Equity, Diversity, and Inclusion in Radiation Oncology: A Bibliometric Analysis and Critical Review

The promotion of equity, diversity, and inclusion (EDI) is being increasingly pursued in health care, both in general and within radiation oncology. Because bibliometrics is a powerful tool to reveal the scientific literature on a specific topic during a certain timespan, a systematic bibliometric analysis of the documents published on EDI in radiation oncology was performed, aiming at exploring common patterns in research and emerging trends, tracking collaborations and networks, and anticipating future directions in clinical research. Standard descriptive statistics and bibliometric techniques were used in the analysis. A collaboration network and thematic map were generated from the data. Four domains were represented: (1) motor themes, including themes well developed and important for the structuring of the research field; (2) niche themes, representing the isolated topics that do not share important external links with other themes; (3) emerging themes, referring to still weakly developed topics; and (4) basic themes, including the essential topics. EDI in the profession of radiation oncology is essential to ensure that the workforce delivering radiation oncology care both draws from the full talent pool of human capital and delivers the highest quality science and clinical care to all patients. The burgeoning literature on EDI in radiation oncology suggests that a large and growing cohort of scholars within radiation oncology are dedicated to addressing these important challenges.

Breast cancer radiation therapy: A bibliometric analysis of the scientific literature

Background and purpose

Breast cancer is the most common malignancy in women and radiation therapy (RT) is crucial in its multimodality management. Since bibliometrics is a powerful tool to reveal the scientific literature, we decided to perform a bibliometric analysis of the literature on breast cancer radiotherapy. We explored emerging trends and common patterns in research, tracking collaboration and networks, and foreseeing future directions in this clinical setting.

Material and methods

The electronic Scopus database was searched using the keywords "breast cancer" and "radiotherapy" to include manuscripts published in English, between 2000 and 2021. Data analysis was performed using R-Studio 0.98.1091 software with a machine-learning bibliometric method, based on the bibliometrix R package. The most relevant authors were quantified per number and fractionalized number of authored documents. Author productivity was analysed through Lotka's law. Bradford's law was applied to identify the nucleus of journals focused on the addressed topic. Mainstream themes area included isolated topics (niche themes), new topics (emerging themes), hot topics (motor themes) and essential topics (basic themes).

Results

A total of 27 184 documents was found, mainly original articles (76 %). The annual growth rate was 6.98 %, with an increase in scientific production from 485 to 2000 documents between 2000 and 2021. Overall, 2 544 journals published ≥ 1 documents. The most relevant authors were affiliated in the United States. Surgical procedures, cancer type and treatment strategies represented basic themes, while primary systemic therapy and sentinel lymph node biopsy were emerging themes. Health-related quality of life was a niche theme, while RT techniques had high centrality.

Conclusion

The primary interests of breast cancer radiation oncologists have evolved over time, adding safety, health related quality of life, sustainability of treatments and combination to systemic therapies to radiotherapy efficacy and effectiveness and treatment outcomes.

Re-irradiation for intra-thoracic tumours and extra-thoracic breast cancer: dose accumulation, evaluation of efficacy and toxicity based on a literature review

The improvement seen in the diagnostic procedures and treatment of thoracic tumours means that patients have an increased chance of longer overall survival. Nevertheless, we can still find those who have had a recurrence or developed a secondary cancer in the previously treated area. These patients require retreatment including re-irradiation. We have reviewed the published data on thoracic re-irradiation, which shows that some specific healthy tissues can tolerate a significant dose of irradiation and these patients benefit from aggressive treatment; however, there is a risk of damage to normal tissue under these circumstances. We analysed the literature data on re-irradiation in the areas of vertebral bodies, spinal cord, breast, lung and oesophagus. We evaluated the doses of primary and secondary radiotherapy, the treatment techniques, as well as the local control and median or overall survival in patients treated with re-radiation. The longest OS is reported in the case of re-irradiation after second breast-conserving therapy where the 5-year OS range is 81 to 100% and is shorter in patients with loco-reginal re-irradiation where the 5-y OS range is 18 to 60%. 2-year OS in patients re-irradiated for lung cancer and oesophagus cancer range from 13 to 74% and 18 to 42%, respectively. Majority grade ≥3 toxicity after second breast-conserving therapy was fibrosis up to 35%. For loco-regional breast cancer recurrences, early toxicity occurred in up to 33% of patients resulting in mostly desquamation, while late toxicity was recorded in up to 23% of patients and were mostly ulcerations. Early grade ≥3 lung toxicity developed in up to 39% of patients and up to 20% of Grade 5 hemoptysis. The most frequently observed early toxicity grade ≥3 in oesophageal cancer was oesophagitis recorded in up to 57% of patients, followed by hematological complications which was recorded in up to 50% of patients. The most common late complications included dysphagia, recorded in up to 16.7% of patients. We have shown that thoracic re-irradiation is feasible and effective in achieving local control in some patients. Re-irradiation should be performed with maximum accuracy and care using the best available treatment methods with a highly conformal, image-guided approach. Due to tremendous technological progress in the field of radiotherapy, we can deliver radiation precisely, shorten the overall treatment time and potentially reduce treatment-related toxicities.

