Harnessing the cGAS-STING pathway to potentiate radiation therapy: current approaches and future directions

In this review, we cover the current understanding of how radiation therapy, which uses ionizing radiation to kill cancer cells, mediates an anti-tumor immune response through the cGAS-STING pathway, and how STING agonists might potentiate this. We examine how cGAS-STING signaling mediates the release of inflammatory cytokines in response to nuclear and mitochondrial DNA entering the cytoplasm. The significance of this in the context of cancer is explored, such as in response to cell-damaging therapies and genomic instability. The contribution of the immune and non-immune cells in the tumor microenvironment is considered. This review also discusses the burgeoning understanding of STING signaling that is independent of inflammatory cytokine release and the various mechanisms by which cancer cells can evade STING signaling. We review the available data on how ionizing radiation stimulates cGAS-STING signaling as well as how STING agonists may potentiate the anti-tumor immune response induced by ionizing radiation. There is also discussion of how novel radiation modalities may affect cGAS-STING signaling. We conclude with a discussion of ongoing and planned clinical trials combining radiation therapy with STING agonists, and provide insights to consider when planning future clinical trials combining these treatments.

Partial Breast Irradiation for Patients With Early-Stage Invasive Breast Cancer or Ductal Carcinoma In Situ: An ASTRO Clinical Practice Guideline

PURPOSE

This guideline provides evidence-based recommendations on appropriate indications and techniques for partial breast irradiation (PBI) for patients with early-stage invasive breast cancer and ductal carcinoma in situ.

METHODS

ASTRO convened a task force to address 4 key questions focused on the appropriate indications and techniques for PBI as an alternative to whole breast irradiation (WBI) to result in similar rates of ipsilateral breast recurrence (IBR) and toxicity outcomes. Also addressed were aspects related to the technical delivery of PBI, including dose-fractionation regimens, target volumes, and treatment parameters for different PBI techniques. The guideline is based on a systematic review provided by the Agency for Healthcare Research and Quality. Recommendations were created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength.

RESULTS

PBI delivered using 3-dimensional conformal radiation therapy, intensity modulated radiation therapy, multicatheter brachytherapy, and single-entry brachytherapy results in similar IBR as WBI with long-term follow-up. Some patient characteristics and tumor features were underrepresented in the randomized controlled trials, making it difficult to fully define IBR risks for patients with these features. Appropriate dose-fractionation regimens, target volume delineation, and treatment planning parameters for delivery of PBI are outlined. Intraoperative radiation therapy alone is associated with a higher IBR rate compared with WBI. A daily or every-other-day external beam PBI regimen is preferred over twice-daily regimens due to late toxicity concerns.

CONCLUSIONS

Based on published data, the ASTRO task force has proposed recommendations to inform best clinical practices on the use of PBI.

Phase I-II Study of Prone Hypofractionated Accelerated Breast and Nodal Intensity Modulated Radiation Therapy

PURPOSE/OBJECTIVE(S)

In patients (pts) with breast cancer, prone radiation therapy (RT) has been shown to reduce heart and lung dose which may decrease late toxicity. Routinely used for whole breast irradiation, its use to treat regional lymph nodes (LNs) is not widespread.

MATERIALS/METHODS

In this phase I-II study, pts treated with partial mastectomy or mastectomy with 1-5 pathologically involved LNs underwent whole breast or post-mastectomy RT plus regional nodal irradiation using IMRT to the supraclavicular and level III axillary LNs. Pts who underwent sentinel LN biopsy (SLNB) alone (no axillary dissection) had the level I and II axillary LNs included in the RT field. 40.5Gy in 15 daily 2.7Gy fractions with daily concomitant 0.5Gy tumor bed boost was prescribed. Normal tissue dose constraints included heart V5Gy<5%, ipsilateral lung V10Gy<20%, contralateral lung V5Gy<15%, ipsilateral brachial plexus (BP) maximal dose (Dmax)<43Gy, spinal cord Dmax≤37.5Gy, spinal cord + 0.5cm Dmax<41Gy, thyroid contralateral lobe Dmax<16Gy, esophagus V30Gy<50% and Dmax≤40.5Gy. The primary endpoints were dosimetric feasibility and incidence of >grade 2 acute toxicity according to CTCAE, v3.0. The secondary endpoint was late toxicity. Exploratory outcomes were local recurrence, disease free survival (DFS), and overall survival (OS).

RESULTS

Between January 2011 to December 2016, 97 pts with stage IB-IIA breast cancer were enrolled. 66 pts underwent partial mastectomy and 31 pts underwent mastectomy. 16 pts had SLNB alone. 33% (95% CI: 23.8%, 43.3%) met all protocol dose constraints. Heart, contralateral lung, spinal cord and esophagus V30Gy constraints were met by all pts. The ipsilateral lung constraint was met in 95% (95% CI: 88.6%, 98.4%) of plans with a mean V10Gy of 9.44% (SD: 6.08). The BP Dmax constraint was exceeded in 31.6% (95% CI: 22.4%, 41.9%) of plans with a mean increase of 2.86 Gy (SD: 7.92 Gy) over target. The esophageal Dmax<40.5Gy constraint was exceeded in 6 plans with an increase in 0.74 Gy (SD: 0.46 Gy) over target. There were no grade 3 acute toxicities meeting the primary toxicity endpoint. Common acute low-grade toxicities by pt included fatigue (grade 1: 54 [56%]; grade 2: 2 [2%]), esophagitis (grade 1: 8 [8%]; grade 2: 2 [2%]), dermatitis (grade 1: 81 [84%]; grade 2: 6 [6%]). At median and maximum follow up of 8.02 (IQR: 3.31) and 13.3 years, respectively, there were 2 local recurrences (2.1%). DFS and OS were 86.6% (95% CI: 78.2%, 92.7%) and 90.7% (95% CI: 83.1%, 95.7%), respectively. The incidence of pts with maximum grade 1, 2 and 3 late toxicities were 39 (40%), 14 (14%), and 2 (2%), respectively. The maximum grade late toxicities included 1 grade 3 retraction and 2 grade 3 asymmetries. There was no brachial plexopathy or pneumonitis.

CONCLUSION

Patients treated with prone hypofractionated hybrid breast/chest wall tangents and IMRT to the regional LNs demonstrate excellent dosimetry to the heart, lungs and spinal cord, minimal acute and late toxicity and excellent clinical outcomes. PMID: 26723552.

A Radiation Therapy Contouring Atlas for Delineation of the Level I-II Axilla in the Prone Position

PURPOSE/OBJECTIVE(S)

When patients are treated prone for whole breast irradiation (WBI), the axilla typically receives less dose than when patients are treated with WBI in the supine position. There are situations, however, where the axilla is a target as in a situation where the physician intends to treat with "high tangents" to provide good coverage of both the breast and level I-II axilla. In these scenarios, ideal target delineation when the patient is in the prone position is not well-defined. While different consensus guidelines exist for delineation of the nodal areas in the supine position, to our knowledge there are no contouring guidelines for the regional nodes in the prone position based on bone, skin, vascular and muscle landmarks.

MATERIALS/METHODS

Forty-three patients treated with high tangents in the prone position from 2012-2018 were identified as representative cases. The level I and II regional nodal contours from the Radiation Therapy Oncology Group (RTOG) breast cancer atlas were adapted for prone position by a radiation oncologist and a breast radiologist based on anatomic considerations and changes observed from supine to prone positioning on diagnostic imaging. The revised nodal contours were reviewed by an expanded expert multidisciplinary panel including additional breast radiation oncologists and surgical oncologists to delineate the level I and II axilla on noncontrast computed tomography (CT) scans.

RESULTS

We adapted the RTOG breast cancer atlas, supported by detailed figures, in order to create a CT based atlas of the level I and II axillary lymph node stations in the prone position. For the level I axilla, the cranial and caudal anatomic boundaries remain unchanged. With transition to the prone position from supine, tenting of the pectoralis major occurs displacing the muscle from the chest wall and shifting the axillary space anteromedial to the lateral border of the pectoralis major. Therefore, the anterior boundary is now defined by the plane of the anterior extent of the pectoralis major to skin. The medial boundary is defined by the plane of the lateral border of the pectoralis major and pectoralis minor including to ribs and intercostal muscles. The lateral boundary is defined by the skin, cropped by 5mm. The posterior boundary is defined by the plane of the anterior surface of the latissimus dorsi and subscapularis muscle to skin. For the level II axilla, the cranial, posterior, medial and lateral boundaries remain unchanged. With transition from supine to prone, the axilla exhibits an anterolateral shift, now laterally abutting the lateral border of the pectoralis minor. The anterior boundary is now defined as the posterior aspect of the pectoralis major muscle. The caudal boundary is where the pectoralis minor inserts into ribs.

CONCLUSION

The adaptations to the RTOG breast cancer atlas for prone positioning will enable radiation oncologists to more accurately target the level I and II axilla when treating patients prone in whom the axilla is a target in addition to the breast.

Effectiveness and Toxicity of Five Fraction Prone Accelerated Partial Breast Irradiation

PURPOSE/OBJECTIVE(S)

Accelerated partial breast irradiation (APBI) after breast conserving therapy (BCT) is increasingly used to treat women with early stage breast cancer. Our institution was an early adopter of 5-fraction ABPI and delivers APBI primarily to patients in the prone position. This study reports long term oncologic and cosmetic outcome in a large cohort of women treated with 5-fraction external beam APBI.

