Breast Radiation Treatment Research Articles

Transit-guided radiation therapy: a novel patient monitoring approach

Background and purposeTransit-Guided Radiation Therapy (TGRT) is a novel technique that uses the transit portal images (TPIs) acquired with Electronic Portal Image Devices (EPID) to quantify patient position errors during the treatment. It has been validated using anthropomorphic phantoms but a validation in a clinical setting was lacking. A pilot clinical study is presented to confirm our previous results. Materials and methodsA prospective study was conducted between June and December 2022 with patients who received whole-brain or breast radiotherapy treatments. The selected treatments were composed of radiation fields using skin-flash, where the body contour projected a sharp edge on the EPID which has been used as a surrogate of the true patient position. Daily imaging procedures were applied as scheduled before running the one- and two-parameter model (1PM and 2PM) of the TGRT formalism on the acquired TPIs to independently estimate the patient position errors. Results43 patients and 1015 TPIs have been assessed. The 2PM showed a better correlation with the true position errors (R2 = 0.76 vs. 0.73), a lower detection threshold (0.77 mm vs. 1.24 mm), and a lower overcorrection risk above the detection threshold (7.0 % vs. 11.1 %) than the 1PM. Overall, the 2PM would have significantly reduced the true position errors by a factor of 0.58 (0.49 – 1.27) (p < 0.0001). ConclusionThe TGRT technique has confirmed the ability to reduce the position errors in a clinical setting, demonstrating the potential to enhance the patient position monitoring without increasing treatment time or patient dose.

432 - A review of accuracy of optical surface imaging systems for setup verification during breast radiotherapy treatment

432 - A review of accuracy of optical surface imaging systems for setup verification during breast radiotherapy treatment

1661: National benchmarking of lung SABR and breast radiotherapy treatment plans using cloud-based ProKnow

1661: National benchmarking of lung SABR and breast radiotherapy treatment plans using cloud-based ProKnow

The Role of MRI in Breast Cancer and Breast Conservation Therapy.

Contrast-enhanced breast MRI has an established role in aiding in the detection, evaluation, and management of breast cancer. This article discusses MRI sequences, the clinical utility of MRI, and how MRI has been evaluated for use in breast radiotherapy treatment planning. We highlight the contribution of MRI in the decision-making regarding selecting appropriate candidates for breast conservation therapy and review the emerging role of MRI-guided breast radiotherapy.

Automation to facilitate optimisation of breast radiotherapy treatments using EPID-based in vivo dosimetry

Objective. To use automation to facilitate the monitoring of each treatment fraction using an electronic portal imaging device (EPID) based in vivo dosimetry (IVD) system, allowing optimisation of breast radiotherapy delivery for individual patients and cohorts. Approach. A suite of in-house software was developed to reduce the number of manual interactions with the commercial IVD system, dosimetry check. An EPID specific pixel sensitivity map facilitated use of the EPID panel away from the central axis. Point dose difference and the change in standard deviation in dose were identified as useful dose metrics, with standard deviation used in preference to gamma in the presence of a systematic dose offset. Automated IVD was completed for 3261 fractions across 704 patients receiving breast radiotherapy. Main results. Multiple opportunities for treatment optimisation were identified for individual patients and across patient cohorts as a result of successful implementation of automated IVD. 5.1% of analysed fractions were out of tolerance with 27.1% of these considered true positives. True positive results were obtained on any fraction of treatment and if IVD had only been completed on the first fraction, 84.4% of true positive results would have been missed. This was made possible due to the automation that saved over 800 h of manual intervention and stored data in an accessible database. Significance. An improved EPID calibration to allow off-axis measurement maximises the number of patients eligible for IVD (36.8% of patients in this study). We also demonstrate the importance in selecting context-specific assessment metrics and how these can lead to a managable false positive rate. We have shown that the use of fully automated IVD facilitates use on every fraction of treatment. This leads to identification of areas for treatment improvement for both individuals and across a patient cohort, expanding the uses of IVD from simply gross error detection towards treatment optimisation.

Development and validation of the low-cost pregnant female physical phantom for fetal dosimetry in MV photon radiotherapy.

