2021 AAPM Equity, Diversity, and Inclusion Climate Survey Executive Summary.

PURPOSE: The American Association of Physicists in Medicine (AAPM) shares the results, conclusions, and recommendations from the initial Equity, Diversity, and Inclusion Climate Survey conducted in 2021. METHODS AND MATERIALS: The climate survey targeted medical physicists who are full members of the AAPM and included demographic inquiries and questions intended to assess the working environmental climate in terms of a sense of belonging and inclusion, experiences of discrimination and harassment, and obstacles to participation within the AAPM. The survey invitation was sent to 5,500 members. Responses were collected from 1385 members (response rate of 25%) between January and February 2021. RESULTS: Overall, the medical physics workplace climate was positive. However, some demographic and professional subgroups reported lower levels of agreement with positive characteristics of their workplace climates. Compared with men, women ranked lower 7 of 8 categories that characterized the workplace climate. Other subgroups that also ranked the workplace climate descriptors lower included individuals not originally from the United States and Canada (3/8). Most respondents strongly agreed/agreed that the climate within the AAPM was welcoming. However, 17% of respondents reported personally experiencing or witnessing microaggressions within the AAPM. Overall, medical physicists reported low levels of agreement that opportunities within the AAPM were available to them, from 34% to 60% among 8 categories, including opportunities to volunteer, join committees, and compete for leadership positions within the AAPM. Several subgroups reported even lower levels of agreement that these opportunities are available. Asian and Asian American respondents (3/8) and physicists with origins in countries outside the United States and Canada (7/8) reported fewer opportunities to participate in the AAPM. Medical physicists reported their experiences of discrimination and sexual harassment in their workplaces and within the AAPM. For those who reported personal experiences of sexual harassment, only 24% (15/63) felt comfortable reporting when it occurred within their workplaces, and 35% (9/26) felt comfortable reporting when it occurred within the AAPM. CONCLUSIONS: The report concludes with several recommendations for action.

Dosimetric and radiobiologic comparison of 103Pd COMS plaque brachytherapy and Gamma Knife radiosurgery for choroidal melanoma.

PURPOSE: Plaque brachytherapy (BT) and Gamma Knife radiosurgery (GKRS) are highly conformal treatment options for choroidal melanoma. This study objectively compares physical dose and biologically effective dose (BED) distributions for these two modalities. METHODS AND MATERIALS: Tumor and organ-at-risk (OAR) dose distributions from a CT-defined reference right eye were compared between 103Pd COMS (Collaborative Ocular Melanoma Study Group) plaques delivering 70 Gy (plaque heterogeneity corrected) over 120 h to the tumor apex and GKRS plans delivering 22 Gy to the 40% isodose line for a representative sample of clinically relevant choroidal melanoma locations and sizes. Tumor and OAR biologically effective dose-volume histograms were generated using consensus radiobiologic parameters and modality-specific BED equations. RESULTS: Published institutional prescriptive practices generally lead to larger tumor and OAR physical doses from COMS BT vs. GKRS. Radiobiologic dose conversions, however, revealed variable BEDs. Medium and large tumors receive >1.3 times higher BEDs with COMS BT vs. GKRS. OAR BEDs have even greater dependence on tumor size, location, and treatment modality. For example, COMS BT maximum BEDs to the optic nerve are lower than from GKRS for large anterior and all posterior tumors but are higher for anterior small and medium tumors. CONCLUSIONS: BT and GKRS for choroidal melanoma have different physical dose and BED distributions with potentially unique clinical consequences. Using published institutional prescriptive practices, neither modality is uniformly favored, although COMS BT delivers higher physical doses and BEDs to tumors. These results suggest that lowering the physical prescription dose for COMS BT to more closely match the BED of GKRS might maintain equivalent tumor control with less potential morbidity.

Brachytherapy vs. external beam radiotherapy for choroidal melanoma: Survival and patterns-of-care analyses.

