Accelerated Partial Breast Irradiation (APBI): A review of available techniques

Breast conservation therapy (BCT) is the procedure of choice for the management of the early stage breast cancer. However, its utilization has not been maximized because of logistics issues associated with the protracted treatment involved with the radiation treatment. Accelerated Partial Breast Irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin, rather than the whole breast. Hence because of the small volume of irradiation a higher dose can be delivered in a shorter period of time. There has been growing interest for APBI and various approaches have been developed under phase I-III clinical studies; these include multicatheter interstitial brachytherapy, balloon catheter brachytherapy, conformal external beam radiation therapy and intra-operative radiation therapy (IORT). Balloon-based brachytherapy approaches include Mammosite, Axxent electronic brachytherapy and Contura, Hybrid brachytherapy devices include SAVI and ClearPath. This paper reviews the different techniques, identifying the weaknesses and strength of each approach and proposes a direction for future research and development. It is evident that APBI will play a role in the management of a selected group of early breast cancer. However, the relative role of the different techniques is yet to be clearly identified

A phase II trial of balloon-catheter partial breast brachytherapy optimization in the treatment of stage 0, I, and IIA breast carcinoma

OBJECTIVE(S): (a) To prospectively determine if multidwell position dose delivery can decrease skin dose and resultant toxicity over single dwell balloon-catheter partial breast irradiation, and (b) to evaluate whether specific skin parameters could be safely used instead of skin-balloon distance alone for predicting toxicity and treatment eligibility. METHODS: A single-arm phase II study using a Simon two-stage design was performed on 28 women with stage 0-II breast cancer. All patients were treated with multiple dwell position balloon-catheter brachytherapy. The primary endpoint was ≥ grade 2 skin toxicity. Initial entry required a balloon-skin distance ≥ 7 mm. Based on the toxicity in the first 16 patients, additional patients were treated irrespective of skin-balloon distance as long as the Dmax to 1 mm skin thickness was < 130%. RESULTS: Compared to the phantom single dwell plans, multidwell planning yielded superior PTV coverage as per median V90, V95 and V100, but had slightly worse V150, V200 and DHI. Dmax to skin was decreased by multidwell planning at multiple skin thicknesses. The most common acute toxicity was grade 1 erythema (57%), and only two patients (7%) developed acute grade 2 toxicity (erythema). Late grade 1 fibrosis was seen in 32%. No patients experienced grade 3, 4, or 5 toxicity. CONCLUSIONS: Multidwell position planning for balloon-catheter brachytherapy results in lower skin doses with equal to superior PTV coverage and an overall low rate of initial skin toxicity. Our data suggest that limiting the Dmax to < 130% to 1 mm thick skin is achievable and results in minimal toxicity

Review of MammoSite brachytherapy: Advantages, disadvantages and clinical outcomes

Background: The MammoSite† radiotherapy system is an alternative treatment option for patients with early-stage breast cancer to overcome the longer schedules associated with external beam radiation therapy. The device is placed inside the breast surgical cavity and inflated with a combination of saline and radiographic contrast to completely fill the cavity. The treatment schedule for the MammoSite monotherapy is 34 Gy delivered in 10 fractions at 1.0 cm from the balloon surface with a minimum of 6 hours between fractions on the same day. Material and methods: This review article presents the advantages, disadvantages, uncertainties and clinical outcomes associated with the MammoSite brachytherapy (MSB). Results: Potential advantages of MSB are: high localised dose with rapid falloff for normal tissue sparing, minimum delay between surgery and RT, catheter moves with breast, improved local control, no exposure to staff, likely side-effects reduction and potential cost/time saving (e.g. for country patients). The optimal cosmetic results depend on the balloon-toskin distance. Good-to-excellent cosmetic results are achieved for patients with balloon-skin spacing of ]7 mm. There have been very few published data regarding the long term tumour control and cosmesis associated with the MSB. The available data on the local control achieved with the MSB were comparable with other accelerated partial breast irradiation techniques. The contrast medium inside the balloon causes dose reduction at the prescription point. Current brachytherapy treatment planning systems (BTPS) do not take into account the increased photon attenuation due to high Z of contrast. Some BTPS predicted up to 10% higher dose near the balloon surface compared with Monte Carlo calculations using various contrast concentrations (5.25%). Conclusion: Initial clinical results have shown that the MammoSite device could be used as a sole radiation treatment for selected patients with early stage breast cancer providing good local control, minimal complication rate and excellent cosmesis.Saleh Bensaleh, Eva Bezak and Martin Bor