Monte Carlo (MC) simulations or measurements in anthropomorphic phantoms are recommended for estimating fetal dose in pregnant patients in radiotherapy. Among the many existing phantoms, there is no commercially available physical phantom representing the entire pregnant woman. In this study, the development of a low-cost, physical pregnant female phantom was demonstrated using commercially available materials. This phantom is based on the previously published computational phantom. Three tissue substitution materials (soft tissue, lung and bone tissue substitution) were developed. To verify Tena's substitution tissue materials, their radiation properties were assessed and compared to ICRP and ICRU materials using MC simulations in MV radiotherapy beams. Validation of the physical phantom was performed by comparing fetal doses obtained by measurements in the phantom with fetal doses obtained by MC simulations in computational phantom, during an MV photon breast radiotherapy treatment. Materials used for building Tena phantom are matched to ICRU materials using physical density, radiation absorption properties and effective atomic number. MC simulations showed that percentage depth doses of Tena and ICRU material comply within 5% for soft and lung tissue, up to 25cm depth. In the bone tissue, the discrepancy is higher, but again within 5% up to the depth of 5cm. When the phantom was used for fetal dose measurements in MV photon breast radiotherapy, measured fetal doses complied with fetal doses calculated using MC simulation within 15%. Physical anthropomorphic phantom of pregnant patient can be manufactured using commercial materials and with low expenses. The files needed for 3D printing are now freely available. This enables further studies and comparison of numerical and physical experiments in diagnostic radiology or radiotherapy.

Evaluation of the effect of silicone implants in a breast radiotherapy treatment: A Monte Carlo approach

Since 2020, breast cancer is the most common among women, and in South America, Brazil presents the highest rates. After mastectomy and breast reconstruction, commonly silicone breast implants are used to replace the removed breast tissue, and radiation therapy is performed to reduce its recurrence in the remaining tissues and nearby lymph nodes. The Monte Carlo simulation using the MCNP6.2 code accompanied by a female virtual anthropomorphic phantom (FASH3) were utilized to simulate the radiation therapy scenario. These tools were used to determine the absorbed doses in the patient's organs and tissues, evaluating the effect of the breast silicone prosthesis on the dose distribution, applying a dose of 50.4 Gy in a LINAC Varian 2100c with a 6 MV beam. The eye lens and the gonads suffered the highest effects of scattered radiation by the silicone prosthesis, increasing the absorbed dose values by 2.10% and 1.51%, respectively, when compared to normal breast tissue.

PO-2250 SGRT for whole breast radiotherapy treatments: accuracy compared to conventional tattoo method

PO-2250 SGRT for whole breast radiotherapy treatments: accuracy compared to conventional tattoo method

Radiological Society of North America (RSNA) 3D Printing Special Interest Group (SIG) clinical situations for which 3D printing is considered an appropriate representation or extension of data contained in a medical imaging examination: breast conditions

The use of medical 3D printing has expanded dramatically for breast diseases. A writing group composed of the Radiological Society of North America (RSNA) Special Interest Group on 3D Printing (SIG) provides updated appropriateness criteria for breast 3D printing in various clinical scenarios. Evidence-based appropriateness criteria are provided for the following clinical scenarios: benign breast lesions and high-risk breast lesions, breast cancer, breast reconstruction, and breast radiation (treatment planning and radiation delivery).

Abstract P2-14-09: Sensory Evaluation of Nipple-Areolar Complex after Nipple-Sparing Mastectomy: A Comparison of Incision Approaches

