Intraoperative radiotherapy given as a boost after breast-conserving surgery in breast cancer patients

Intraoperative Radiotherapy as a Tumour-Bed Boost Combined with Whole Breast Irradiation Versus Conventional Radiotherapy in Patients with Early-Stage Breast Cancer: A Systematic Review and Meta-analysis

BACKGROUND

There is no definitive answer regarding the efficacy of intraoperative radiotherapy (IORT) as a tumour bed boost for patients with early-stage breast cancer. The purpose of this meta-analysis was to summarise the available evidence and explore the efficacy and safety of IORT combined with whole breast irradiation (WBI) versus conventional radiotherapy in women with early-stage breast cancer who underwent breast-conserving surgery.

METHODS

The PUBMED, MEDLINE, EMBASE, Web of Science, and Cochrane Library databases were searched from inception to December 31, 2022. We collected studies on the efficacy, cosmetic outcome, and safety of IORT boost combined with WBI compared with those of conventional radiotherapy in patients with early-stage breast cancer after breast-conserving surgery. Two authors independently performed the literature selection and data extraction. The quality of the randomised, controlled trials (RCTs) was assessed according to the PEDro scale. The quality of non-RCTs was assessed according to the Methodological Index for Non-Randomised Studies. Risk ratios (RRs) for the local recurrence rate (LRR), distant metastasis rate (DMR), disease-free survival (DFS), cosmetic outcome, and toxicity were pooled using fixed or random effects models. Meta-analysis of the included studies was performed by using RevMan 5.3 software.

RESULTS

Nine studies, including one RCT and eight non-RCTs, with a total of 3219 patients were included. In terms of LRR, there was no significant benefit of IORT boost+WBI over conventional radiotherapy (with or without the tumour bed boost) (RR = 0.77, 95% confidence interval (CI): 0.54-1.09, P = 0.14), but a trend towards benefit could be identified. There was a significant reduction in DMR in the IORT boost+WBI group (RR = 0.63, 95% CI: 0.46-0.85, P = 0.003) and a significant improvement in DFS (RR = 0.40, 95% CI: 0.25-0.65, P = 0.0002). Exploratory subgroup analysis showed that the DMR and DFS of the electron boost group were significantly better than those of conventional radiotherapy group, and there was a tendency for LRR to improve in the electron boost group. However, the LRR, DMR, and DFS did not effectively improve in the x-ray boost group. In terms of appearance and toxicity, there were no significant differences in cosmetic outcome, fibrosis, and hyperpigmentation between the two groups (RR = 0.99, 95% CI: 0.91-1.07, P = 0.78; RR = 1.02, 95% CI: 0.41-2.56, P = 0.96; RR = 0.42, 95% CI: 0.10-1.72, P = 0.23), but the incidence of oedema was significantly reduced in the IORT boost+WBI group (RR = 0.27, 95% CI: 0.13-0.59, P = 0.0009).

CONCLUSIONS

IORT boost+WBI is more effective than conventional radiotherapy after breast-conserving surgery in patients with early-stage breast cancer, and electron boost exhibits better efficacy than x-ray boost. In addition, the cosmetic and safety profiles of IORT boost+WBI are not inferior to those of conventional radiotherapy.

Comparison of mammography and ultrasound findings in the follow-up of patients with breast cancer treated with segmental mastectomy followed by intraoperative electron radiotherapy versus external whole breast radiotherapy

PURPOSE

This study aims to describe imaging findings in patients treated with intraoperative electron radiotherapy and compare them with those detected in patients treated with external whole breast radiotherapy (WBRT).

METHODS

The study population consisted of 25 patients who received intraoperative radiotherapy [IORT (21 Gy)] as single-dose radiotherapy and a control group of 25 patients who received WBRT at the same institution. Mammography and ultrasound (US) findings were divided into three groups: minor, intermediate, and advanced. On mammography, mass lesions were considered advanced, and asymmetries or architectural distortions were considered intermediate. Oil cysts, linear scars, and the increase in parenchymal density were considered minor findings. On US, irregular non-mass lesions were considered advanced, and circumscribed hypoechoic lesions or planar irregular scars with shadowing were considered intermediate. Oil cysts, fluid collections, or linear scars were considered minor findings.

RESULTS

On mammography, skin thickening (P = 0.001), edema (P < 0.001), increased parenchymal density (P < 0.001), dystrophic calcifications (P = 0.045), and scar/distortion (P = 0.005) were significantly more common in the WBRT group. On US, irregular non-mass lesions, which made interpretation considerably difficult, were significantly more common in the IORT group (P = 0.004). Dominant US findings were fluid collections and postoperative linear or planar scars in the WBRT group. Minor findings were more common in low-density breasts, and major findings (intermediate and advanced) were more common in high-density breasts on both mammographies (P = 0.011) and US (P = 0.027) in the IORT group.

CONCLUSION

Ill-defined non-mass lesions detected on US in the IORT group have not been defined previously. Radiologists should be aware of these lesions because they can be confusing, especially in early follow-up studies. This study has found that minor findings are seen more frequently in low-density breasts, while major findings are more common in high-density breasts in the IORT group. This has not been reported before, and further studies with more cases are needed to verify these results.

Early Outcome, Cosmetic Result and Tolerability of an IOERT-Boost Prior to Adjuvant Whole-Breast Irradiation

Background/Aims: Due to its favorable dose distribution and targeting of the region at highest risk of recurrence due to direct visualization of tumor bed, intraoperative electron radiation therapy (IOERT) is used as part of a breast-conserving treatment approach. The aim of this study was to analyze tumor control and survival, as well as the toxicity profile, and cosmetic outcomes in patients irradiated with an IOERT boost for breast cancer. Materials and Methods: 139 Patients treated at our institution between January 2010 and January 2015 with a single boost dose of 10 Gy to the tumor bed during breast-conserving surgery followed by whole-breast irradiation were retrospectively analyzed. Results: 139 patients were included in this analysis. The median age was 54 years (range 28−83 years). The preferred surgical strategy was segmental resection with sentinel lymphonodectomy (66.5%) or axillary dissection (23.1%). Regarding adjuvant radiotherapy, the vast majority received 5 × 1.8 Gy to 50.4 Gy. At a median follow-up of 33.6 months, recurrence-free and overall survival were 95.5% and 94.9%, respectively. No patient developed an in-field recurrence. Seven patients (5.0%) died during the follow-up period, including two patients due to disease recurrence (non-in-field). High-grade (CTCAE > 2) perioperative adverse events attributable to IOERT included wound healing disorder (N = 1) and hematoma (N = 1). High-grade late adverse events (LENT-SOMA grade III) were reported only in one patient with fat necrosis. Low-grade late adverse events (LENT-SOMA grade I-II) included pain (18.0%), edema (10.5%), fibrosis (21%), telangiectasia (4.5%) and pigmentation change (23.0%). The mean breast retraction assessment score was 1.66 (0−6). Both patients and specialists rated the cosmetic result “excellent/good” in 84.8% and 87.9%, respectively. Conclusion: Our study reports favorable data on the cosmetic outcome as well as the acute and early long-term tolerability for patients treated with an IOERT boost. Our oncologic control rates are comparable to the previous literature. However, prospective investigations on the role of IOERT in comparison to other boost procedures would be desirable.