ESTRO ACROP consensus guideline for target volume delineation in the setting of postmastectomy radiation therapy after implant-based immediate reconstruction for early stage breast cancer

Immediate breast reconstruction (IBR) rates after mastectomy are increasing. Postmastectomy radiation therapy (PMRT) contouring guidelines for target volumes in the setting of IBR are lacking. Therefore, many patients who have had IBR receive PMRT to target volumes similar to conventional simulator-based whole breast irradiation. The aim of this paper is to describe delineation guidelines for PMRT after implant-based IBR based on a thorough understanding of the surgical procedures, disease stage, patterns of recurrence and radiation techniques. They are based on a consensus endorsed by a global multidisciplinary group of breast cancer experts.

Long-term effects of low-dose mouse liver irradiation involve ultrastructural and biochemical changes in hepatocytes that depend on lipid metabolism

The aim of the study was to investigate long-term effects of radiation on the (ultra)structure and function of the liver in mice. The experiments were conducted on wild-type C57BL/6J and apolipoprotein E knock-out (ApoE^-/-) male mice which received a single dose (2 or 8 Gy) of X-rays to the heart with simultaneous exposure of liver to low doses (no more than 30 and 120 mGy, respectively). Livers were collected for analysis 60 weeks after irradiation and used for morphological, ultrastructural, and biochemical studies. The results show increased damage to mitochondrial ultrastructure and lipid deposition in hepatocytes of irradiated animals as compared to non-irradiated controls. Stronger radiation-related effects were noted in ApoE^-/- mice than wild-type animals. In contrast, radiation-related changes in the activity of lysosomal hydrolases, including acid phosphatase, β-glucuronidase, N-acetyl-β-D-hexosaminidase, β-galactosidase, and α-glucosidase, were observed in wild type but not in ApoE-deficient mice, which together with ultrastructural picture suggests a higher activity of autophagy in ApoE-proficient animals. Irradiation caused a reduction of plasma markers of liver damage in wild-type mice, while an increased level of hepatic lipase was observed in plasma of ApoE-deficient mice, which collectively indicates a higher resistance of hepatocytes from ApoE-proficient animals to radiation-mediated damage. In conclusion, liver dysfunctions were observed as late effects of irradiation with an apparent association with malfunction of lipid metabolism.

Changes in activity and structure of lysosomes from liver of mouse irradiated in vivo

PURPOSE

Lysosomes may have an important role in response to ionizing radiation. Moreover, radiation could affect autophagy, which process involves the activity of lysosomal enzymes. In the present study, the effect of ionizing radiation on the lysosomal compartment of mouse liver was investigated after in vivo exposure.

MATERIALS AND METHODS

Morphology and ultrastructure of hepatocytes were assessed by light and electron microscopy, and activities of selected lysosomal enzymes were assessed in 12, 36 and 120 h after exposure to the mean dose of 1 Gy. The levels of autophagy-related proteins LC3-II and p62 were compared by Western blotting between untreated and irradiated animals (120 h after exposure).

RESULTS

Increased number of autophagic vacuoles in hepatocytes from exposed animals was documented in the ultrastructural study; destroyed mitochondria were the dominant component of such vacuoles. Moreover, an increased activity of lysosomal hydrolases was observed after exposure. However, levels of autophagy substrates LC3-II and p62 were barely affected in exposed animals 120 h after irradiation when the accumulation of autophagic vacuoles was observed.

