Uncovering the armpit of SBRT: An institutional experience with stereotactic radiation of axillary metastases

Purpose/objectives

The growing use of stereotactic body radiotherapy (SBRT) in metastatic cancer has led to its use in varying anatomic locations. The objective of this study was to review our institutional SBRT experience for axillary metastases (AM), focusing on outcomes and process.

Materials/methods

Patients treated with SBRT to AM from 2014 to 2022 were reviewed. Cumulative incidence functions were used to estimate the incidence of local failure (LF), with death as competing risk. Kaplan-Meier method was used to estimate progression-free (PFS) and overall survival (OS). Univariate regression analysis examined predictors of LF.

Results

We analyzed 37 patients with 39 AM who received SBRT. Patients were predominantly female (60 %) and elderly (median age: 72). Median follow-up was 14.6 months. Common primary cancers included breast (43 %), skin (19 %), and lung (14 %). Treatment indication included oligoprogression (46 %), oligometastases (35 %) and symptomatic progression (19 %). A minority had prior overlapping radiation (18 %) or surgery (11 %). Most had prior systemic therapy (70 %).Significant heterogeneity in planning technique was identified; a minority of patient received 4-D CT scans (46 %), MR-simulation (21 %), or contrast (10 %). Median dose was 40 Gy (interquartile range (IQR): 35-40) in 5 fractions, (BED10 = 72 Gy). Seventeen cases (44 %) utilized a low-dose elective volume to cover remaining axilla.At first assessment, 87 % had partial or complete response, with a single progression. Of symptomatic patients (n = 14), 57 % had complete resolution and 21 % had improvement. One and 2-year LF rate were 16 % and 20 %, respectively. Univariable analysis showed increasing BED reduced risk of LF. Median OS was 21.0 months (95 % [Confidence Interval (CI)] 17.3-not reached) and median PFS was 7.0 months (95 % [CI] 4.3-11.3). Two grade 3 events were identified, and no grade 4/5.

Conclusion

Using SBRT for AM demonstrated low rates of toxicity and LF, and respectable symptom improvement. Variation in treatment delivery has prompted development of an institutional protocol to standardize technique and increase efficiency. Limited followup may limit detection of local failure and late toxicity.

Uncovering the Armpit of Axillary SBRT

PURPOSE/OBJECTIVE(S)

The growing use of stereotactic body radiotherapy (SBRT) in metastatic cancer has led to applications in new and unique anatomic locations, highlighting the importance of effective, safe, reproducible treatment delivery. The objective of this study was to review our institutional SBRT experience for axillary metastases (AM), focusing on outcomes, safety and process.

MATERIALS/METHODS

In this ethics approved single-institution retrospective review, patients treated with SBRT to AM from 2014-2022 had tumor, treatment planning, and dosimetric variables abstracted. Toxicity was assessed per Common Terminology for Adverse Events V5.0. Cumulative incidence functions were used to estimate the incidence of local failure (LF), with death as competing risk. Kaplan-Meier method was used to estimate progression-free (PFS) and overall survival (OS).

RESULTS

We analyzed 37 patients with 39 AM who received SBRT. Patients were predominantly female (60%), Eastern Cooperative Oncology Group performance status 0-1 (62%), and elderly (median age: 72), with a median follow-up of 14.6 months. Common primary sites included breast (n = 16, 43%), skin (n = 7, 19%), and lung (n = 5, 14%). Treatment indication included oligoprogression (n = 18, 46%), oligometastases (n = 14, 36%) and symptomatic progression (n = 7, 18%). A minority had prior overlapping radiation (n = 7, 18%) or regional surgery (n = 4, 11%), while most had prior systemic therapy (n = 26, 70%). Significant heterogeneity in simulation, planning and treatment was identified. Immobilization included 5-point thermoplastic mask (n = 12, 32%), Vacloc (n = 12, 32%) arms-up thorax bag (n = 11, 30%). 4-D CT scans were obtained in 46%, MR simulation in 21%, and intravenous contrast in 10%. Median dose was 40 Gy (interquartile range (IQR): 35-40) in 5 fractions, (BED10 = 72 Gy), over a median of 12 days (IQR: 9-14). Seventeen cases (44%) utilized a low-dose elective volume to cover remaining axilla; 14% used a high dose clinical target volume. Median planning target volume margin was 5mm (range: 3-10mm), and plans were generated with 5 different dose constraint protocols. At first radiographic assessment, 87% had partial or complete response, with a single progression. Of symptomatic patients (n = 14), 57% had complete symptom resolution and 21% had improvement. One and 2-year LF rate were 19% and 31%, respectively. Median OS was 21.0 months (95% [Confidence Interval (CI)] 17.3-not reached) and median PFS was 7.0 months (95% [CI] 4.3-11.3). Acute and late toxicities were uncommon, with two grade 3 events (1 plexopathy in a case with tumor involving brachial plexus, 1 skin ulceration) identified, and no grade 4/5.