Abstract Background: Since nipple-sparing mastectomy (NSM) has been widely practiced, majority of previous studies have evaluated the effects of Nipple-areolar complex (NAC) preservation on body image adjustment. However, few have evaluated NAC sensation after NSM in a large sample size. This study aims to assess NAC sensation after NSM and compare the results according to different incisional approaches; specifically, inframammary fold (IMF) and peri-areolar. Methods: Post NSM patients from Oct 2019 to Nov 2021 have been recruited prospectively. A total of 115 patients (IMF 69 and peri-areolar 36) were evaluated for NAC sensory at various time points during follow up within 1.5 to 4 years after surgery. NAC sensation was scored by pin-prick test in a scale of 0 to 2 (0: no sensation, 1: dull sensation, 2: sharp sensation), divided in 5 areas of the NAC and summed up to a total of 10. Results: In all patients, a median of the pin-prick test total score on NAC was 3 (0-10). Pin-prick test of NAC showed numerically higher NAC sensory score in the IMF incision than in the peri-areolar group without a statistical significance (IMF: Median 4 Mean 3.83 ± 3.04, Peri-areolar Median 2 Mean 2.69 ± 3.64, p=0.062). When sensory scores were evaluated depending on NAC zones (A: Nipple, B: Upper outer, C: Upper inner, D: Lower outer, E: Lower inner) the IMF incision group showed better outcomes in zone B (p=0.015) and E (p=0.043). Simple linear regression analysis showed the possibility of incisional approach, diabetes mellitus (DM) history, previous radiotherapy of ipsilateral breast, post mastectomy radiotherapy (PMRT), adjuvant chemotherapy, tumor to nipple distance and laterality influencing NAC sensory with p&amp;lt; 0.2. When these factors were taken to multiple linear regression analysis, DM history (p=0.045), previous radiotherapy (p=0.001), postop radiotherapy (p=0.001), and adjuvant chemotherapy (p=0.001). Conclusion: NAC sensory deteriorated postoperatively in general. Scores of NAC sensation were numerically higher in the patients with IMF incision, although the difference was not statistically significant. NAC sensation was negatively affected by DM history, previous ipsilateral breast radiotherapy and post-NSM treatments such as chemotherapy and PMRT. While incision type may improve aesthetic outcomes, additional efforts are necessary to ameliorate the post-NSM NAC desensitization. Table 1. Patient characteristics Table 2. Linear regression analysis for clinical factors affecting NAC sensory Citation Format: Yoonwon Kook, Ji Soo Jang, Seung Ho Baek, Soong June Bae, Sung Gwe Ahn, Joon Jeong. Sensory Evaluation of Nipple-Areolar Complex after Nipple-Sparing Mastectomy: A Comparison of Incision Approaches [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-14-09.

Radiation-Associated Cardiotoxicity during Breast Cancer Treatment with Ionizing Radiation

Introduction: Breast cancer is the most common cancer in women. The treatment of breast carcinoma has advanced in the last decade and nowadays there are treatment protocols for all stages of the disease. Depending on the histopathology and stage breast cancer is treated with surgery, chemotherapy and radiotherapy. Regarding radiation, the field of irradiation includes the chest wall in patients with mastectomy, or the breast glandular tissue in patients with conserving surgical approaches. It is often treated with radiation therapy with two opposing tangential fields, and when indicated supraclavicular lymph nodes have to be irradiated. In this case an additional anterior field is applied. The tangential as well as the other radiation beams have a potential damaging effect on the healthy surrounding tissues, particularly over the heart in the left breast irradiation and in the lungs as well. Material and Methods: The study included 25 patients with left breast carcinoma, all post surgery, treated with radiation therapy, with the Elekta accelerator at our department. For academic purpose the treatment plans were generated following two methods. The first one with two tangential opposite beams plus a supraclavicular beam. In this method the angles of the tangential internal and external create an angle that is equal to 180&#730 {310&#730& 130&#730}; no further changes were made to the beam geometry. Even though this is not the best option from the dose distribution point of view, it is still the most applied method, probably because of the semplicity of it. For each patient, a second plan was generated using two opposite tangential beams plus the supraclavicular beam. The angles of the internal and external beam were changed from 1&#730to 3&#730, depending on the surface of the body, so that the resulting angle was 180&#730± 3&#730 {310&#730± 3&#730& 130&#730± 3&#730} with the aim to adapt the beam geometry as much as possible to the shape of the thoracic wall and to spare the OAR-s. Results and Discussion: The data show that the dose in the organs at risk, in terms of dose percentage, is lower when the angles of the beams are changed with 1&#730-3&#730, compared to the classic method where the internal and external angles equal 180&#730. This dose is not only non-negligible but significant; for every angle change from 1&#730to 3&#730, there is a significant reduction in the integral dose in the radiated volume, expressed in percentage, up to 5%. Conclusion: In most centers, the radiation treatment of breast is realized with two tangential opposite beams, which usually are mirror beams, or in other words, the internal and external beam angles create an angle of 180&#730 {α + β = 180&#730}. This is a simple method, which provides a good dose distribution, but leaves a relatively high dose in the organs at risk. This study shows the difference in the dose percentage in the heart and lung when the beam angles are changed adapting to the anatomy of the patient. Reducing these doses allows for better overall treatment and less longtime toxicity, particularly for the heart tissues.