CONCLUSION

Effects of irradiation included an increased number of autophagic vacuoles, especially of autophagosomes, and increased activity of lysosomal enzymes. However, putative markers of autophagic flux were not observed, which suggested suppression of the completion of the radiation-mediated autophagy pathway.

ESTRO consensus guideline on target volume delineation for elective radiation therapy of early stage breast cancer

BACKGROUND AND PURPOSE

Delineation of clinical target volumes (CTVs) is a weak link in radiation therapy (RT), and large inter-observer variation is seen in breast cancer patients. Several guidelines have been proposed, but most result in larger CTVs than based on conventional simulator-based RT. The aim was to develop a delineation guideline obtained by consensus between a broad European group of radiation oncologists.

MATERIAL AND METHODS

During ESTRO teaching courses on breast cancer, teachers sought consensus on delineation of CTV through dialogue based on cases. One teacher delineated CTV on CT scans of 2 patients, followed by discussion and adaptation of the delineation. The consensus established between teachers was sent to other teams working in the same field, both locally and on a national level, for their input. This was followed by developing a broad consensus based on discussions.

RESULTS

Borders of the CTV encompassing a 5mm margin around the large veins, running through the regional lymph node levels were agreed, and for the breast/thoracic wall other vessels were pointed out to guide delineation, with comments on margins for patients with advanced breast cancer.

CONCLUSION

The ESTRO consensus on CTV for elective RT of breast cancer, endorsed by a broad base of the radiation oncology community, is presented to improve consistency.

Prone versus supine breast irradiation in early stage breast cancer patients

Abstract #5130

Introduction
 External beam radiotherapy for breast cancer patients is necessary after breast conserving therapy. Volume of breast tissue which needs to be irradiated is close to critical structures such as lung, heart; therefore an alternative prone position could be used to improve dose homogeneity during radiotherapy. The purpose of this study was to compare dose distribution within target and normal tissue volumes between two radiotherapy plans in prone and supine position in women with large and also with small breasts.
 Material and methods
 36 early breast cancer patients (15 – right side and 21 left side, 7 – small, 9 - median, and 20 – large breast size) in clinical stage T1-2N0 were treated with breast conserving therapy and were dedicated for further radiotherapy. Planning CT was performed in a prone and supine position and two treatment plans for each patient were developed using conventional tangents technique. Dose volume histograms were produced and plans were compared with regard to dose volumes parameters. Comparison of the different techniques was statistically analyzed using the Wilcoxon signed rank test.
 Results
 The mean doses to the target volume were (50.9 Gy ± 0.59 for supine position and 50.3 Gy ± 0.81 for prone position, p=0.005), minimum dose (39.9 Gy ± 3.7 vs. 38.7 Gy ± 7.7, p=0.6) and maximum dose (54.9 Gy ± 0.5 vs. 54.4 Gy ± 0.9, p=0.02), the dose in 95 % of PTV was significantly higher in supine compare to prone position (48.0 Gy ± 1.3 vs. 46.7 Gy ± 1.8, p=0.0002). The percentage of ipsilateral lung receiving specified dose were significantly higher in supine position compare to prone position: V5 Gy was 26.8% ± 9.5 for supine position and 7.7% ± 6.4 for prone position (p<0.0001), V10 Gy was 18% ± 7.9 vs. 4.8% ± 4.6 (p<0.0001) and V20 Gy was 12.1 ± 4.9 vs. 2.7% ± 2.8 (p=0.0001). Furthermore, the maximum and mean dose to the ipsilateral lung and heart was lower in prone position (max/mean lung 44.4/2.2 Gy, max/mean heart 27.9/2.4 Gy) compare to supine position (max/mean lung 51.4/7.8 Gy, max/mean heart 30.8/3.4 Gy).
 In the last part we precisely evaluated dose to the heart in left side breast patients. In this case there was significant decrease in maximum, mean and dose to the heart in prone position (max/mean heart 42.9/3.3 Gy, for prone position and max/mean heart 48.1/5 Gy for supine position). There was also smaller heart volume which received 5 Gy (10% ± 5.7 vs. 15.5 ± 11.1). Decrease in dose to the organ at risk was seen not only in large breast size patients but also in patients with smaller breasts.
 Conclusion
 Irradiation of patients in prone positions compare to supine positions did not improved dose distribution within target volume. Using plans generated in prone position we were able to reduce the dose to the organ at risk especially ipsilateral lung and heart.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5130.