The Role of Intraoperative Radiation in Early-stage Breast Cancer

Intraoperative radiation therapy (IORT) is a specialized form of accelerated partial breast irradiation in which a single dose of radiation is delivered to the tumor bed at the time of breast conserving surgery. With completion of radiation to the tumor bed at the time of surgery, IORT promises improved patient convenience, compliance, and quality of life. In addition, with its potentially skin-sparing properties and ability to deliver a high biologically effective dose to the tumor bed while reducing dose to nontarget tissues, IORT results in different but overall less toxicities compared with other modalities of radiation for breast cancer. However, skepticism over the role of IORT in breast cancer exists, and the 2 randomized trials that have analyzed IORT as the definitive radiation component of breast conservation therapy have shown an increase in local recurrence rates with IORT compared with whole breast irradiation, but similar rates of overall survival. In this review, we discuss the practicalities of IORT, the prospective data supporting and negating the role of IORT in lieu of whole breast irradiation, and the toxicity after IORT in early-stage breast cancer. We also review the role of IORT as a radiation boost and specific strategies for successful implementation of IORT in breast cancer.

Results of intraoperative radiotherapy given as a boost after breast conserving-surgery

Background

Whole breast irradiation after breast-conserving surgery (BCS) with an external beam boost of 10-16 Gy is currently the standard treatment in breast cancer. Various modalities have been used for tumor bed boost irradiation. This study aimed to evaluate the local recurrence rate, overall survival rate (OSR), toxicity and cosmetic outcome of intraoperative radiotherapy (IORT) as a boost followed by whole breast irradiation in patients who received BCS.

Methods

This is a retrospective study. Between December 2009 and March 2017, 81 patients who underwent BCS with IORT as a boost were enrolled in this study. For IORT, a single dose of 20 Gy was delivered using a 30-50 kV photon beam, intraoperatively. All patients received whole breast radiation therapy (WBRT) of 42.5-50 Gy over 4-5 weeks. The primary endpoint was a 3-year local recurrence rate. Secondary endpoints included the OSR, toxicity and cosmetic outcome at 6 months after radiation treatment.

Results

At a median follow-up of 43 months, ipsilateral local recurrence was observed in one of the 81 patients (1.2%) which occurred in the same quadrant of the breast index. The 3-year OSR was 89.8%. Treatment was well-tolerated with no grade 3-4 acute and late toxicity, and 87% of patients were recorded as excellent-good cosmesis.

Conclusions

The use of BCS with IORT as a boost resulted in a low local recurrence rate and excellent cosmetic outcome in early breast cancer. Thus, IORT as a boost could be considered as an alternative to an external beam boost. Prospective studies are needed to confirm this data.

Intraoperative Electron Radiotherapy (IOERT) in the Treatment of Primary Breast Cancer

IOERT (intraoperative electron radiotherapy) in breast cancer is used either as a boost (10-12 Gy) followed by whole breast irradiation (WBI) or as full-dose partial breast irradiation (PBI, 20-24 Gy) during breast-conserving surgery. IOERT has the longest evidence of all IORT techniques. When administered as a boost, excellent low local recurrence rates were observed in long-term follow-up >5 years. Even in high-risk groups like triple-negative or locally advanced breast cancers, IOERT contributes to long-term local control rates of more than 90%. For selected low-risk groups, IOERT as PBI with 21 Gy seems to be a viable treatment alternative to standard WBI. IOERT has been shown to be advantageous for several reasons: Geographic misses are avoided due to direct visualization of the tumor bed; thus, a high single dose is delivered with utmost precision to small volumes, completely sparing the skin and ensuring good long-term cosmetic outcome. Furthermore, high single doses seem to induce biological mechanisms with verifiable antitumor capability in in-vitro cell-line studies. In addition, IOERT markedly shortens the overall treatment time both in combination with (now mostly hypofractionated) WBI or as a PBI in selected low-risk constellations.

Accelerated Intensity-Modulated External Radiotherapy as a New Technical Approach to Treat the Index Quadrant after Conserving Surgery in Early Breast Cancer: A Preliminary Study

Purpose

We present a novel technical approach to treat the index quadrant after conserving surgery in patients with early breast cancer and study its clinical feasibility.

Methods and material

Patients selected for the study, after breast conserving surgery with histologically verified breast carcinoma, signed a full informed consent to intensity-modulated external radiotherapy of the partial breast. Treatment was performed with the 6 MV beam from one of the Elekta Precise LINAC units installed in our Department. The prescribed dose was 30 Gy in 5 fractions in 10 days.

Results

Acute toxicity was minimal. No skin changes were noted during treatment or during the first 6 months after radiotherapy treatment.

Conclusions

Accelerated partial breast irradiation using intensity-modulated external radiotherapy is technically feasible. We think the approach will give good results in terms of local control, toxicity and quality of life, at the same time sparing resources for the patient and health care system.

Pulsed-dose-rate peri-operative brachytherapy as an interstitial boost in organ-sparing treatment of breast cancer

Purpose

To evaluate peri-operative multicatheter interstitial pulsed-dose-rate brachytherapy (PDR-BT) with an intra-operative catheter placement to boost the tumor excision site in breast cancer patients treated conservatively.

Material and methods

Between May 2002 and October 2008, 96 consecutive T1-3N0-2M0 breast cancer patients underwent breast-conserving therapy (BCT) including peri-operative PDR-BT boost, followed by whole breast external beam radiotherapy (WBRT). The BT dose of 15 Gy (1 Gy/pulse/h) was given on the following day after surgery.

Results

No increased bleeding or delayed wound healing related to the implants were observed. The only side effects included one case of temporary peri-operative breast infection and 3 cases of fat necrosis, both early and late. In 11 patients (11.4%), subsequent WBRT was omitted owing to the final pathology findings. These included eight patients who underwent mastectomy due to multiple adverse prognostic pathological features, one case of lobular carcinoma in situ, and two cases with no malignant tumor. With a median follow-up of 12 years (range: 7-14 years), among 85 patients who completed BCT, there was one ipsilateral breast tumor and one locoregional nodal recurrence. Six patients developed distant metastases and one was diagnosed with angiosarcoma within irradiated breast. The actuarial 5- and 10-year disease free survival was 90% (95% CI: 84-96%) and 87% (95% CI: 80-94%), respectively, for the patients with invasive breast cancer, and 91% (95% CI: 84-97%) and 89% (95% CI: 82-96%), respectively, for patients who completed BCT. Good cosmetic outcome by self-assessment was achieved in 58 out of 64 (91%) evaluable patients.

Conclusions

Peri-operative PDR-BT boost with intra-operative tube placement followed by EBRT is feasible and devoid of considerable toxicity, and provides excellent long-term local control. However, this strategy necessitates careful patient selection and histological confirmation of primary diagnosis.