Breast Cancer Radiotherapy Experience in a Newly Established Cancer Center in Nigeria

<h3>Purpose/Objective(s)</h3> The purpose of this project is to document the experience of breast cancer radiation therapy for a newly established cancer center in Nigeria. The documented experiences will provide insights to radiation oncology practice in this low- and middle-income country setting as a reference in global oncology <h3>Materials/Methods</h3> IRB approved analysis of data from 83 breast cancer patients was conducted to determine patient characteristics and dosimetric parameters including average, median, maximum and minimum radiotherapy doses to different organs-at-risk (OARs) for the patients treated. The mean thyroid dose, lung V20Gy, and heart V5Gy were selected as critical points of interest as literature suggests these values to be good predictors of various complications including hypothyroidism, lung perfusion and pneumonitis, and increased cardiac mortality risk, respectively. <h3>Results</h3> The mean and median ages of patients presenting at the cancer center with breast cancer for radiotherapy was about 50 years and 49 years, respectively. This is significantly less than the median age for whites (63 years) and Blacks (56 years) presenting in the United States. About 1 out of 4 patients assessed was HER2 positive, and nearly 80% of patients had positive lymph node status. Meanwhile, average prescription dose to the treated breast was 41.8 Gy. The mean dose to the thyroid among the treated patients was 22.1 Gy, on the lower end of predictive doses regarding risks of hypothyroidism development (V10Gy-V80Gy). The average lung V20Gy in this cohort was 18.9% the total ipsilateral lung volume. On average, the mean dose to the contralateral breast was 2.7 Gy. <h3>Conclusion</h3> Breast cancer patients in Nigeria often present relatively younger and with advanced disease requiring surgery and radiotherapy. The current breast radiotherapy treatment practice in this new cancer center provides a solid foundation for quality treatment delivery. The ongoing analysis in this project provides a foundation for more research to assess long term toxicity and treatment response or survival and areas for continuous improvement and complementary or integrative interventions.

Machine Learning to Predict the Quality of a Left-Sided Whole Breast Radiotherapy Treatment Plan

<h3>Purpose/Objective(s)</h3> Develop a Support Vector Machine (SVM) model that uses dosimetric data to predict the quality of a breast radiotherapy treatment plan. <h3>Materials/Methods</h3> One hundred twenty left-sided breast cancer patients from a single institute were included in the study. They were treated with 15-fractions whole breast radiotherapy up to 40.05 Gy with a concomitant boost to deliver 48 Gy to the tumor bed. There was no treatment of lymph nodes. Dose was delivered with a fixed-beam treatment mode and delivered plans were manually created. For each patient, a second treatment plan was generated, using an in-house system for automated plan generation. The treating clinician evaluated the two available plans for each patient and assigned a sentence regarding the quality of the plan in the format of yes/no variable (well optimized plan i.e., "yes" or plan that can be further optimized i.e., "no"). A quantitative scoring tool (ST) already used by Orecchia et al was used to assign 0, 0.5 or 1 points for each involved OAR and PTVs depending on both the fulfilment of multiple DVH constraints and on achieved coverage level for PTVs. Four SVM models were trained using 216 plans (arbitrarily selected from the available 240) using: i) dose volume parameters for target and OARs of each plan, ii) ST and iii) the clinician's plan sentence. Training was performed through iterative optimization using ten Cross-validation folds with four models: a) Model 1 with the ST only, b) Model 2 with the difference between dose volume parameters and the DVH constraints, c) Model 3 with both information from models 1 and 2 and d) Model 4 with ST and dose volume parameter. All models had clinician's sentence as response variable. Finally, the 24/240 patients not used for training were used for final validation. Models' performances were assessed through confusion matrix parameters and multiclass ROC analyses on the training and independent validation set. <h3>Results</h3> The involved clinician refereed as "yes" 92 plans (77%) out of 120 and "no" the remaining 28 in the manual set; 79 plans (66%) were judged "yes" and 41 "no" in the automatic set. Results in terms of Accuracy (ACC), Positive Predicted Values (PPV), True Positive Rates (TPR) and Area under Curve (AUC) for the four models are presented in table 1. <h3>Conclusion</h3> Clinicians' judgements are crucial in daily plan evaluations. We have proposed supervised learning to predict if a plan will be considered by clinician well optimized or not. Results are encouraging and the tool could potentially become useful for aiding treatment planners and reducing clinicians' workload.

