Outcomes in Patients Treated with Post-mastectomy Chest Wall Radiotherapy without the Routine Use of Bolus

M L Yap; M Tieu; J Sappiatzer; T Panzarella; J Cuartero; D McCready; A Fyles

doi:10.1016/j.clon.2018.03.005

Outcomes in Patients Treated with Post-mastectomy Chest Wall Radiotherapy without the Routine Use of Bolus

Clin Oncol (R Coll Radiol). 2018 Jul;30(7):427-432. doi: 10.1016/j.clon.2018.03.005. Epub 2018 Mar 23.

Authors

M L Yap¹, M Tieu¹, J Sappiatzer¹, T Panzarella², J Cuartero¹, D McCready³, A Fyles⁴

Affiliations

¹ Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
² Department of Biostatistics, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
³ Department of Surgery, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
⁴ Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. Electronic address: Anthony.fyles@rmp.uhn.on.ca.

PMID: 29580696
DOI: 10.1016/j.clon.2018.03.005

Abstract

Aims: The use of bolus in post-mastectomy radiotherapy (PMRT) varies significantly between institutions. We report on chest wall recurrence and acute toxicity rates for PMRT patients treated with selective use of bolus.

Materials and methods: We analysed PMRT patients who received adjuvant chest wall radiotherapy for invasive breast cancer between 2004 and 2009. Patient, tumour and cancer outcomes were collected from a prospective database, with additional radiotherapy and acute toxicity details supplemented retrospectively. Chest wall bolus was reserved for patients considered at high risk of local recurrence.

Results: There were 314 patients suitable for analysis: 52 received bolus, 262 did not. The mean age was 53.2 years. The median follow-up was 4.2 years. The most common T stage was T2 (37%), followed by T3/T4 (33%). There were 229 patients (73%) who had N+ disease; 213 (68%) patients had grade 3 cancer. Oestrogen receptor was positive in 176 (56%) cases, progesterone receptor was positive in 134 (43%) and HER2 receptor was positive in 24 (8%). Lymphovascular space invasion was present in 146 patients (46%), dermal invasion in 30 patients (10%) and positive margin in 14 patients (4%). The 4 year chest wall recurrence rate was 14% (95% confidence interval 5.4-26.8%) in the bolus group and only 3.5% (95% confidence interval 1.6-6.4%) in the non-bolus group. On univariate analysis, use of bolus was associated with a significant difference in chest wall recurrence (hazard ratio 3.09; 1.15-8.33; P = 0.025). However, when taking into account margin status, this significance was lost (hazard ratio = 2.45; 95% confidence interval 0.80-7.50, P = 0.12). There was a higher rate of acute grade 2 skin toxicity in patients receiving bolus compared with those without, 40% versus 21% (P = 0.01).

Conclusions: The selective use of bolus resulted in a small risk of chest wall recurrence rates for low-risk patients. This suggests that the routine use of bolus in PMRT patients may be unnecessary.

Keywords: Bolus; breast cancer; outcomes; post-mastectomy radiotherapy; radiotherapy.

MeSH terms

Adult
Aged
Breast Neoplasms / radiotherapy*
Breast Neoplasms / surgery
Female
Humans
Mastectomy
Middle Aged
Neoplasm Recurrence, Local / epidemiology*
Neoplasm Recurrence, Local / prevention & control
Radiotherapy, Adjuvant / adverse effects*
Radiotherapy, Adjuvant / methods*
Thoracic Wall / radiation effects