International Journal of Radiation Oncology*Biology*Physics
Clinical investigation: breastOptimizing breast cancer treatment efficacy with intensity-modulated radiotherapy
Introduction
The proportion of patients with breast cancer treated with radiation therapy (RT) has increased substantially during the past two decades. Multiple, prospective, randomized trials have both established the equivalence of breast-conserving therapy to mastectomy in patients with early-stage disease, as well as documented a statistically significant improvement in cancer-specific survival with postmastectomy RT 1, 2, 3. Despite the documented importance of RT in the overall treatment of patients with breast cancer, normal tissue toxicities can limit the potential survival advantages of this treatment modality and reduce the overall quality of life of many patients 4, 5, 6. In recognition of the technical limitations of traditional RT in providing a safe and efficacious dose, three-dimensional (3D) treatment planning and intensity-modulated RT (IMRT) have recently been explored as possible mechanisms for improving RT delivery 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23. Several groups have demonstrated that these two technological advances have the capacity to improve RT delivery in most cancer patients (23). However, the practical application of these advanced technologies in the clinic on a large scale for the treatment of most women with breast cancer has proven difficult because of the potential for significant increases in the time required to both plan and deliver these more complex RT schemes.
In March 1999, we incorporated the use of 3D treatment planning and IMRT in our clinic in the management of early-stage breast cancer (24). Our goals were to improve the efficacy of whole breast RT delivery by optimizing dose homogeneity, avoiding unnecessary normal tissue irradiation and improving (standardizing) target volume coverage without significantly affecting the amount of time required to treat patients practically. In addition, this preliminary work with whole breast IMRT was conducted with the ultimate goal of applying this technology to more complex applications such as postmastectomy and comprehensive regional nodal irradiation. This report summarizes our overall experience using these technologies with standard whole breast RT and reviews the logistics of their use, as well as their clinical impact on dose delivery.
Section snippets
Methods and materials
Between March 1999 and March 2001, 281 women with Stage 0, I, and II breast cancer who were considered acceptable candidates for postlumpectomy RT were treated with a our new, in-house method of whole breast IMRT using static, multileaf collimator (sMLC) segments. Our IMRT technique has been previously reported (24). In brief, an immobilization device is constructed, and, after a CT scan is acquired of the patient in the treatment position (both arms extended above the head), the entrance and
3D beam alignment
As of April 1, 2001, 281 patients have been treated with the sMLC IMRT technique. The median time required for 3D alignment of the tangential fields on the CT breast images was approximately 40 min. In approximately 76% of patients (95 patients evaluated), changes were made from the clinical positioning of the tangential fields (based on the radiopaque markers placed clinically at initial CT scanning) to (1) better encompass breast tissue (e.g., lumpectomy cavity or chest wall) and/or (2) avoid
Discussion
The current study was conducted to evaluate the practical aspects of implementing a new whole breast IMRT technique in the clinic and to analyze the acute toxicities associated with this approach. By limiting the number of sMLC segments to a median of 6, it was possible to deliver a consistently uniform and standardized dose of RT to all patients in <10 min per case. Just as critical, the IMRT planning time was only 45 min per patient (on average). Although no direct comparison of acute
Conclusion
The use of 3D treatment planning and intensity modulation with an sMLC technique for tangential whole breast RT is an efficient and reliable method for achieving a uniform dose throughout the whole breast. Strict dose-volume constraints can be readily achieved in most patients, resulting in both improved coverage of breast tissue, as well as a potential reduction in acute and chronic toxicities. Because the median number of sMLC segments required per patient is only 6, the treatment time is not
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