Preliminary result of accelerated partial breast irradiation after breast-conserving surgery

Feasibility of accelerated partial breast irradiation with strut-adjusted volume implant brachytherapy in Japan focusing on dosimetry and acute toxicity: a Japanese multi-institutional prospective study

BACKGROUND

A Japanese multi-institutional prospective study was initiated to investigate the effectiveness and safety of accelerated partial breast irradiation (APBI) using strut-adjusted volume implant (SAVI) brachytherapy, with subjects registered between 2016 and 2021. Herein, we report the preliminary results on the feasibility of this treatment modality in Japan, focusing on the registration process, dosimetry, and acute toxicities.

PATIENTS AND METHODS

Primary registration was conducted before breast-conserving surgery (BCS) and the eligibility criteria included the following: age ≥ 40 years, tumor unifocal and unicentric, ≤ 3 cm in diameter, cN0M0, proven ductal, mucinous, tubular, medullary, or lobular carcinoma by needle biopsy. Secondary registration was conducted after BCS had been performed leaving a cavity for device implantation and pathological evaluations, and the eligibility criteria were as follows: negative surgical margin, tumor ≤ 3 cm in diameter on gross pathological examination, histologically confirmed ductal, mucinous, tubular medullary, colloid, or lobular carcinoma, pN0, L0V0, no extensive ductal component, no initiation of chemotherapy within 2 weeks of the brachytherapy APBI planning with SAVI was performed for the patients successfully entered in the study by the secondary registration process, and the treatment was administered at the dose of 34 Gy in 10 fractions administered twice daily.

RESULTS

Between 2016 and 2021, 64 women were enrolled in the study through primary registration, of which 19 were excluded from the secondary registration process, and in one, it was deemed impossible to comply with the dose constraints established during treatment planning. After the exclusion of these latter 20 patients, we treated the remaining 44 patients by APBI with SAVI. The dose constraints could be adhered to in all the patients, but re-planning was necessitated in 3 patients because of applicator movement during the treatment period. Grade 2 acute toxicities were observed in 18% of all patients, but more severe acute toxicities than Grade 2 were not observed in any of the patients.

CONCLUSION

APBI with SAVI brachytherapy is feasible in Japan from the aspects of compliance with dose constraints and frequency of acute toxicities.

Preliminary outcomes of accelerated partial breast irradiation by interstitial multicatheter brachytherapy with intraoperative free-hand catheter implantation in early breast cancer

BACKGROUND

To evaluate the clinical feasibility of interstitial brachytherapy by intraoperative free-hand catheter implantation in the treatment of early breast cancer after breast-conserving surgery (BCS).

METHODS

Between January 2018 and December 2019, 44 patients with early breast cancer after BCS who met the inclusion criteria ≥45 years old, invasive carcinoma ≤3 cm or ductal carcinoma in situ <2.5 cm, estrogen receptor positive, lymph node negative, surgical margin negative, no distant metastasis, and an ECOG performance score ≤1 were enrolled in this phase II single-arm study. The postoperative irradiation field includes the tumor bed plus 2-cm margin in all directions, except in the anterior-posterior direction. The total prescribed tumor dose was 3400 cGy delivered in 10 fractions twice daily at 6-hour intervals. The primary endpoints were acute side effects, late treatment-related toxicity, and cosmetic outcome. The secondary endpoints were local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), distant metastasis-free survival (DMFS), and overall survival (OS).

RESULTS

The median follow-up time was 33.5 months (mean, 32.9 months; range, 20-43 months). The cosmetic results were good to very good in 92.3% of the questionnaire respondents. The acute toxicities were mild, and no acute grade 3-4 toxicity was noted. Wound infection was noted in two patients (4.5%). There was only one event of regional lymph node recurrence in one patient. The 3-year LRFS, DMFS, and OS were 100%, and RRFS was 94.7%. For two patients who had a positive lymph node based on their final pathology reports, postoperative irradiation, including whole breast and regional lymph nodes, was added.

