What are the suitable criteria for accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer?

Suitable Criteria for Accelerated Partial Breast Irradiation

Accelerated partial breast irradiation (APBI) is an acceptable treatment option for patients who are at least 50 years old with unicentric, unifocal, node-negative, non-lobular breast cancer measuring up to 3 cm, without extensive intraductal components or vascular invasion, with negative margins, and especially if they will receive adjuvant endocrine treatment. 1

Patient Selection Criteria for APBI

The most recent guidelines provide specific criteria for identifying suitable candidates for APBI:

NCCN Criteria (2016-2017):

• Age ≥50 years with invasive ductal carcinoma measuring ≤2 cm (T1 disease) 1
• Negative surgical margins by ≥2 mm 1
• No lymphovascular space invasion (LVSI) 1
• Hormone receptor-positive disease 1
• BRCA-negative status 1
• Low to intermediate grade screen-detected DCIS measuring ≤2.5 cm with negative margins by ≥3 mm (also suitable) 1

ESMO Criteria (2019):

• Age ≥50 years 1
• Unicentric, unifocal disease 1
• Node-negative status 1
• Non-lobular histology 1
• Tumor size up to 3 cm 1
• No extensive intraductal components 1
• No vascular invasion 1
• Negative surgical margins 1
• Adjuvant endocrine treatment (preferred) 1
• Low-grade DCIS may also be considered 1

Treatment Delivery Options

APBI can be delivered through various techniques:

Brachytherapy:

• Recommended dose: 34 Gy in 10 fractions delivered twice per day 1

External Beam Radiation Therapy:

• Recommended dose: 38.5 Gy in 10 fractions delivered twice per day 1

Other Approaches:

• Intraoperative radiation therapy (IORT) techniques like ELIOT (electrons) and TARGIT (50-kV X-rays) have shown higher ipsilateral breast recurrence rates compared to whole breast radiation therapy 1

Rationale for APBI

The concept behind APBI is based on clinical observations that:

• The majority of local recurrences occur in the vicinity of the primary tumor site 1
• "Elsewhere" in-breast failures may represent new primary tumors rather than true recurrences 1
• APBI substantially shortens the overall treatment time compared to whole breast irradiation 1

Efficacy and Outcomes

Recent evidence demonstrates:

• Excellent results with low local recurrence rates equivalent to whole breast radiation therapy have been reported for partial-breast irradiation using external beam techniques and brachytherapy 1
• The NCCN panel generally views APBI as investigational and encourages its use within high-quality, prospective clinical trials 1
• For patients who are not trial-eligible, APBI may be suitable in selected patients with early-stage breast cancer 1

Important Considerations and Caveats

• Patient selection is critical for successful outcomes with APBI
• Some studies suggest that the ASTRO stratification guidelines may not adequately predict ipsilateral breast tumor recurrences following APBI 1
• Follow-up in many studies remains limited, and ongoing research continues to refine selection criteria 1
• Intraoperative radiation therapy techniques (ELIOT and TARGIT) have shown significantly higher ipsilateral breast cancer recurrence rates compared to whole breast radiation therapy 1
• APBI should not be used in patients with BRCA1/2 mutations 1
• The NCCN panel accepts the updated 2016 version of the ASTRO APBI consensus statement for patient selection 1

By carefully selecting patients according to these criteria, APBI offers a convenient and effective alternative to whole breast irradiation for early-stage breast cancer patients, with treatment completed in 4-5 days rather than the conventional 3-6 weeks required for whole breast irradiation.