PURPOSE: No modern randomized trials exist comparing external beam radiotherapy (EBRT) and plaque brachytherapy (BT) for choroidal melanoma, and the optimal treatment modality is currently unknown. This study compares the patterns of care and efficacy of EBRT vs. BT based on data in the Surveillance, Epidemiology, and End Results database. METHODS AND MATERIALS: The Surveillance, Epidemiology, and End Results database was queried for patients aged 20-79 diagnosed with choroidal melanoma from 2004 to 2011, treated with EBRT or BT; included patients were clinically T1-T4, N0, and M0. Overall survival and cause-specific survival curves were calculated by the Kaplan-Meier method. Univariate and multivariate analyses were performed in the survival and patterns-of-care analyses. RESULTS: A total of 1004 cases (380 EBRT and 624 BT) were included in the survival analysis. There was no difference in the 5-year overall survival (83.3% EBRT vs. 82.5% BT, p = 0.69) and 5-year cause-specific survival (88.3% EBRT vs. 88.3% BT, p = 0.92). In the survival analysis, older age and advanced tumor stage were predictors of increased risk of death. In the patterns-of-care analysis, later year of diagnosis and smaller tumor stage were predictors of BT use. CONCLUSIONS: Advanced tumor stage and older age seem to be independent predictors for risk of death from choroidal melanoma. The use of BT favors smaller tumors and later year of diagnosis. There is no difference in survival between those treated with EBRT or BT, and the utilization of BT is increasing.

COMS eye plaque brachytherapy dosimetric sensitivity to source photon energy and seed design.

This study explores the influence of source photon energy on eye plaque brachytherapy dose distributions for a 16 mm COMS plaque filled with (103)Pd, (125)I, or (131)Cs sources or monoenergetic photon emissions ranging from 12 keV to 100 keV. Dose distributions were similarly created for all permutations of three common brachytherapy seed designs. Within this range, sources with average energy ≤22 keV may reduce dose to the opposite eye wall by more than a factor of 2 while maintaining tolerable proximal sclera doses when prescribing to depths of 9 mm or less. Current commercially-available brachytherapy sources can exhibit up to 15% relative dosimetric sensitivity to seed design at regions within the eye.

Quantifying the dosimetric influences of radiation coverage and brachytherapy implant placement uncertainty on eye plaque size selection.

PURPOSE: Quantify the dosimetric adequacy of the 2003 American Brachytherapy Society report tumor margin recommendations for Collaborative Ocular Melanoma Study (COMS) eye plaque size selection for radiation coverage and clinical plaque placement uncertainties. METHODS AND MATERIALS: Plaque heterogeneity-corrected dose distributions were generated for the range of available COMS plaque diameters (φplaque) and radionuclides. These dose distributions were used to determine the radiation dose distribution diameter (φ℞) at the eye surface for each plaque as a function of central axis prescription depth (d℞) to assess adequacy of a 2-3-mm margin for various gross tumor volume (GTV) basal diameters (φGTV). Four sets of ellipsoidal tumors (φGTV=5, 8, 11, and 14mm) with a range of apical heights (dGTV=2-8mm) were contoured in a reference CT environment. Plaque placement uncertainties were quantified as circumferential displacements (Δ) at the outer scleral surface. Tumor dose-volume histograms were generated and compared for all Δ with D90 and D95 used to evaluate tumor margin adequacy. RESULTS: For equivalent φplaque and prescription depths, φ℞ values were typically 0.4-0.8mm less for (103)Pd than for (125)I or (131)Cs. Δ≤3mm resulted in D90 and D95 values as low as 68% and 64% of the prescription dose, respectively. (103)Pd plaque dose distributions were more sensitive than (125)I or (131)Cs to placement uncertainties. CONCLUSIONS: The American Brachytherapy Society-recommended tumor margin may be inadequate for prescription dose coverage given COMS plaque radiation characteristics and placement uncertainties. Better coverage is achieved assuming a GTV-to-planning target volume total basal expansion of 3mm or greater and/or prescribing beyond the tumor apex.

Radiobiology for eye plaque brachytherapy and evaluation of implant duration and radionuclide choice using an objective function.

