Single dose IOERT versus whole breast irradiation : Cosmetic results in breast-conserving therapy

A Novel Treatment Planning Design for Intraoperative Electron Radiation Therapy (IOERT) using an Electronic Board

Background

Intraoperative Irradiation Therapy (IORT) refers to the delivery of radiation during surgery and needs the computed- thickness of the target as one of the most significant factors.

Objective

This paper aimed to compute target thickness and design a radiation pattern distributing the irradiation uniformly throughout the target.

Material and Methods

The Monte Carlo code was used to simulate the experimental setup in this simulation study. The electron flux variations on an electronic board's metallic layer were studied for different thicknesses of the target tissue and validated with experimental data of the electronic board.

Results

Based on the electron number for different Poly Methyl Methacrylate (PMMA) phantom thicknesses at various energies, 6 MeV electrons are suitable to determine the target thickness. Uniformity in radiation and corresponding time for each target were investigated. The iso-dose and percentage depth dose curves show that higher energies are suitable for treatment and distribute uniform radiation throughout the target. Increasing the phantom thickness leads to rising radiation time based on the radiation time corresponding to these energies. The tissue thickness of each section is determined, and the radiation time is managed by scanning the target.

Conclusion

Calculation of the thickness of the remaining tissue and irradiation time are needed after incomplete tumor removal in IORT for various remaining tissues. The patients should be protected from overexposure to uniform irradiation of tissues since the radiation dose is prescribed and checked by an oncologist.

Assessment of non-inferiority with meta-analysis: example of hypofractionated radiation therapy in breast and prostate cancer

The aim of this study was to propose a methodology for the assessment of non-inferiority with meta-analysis. Assessment of hypofractionated RT in prostate and breast cancers is used as an illustrative example. Non-inferiority assessment of an experimental treatment versus an active comparator should rely on two elements: (1) an estimation of experimental treatment’s effect versus the active comparator based on a meta-analysis of randomized controlled trials and (2) the value of an objective non-inferiority margin. This margin can be defined using the reported effect of active comparator and the percentage of the active comparator’s effect that is desired to be preserved. Non-inferiority can then be assessed by comparing the upper bound of the 95% confidence interval of experimental treatment’s effect to the value of the objective non-inferiority margin. Application to hypofractionated RT in breast cancer showed that hypofractionated whole breast irradiation (HWBI) appeared to be non-inferior to conventionally fractionated RT for local recurrence. This was not the case for accelerated partial breast irradiation (APBI). Concerning overall survival, non-inferiority could not be claimed for either HWBI or APBI. For prostate cancer, the lack of demonstrated significant superiority of conventional RT versus no RT precluded any conclusion regarding non-inferiority of hypofractionated RT.

Intraoperative Radiotherapy for Breast Cancer

Intraoperative radiotherapy (IORT) for early stage breast cancer is a technique for partial breast irradiation. There are several technologies in clinical use to perform breast IORT. Regardless of technique, IORT generally refers to the delivery of a single dose of radiation to the periphery of the tumor bed in the immediate intraoperative time frame, although some protocols have performed IORT as a second procedure. There are two large prospective randomized trials establishing the safety and efficacy of breast IORT in early stage breast cancer patients with sufficient follow-up time on thousands of women. The advantages of IORT for partial breast irradiation include: direct visualization of the target tissue ensuring treatment of the high-risk tissue and eliminating the risk of marginal miss; the use of a single dose coordinated with the necessary surgical excision thereby reducing omission of radiation and the selection of mastectomy for women without access to a radiotherapy facility or unable to undergo several weeks of daily radiation; favorable toxicity profiles; patient convenience and cost savings; radiobiological and tumor microenvironment conditions which lead to enhanced tumor control. The main disadvantage of IORT is the lack of final pathologic information on the tumor size, histology, margins, and nodal status. When unexpected findings on final pathology such as positive margins or positive sentinel nodes predict a higher risk of local or regional recurrence, additional whole breast radiation may be indicated, thereby reducing some of the convenience and low-toxicity advantages of sole IORT. However, IORT as a tumor bed boost has also been studied and appears to be safe with acceptable toxicity. IORT has potential efficacy advantages related to overall survival related to reduced cardiopulmonary radiation doses. It may also be very useful in specific situations, such as prior to oncoplastic reconstruction to improve accuracy of adjuvant radiation delivery, or when used as a boost in higher risk patients to improve tumor control. Ongoing international clinical trials are studying these uses and follow-up data are accumulating on completed studies.

Cosmetic changes following surgery and accelerated partial breast irradiation using HDR interstitial brachytherapy : Evaluation by a multidisciplinary/multigender committee

BACKGROUND

Patients with early-stage breast cancer can benefit from adjuvant accelerated partial breast irradiation (APBI) following breast-conserving surgery (BCS). This work reports on cosmetic results following APBI using multicatheter high-dose-rate interstitial brachytherapy (HDR-IBT).

PATIENTS AND METHODS

Between 2006 and 2014, 114 patients received adjuvant APBI using multicatheter HDR-IBT. For each patient, two photographs were analyzed: the first was taken after surgery (baseline image) and the second at the last follow-up visit. Cosmesis was assessed by a multigender multidisciplinary team using the Harvard Breast Cosmesis Scale. Dose-volume histogram (DVH) parameters and the observed cosmetic results were investigated for potential correlations.

RESULTS

The median follow-up period was 3.5 years (range 0.6-8.5 years). The final cosmetic scores were 30% excellent, 52% good, 14.5% fair, and 3.5% poor. Comparing the baseline and follow-up photographs, 59.6% of patients had the same score, 36% had a better final score, and 4.4% had a worse final score. Only lower target dose nonuniformity ratio (DNR) values (0.3 vs. 0.26; p = 0.009) were significantly associated with improved cosmetic outcome vs. same/worse cosmesis.

CONCLUSION

APBI using multicatheter HDR-IBT adjuvant to BCS results in favorable final cosmesis. Deterioration in breast cosmesis occurs in less than 5% of patients. The final breast cosmetic outcome in patients treated with BCS and APBI using multicatheter HDR-IBT is influenced primarily by the cosmetic result of the surgery. A lower DNR value is significantly associated with a better cosmetic outcome.