MATERIALS/METHODS

We included patients receiving APBI 600 cGy × 5 fx delivered every other day or every day between 2010 and 2022. Late toxicities and clinician and patient rated cosmesis were evaluated for patients with > 6 month follow up. Univariate and multivariate logistic regression models were used to identify clinical and dosimetric factors associated with development of acute and late toxicities, clinician and patient rated cosmesis. All statistical tests were two-sided, and the null hypothesis was rejected for p<0.05. Kaplan Meier methodology was used to calculate overall survival (OS), disease-free survival (DFS) and locoregional recurrence-free survival (LR-RFS).

RESULTS

Four hundred and forty-two patients received APBI either daily (56%) or every other day (44%). Most of the patients (92%) were treated in the prone position. Average mean heart dose was 23 cGy for left-sided and 11 cGy for right-sided breast cancers. Ipsilateral lung V30% ≤ 30%. At a median follow up of 48 months (range: 5.96 - 155 months), 12 (2.7%) patients developed a local recurrence, 14 (3.2%) patients developed a contralateral breast primary, 10 patients (2.3%) developed a distant metastasis and one patient (0.2%) developed a local recurrence followed by a distant metastasis 1 month later. Out of 258 patients with > 6 month follow up, rates of late grade 1-2 telangiectasia, fibrosis, edema, atrophy and hyperpigmentation were 4%, 18%, 1%, 19% and 7% respectively. There was only one late grade 3 event in a patient who developed significant breast atrophy. The rate of good-excellent physician and patient rated cosmesis was 95% and 89% respectively (N = 256 at median follow up of 80 months). On multivariate logistic regression, patients who did not receive any adjuvant endocrine or chemotherapy were at increased risk of developing a local recurrence. Patients with PR negative disease were at increased risk of distant metastasis. Patient who experienced any grade of acute dermatitis during treatment were at increased risk of any high grade (grade ≥ 2) late adverse event and worse physician rated cosmesis. Daily or every other day treatment did not correlate with worse toxicity or clinical outcomes. Plastic surgery involvement, LVI, EIC, lobular histology, and ER negativity did not correlate with an increased risk of recurrence. Five-year LR-RFS, DFS and OS were 98%, 92.5% and 98.6% respectively.

CONCLUSION

Five- fraction APBI delivered primarily in the prone position either daily or every other day was effective with low rates of local recurrence, minimal toxicity and excellent cosmetic scores at long term follow up.

Curietherapy User eXperience Pilot Study: A Novel Augmented Reality Educational Tool during Radiation Oncology Consultation for Patients with Breast Cancer

PURPOSE/OBJECTIVE(S)

Improved communication and knowledge delivery by clinicians at initial consultation may reduce anxiety and psychological burdens associated with cancer treatment. Based on our pilot qualitative study which involved semi-structured interviews of breast cancer patients, we developed Curietherapy User eXperience (CurieUx), an educational tool integrating augmented reality display technology into radiation oncology consultations.

MATERIALS/METHODS

We developed an interactive 3-dimensional hologram using a frictionless, augmented reality desktop display. Animated modules on patient-specific anatomy (breast, regional lymph nodes, organs-at-risk), linear accelerator, and positioning (prone and breath holding techniques) were created. Patients with newly diagnosed localized breast cancer undergoing radiation oncology treatment were prospectively enrolled in this IRB approved study to evaluate the impact of integrating augmented reality educational tools during radiation therapy consultation (n = 40). Likert scale surveys on anxiety (NIH PROMIS), radiation knowledge, and augmented reality experience (modified IBM technology usability survey) were administered to patients before and after radiation consultation.

RESULTS

A total of 40 newly diagnosed breast cancer patients were enrolled in this study with a median age of 67 years. Majority were diagnosed with T1-T2N0 (75.0%), followed by Tis (17.5%) and N1+ (7.5%). Of the 36 patients who proceeded with radiation, prone technique was utilized in 83.3% and deep inspiratory breath holding technique in 16.7%. Patients reported decreases in multiple components of anxiety after consultation with the CurieUx platform, including in fearfulness (2.13 vs 1.78, p = 0.003), uneasiness (2.28 vs. 1.82, p = 0.008), nervousness (2.41 vs 2.06, p = 0.005), and tenseness (2.28 vs 1.87, p = 0.004). Patients reported significant increases in radiation knowledge across multiple domains, including treatment machine (2.35 vs 4.7, p<0.001), radiation (2.7 vs 4.58, p<0.001), positioning (2.49 vs 4.68, p<0.001), and confidence (2.4 vs 4.3, p<0.001). An overwhelming majority of patients had positive experiences (4 or 5 on Likert scale) with using the CurieUx hologram display as part of consultation, including its ease of understanding (97%), clarity (93%), comfort (100%), value (97%), and satisfaction (97%).

CONCLUSION

Curietherapy User eXperience is a valuable educational tool that reduces patient anxiety and promotes radiation knowledge. CurieUx is easily incorporated into the existing radiation oncology consultation practice with the vast majority of patients believing it to be a valuable addition to the consultation process.

Clinical Outcomes and Setup Reproducibility in Patients Receiving Synchronous Bilateral Breast Radiation in the Prone Position

PURPOSE/OBJECTIVE(S)

Standardized radiation therapy (RT) positioning and planning are vital to treat both breasts without excess toxicity in patients with synchronous bilateral breast cancer (SBBC). We studied clinical outcomes and setup reproducibility in patients with SBBC treated in the prone position.

MATERIALS/METHODS

This is a retrospective study of patients receiving RT for SBBC from 2012-2022 treated in the prone position. Patient demographics, RT dose and field, toxicity, and outcomes were collected. RT planning used gantry and table shifts to avoid entrance/exit through contralateral breast and organs at risk. RT delivery was standardized, with left breast treated first. After 2014, radiographic films were placed during the first 5 fractions to evaluate field overlap. Consistent overlap required re-simulation or re-planning. Positional shifts during setup were collected for patients receiving bilateral whole breast irradiation (WBI) and bilateral partial breast irradiation (PBI).

RESULTS

A total of 45 patients were treated for SBBC. Median age was 67 years. Median follow-up was 28 months. 35 patients were treated with WBI (1 with low axilla on one side) and 5 with PBI. 5 patients were treated with WBI in one breast and PBI in the other. The most common whole breast dose was 40.5Gy, with a simultaneous integrated boost to the lumpectomy cavity to 48Gy. PBI patients were treated with 30Gy (n = 4) or 40.05Gy (n = 1). 8 patients (17.7%) had acute grade 2 and 1 patient (2%) had acute grade 3 dermatitis. This patient was treated WBI bilaterally and was known to have overlap on GaF. Physician and patient accepted higher toxicity for adequate coverage of bilateral upper inner quadrant tumors. Patients with grade > = 2 dermatitis had bilateral WBI (+/- low axilla) except 1. 6 patients had acute dermatitis in the sternal area (5 were WBI and 1 PBI). Only 2 of these patients had overlap on GaF. Of 20 patients with late toxicity follow-up (> 6 months), 5 (25%) had late grade 1-2 dermatitis. 4 (20%) were treated with WBI (+/-low axilla). 1 patient had both a local and distant recurrence. For setup and treatment delivery, couch shifts recorded for patients treated with bilateral WBI (n = 33) and bilateral PBI (n = 5) were minimal. Mean shifts in nearly all dimensions were limited to sub-centimeter or sub-degree changes, with 2D and cone beam CT (CBCT) imaging. Analysis of GaF showed that only 3 patients (10%) had field overlap. A new plan was created for 1 patient to increase the gap between fields, and for the others, patient and physician accepted overlap for adequate coverage.

CONCLUSION

To our knowledge, this is the first study examining clinical outcomes and setup reproducibility in patients treated with SBBC in the prone position. This study indicates the feasibility of prone bilateral breast treatment with minimal shifts and overlap on daily treatments. However, we do see a higher number of acute dermatitis in patients treated with bilateral WBI (vs. PBI) and that overlap was not seen on GaF in all patients who developed sternal dermatitis.

Characterization of Objective Skin Color Changes during and after Breast and Chest Wall Radiotherapy and Correlation with Radiation-Induced Skin Toxicity in Breast Cancer Patients, Including Patients with Skin of Color

PURPOSE/OBJECTIVE(S)

Radiation dermatitis (RD) is common among women undergoing breast and chest wall radiotherapy (RT); however, existing scales to assess the severity of RD are subjective and do not account for variability in skin of color (SOC). For instance, the Common Terminology Criteria for Adverse Events (CTCAE) criteria do not include hyperpigmentation in the grading scale. There is data indicating worse RD in African American and Hispanic patients; however, the rate and severity in SOC remains unknown given the lack of data using objective measures of RD. Spectrophotometry is one method to quantify the appearance of color by measuring spectral characteristics without the bias associated with subjective clinical scoring. We present a phase I prospective non-therapeutic clinical trial to objectively define SOC at baseline and evaluate spectrophotometric skin changes during and after breast or chest wall RT in parallel with physician-graded RD using CTCAE criteria. We hypothesize that there will be greater discrepancy between physician graded RD and objective measures of RD in patients with SOC in whom hyperpigmentation will be undercaptured by physician-grading. This is the first study intending to correlate SOC with objective changes after RT as a reliable indicator of RD. We offer a novel system for evaluating RD that is applicable to SOC.