Intraoperative radiotherapy (IORT) as boost in breast cancer

The term IORT (intraoperative radiotherapy) is currently used for various techniques that show huge differences in dose delivery and coverage of the tissue at risk. The largest evidence for boost IORT preceding whole breast irradiation (WBI) originates from intraoperative electron treatments (IOERT) with single doses around 10 Gy. At median follow-up periods at 6 years, outstandingly low local recurrence rates of less than 1% are observed. Higher local relapse rates were described for G3 tumors and triple negative breast cancers as well as for IORT following primary systemic treatment for locally advanced tumors. Even there, long term (>5y) local tumor control rates mostly beyond 95% were maintained. Compared to other boost methods, an intraoperative treatment has evident advantages in terms of precision (by avoiding a “spatial and/or temporal miss”), cosmetic outcome and patient comfort. Direct visualisation of a tumor bed during surgery guarantees for an accurate dose delivery, which has additionally gained importance in times of primary reconstruction techniques after lumpectomy, since IORT is performed before breast tissue including parts of the tumor bed is mobilized for plastic purposes. As a consequence of direct tissue exposure without distension by hematoma/seroma, IORT allows for small treatment volumes and complete skin sparing, both having a positive effect on late tissue tolerance and, hence, cosmetic appearance. Boost IORT marginally prolongs the surgical procedure, while significantly shortening postoperative radiotherapy. Its combination with external beam radiotherapy to the whole breast (WBI) is currently tested in two multicentric prospective trials: as kV-IORT in the multicentric TARGIT-B (oost) study, and as IOERT in the HIOB trial (3 weeks hypofractionated WBI preceded by IORT electron boost).

Impact of intraoperative radiotherapy on cosmetic outcome and complications after oncoplastic breast surgery

Breast cancer is one of the most common tumors in the population worldwide. Conservative breast surgery (CBS) is one of the preferred surgical options, because both the oncologic and esthetic needs of the patient can be addressed. CBS surgical outcomes tend to be more effective with reduced chances of disease recurrence when radiotherapy (RT) treatment is considered as an adjunct treatment, either applied during surgery (IORT) and/or after (EBRT). The purpose of our study was to compare surgical outcomes between IORT and EBRT after CBS. In the past 5 years, we performed CBS in 489 patients in our clinic. Of these patients, 83 underwent adjunct treatment with IORT and 109 were treated with EBRT in accordance with our university approved clinical protocol. Surgical outcomes, early complication rates, and esthetic results were compared between these two groups of CBS patients, with a mean follow-up time of 17 months. IORT allowed breast irradiation treatment to be performed without effecting overlying skin, thus cosmetic outcomes tended to be favorable. Esthetic postoperative results assessed with the Breast Cancer Conservation Treatment (BCCTcore) software showed that the differences between IORT and EBRT were not statistically significant (including those patients that underwent further oncoplastic techniques after EBRT). The disease recurrence rates between the two groups were not significantly different. IORT is a safe, fast, and feasible technique that provides effective and comparable CBS outcomes for patients with breast cancer.

Our intraoperative boost radiotherapy experience and applications

OBJECTIVE

To present our experience since November 2013, and case selection criteria for intraoperative boost radiotherapy (IObRT) that significantly reduces the local recurrence rate after breast conserving surgery in patients with breast cancer.

MATERIAL AND METHODS

Patients who were suitable for IObRT were identified within the group of patients who were selected for breast conserving surgery at our breast council. A MOBETRON (mobile linear accelerator for IObRT) was used for IObRt during surgery.

RESULTS

Patients younger than 60 years old with <3 cm invasive ductal cancer in one focus (or two foci within 2 cm), with a histologic grade of 2-3, and a high possibility of local recurrence were admitted for IObRT application. Informed consent was obtained from all participants. Lumpectomy and sentinel lymph node biopsy was performed and advancement flaps were prepared according to the size and inclination of the conus following evaluation of tumor size and surgical margins by pathology. Distance to the thoracic wall was measured, and a radiation oncologist and radiation physicist calculated the required dose. Anesthesia was regulated with slower ventilation frequency, without causing hypoxia. The skin and incision edges were protected, the field was radiated (with 6 MeV electron beam of 10 Gy) and the incision was closed. In our cases, there were no major postoperative surgical or early radiotherapy related complications.

CONCLUSION

The completion of another stage of local therapy with IObRT during surgery positively effects sequencing of other treatments like chemotherapy, hormonotherapy and radiotherapy, if required. IObRT increases disease free and overall survival, as well as quality of life in breast cancer patients.

Intraoperative radiotherapy in early stage breast cancer: potential indications and evidence to date

Following early results of recent studies of intraoperative radiotherapy (IORT) in the adjuvant treatment of patients with early breast cancer, the clinical utility of IORT is a subject of much recent debate within the breast oncology community. This review describes the intraoperative techniques available, the potential indications and the evidence to date pertaining to local control and toxicity. We also discuss any implications for current practice and future research.

Boost IORT in Breast Cancer: Body of Evidence

The term IORT (intraoperative radiotherapy) is currently used for various techniques that show decisive differences in dose delivery. The largest evidence for boost IORT preceding whole breast irradiation (WBI) originates from intraoperative electron treatments with single doses around 10 Gy, providing outstandingly low local recurrence rates in any risk constellation also at long term analyses. Compared to other boost methods, an intraoperative treatment has evident advantages as follows. Precision. Direct visualisation of the tumour bed during surgery guarantees an accurate dose delivery. This fact has additionally gained importance in times of primary reconstruction techniques after lumpectomy to optimise cosmetic outcome. IORT is performed before breast tissue is mobilised for plastic purposes. Cosmesis. As a consequence of direct tissue exposure without distension by hematoma/seroma, IORT allows for small treatment volumes and complete skin sparing, both having a positive effect on late tissue tolerance and, hence, cosmetic appearance. Patient Comfort. Boost IORT marginally prolongs the surgical procedure, while significantly shortening postoperative radiotherapy. Its combination with a 3-week hypofractionated external beam radiotherapy to the whole breast (WBI) is presently tested in the HIOB trial (hypofractionated WBI preceded by IORT electron boost), a prospective multicenter trial of the International Society of Intraoperative Radiotherapy (ISIORT).

Intraoperative radiation therapy techniques and options for breast cancer

Intraoperative radiation therapy (IORT) applied to peri-tumoral tissue can play a significant role in preventing breast cancer recurrence. Approximately 80-100% of breast cancer recurrences occur at the tumor bed, thus restricting radiation to the postoperative bed may be reasonable in a select group of patients. IORT can be delivered as a boost in addition to standard external beam radiotherapy, or as a primary form of treatment. IORT can be administered via electrons generated by a linear accelerator or by a system using low-energy x-rays. Potential advantages of IORT include improved cosmesis, shorter overall treatment time, radiobiological advantages, and ability to define the tumor bed by direct visualization during surgery assuring accurate delivery of radiotherapy. IORT alone can be considered for appropriate patients with early breast cancer who may not require whole-breast radiation therapy. This review discusses patient criteria and benefits, IORT's roots, radiobiological considerations, treatment options, and device categories.

