Accelerated Partial Breast Irradiation Via Interstitial Brachytherapy as the Sole Radiation Modality for Treatment of Early-Stage Breast Cancer

Reviewer: Roberto Santiago, MD
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Ultima Vez Modificado: 11 de octubre del 2002

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Presenter: Peter Y. Chen
Presenter's Affiliation: Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI
Type of Session: Scientific

Background

    In several randomized clinical trials BCT including whole breast irradiation has been found to yield equivalent survival rates when compared to mastectomy in patients with early carcinoma of the breast. This ?conventional? BCT confers high local control rates and good cosmetic results with acceptable toxicity in the majority of these patients. However, some investigators feel the need for whole breast irradiation is unclear. This study evaluates the local control, patterns of failure, cosmesis and survival in selected patients with early-stage breast cancer treated with partial breast brachytherapy over 4-5 days as the sole radiation modality.

Materials and Methods

  • Two hundred seven women with early-stage breast cancer were entered between January 1993 and December 2001 into three protocols of tumor bed irradiation alone using either an interstitial LDR (n=128) or HDR (n=79) implant.
  • Patients were eligible if their tumor was an invasive ductal carcinoma 3cm in diameter, surgical margins were clear by at least 2 mm, the tumor did not contain an extensive intraductal component, the axilla was surgically staged with 3 nodes involved with cancer and no residual mammographic calcifications noted on post-operative imaging.
  • After the first 50 patients entered, the protocol was amended so that no positive nodes were allowed.
  • The interstitial implants were positioned using a template guide.
  • 128 patients were treated on an inpatient basis with a LDR iodine implant that delivered 50 Gy over 96 hours at a rate of 0.52 Gy per hour.
  • The remaining patients were treated on an outpatient basis with a HDR implant that delivered 32 Gy in 8 twice-daily fractions (68 patients) each separated by a minimum of 6 hours or 34 Gy in 10 twice-daily fractions each separated by 6 hours (11 patients).
  • Both, open cavity (usually during lumpectomy) and closed cavity (usually as a separate procedure) techniques were used. Every implant was designed to irradiate the lumpectomy cavity plus a 1-2 cm margin.
  • Intraoperative US and CT treatment planning were used to improve the implant quality.
  • Thirteen percent received adjuvant systemic chemotherapy and 60% received adjuvant Tamoxifen.

Results

  • Median age of the women was 65 years
  • 92% of patients had T1 tumors, 39% had tumors < 10 mm in diameter, 86% were N0, and 56% had margins > 10 mm.
  • One half of the implants were done with an open technique. 59% had a triple plane implants and 37% had more than 15 catheters inserted. Median follow-up on all patients was 5 years
  • 5 patients had ipsilateral breast recurrences consisting of 2 true recurrences/marginal misses and 3 elsewhere recurrences. One of these patients had synchronous regional and distant failure.
  • Time to failure ranged from 1.5 to 7.6 years and the median time to elsewhere breast failure was 5 years (range, 2.6-6.8 years).
  • The 5-year actuarial local failure rate was 1.2%. The 5-year actuarial isolated local failure rate was 0.6%. Regional recurrence (RR) occurred in 2 patients at a median time of 1.6 years for a 5-year actuarial RR rate of 1.1%.
  • Six patients failed distantly for a 5-year actuarial rate of 4.8%. Five-year actuarial cause specific survival was 97%.
  • All local failures were successfully salvaged by mastectomy except for the patient who had synchronous regional and distant failure.
  • The only chronic toxicity was telangectasia usually at the insertion site in 30% of LDR and 24% of HDR patients.
  • Good to excellent cosmetic results were observed in 91% of LDR and 98% of HDR patients. Asymptomatic fat necrosis was observed in 19% of LDR and 8% of HDR patients.

Author's Conclusions

  • In properly selected patients APBI via interstitial brachytherapy technique, either LDR or HDR, offers 5-year results comparable to conventional BCT with whole breast irradiation in early stage breast cancer.
  • Extended follow-up will be required to determine the long-term efficacy of this treatment approach.

Clinical/Scientific Implications

  • Newer PBI techniques using 3-D conformal quadrant irradiation, IMRT, or novel brachytherapy applicators should be investigated.
  • There is a paucity of efficacy data from randomized trials comparing this or similar PBI approaches to conventional whole breast irradiation for breast conservation therapy in early stage breast cancer. These randomized trials would provide very important information but will require a long follow-up (10-15 years) before meaningful conclusions can be drawn.
  • These techniques have a learning curve probably requiring special training and experience.
  • PBI could be a reasonable approach for highly selected patients with limited access to conventional BCT practices due to time or transportation issues.
  • The use of PBI should be limited highly selected patients in the clinical trial setting.

Oncolink's ASTRO Coverage made possible by an unrestricted Educational Grant from Ortho Biotech.

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