Concepts and techniques of intraoperative radiotherapy (IORT) for breast cancer

Abstract

The standard treatment for early breast cancer comprises wide local excision, sentinel lymph node biopsy or axillary lymph node dissection, adjuvant medical treatment and radiotherapy to the whole breast. Many studies suggest that local control plays a crucial role in overall survival. The local recurrence rate is estimated to be 1% per year and varies between 4 and 7% after 5 years and up to 10 to 20% in the long-term follow up. On the basis of low local recurrence rates the concept of whole breast irradiation comes up for discussion, and partial breast irradiation (PBI) is increasingly under consideration. Intraoperative radiotherapy (IORT) is referred to as the delivery of a single high dose of irradiation directly to the tumor bed (confined target) during surgery. PBI (limited field radiation therapy, accelerated partial breast irradiation APBI) is the irradiation exclusively confined to a breast volume, the tumor surrounding tissue (tumor bed) either during surgery or after surgery without whole breast irradiation. Various methods and techniques for IORT or PBI are under investigation. The advantage of a very short radiation time or the integration of the complete radiation treatment into the surgical procedure convinces at a first glance. The promising short-term results of those studies must not fail to mention that local recurrence rates could probably increase and furthermore give rise to distant metastases and a reduction in overall survival. The combination of IORT in boost modality and whole breast irradiation has the ability to reduce local recurrence rates. The EBCTCG overview approves that differences in local treatment that substantially affect local recurrence rates would avoid about one breast cancer death over the next 15 years for every four local recurrences avoided, and should reduce 15-year overall mortality.

Mammographic Findings after Intraoperative Radiotherapy of the Breast

“…IORT is an alternative method of breast radiotherapy in which a complete course of breast radiotherapy is administered at the time of primary tumor resection or reexcision. IORT administered to the tumor bed may also substitute for an external beam boost when the patient is expected to receive WB-EBRT [13, 14]. As a form of accelerated partial breast radiotherapy (APBI), the purpose of IORT is to administer a complete course of radiotherapy to a predefined distance beyond the surgical margins in a single fraction of approximately 21 Gy [1].…”

Intraoperative Radiotherapy in Early-Stage Breast Cancer: Results of the Montpellier Phase II Trial

“…However, considering the low and focal local recurrence rates, the concept of accelerated partial breast irradiation (PBI) therapy has gained widespread interest employing various methods. Intraoperative RT (IORT) is one method that may offer the advantage of an excellent delineation of the tumor bed under visual control, very good dose homogeneity, and high sparing of normal tissue (6,7).…”

Using Histopathology Breast Cancer Data to Reduce Clinical Target Volume Margins at Radiotherapy

“…Although we use external-beam radiotherapy to boost the excision cavity in our institute, the given concept may be generalized to other radiation boost techniques such as intraoperative electron or photon irradiation and interstitial and balloon-based brachytherapy (12,13). In any of these techniques, knowledge of asymmetry of the macroscopic tumor excision combined with population-based knowledge of microscopic disease extension may help to improve the efficacy of the treatment.…”

“…Strategies to reduce the extent of the boost field while maintaining coverage of microscopic disease are expected to facilitate in achieving the optimal Reprint balance. Moreover, alternative methods to deliver the boost, such as intraoperative radiotherapy with photons or electrons or (balloon-based) brachytherapy have the potential to more closely conform to the postoperative target volume, thus further sparing normal tissue (12,13). Despite recent progress, uncertainties about the achieved margins of surgical excision and microscopic spread of disease are major factors that limit further reduction of the boost volume.…”