International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationAccelerated Partial Breast Irradiation Is Safe and Effective Using Intensity-Modulated Radiation Therapy in Selected Early-Stage Breast Cancer
Introduction
In the past several decades, there has been a significant paradigm shift in the management of early-stage breast cancers. Mounting long-term evidence from prospective randomized trials has demonstrated that breast-conserving surgery (BCS) followed by whole breast external-beam radiation therapy is comparable to mastectomy in terms of overall and disease-free survival 1, 2. Routine management of Stage I and II breast cancers today consists of BCS followed by 5 to 7 weeks of daily whole-breast radiation therapy (WBRT) to achieve a dose of approximately 45 to 50 Gy, often followed by a boost to the lumpectomy cavity (3). Although the major advantages of BCS followed by WBRT include a superior cosmetic result and decreased emotional and psychologic trauma associated with a mastectomy, a major drawback is the prolonged overall treatment time as compared with a more definitive surgical approach.
More recent data have revealed that the vast majority of ipsilateral breast tumor recurrences (IBTR) occur at or near the site of the original primary tumor, often within the lumpectomy cavity 1, 4, 5. Therefore, irradiating the entire breast volume to treat subclinical disease may not necessarily be of benefit. These findings consequently have led to a growing interest in adjuvant partial breast irradiation to treat the area at highest risk for recurrence. Given that only a small volume of the breast is to be treated, it is hypothesized to be safe to deliver larger doses of local radiation therapy in an accelerated schedule. This method, termed accelerated partial breast irradiation (APBI), can additionally address the logistic issues associated with a prolonged radiation treatment schedule, which sometimes precludes patients from receiving adjuvant radiation therapy (6).
Several techniques to deliver APBI have been implemented, including intraoperative radiation therapy and both catheter and balloon interstitial brachytherapy 6, 7, 8. However, these are often technically challenging procedures, which also require the patient to undergo an additional invasive procedure and to be placed at an increased risk of infection. In the case of low-dose-rate (LDR) brachytherapy, the patient must also remain hospitalized, which further increases the risk of complications. With high-dose-rate (HDR) techniques or with newer balloon-based interstitial techniques, patients remain with a catheter in place for the duration of therapy. With the advent of three-dimensional treatment planning and highly conformal delivery of external-beam irradiation to deliver a homogenous dose distribution, there has naturally followed a growing interest in delivering APBI using noninvasive modalities. The ongoing Phase III Radiation Therapy Oncology Group (RTOG) 0413/NSABP B-39 is assessing the efficacy of APBI using the aforementioned techniques; however, external-beam delivery is limited to three-dimensional conformal planning (9).
Intensity-modulated radiation therapy (IMRT) further improves on three-dimensional conformal planning techniques by using inverse planning algorithms for optimal dose delivery to the target volume while improving the sparing of surrounding normal tissues (9). Additionally, using modern respiratory gating techniques to improve precision of target dose delivery, it is considerably safer to deliver higher doses per fraction using external-beam radiation therapy. In this study, we sought to evaluate the safety, feasibility, and clinical efficacy of delivering APBI using IMRT in selected early-stage breast cancers.
Section snippets
Patient selection and eligibility
Thirty-six patients elected to receive adjuvant APBI using IMRT with respiratory gating after BCS at Baptist Hospital in Miami, Florida, from 2003 until 2009. All patients were prospectively enrolled in an institutional review board approved protocol with informed consent before beginning treatment. The primary endpoints of the study were technical feasibility, toxicity, and cosmetic outcome of APBI using IMRT to the tumor bed alone in patients with early-stage breast cancers undergoing BCS
Results
All patients enrolled met the eligibility criteria as outlined in Methods and Materials. The patient characteristics for all enrolled patients are shown in Table 1. The median age of the 36 patients was 68 years (range, 50–84 years). A significant majority of patients included were white (34/36). Thirty-five of 36 (97%) patients were postmenopausal, and 1 patient was premenopausal. Twenty-three (64%) patients presented with right-sided tumors, and 13 (36%) had left-sided tumors. The median
Discussion
In this study, we have shown the feasibility, safety, and clinical outcomes of delivering APBI using IMRT, a more sophisticated dose-delivery system than three-dimensional conformal radiation therapy. The advantages offered by IMRT have been most clearly realized in sites such as the head and neck, prostate, and central nervous system when tumors often lie adjacent to critical normal structures 13, 14. In the case of APBI, it becomes crucial to deliver a conformal and homogenous dose
Conclusions
We have shown that APBI can be safely and effectively delivered via an IMRT technique for selected breast cancer patients. At a median follow-up time of nearly 4 years, we have shown acceptable local recurrence rates, with minimal acute toxicity and good to excellent cosmesis as rated by physicians and patients. When our data are compared with other similar studies, our results suggest that cosmesis in the setting of APBI via IMRT seems to be highly sensitive to the target volume size, which is
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Conflict of interest: none.