MATERIALS/METHODS

A total of 60 patients with localized breast cancer (stage 0-III) undergoing conventional whole breast or chest wall RT (50Gy/ 25 fx), hypofractionated whole breast RT (40.5Gy/15 fx) or ultrahypofractionated partial breast RT (6Gy x5), with or without regional nodal RT were enrolled. 3 skin color readouts using the Commission International de l'Eclairage 3D color system (l*, a*, b*) were measured within the radiation field using a spectrophotometer at baseline, once weekly during RT, 10 days post RT, 4 weeks and 12 months post RT. The spectrophotometer is a non-invasive, hand-held device that is used in the clinic room with no additional equipment or setup requirements. Data is automatically exported to a spreadsheet organized by timepoint and patient. The l* axis is a gray scale (0 = black, 100 = white) correlating with skin pigmentation and the a* axis describes red and green values correlating with erythema. The primary objective is to evaluate the changes from baseline in skin color readouts in the quadrant of tumor location during and after RT based on fractionation. The secondary objective is to evaluate changes within and across groups defined by baseline skin color. Exploratory objectives include evaluating the association of baseline color readouts and changes after RT with acute and late grade > 2 clinician-rated skin and subcutaneous tissue effects according to the CTCAE, v5.0, physician graded cosmesis and clinical interventions to treat RD, such as use of topical steroids and oral analgesics. As of January 2023, we have enrolled 100% of the planned patients.

RESULTS

To be determined.

CONCLUSION

To be determined. Clinical Study Identifier: S22-00192.

A Phase II, Randomized, Double Blind, Placebo Controlled Study of the Safety and Efficacy of a Caffeine-Based Antifibrosis Cream in Patients with Breast Cancer Undergoing Radiation Therapy

PURPOSE/OBJECTIVE(S)

Radiation induced fibrosis (RIF) is a common long term adverse event in patients undergoing post-mastectomy radiation therapy (PMRT) which can cause capsular contracture, implant loss, and reconstruction complications in women with implant-based breast reconstruction. At a molecular level, adenosine is a driver of RIF. Preclinical data have shown that pharmacologic blockade of the adenosine A2A Receptor (A2AR) in mice as well as an A2AR knockout mouse model prevented skin fibrosis associated with radiation injury. Caffeine is an A2AR antagonist which has been shown to block the development of hepatic fibrosis in liver disease patients. We present a phase II placebo controlled clinical trial to evaluate whether a caffeine-based cream can prevent RIF and thus reduce the rates of reconstructive complications in patients with tissue expander-based reconstruction requiring PMRT.

MATERIALS/METHODS

Women ≥ 18 years old with breast carcinoma stage 0-III status post mastectomy with tissue expander-based reconstruction who require PMRT to the chest wall +/- the regional nodes are being enrolled. The target accrual is 60 patients. Boost field to the chest wall, scar and/or nodal region is allowed. Patients with inflammatory breast cancer or those requiring skin bolus are excluded. Prior to starting radiation, patients will be randomized to placebo vs. caffeine cream and they will be instructed to apply the cream twice a day starting on the first day of radiation treatment and continuing daily for the duration of radiation until the removal of tissue expanders. The primary study endpoint is reconstructive complications requiring rehospitalization or reoperation by 2 years post radiation including reconstructive failure with or without reconstruction. A safety endpoint of grade ≥ 2 acute radiation dermatitis will also serve as a co-primary endpoint. Secondary endpoints are wound infection/cellulitis, hematoma, seroma, threatened exposure, wound dehiscence, implant leakage, rupture, and or deflation, and capsular contracture that do not meet criteria for the primary endpoint. Clinician rated cosmesis, local recurrence, regional recurrence, distant metastasis and survival up to 4 years are additional secondary endpoints. Exploratory endpoint includes the use of shear wave elastography (SWE) as a potential tool to quantitatively measure post irradiation fibrosis. Correlative aims include assessing epidermal thickness and fat layer thickness from tissue obtained at time of implant exchange for association with the development of fibrosis. The primary efficacy endpoint will be estimated using Kaplan Meier methods from date of randomization. Treatment comparisons will be based on a 2-sided log rank chi-square test and the hazard ratio will be estimated with 95% confidence intervals. The study started accruing in 12/2019 and is estimated to end by 04/2024. As of January 2023, 67% (40/60 patients) of the planned patients have been enrolled.

RESULTS

To be determined.

CONCLUSION

To be determined.

Understanding Treatment Anxiety and Utility of Mixed Media Educational Tools in Radiation Oncology Consultation: A Qualitative Study

PURPOSE/OBJECTIVE(S)

Anxiety and adjustment disorders are prevalent in cancer patients, especially at the initiation of treatment, which may be alleviated by improved communication at initial consultation. The purpose of this study is to explore patients' needs in how radiation consultation may improve treatment-related anxiety and the role of multimedia visual tools.

MATERIALS/METHODS

Eight patients previously treated with partial or whole breast irradiation at our institution were interviewed in a semi-structured manner at a median of 1.54 months (range 0.13 - 12.42) after they completed radiation. Interview questions included expectations prior to consultation, experience of consultation and treatment, and the role of augmented reality or multimedia tools. Two independent reviewers performed an inductive, thematic analysis to generate themes and subthemes (inter-rater reliability = 0.79).

RESULTS

Four main themes were identified in thematic analysis: information expectations, anxiety, personalized education, and visual aids. Patients described preconceptions of radiation, desire for greater volume of information, importance of repetition from providers, benefit of seeing treatment set-up during simulation, and frustrations with the breath-holding process. Anxiety was related to fear of the unknown, difficulty remembering information when anxious, difficulty asking questions, and ambiguity of information worth worrying about. Patients expressed a desire for personalized education, including accounting for prior health conditions, varying health literacy, preference for individualized presentations, and minimizing extraneous input from those not on the healthcare team. Patients desired visuals during consultation, favored 3D technology over 2D mediums, acknowledged differences in learning style, and preferred an interactive component of patient education done in conjunction with visual tools.

CONCLUSION

While verbal consultation process provides valuable education regarding radiation treatment, patients continue to experience anxiety attributed to fear of the unknown. Augmenting the standard initial consultation with interactive visual aids, particularly in the form of a 3D medium, may enhance the patient experience at time of consultation. The results of this study will inform the development of a patient educational tool and clinical study named Curie therapy User eXperience (CurieUx) to be used during radiation oncology consultations.

Risk of Radiation Dermatitis in Patients With Skin of Color Who Undergo Radiation to the Breast or Chest Wall With and Without Regional Nodal Irradiation

PURPOSE

Acute radiation dermatitis (ARD) is common after radiation therapy for breast cancer, with data indicating that ARD may disproportionately affect Black or African American (AA) patients. We evaluated the effect of skin of color (SOC) on physician-reported ARD in patients treated with radiation therapy.

METHODS AND MATERIALS

We identified patients treated with whole breast or chest wall ± regional nodal irradiation or high tangents using 50 Gy in 25 fractions from 2015 to 2018. Baseline skin pigmentation was assessed using the Fitzpatrick scale (I = light/pale white to VI = black/very dark brown) with SOC defined as Fitzpatrick scale IV to VI. We evaluated associations among SOC, physician-reported ARD, late hyperpigmentation, and use of oral and topical treatments for RD using multivariable models.

RESULTS

A total of 325 patients met eligibility, of which 40% had SOC (n = 129). On multivariable analysis, Black/AA race and chest wall irradiation had a lower odds of physician-reported grade 2 or 3 ARD (odds ratio [OR], 0.110; 95% confidence interval [CI], 0.030-0.397; P = .001; OR, 0.377; 95% CI, 0.161-0.883; P = .025), whereas skin bolus (OR, 8.029; 95% CI, 3.655-17.635; P = 0) and planning target volume D0.03cc (OR, 1.001; 95% CI, 1.000-1.001; P = .028) were associated with increased odds. On multivariable analysis, SOC (OR, 3.658; 95% CI, 1.236-10.830; P = .019) and skin bolus (OR, 26.786; 95% CI, 4.235-169.432; P = 0) were associated with increased odds of physician-reported late grade 2 or 3 hyperpigmentation. There was less frequent use of topical steroids to treat ARD and more frequent use of oral analgesics in SOC versus non-SOC patients (43% vs 63%, P < .001; 50% vs 38%, P = .05, respectively).

CONCLUSIONS

Black/AA patients exhibited lower odds of physician-reported ARD. However, we found higher odds of late hyperpigmentation in SOC patients, independent of self-reported race. These findings suggest that ARD may be underdiagnosed in SOC when using the physician-rated scale despite this late evidence of radiation-induced skin toxicity.

Different Re-Irradiation Techniques after Breast-Conserving Surgery for Recurrent or New Primary Breast Cancer

Breast re-irradiation (reRT) after breast-conserving surgery (BCS) using external beam radiation is an increasingly used salvage approach for women presenting with recurrent or new primary breast cancer. However, radiation technique, dose and fractionation as well as eligibility criteria differ between studies. There is also limited data on efficacy and safety of external beam hypofractionation and accelerated partial-breast irradiation (APBI) regimens. This paper reviews existing retrospective and prospective data for breast reRT after BCS, APBI reRT outcomes and delivery at our institution and the need for a randomized controlled trial using shorter courses of radiation to better define patient selection for different reRT fractionation regimens.

