Dosimetric Improvements with a Novel Breast Stereotactic Radiotherapy Device for Delivery of Preoperative Partial-Breast Irradiation

A Prospective Trial of Single-Fraction Radiation to the Tumor Bed with a Novel Breast-Specific Stereotactic Radiation Therapy Device: The GammaPod

Purpose

Radiation therapy for early-stage breast cancer is typically delivered in a hypofractionated regimen to the whole breast followed by a tumor bed boost. This results in a treatment course of approximately 4 weeks. In this study, the tumor bed boost was delivered in a single fraction as part of a safety and feasibility study for FDA clearance of the device.

Methods and Materials

Eligible women with early-stage breast cancer underwent lumpectomy followed by radiation therapy. Patients underwent breast immobilization using a system specific to the GammaPod followed by CT simulation, boost treatment planning, and boost treatment delivery all in a single treatment day. Patients then started whole-breast radiation therapy within 1 week of the boost treatment. Patients and treatments were assessed for safety and feasibility. Acute toxicities were recorded.

Results

A single-fraction boost of 8 Gy was delivered to the tumor bed before a course of whole-breast radiation. The GammaPod treatment was successfully delivered to 14 of 17 enrolled patients. Acute toxicities from all radiation therapy, inclusive of the boost and whole-breast radiation, were limited to grade 1 events.

Conclusions

The GammaPod device successfully delivered a single-fraction boost treatment to the tumor bed with no change in expected acute toxicities. The results of this study led to FDA clearance of the device through the Investigational Device Exemption process at the FDA. The GammaPod is in clinical use at 4e institutions nationally and internationally, with additional sites pending in 2023.

A narrative review for radiation oncologists to implement preoperative partial breast irradiation

The strategy to anticipate radiotherapy (RT) before surgery, for breast cancer (BC) treatment, has recently generated a renewed interest. Historically, preoperative RT has remained confined either to highly selected patients, in the context of personalized therapy, or to clinical research protocols. Nevertheless, in the recent years, thanks to technological advances and increased tumor biology understanding, RT has undergone great changes that have also impacted the preoperative settings, embracing the modern approach to breast cancer. In particular, the reappraisal of preoperative RT can be viewed within the broader view of personalized and tailored medicine. In fact, preoperative accelerated partial breast irradiation (APBI) allows a more precise target delineation, with less variability in contouring among radiation oncologists, and a smaller treatment volume, possibly leading to lower toxicity and to dose escalation programs. The aim of the present review, which represents a benchmark study for the AIRC IG-23118, is to report available data on different technical aspects of preoperative RT including dosimetric studies, patient's selection and set-up, constraints, target delineation and clinical results. These data, along with the ones that will become available from ongoing studies, may inform the design of the future trials and representing a step toward a tailored APBI approach with the potential to challenge the current treatment paradigm in early-stage BC.Trial registration: The study is registered at clinicaltrials.gov (NCT04679454).

Stereotactic partial breast irradiation in primary breast cancer: A comprehensive review of the current status and future directions

In selected low-risk breast cancer patients, accelerated partial breast irradiation (APBI) may represent an alternative option to the whole breast irradiation to reduce the volume of irradiated breast and total treatment duration. In the last few years, preliminary data from clinical trials showed that stereotactic partial breast radiotherapy may have the advantage to be less invasive compared to other APBI techniques, with preliminary good results in terms of local toxicity and cosmesis: the use of magnetic resonance, fiducial markers in the tumor bed, and new breast devices support both a precise definition of the target and radiation planning.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021257856, identifier CRD42021257856.