Feasibility of concervative breast surgery and intraoperative radiation therapy for early breast cancer: a single-center, open, non-randomized, prospective pilot study

Intraoperative radiotherapy (IORT) consists of an accelerated, single-dose, partial breast irradiation, performed immediately after breast conservative surgery. In the present study, we report the results of our feasibility protocol study using IORT between 2005 and 2009. We analyzed the data from a single-center, open, non-randomized, prospective pilot study including patients who underwent breast conservative surgery for invasive breast cancer between January 2005 and December 2009 at our Clinic of Surgery. Patients were divided based on IORT performance and stratified by age (≥48 or <48 years). Data were analyzed using R (version 2.15.2), considering a level of significance at P<0.05. Among the 247 eligible patients, 81 accepted the IORT protocol. Intraoperative IORT feasibility was 95.1% (77/81). In 71.4% (55/77) of the cases no postoperative complication was registered. Concerning local recurrence and overall survival, no significant difference was observed between women who underwent the IORT protocol or standard treatment. Among the patients aged <48 years, no local recurrence was noted after IORT protocol, and among women aged ≥48, local recurrences developed later in patients treated with IORT than with standard treatment. IORT represents a feasible and promising technique for the treatment of early breast cancer, with low morbidity, and beneficial aesthetic and oncologic results. Further studies are required in order to extend the inclusion criteria and offer IORT to a larger number of breast cancer patients.

Breast cancer: Actual methods of treatment and future trends

The recent ten to twenty years have seen a substantial progress in the diagnosis and treatment of breast cancer. A rapid development of various curative options has led to the improvement of treatment outcomes, while paying more and more attention to the aspects of quality of life and cosmetic effect. In our publication, we wish to outline certain trends in the development of modern treatment of breast cancer. Among topics discussed are new forms of molecular diagnostics, new approach to the idea of sentinel node biopsy, as well as new techniques for delivery of medical procedures, the increasing use of nomograms, progress in the techniques of breast conservative treatment, modern approach to occult breast lesions, the increasing use of neoadjuvant treatment and intraoperative radiotherapy.

Six-year outcome of a prospective study evaluating tumor bed boost with intra-operative electron irradiation followed by whole-breast irradiation for early-stage breast cancer

A prospective study was performed for patients with early-stage breast cancer in which a single fraction of intraoperative electron irradiation (IOERT) was given to the tumor bed, followed by conventional fractionated whole-breast irradiation (WBRT). Patients with T1/T2N0 breast cancer underwent lumpectomy and sentinel lymph node biopsy. A tumor bed boost of 10 Gy of IOERT using 6-12 MeV electrons was administered by a dedicated mobile linear accelerator in the operating room. After adequate wound healing, 48 Gy WBRT was given to the whole breast in 24 fractions. Fifty-two patients were enrolled between February 2003 and January 2005. At a median follow-up of 79 months, there were two local relapses. The 6-year actuarial overall survival and distant control rates were 89% and 96%, respectively. At last follow-up, cosmesis was graded as excellent or good in 45 (87%), fair in five (10%), and poor in two patients (4%), respectively. Difficulty in wound healing occurred in two patients who had additional surgery later. One patient developed significant fibrosis after aspiration of a symptomatic seroma. The result of this pilot study shows the feasibility of using IOERT as the tumor bed boost in lieu of 6-8 days of standard electron beam treatment with good local control and cosmetic results. However, late surgical intervention of the lumpectomy bed may result in more pronounced tissue fibrosis and wound healing difficulty.

First description of MR mammographic findings in the tumor bed after intraoperative radiotherapy (IORT) of breast cancer

The aim was to investigate changes in the tumor bed on magnetic resonance mammography (MRM) after intraoperative radiotherapy (IORT) and whether they would limit the diagnostic value of posttherapeutic MRM. We retrospectively investigated 36 patients undergoing MRM after IORT (median interval 2.8 years, range 0.4-7.1). Wound cavities with fat necrosis were common after IORT (81%). They were associated with persisting contrast enhancement, i.e., enhancement was mostly seen irrespective of the posttherapeutic interval. It normally presented as rim enhancement and did not cause any diagnostic uncertainty if viewed together with other tissue characteristics. We do not expect a limited diagnostic value of MRM after IORT.

Relative biological effectiveness of photon energies used in brachytherapy and intraoperative radiotherapy techniques for two breast cancer cell lines

BACKGROUND

Partial breast irradiation (IORT or brachytherapy) differ from external radiation of whole breast in terms of irradiated volumes, fractionation, radiation energy and dose rate; all factors influencing the treatment outcome in a complex manner. Theoretically obtained RBE values comparing effects of radiation used in IORT and external therapy are published, but experimental studies are required to confirm these data. The aim of this study is to establish such RBE values for two breast cancer cell lines.

MATERIALS AND METHODS

Colony formation of breast cancer cell lines (MCF-7 and T-47D) were studied after photon irradiation with qualities and dose rates used in IORT, brachytherapy and external radiation. RBE values from survival data were used to compare effects.

RESULTS

Increasing the photon energy (dose rate 0.2 Gy/min) from 50 kV (Intrabeam) to 380 keV (¹⁹²Ir source) and 6 MV (linear accelerator) yielded an increase in the cell survival, whereas increasing the dose rate to 6 Gy/min had minor effect. Average RBE values for 50 kV with 6 MV as reference radiation varied from about 1.4 (for doses < 5 Gy) to > 1.9 (for doses < 0.02 Gy) for MCF-7 cells and from about 1.4 to > 3.1 for T-47D cells for the same dose levels. Corresponding RBE values for 380 keV radiation were about 1.4 for MCF-7 cells and 1.3-2.3 for T-47D cells.

CONCLUSION

RBE data for breast cancer cells exposed to radiation used in IORT, brachytherapy or external radiation differ among the cell lines tested. The values are in agreement with published theoretical and experimental work.

The role of intraoperative radiotherapy in solid tumors

BACKGROUND

Combined multimodality therapy is becoming standard treatment for many solid tumors, but the role of intraoperative radiotherapy in the management of solid tumors remains uncertain. The aim is to review the indication, application, and outcomes of intraoperative radiotherapy in the management of nongynecological solid tumors.

METHODS

A literature search was performed using Medline, Embase, Ovid, and Cochrane database for studies between 1965 and 2008 assessing intraoperative radiotherapy, using the keywords "intraoperative radiotherapy," "colorectal cancer," "breast cancer," "gastric cancer," "pancreatic cancer," "soft tissue tumor," and "surgery." Only publications in English with available abstracts and regarding adult humans were included, and the evidence was critically evaluated.

RESULTS

Our search retrieved 864 publications. After exclusion of nonclinical papers, duplicated papers and exclusion of brachytherapy papers, 77 papers were suitable to assess the current role of intraoperative radiotherapy. The clinical application and evidence base of intraoperative radiotherapy for each cancer is presented.