PURPOSE: Clinical optimization of Collaborative Ocular Melanoma Study (COMS) eye plaque brachytherapy is currently limited to tumor coverage, consensus prescription dosage, and dose calculations to ocular structures. The biologically effective dose (BED) of temporary brachytherapy treatments is a function of both chosen radionuclide R and implant duration T. This study endeavored to evaluate BED delivered to the tumor volume and surrounding ocular structures as a function of plaque position P, prescription dose, R, and T. METHODS: Plaque-heterogeneity-corrected dose distributions were generated with MCNP5 for the range of currently available COMS plaques loaded with sources using three available low-energy radionuclides. These physical dose distributions were imported into the PINNACLE(3) treatment planning system using the TG-43 hybrid technique and used to generate dose volume histograms for a T = 7 day implant within a reference eye geometry including the ciliary body, cornea, eyelid, foveola, lacrimal gland, lens, optic disc, optic nerve, retina, and tumor at eight standard treatment positions. The equation of Dale and Jones was employed to create biologically effective dose volume histograms (BEDVHs), allowing for BED volumetric analysis of all ROIs. Isobiologically effective prescription doses were calculated for T = 5 days down to 0.01 days, with BEDVHs subsequently generated for all ROIs using correspondingly reduced prescription doses. Objective functions were created to evaluate the BEDVHs as a function of R and T. These objective functions are mathematically accessible and sufficiently general to be applied to temporary or permanent brachytherapy implants for a variety of disease sites. RESULTS: Reducing T from 7 to 0.01 days for a 10 mm plaque produced an average BED benefit of 26%, 20%, and 17% for (103)Pd, (125)I, and (131)Cs, respectively, for all P; 16 and 22 mm plaque results were more position-dependent. (103)Pd produced a 16%-35% BED benefit over (125)I, whereas (131)Cs produced a 3%-7% BED detriment, independent of P, T, and plaque size. Additionally, corresponding organ at risk physical doses were lowest using (103)Pd in all circumstances. CONCLUSIONS: The results suggest that shorter implant durations may correlate with more favorable outcomes compared to 7 day implants when treating small or medium intraocular lesions. The data also indicate that implant duration may be safely reduced if the prescription physical dose is likewise diminished and that (103)Pd offers a substantial radiobiological benefit over (125)I and (131)Cs irrespective of plaque position, implant duration, and tumor size.

BEDVH-A method for evaluating biologically effective dose volume histograms: application to eye plaque brachytherapy implants.

PURPOSE: A method is introduced to examine the influence of implant duration T, radionuclide, and radiobiological parameters on the biologically effective dose (BED) throughout the entire volume of regions of interest for episcleral brachytherapy using available radionuclides. This method is employed to evaluate a particular eye plaque brachytherapy implant in a radiobiological context. METHODS: A reference eye geometry and 16 mm COMS eye plaque loaded with (103)Pd, (125)I, or (131)Cs sources were examined with dose distributions accounting for plaque heterogeneities. For a standardized 7 day implant, doses to 90% of the tumor volume ( (TUMOR)D(90)) and 10% of the organ at risk volumes ( (OAR)D(10)) were calculated. The BED equation from Dale and Jones and published α/ß and µ parameters were incorporated with dose volume histograms (DVHs) for various T values such as T = 7 days (i.e., (TUMOR) (7)BED(10) and (OAR) (7)BED(10)). By calculating BED throughout the volumes, biologically effective dose volume histograms (BEDVHs) were developed for tumor and OARs. Influence of T, radionuclide choice, and radiobiological parameters on (TUMOR)BEDVH and (OAR)BEDVH were examined. The nominal dose was scaled for shorter implants to achieve biological equivalence. RESULTS: (TUMOR)D(90) values were 102, 112, and 110 Gy for (103)Pd, (125)I, and (131)Cs, respectively. Corresponding (TUMOR) (7)BED(10) values were 124, 140, and 138 Gy, respectively. As T decreased from 7 to 0.01 days, the isobiologically effective prescription dose decreased by a factor of three. As expected, (TUMOR) (7)BEDVH did not significantly change as a function of radionuclide half-life but varied by 10% due to radionuclide dose distribution. Variations in reported radiobiological parameters caused (TUMOR) (7)BED(10) to deviate by up to 46%. Over the range of (OAR)α/ß values, (OAR) (7)BED(10) varied by up to 41%, 3.1%, and 1.4% for the lens, optic nerve, and lacrimal gland, respectively. CONCLUSIONS: BEDVH permits evaluation of the relative biological effectiveness for brachytherapy implants. For eye plaques, (TUMOR)BEDVH and (OAR)BEDVH were sensitive to implant duration, which may be manipulated to affect outcomes.