Radiation-induced skin changes after breast or chest wall irradiation in patients with breast cancer and skin of color: a systematic review

INTRODUCTION

The purpose of this study is to systematically review data pertaining to breast cancer and radiation-induced skin reactions in patients with skin of color (SOC), as well as data pertaining to objective measurements of skin pigmentation in the assessment of radiation dermatitis (RD).

METHODS AND MATERIALS

We conducted a systematic review utilizing MEDLINE electronic databases to identify published studies until August 2022. Key inclusion criteria included studies that described RD in breast cancer with data pertaining to skin of color and/or characterization of pigmentation changes after radiation.

RESULTS

We identified 17 prospective cohort studies, 7 cross-sectional studies, 5 retrospective studies and 4 randomized controlled trials. Prospective cohort and retrospective series demonstrate worse RD in African American (AA) patients using subjective physician-graded scales. There is more limited data in patients representing other non-White racial subgroups with SOC. 2 studies utilize patient reported outcomes and 15 studies utilize objective methods to characterize pigmentation change after radiation. There are no prospective and randomized studies that objectively describe pigmentation changes with radiotherapy in SOC.

CONCLUSIONS

AA patients appear to have worse RD outcomes, though this is not uniformly observed across all studies. There are no studies that describe objective measures of RD and include baseline skin pigmentation as a variable, limiting the ability to draw uniform conclusions on the rate and impact of RD in SOC. We highlight the importance of objectively characterizing SOC and pigmentation changes before, during and after radiotherapy to understand the incidence and severity of RD in SOC.

Radiation in Early-Stage Breast Cancer: Moving beyond an All or Nothing Approach

Radiotherapy omission is increasingly considered for selected patients with early-stage breast cancer. However, with emerging data on the safety and efficacy of radiotherapy de-escalation with partial breast irradiation and accelerated treatment regimens for low-risk breast cancer, it is necessary to move beyond an all-or-nothing approach. Here, we review existing data for radiotherapy omission, including the use of age, tumor subtype, and multigene profiling assays for selecting low-risk patients for whom omission is a reasonable strategy. We review data for de-escalated radiotherapy, including partial breast irradiation and acceleration of treatment time, emphasizing these regimens' decreasing biological and financial toxicities. Lastly, we review evidence of omission of endocrine therapy. We emphasize ongoing research to define patient selection, treatment delivery, and toxicity outcomes for de-escalated adjuvant therapies better and highlight future directions.

Accelerated partial breast irradiation in early stage breast cancer

Accelerated partial breast irradiation (APBI) is increasingly used to treat select patients with early stage breast cancer. However, radiation technique, dose and fractionation as well as eligibility criteria differ between studies. This has led to controversy surrounding appropriate patients for APBI and an assessment of the toxicity and cosmetic outcomes of APBI as compared to whole breast irradiation (WBI). This paper reviews existing data for APBI, APBI delivery at our institution, and ongoing research to better define patient selection, treatment delivery, dosimetric considerations and toxicity outcomes.

Abstract CT243: Phase 1 study of TAK-676 + pembrolizumab following radiation therapy in patients with advanced non-small-cell lung cancer (NSCLC), triple-negative breast cancer (TNBC), or squamous-cell carcinoma of the head and neck (SCCHN)

Background: Radiation therapy has immune-modulating effects resulting from apoptosis of tumor cells and DNA damage. The downstream generation of cytosolic DNA activates the cyclic GMP-AMP Synthase (cGAS)-STimulator of INterferon Gene (STING) signaling axis in both tumor and nearby immune cells, leading to increased induction of type I interferon (IFN-I) and other immune stimulating molecules. TAK-676 is a novel synthetic STING agonist being investigated (+/- pembrolizumab) in an ongoing first-in-human phase 1 study (NCT04420884). TAK-676 is a potent modulator of the innate immune system and leads to downstream activation of the adaptive immune system to produce antitumor responses in preclinical studies. In contrast to intratumorally injected STING agonists, TAK-676 is optimally designed for reduced serum degradation and enhanced permeability, allowing systemic IV delivery and access to tumor sites and lymphatics. The addition of TAK-676 following radiation therapy may enhance the immune response by increasing the STING-mediated IFN-I release and further stimulate T cell-mediated antitumor immunity, particularly in combination with anti-PD-1/PD-L1 therapies. Impaired IFN signaling has been linked to checkpoint inhibitor (CPI) resistance. Preclinical studies show that addition of a STING agonist may reverse the mechanisms of resistance in tumors with prior exposure to CPIs. This phase 1 trial was designed to investigate the safety and preliminary antitumor activity of TAK-676 + pembrolizumab following radiation therapy (NCT04879849).

Methods: Patients aged ≥18 years with advanced NSCLC, TNBC, or SCCHN who have progressed on CPIs with ≥2 lesions, one of which can be targeted with radiation, are being enrolled. Patients receive 8 Gy x 3 fractions of image-guided radiation therapy followed by (after a minimum of 40 hours) IV pembrolizumab 200 mg on day 1 plus escalating doses of IV TAK-676 on days 1, 8, and 15 of a 21-day cycle. TAK-676 dose escalation is guided by the Bayesian Optimal Interval design. Patients receive TAK-676 + pembrolizumab until disease progression, intolerance, or withdrawal of consent. Once pharmacologically active dose levels of TAK-676 have been observed, paired biopsies will be collected in patients with a safely accessible lesion outside the radiation field at screening and between days 15 and 21 of cycle 1. The primary objective is to determine the safety and tolerability of TAK-676 + pembrolizumab following radiation therapy; secondary objectives are to determine the recommended phase 2 dose of TAK-676 + pembrolizumab following radiation therapy, and to assess preliminary antitumor activity both locally (in the radiation field) and systemically (non-radiated lesions). As of January 2022, nearly 10% of the planned patients have been enrolled.

Citation Format: Benjamin Cooper, Steven J. Chmura, Jason J. Luke, Stephen L. Shiao, Reva K. Basho, Wade T. Iams, David B. Page, Cong Li, Richard C. Gregory, Michael H. Shaw, Kristin H. Horn, John P. Gibbs, Vicky A. Appleman, Allison J. Berger, Adnan O. Abu-Yousif, Neil B. Lineberry, Kate F. Stumpo, Aymen Elfiky, Naamit K. Gerber. Phase 1 study of TAK-676 + pembrolizumab following radiation therapy in patients with advanced non-small-cell lung cancer (NSCLC), triple-negative breast cancer (TNBC), or squamous-cell carcinoma of the head and neck (SCCHN) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT243.

The Clinical Utility of DCISionRT® on Radiation Therapy Decision Making in Patients with Ductal Carcinoma In Situ Following Breast-Conserving Surgery

BACKGROUND

The role of radiation therapy (RT) following breast-conserving surgery (BCS) in ductal carcinoma in situ (DCIS) remains controversial. Trials have not identified a low-risk cohort, based on clinicopathologic features, who do not benefit from RT. A biosignature (DCISionRT®) that evaluates recurrence risk has been developed and validated. We evaluated the impact of DCISionRT on clinicians' recommendations for adjuvant RT.

METHODS

The PREDICT study is a prospective, multi-institutional, observational registry in which patients underwent DCISionRT testing. The primary endpoint was to identify the percentage of patients where testing led to a change in RT recommendations.

RESULTS

Overall, 539 women were included in this study. Pre DCISionRT testing, RT was recommended to 69% of patients; however, post-testing, a change in the RT recommendation was made for 42% of patients compared with the pre-testing recommendation; the percentage of women who were recommended RT decreased by 20%. For women initially recommended not to receive an RT pre-test, 35% had their recommendation changed to add RT following testing, while post-test, 46% of patients had their recommendation changed to omit RT after an initial recommendation for RT. When considered in conjunction with other clinicopathologic factors, the elevated DCISionRT score risk group (DS > 3) had the strongest association with an RT recommendation (odds ratio 43.4) compared with age, grade, size, margin status, and other factors.

CONCLUSIONS

DCISionRT provided information that significantly changed the recommendations to add or omit RT. Compared with traditional clinicopathologic features used to determine recommendations for or against RT, the factor most strongly associated with RT recommendations was the DCISionRT result, with other factors of importance being patient preference, tumor size, and grade.

Five-Fraction Prone Accelerated Partial Breast Irradiation: Long-Term Oncologic, Dosimetric, and Cosmetic Outcome

PURPOSE

Randomized data support accelerated partial breast irradiation (APBI) for early-stage breast cancer with variable techniques and cosmesis outcomes. We have treated patients with 5-fraction prone external beam APBI for over a decade and herein report acute and late outcomes.

METHODS AND MATERIALS

Patients receiving APBI 600 cGy × 5 between 2010 and 2019 were included. APBI was primarily delivered prone, with opposed tangents targeting the tumor bed expanded by 1.5 cm (cropped 6 mm from skin). Ipsilateral breast was constrained to V50% < 60% and V100% < 35%. Survival was estimated with Kaplan-Meier. Late toxicities and clinician- and patient-rated cosmesis were evaluated for patients with >6 months follow-up (FU).