CONCLUSION

Accelerated partial breast irradiation using interstitial brachytherapy with the intraoperative free-hand catheter implantation technique provides an alternative method of postoperative radiotherapy for selected patients with early breast cancer after BCS with acceptable toxicities.

A Japanese prospective multi-institutional feasibility study on accelerated partial breast irradiation using multicatheter interstitial brachytherapy: clinical results with a median follow-up of 60 months

BACKGROUND

We carried out the first multi-institutional prospective study on accelerated partial breast irradiation (APBI) via multicatheter interstitial brachytherapy in a shorter period for early breast cancer in Japan.

METHODS

Patient eligibility criteria included positive hormone receptors, tumors ≤ 3 cm and TNM stage pN0M0. After breast-conserving surgery (Japanese cylindrical resection) and histological confirmation of negative surgical margins and the absence of lymph node metastasis, applicator implantation was performed either postoperatively or intraoperatively. High-dose-rate brachytherapy of 36 Gy in 6 fractions was delivered.

RESULTS

Forty-six patients from six institutions received this treatment regimen, and the median follow-up time was 60 months (range 57-67 months). The median resected breast tissue volume was 81 cm³ (range 28-260 cm³). No Grade 4 late sequela, local recurrence nor death due to breast cancer were observed. Grade 2-3 sequelae such as rib fracture (2%), soft tissue necrosis (9%), fibrosis (20%), and breast pain (9%) were observed. The resected breast tissue volumes of the patients who had Grade ≥ 2 fibrosis and Grade < 2 fibrosis were 105.9 ± 32.3 cm³ and 76.3 ± 45.6 cm³, respectively, p = 0.02. The overall cosmetic outcome score of Excellent/Good was 74% at 60 months after APBI. Grade ≥ 1 fibrosis was observed in 44% and 92% of patients who scored Excellent/Good and Fair/Poor, respectively, p = 0.004.

CONCLUSIONS

This study showed excellent local control and survival results with minimal late sequelae.

Modern development of high-dose-rate brachytherapy

Brachytherapy is an invasive therapy with placement of radiation source into or near the tumor. The difference between planning target volume and clinical target volume is minimal, and the dose out of the tumor reduces rapidly due to the inverse-square law. High-dose-rate brachytherapy enables three-dimensional image guidance, and currently, tumor dose as well as doses of the surrounding normal structures can be evaluated accurately. High-dose-rate brachytherapy is the utmost precision radiation therapy even surpassing carbon ion therapy. Biological disadvantages of high-dose rate have been overcome by the fractional irradiation. High-dose-rate brachytherapy is indispensable in the definitive radiation therapy of cervical cancer. Also in prostate cancer and breast cancer, high-dose-rate brachytherapy plays a significant role. Brachytherapy requires techniques and skills of radiation oncologists at the time of invasive placement of the radiation source into the tumor area. Education of young radiation oncologists is most urgent and important.

Case report of a dose-volume histogram analysis of rib fracture after accelerated partial breast irradiation: interim analysis of a Japanese prospective multi-institutional feasibility study

We initiated the first multi-institutional prospective study of accelerated partial breast irradiation for early breast cancer in Japan. Our early clinical results showed that the treatment methods were technically reproducible between institutions and showed excellent disease control at a median follow-up of 26 months in our previous report. At present, total 46 patients from six institutions underwent the treatment regimen from October 2009 to December 2011, and the median follow-up time was 60 months (range, 57-67 months). In 46 patients, we experienced one patient who had rib fracture as a late complication. The dose-volume histogram (DVH) result of this patient was analyzed. The D_0.01cc, D_0.1cc, and D_1cc values of the patient were 913, 817, and 664 cGy per fraction, respectively. These values were the highest values in 46 patients. The average D_0.01cc, D_0.1cc, and D_1cc values of the other 45 patients were 546, 500, and 419, respectively, cGy per fraction. From this result, DVH values showing high-dose irradiated volume (D_0.01cc, D_0.1cc, and D_1cc) seem to be a good predictive factor of rib fracture for accelerated partial breast irradiation. However, further investigation is necessary because of the small number of patients investigated.

