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Multicatheter brachytherapy linked to long-term disease control rates
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SAN FRANCISCO — The 10-year regional failure rate associated with multicatheter brachytherapy in a cohort of patients with stage I/II breast cancer was slightly higher than 5%, according to results of a phase 2 study.
The findings suggest the treatment method has “durable local regional cancer control rates,” the researchers wrote.
Researchers investigated multicatheter brachytherapy, which is one of the earliest methods of accelerated partial breast irradiation, in a cohort of 98 patients with stage I/II unifocal breast cancer <3 cm. Eligibility criteria included invasive non-lobular histology without extensive intraductal component, negative surgical margins, 0-3 positive axillary nodes and no extracapsular extension.
Target volume was the lumpectomy cavity plus a 2 cm radial and 1 cm anterior/posterior margin, the researchers said.
The investigators defined a low radiation dose as 45 Gy in 3.5-5 days. They defined a high dose as 34 Gy in 10 twice-daily fractions over 5 days.
Study protocols called for a rapid dosimetry review to assure dose delivery. Physicians were granted latitude to initiate systemic therapy upon discretion.
Multicatheter brachytherapy reproducibility with low- or high-dose radiation served as the primary outcome measure. Other endpoints included ipsilateral breast failure, contralateral breast cancer events, regional and distant failure, DFS, relapse-free survival (RFS) and OS.
The researchers enrolled 100 patients between 1997 and 2000. Median follow-up was 12.1 years. Of the 98 evaluable patients, 33 received low-dose radiation and 65 received high-dose radiation.
The median patient age was 62 years. Eighty-eight percent had T1 tumors and 12% had T2 tumors. Eighty-one percent were node negative and 19% were node positive. Seventy-seven percent of patients were ER- and/or PR-positive , whereas 19% were ER- and PR-negative.
Adjuvant chemotherapy was administered to 33% of patients, and 64% received anti-endocrine therapy.
The 10-year ipsilateral breast failure rate was 6.2%. Two ipsilateral breast failures occurred outside the accelerated partial breast irradiation field.
The regional failure rate at 10 years was 5.2%. The 10-year contralateral breast cancer event rate was 4.2%.
There were 21 total failures involving multiple failure patterns, including:
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four isolated intralateral breast failures
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one isolated regional failure
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eight distant failures
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one intralateral breast plus regional failure
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one intralateral breast plus regional plus distant failure
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one regional plus contralateral breast cancer events
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one regional plus distant failure
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three contralateral breast cancer events
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one contralateral breast cancer event plus distant failure.
Eleven patients developed distant failure. There were eight breast cancer deaths and 22 deaths from other causes.
At the 10-year mark, DFS was 69.8%, RFS was 71.9% and OS was 78.0%, study results showed.
For more information:
White JR. Abstract #147. Presented at: 2012 Breast Cancer Symposium; Sept. 13-15, 2012; San Francisco.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Bruce G. Haffty, MD
Accelerated partial breast irradiation (APBI), which delivers radiation following breast-conserving surgery to the tumor bed only, has gained popularity and continues to be evaluated in multiple trials throughout the world. It is important that patients and clinicians have confidence that, in appropriately selected patients, the long-term results of the concept of APBI are safe and effective. This phase 2 trial demonstrates the long-term effectiveness — with acceptable local control and survival rates — of the concept of APBI, pending the results of the ongoing phase 3 trials comparing the 1-week course of APBI with the standard 5- to 6-week course of daily whole breast irradiation.
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