Accelerated treatment of breast cancer: dosimetric comparisons between interstitial HDR brachytherapy, mammosite balloon brachytherapy, and external beam quadrant radiation

Increased Skin Dose With the Use of a Custom Mattress for Prone Breast Radiotherapy

The purpose of this study was to measure and compare the loss of buildup to the skin of the breast in the prone position due to 2 different positioning systems during tangential external beam irradiation. Two experiments were performed; one with a standard nylon-covered foam support and another with a novel helium-filled Mylar bag support. The choice of helium-filled Mylar was to reduce the contamination to as low as possible. The experiments were designed to allow a surface dose measurement and a depth dose profile with the pads placed in the path of the beam in front of the detector. All measurements were taken using a Capintec PS-033 thin-window parallel plate ionization chamber. The standard nylon-covered foam pad caused the surface dose to rise as it got closer to the skin. When the pad was directly touching the surface, the surface dose increased by 300% compared to the result when no pad was present. This loss of buildup to the surface was similar to that of a custom bolus material. The opposite effect occurred with the use of the helium-filled Mylar bag, namely the surface dose gradually decreased as the pad got closer to the phantom. When the Mylar pad was directly touching the phantom, the surface dose was decreased by 7% compared to when no pad was present. The use of a foam pad could potentially result in a significant higher dose to the skin, resulting in an enhanced acute skin reaction. Therefore, special care should be taken in this clinical scenario and further investigation of an air- or helium-based mylar support pad should be investigated in the context of definitive breast radiation treatment.

Feasibility study on the MammoSite in early-stage breast cancer: Initial experience

The aims of this study were to evaluate the feasibility, practicality, efficacy and safety of the delivery of accelerated partial breast irradiation using the MammoSite for the boost phase. Six patients aged 53-69 years with stage T1N0, T2N0, Grade I-II invasive ductal carcinoma received 9-10 Gy prescribed at 1 cm from the MammoSite balloon surface in two fractions of 4.5-5 Gy 6 h apart. The MammoSite was inserted 20-37 days postoperatively. External beam radiation therapy to the whole breast commenced 1-5 days after accelerated partial breast irradiation. The maximum skin dose ranged from 3 to 9 Gy. The skin-cavity distance ranged from 7 to 19 mm. Local discomfort resolved as the scar healed spontaneously within 3-5 days. No Grade III or higher acute toxicity or local infection was recorded. The ease of insertion and accuracy of dosimetry makes the MammoSite suitable for use in properly selected women with early-stage breast cancer in a trial setting.

Partial-breast treatment for early breast cancer: emergence of a new paradigm

Although hailed as a paradigm shift, the breast conservative treatment that emerged in the 1980s was in fact an extension of the Halstedian concept, wherein whole-breast irradiation (WBI) compensated for the limited surgery. Observations that 80-90% of breast recurrences after breast conservative surgery and WBI occur in the tumor bed questions the need for protracted elective WBI, and provides the rationale for accelerated-partial-breast irradiation (APBI) of small cancers without adverse features predisposing to multicentric recurrence. APBI can be given over a week with various external beam, intraoperative or brachytherapy (interstitial or MammoSite) techniques. Since the approval of MammoSite by the US FDA in May 2002, a surge of interest has been evident, with 4,000 cases treated using this technique in the past 2 years. Several phase II APBI brachytherapy studies show that 4 to 7-year breast control rates (95%), survival and cosmetic outcome obtained from more than 600 appropriately selected women are comparable to matched or historic controls receiving WBI. The 2 to 3-year interim results of two ongoing randomized trials do not show any early detriment with APBI. If mature results of randomized trials confirm equivalence of APBI to conventional WBI in selected women, it would mark a paradigm shift and a major advance in treatment. This would allow many more women to opt for breast conservation, resolve the dilemmas regarding chemotherapy and radiotherapy sequencing and perhaps would be more cost effective.

Acute Toxicity of High-Dose-Rate Intracavitary Brachytherapy With the MammoSite Applicator in Patients With Early-Stage Breast Cancer

BACKGROUND

Intracavitary brachytherapy with the MammoSite applicator as the sole radiation treatment in breast-conserving therapy is an option for women with early-stage breast cancer; we evaluated the acute toxicities associated with this treatment method.

METHODS

Thirty-one patients with 32 stage I or II breast carcinomas underwent breast-conserving therapy, which included lumpectomy with negative margins, sentinel node biopsy, or axillary dissection, followed by brachytherapy with the MammoSite applicator. Acute radiation skin complications were graded on the day of radiotherapy completion and at weeks 2, 4, 6, and 12 after radiation treatment. Cosmesis was graded on the Harvard Scale at all follow-ups.

RESULTS

The median follow-up was 11 months (range, 4-15 months). Twenty-seven of the 31 patients were treated with the device as the sole method of radiotherapy. No acute toxicities occurred during the 5 days of treatment. Nineteen patients (68%) had no to mild acute skin reactions, and 25% developed bright erythema and patchy moist desquamation. Two patients (7%) developed confluent moist desquamation within the first 4 weeks (grade 3); this healed by week 12. All skin reactions were localized to the area overlying the balloon. Sixteen percent (5 of 32) of all breasts with implants developed infection. Cosmesis was good to excellent in 86% of cases.

CONCLUSIONS

Most acute skin toxicities were mild. Our infection rate was higher than in prior studies that used interstitial brachytherapy. Cosmesis was good to excellent in most patients. Breast brachytherapy with the MammoSite catheter was well tolerated; further investigations of breast brachytherapy with this system are warranted.