Definitive single fraction stereotactic ablative radiotherapy for inoperable early-stage breast cancer: A case report

Stereotactic body radiation therapy (SBRT) for the treatment of primary breast cancer in patients not undergoing surgery

PURPOSE

The purpose was to explore the role of stereotactic body radiation therapy (SBRT) in providing local control (LC) for primary breast cancer in patients unable to undergo surgery.

MATERIALS/METHODS

Between 2015 and 2019, 13 non-surgical candidates with 14 lesions were treated with SBRT for primary breast cancer. In 4 cases, SBRT was used after whole breast radiation therapy (WBRT; 40-50 Gy/20-25 fractions). SBRT dose was 30-40 ​Gy in 5 fractions for patients treated with SBRT alone and 25-32 ​Gy in 4-5 fractions for those treated with SBRT ​+ ​WBRT. LC and overall survival (OS) were estimated using Kaplan-Meier curves. Response was also assessed using RECIST guidelines.

RESULTS

Median follow-up was 32 (range: 3.4-70.4) months. Imaging at median 2.2 (0.6-8.1) months post-SBRT showed median 43.2 ​% (range: 2-100 ​%) decrease in the largest diameter and median 68.7 ​% (range: 27.9-100 ​%) SUV reduction. There were 3 cases of local progression at 8.7-10.6 months. Estimated LC was 100 ​% at 6 months and 71.6 ​% at 12, 24 and 36 months. Estimated median OS was 100 ​% at 6 months, 76.9 ​% at 12 months, and 61.5 ​% at 24 and 36 months. Acute toxicity (n ​= ​13; 92.9 ​%) included grade (G)1 (n ​= ​8), G2 (n ​= ​4), and G4 (necrosis; n ​= ​1). Late toxicity included G2 edema (n ​= ​1) and G4 necrosis (n ​= ​2, including 1 consequential late effect). Only patients treated with SBRT ​+ ​WBRT experienced acute/late G4 toxicity, managed with resection or steroids.

CONCLUSIONS

SBRT to primary breast cancer resulted in good LC in non-surgical/metastatic patients. Although necrosis (n ​= ​2) occurred in the SBRT ​+ ​WBRT group, it was successfully salvaged.

Utility of Stereotactic Body Radiation Therapy in Establishing Local Control for Patients With Invasive Breast Cancer Not Undergoing Definitive Surgery

PURPOSE

Surgery is the backbone of breast cancer (BC) treatment. For patients who cannot undergo surgery, improving local control (LC) of the primary tumor is paramount. To that end, this study explored the role of stereotactic body radiation therapy (SBRT).

METHODS AND MATERIALS

Between 2015 and 2022, 21 nonsurgical candidates (10 metastatic, 11 stage IA-IIIC) received 23 SBRT courses to primary BC. Seven were analyzed retrospectively; 15 are currently enrolled in a prospective study. SBRT (40 Gy/5 fractions) was delivered every other day. Follow-up imaging was reviewed. Acute (≤3 months) and late toxicities were evaluated using Common Terminology Criteria for Adverse Events, version 5. LC and overall survival (OS) were estimated using Kaplan-Meier curves.

RESULTS

Median age was 78.4 years (45.9-97.3). Median follow-up was 14.7 months (3.3-70.3). Median pre-SBRT index lesion size was 3.1 cm (0.5-14.5) and planning treatment volume was 32.4 cc (11.5-522.4). Initial posttreatment imaging performed at a median 4.0 months (0.6-11.9) post-SBRT demonstrated median decrease in index lesion size of 20.8% (0%-100%); SUV reduction of 65.2% (20.8%-100%). Second follow-up scans at a median 7.8 months post-SBRT showed 62% (0%-100%) and 88% (33.3%-100%) median reduction in tumor size and SUV, respectively, compared with pre-SBRT values. The estimated LC rate was 100% at 6 months and 93.3% at 12, 24, and 36 months. Local progression occurred in 1 case 9.5 months after SBRT, after an initial response. Regional progression occurred in 4 cases (17.4%) at a median 18.6 months (5.2-22.7) post-SBRT. Six patients (35.3%) developed distant progression at a median 2.7 months (0.9-16.2). The estimated OS was 85.7% at 6 months, 69.6% at 12 months, and 63.8% at 24 and 36 months. The rates of acute toxicity were G1: 47.8%, G2: 4.3%, G3: 8.7%, and G4: 0%.

CONCLUSIONS

Definitive SBRT for primary BC resulted in good LC in nonsurgical patients and was well-tolerated. Considering the pattern of progression, additional approaches to improve regional/distant control should be investigated.

Definitive ablative stereotactic partial breast irradiation in early stage inoperable breast cancer

PURPOSE

This case series and literature review aims to investigate the efficacy and safety of definitive ablative radiation therapy as a treatment modality for non-operable patients with early stage breast cancer. We present two cases demonstrating the potential of this approach to achieve durable responses.

METHODS

We assessed the long-term response of two non-operable patients diagnosed with Stage II (cT2N0M) and Stage IA (T1bN0M0) invasive ductal carcinoma (IDC), who were deemed unfit for surgery due to significant co-morbid conditions. Definitive ablative radiation therapy was administered using stereotactic partial breast irradiation with ablative doses delivered in either a single fraction or two fractions. Serial imaging was conducted to assess treatment response and monitor adverse events.

RESULTS

Both patients exhibited notable treatment responses following definitive ablative radiation therapy. The first patient, an 84-year-old woman, experienced a 69% reduction in tumor size over a follow-up period exceeding 2 years. The second patient, an 87-year-old woman, achieved complete resolution of disease on imaging, with no signs of progression even 26 month post-treatment. Both patients tolerated the treatment well, without significant treatment-related adverse events.

CONCLUSIONS

Our case series suggests that definitive ablative radiation therapy may serve as a safe and effective treatment option for non-operable patients with early stage breast cancer. The observed durable treatment responses and minimal toxicity support the potential of this approach. Furthermore, a longer interval between ablative radiation therapy and surgery may enhance treatment response, potentially leading to increased complete pathologic response rates.