CONCLUSION

In this series of AM SBRT, low rates of toxicity, and good rates of LF and symptom improvement were observed. As treatment was delivered with a variety of individual treatment differences, an institutional protocol is under development to standardize technique, optimize efficiency and improve evaluability.

All that Glitters is Not Gold: Examining Cost Effectiveness Analyses in Radiation Oncology

PURPOSE/OBJECTIVE(S)

Cost effectiveness analyses (CEA) provide data for health policy decisions in resource constrained environments. These are important in Radiation Oncology as infrastructure and delivery costs increase and indications expand. The purpose of this study was to systematically review methodologic quality and trends in CEAs involving radiotherapy (RT).

MATERIALS/METHODS

A systematic review was performed on cost effectiveness/utility studies involving RT, querying PubMed and Embase from inception to September 2020. Non-English, reviews, abstracts and cost-only studies were excluded. Independent reviewers screened and abstracted study demographics, economic parameters and methodological details.

RESULTS

After screening 1652 abstracts, 214 met criteria. The first publication was in 1995, and more than half (n = 113, 53%) were published after 2014. Author institutions were from North America (n = 128, 60%), Europe (n = 49, 23%) and Asia (n = 30, 14%) with most reporting in US$ (n = 143, 67%). A majority utilized a decision model (n = 164, 77%), healthcare payer perspective (n = 171, 80%) and a finite time horizon (n = 108, 50%). Publications spanned 96 unique journals, most commonly International Journal of Radiation and Oncological Biology and Physics (n = 35, 16%). Treatment intent was curative in 171 studies. Disease sites included breast (n = 34, 16%), genitourinary (n = 31, 14%), and gastrointestinal (n = 31, 14%). RT was mostly used as primary treatment (n = 144, 67%), followed by adjuvant (n = 70, 33%) and neoadjuvant (n = 10, 5%). Emerging topics included stereotactic RT (n = 45, 21%), immunotherapy (n = 6, 3%), oligometastasis (n = 4, 2%), and heavy particles (n = 23, 11%). RT was compared to other RT (n = 136, 64%), surgery (n = 43, 20%), drugs (n = 14, 7%) and observation (n = 31, 17%). Incomplete reporting was common. Missing elements included analysis perspective (n = 13, 6%), time horizon (n = 38, 18%), discounting of utilities (n = 71, 33%) or costs (n = 54, 25%), and willingness-to-pay threshold (n = 59, 28%). Furthermore, 27 studies did not perform sensitivity analyses, 36 did not evaluate incremental cost-effectiveness ratio and only 60 explicitly utilized recognized reporting guidelines. Conflict of interest statements were found in 63%, with sponsor statements in 59%; 25% were industry sponsors. Outcome parameters were obtained from primary (author institution/trial data) sources in 33%, including randomized trials (RCTs) (n = 20, 9%), retrospective data (n = 20, 9%) and population data (n = 9, 4%). The remainder utilized secondary sources including RCTs (n = 71, 33%), retrospective data (n = 35, 16%) or meta-analyses (n = 11, 5%). Outcomes included quality adjusted life years (n = 158, 74%), life-years (n = 30, 14%) or toxicity (n = 26,12%). 31% utilized author generated utilities; of literature derived only 49% were matched to disease and clinical context.

