Technology Insight: MammoSite®—a new device for delivering brachytherapy following breast-conserving therapy

Breast conservation therapy utilizing partial breast brachytherapy for early-stage cancer of the breast: a retrospective review from the Saint Luke's Cancer Institute

BACKGROUND

Accelerated partial breast irradiation (APBI) is a convenient alternative to whole-breast irradiation, as less overall time is needed for completion. The use of APBI outside the framework of large prospective clinical trials has markedly increased. To our knowledge, no high-volume, community-based breast program has published their experience with APBI.

METHODS

The records of 93 consecutive patients who underwent APBI utilizing Mammosite Radiation Therapy System from 2005 to 2010 at Saint Luke's Cancer Institute in Kansas City, MO, were retrospectively reviewed. The Kaplan-Meier method was used to estimate the ipsilateral breast recurrence rate and recurrence-free survival.

RESULTS

Median age at diagnosis was 63 years (range, 45 to 86 y) and mean follow-up was 29 months. Patient stratification ASTRO consensus classifications for APBI was 37% suitable, 57% cautionary, and 6% unsuitable. The 3-year breast control rate was 98.7%. Three-year overall recurrence-free survival was 94.4%, and 3-year mastectomy-free survival was 97.4%. Using univariate analysis, no tumor or patient factors were associated with ipsilateral breast recurrence. However, tumor grade (P<0.05), stage (P=0.04), estrogen receptor status (P<0.001), progesterone receptor status (P<0.001), tumor size (P<0.001), and ASTRO suitability criteria (P=0.027) were associated with overall recurrence-free survival. No differences were observed when outcomes of patients with ductal carcinoma in situ were compared with those with invasive disease.

CONCLUSIONS

In our high-volume community-based program, APBI outcomes are comparable with those reported from large academic institutions. We also found relationships between tumor stage, grade, negative estrogen receptor status, and ASTRO suitability criteria with overall recurrence rates. The continued careful application of APBI in appropriately selected patients appears warranted until phase III trials comparing this modality to whole-breast irradiation have matured.

Accelerated partial breast irradiation using the strut-adjusted volume implant single-entry hybrid catheter in brachytherapy for breast cancer in the setting of breast augmentation

PURPOSE

Accelerated partial breast irradiation (APBI) has gained popularity as an alternative to adjuvant whole breast irradiation; however, owing to limitations of delivery devices for brachytherapy, APBI has not been a suitable option for all the patients. This report evaluates APBI using the strut-adjusted volume implant (SAVI) single-entry catheter to deliver brachytherapy for breast cancer in the setting of an augmented breast.

METHODS AND MATERIALS

The patient previously had placed bilateral subpectoral saline implants; stereotactic core biopsy revealed estrogen receptor- and progesterone receptor-positive ductal carcinoma in situ of intermediate nuclear grade. The patient underwent needle-localized segmental mastectomy of her left breast; pathologic specimen revealed no residual malignancy. An SAVI 8-1 device was placed within the segmental resection cavity. Treatment consisted of 3.4 Gy delivered twice a day for 5 days for a total dose of 34 Gy. Treatments were delivered with a high-dose-rate (192)Ir remote afterloader.

RESULTS

Conformance of the device to the lumpectomy cavity was excellent at 99.2%. Dosimetric values of percentage of the planning target volume for evaluation receiving 90% of the prescribed dose, percentage of the planning target volume for evaluation receiving 95% of the prescribed dose, volume receiving 150% of the prescribed dose, and volume receiving 200% of the prescribed dose were 97.1%, 94.6%, 22.7 cc, and 11.6 cc, respectively. Maximum skin dose was 115% of the prescribed dose. The patient tolerated treatment well with excellent cosmetic results, and limited acute and late toxicity at 8 weeks and 6 months, respectively.

CONCLUSIONS

Breast augmentation should not be an exclusion criterion for the option of APBI. The SAVI single-entry catheter is another option to successfully complete APBI using brachytherapy for breast cancer in the setting of an augmented breast.

Xoft Axxent electronic brachytherapy: a new device for delivering brachytherapy to the breast

Balloon-based brachytherapy was developed to simplify the brachytherapy technique and make accelerated partial breast irradiation more accessible to patients with breast cancer who are suitable candidates for this technique. Xoft Axxent (Xoft, Inc., Sunnyvale, CA) electronic brachytherapy is a novel method of accelerated partial breast irradiation that uses an electronic source to produce X-rays. Xoft Axxent treatment does not require a high-dose-rate afterloader unit or a shielded vault, unlike other brachytherapy techniques that use iridium-192, such as MammoSite brachytherapy. Xoft Axxent is associated with the delivery of less radiation to normal tissues, and increased high radiation dose regions or 'hot spots' to the target volume compared with treatment with the MammoSite device. Further research will be needed to determine subgroups of patients who might benefit from treatment with Xoft Axxent electronic brachytherapy.

