Utility of Bolus in Post Mastectomy Radiation
Novick K, Chadha M, Harris E, Daroui P, Freedman G, Gao W, Hunt K, Park C, Rewari A, Suh W, Walker E, and Wong J. Utility of Bolus in Post Mastectomy Radiation. International Journal of Radiation Oncology Biology Physics 2020; 108(2):E25-E26.
International Journal of Radiation Oncology Biology Physics
Background: The most common site of local recurrence after mastectomy is within skin and subcutaneous tissues anterior to the pectoralis muscles. The application of tissue-equivalent bolus can improve dose to the skin, which is often significantly below prescription dose in modern radiation treatment plans. However, practice surveys have shown a great degree of international heterogeneity in use of bolus (Vu 2007).
Objectives: The American Radium Society (R) Appropriate Use Criteria (TM) Breast Cancer Committee examined the evidence for use of bolus in post mastectomy radiation. Methods: A PRISMA systematic review of available evidence through June 2019 was performed. The Committee reached a Delphi consensus on the appropriateness of bolus use in 3 different clinical variants.
Results: Of 26 articles identified using the search terms, 18 were included as evidence. No randomized data for the effect of bolus application on local recurrence for modern photon treatment plans has been published. Several comparative retrospective studies show equivalent rates of recurrence with or without bolus (Abel 2017; Tieu 2011; Uematsu 1993; Turner 2016). Low rates of recurrence (4%-9%) and low rates of grade 2 acute dermatitis (9-10%) were reported without bolus. Probability of grade 2 dermatitis increased with Dmax greater than 5311 cGy (Shiba 2018). Dosimetric evaluation suggests that adequate dose to the skin can be achieved with application of 1 cm bolus in 15 out of 25 treatment days (Andic 2009). Alternatively, 2 mm brass mesh bolus could be applied daily, necessitating only one treatment plan (Ordonez-Sanz 2014; Manager 2016), but, due to risk of neutron formation, should not be used with higher energy photon beams (>10 MV). The Delphi consensus revealed that application of bolus to the chest wall was considered usually appropriate but the omission of bolus from cases involving reconstruction may be appropriate. There was a significant amount of the heterogeneity in the rating of appropriateness for the omission of bolus.
Conclusions: Bolus use should be customized to the patient’s skin dose and the patient’s risk of skin recurrence. Some patients may have acceptable skin dose in their PMRT plan without bolus, so treatment plans with and without bolus should be evaluated. Patients with inflammatory carcinoma, positive anterior skin margins or poor skin dose without bolus may benefit more from more aggressive use of bolus while patients with breast reconstruction or poor skin healing may be at greater risk of toxicity with bolus. Aggressive use of bolus may include 1 cm bolus every other day or ≤0.5 cm daily. Less aggressive bolus may use 0.5 cm bolus every other day or no bolus. Removal of bolus after appearance of grade 2 acute dermatitis may help prevent progression to grade 3 toxicity and prevent treatment interruptions. Additional randomized evidence is greatly needed to resolve noted international and Committee heterogeneity regarding bolus use.