Accelerated partial breast irradiation in an Asian population: dosimetric findings and preliminary results of a multicatheter interstitial program

Introduction

Accelerated partial breast irradiation (APBI) using the multicatheter method has excellent cosmesis and low rates of long-term toxicity. However, there are few studies looking at the feasibility of this procedure and the outcomes in an Asian population. This study aims to look at outcomes at our hospital.

Methods

We identified 121 patients treated with APBI at our center between 2008 and 2014. The median follow-up for our patient group was 30 months (range 3.7–66.5). The prescribed dose per fraction was 3.4 Gy in 10 fractions. In this study population, 71% of the patients were Chinese while 15% (n=19) were of other Asian ethnicity.

Results

In this study, the median breast volume was 850 cc (range 216–2,108) with 59.5% (n=72) patients with a breast volume of <1,000 cc. The average planning target volume was 134 cc (range 28–324). The number of catheters used ranged from 8 to 25 with an average of 18 catheters used per patient. We achieved an average dose homogeneity index of 0.76 in our patients. The average D90(%) was 105% and the average D90(Gy) was 3.6 Gy per fraction. The median volume receiving 100% of the prescribed dose (V100) was 161.7 cc (range 33.9–330.1), 150% of the prescribed dose (V150) and 200% of the prescribed dose (V200) was 39.4 cc (range 14.6–69.6) and 14.72 cc (range 6.48–22.25), respectively. Our dosimetric outcomes were excellent even in patients with breast volume under 1,000 cc. There were no cases of grade 3 skin toxicity or acute pneumonitis. Two patients had a postoperative infection and two patients had fat necrosis postprocedure.

Conclusion

Multicatheter high dose rate APBI is a safe and feasible procedure that can be carried out with minimal toxicity in Asian patients with breast volumes under 1,000 cc.

A Japanese prospective multi-institutional feasibility study on accelerated partial breast irradiation using interstitial brachytherapy: clinical results with a median follow-up of 26 months

BACKGROUND

A Japanese prospective multi-institutional feasibility study on accelerated partial breast irradiation using interstitial brachytherapy was performed. The first clinical results were reported with a median follow-up of 26 months.

PATIENTS AND METHODS

Forty-six female breast cancer patients with positive hormone receptors and tumors ≤3 cm, pN0M0, completed the protocol treatment. After breast-conserving surgery and histological confirmation of negative surgical margins and pN0, brachytherapy applicators were implanted either postoperatively (n = 45) or intraoperatively (n = 1). High-dose-rate brachytherapy of 36 Gy/6 fractions was delivered. All clinical data were prospectively collected using case report forms and the Common Terminology Criteria for Adverse Events ver.3.0.

RESULTS

At the median follow-up of 26 months, no breast cancer recurrence of any type was observed. Sequelae ≥G2 were dermatitis (G2, 7 %), fibrosis (G2, 11 %; G3, 4 %), fracture (G2, 2 %), pain (G2, 7 %; G3, 2 %), and soft tissue necrosis (G2, 6 %). Cosmetic outcomes evaluated by excellent/good scores were 100 % at pre-therapy (n = 46), 94 % at 12 months (n = 46), and 81 % at 24 months (n = 36), respectively.

CONCLUSIONS

Disease control and sequelae were satisfactory due to the strict eligibility and protocol-defined treatment parameters. The cosmetic outcomes were comparable to those of previous Japanese breast-conserving therapy series.

The American Brachytherapy Society consensus statement for accelerated partial breast irradiation

PURPOSE

To develop clinical guidelines for the quality practice of accelerated partial breast irradiation (APBI) as part of breast-conserving therapy for women with early-stage breast cancer.