Hypofractionated and accelerated radiotherapy with subcutaneous amifostine cytoprotection as short adjuvant regimen after breast-conserving surgery: interim report

PURPOSE

Short radiotherapy schedules might be more convenient for patients and overloaded radiotherapy departments, provided late toxicity is not increased. We evaluated the efficacy and toxicity of a hypofractionated and highly accelerated radiotherapy regimen supported with cytoprotection provided by amifostine in breast cancer patients treated with breast-conserving surgery.

METHODS AND MATERIALS

A total of 92 patients received 12 consecutive fractions of radiotherapy (3.5 Gy/fraction for 10 fractions) to the breast and/or axillary/supraclavicular area and 4 Gy/fraction for 2 fractions to the tumor bed). Amifostine at a dose of 1,000 mg/d was administered subcutaneously. The follow-up of patients was 30-60 months (median, 39).

RESULTS

Using a dose individualization algorithm, 77.1% of patients received 1,000 mg and 16.3% received 750 mg of amifostine daily. Of the 92 patients, 13% interrupted amifostine because of fever/rash symptoms. Acute Grade 2 breast toxicity developed in 6.5% of patients receiving 1,000 mg of amifostine compared with 46.6% of the rest of the patients (p < .0001). The incidence of Grade 2 late sequelae was less frequent in the high amifostine dose group (3.2% vs. 6.6%; p = NS). Grade 1 lung fibrosis was infrequent (3.3%). The in-field relapse rate was 3.3%, and an additional 2.2% of patients developed a relapse in the nonirradiated supraclavicular area. c-erbB-2 overexpression was linked to local control failure (p = .01). Distant metastasis appeared in 13% of patients, and this was marginally related to more advanced T/N stage (p = .06).

CONCLUSION

Within a minimal follow-up of 2.5 years after therapy, hypofractionated and accelerated radiotherapy with subcutaneous amifostine cytoprotection has proved a well-tolerated and effective regimen. Longer follow-up is required to assess the long-term late sequelae.

Late chest wall toxicity after MammoSite breast brachytherapy

PURPOSE

Accelerated partial breast irradiation (APBI) with the MammoSite breast brachytherapy (MBB) system is being investigated as an alternative to whole breast radiation in breast conservation therapy (BCT) at multiple centers worldwide. The newness of MBB means a complete understanding of long-term toxicity, particularly involving the chest wall, has yet to be completely articulated. We report the first pathologic rib fractures associated with MBB and dosimetric analysis of the original treatment plans.

METHODS AND MATERIALS

As part of ongoing quality assurance, we reviewed the records of 129 sequential patients who underwent MBB for breast cancer and identified those who subsequently had clinically significant and radiographically documented rib fracture(s) involving the ipsilateral chest wall. Equivalent tolerance doses yielding a 5% and 50% risk of rib toxicity within 5 years from treatment with 10 fractions (as with MBB) were previously calculated using the linear quadratic equation based on 2Gy per fraction treatments delivered to one-third of the rib volume (TD5/5=37Gy; TD50/5=44Gy). The original radiation therapy plans were evaluated vis-à-vis the plane films or PET/CT images documenting the osseous abnormalities and presenting complaints to find the specific fractured ribs. The specific effected ribs were contoured on the planning CT in "bone windows" using the Nucletron MicroSelectron-classic V2 (Nucletron B.V., Veenendaal, The Netherlands) for this analysis and the original patient treatments. With these datasets, we determined the dose-volume characteristics of the effected ribs including maximal dose encompassing the entire rib on one CT slice, V(20Gy), V(30Gy), V(37Gy), V(44Gy), D(50), D(25), and D(5) (the mean dose to 50%, 25%, and 5% of the rib).

RESULTS

Between May 2002 and August 2007, three of 105 patients with a minimum of 6-months follow-up who underwent adjuvant APBI by MBB were found to have a total of five treatment-related rib fractures. The average dose-volume characteristics from the original plans were as follows: D(50)=22.1Gy, D(25)=32.2Gy, D(5)=41.6Gy, max dose to 1cc=34.8, D(max) (to 0.1cc)=45.6Gy, V(20)Gy=57.4%, V(30)Gy=30.8%, V(37)Gy=15.9%, V(44)Gy=6.6%, and max dose through rib=35.8Gy. Two patients sustained two rib fractures and 1 patient had a single rib fracture. Four of five fractures occurred in postmenopausal patients and two of five fractures occurred in a patient with a history of osteoporosis and exposure to adjuvant chemotherapy.

CONCLUSIONS

Fractures occurred in ribs with V(37)Gy and V(44)Gy each well below 33%. As long-term toxicity data accrue from APBI series, the traditional models for estimating the biologic equivalent dose may benefit from refinements that specifically address the unique radiobiologic and physical properties intrinsic to high-dose-rate brachytherapy for breast conservation therapy.