RESULTS

Of 345 patients meeting criteria, 14 were excluded due to APBI given for ipsilateral breast tumor recurrence (IBTR; n = 3), palliation (n = 9), and incomplete radiation therapy course (n = 2). Of the 331 remaining, median age was 70, 7.2% had ductal carcinoma in situ, and 94.3% were treated prone, with 32% treated every other day and 68% on consecutive days. Mean heart dose was 23.8 cGy for left-sided and 12.7 cGy for right-sided cancers. Ipsilateral lung V30% was 0.4%. At 5-year median FU, there were 7 (2.1%) IBTR, 9 (2.7%) contralateral recurrences, and 1 (0.3%) distant metastasis. Five-year local recurrence-free, disease-free, and overall survival was 99.5%, 96.7%, and 98.1%, respectively. When comparing patients with IBTR versus without, a higher proportion did not receive hormone therapy (71.4% vs. 26.2%, P = .018). Rates of acute grade 1 to 2 dermatitis, fatigue, and pain were 35.4%, 21.8%, and 9.4%, respectively, with no grade 3 toxicity. The rate of good-excellent physician- and patient-rated cosmesis (n = 199, median FU 2.8 years) was 92.5% and 89.4%, respectively. Patients experienced low rates of telangiectasia, fibrosis, and retraction/atrophy.

CONCLUSIONS

We report excellent dosimetric, oncologic, cosmetic, and late toxicity outcomes for patients treated with 5-fraction APBI. To our knowledge this is the largest series of women treated with prone APBI.

Early Stage Pregnancy During Radiation Therapy to the Breast

We describe a model case of unplanned pregnancy during radiation therapy to the chest wall and peripheral lymphatics for breast cancer. We use the Morbidity and Mortality Conference format to demonstrate how radiation oncology departments should evaluate and manage this situation.

Breast Conservation in Women with Autoimmune Disease: The Role of Active Autoimmune Disease and Hypofractionation on Acute and Late Toxicity in a Case-Controlled Series

PURPOSE

Autoimmune connective tissue disease (CTD) has historically represented a relative contraindication to breast conservation (BC) among patients with early-stage breast cancer. Controversy exists regarding the use of hypofractionated radiation therapy (RT) among patients with CTDs. We evaluated acute and late toxicity in patients with breast cancer and CTD treated with BC.

METHODS AND MATERIALS

Of 1983 patients treated with BC from 2012 to 2016, we identified 91 patients with an autoimmune disease (AD). Each patient was matched to a control without AD based on age, RT field, and fractionation. RT toxicity and clinician-rated cosmesis were compared between cases and controls. Overall survival, disease-free survival, and local recurrence-free survival were estimated using the Kaplan-Meier method.

RESULTS

The median follow-up was 49.9 months for cases and 53.0 months for controls, and 67% of cases and controls were treated with hypofractionated RT. There was no difference in grade 2/3 acute toxicity between cases and controls (26.4% vs. 16.5%, respectively; P = .148). There was a significantly higher rate of grade 2/3 late toxicity among cases (25.8% vs 12.1% among controls; P = .049). Active AD at the time of RT increased the rate of grade 2/3 late toxicity compared with controls (41.7% in cases vs. 11.4% in controls; P = .018). Among patients treated with hypofractionated RT, there was no difference in acute or late grade 2/3 toxicity between cases and controls (acute: 13.1% in cases vs. 11.5% in controls [P > 0.9]; late: 11.9% in cases vs. 13.1% in controls [P > 0.9]). The rates of good/excellent clinician-rated cosmesis were similar between groups (92.9% in cases vs. 98.9% in controls; P = .142).

CONCLUSIONS

In the largest matched case-control study of patients with CTD treated with conventional and hypofractionated RT, we demonstrate low rates of radiation toxicity, with good to excellent clinician-rated cosmesis. There was increased late toxicity in cases, especially in patients with active AD at time of RT. There was no increase in acute or late toxicity in the patients treated with hypofractionation.

Radiation Without Endocrine Therapy in Older Women With Stage I Estrogen-Receptor-Positive Breast Cancer Is Not Associated With a Higher Risk of Second Breast Cancer Events

PURPOSE

The omission of radiation therapy (RT) in older women with stage 1 estrogen-receptor-positive (ER+) breast cancer receiving endocrine therapy (ET) is an acceptable strategy based on randomized trial data. Less is known about the omission of ET with or without RT.

METHODS AND MATERIALS

We analyzed surveillance, epidemiology, and end results (SEER)-Medicare data for 13,321 women age 66 years or older with stage I ER+ breast cancer from 2007 to 2012 who underwent breast-conserving surgery. Patients were classified into 4 groups: (1) ET + RT (reference); (2) ET alone; (3) RT alone; and (4) neither RT nor ET (NT). Second breast cancer events (SBCEs) were captured using the Chubak high-specificity algorithm. We used χ² tests for descriptive statistics, multivariable multinomial logistic regression to estimate relative risk of undergoing a treatment, and multivariable, propensity-weighted competing-risks survival regression to estimate standardized hazard ratio (SHR) of SBCE. We set significance at P ≤ .01.

RESULTS

Most women underwent both treatments, with 44% undergoing ET + RT, 41% RT alone, 6.6% ET alone, and 8.6% NT, but practice patterns varied over time. From 2007 to 2012, RT decreased from 49% to 30%, whereas ET alone and ET + RT increased (ET alone, 5.4%-9.6%; ET + RT, 38%-51%). Compared with patients age 66 to 69 years, patients age 80 to 85 years were more likely to receive NT (odds ratio [OR], 8.9), RT (OR, 1.9), or ET (OR, 8.8) versus ET + RT (P < .01). Three percent of subjects had an SBCE (2.2% ET + RT, 3.0% RT alone, 3.2% ET alone, 7.0% NT). Relative to ET + RT, NT and ET alone were associated with higher SBCE (NT: SHR, 3.7, P < .001; ET alone: SHR, 2.2, P = .008), whereas RT was not associated with a higher SBCE (SHR 1.21; P = .137). Clinical factors associated with higher SBCE were HER2 positivity and pT1c (SHR, 1.7; P = .006).

CONCLUSIONS

Treatment with RT alone in older women with stage I ER+ disease is decreasing. RT alone is not associated with an increased risk for SBCE. By contrast, NT and ET are both associated with higher SBCE in multivariable analysis with propensity weighting. Further study of the omission of endocrine therapy in this patient population is warranted.

Ductal Carcinoma in Situ in Young Women: Increasing Rates of Mastectomy and Variability in Endocrine Therapy Use

BACKGROUND

Young women with ductal carcinoma in situ (DCIS) represent a unique cohort given considerations for future risk reduction and treatment effects on fertility and quality of life. We evaluated national patterns of care in the treatment of young women and the impact of those treatments on overall survival (OS).

METHODS

Women younger than 50 years of age diagnosed with pure DCIS from 2004 to 2016 in the National Cancer Database (NCDB) were identified. Clinical, demographic, and choice of local therapy are summarized and trended over time. OS was analyzed using Cox proportional hazard models.

RESULTS

A total of 52,150 women were identified, and the most common surgical treatment was breast-conservation surgery (BCS; 59%). Bilateral mastectomy (BM) increased in frequency from 2004 to 2016 (11-27%; p < 0.001). In women < 40 years of age, BM (39%) surpassed BCS (35%) in 2010 with a continued upward trend. On multivariable analysis, no OS benefit of BM (hazard ratio [HR] 0.99, p = 0.90) or unilateral mastectomy (UM; HR 0.98, p = 0.80) was observed when compared with BCS + radiation therapy (RT). Inferior OS was seen with BCS, Black race, estrogen receptor (ER)-negative, and tumor ≥ 2.5 cm (p ≤ 0.006). In ER+ patients, there was a significant difference in endocrine therapy (ET) use between BM (11%), UM (33%), and BCS (28%) compared with BCS + RT (64%, p < 0.001).

CONCLUSION

The use of BM for DCIS is increasing in younger patients and now exceeds breast-conservation approaches in women < 40 years of age with no evidence of improved OS. Among ER+ patients, the rates of ET are lower in the BM, UM, and BCS-alone groups compared with BCS + RT.

Breaking Tradition to Bridge Bench and Bedside: Accelerating the MD-PhD-Residency Pathway

PROBLEM

Physician-scientists are individuals trained in both clinical practice and scientific research. Often, the goal of physician-scientist training is to address pressing questions in biomedical research. The established pathways to formally train such individuals are mainly MD-PhD programs and physician-scientist track residencies. Although graduates of these pathways are well equipped to be physician-scientists, numerous factors, including funding and length of training, discourage application to such programs and impede success rates.

APPROACH

To address some of the pressing challenges in training and retaining burgeoning physician-scientists, New York University Grossman School of Medicine formed the Accelerated MD-PhD-Residency Pathway in 2016. This pathway builds on the previously established accelerated 3-year MD pathway to residency at the same institution. The Accelerated MD-PhD-Residency Pathway conditionally accepts MD-PhD trainees to a residency position at the same institution through the National Resident Matching Program.

OUTCOMES

Since its inception, 2 students have joined the Accelerated MD-PhD-Residency Pathway, which provides protected research time in their chosen residency. The pathway reduces the time to earn an MD and PhD by 1 year and reduces the MD training phase to 3 years, reducing the cost and lowering socioeconomic barriers. Remaining at the same institution for residency allows for the growth of strong research collaborations and mentoring opportunities, which foster success.

NEXT STEPS

The authors and institutional leaders plan to increase the number of trainees who are accepted into the Accelerated MD-PhD-Residency Pathway and track the success of these students through residency and into practice to determine if the pathway is meeting its goal of increasing the number of practicing physician-scientists. The authors hope this model can serve as an example to leaders at other institutions who may wish to adopt this pathway for the training of their MD-PhD students.

