A study on the use of a subcutaneous injection to reduce skin side effects of breast brachytherapy with palladium seeds.

1 out of 8 women develop breast cancer. Breast conserving therapy has been shown to be as effective as ablative therapy in the treatment of a selected group of early stage breast cancer patients. Postoperative irradiation of the breast is part of the breast conserving therapy. Along with the fact that local recurrences usually occur close to the primary tumor, this stimulated worldwide research on various forms of partial breast irradiation and cosmesis and quality of life.With Permanent Breast Seed Implant (PBSI), a form of brachytherapy, radioactive seeds are implanted percutaneously into the surgical cavity. Palladium103 seeds, with a halflife of 16.8 days, and a therapeutic dosage after 84 days, appear to be the most appropriate for this purpose. 5year results of several multicentre trials on Permanent Breast Seed Implant (PBSI) were reported in 2015. In total, 134 patients with early stage invasive breast cancer were treated with a permanent breast seed implant as the sole adjuvant radiation treatment after breast conserving surgery. The trials accrued patients based on the guideline for accelerated partial breast irradiation (APBI) of the American Society for Radiation Oncology (ASTRO). The outcomes included overall and diseasefree survival and local recurrence at 5 years. The true local recurrence rate was compared using 2tailed paired t tests for control estimates calculated using the Tufts University ipsilateral breast tumor recurrence and Memorial Sloan Kettering ductal carcinoma in situ nomograms. The observed local recurrence rate at a median followup period of 63 months was 1.2%, similar to the estimate for whole breast irradiation (1.4% p=0.23), The 5year overall survival rate was 97.4% SD ± 1.9%, and the disease free survival rate was 96.4% SD ± 2.1%.

The most common side effects of PBSI are skinrelated. Acute skin toxicity comprises a moist desquamation in 16% with PBSI, which is lower than with WBI. Late skin toxicity leads to fibrosis and induration or telangiectasia. The latter occurs in 25% of the patients after PBSI, slightly more than after WBI5. Telangiectasia corresponds to the dilation of an abnormal neovasculature in the skin following the destruction of normal capillaries by the radiation treatment. Due to their prominent appearance, telangiectasia have a negative effect on cosmesis, the patient’s body image and quality of life. Therefore, interventions to reduce the clinical appearance of telangiectasia may impact a patient’s overall wellbeing or quality of life. The use of a subcutaneously injected spacer, to increase the distance between the radiation sources and the skin, could reduce skin toxicity after PBSI. Studies in patients with prostate cancer who underwent brachytherapy, show that the use of a hyaluronic acid spacer reduced rectal dose. This spacer is reabsorbed in 6 to 12 months and is not associated with an increased risk of infection. Hyaluronic Acid is widely used as a dermal filler in cosmetic industry. The use of a spacer in breast cancer patients has never been done before. In this study the effect of a hyaluronic acid spacer on skin toxicity after PBSI will be investigated in a randomized controlled trial. All patients in the study will receive PBSI as sole adjuvant radiation therapy with or without spacer injection, depending on their treatment allocation. The primary outcome measure is the occurrence of telangiectasia at two years. In addition, the effect of PBSI on cosmesis, quality of life (both patientreported), wound infection, local recurrence and (disease free) survival and cost effectiveness will be assessed and compared to a comparable group of patients getting standard radiation treatment. This will be the first study on PBSI in Europe. If the results of this study are favourable, PBSI can be a very patientfriendly and costeffective alternative for external whole breast irradiation in breast conserving therapy.

We hypothesize that injecting an inert/biodegradable spacer between the dermis and the most superficial layer of the planned target volume (PTV) could remove the skin from the high dose volume, and this would result in a significant reduction of telangiectasia at 2 years.

primary outcome: 1 and 2 years

secondary outcomes:

local recurrence, disease free and overall survival (1,2,3,4,5,10y)

induration (Baseline, 2months, 1y, 2y)

wound infection (3m)

cosmetic results and health related quality of life (BL, 6M, 1-5y)

costeffectiveness (1y)

Validation of a Dutch translation of the BCTOS questionnaire

subcutaneous injection of 5-10ml hyaluronic acid (Barrigel of Restylane SubQ) as a spacer during PBSI

Intervention group receives PBSI treatment with spacer injection, control group receives PBSI without spacer injection.