outcomes with an acceptable level of urogenital and gastrointestinal side effects (5-year recurrence-free survival: stereotactic body radiation therapy (SBRT), 58%; high dose rate (HDR) brachytherapy, 77%; versus salvage prostatectomy, 72%). RCTs on this topic are lacking.

CONCLUSION

Re-irradiation is a treatment option for selected cancer patients. As the available scientific evidence is limited, multidisciplinary collaboration and participatory decision-making are particularly important.

Investigation of the linear accelerator low dose rate mode for pulsed low-dose-rate radiotherapy delivery

Purpose. Pulsed volumetric modulated arc therapy (VMAT) was proposed as an advanced treatment that combines the biological benefits of pulsed low dose rate (PLDR) and the dosimetric benefits of the intensity-modulated beams. In our conventional pulsed VMAT technique, a daily fractional dose of 200 cGy is delivered in 10 arcs with 3 min intervals between the arcs. In this study, we are testing the feasibility of pulsed VMAT that omits the need to split into ten arcs and excludes any beam-off gaps.Methods. The study was conducted using computed tomographic images of 24 patients previously treated at our institution with the conventional PLDR technique. Our newly installed Elekta machine has a low dose rate option on the order of 25 MU min-1. PLDR requires an effective dose rate of 6.7 cGy min-1with attention being paid to the maximum dose received within any point within the target not to exceed 13 cGy min-1. The quality of treatment plans was judged based on dose-volume histograms, isodose distribution, dose conformality to the target, and target dose homogeneity. The dose delivery accuracy was assessed by measurements using theMatriXXEvolution2D array system.Results. All cases were normalized to cover 95% of the target volume with 100% of the prescription dose. The average conformity index was 1.03 ± 0.08 while the average homogeneity index was 1.05 ± 0.02. The maximum reported dose rate at any point within the target was 10.44 cGy min-1. The mean dose rate for all pulsed VMAT plans was 6.88 ± 0.1 cGy min-1. All cases passed our gamma analysis with an average passing rate of 99.00% ± 0.48%.Conclusion. The study showed the applicability of planning pulsed VMAT using Eclipse and its successful delivery on our Elekta linac. Pulsed VMAT using the machine's low dose rate mode is more efficient than our previous pulsed VMAT delivery.

FLASH proton reirradiation, with or without hypofractionation, mitigates chronic toxicity in the normal murine intestine, skin, and bone

Background and purpose

The normal tissue sparing afforded by FLASH radiotherapy (RT) is being intensely investigated for potential clinical translation. Here, we studied the effects of FLASH proton RT (F-PRT) in the reirradiation setting, with or without hypofractionation. Chronic toxicities in three murine models of normal tissue toxicity including the intestine, skin, and bone were investigated.

Materials and methods

In studies of the intestine, single-dose irradiation was performed with 12 Gy of Standard proton RT (S-PRT), followed by a second dose of 12 Gy of F-PRT or S-PRT. Additionally, a hypofractionation scheme was applied in the reirradiation setting (3 x 6.4 Gy of F-PRT or S-PRT, given every 48 hrs). In studies of skin/bone of the murine leg, 15 Gy of S-PRT was followed by hypofractionated reirradiation with F-PRT or S-PRT (3 x 11 Gy).

Results

Compared to reirradiation with S-PRT, F-PRT reduced intestinal fibrosis and collagen deposition in the reirradiation setting and significantly increased survival rate, demonstrating its protective effects on intestinal tissues. In previously irradiated leg tissues, reirradiation with hypofractionated F-PRT created transient dermatitis that fully resolved in contrast to reirradiation with hypofractionated S-PRT. Lymphedema was also alleviated after a second course of radiation with F-PRT, along with significant reductions in the accumulation of fibrous connective tissue in the skin compared to mice reirradiated with S-PRT. The delivery of a second course of fractionated S-PRT induced tibial fractures in 83.3% of the mice, whereas only 20% of mice reirradiated with F-PRT presented with fractures.

Conclusion

These studies provide the first evidence of the sparing effects of F-PRT, in the setting of hypofractionated reirradiation. The results support FLASH as highly relevant to the reirradiation regimen where it exhibits significant potential to minimize chronic complications for patients undergoing RT.

