Technique and outcome of post-mastectomy adjuvant chest wall radiotherapy—the role of tissue-equivalent bolus in reducing risk of local recurrence

Abstract

Objective: Adjuvant chest wall radiotherapy is used in patients with high-risk histological features post-mastectomy to reduce the risk of locoregional recurrence. Treatment can be given with or without a tissue-equivalent bolus to increase skin surface dose. The additional benefit of using a bolus remains unclear; however, it is known to be associated with a higher incidence of skin toxicity. This study compared chest wall recurrence and skin toxicity in patients treated with and without a bolus. Methods: This retrospective cohort study reviewed 314 consecutive patients who received chest wall radiotherapy between 2005 and 2010. Data were collected on histological, demographic and treatment parameters and on the incidence and grade of acute skin reactions. Treatment outcomes analyzed included chest wall recurrence, disease-free survival and overall survival (OS). Results: 101 patients received treatment with a bolus; 213 patients received treatment without a bolus. A significantly higher incidence of acute skin toxicity was seen in the bolus treatment group (p = 0.002). One patient treated with a bolus developed chest wall recurrence compared with four patients treated without a bolus. No statistically significant difference could be shown between the two groups. 66 (21%) patients had metastatic relapse. Median time to relapse was 29.5 months and OS was 76% in both treatment groups. Conclusion: No statistically significant difference in chest wall recurrence can be demonstrated between patients treated with and without a bolus. Advances in knowledge: This study is consistent with limited previous literature and invites further evaluation of the role of a bolus in post-mastectomy chest wall radiotherapy, especially considering the increased toxicity that the use of a bolus generates.

Quantitative Effect of Bolus on Skin Dose in Postmastectomy Radiation Therapy

“…Based on the lack of evidence-based causation between changes in dose and potential recurrence, there is variability of bolus application in a clinical setting. Some physicians may not find that the benefits of the bolus outweigh the associated risks, namely the increased risk of RD [6,14,17,18]. Skin toxicity is an exceedingly common side effect of RT which can be very painful, may lead to long-term sequelae such as undesirable cosmesis, fibrosis, chronic pain, hyperpigmentation, and telangiectasia, and can decrease quality of life.…”

“…It is therefore important to find a balance between tolerable skin toxicity and adequate treatment to the skin. Turner et al followed up 314 postmastectomy patients and found that among the 101 patients treated with bolus, 75% had grade 1-2 acute skin toxicity compared with 57.3% of those treated without bolus (P ¼ .002) [14]. Abel et al [6] reported that 70% of patients treated with bolus compared with 42% of those treated without a bolus developed !…”

“…Some centres use it routinely for postmastectomy patients, and some only apply a bolus under high-risk circumstances such as skin invasion, lymphovascular invasion, inflammatory disease, close or positive margins and/or its used as a compensator for irregular chest wall [13]. Given the risk of increased skin toxicity associated with bolus use [5,6,14,15], a better understanding of its effect on skin dose and local control is needed to help inform treatment guidelines. Accordingly, the primary objective of this study was to quantify the effect of bolus on mean and maximum skin dose in clinical PMRT treatment plans.…”

The Lack of Consensus of International Contouring Guidelines for the Dorsal Border of the Chest Wall Clinical Target Volume: What is the Impact on Organs at Risk and Relationships to Patterns of Recurrence in the Modern Era?

“… 16 , 17 Furthermore, this study cannot speak to the implications for use of skin bolus in the postmastectomy setting, which varies at our institution, but is commonly applied, usually in an every-other-day fashion or daily until a Grade 2 reaction develops. 18 …”

A Patient-Specific Polylactic Acid Bolus Made by a 3D Printer for Breast Cancer Radiation Therapy

“…The ability to spare the skin is very useful for many different types of cancer, however, there is a problem with the treatment of superficial lesions near the skin surface. Thus, a build-up material (bolus) is placed in direct contact with the patient’s skin surface in order to increase the superficial dose and improve dose uniformity by compensating for missing tissue [4–6]. Normal organs including lung and heart could be protected because bolus brings isodose lines toward the surface and it was demonstrated that the use of bolus in the postmastectomy radiotherapy reduced the normal tissue complication probabilities (NTCPs) of the ipsilateral lung [7].…”