Association of Dosimetric Parameters and Boost Volume with Quantitative Cosmetic Outcomes in a Randomized Trial of Conventionally Fractionated vs. Hypofractionated Whole Breast Irradiation

<h3>Purpose/Objective(s)</h3> Whole breast irradiation (WBI) is the most common treatment in radiation oncology, yet there is a relative paucity of evidence delineating the relationship between dosimetric parameters and long-term outcomes. We conducted a prospective randomized trial with longitudinal follow up to compare two different WBI dosing schedules and sought to evaluate the association of dosimetric parameters and boost volume with long term cosmetic outcomes using novel, previously validated, quantitative metrics of breast cosmesis derived from 2-dimensional photographs. <h3>Materials/Methods</h3> A prospective randomized trial of patients with early breast cancer who were randomly assigned to conventionally fractionated or hypofractionated WBI plus boost was conducted from 2011-14. Anteroposterior photographs from the low-neck to umbilicus were obtained at baseline, 6 months, and yearly through 5 years. Fiducial points marking each nipple and inframammary fold were delineated on each photograph and used to calculate a measure of nipple symmetry (M1) and breast vertical symmetry (M2), as previously described (PMID 28333010). These values range from 0 to 1 with values closer to 1 indicating better symmetry. Multivariable logistic regression longitudinal models with M1 and M2 as outcomes, dichotomized at the median, evaluated associations of dosimetric parameters and boost volume with M1 and M2 adjusting for relevant clinical, demographic and treatment variables. Candidate dosimetric variables included volume of tissue encompassed by the 90% isodose line (PTV), tumor bed volume, volume encompassed by the 105% isodose line, maximum point dose in the breast (Dmax), central axis separation, percent dose delivered with 18 MV photons, boost energy, boost position, boost modality, and cross-sectional area of the boost field. <h3>Results</h3> Of the 287 patients included in this trial, 149 patients received CF-WBI and 138 received HF-WBI, with median follow up 48 months. Median age was 60 years. Median PTV was 1340cc (IQR 904-1760), median tumor bed volume was 23cc (IQR 13-43), and median boost field size was 64cm² (IQR 54-80). 50% of patients had a Dmax of ≥107% of the prescription dose. A total of 1600 photographs were annotated to calculate M1 and M2. In multivariable analysis, highest quartile of PTV (OR 0.40, P=0.002) and boost field size (OR 0.50, P=0.02) were associated with worse M1 outcome compared to the lowest quartile. Highest quartile of tumor bed volume was associated with worse M2 compared to the lowest quartile (OR 0.52, P=0.03). <h3>Conclusion</h3> Utilizing previously validated quantitative measures of cosmetic outcome derived from 2D photographs, we found that boost fields with cross-sectional area <54 cm² and PTV <1760cc were associated with better nipple symmetry, and tumor bed volume >43cc was associated with worse vertical breast symmetry. Understanding how dosimetric parameters and boost volume affect long-term cosmetic outcomes can facilitate optimization of breast radiation treatment plans.