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity.

PURPOSE: To improve tumor dose conformity and homogeneity for COMS plaque brachytherapy by investigating the dosimetric effects of varying component source ring radionuclides and source strengths. MATERIAL AND METHODS: The MCNP5 Monte Carlo (MC) radiation transport code was used to simulate plaque heterogeneity-corrected dose distributions for individually-activated source rings of 14, 16 and 18 mm diameter COMS plaques, populated with (103)Pd, (125)I and (131)Cs sources. Ellipsoidal tumors were contoured for each plaque size and MATLAB programming was developed to generate tumor dose distributions for all possible ring weighting and radionuclide permutations for a given plaque size and source strength resolution, assuming a 75 Gy apical prescription dose. These dose distributions were analyzed for conformity and homogeneity and compared to reference dose distributions from uniformly-loaded (125)I plaques. The most conformal and homogeneous dose distributions were reproduced within a reference eye environment to assess organ-at-risk (OAR) doses in the Pinnacle(3) treatment planning system (TPS). The gamma-index analysis method was used to quantitatively compare MC and TPS-generated dose distributions. RESULTS: Concentrating > 97% of the total source strength in a single or pair of central (103)Pd seeds produced the most conformal dose distributions, with tumor basal doses a factor of 2-3 higher and OAR doses a factor of 2-3 lower than those of corresponding uniformly-loaded (125)I plaques. Concentrating 82-86% of the total source strength in peripherally-loaded (131)Cs seeds produced the most homogeneous dose distributions, with tumor basal doses 17-25% lower and OAR doses typically 20% higher than those of corresponding uniformly-loaded (125)I plaques. Gamma-index analysis found > 99% agreement between MC and TPS dose distributions. CONCLUSIONS: A method was developed to select intra-plaque ring radionuclide compositions and source strengths to deliver more conformal and homogeneous tumor dose distributions than uniformly-loaded (125)I plaques. This method may support coordinated investigations of an appropriate clinical target for eye plaque brachytherapy.

A 17-year retrospective study of institutional results for eye plaque brachytherapy of uveal melanoma using (125)I, (103)Pd, and (131)Cs and historical perspective.

PURPOSE: To compare overall survival, local and distant failure rates, ocular toxicity, and vision preservation in patients treated with eye plaque brachytherapy at Tufts Medical Center with those in the published literature. METHODS AND MATERIALS: Records were reviewed for 53 patients with the diagnosis of uveal melanoma treated with plaque brachytherapy at Tufts Medical Center over the past 17 years. American Joint Committee on Cancer staging (T1, T2, or T3) were 4, 39, and 10 patients, respectively. All the patients were treated using (125)I (n=37), (103)Pd (n=5), or (131)Cs (n=11) to a dose of 85Gy (documented as 100Gy before 1996 for the same physical dose). RESULTS: With a mean followup of 75 months, 38 of 53 patients were still alive. Five patients (all (125)I) developed liver metastases (9%) with no evidence of local failure. There were 10 definitive local failures and four additional transpupillary thermo-therapy procedures performed to ensure local control for lesions slow to respond. Twelve patients (23%) required enucleation. At most recent followup, 32 patients (71%) maintained 20/200 vision or better in the treated eye. In this first report of (131)Cs plaque therapy with a mean followup of 20 months, there were two transpupillary thermo-therapy procedures and one definitive failure requiring enucleation after 10 months. CONCLUSIONS: Our disease control and ocular results were comparable to those in the literature given the extended followup. We are developing a multi-institutional, prospective clinical protocol for considering radionuclide selection and other prescriptive criteria.