International Journal of Radiation Oncology*Biology*Physics
Physics ContributionAccelerated Partial-Breast Intensity-Modulated Radiotherapy Results in Improved Dose Distribution When Compared With Three-Dimensional Treatment-Planning Techniques
Introduction
The use of conservative surgery combined with whole-breast irradiation (WBI) has been established as a valid alternative to mastectomy for the local treatment of ductal carcinoma in situ and early invasive breast cancer. Recently updated 20-year results of breast-conservation therapy trials have shown comparable overall survival and disease-free survival results for limited surgery and WBI compared with mastectomy 1, 2, 3, 4.
Despite the efficacy of breast-conservation therapy in the treatment of early breast cancer, only 10–40% of patients who qualify for breast-conservation therapy are treated in this manner (5). In addition, a study querying the Surveillance, Epidemiology, and End Results database estimates that up to 25% of patients who are treated with breast-conservation surgery do not receive adjuvant radiotherapy (6). Breast-conservation therapy is time consuming, with WBI requiring 5–7 weeks to complete. Moreover, there has been a trend toward use of adjuvant chemotherapy after lumpectomy, delaying the start of radiotherapy (RT) (5). Although early delivery of chemotherapy is favored, the associated delay of conventional WBI negatively impacts local control (7).
Thus, accelerated partial-breast irradiation (APBI) offers potential advantages, allowing the completion of RT in 1 to 2 weeks, typically before the start of adjuvant chemotherapy. Several investigators have evaluated both low-dose-rate 8, 9, 10, 11, 12, 13, 14 and high-dose-rate brachytherapy 8, 14, 15, 16, 17, 18, 19, 20 and have demonstrated 5-year disease-free survival rates similar to those of historical controls. External beam RT (EBRT) has recently been established as an option in the delivery of APBI. The use of three-dimensional conformal radiotherapy (3D-CRT) has been tested in two Phase I/II clinical trials 21, 22, 23, 24, 25 and represents the most frequently used option for APBI in the Phase III National Surgical Adjuvant Breast and Bowel Project (NSABP) B39/Radiation Therapy Oncology Group (RTOG) 0413 randomized trial (26).
Intensity-modulated RT (IMRT) potentially offers further improvement in normal tissue sparing. Studies in prostate and head-and-neck cancer have shown that IMRT allows further dose reduction to normal tissues compared with 3D-CRT 27, 28. If the use of IMRT confers a significant reduction in uninvolved breast irradiation, then a reduction in the incidence of late toxicity and poor cosmetic outcomes may be achievable.
The current analysis compares target volume and normal tissue radiation doses using 3D-CRT vs. IMRT from an initial cohort of patients treated on a Phase II accelerated partial-breast IMRT protocol.
Section snippets
Patients
Sixty-three patients with T1N0 or ductal carcinoma in situ breast cancer were treated on a Phase II prospective accelerated partial-breast IMRT protocol at two facilities between April 2004 and January 2006. Eligibility requirements were a minimum age of 45 years, staged as a T1, N0, M0 Stage I American Joint Committee on Cancer classification (later amended to include patients with a minimum age of 40 years and to include Tis) and negative surgical margins (≥2 mm) after final surgery.
Treatment planning
Two
Ipsilateral breast
The maximum delivered dose was similar for IMRT and 3D-CRT. The mean Dmax as a percentage of the prescribed dose was 105.1% with IMRT and 105.8% with 3D-CRT. The present analysis showed a statistically significant reduction in the dose delivered to the IB favoring IMRT, particularly at the higher dose levels, as presented in Table 1. The mean volume of IB receiving 25% (V25), 50% (V50), 75% (V75), and 100% (V100) was reduced by 7%, 11%, 15%, and 53%, respectively, with IMRT compared with 3D
Discussion
The present analysis evaluated a cohort of 56 early-stage breast cancer patients planned for APBI with both 3D-CRT and IMRT planning techniques. Averaging all patients, the use of IMRT was associated with a reduction in dose and volume of normal breast irradiated.
The observation that IMRT has its greatest benefit at higher doses may be influential in decreasing toxicity. Skin tolerance to radiation as reported by Emani et al. is 30–40 Gy (30). In the setting of a hypofractionated accelerated
Acknowledgment
The authors thank Angel Sandoval, C.M.D., for assistance with treatment-planning calculations.
References (31)
- et al.
Radiotherapy in breast-conserving treatment for ductal carcinoma in situ: First results of the EORTC randomised phase III trial 10853. EORTC Breast Cancer Cooperative Group and EORTC Radiotherapy Group
Lancet
(2000) - et al.
Relation between appropriateness of primary therapy for early-stage breast carcinoma and increased use of breast-conserving surgery
Lancet
(2000) - et al.
Long-term results of wide-field brachytherapy as the sole method of radiation therapy after segmental mastectomy for T (is,1,2) breast cancer
Am J Surg
(2000) - et al.
Inadequacy of iridium implant as sole radiation treatment for operable breast cancer
Eur J Cancer
(1996) - et al.
Iridium implant treatment without external radiotherapy for operable breast cancer: A pilot study
Eur J Cancer
(1991) - et al.
Partial breast brachytherapy after lumpectomy: Low-dose-rate and high-dose-rate experience
Int J Rad Oncol Biol Phys
(2003) - et al.
Method of localization and implantation of the lumpectomy site for high dose rate brachytherapy after conservative surgery for T1 and T2 breast cancer
Int J Rad Oncol Biol Phys
(1995) - et al.
The use of high-dose-rate brachytherapy alone after lumpectomy in patients with early stage breast cancer treated with breast-conserving therapy
Int J Radiat Oncol Biol Phys
(2001) - et al.
Preliminary results of a Phase I/II study of HDR brachytherapy alone for T1/T2 breast cancer
Int J Radiat Oncol Biol Phys
(2002) - et al.
Caesium (137) implant as sole radiation therapy for operable breast cancer: A phase II trial
Radiother Oncol
(2004)
Ongoing clinical experience utilizing 3D conformal external beam radiotherapy to deliver partial-breast irradiation in patients with early-stage breast cancer treated with breast conserving therapy
Int J Radiat Oncol Biol Phys
Prone accelerated partial breast irradiation after breast-conserving surgery: Preliminary clinical results and dose-volume histogram analysis
Int J Radiat Oncol Biol Phys
A Phase I/II trial to evaluate three-dimensional conformal radiation therapy confined to the region of the lumpectomy cavity for stage I/II breast carcinoma: Initial report of feasibility and reproducibility of Radiation Therapy Oncology Group (RTOG) study 0319
Int J Radiat Oncol Biol Phys
Reduction of small and large bowel irradiation using an optimized intensity-modulated pelvic radiotherapy technique in patients with prostate cancer
Int J Radiat Oncol Biol Phys
Three-dimensional conformal vs. intensity-modulated radiotherapy in head-and-neck cancer patients: Comparative analysis of dosimetric and technical parameters
Int J Radiat Oncol Biol Phys
Cited by (0)
Supported by Rocky Mountain Cancer Centers, Denver, CO.
Presented in poster form at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), November 5–9, 2006, Philadelphia, PA.
Conflict of interest: none.