CONCLUSIONS

Current studies in all common cancers show an additional benefit in local recurrence rates when intraoperative radiotherapy is included in the multimodal treatment. However, intraoperative radiotherapy may not improve overall survival and has significant morbidity depending on the site of the tumor. Intraoperative radiotherapy does have a role in the multidisciplinary management of solid tumors, but further studies are required to more precisely determine the extent of benefit.

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

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.

Prototyping a large field size IORT applicator for a mobile linear accelerator

The treatment of large tumors such as sarcomas with intra-operative radiotherapy using a Mobetron is often complicated because of the limited field size of the primary collimator and the available applicators (max Ø100 mm). To circumvent this limitation a prototype rectangular applicator of 80 x 150 mm(2) was designed and built featuring an additional scattering foil located at the top of the applicator. Because of its proven accuracy in modeling linear accelerator components the design was based on the EGSnrc Monte Carlo simulation code BEAMnrc. First, the Mobetron treatment head was simulated both without an applicator and with a standard 100 mm applicator. Next, this model was used to design an applicator foil consisting of a rectangular Al base plate covering the whole beam and a pyramid of four stacked cylindrical slabs of different diameters centered on top of it. This foil was mounted on top of a plain rectangular Al tube. A prototype was built and tested with diode dosimetry in a water tank. Here, the prototype showed clinically acceptable 80 x 150 mm(2) dose distributions for 4 MeV, 6 MeV and 9 MeV, obviating the use of complicated multiple irradiations with abutting field techniques. In addition, the measurements agreed well with the MC simulations, typically within 2%/1 mm.

Accelerated partial breast irradiation in early-stage breast cancer

Whole-breast irradiation, as part of breast-conservation therapy (BCT), has well-established results, good cosmesis, and low toxicity. Results from the BCT trials suggest that the risk for ipsilateral breast cancer recurrence resides within close proximity to the original tumor site. This leads investigators to consider the role of an accelerated and more tumor bed-focused course of radiotherapy. Accelerated partial-breast irradiation (APBI) involves treating a limited volume of breast tissue, with dose of irradiation per fraction increased and the treatment time course decreased. Four currently available methods of APBI are interstitial brachytherapy, intracavitary brachytherapy, intraoperative radiotherapy, and three-dimensional conformal external-beam radiotherapy. Patient selection is critical. This review article presents some preliminary clinical observations and limitations that suggest a potential role for APBI as a more user-friendly mode for delivering radiotherapy after lumpectomy for early breast cancer.

Early mammographic and sonographic findings after intraoperative radiotherapy (IORT) as a boost in patients with breast cancer

The aim of this study was to evaluate mammographic and sonographic changes at the surgical site within the first 2 years after IORT as a boost followed by whole-breast radiotherapy (WBRT), compared with a control group treated with WBRT alone. All patients had breast-conserving surgery for early-stage breast cancer. Group A: n = 27, IORT (20 Gy) followed by WBRT (46 Gy). Group B (control group): n = 27, WBRT alone (56-66 Gy). Mammography: fat necrosis in 14 group A versus four group B patients (P < 0.001); parenchymal scarring classified as unorganized at the last follow-up in 16 vs seven cases, respectively (P = 0.03). Ultrasound: overall number of patients with circumscribed findings 27 vs 18 (P < 0.001); particular hematomas/seromas in 26 vs 13 patients (P < 0.001). Synopsis of mammography and ultrasound: overall postoperative changes were significantly higher classified in group A (P = 0.01), but not judged to have a significantly higher impact on interpretation. Additional diagnostic procedures, due to unclear findings at the surgical site, were performed on four patients of both groups. Within the first 2 years after IORT as a boost, therapy-induced changes at the original tumor site are significantly more pronounced compared with a control group. There is no evidence that the interpretation of findings is complicated after IORT.

Long-term toxicity of an intraoperative radiotherapy boost using low energy X-rays during breast-conserving surgery

PURPOSE

Intraoperative radiotherapy (IORT) as a boost for breast cancer delivers a high single dose of radiation to a late-reacting tissue; therefore late toxicity is of particular interest, and long-term follow-up is warranted. To date there are only limited data available on breast cancer patients treated with IORT using low energy X-rays. We analyzed toxicity and cosmesis after IORT as a boost with a minimum follow-up of 18 months.

METHODS AND MATERIALS

A total of 73 patients treated with IORT (20 Gy/50 kV X-rays; INTRABEAM [Carl Zeiss Surgical, Oberkochen, Germany]) to the tumor bed during breast-conserving surgery as a boost followed by whole-breast radiotherapy (WBRT, 46 Gy) underwent a prospective, predefined follow-up (median, 25 months; range 18-44 months), including clinical examination and breast ultrasound at 6-months and mammographies at 1-year intervals. Toxicities were documented using the common toxicity criteria (CTC)/European Organization for Research and Treatment of Cancer and the LENT-SOMA score. Cosmesis was evaluated with a score from 1 to 4.

RESULTS

The IORT in combination with WBRT was well tolerated, with no Grade 3 or 4 skin toxicities and no telangiectasias. Fibrosis of the entire breast was observed in 5% of the patients. A circumscribed fibrosis around the tumor bed was palpable in up to 27% with a peak around 18 months after therapy and a decline thereafter. The observed toxicitiy rates were not influenced by age, tumor stage, or systemic therapy. The cosmetic outcome was good to excellent in>or=90% of cases.

CONCLUSIONS

After IORT of the breast using low-energy X-rays, no unexpected toxicity rates were observed during long-term-follow-up.

Mammographic and ultrasonographic comparison between intraoperative radiotherapy (IORT) and conventional external radiotherapy (RT) in limited-stage breast cancer, conservatively treated

OBJECTIVE

Assess mammographic and echographic modifications in mild cases of breast cancer (suitable for conservative surgery) after intraoperatory radio treatment (IORT) as opposed to conventional post-operative radiotherapy (RT).

MATERIALS AND METHODS

We report data from 45 patients in each group (IORT and RT). All patients were examined using the same mammographic and ecographic equipment at 6, 12 and 24 months after treatment. We focused on structural alterations, edema and others, and quantified them using pre-established (unbiased) protocols. Both patient examination and subsequent assessment of the results were performed by radiologists with exepertise in breast cancer evaluation.

RESULTS

At 6 months, IORT patients showed slightly more pronounced structural distortions and oedema than RT patients; these differences became more apparent at 12 months, with the addition of fat necrosis and/or calcifications. These alterations were evident and consistent under both mammographic and ecographic examination, and became even more pronounced at 24 months. At this stage, RT patients showed minimal alterations of the tissue (apart from normal post-surgical scarring), whereas IORT patients showed virtually no improvement over the preceding 12-month period.

CONCLUSION

We show radiological alterations in post-operative breast cancer are significantly more pronounced in patients treated with IORT as opposed to RT.