Outcomes of HER2-positive non-metastatic breast cancer patients treated with anti-HER2 therapy without chemotherapy

PURPOSE

Anti-HER2 therapy delivered in the adjuvant setting for breast cancer is given in conjunction with cytotoxic chemotherapy. For HER2-positive (HER2+) patients who cannot tolerate chemotherapy, there is no randomized data regarding the role of anti-HER2 therapy without chemotherapy.

METHODS

The National Cancer Database (NCDB) was queried for non-metastatic breast cancer patients with estrogen receptor-positive (ER+) and HER2+ breast cancer who received surgery and endocrine therapy, without chemotherapy from 2013 to 2016. Outcomes were compared between endocrine therapy alone (ET) or endocrine therapy with anti-HER2 therapy (ET + aHER2). Univariate and multivariate Cox-proportional hazards models were used to analyze the association between clinical characteristics and survival outcomes between groups. Propensity score matching (PSM) was performed to account for differences between the two groups.

RESULTS

Of all patients with non-metastatic ER+/HER2+ breast cancer, we identified 9458 (20.5%) who did not receive chemotherapy. Of the 6741 patients who received ET, 17.2% also received aHER2 therapy. Median follow-up was 31.7 months (IQR 21.1-42.1). In the aHER2 group (vs. ET), there were more patients with older age, higher stage, node positivity, poorly or undifferentiated disease, lymphovascular invasion, lobular cancer, and Medicare insurance. Compared to the ET cohort, ET + aHER2 was not significantly associated with improved OS on multivariate analysis (HR 0.88 95% CI 0.68-1.15) or after propensity score matching (HR 0.80 95% CI 0.57-1.11).

CONCLUSIONS

There is no significant difference in survival with the addition of HER2 therapy to endocrine therapy in ER+/HER2+ non-metastatic breast cancer patients who do not receive chemotherapy. To our knowledge, this is the largest series investigating this question.

Automatic treatment planning for VMAT-based total body irradiation using Eclipse scripting

The purpose of this work is to establish an automated approach for a multiple isocenter volumetric arc therapy (VMAT)‐based TBI treatment planning approach. Five anonymized full‐body CT imaging sets were used. A script was developed to automate and standardize the treatment planning process using the Varian Eclipse v15.6 Scripting API. The script generates two treatment plans: a head‐first VMAT‐based plan for upper body coverage using four isocenters and a total of eight full arcs; and a feet‐first AP/PA plan with three isocenters that covers the lower extremities of the patient. PTV was the entire body cropped 5 mm from the patient surface and extended 3 mm into the lungs and kidneys. Two plans were generated for each case: one to a total dose of 1200 cGy in 8 fractions and a second one to a total dose of 1320 cGy in 8 fractions. Plans were calculated using the AAA algorithm and 6 MV photon energy. One plan was created and delivered to an anthropomorphic phantom containing 12 OSLDs for in‐vivo dose verification. For the plans prescribed to 1200 cGy total dose the following dosimetric results were achieved: median PTV V100% = 94.5%; median PTV D98% = 89.9%; median lungs Dmean = 763 cGy; median left kidney Dmean = 1058 cGy; and median right kidney Dmean = 1051 cGy. For the plans prescribed to 1320 cGy total dose the following dosimetric results were achieved: median PTV V100% = 95.0%; median PTV D98% = 88.7%; median lungs Dmean = 798 cGy; median left kidney Dmean = 1059 cGy; and median right kidney Dmean = 1064 cGy. Maximum dose objective was met for all cases. The dose deviation between the treatment planning dose and the dose measured by the OSLDs was within ±4%. In summary, we have demonstrated that scripting can produce high‐quality plans based on predefined dose objectives and can decrease planning time by automatic target and optimization contours generation, plan creation, field and isocenter placement, and optimization objectives setup.

Current Social Media Use Among Radiation Oncology Trainees

Purpose

Resident physicians use social media (SM) for many reasons. We sought to characterize current SM use by radiation oncology (RO) trainees for education and professional development.

Methods and Materials

An anonymous 40-question survey was sent by e-mail to RO residents in the 2018 to 2019 academic year. SM platform use, time spent on SM, professional use, and opinions regarding SM use were assessed. Descriptive statistics and a univariate logistic regression analysis were performed to identify factors associated with perceptions of SM and spending >25% of SM time for academic or professional purposes.

Results

Of the 615 residents surveyed, 149 responded (24% response rate). Facebook (73%), theMednet (62%), Instagram (59%), Twitter (57%), and Doximity (50%) were the top SM platforms used. Most respondents (53%) reported <25% of overall SM time on professional/academic purposes, and 21% reported using SM >60 minutes per day over the past week. Residents with an RO mentor on SM (n = 35; 24%; odds ratio [OR]: 2.79; 95% confidence interval [CI], 1.29-6.08; P = .010), those participating in RO discussions on SM (n = 71; 48%; OR: 2.85; 95% CI, 1.42-5.72; P = .003), and those interacting with professional societies (n = 69; 46%; OR: 7.11; 95% CI, 3.32-15.24; P < .001) were more likely to spend >25% of their SM time on professional/academic purposes. The vast majority of respondents agreed that SM exposed them to novel educational content (82%) and was helpful for career development (65%). In addition, 69% agreed that SM can improve clinical skills and knowledge. A substantial minority agreed that SM distracts them from studying (38%) or they felt pressure to have a SM presence (29%).

Conclusions

Most RO residents reported that SM provides novel educational content and can help with career development. Potential disadvantages of SM for trainees may include distraction and pressure to maintain a SM presence. SM use by RO trainees merits further research to optimize its potential for education and professional development.

Radiation Dose Reduction in Early-Stage Hodgkin Lymphoma

INTRODUCTION

Treatment for early-stage Hodgkin lymphoma (HL) involves radiotherapy (RT), chemotherapy, or combined modality therapy (CMT). We analyzed reduction of RT dose in CMT, particularly in the context of German Hodgkin Study Group (GHSG) HD10 randomized trial results of 2010.

PATIENTS AND METHODS

The National Cancer Data Base was queried for patients with stage I-II HL receiving CMT. RT dose and associated characteristics were analyzed. Stage I and absence of B symptoms were used as a surrogate for early-stage favorable disease.

RESULTS

Of 31,301 patients with stage I-II HL, 11,457 received CMT between 2004 and 2015. Using the surrogate defined above, 1955 patients (17.1%) were classified as having favorable disease. The majority (61.6%) received 30-36 Gy, while 7.0% received 20 Gy. The provision of 20 Gy was more common in stage I patients (12.3% vs. 5.4% in stage II) and at academic facilities (10.8% vs. 6.3%-8.9% at other facilities). Use of 20 Gy (vs. 30-36 Gy) was less likely with thorax site (odds ratio [OR] 0.43 vs. head and neck), stage II disease (OR 0.41), and B symptoms (OR 0.33). Notably, the use of 20 Gy increased dramatically after 2010 (the year of publication of GHSG HD10 trial results), with rates of 12.3% in 2010-2015 versus 0.1% in 2004-2009 (OR 6.3, P < .001). This was even more pronounced in cases of favorable early-stage disease, with 25.5% after 2010 versus 2.8% before 2010 (OR 13.2, P < .001). The use of doses > 36 Gy decreased over a corresponding time period (OR 0.44, P < .001).

CONCLUSION

Analysis of CMT for patients with early-stage HL demonstrates variability in RT dose, including increasing use of 20 Gy and decreasing use of high doses > 36 Gy.

Abstract P1-18-02: Outcomes of patients with ER+/HER2+ non-metastatic breast cancer treated with trastuzumab without chemotherapy