METHODS AND MATERIALS

Members of the American Brachytherapy Society with expertise in breast cancer and breast brachytherapy in particular devised updated guidelines for appropriate patient evaluation and selection based on an extensive literature search and clinical experience.

RESULTS

Increasing numbers of randomized and single and multi-institution series have been published documenting the efficacy of various APBI modalities. With more than 10-year followup, multiple series have documented excellent clinical outcomes with interstitial APBI. Patient selection for APBI should be based on a review of clinical and pathologic factors by the clinician with particular attention paid to age (≥50 years old), tumor size (≤3cm), histology (all invasive subtypes and ductal carcinoma in situ), surgical margins (negative), lymphovascular space invasion (not present), and nodal status (negative). Consistent dosimetric guidelines should be used to improve target coverage and limit potential for toxicity following treatment.

CONCLUSIONS

These guidelines have been created to provide clinicians with appropriate patient selection criteria to allow clinicians to use APBI in a manner that will optimize clinical outcomes and patient satisfaction. These guidelines will continue to be evaluated and revised as future publications further stratify optimal patient selection.

Accelerated partial breast irradiation: the need for well-defined patient selection criteria, improved volume definitions, close follow-up and discussion of salvage treatment

Breast-conserving therapy, including whole breast irradiation, has become a well-established alternative to mastectomy in early-stage breast cancer patients, with similar survival rates and better cosmetic outcome. However, many women are still treated with mastectomy, due to logistical issues related to the long course of radiotherapy (RT). To reduce mastectomy rates and/or omission of RT after breast-conserving surgery, shorter, hypofractionated RT treatments have been introduced. More recently, the necessity of routinely treating the entire breast in all patients has been questioned, leading to the development of partial breast radiotherapy. With accelerated partial breast irradiation (APBI) these two approaches have been combined: the tumor bed with a 1-2 cm margin is irradiated either intra-operatively (single fraction) or postoperatively over 5-15 days. Different techniques have been developed, including interstitial brachytherapy, intra-cavity brachytherapy, intra-operative radiotherapy and external beam radiotherapy. These techniques are being evaluated in several ongoing phase III studies. Since its introduction, APBI has been the subject of continuous debate. ASTRO and GEC-ESTRO have published guidelines for patient selection for APBI, and strongly recommend that APBI be carried out within ongoing clinical trials. Recently, the patient selection criteria for APBI have also been up for debate, following the publication of results from different groups that do/do not confirm a difference in recurrence risk among the ASTRO defined risk groups. This paper reviews the different APBI techniques, current recommendations for patient selection, available clinical data and ongoing clinical trials. A case report is included to illustrate the need for careful follow-up of patients treated with APBI.

Objective and longitudinal assessment of dermatitis after postoperative accelerated partial breast irradiation using high-dose-rate interstitial brachytherapy in patients with breast cancer treated with breast conserving therapy: reduction of moisture deterioration by APBI

PURPOSE

To objectively evaluate the radiation dermatitis caused by accelerated partial breast irradiation (APBI) using high-dose-rate interstitial brachytherapy.

PATIENTS AND METHODS

The skin color and moisture changes were examined using a newly installed spectrophotometer and corneometer in 22 patients who had undergone APBI using open cavity implant high-dose-rate interstitial brachytherapy (36 Gy in six fractions) and compared with the corresponding values for 44 patients in an external beam radiotherapy (EBRT) control group (50-60 Gy in 25-30 fractions within 5-6 weeks) after breast conserving surgery.

RESULTS

All values changed significantly as a result of APBI. The extent of elevation in a∗ (reddish) and reduction in L∗ (black) values caused by APBI were similar to those for EBRT, with slightly delayed recovery for 6-12 months after treatment owing to the surgical procedure. In contrast, only APBI caused a change in the b∗ values, and EBRT did not, demonstrating that the reduction in b∗ values (yellowish) depends largely on the surgical procedure. The changes in moisture were less severe after APBI than after EBRT, and the recovery was more rapid. The toxicity assessment using the Common Toxicity Criteria, version 3, showed that all dermatitis caused by APBI was Grade 2 or less.