Adjuvant Stereotactic Body Radiation Therapy (ASBRT) for Early-Stage Breast Cancer: Symptomatic Fat Necrosis is Associated with Consecutive Daily Treatments

<h3>Purpose/Objective(s)</h3> Outcomes following accelerated partial breast irradiation in select women with early-stage breast cancer are comparable to whole breast irradiation. ASBRT is an attractive treatment option, but mature toxicity outcomes are limited. Toxicity risk with SBRT has been associated with a consecutive daily schedule in other organs. In the present study, we explore the association of treatment schedule and fat necrosis. <h3>Materials/Methods</h3> Early-stage breast cancer patients (Stage 0 and I) were treated per an institutional protocol. A minimum of 4 gold fiducials were implanted around the lumpectomy cavity for target delineation and tracking. The clinical treatment volume (CTV) was defined as lumpectomy cavity with a uniform 0-10 mm expansion confined to breast tissue. The planning treatment volume (PTV), defined as the CTV with a 0-2 mm uniform expansion, was prescribed 30 Gy in 5 fractions. Breast examination and mammography were completed per routine institutional practice. A patient was deemed to have fat necrosis when breast examination identified a tumor bed mass with distinctive mammographic characteristics. <h3>Results</h3> Twenty women were treated over a 7-year period extending from September 2008 to September 2015 and followed for a minimum of 6 years. The median CTV expansion was 5 mm (range, 0-10), median PTV was 62.5 cm³ (range 15-142), median PTV/breast volume ratio was 8.3% (range 4.1-25.6), median prescription isodose line was 83% (range 75-87) and median treatment duration was 7 days (range 5-13). Seven patients were treated on 5 consecutive days (i.e., Monday through Friday). At a median follow up of 8 years (range, 6-12 years), 5 women developed fat necrosis. All 4 symptomatic patients had been treated on consecutive days and the symptomatic fat necrosis was diagnosed at a median follow-up of 5.9 years (range, 4.8-7.4). Cox regression analysis identified consecutive daily treatments as a predictor of symptomatic fat necrosis (OR: 26.8, <i>p value</i>=0.05). <h3>Conclusion</h3> Our mature findings demonstrate an association between Monday through Friday treatment and symptomatic fat necrosis. Fortunately, our research also suggests that symptomatic fat necrosis is curtailed by merely extending the treatment duration beyond 5 days. Accordingly, we believe that the Fast-Forward trial investigators should reevaluate their current assertion that 26 Gy whole breast irradiation delivered in 5 consecutive daily fractions over 5 or 7 days is a new standard treatment option. Only the yet to be completed 10-year analysis of this large prospective study will ultimately determine if delivering 5 large consecutive daily adjuvant breast radiation treatments is associated with symptomatic fat necrosis and if adding 2 additional days to the treatment course effectively curtails this adverse side-effect.

Mepitel Film for the prevention of acute radiation dermatitis in breast cancer: A randomized multi-centre open-label phase 3 trial

