Using the Bolus in Post-mastectomy Radiation Therapy (PMRT): A National Survey on Behalf of the Italian Association of Radiotherapy and Clinical Oncology (AIRO) Breast Cancer Group

Abstract

Background/Aim: This study aimed to investigate the bolus practice among Italian radiation oncologists. Patients and Methods: In 2018, a survey on bolus application was sent to all members of the Italian Association of Radiotherapy and Clinical Oncology. Results: The survey was joined by 102 radiation oncologists. Not all respondents answered to every question. A 69.5% of 82 respondents used bolus in case of skin infiltration and 52 of 68 respondents (76.5%) applied it every day. Skin was included as part of chest wall Clinical Target Volume both in the absence or the presence of breast reconstruction. Five mm bolus was the most used. 3D Conformal radiotherapy was the most used technique, in 73.5% of cases. Acute RTOG G2-G3 skin toxicity was recorded by 93.9% physicians. Conclusion: There was heterogeneity in the use of bolus, though an agreement was found in some topics. The achievement of a National Consensus may represent an interesting future goal.Post-mastectomy radiation therapy (PMRT) has been demonstrated to improve locoregional control and overall survival for patients with high risk breast cancer recurrence in several studies. Chest wall represents the anatomical region with the highest risk of recurrence (1-7); main factors influencing the recurrence rate are: primary tumor size, nodal status, positive margins, tumor grade and lymphovascular invasion (8, 9).Bolus is a tissue equivalent material, with atomic number and density similar to tissue or water, placed on the chest wall to spread the area that is covered by the 95% isodose increasing the surface radiation dose (10).Up to now, its application remains controversial with some uncertainties about its routine application, especially concerning the timing (every day or less frequently). Moreover, a large variability about bolus thickness between different Radiation Oncology Departments has been reported (11).However, the use of a bolus has been reported to increase the frequency of severe radiation dermatitis. Therefore, the advantage in terms of reduced risk of local recurrence could be thwarted by increased acute skin and subcutaneous tissue side effects that might require interruption of the radiation treatment with a potential detrimental impact on local control (12,13).Finally, late cutaneous/subcutaneous toxicities could occur, when breast prosthesis are present, with a potential worsening of the cosmetic result (14).To the best of our knowledge, routine use of a bolus was mentioned only in ASCO guidelines published in 2001 with a low grade of evidence about its recommendation (15).In this context of uncertainties, the aim of this survey was to investigate bolus routine practice among Italian radiation 6505

A Delphi study and International Consensus Recommendations: The use of bolus in the setting of postmastectomy radiation therapy for early breast cancer

“…Bolus serves as a tissue equivalent material that shifts the 95-100% isodose towards the skin and subcutaneous tissue (depending on the thickness of bolus and subcutaneous tissue) [1]. The need for bolus for all breast cancer patients planned for PMRT has been questioned due to skin toxicity as seen in a number of studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], clinician surveys [21][22][23][24][25], and national guidelines [26]. All studies showed huge variability in terms of bolus indications and use, with no proven optimum regimen pertaining to thickness, schedule (i.e., daily, alternating days), bolus material, and RT planning characteristics (such as beam energy)…”

Comparing brass mesh to tissue equivalent bolus materials for volumetric modulated arc therapy chest wall irradiation

“…In PMRT patients, clinicians usually intend to treat the skin and typically prescribe the use of physical bolus (p‐bolus) to increase the superficial dose in the presence and absence of breast reconstruction 8 . Regimens for p‐bolus can become complicated and cause confusion among the staff, particularly for busy clinics.…”

“…In PMRT patients, clinicians usually intend to treat the skin and typically prescribe the use of physical bolus (p‐bolus) to increase the superficial dose in the presence and absence of breast reconstruction. 8 Regimens for p‐bolus can become complicated and cause confusion among the staff, particularly for busy clinics. While the use of p‐bolus in PMRT is itself a point of controversy in the community, 9 , 10 understanding the available tools to control the superficial dose is imperative to providing the best patient experience and outcomes.…”