Intraoperative radiotherapy (IORT) as a boost in patients with early-stage breast cancer -- acute toxicity

BACKGROUND

We report on acute toxicities as well as the early cosmetic outcome of patients receiving intraoperative radiotherapy (IORT) followed by whole-breast radiotherapy (WBRT) compared to patients treated with standard WBRT alone.

PATIENTS AND METHODS

From 2/2002 until 2/2005, 84 breast cancer patients were treated with IORT during breast-conserving surgery (BCS) as a boost (20 Gy/50 kV X-rays) followed by WBRT. After wound healing, all IORT patients were treated with WBRT at a total dose of 46 Gy. For the purpose of comparison, 53 patients treated consecutively between 1/2003 and 12/2004 in our institution with BCS followed by WBRT at a total dose of 50-66 Gy, were analyzed. All patients had a defined followup schedule. Toxicities were prospectively documented using the CTC/EORTC Score. Cosmesis was evaluated after 6 months using a 1-4 score.

RESULTS

Treatment was well tolerated with no grade 3/4 acute toxicity. Rare adverse effects following IORT included wound healing problems (2%), erythema grade I-II (3%), palpable seroma (6%) and mastitis (2-4%). The number of patients with induration of the tumor bed was comparably low.

CONCLUSION

IORT with the IntrabeamTM system applied as a boost during BCS, followed by 46 Gy WBRT, exerts similar acute toxicity as standard WBRT. Further follow-up is needed to assess long-term toxicity and efficacy.

Intraoperative radiotherapy given as a boost for early breast cancer: long-term clinical and cosmetic results

PURPOSE

The standard radiotherapy (RT) of breast cancer consists of 50 Gy external beam RT (EBRT) to the whole breast followed by an electron boost of 10-16 Gy to the tumor bed, but this has several cosmetic disadvantages. Intraoperative radiotherapy (IORT) could be an alternative to overcome these.

METHODS AND MATERIALS

We evaluated 50 women with early breast cancer operated on in a dedicated IORT facility. Median dose of 10 Gy was delivered using 9-MeV electron beams. All patients received postoperative EBRT (50 Gy in 2 Gy fractions). Late toxicity and cosmetic results were assessed independently by two physicians according to the Common Terminology Criteria for Adverse Event v3.0 grading system and the European Organization for Research and Treatment of Cancer questionnaires.

RESULTS

After a median follow-up of 9.1 years (range, 5-15 years), two local recurrences were observed within the primary tumor bed. At the time of analysis, 45 patients are alive with (n = 1) or without disease. Among the 42 disease-free remaining patients, 6 experienced Grade 2 late subcutaneous fibrosis within the boost area. Overall, the scores indicated a very good quality of life and cosmesis was good to excellent in the evaluated patients.

CONCLUSION

Our results confirm that IORT given as a boost after breast-conserving surgery is a reliable alternative to conventional postoperative fractionated boost radiation.

The Salzburg concept of intraoperative radiotherapy for breast cancer: Results and considerations

Aim of this study is to show that ipsilateral breast tumor recurrence (IBTR) after breast conserving surgery can be reduced by proper surgery and modern radiotherapy techniques. Three hundred and seventy eight women with stage I or II breast cancer had breast conserving surgery and received 51-56.1 Gy of postoperative radiation to the whole breast in 1.7 Gy fractions, but patients received different boost strategies. Group 1 (n = 188) received electron boost radiation of 12 Gy subsequent to the irradiation to the whole breast, group 2 (n = 190) received intraoperative electron boost radiation of 9 Gy directly to the tumor bed, followed by whole breast irradiation. After a median follow up period of 81.0 months in group 1 and a median follow up period of 51.1 months in group 2, 12 IBTRs (6.4%) could be observed in group 1 and no IBTR could be observed in group 2 (0.0%). The 5-year actuarial rates of IBTR were 4.3% (95% CI, 1.9-8.3%) and 0.0% (95% CI, 0.0-1.9%), respectively (p = 0.0018). The 5-year actuarial rates of distant recurrence were 8.6% (95% CI, 4.9-13.5%) and 4.2% (95% CI, 1.8-8.2%), respectively (p = 0.08). The 5 year disease-free survival rates were 90.9% (95% CI, 85.8-94.7%) in group 1 and 95.8% (95% CI, 91.8-98.2%) in group 2 (p = 0.064). Immediate IORT-boost and whole breast irradiation yields excellent local control at 5 years, and was associated with a statistically significant decreased rate of IBTR compared with a similar cohort of patients treated with whole breast irradiation and conventional electron boost.

Mathematical modelling of radiotherapy strategies for early breast cancer

Targeted intraoperative radiotherapy (Targit) is a new concept of partial breast irradiation where single fraction radiotherapy is delivered directly to the tumour bed. Apart from logistic advantages, this strategy minimizes the risk of missing the tumour bed and avoids delay between surgery and radiotherapy. It is presently being compared with the standard fractionated external beam radiotherapy (EBRT) in randomized trials. In this paper we present a mathematical model for the growth and invasion of a solid tumour into a domain of tissue (in this case breast tissue), and then a model for surgery and radiation treatment of this tumour. We use the established linear-quadratic (LQ) model to compute the survival probabilities for both tumour cells and irradiated breast tissue and then simulate the effects of conventional EBRT and Targit. True local recurrence of the tumour could arise either from stray tumour cells, or the tumour bed that harbours morphologically normal cells having a predisposition to genetic changes, such as a loss of heterozygosity (LOH) in genes that are crucial for tumourigenesis, e.g. tumour suppressor genes (TSGs). Our mathematical model predicts that the single high dose of radiotherapy delivered by Targit would result in eliminating all these sources of recurrence, whereas the fractionated EBRT would eliminate stray tumour cells, but allow (by virtue of its very schedule) the cells with LOH in TSGs or cell-cycle checkpoint genes to pass on low-dose radiation-induced DNA damage and consequently mutations that may favour the development of a new tumour. The mathematical model presented here is an initial attempt to model a biologically complex phenomenon that has until now received little attention in the literature and provides a 'proof of principle' that it is possible to produce clinically testable hypotheses on the effects of different approaches of radiotherapy for breast cancer.

Accelerated Partial Breast Irradiation as an Alternative to Whole-Breast Irradiation in Breast-Conserving Therapy for Early-Stage Breast Cancer

Breast-conserving therapy has been established as a standard treatment for women with early-stage breast cancer. Whole-breast irradiation has traditionally been utilized to consolidate local therapy following conservative surgery. Recently, the need for whole-breast irradiation after breast-conserving surgery has become controversial, with some investigators advocating accelerated partial breast irradiation as an alternative. Accelerated partial breast irradiation is delivered over a shorter period and only to a portion of the breast. This review will examine the emerging role of accelerated partial breast irradiation in the treatment of early-stage breast cancer and review the biologic rationale for, techniques of, and limitations of partial breast irradiation following breast-conserving surgery.