Interdisciplinary Approach Toward Reirradiation of Cancer Patients

As systemic therapies, alongside radiation, for cancer treatment continue to evolve, the radiation oncology community is facing an increasing number of reirradiation (re-RT) of tumor sites subject to recurrences. There are multiple factors associated with choosing re-RT as a treatment option for a previously irradiated site. The factors include the site of previous radiotherapy (RT), the current extent of the disease, the nature of recurrence, the technique used for previous irradiation, and the previous RT details including dose and dose fractionation. There is a persistent heterogeneity in the workflow and decision-making in cancer care centers worldwide. The current review is an attempt to dive into the practices of decision-making for re-RT, interdisciplinary attention given to the re-RT patients, and acceptable doses to the organ at risk (OAR) deduced from the understanding of previous RT and radiobiology of the tumor and sites evidence of better techniques for effective execution.

Multi-centre evaluation of variation in cumulative dose assessment in reirradiation scenarios

BACKGROUND AND PURPOSE

Safe reirradiation relies on assessment of cumulative doses to organs at risk (OARs) across multiple treatments. Different clinical pathways can result in inconsistent estimates. Here, we quantified the consistency of cumulative dose to OARs across multi-centre clinical pathways.

MATERIAL AND METHODS

We provided DICOM planning CT, structures and doses for two reirradiation cases: head & neck (HN) and lung. Participants followed their standard pathway to assess the cumulative physical and EQD2 doses (with provided α/β values), and submitted DVH metrics and a description of their pathways. Participants could also submit physical dose distributions from Course 1 mapped onto the CT of Course 2 using their best available tools. To assess isolated impact of image registrations, a single observer accumulated each submitted spatially mapped physical dose for every participating centre.

RESULTS

Cumulative dose assessment was performed by 24 participants. Pathways included rigid (n = 15), or deformable (n = 5) image registration-based 3D dose summation, visual inspection of isodose line contours (n = 1), or summation of dose metrics extracted from each course (n = 3). Largest variations were observed in near-maximum cumulative doses (25.4 - 41.8 Gy for HN, 2.4 - 33.8 Gy for lung OARs), with lower variations in volume/dose metrics to large organs. A standardised process involving spatial mapping of the first course dose to the second course CT followed by summation improved consistency for most near-maximum dose metrics in both cases.

CONCLUSION

Large variations highlight the uncertainty in reporting cumulative doses in reirradiation scenarios, with implications for outcome analysis and understanding of published doses. Using a standardised workflow potentially including spatially mapped doses improves consistency in determination of accumulated dose in reirradiation scenarios.

Interventional radiotherapy (brachytherapy) for re-irradiation of recurrent head and neck malignancies: oncologic outcomes and morbidity

Objective

Management of recurrent head and neck cancer (HNC) is challenging. One option in previously irradiated patients is re-irradiation using interventional radiotherapy (IRT), the modern form of brachytherapy. Re-irradiation using IRT can be delivered as an exclusive strategy for salvage or through a postoperative or perioperative approach after salvage surgery. The aim of the present study is to analyse a bicentric Italian series focusing on the use of IRT as a re-irradiation modality and assess the resulting evidence concerning oncologic outcomes and morbidity.

Methods

This is a retrospective study performed in two referral centres in Italy: Policlinico Universitario Agostino Gemelli in Rome and Azienda Ospedaliera Universitaria in Sassari. All patients who had previously received a full course of external beam RT and have been re-irradiated using high-dose-rate IRT between December 2010 and June 2023 were included. Patients were retreated either by a combination of surgery and perioperative (either endocavitary or interstitial) IRT or by exclusive interstitial IRT.

Results

Thirty-four patients were included in the present series, 2 of whom underwent more than one IRT re-irradiation. Notably, no patient reported specific IRT-related toxicities. Median follow-up, excluding patients who died of HNC, was 24.5 months. Two-year local relapse-free survival was 26%, disease-specific survival 39.1%, and overall survival 36.6%.

Conclusions

The present series is the largest reported experience of re-irradiation by IRT for HNC in Italy. The very low rate of toxicity confirms IRT as the safest re-irradiation modality. It is noteworthy to underline that IRT is a multidisciplinary strategy based on the close cooperation between surgeons and radiation oncologists during every phase, from the recommendation of treatment and implantation in the operating theatre, to its prescription and dose painting.