DEFINING THE APPROPRIATE PATIENT POPULATION

Several professional groups established criteria for defining the appropriate candidates for PBI utilizing HDR, also called accelerated partial breast irradiation (APBI). The American Society of Breast Surgeons (ASBS) recommend that women with invasive ductal carcinoma who undergo PBI be 45 years or older, and women who undergo PBI for ductal carcinoma in situ (DCIS) be 50 years or older.14 Other recommendations include the tumor should be 3 cm or less, have negative microscopic surgical margins, and negative lymph nodes.13 The American Brachytherapy Society states women 45 years or older with unifocal invasive ductal carcinoma up to 3 cm with negative surgical margins and negative lymph nodes are appropriate candidates for APBI.15 However, the American Society for Radiation Oncology (ASTRO) created a consensus statement that categorizes patients as suitable, cautionary, or unsuitable candidates16 (Table 1). The unsuitable category was derived due to limited evidence for that patient population. The intent of the consensus panel was to refine recommendations as new evidence emerges.16

Table 1. ASTRO selection criteria for APBI16


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Suitable
All criteria are met
Cautionary
Presence of any of these criteria elicit caution
Unsuitable
If any of these criteria are present (outside of a clinical trial)
Age ≥60 years 50-59 years <50 years
Tumor size ≤2 cm 2.1-3.0 cm

• >3 cm

• T3-T4

• Multicentric

Foclaity Unifocal Unifocal with total size 2.1-3.0 cm

• Microscopic mulifocality

• >3 cm total size
Margins Negative by
≥2 mm
Close (<2 mm) Positive
Grade Any grade Not directly accessed Not directly accessed
Estrogen receptor status Positive Negative Not directly accessed
Histology Invasive ductal (or other favorable)

•  Invasive lobular DCIS ≤3cm 

• Extensive intraductal component
(≤3 cm)

• Pure DCIS
>3 cm

• Extensive intraductal component >3 cm

Lymphovascular space invasion None allowed Limited or focal Extensive
Node status N0 Not directly accessed

N1, N2, or N3, or no nodal surgery performed

Contraindications

• BRCA 1/2 mutation

• Pure DCIS or extensive intraductal component

 • Neoadjuvant chemotherapy

• BRCA 1/2 mutation

• Neoadjuvant chemotherapy

Key: APBI, accelerated partial breast irradiation; ASTRO, American Society for Radiation Oncology; DCIS, ductal carcinoma in situ.

Patel and colleagues compared ipsilateral breast tumor recurrence (IBTR) in the cautionary group with IBTR in the suitable group in women who underwent APBI within their practice.17 They found 8% of the women in the cautionary group experienced IBTR, whereas only 3% in the suitable category had IBTR within a median of 32 months. They also found a statistically significant increase in incidence of IBTR when the margins were cleared by less than 2 mm and in cases of grade III tumors.17

Vicini and colleagues identified 199 women who received WBI and 199 women who had PBI; stratified the women by the suitable (S), cautionary (C), and unsuitable (U) criteria. Then, assessed the rate of ipsilateral breast tumor recurrence.18 They found in these stratified groups there was no significant difference in IBTR rates for women at 10 years. However, regional nodal failure and distant metastasis was progressively worse when comparing the suitable, cautionary, and unsuitable groups.18 In this analysis which reviewed multiple variables, age at diagnosis was the only variable associated with IBTR in the whole breast irradiation group.18 Admittedly this was a smaller study, and validation from larger studies is necessary.

PLACEMENT OF AND TREATMENT WITH AN ALC

Currently, three temporary implanted afterloading catheters are available for APBI; which one is used is based on the surgeon’s preference. The MammoSite catheter (Hologic Inc; Danbury, Connecticut) was the first FDA-approved ALC. The first generation MammoSite catheter consisted of a single treatment lumen within a balloon (similar to that of a bladder catheter) that is inflated with saline and contrast medium. A later version of the MammoSite catheter has multiple treatment lumens within the balloon. The Contura (SenoRx; Tempe, Arizona) also has multiple lumens within the balloon. In addition, the Contura has a port from which to withdraw fluid, for example, from a seroma. The SAVI (Cianna Medical Inc; Aliso Viejo, California) is a strut adjusted volume implant device. Unlike the other two ALCs, the SAVI does not have a balloon. Rather, it has adjustable struts (similar to spokes) that also serve as the treatment lumens.

As with the choice of catheter, when it is placed is also determined by the surgeon. Zannis and colleagues reviewed outcomes of insertion techniques in a sample of 1,403 women.19 They described three opportunities for placing the ALC. The first option is at the time of excisional biospy, placing the ALC in the open cavity. The second option is after surgery, using ultrasonography to guide the device into a closed cavity. This option requires placing a cavitary expansion device (CED), or spacer balloon, at the time of surgery to ensure the cavity is prepared to receive the ALC at a later time. The third option is to place the ALC after surgery through the lumpectomy scar. Data from this registry trial showed catheter removal due to unfavorable pathology occurred at a statistically significant higher rate when the catheter was placed during surgery. The researchers concluded that catheters placed after histopathology was reviewed resulted in fewer unexpected or premature removals.19