CONCLUSION

An objective analysis can quantify the effects of APBI procedures on color and moisture cosmesis. The radiation dermatitis caused by APBI using the present schedule showed an equivalent effect on skin color and a less severe effect on moisture than the effects caused by standard EBRT.

Radiobiological comparison of hypofractionated accelerated partial-breast irradiation (APBI) and single-dose intraoperative radiotherapy (IORT) with 50-kV X-rays

BACKGROUND AND PURPOSE

Intraoperative radiotherapy (IORT) of the tumor bed in early breast cancer is presently performed with a single dose of 50-kV X-rays from a miniaturized X-ray machine using spherical applicators. The purpose was to model the biological effect of hypofractionated accelerated partial-breast irradiation (APBI) with ten fractions.

MATERIAL AND METHODS

The relative biologic effectiveness (RBE) was estimated from the linear-quadratic (L-Q) formalism including repair of sublethal damage or assuming a constant RBE = 1.2-1.5. The radial distribution of biological effect was assessed from clinical dose-response curves. In accordance with clinical convention, the dose for APBI was prescribed at 1 cm depth in the tumor bed, whereas for IORT it was prescribed at the applicator surface.

RESULTS

The fraction size was fitted to give the same risk of late normal-tissue reaction (fibrosis) as single-dose IORT with a maximum dose of 20 Gy. The isoeffective fraction size at 1 cm depth varied between 1.01 Gy for RBE estimated from the L-Q model and 1.64 Gy for constant RBE. The applicator size and dose prescription point influenced the radial dose distribution. The "sphere of equivalence" within which the risk for local recurrence is the same for whole-breast radiotherapy was predicted to extend to 11-15 mm distance from the applicator for alpha/beta = 10 Gy and 9-13 mm for alpha/beta = 4 Gy for hypofractionated APBI, representing an increase of the sphere of equivalence by 2.5-6 mm relative to single-dose IORT.

CONCLUSION

An increase of the therapeutic window with hypofractionated APBI relative to single-dose IORT should be feasible.

A Contura catheter offers dosimetric advantages over a MammoSite catheter that increase the applicability of accelerated partial breast irradiation

PURPOSE

The purpose of this study was to determine whether a Contura catheter (SenoRx, Inc, Aliso Viejo, CA) can increase the applicability of accelerated partial breast irradiation.

METHODS AND MATERIALS

One hundred eighty-two women with early stage breast carcinomas were treated with postlumpectomy brachytherapy using a Contura multilumen catheter (n=45) or a MammoSite single-lumen catheter (Cytyc Corp, Marlborough, MA) (n=137). Hypothetical MammoSite catheter treatment plans were created for the Contura patients. Treatment planning goals were to (1) avoid a radiation "hot spot" in the skin and (2) have only a small air/fluid pocket next to the balloon.

RESULTS

The median followup was 16 months. Eighty-nine percent (40 of 45) of Contura plans satisfied both treatment planning goals vs. only 36% (16 of 45) of MammoSite plans (p<0.0001). A Contura catheter did not require explantation in 16% (7 of 45) of patients where balloon-to-skin spacing was only 3-6mm and 11% (5 of 45) of patients where there was an air/fluid pocket >10% of the planning target volume for plan evaluation (PTV_EVAL). A MammoSite catheter was explanted in 10% of cases where the minimum balloon-to-skin distance was <7mm and in 13% of cases where there was a large air/fluid pocket next to the balloon. Our incidence rates of acute toxicity with a Contura catheter were similar to those with a MammoSite catheter.

CONCLUSIONS

A Contura catheter provides important dosimetric advantages over a MammoSite catheter and does not require explantation in cases where balloon-to-skin spacing is only 3-6mm or an air/fluid pocket next to the balloon is >10% of PTV_EVAL.