CONCLUSION

While CEAs are increasingly common in RT, reporting and methodologic rigor must improve. Greater use of published guidelines will improve data quality for decision makers.

Heatmaps to Assess Tumor Motion Probability with MRcine in Head and Neck Cancer

PURPOSE/OBJECTIVE(S)

Intrafraction motion affects tumor position during radiation for head and neck cancers (HNC) and can be assessed using magnetic resonance cine (MR-cine). Heatmaps - visual representation of patient specific temporal tumor location akin to internal target volume (ITV) - were analyzed to demonstrate the variation of population-based motion margins in primary oropharyngeal (OP) and laryngeal/hypopharyngeal (LH) sites with the goal to provide insights towards personalized margins.

MATERIALS/METHODS

MR-cine were performed for LH and OP HNC patients as part of simulation protocol. Images (900-1500 slices) were acquired across 3-5 minutes per patient. Gross target volumes were propagated on T1 contrast sagittal sequence using deformable image registration then adjusted manually. Tumor locations were integrated across all frames and displayed as heatmaps representing location probability. To determine individualized motion, a baseline contour representing average tumor rest position was expanded both isotropically and directionally in 1 mm increments in a novel analysis to define the contribution of each increment on target coverage. To assess directional dependence, displacements from rest position were evaluated in 4 planes from centroid: (A) 12 o'clock (OC) to 6OC (capturing volumetric shift in a portion of superior, posterior and inferior directions), B) 3OC-9OC, C) 6OC-12OC, D) 9OC-3OC. Histograms demonstrating the proportion of scan time the tumor was within expansions were generated, with expansion margins for 25%-95% coverage analyzed by patient. Wilcoxon-rank-sum test was performed to compare motion by site.

RESULTS

Motion was evaluated in 66 patients (LH n = 27, OP n = 39). In LH, a median (med) isometric expansion of 8.5mm to achieve 95% target was required, with large variations observed for minimum (min): 2.8mm and maximum (max):23.5mm. Smaller differences were observed for OP with med of 5.3mm, (min:1.9mm, max:14.6mm). At 75%, 50% and 25% coverage, expansions for LH (med: 4.8 min: 1.9 max: 17.3; med: 3.8 min: 1.2 max: 12.9; med: 3.3, min: 0.6, max: 9.3) were not significantly different than OP (med: 3.8, min: 1.7, max: 10.9; med: 3.1 min: 1.3, max: 9.4; med: 2.1, min: 0.7, max: 8.4), suggesting larger but infrequent shifts in LH. Directional tumor displacement varied widely (Table 1), and by site and points describing the need for personalized margins.

CONCLUSION

Current literature as well as the analysis in this study indicate a wide range of motion - both in magnitude and duty cycle - between and within HN sub-sites not captured on CT simulation. Moving forward, motion based heatmaps based on MR-cine may serve as visualization tool for ITV contouring or to generate personalized motion margins.

Surgeon, Pathologist and Pathology Technician Effects on Nodal Yield after a Neck Dissection

PURPOSE/OBJECTIVE(S)

A minimum nodal count of 18 lymph nodes has been associated with improved survival after neck dissection and has been suggested as a head and neck cancer quality metric. Despite its critical importance, factors affecting nodal yield are poorly studied. In particular, the relative contribution of surgeons, pathologists, and pathology technicians has not been evaluated. The purpose of this study was to understand both patient and provider related factors that affect nodal yield after neck dissection for patients with oral cavity squamous cell carcinoma (OCSCC).

MATERIALS/METHODS

This retrospective cohort study involved review of all adult patients with OCSCC undergoing primary neck dissection between 2000-2020 at an academic medical center. The outcome of interest was a continuous variable denoting the number of nodes removed per side during neck surgery. Surgeon and pathologist year of experience were calculated and represented in quartiles. A multilevel multivariable linear regression model was used to assess the association of surgeon/pathologist experience quartiles with nodal yield, controlling for patient age, comorbidity index, previous cancer, tumor grade, and clinical nodal status.