390226 Background: Radiation dermatitis (RD) is common in patients undergoing breast radiation treatment (RT), with worse RD in patients with large breasts and after mastectomy. Mepitel Film (MF), a silicone-based polyurethane film with Safetac technology, may reduce RD. We hypothesized that MF might play a role in preventing RD in this group of patients at risk. Methods: Patients were randomly assigned to receive MF or standard skin care (2:1 ratio). Patients with large breasts after lumpectomy (bra size ≥ 36 inches or cup size ≥ C) or after mastectomy were eligible. Stratification factors included surgery type (lumpectomy vs. mastectomy), dose fractionation (conventional vs. hypofractionated), and administration of boost/bolus. The primary endpoint was grade (G) 2 or 3 RD using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 during RT and within 3 months of completion of RT. Secondary endpoints included CTCAE G3, incidence of moist desquamation, use of topical antibiotic cream, and patient- (PROs) and clinician- (CRO) reported outcomes using the modified Radiation-Induced Skin Reaction Assessment Scale (RISRAS) and Skin Symptom Assessment (SSA). This study is registered with ClinicalTrials.gov (NCT04166799). Results: Between January 2020 and May 2022, 266 patients (66%) were randomly assigned to MF and 137 (34%) to standard care. After removing withdrawn patients, 376 patients were included in the modified intention-to-treat analysis. The incidence of G2 or 3 RD was significantly lower in MF patients compared to standard care (n = 39/251, 15.5%; 95% CI, 11.3-20.6% vs. n = 57/125, 45.6%; 95% CI, 36.7-54.8% respectively, odds ratio [OR]: 0.20, P &lt; .0001). Benefits of MF over standard care remained significant in patients who developed G3 RD (n = 7, 2.8%; 95% CI, 1.1-5.7% vs. n = 17, 13.6%; 95% CI, 8.1-20.9%, OR: 0.19) and moist desquamation (n = 20, 8.0%; 95% CI, 4.9-12.0% vs. n = 24, 19.2%; 95% CI, 12.7-27.1%, OR: 0.36). When evaluating the combined patient and health care professional score using the RISRAS, the MF arm had significantly lower scores than standard care ( P &lt; .0001); individual items on the RISRAS also favored MF for PROs (tenderness, discomfort of pain and burning sensation) and CROs (erythema and moist desquamation). Similarly, when assessed by the SSA, blistering/peeling, erythema, pigmentation, and edema in PROs, and pain/soreness, blistering/peeling, erythema, and pigmentation in CROs were significantly reduced in MF. Topical antibiotics were prescribed significantly less frequently in MF (23.1% vs. 43.2%, P &lt; .0001). Three patients removed the film prematurely due to development of an allergic rash (n = 2) and excessive pruritis (n = 1). Conclusions: MF significantly reduces RD in breast cancer patients undergoing RT when compared to the standard care. We recommend changes to the clinical practice for RD prevention and inclusion of MF in high-risk patients in future guideline recommendations. Clinical trial information: NCT04166799.

Performance comparison of quantitative metrics for analysis of in vivo Cherenkov imaging incident detection during radiotherapy.

Examine the responses of multiple image similarity metrics to detect patient positioning errors in radiotherapy observed through Cherenkov imaging, which may be used to optimize automated incident detection. An anthropomorphic phantom mimicking patient vasculature, a biological marker seen in Cherenkov images, was simulated for a breast radiotherapy treatment. The phantom was systematically shifted in each translational direction, and Cherenkov images were captured during treatment delivery at each step. The responses of mutual information (MI) and the γ passing rate (%GP) were compared to that of existing field-shape matching image metrics, the Dice coefficient, and mean distance to conformity (MDC). Patient images containing other incidents were analyzed to verify the best detection algorithm for different incident types. Positional shifts in all directions were registered by both MI and %GP, degrading monotonically as the shifts increased. Shifts in intensity, which may result from erythema or bolus-tissue air gaps, were detected most by %GP. However, neither metric detected beam-shape misalignment, such as that caused by dose to unintended areas, as well as currently employed metrics (Dice and MDC). This study indicates that different radiotherapy incidents may be detected by comparing both inter- and intrafractional Cherenkov images with a corresponding image similarity metric, varying with the type of incident. Future work will involve determining appropriate thresholds per metric for automatic flagging. Classifying different algorithms for the detection of various radiotherapy incidents allows for the development of an automatic flagging system, eliminating the burden of manual review of Cherenkov images.

Ultrahypofractionated breast radiotherapy during SARS-CoV-2 virus pandemic, beyond fast-forward trial: a local experience