Purpose: The development of trastuzumab has significantly improved prognosis and treatment of Her2 positive breast cancer. The efficacy of trastuzumab monotherapy is limited and thus standard of care is to combine trastuzumab with chemotherapy. Yet for those who cannot tolerate chemotherapy, there is no randomized data comparing no trastuzumab with trastuzumab monotherapy in the non-metastatic setting. We therefore examined the outcomes of non-metastatic patients treated with trastuzumab without chemotherapy in the National Cancer Database (NCDB). Methods: We included female patients from 2013-2016 with clinical stage I-III breast cancer who received surgery with ER+/HER+ disease. Patients treated with Her2 therapy after 2013 had their treatment classified under immunotherapy, whereas those treated before 2013 had Her2 therapy classified under chemotherapy. Exclusion criteria included male sex, prior cancer history, and clinical stage IV disease. We also excluded patients with pathologic stage 0 (DCIS), stage IV, or unknown pathologic stage. Treatments compared included chemotherapy (CT), adjuvant hormone therapy alone (HT), combination HT + trastuzumab (HT+T), and no adjuvant treatment (NT). Pearson chi square analysis, one-way ANOVA, and the Kaplan Meier method was used to evaluate the differences in clinical characteristics for the treatment groups and effects of treatment on overall survival. Results: We identified 46,025 patients who met eligibility criteria. The median follow-up was 31 months (SD 13.16) for CT, 30 months (SD 14.07) for HT, 30 months (SD 12.87) for HT + T, and 27 months (SD 14.61) for NT. Most patients received standard of care with CT (78%, n=36008), 12% (n=5632) received adjuvant HT without T (HT), 3% (n=1157) were treated with HT+T, and 12% (n=2669) with NT. There was a higher representation of elderly patients &gt;70 years old in the HT (41%) and HT +T (51%) and NT arm (38%) compared to the CT arm (13%). There was a higher representation of lobular histology specifically in the HT + T arm (52%) compared to CT (11%), HT (11%), or NT arm (11%). There was a higher representation of patients with Charlson Deyo Comorbidity Scores of 1-2 (vs. 0) in the HT (21%) and HT +T arms (21%) compared to the CT (15%) or NT (18%) arms. There was a higher representation of node positive patients (N1-3 vs. N0) in the CT (38%) and HT+T (27%) groups vs. the HT (13%) and NT (16%) arms. Similarly, there were more patients with high grade disease (G3) and lymphovascular invasion (+LVI) in the CT (48% G3, 25% +LVI) and HT+T (45% G3, 20% +LVI) arms vs. in the HT (30% G3, 12% +LVI) and NT (39% G3, 15% +LVI) arms. Medicare patients were more likely to be treated with HT +T (58%) or HT (50%) than CT (24%) or NT (45%) which likely reflects the overlap of Medicare and older age. As compared to the standard of care CT arm, the patients treated without CT, had significantly worse overall survival. There was no improvement in OS for HT+T vs. HT without T. Hazard ratios for treatment regimens without CT were significantly worse with a HR 2.26 (95% CI 0.4-1.9) for HT without T, 3.01 (95% CI 0.3-2.3) for HT + T, and 4.37 (95% CI 3.7-5.1) for NT (p&lt;0.0001). Conclusions: This is the largest retrospective analysis of US patients with ER+/HER2+ non-metastatic breast cancer. Those treated with HT + T (vs. CT, HT, and NT) are more likely to have lobular histology. Patients treated with HT+T (vs. HT) are more likely to have more aggressive disease including higher nodal stage, higher grade, and the presence of LVI. Those treated with HT+T (vs. CT) are more likely to be older. We fail to identify an OS benefit with HT + T compared to HT alone though further analysis including a multivariate analysis and propensity score matching will further elucidate the outcome of this group.

Citation Format: Susanna Nguy, S. Peter Wu, Cheongeun Oh, Naamit K Gerber. Outcomes of patients with ER+/HER2+ non-metastatic breast cancer treated with trastuzumab without chemotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-18-02.

A Prospective Trial to Compare Deep Inspiratory Breath Hold With Prone Breast Irradiation

PURPOSE

To compare heart and lung doses for adjuvant whole breast irradiation (WBI) between radiation plans generated supine with deep inspiratory breath hold (S-DIBH) and prone with free-breathing (P-FB) and examine the effect of breast volume (BV) on dosimetric parameters.

METHODS AND MATERIALS

Patients with left breast ductal carcinoma in situ or invasive cancer receiving adjuvant WBI were enrolled on a single-institutional prospective protocol. Patients were simulated S-DIBH and P-FB; plans were generated using both scans. Wilcoxon signed-rank and rank-sum tests were used to compare intrapatient differences between plans for the entire cohort and within BV groups defined by tertiles.

RESULTS

Forty patients were enrolled. Thirty-four patients are included in the analysis owing to patient withdrawal or inability to hold breath. With WBI dose of 4005 to 4256 cGy, mean heart dose (MHD) was 80 cGy in S-DIBH and 77 cGy in P-FB (P = .08). Mean ipsilateral lung dose (MLD) was 453 cGy in S-DIBH and 45 cGy in P-FB (P < .0001). Mean and max left anterior descending artery doses were 251 cGy and 551 cGy in S-DIBH, respectively (P = .1), and 324 cGy and 993 cGy in P-FB, respectively (P = .3). Hot spot and separation were 109% and 22 cm in S-DIBH, respectively, and 107% and 16 cm in P-FB, respectively (P < .0001). For patients with smallest BV, S-DIBH improved MHD and left anterior descending artery doses; for those with largest BV, P-FB improved cardiac dosimetry. With increasing BV, there was an increasing advantage of P-FB for MHD (P = .05), and max (P = .03) and mean (P = .02) left anterior descending artery doses, and the reduction in MLD, hot spot, and separation with P-FB increased (P < .05).

CONCLUSIONS

MHD did not differ between P-FB and S-DIBH, whereas MLD was significantly lower with P-FB. Analysis according to breast volume revealed improved cardiac dosimetry with S-DIBH for women with smallest BV and improved cardiac dosimetry with P-FB for women with larger BV, thereby providing a dosimetric rationale for using breast size to help determine the optimal positioning for WBI.

Ipsilateral breast tumor recurrence in early stage breast cancer patients treated with breast conserving surgery and adjuvant radiation therapy: Concordance of biomarkers and tumor location from primary tumor to in-breast tumor recurrence

BACKGROUND

Patients with an in-breast tumor recurrence (IBTR) after breast-conserving therapy have a high risk of distant metastasis and disease-related mortality. Classifying clinical parameters that increase risk for recurrence after IBTR remains a challenge.

AIM

To describe primary and recurrent tumor characteristics in patients who experience an IBTR and understand the relationship between these characteristics and disease outcomes.

METHODS

Patients with stage 0-II breast cancer treated with lumpectomy and adjuvant radiation were identified from institutional databases of patients treated from 2003-2017 at our institution. Overall survival (OS), disease-free survival, and local recurrence-free survival (LRFS) were estimated using the Kaplan Meier method. We identified patients who experienced an isolated IBTR. Concordance of hormone receptor status and location of tumor from primary to recurrence was evaluated. The effect of clinical and treatment parameters on disease outcomes was also evaluated.

RESULTS

We identified 2164 patients who met the eligibility criteria. The median follow-up for all patients was 3.73 [interquartile range (IQR) 2.27-6.07] years. Five-year OS was 97.7% (95%CI: 96.8%-98.6%) with 28 deaths; 5-year LRFS was 98.0% (97.2-98.8) with 31 IBTRs. We identified 37 patients with isolated IBTR, 19 (51.4%) as ductal carcinoma in situ and 18 (48.6%) as invasive disease, of whom 83.3% had an in situ component. Median time from initial diagnosis to IBTR was 1.97 (IQR: 1.03-3.5) years. Radiotherapy information was available for 30 of 37 patients. Median whole-breast dose was 40.5 Gy and 23 patients received a boost to the tumor bed. Twenty-five of thirty-two (78.1%) patients had concordant hormone receptor status, HER-2 receptor status, and estrogen receptor (ER) (P = 0.006) and progesterone receptor (PR) (P = 0.001) status from primary to IBTR were significantly associated. There were no observed changes in HER-2 status from primary to IBTR. The concordance between quadrant of primary to IBTR was 10/19 [(62.2%), P = 0.008]. Tumor size greater than 1.5 cm (HR = 0.44, 95%CI: 0.22-0.90, P = 0.02) and use of endocrine therapy upfront (HR = 0.36, 95%CI: 0.18-0.73, P = 0.004) decreased the risk of IBTR.

CONCLUSION

Among patients with early stage breast cancer who had breast conserving surgery treated with adjuvant RT, ER/PR status and quadrant were highly concordant from primary to IBTR. Tumor size greater than 1.5 cm and use of adjuvant endocrine therapy were significantly associated with decreased risk of IBTR.

Radiation effect on late cardiopulmonary toxicity: An analysis comparing supine DIBH versus prone techniques for breast treatment

Two commonly used whole breast irradiation (WBI) techniques, deep inspiration breath hold (DIBH) and prone positioning, are compared with regard to dosimetry and estimated late cardiac morbidity and secondary lung cancer mortality using published models. Forty patients with left-sided DCIS or breast cancer who underwent lumpectomy and required adjuvant WBI were enrolled on a prospective trial comparing supine DIBH (S-DIBH) with prone free breathing (P-FB) planning. Patients underwent CT simulation in both positions; two plans were generated for each patient. Comparative dosimetry was available for 34 patients. Mean cardiac and lung doses were calculated. Risk of death from ischemic heart disease (IHD), risk of at least one acute coronary event (ACE), and lung cancer mortality were estimated from published data. Difference between S-DIBH and P-FB plans was compared using paired two-tailed t test. Estimated mean risk of death from IHD by age 80 was 0.1% (range 0.0%-0.2%) for both plans (P = 1.0). Mean risk of at least one ACE was 0.3% (range 0.1%-0.6%) for both plans (P = .6). Mean lung cancer mortality risk was 1.4% (range 0.5%-15.4%) for S-DIBH and 1.0% (range 0.4%-9.8%) for P-FB (P = .008). Excess lung cancer mortality due to radiation was 0.5% (range 0.1%-6.0%) with S-DIBH and 0.0% (range 0.0%-0.4%) with P-FB (P = .008). Both S-DIBH and P-FB provide excellent cardiac sparing. Prone positioning results in lower lung dose than S-DIBH and leads to an absolute decrease of 0.5% in excess lung cancer mortality for patients receiving WBI.