Differences in outcome of young breast cancer patients according to BRCA1 mutation status

Abstract #1044

Introduction
 5 to 10 % of all breast cancer and 25 % of early onset breast cancer are inheritable, which may be caused by mutations of tumour suppressor genes such as BRCA1. Moreover, the issue of a familial breast cancer has raised much attention in recent years due to numerous medical and social implications. In the present paper we investigate the clinical characteristic and outcomes of younger (<50 years old) breast cancer patients with BRCA1 mutation in comparison to patients without this germline mutation.
 Methods and Materials
 This is an ongoing study and patients will be enrolled till end of 2008. Till now we followed 495 breast cancer patients who were diagnosed before age 50 and were asked to provide a blood sample for BRCA1 mutation screening. We compared contralateral breast cancer and ovarian cancer incidence, disease free, metastases free, and overall survival, between BRCA1 mutation carriers and non-carriers.
 Results
 BRCA1 mutations were detected in 90 breast cancer patients (5382insC in 60 patients, 300T/G in 18 pts, 185delAG in 10 pts, and 4153delAin 2 pts); the remaining 405 women did not carry the mutation. BRCA1 related tumours showed higher grade, higher Ki67 protein expression, more frequent negative oestrogen, progesterone, HER2-neu receptor status. Patients with BRCA1 mutation had a higher incidence of bilateral breast (40% compared to 10% in non mutated patients) and ovarian cancer (16% compared to less than 1% in non mutated patients. 10-years OS (overall survial) was 81% in no BRCA1 mutation patients compare to 88% in mutated BRCA1 patients (p=0.7), 10-years DSF (local-regional and distant failure) was 81% vs. 67% (p=0.8), 10-years MFS (metastases free survival) was 85% vs 71% (p=0.1), and 10-years RFS (recurrence free survival) was 90% vs. 80% (p=0.1) respectively.
 Multivariate Cox analysis for DFS showed that node ratio > 12% (HR=2.12), increasing tumour diameter (HR=1.23), experienced significantly decreased DFS. Furthermore, overall survival analysis also showed that node ratio > 12% (HR=2.65), increasing tumour diameter (HR=1.23), experienced significantly decreased OS. There is an insignificant trend for patients without BRCA1 mutation and younger to have worse DFS (HR=1.28) and worse OS (HR=2.23).
 Conclusions
 Patients with BRCA1 mutations have higher incidence of bilateral breast and ovarian cancer which imposes the need for frequent and careful follow-up after therapy. Node ratio and tumour diameter are the strongest prognostic factors. A final conclusion will require more patients and longer follow up.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1044.

Dose-volume factors contributing to the incidence of radiation pneumonitis in non-small-cell lung cancer patients treated with three-dimensional conformal radiation therapy

PURPOSE

To analyze acute lung toxicity data of non-small-cell lung cancer patients treated with three-dimensional conformal radiation therapy in terms of dosimetric variables, location of dose within subvolumes of the lungs, and models of normal-tissue complication probability (NTCP).

METHODS AND MATERIALS

Dose distributions of 49 non-small-cell lung cancer patients treated in a dose escalation protocol between 1992 and 1999 were analyzed (dose range: 57.6-81 Gy). Nine patients had RTOG Grade 3 or higher acute lung toxicity. Correlation with dosimetric and physical variables, as well as Lyman and parallel NTCP models, was assessed. Lungs were evaluated as a single structure, as superior and inferior halves (to assess significance of dose to upper and lower lungs), and as ipsilateral and contralateral lungs.

RESULTS

For the whole lung, Grade 3 or higher pneumonitis was significantly correlated (p <or= 0.05) with mean dose and Lyman and parallel model indices (d(eff) and f(dam)). It was significantly correlated with these indices and with V20 for the ipsilateral lung and with mean dose and d(eff) for the inferior half of the lungs. Dosimetric and NTCP model quantities for the superior half of the lungs and contralateral lung were not significantly correlated (p > 0.5 for superior lung indices, and >0.1 for contralateral lung indices studied).

CONCLUSIONS

For these patients, commonly used dosimetric and NTCP models are significantly correlated with >or= Grade 3 pneumonitis. Equivalently strong correlations are found in the lower portion of the lungs and the ipsilateral lung, but not in the upper portion or contralateral lung.