Abstract Background: During the SARS-CoV-2 virus pandemic, University Hospital Birmingham NHS Trust Oncology Department incorporated the ultrahypofractionated regime of 26Gy/5 fractions alongside the moderate hypofractionated regime of 40Gy/15 fractions as part of local adjuvant breast radiotherapy treatment (RT) for eligible patients. We conducted a local study to assess the real-life experience of patients undergoing ultrahypofractionated schedule to compare feasibility and toxicity to the fast-forward trial during the COVID − 19 pandemic. Methods: A single institution, retrospective, qualitative study. Patients included had early-stage breast cancer and received adjuvant radiotherapy between 23 March 2020 and 31 May 2020, a total of 211 patients. Inclusion was irrespective of any other neoadjuvant/adjuvant treatments. Data were collected retrospectively for treatment dose, boost dose and toxicity. Results: Of the total 211 patients, 85 were treated with 26Gy in 5# and 19 patients received a boost as per the fast-forward protocol. Of these 85 patients, 15·9% did not report any skin toxicity post-treatment. 63·5% of patients reported RTOG Grade 1, 15·9% had RTOG Grade 2, and 1·6% reported RTOG Grade 3 skin toxicity. 3·2% of the patients could not be contacted for follow-up. Of the 19 patients who received a breast boost, 10·53% reported no skin changes. 78·9% reported Grade 1 skin toxicity. Both Grades 2a and 2b skin toxicity were reported by 5·26% each. The patient demographics and tumour characteristics in our study cohort were comparable to those within the fast-forward trial. In terms of post-RT skin toxicity, fewer patients reported any toxicity in the UHB patient cohort versus those in the trial, and the number of Grade 2/3 toxicities reported was also low. A delay in toxicity reporting from 2 weeks for 40Gy/15 to 3 weeks for 26Gy/5 was observed. Conclusion: Our study concluded that offering ultrahypofractionation was convenient for patients; reducing the number of hospital visits during the SARS-CoV-2 virus pandemic appeared safe in terms of acute post-RT-related skin toxicity. The reduced hospital visits limited exposure of patients and staff to the SARS-CoV-2 virus while also ensuring efficient use of Radiotherapy Department resources. Local follow-up protocols have been amended to ensure review at 3 weeks for the 26Gy/5 schedule to acknowledge the delay in acute toxicity development. To date, there is only 5-year toxicity and relapse data available from the fast-forward trial; therefore, hypofractionation schedules should be offered to patients as long as they fulfil the criteria and understand the limitations of the study as well as accelerated peer review processes in the face of the pandemic.

P116 - On the use of OSLDs for in-vivo measurements of surface dose in breast radiotherapy treatments

P116 - On the use of OSLDs for in-vivo measurements of surface dose in breast radiotherapy treatments

Pre-pectoral breast reconstruction: early and long-term safety evaluation of 146 unselected cases of the early pre-pectoral era of a single-institution, including cases with previous breast irradiation and post-mastectomy radiation therapy.

We re-evaluated acute and early-late toxicity-related factors among pre-pectoral immediate tissue expander/implant (TE/I) breast reconstruction (BR) unselected, first-era, cases, including previous breast radiation treatment and post-mastectomy radiation therapy (PMRT). A retrospective analysis of 146 (117 therapeutic and 29 prophylactic) pre-pectoral reconstructions, between 2012 and 2016, considered patient-related (age, body mass index [BMI], smoke-history, comorbidity, BRCA mutation), and treatment-related characteristics (previous irradiation, axillary surgery, PMRT, pre- and postoperative chemotherapy, endocrine therapy, and target-therapy). Safety was evaluated as acute and early-late complications, and TE/I failures. At multivariate analysis of the 146 cases (117 patients submitted to BR) a significant factor related to acute toxicity was: BMI ≥ 25 (31.3% [≥ 25] vs 8.8% [< 25]; OR 4.44, 95% CI 1.56-12.6; p = 0.003), while previous breast surgery on ipsilateral side presented a borderline significance (31.6% [previous surgery] vs 7.4% [no previous surgery]; OR 3.74, 95% CI 0.97-14.40; p = 0.055). Factors significantly related to TE/I failure were: current or previous smoking exposition (13.8% [smokers] vs 2.6% [non-smokers]; OR 7.32, 95% CI 1.37-39.08; p = 0.02) and preoperative chemotherapy (18.8% [yes] vs 3.5% [no]; OR 8.16, 95% CI 1.29-51.63; p = 0.026). At 4-year median follow-up, 3 deaths, 5 locoregional recurrences, and 14 distant metastases occurred. Immediate pre-pectoral BR is safe and effective, with low rates of acute and early-late complications. BMI and previous breast surgery were related to higher complications but not failure; smoking and preoperative chemotherapy were related to TE/I explant. Previous RT and PMRT were related neither to early-late toxicity nor failure.