The Implications of Genetic Testing on Radiation Therapy Decisions: A Guide for Radiation Oncologists

The advent of affordable and rapid next-generation DNA sequencing technology, along with the US Supreme Court ruling invalidating gene patents, has led to a deluge of germline and tumor genetic variant tests that are being rapidly incorporated into clinical cancer decision-making. A major concern for clinicians is whether the presence of germline mutations may increase the risk of radiation toxicity or secondary malignancies. Because scarce clinical data exist to inform decisions at this time, the American Society for Radiation Oncology convened a group of radiation science experts and clinicians to summarize potential issues, review relevant data, and provide guidance for adult patients and their care teams regarding the impact, if any, that genetic testing should have on radiation therapy recommendations. During the American Society for Radiation Oncology workshop, several main points emerged, which are discussed in this manuscript: (1) variants of uncertain significance should be considered nondeleterious until functional genomic data emerge to demonstrate otherwise; (2) possession of germline alterations in a single copy of a gene critical for radiation damage responses does not necessarily equate to increased risk of radiation-induced toxicity; (3) deleterious ataxia-telangiesctasia gene mutations may modestly increase second cancer risk after radiation therapy, and thus follow-up for these patients after indicated radiation therapy should include second cancer screening; (4) conveying to patients the difference between relative and absolute risk is critical to decision-making; and (5) more work is needed to assess the impact of tumor somatic alterations on the probability of response to radiation therapy and the potential for individualization of radiation doses. Data on radiosensitivity related to specific genetic mutations is also briefly discussed.

Adjuvant endocrine monotherapy (ET) versus adjuvant breast radiation (RT) alone in healthy older women with stage I, estrogen receptor-positive (ER+) breast cancer: An analysis of the National Cancer Database (NCDB)

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Background: The NCCN guidelines state that breast RT may be omitted in patients > 70 years of age with ER+, clinically node-negative, T1 breast cancer (BC) who receive adjuvant ET. Available data on older patients notes that local relapses are the most frequent site of failure, and distant relapse rates are low. The side effects of ET are not inconsequential and negatively affect QOL. The objectives of this study are to examine clinical outcomes including overall survival (OS) in women ≥70 years of age treated by lumpectomy(L)+ET and L+RT in the NCDB. Methods: The 2004-2013 NCDB includes 76,431 women ≥70 years with ER+ stage I BC who underwent L, and had a minimum one year follow up. Women who received no adjuvant therapy, both ET+RT, or any chemotherapy were excluded. To limit the analysis to healthy women, we excluded subjects with a Charlson comorbidity index > 0. We identified 24,572 patients who received either adjuvant ET monotherapy or adjuvant RT alone. Among these, 46% (11,313) received ET and 54% (13,259) breast RT. Overall median follow up was 57 months (range: 12-143 months). Analysis of OS between the 2 treatment groups was performed using Kaplan-Meier statistics and Cox proportional hazards regression; propensity weighting was used to balance covariates across the 2 treatment groups. Results: After propensity weighting, demographic covariates including age, race, insurance, and facility type were balanced between the 2 treatment groups. The median OS for ET was 125.9 months (95% CI 120.1-131.8), and 127.2 months for RT (95% CI 124.5-131.7) (p < 0.0001). The weighted hazard of death was 11.7% less in women receiving RT compared to ET (HR 0.883, 95% CI 0.834-0.936, p < 0.0001). Conclusions: To our knowledge, this is the first large study comparing RT and ET monotherapy in healthy older women with stage I, ER+ BC. The OS with RT alone is not inferior to ET alone, and in this study population is noted to be better. While this analysis has various limitations not dissimilar from other NCDB database studies, our observations are encouraging and warrant further research with prospective studies.

The Evolving and Multidisciplinary Considerations in Nodal Radiation in Breast Cancer

The therapeutic management of regional lymph nodes in breast cancer has seen a remarkable change in the past 2 decades. Clinical trials have refined our knowledge regarding the biology of the disease including the prognostic significance of disease in the regional lymph nodes. The contemporary management of lymph nodes is also influenced by advances in surgical technique, radiation oncology delivery systems, and effective systemic therapy regimens. This paper describes the role of regional nodal irradiation in the context of the de-escalation of axillary surgery, improved understanding of the molecular and pathologic features, and increasing use of neoadjuvant chemotherapy.

Model-based cardiac dose estimation in radiation treatment of left breast cancer

OBJECTIVE:

To develop a mathematical model for cardiac dose estimation for patients who have been treated for left-sided breast cancer without CT data.

METHODS:

After obtaining institutional review board approvals, 147 patients with left-sided breast cancer were selected that were treated supine with opposed tangents. The heart blocks from the tangential fields were removed and dose calculations were performed with 6 MV beams using an advanced algorithm. This study was performed with CT data with DRR to represent a radiographic simulator image of yesteryear treatments. The beam's eye-view images showing delineated breast, lung and heart were created to represent views on radiograph. The maximum heart distance (MHD) was recorded and irradiated heart area (AREA) was computed by combination of triangles and rectangles. Based on accurate 3D dose calculation, mean dose (D_mean) and V₁₀ to V₅₀ of heart were analyzed with respect to MHD and AREA for dosimetric parameters using linear and quadratic fit.

RESULTS:

The treatment parameters calculated by MHD and segments using 2D radiographs were within 2% of the actual dosimetric parameters computed from the 3D planning system. The MHD and AREA vs D_mean, V₁₀, V₂₀, V₃₀ and V₅₀ showed very good correlation with linear model (R² > 0.91); however the correlation was significantly better with quadratic model (R² > 0.92). The analysis of the dosimetric error with our linear and quadratic model is remarkable within <3% error for most cases.

CONCLUSION:

The proposed mathematical model for the cardiac dose estimation is accurate within ±3% using a radiograph without CT data. This provides avenues for patient pooling in future studies related to radiation dose and cardiac toxicity. These results will help in estimating cardiac dose analysis accurately from previous studies as well as in centers still using 2D planning.

ADVANCES IN KNOWLEDGE:

The evidence of cardiac risk following radiotherapy continues to be one of the important considerations for the management of left-sided breast cancer patients. One of the problem in the estimation of dose-risk effects is the reconstruction of heart dose for pre-CT treatments. In this study, a simple mathematical model is presented that could estimate cardiac dose within ±3% in left breast cancer treatment from 2D radiograph where CT data do not exist.

The impact of adjuvant chemoradiotherapy timing on survival of head and neck cancers

BACKGROUND

Delays in postoperative head and neck (HN) radiotherapy have been associated with decreased overall survival; however, the impact of delays in postoperative HN chemoradiotherapy remains undefined.

METHODS

All patients with nonmetastatic HN cancer (oral cavity, oropharynx, larynx, hypopharynx) who underwent curative intent surgery and received adjuvant chemoradiotherapy were identified from the National Cancer Database (2005-2012). Overall treatment time (OTT) was defined as the time from surgery to the end of radiation therapy. Statistical methods included Cox proportional hazards modeling, which adjusted for clinicopathologic, demographic, and socioeconomic factors. Recursive partitioning analysis (RPA) identified the optimal threshold of OTT via conditional inference trees to estimate the greatest differences in overall survival (OS) on the basis of randomly selected training and validation sets.

RESULTS

A total of 16,733 patients were included, with a median follow-up of 37 months. Median OS for OTT in a predefined threshold of ≤ 13 weeks was 10.1 years (95% confidence interval [CI], 9.8 years; not reached) compared with 8.7 years (95% CI, 8.2-9.2 years) in > 13 weeks. On multivariate analysis, OTT of > 13 weeks versus ≤ 13 weeks independently increased mortality risk (hazard ratio, 1.10; 95% CI, 1.04-1.17; P = < 0.001). RPA identified an optimal OTT threshold of 97 days (interquartile range: 96-98 days). The OTT threshold of 97 days was confirmed in a full Cox regression model estimating the risk of death according to overall treatment time as a continuous variable.

CONCLUSION

In this large hospital-based national data, an OTT of greater than approximately 14 weeks most consistently increased the risk of death.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:2326-2332, 2018.

Utilization and Survival of Postoperative Radiation or Chemoradiation for pT1-2N1M0 Head and Neck Cancer

Objective

To analyze the patterns of care and survival for pT1-2N1M0 head and neck cancer based on receipt of surgery alone, surgery + postoperative radiotherapy (S + RT), or surgery + postoperative chemoradiotherapy (S + CRT).

Study Design

Retrospective analysis.

Setting

National Cancer Database.

Subjects and Methods

We queried the database for patients with stage pT1-2N1M0 squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx between 2004 and 2012 who were treated with surgery with negative margins and no extracapsular extension. Logistic regression was used to assess predictors of receipt of postoperative treatment. Overall survival was assessed by the Kaplan-Meier method, and Cox regression analysis identified covariates that affected it.

Results

There were 1598 patients included in this study: 566 (35.4%) received surgery alone; 726 (45.4%), S + RT; and 306 (19.1%), S + CRT. The 5-year overall survival was 68.8%, 74.0%, and 87.8%, respectively ( P = .009 comparing S + RT and surgery alone, P < .001 for all other comparisons). On multivariable logistic regression, academic centers were associated with a decreased likelihood of S + RT (odds ratio = 0.71) and S + CRT (odds ratio = 0.66). Multivariable Cox regression demonstrated no difference in survival for S + RT over surgery alone (hazard ratio = 0.88, 95% CI = 0.70-1.09, P = .24); however, there was a survival benefit associated with S + CRT (hazard ratio = 0.57, 95% CI = 0.39-0.81, P = .002).

Conclusion

Nearly 65% of patients with pT1-2N1 head and neck cancer with negative margins and no extracapsular extension received S + RT or S + CRT. Improvement in survival was noted only for patients who received S + CRT.