Salvage brachytherapy for second ipsilateral breast tumor event: Relating dosimetric analysis to late side effects.

PURPOSE: For second ipsilateral breast tumor event (2ndIBTE), conservative treatment (CT) involving wide local excision plus accelerated partial breast reirradiation (APBrI) is increasingly used as an alternative to mastectomy. This study investigates the impact of APBrI technique and multicatheter interstitial high dose-rate brachytherapy (MIB) dosimetry parameters on toxicity and survival in patients with 2ndIBTE. MATERIALS-METHODS: Data from patients with 2ndIBTE treated with CT, were analyzed. Inclusion criteria specified 2ndIBTE occurring at least one year after 1st CT for primary breast cancer. Treatment details and dosimetry parameters were recorded. Primary endpoint was late toxicity. Secondary endpoints were late toxicity prognostic factors analysis and oncological outcome. RESULTS: From 07/2005 and 07/2023, 201 patients (pts) received 2nd CT. With a median follow-up of 49.6 months (44.9-59.5), tumor size was less than 2 cm (88.1%), with estrogen receptor positive (92.7%). Patients were low (63.7%) or intermediate (29.8%) GEC-ESTRO APBI risk classification. Late toxicities were observed in 34.8% (G1 52.3%, G2 40.7%). Cutaneous fibrosis was the most common toxicity. Cosmetic outcomes were excellent in 64.1%. Dosimetry analysis revealed positive correlations between complications and absolute volumes of CTV, V100, V150, and V200. Volumes requiring higher needle number and lower DNR resulted in fewer complications. 5-year disease-free and overall survival were 88% and 95% respectively. CONCLUSION: Second CT for 2ndIBTE showed favorable oncological outcomes and survival rates. Complications were correlated with specific dosimetric parameters, emphasizing the importance of tailored treatment planning. This study provides valuable insights in risk stratification and MIB optimization for APBrI.

Workflow optimization of brachytherapy-based very accelerated partial breast irradiation.

PURPOSE: For low-risk breast cancer, accelerated partial breast irradiation (APBI) is a level 1 evidence procedure. Brachytherapy based very APBI (vAPBI) makes it possible to perform adjuvant irradiation in 4 to 1 fraction. However, vAPBI organization is critical. The aim of this technical note is to report on its optimization. METHODS AND MATERIALS: To offer to low-risk breast cancer patient an efficient, simple, rapid adjuvant irradiation with a reduced number of hospital visits, a new organization of vAPBI based on a single fraction was established, merging all the different steps (from first consultation to irradiation) into a 4-5-consecutive-hour period. This therapeutic program was developed in strong collaboration with radiation oncologists, medical physicists, radiation therapists, and the medical secretary. RESULTS: After the validation of adjuvant breast irradiation, the patient was offered a telemedicine consultation with the radiation oncologist. Then, the day of vAPBI, the patient arrived at the brachytherapy unit at 08:00 AM for an in-person consultation followed by a preimplant CT scan (defining catheter number and position). After breast local anesthesia, catheter placement was performed followed by a postimplant CT scan for planning purposes. A total dose of 16 Gy in 1 fraction was delivered before removing the catheters. The patient was discharged from the brachytherapy unit around 12:30 PM with an upcoming surveillance consultation date. CONCLUSIONS: VAPBI organization optimization makes it possible to propose a short 5-h procedure from medical consultation to treatment with only one round trip. Strict organization among staff is required.

Biodosimetry in interventional radiology: cutaneous-based immunoassay for anticipating risks of dermatitis.

OBJECTIVES: Interventional radiology procedures expose individuals to ionizing radiation. However, existing dosimetry methods do not provide the dose effectively absorbed to the skin, and do not consider the patient's individual response to irradiation. To resolve this lack of dosimetry data, we developed a new external irradiation biodosimetry device, DosiKit, based on the dose-dependent relationship between irradiation dose and radiation-induced H2AX protein phosphorylation in hair follicles. This new biological method was tested in Clermont-Ferrand University Hospital to evaluate the assay performances in the medical field and to estimate DosiKit sensitivity threshold. METHODS: DosiKit was tested over 95 patients treated with neuroradiological interventions. For each intervention, lithium fluoride thermoluminescent dosimeters (TLD) were used to measure total dose received at each hair collection point (lateral and occipital skull areas), and conventional indirect dosimetry parameters were collected with a Dosimetry Archiving and Communication System (DACS). RESULTS: Quantitative measurement of radiation-induced H2AX protein phosphorylation was performed on 174 hair samples before and after the radiation exposure and 105 samples showed a notable induction of gammaH2AX protein after the radiological procedure. According to a statistical analysis, the threshold sensitivity of the DosiKit immunoassay was estimated around 700 mGy. CONCLUSIONS: With this study, we showed that DosiKit provides a useful way for mapping the actually absorbed doses, allowing to identify patients overexposed in interventional radiology procedures, and thus for anticipating risk of developing dermatitis. KEY POINTS: • DosiKit is a new external irradiation biodosimetry device, based on the dose-dependent relationship between irradiation dose and radiation-induced H2AX protein phosphorylation in hair follicles. • DosiKit was tested over 95 patients treated with neuroradiological interventions. • The threshold sensitivity of the DosiKit immunoassay was estimated around 700 mGy and DosiKit provides a useful way for mapping the actually absorbed doses.