RESULTS

The 508 patients included in our cohort were treated by 5 surgeons and 6 pathologists and involved 44 pathology technicians. Of these patients, 310 (61.0%) were male with a mean age of 63. Oral tongue primary tumors were 46.7% of the cohort, while 64.4% of patients had cT1-T2 tumors, and 65.2% were cN0. The mean nodal yield was 24.2 nodes. The ANOVA analysis revealed significant difference in mean nodal yield by surgeon (p-value = 0.03), pathologist (p-value<0.01) and pathology technician (p-value = 0.037). After accounting for patient-level characteristics and patient clustering by surgeon, increasing surgeon experience was found to be significantly associated with a higher nodal yield (joint significance of surgeon years of experience quartiles < 0.01). Specifically, when compared to surgeons with the least experience (1st quartile), those whose years of experience fell into the 2nd, 3rd, and 4th quartile removed 4.69 (95% CI: 0.97 to 7.92), 4.47 (95% CI: 0.33 to 7.87), and 7.37 (95% CI: 0.73 to 11.27) more lymph nodes. Meanwhile, there was no association between pathologist experience and nodal yield (joint significance of pathologist years of experience quartiles = 0.27). Additionally, previous cancer diagnosis and cN0 disease were significantly associated with lower nodal yield (all p-values = 0.02).

CONCLUSION

This study demonstrates an independent association between increasing surgeon experience and higher nodal yields. Importantly, it also demonstrates that pathologists and pathology technicians contribute to the variation in nodal yield, and their contribution should not be overlooked in the implementation of a lymph node yield-based quality metric.

Evaluating the Oncology Research Internship (ORIoN) during the COVID-19 Pandemic: A Comparison of Virtual and In-Person Iterations

Purpose/Objective(s)

The Oncology Research Internship (ORIoN), a novel resident-supervised initiative for medical students (MS), was first established in 2018 and found to be mutually beneficial to both residents and MS. The COVID-19 pandemic halted many scholarly programs, including ORIoN, which relied heavily on mentorship through in-person interactions. We report results of the first virtual program, adapted to the COVID-19 pandemic, and compare participant feedback to previous in-person iterations.

Materials/Methods

ORIoN application details were published online and emailed to first- and second-year MS. A panel of 3 physicians reviewed and scored applications independently. Successful MS applicants were paired with volunteer resident supervisors; each pair supervised by a staff oncologist. Compared to previous years, all meetings, correspondences and presentations between MS, residents, and supervising oncologists were conducted exclusively remotely. Only chart reviews were conducted on-site by MS. At the program's conclusion, each MS delivered a live virtual oral presentation of their completed case report, previously done in-person. Resident and MS participants completed questionnaires pre-/post program. Responses were collected on a 5-point Likert scale with open-ended free-text responses. Survey results from this virtual and the previous in-person programs were compared.

Results

Of 54 applications (previously 32 in 2018), 9 MS (three first-year, six second-year) were accepted and assigned to 9 volunteer residents (6 radiation oncology, 2 medical oncology, 1 pathology). To date, 9 manuscripts have been completed with 2 submitted for publication (1 published, 1 under review). Survey response rates were 100% (9/9) for residents and 89% (8/9) for MS. In the post-program surveys comparing the virtual and prior in-person programs, 87.5% (7/8) MS felt comfortable completing a clinical research project (22% strongly agree (SA), 62.5% agree (A), previously 25% and 75% respectively) and 100% (8/8) felt comfortable writing a case report (50% SA, 50% A, previously 75%, 25% respectively). All MS felt comfortable giving an oral research presentation (37.5% SA, 62.5% A) and teaching another MS to complete a case report (37.5% SA, 50% A). Similar to the in-person program, MS unanimously agreed that ORIoN was a beneficial experience (100%) and felt the program contributed to their career goals (100%, previously 88%). Post-program, all residents felt comfortable as a supervisor (67% SA, 22% A, previously 33%, 67% respectively), reviewing manuscripts (56% SA, 33% A, previously 33%, 50% respectively) and providing constructive feedback to trainees (67% SA, 33% A, previously 17%, 67% respectively).

Conclusion

Compared to the previous in-person program, the virtual ORIoN retained strongly favorable ratings from MS and residents alike. These findings support adapting similar scholarly and mentorship programs to a virtual setting when in-person interactions are not feasible.