Reproducibility of a novel, vacuum-assisted immobilization for breast stereotactic radiotherapy

A novel, breast‐specific stereotactic radiotherapy device has been developed for delivery of highly conformal, accelerated partial breast irradiation. This device employs a unique, vacuum‐assisted, breast cup immobilization system that applies a gentle, negative pressure to the target breast with the patient in the prone position. A device‐specific patient loader is utilized for simulation scanning and device docking. Prior to clinical activation, a prospective protocol enrolled 25 patients who had been or were to be treated with breast conservation surgery and adjuvant radiotherapy for localized breast cancer. The patients underwent breast cup placement and two separate CT simulation scans. Surgical clips within the breast were mapped and positions measured against the device’s integrated stereotactic fiducial/coordinate system to confirm reproducible and durable immobilization during the simulation, treatment planning, and delivery process for the device. Of the enrolled 25 patients, 16 were deemed eligible for analysis. Seventy‐three clips (median, 4; mean, 4.6; range, 1–8 per patient) were mapped in these selected patients on both the first and second CT scans. X, Y, and Z coordinates were determined for the center point of each clip. Length of vector change in position was determined for each clip between the two scans. The mean displacement of implanted clips was 1.90 mm (median, 1.47 mm; range, 0.44–6.52 mm) (95% CI, 1.6–2.20 mm). Additional analyses stratified clips by position within the breast and depth into the immobilization cup. Overall, this effort validated the clinically utilized 3‐mm planning target volume margin for accurate, reliable, and precise employment of the device.

A novel, adaptable, radiographically opaque, multi-plane continuous filament marker for optimizing tissue identification, radiation planning, and radiographic follow-up

Background

In breast cancer treatment, marking the tumor bed is an important aspect of the surgical component of therapy. Clear delineation of the tumor bed allows radiation oncologists a defined target for planning and delivering postoperative radiation therapy (XRT). Tumor bed marking also allows radiographic follow-up of the tumor bed on subsequent breast imaging. The aim of this assessment is to evaluate the ease and feasibility of utilizing a tumor bed filament marker (VeraFormÒ, Videra Surgical inc., USA) as a marker in post-operative benign surgical sites and malignant breast surgical tumor beds in breast cancer surgery.

Methods

The filament marker is a novel radiopaque surgical filament that in lieu of clips and other markers is implanted in the surgical tumor bed during breast surgery. Following development of the filament marker, the researchers used breast phantoms and radiographic images to develop a series of geometric patterns of placement options that optimize comprehensive multi-plane radiographic interpretation of the exact tumor bed or surgical margin. Three breast surgeons at 3 separate institutions then used this filament as a continuous multi-plane marker in 20 patients during breast conservation surgery. In these patients, the filament marker was thus used to mark the tumor bed (breast cancer surgery) or surgical site (benign breast disease) instead of the more traditional devices such as clips or other metallic open framework devices. We then assessed 2 important factors related to this device; (I) the ease, feasibility, and accuracy of in vivo placement with oncoplastic and non-oncoplastic breast conservation surgery techniques; (II) the radiographic footprint this device left on standard imaging protocols of post-operative mammogram (MMG), computed tomography (CT) scan, breast magnetic resonance imaging (MRI) examinations, and ultrasounds (USs) for both routine follow-up imaging and for standard radiation planning.

Results

There were no adverse events reported with the use of this device. The cases were then reviewed by a multidisciplinary team that included the original surgeon, a breast radiologist, and radiation oncologist. Their unanimous evaluation was that the filament marker clearly delineated all sides and planes of the tumor bed (cancer surgery) or surgical site (benign disease). Regardless of surgical technique utilized, this information provided precise 3D guidance for radiation planning and delivery as well as radiographic follow-up. The surgeons involved reported that delineating the bed with the filament marker was a quick and easy procedure and did not interfere with performing the planned surgical technique. Radiologists, surgeons, and radiation oncologists found that the filament marker was not only radiographically opaque on CT and MMG, but also caused no significant artifact on CT, MRI, US, or MMG.

Conclusions

The continuous multi-plane filament marker is a new device that fulfills the heretofore unmet need for safe and improved tumor bed and tissue site marking. It is an easy to place, non-palpable continuous multi-plane radiographic opaque tissue marker that seems to better delineate the tumor bed, regardless of type of breast surgery performed, while providing a more accurate 3D image for radiation planning and radiographic follow-up on MMG MRI, CT and US.