Accelerated partial breast irradiation as an alternative to whole breast irradiation in breast-conserving therapy for early-stage breast cancer

Breast-conserving therapy has been established as a standard treatment for women with early-stage breast cancer. Whole breast irradiation has traditionally been utilized to consolidate local therapy following conservative surgery. Recently, the need for whole breastwhole breast irradiation after breast-conserving surgery has become controversial, with some investigators advocating accelerated partial breast irradiation as an alternative. Accelerated partial breast irradiation is delivered over a shorter period and only to a portion of the breast. This review will examine the emerging role of accelerated partial breast irradiation in the treatment of early-stage breast cancer and review the biologic rationale for, techniques of, and limitations of partial breast irradiation following breast-conserving surgery.

The evolution of accelerated, partial breast irradiation as a potential treatment option for women with newly diagnosed breast cancer considering breast conservation

Breast conservation therapy (BCT) is a safe, effective alternative to mastectomy for many women with newly diagnosed breast cancer. This approach involves local excision of the malignancy with tumor-free margins, followed by 5-7 weeks of external beam whole breast (WB) radiotherapy (XRT) to minimize the risk of an in-breast tumor recurrence (IBTR). Though clearly beneficial, the extended course of almost daily postoperative radiotherapy interrupts normal activities and lengthens care. Additional options are now available that shorten the radiotherapy treatment time to 1-5 days (accelerated) and focus an increased dose of radiation on just the breast tissue around the excision cavity (partial breast). Recent trials with accelerated, partial breast irradiation (APBI) have shown promise as a potential replacement to the longer, whole breast treatments for select women with early-stage breast cancer. Current APBI approaches include interstitial brachytherapy, intracavitary (balloon) brachytherapy, and accelerated external beam (3-D conformal) radiotherapy, all of which normally complete treatment over 5 days, while intraoperative radiotherapy (IORT) condenses the entire treatment into a single dose delivered immediately after tumor excision. Each approach has benefits and limitations. This study covers over 2 decades of clinical trials exploring APBI, discusses treatment variables that appear necessary for successful implementation of this new form of radiotherapy, compares and contrasts the various APBI approaches, and summarizes current and planned randomized trials that will shape if and how APBI is introduced into routine clinical care. Some of the more important outcome variables from these trials will be local toxicity, local and regional recurrence, and overall survival. If APBI options are ultimately demonstrated to be as safe and effective as current whole breast radiotherapy approaches, breast conservation may become an even more appealing choice, and the overall impact of treatment may be further reduced for certain women with newly diagnosed breast cancer.

Radiobiological aspects of intraoperative radiotherapy (IORT) with isotropic low-energy X rays for early-stage breast cancer

The purpose of this study was to model the distribution of biological effect around a miniature isotropic X-ray source incorporating spherical applicators for single-dose or hypo-fractionated partial-breast intraoperative radiotherapy. A modification of the linear-quadratic formalism was used to calculate the relative biological effectiveness (RBE) of 50 kV X rays as a function of dose and irradiation time for late-reacting normal tissue and tumor cells. The response was modeled as a function of distance in the tissue based on the distribution of equivalent dose and published dose-response data for pneumonitis and subcutaneous fibrosis after single-dose conventional irradiation. Furthermore, the spatial distribution of tumor cell inactivation was assessed. The RBE for late reactions approached unity at the applicator surface but increased as the absorbed dose decreased with increasing distance from the applicator surface. The ED50 for pneumonitis was estimated to be reached at a depth of 6-11 mm in the tissue and that for subcutaneous fibrosis at 3-6 mm, depending on the applicator diameter and whether the effect of recovery was included. Thus lung tissue would be spared because of the thickness of the thorax wall. The RBE for tumor cells was higher than for late-reacting tissue. The applicator diameter is an important parameter in determining the range of tumor cell control in the irradiated tumor bed.

Forward-planned, multiple-segment, tangential fields with concomitant boost in the treatment of breast cancer

We report on the utility of forward-planned, 3-dimensional (3D), multiple-segment tangential fields for radiation treatment of patients with breast cancer. The technique accurately targets breast tissue and the tumor bed and reduces dose inhomogeneity in the target. By decreasing excess dose to the skin and lung, a concomitant boost to the tumor bed can be delivered during the initial treatment, thereby decreasing the overall treatment time by one week. More than 120 breast cancer patients have been treated with this breast conservation technique in our clinic. For each patient, a 3D treatment plan based upon breast and tumor bed volumes delineated on computed tomography (CT) was developed. Segmented tangent fields were iteratively created to reduce "hot spots" produced by traditional tangents. The tumor bed received a concomitant boost with additional conformal photon beams. The final tumor bed boost was delivered either with conformal photon beams or conventional electron beams. All patients received 45 Gy to the breast target, plus an additional 5 Gy to the surgical excision site, bringing the total dose to 50 Gy to the boost target volume in 25 fractions. The final boost to the excision site brought the total target dose to 60 Gy. With minimum follow-up of 4 months and median follow-up of 11 months, all patients have excellent cosmetic results. There has been minimal breast edema and minimal skin changes. There have been no local relapses to date. Forward planning of multi-segment fields is facilitated with 3D planning and multileaf collimation. The treatment technique offers improvement in target dose homogeneity and the ability to confidently concomitantly boost the excision site. The technique also offers the advantage for physics and therapy staff to develop familiarity with multiple segment fields, as a precursor to intensity-modulated radiation therapy (IMRT) techniques.

Repeat breast-conserving surgery for in-breast local breast carcinoma recurrence: the potential role of partial breast irradiation

Mastectomy is the current standard of care for in-breast local recurrence of breast carcinoma. The objective of the current study was to critically review the rationale for and the theoretic and actual risks and benefits of repeat breast-conserving surgery followed by partial breast irradiation (PBI) for in-breast local recurrence of breast carcinoma. The main outcomes of interest were local control and survival after in-breast local recurrence and side effects, complications, and cosmesis after reirradiation of the breast. The risk of local recurrence was not found to be eliminated with mastectomy; approximately 2-32% of patients treated with mastectomy develop a chest wall recurrence. The interpretation of local control rates in evaluating repeat breast-conserving surgery studies is difficult because of the lack of information regarding preoperative diagnostic mammography to rule out concurrent multicentric disease and microscopic margin status after surgery. Rates of subsequent local recurrence in these studies appeared to be between 19-50%, similar to reported rates of in-breast local recurrence in patients with a first diagnosis of breast carcinoma who were treated with conservative surgery without irradiation. Early follow-up studies of breast reirradiation suggest that catheter-based interstitial brachytherapy and standard external beam radiation therapy can be delivered to the breast more than once without significant side effects in most patients and with acceptable cosmesis in some patients. Mastectomy may not be necessary in all patients with an in-breast local recurrence of breast carcinoma. Recent advances in conformal radiation delivery and single-center published reports concerning repeat breast-conserving therapy support well designed prospective trials to formally test this hypothesis.

Accelerated partial breast irradiation after conservative surgery for breast cancer

OBJECTIVE

To critically review the theoretical and actual risks and benefits of accelerated partial breast irradiation (APBI) after breast-conserving surgery.