Creating a Favorable Microenvironment for Fat Grafting in a Novel Model of Radiation-Induced Mammary Fat Pad Fibrosis

BACKGROUND

Radiofibrosis of breast tissue compromises breast reconstruction by interfering with tissue viability and healing. Autologous fat transfer may reduce radiotherapy-related tissue injury, but graft survival is compromised by the fibrotic microenvironment. Elevated expression of receptor for hyaluronan-mediated motility (RHAMM; also known as hyaluronan-mediated motility receptor, or HMMR) in wounds decreases adipogenesis and increases fibrosis. The authors therefore developed RHAMM peptide mimetics to block RHAMM profibrotic signaling following radiation. They propose that this blocking peptide will decrease radiofibrosis and establish a microenvironment favoring adipose-derived stem cell survival using a rat mammary fat pad model.

METHODS

Rat mammary fat pads underwent a one-time radiation dose of 26 Gy. Irradiated (n = 10) and nonirradiated (n = 10) fat pads received a single intramammary injection of a sham injection or peptide NPI-110. Skin changes were examined clinically. Mammary fat pad tissue was processed for fibrotic and adipogenic markers using quantitative polymerase chain reaction and immunohistochemical analysis.

RESULTS

Clinical assessments and molecular analysis confirmed radiation-induced acute skin changes and radiation-induced fibrosis in rat mammary fat pads. Peptide treatment reduced fibrosis, as detected by polarized microscopy of picrosirius red staining, increased collagen ratio of 3:1, reduced expression of collagen-1 crosslinking enzymes lysyl-oxidase, transglutaminase 2, and transforming growth factor β1 protein, and increased adiponectin, an antifibrotic adipokine. RHAMM was expressed in stromal cell subsets and was downregulated by the RHAMM peptide mimetic.

CONCLUSION

Results from this study predict that blocking RHAMM function in stromal cell subsets can provide a postradiotherapy microenvironment more suitable for fat grafting and breast reconstruction.

Robotic Stereotactic Boost in Early Breast Cancer, a Phase 2 Trial

PURPOSE

To evaluate the feasibility and toxicity of a single-fraction 8-Gy stereotactic boost after whole-breast irradiation in early breast cancer. The primary aim of this phase 2 study was to evaluate cutaneous breast toxicity using National Cancer Institute Common Terminology Criteria for Adverse Events (version 4) 3 months after the boost. Secondary objectives were local control, survival, and patient-reported quality of life using the European Organisation for Research and Treatment of Cancer QLQ-C30 and breast-specific European Organisation for Research and Treatment of Cancer QLQ-BR 23 questionnaires.

METHODS AND MATERIALS

Patients with invasive ductal or lobular pT1-2 breast cancer treated with lumpectomy with clear margins and pN0 were included. Patients requiring chemotherapy were excluded.

RESULTS

Twenty-eight eligible patients received the planned boost, and 26 had hormonal therapy. The procedure was technically successful without procedural complications. A median of 3 fiducials were tracked, and 115 beams were used. There were 22 acute grade 1 breast skin toxicities, including fibrosis, pain, erythema, or pigmentation. There were 2 acute grade 2 erythemas. Median skin boost dose was inversely correlated with acute skin toxicity (P = .028). QLQ-C30 scores revealed acute dyspnea and arm symptoms without correlation to the boost dose. Breast symptom QLQ-BR23 scores did not deteriorate, although upset with hair loss and systemic side effects of hormonal therapy were observed. After a median follow-up of 38 months, 1 patient had in-boost-field relapse, and there were 5 late grade 1 and 1 grade 2 skin toxicities.

CONCLUSIONS

Single-fraction stereotactic boost after conventional whole-breast irradiation in early breast cancer is feasible with minor toxicities. Quality of life and specific breast items showed excellent patient acceptance.