SUMMARY BACKGROUND DATA

Because of rapid evolution of radiation therapy techniques related to brachytherapy and three-dimensional conformal radiation therapy, APBI has very recently come to the forefront as a potential local treatment option for women with breast cancer. This review aims to give an overview of the biologic rationale for APBI techniques, and benefits and limitations of APBI techniques.

METHODS

The authors reviewed the currently available published world medical literature on breast-conserving surgery with and without postoperative irradiation; all studies involving partial breast irradiation, including brachytherapy, for breast cancer; and currently accruing and planned APBI trials. The focus of this review was the early results of treatment in terms of toxicity, complications, cosmesis, and local control.

RESULTS

On average, approximately 3% of patients treated with breast-conserving surgery will have an in-breast local recurrence away from the original lumpectomy site with or without postoperative standard whole-breast irradiation. The results of phase I-II studies involving approximately 500 patients treated with APBI after breast-conserving surgery have been published. Although many of the studies have limited long-term follow-up and potential selection bias, early results suggest that toxicity, cosmesis, and local control are comparable to outcomes seen after breast-conserving surgery followed by standard whole-breast irradiation.

CONCLUSIONS

Recent advances in radiation delivery and published series of partial breast irradiation support large randomized trials comparing APBI with standard whole-breast irradiation after breast-conserving surgery.

Analysis of a large number of clinical studies for breast cancer radiotherapy: estimation of radiobiological parameters for treatment planning

Numerous studies of early-stage breast cancer treated with breast conserving surgery (BCS) and radiotherapy (RT) have been published in recent years. Both external beam radiotherapy (EBRT) and/or brachytherapy (BT) with different fractionation schemes are currently used. The present RT practice is largely based on empirical experience and it lacks a reliable modelling tool to compare different RT modalities or to design new treatment strategies. The purpose of this work is to derive a plausible set of radiobiological parameters that can be used for RT treatment planning. The derivation is based on existing clinical data and is consistent with the analysis of a large number of published clinical studies on early-stage breast cancer. A large number of published clinical studies on the treatment of early breast cancer with BCS plus RT (including whole breast EBRT with or without a boost to the tumour bed, whole breast EBRT alone, brachytherapy alone) and RT alone are compiled and analysed. The linear quadratic (LQ) model is used in the analysis. Three of these clinical studies are selected to derive a plausible set of LQ parameters. The potential doubling time is set a priori in the derivation according to in vitro measurements from the literature. The impact of considering lower or higher T(pot) is investigated. The effects of inhomogeneous dose distributions are considered using clinically representative dose volume histograms. The derived LQ parameters are used to compare a large number of clinical studies using different regimes (e.g., RT modality and/or different fractionation schemes with different prescribed dose) in order to validate their applicability. The values of the equivalent uniform dose (EUD) and biologically effective dose (BED) are used as a common metric to compare the biological effectiveness of each treatment regime. We have obtained a plausible set of radiobiological parameters for breast cancer: alpha = 0.3 Gy(-1), alpha/beta = 10 Gy and sub-lethal damage repair time T(rep) = 1 h (mono-exponential behaviour is assumed). This set of parameters is consistent with in vitro experiments and with previously reported analyses. Using this set of parameters, we have found that most of the studies, using BCS plus whole breast RT and a boost to the tumour bed, have EUDs ranging from 60-70 Gy. No correlation is found between BED and the local recurrence rate. The treatments of BCS plus brachytherapy alone have a wide range of EUD (30-50 Gy), which is significantly lower than the treatments with whole breast EBRT plus a boost of the tumour bed. The studies with different fractionation schemes for whole breast EBRT also show a significant variation of EUD. Carefully designed clinical studies with large numbers of patients are required to determine clinically the relative effectiveness of these treatment variations. The derived LQ parameter set based on clinical data is consistent with in vitro experiments and previous studies. As demonstrated in the present work, these radiobiological parameters can be potentially useful in radiotherapy treatment planning for early breast cancer, e.g., in comparing biological effectiveness of different radiotherapy modalities, different fractionation schemes and in designing new treatment strategies.

Potential of mobile intraoperative radiotherapy technology

Mobile IORT units have the potential to change the way patients who have cancer are treated. The integration of IORT into cancer treatment programs, made possible by the new technologies of mobile linear accelerators that can be used in unshielded operating rooms, makes IORT significantly less time-consuming, less costly, and less risky to administer. It is now practical for IORT to be used in early-stage disease, in addition to advanced disease, and in sites for which patient transportation in the middle of surgery is considered too risky. Preliminary results of trials for early-stage breast and rectal cancer indicate benefits of IORT. Pediatric patients and patients who have lung cancer, previously underserved by IORT therapies, can be offered potential gains when patient transport issues do not limit IORT. Furthermore, because many of these mobile systems require no shielding, it is now practical for mobile units to be shared between hospitals, making this new mobile technology much more widely available.

Intraoperative radiation therapy for breast cancer

The rapid patient accrual observed in the European breast IORT studies reported since 2000 indicates that surgeons, radiation oncologists, and women who have breast cancer are no longer content to continue to travel down the well-worn path of disfiguring ablative treatment. Breast conservation is currently viewed as the preferred mode of therapy for early-stage breast cancer in most clinical situations. Determination of the optimal combination of whole breast EBRT and localized IORT, for dose and fractionation, is a critical issue that only recently has been addressed [20,21]. Clearly, such clinical investigative endeavors should be regarded as high priority. The very low incidence of local in-breast recurrence of cancer to date suggests that another avenue for investigation might be the determination of the extent to which the lumpectomy procedure can be safely minimized when used in conjunction with IORT. For example, physicians might ask, "Are microscopically negative surgical margins still mandatory when IORT is applied at the time of lumpectomy?" If the answer to that question should turn out to be "no," then it should be much easier for surgeons to achieve the desired excellent cosmetic results when dealing with early-stage breast cancer. Another question remaining to be addressed pertains to the utility of IORT in the management of in-breast recurrence of cancer following conservative therapy. The incidence of local failure after organ-conserving treatment is generally reported to be approximately 5% to 10%. Currently, the preferred mode of salvage therapy in such a clinical situation is mastectomy. The proven efficacy of IORT concurrent with lumpectomy in the primary treatment of early-stage breast cancer suggests that even local recurrences following conventional conservative treatment might be dealt with effectively and expeditiously by means of local excision plus IORT. Such treatment, if safe and effective, could prove to be much less disfiguring than mastectomy. Because breast irradiation routinely produces a desmoplastic tissue response in the breast, there seems to be an opportunity here to address local recurrences of breast cancer with local surgical extirpation enhanced by IORT. Because there are currently few data regarding the use of IORT in this clinical situation, pilot studies would seem to be justified. The remarkably low incidence of local recurrence of breast malignancy observed in every breast IORT study reported to date may portend an important advancement in physicians' ability to better achieve local control of mammary carcinoma. It is hoped that such a putative improvement in the local control of breast cancer will soon translate into improved patient survival rates for this common malignancy.