A clinical study of curative partial breast irradiation for stage I breast cancer using carbon ion radiotherapy

Dosimetric analysis of six whole-breast irradiation techniques in supine and prone positions

In breast cancer radiation therapy, minimizing radiation-related risks and toxicity is vital for improving life expectancy. Tailoring radiotherapy techniques and treatment positions can reduce radiation doses to normal organs and mitigate treatment-related toxicity. This study entailed a dosimetric comparison of six different external beam whole-breast irradiation techniques in both supine and prone positions. We selected fourteen breast cancer patients, generating six treatment plans in both positions per patient. We assessed target coverage and organs at risk (OAR) doses to evaluate the impact of treatment techniques and positions. Excess absolute risk was calculated to estimate potential secondary cancer risk in the contralateral breast, ipsilateral lung, and contralateral lung. Additionally, we analyzed the distance between the target volume and OARs (heart and ipsilateral lung) while considering the treatment position. The results indicate that prone positioning lowers lung exposure in X-ray radiotherapy. However, particle beam therapies (PBTs) significantly reduce the dose to the heart and ipsilateral lung regardless of the patient's position. Notably, negligible differences were observed between arc-delivery and static-delivery PBTs in terms of target conformity and OAR sparing. This study provides critical dosimetric evidence to facilitate informed decision-making regarding treatment techniques and positions.

Locoregional Ablative Radiation Therapy for Patients With Breast Cancer Unsuitable for Surgical Resection

PURPOSE

Patients with breast cancer who are unsuitable for surgical resection are typically managed with palliative systemic therapy alone. We report outcomes of 5-fraction ablative radiation therapy for nonresected breast cancers.

METHODS AND MATERIALS

This is a retrospective analysis of an institutional registry of patients with breast cancer who were unsuitable for resection and underwent 35 to 40 Gy/5 fractions to the primary breast tumor or regional lymph nodes from 2014 to 2021. Primary outcomes were cumulative incidence of local failure and grade ≥3 toxicity (Common Terminology Criteria for Adverse Events, version 5.0).

RESULTS

We reviewed 57 patients who received 61 treatment courses (median age of 81 years; range, 38-99). Unresectable tumor (10%), patient refusal (18%), medical inoperability (35%), and metastatic disease (37%) were the causes of not having surgery. Five patients (8%) had previously undergone adjuvant locoregional radiation therapy. Fifty-four percent (n = 33/61) of treatment courses targeted the breast only, 31% (n = 19/61) both the breast and lymph nodes, and 15% (n = 9/61) the lymph nodes only. Sixty-seven percent (n = 35/52) of the courses that targeted the breast were delivered with partial breast irradiation and 33% (n = 17/52) with whole breast radiation therapy (median dose of 25 Gy in 5 fractions) ± simultaneous integrated boost to the primary tumor. Most primary tumors (65%, n = 34/52) and target lymph nodes (61%, n = 17/28) were treated with a dose of 35 Gy in 5 fractions. Most treatments (52%) were delivered with intensity modulated radiation therapy (IMRT). Radiation therapy was delivered daily (20%), every other day (18%), twice weekly (36%), or weekly (26%). The 2-year cumulative incidence of local failure was 11.4% and grade≥3 toxicity was 15.1%. The grade ≥3 toxicity was 6.5% for IMRT treatments, versus 7.7% for non-IMRT treatments targeting partial breast or lymph nodes (hazard ratio, 1.13, P = .92), versus 38.9% for non-IMRT treatments targeting the entire breast (hazard ratio, 6.91, P = .023). All grade ≥3 toxicity cases were radiation dermatitis. No cases of brachial plexopathy were observed.

CONCLUSIONS

Thirty-five to 40 Gy in 5 fractions is a safe and effective breast stereotactic body radiation therapy (SBRT) regimen and may be an attractive option for patients who are not surgical candidates. Highly conformal techniques (ie, IMRT or partial breast irradiation) were associated with a reduced risk of toxicity and should be the preferred treatment approaches.

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.

Recent advances progress in radiotherapy for breast cancer after breast-conserving surgery: a review

Adjuvant radiotherapy after breast-conserving surgery has become an integral part of the treatment of breast cancer. In recent years, the development of radiotherapy technology has made great progress in this field, including the comparison of the curative effects of various radiotherapy techniques and the performance of the segmentation times. The choice of radiotherapy technology needs to be co-determined by clinical evidence practice and evaluated for each individual patient to achieve precision radiotherapy. This article discusses the treatment effects of different radiotherapy, techniques, the risk of second cancers and short-range radiation therapy techniques after breast-conserving surgery such as hypo fractionated whole breast irradiation and accelerated partial breast irradiation. The choice of radiotherapy regimen needs to be based on the individual condition of the patient, and the general principle is to focus on the target area and reduce the irradiation of the normal tissues and organs. Short-range radiotherapy and hypofractionated are superior to conventional radiotherapy and are expected to become the mainstream treatment after breast-conserving surgery.

Particle radiotherapy for breast cancer

Breast cancer is the most common malignant tumor in female patients. Along with surgery, radiotherapy is one of the most commonly prescribed treatments for breast cancer. Over the past few decades, breast cancer radiotherapy technology has significantly improved. Nevertheless, related posttherapy complications should not be overlooked. Common complications include dose-related coronary toxicity, radiation pneumonia, and the risk of second primary cancer of the contralateral breast. Particle radiotherapy with protons or carbon ions is widely attracting interest as a potential competitor to conventional photon radiotherapy because of its superior physical and biological characteristics. This article summarizes the results of clinical research on proton and carbon-ion radiotherapy for treating breast cancer.

Non-Surgical Definitive Treatment for Operable Breast Cancer: Current Status and Future Prospects

This article reviews the results of various non-surgical curative treatments for operable breast cancer. Radiotherapy is considered the most important among such treatments, but conventional radiotherapy alone and concurrent chemoradiotherapy do not achieve high cure rates. As a radiosensitization strategy, intratumoral injection of hydrogen peroxide before radiation has been investigated, and high local control rates (75-97%) were reported. The authors treated 45 patients with whole-breast radiotherapy, followed by stereotactic or intensity-modulated radiotherapy boost, with or without a radiosensitization strategy employing either hydrogen peroxide injection or hyperthermia plus oral tegafur-gimeracil-oteracil potassium. Stages were 0-I in 23 patients, II in 19, and III in 3. Clinical and cosmetic outcomes were good, with 5-year overall, progression-free, and local recurrence-free survival rates of 97, 86, and 88%, respectively. Trials of carbon ion radiotherapy are ongoing, with promising interim results. Radiofrequency ablation, focused ultrasound, and other image-guided ablation treatments yielded complete ablation rates of 20-100% (mostly ≥70%), but long-term cure rates remain unclear. In these treatments, combination with radiotherapy seems necessary to treat the extensive intraductal components. Non-surgical treatment of breast cancer is evolving steadily, with radiotherapy playing a major role. In the future, proton therapy with the ultra-high-dose-rate FLASH mode is expected to further improve outcomes.

Basic and translational research on carbon-ion radiobiology

Carbon-ion beam irradiation (IR) has evident advantages over the conventional photon beams in treating tumors. It releases enormous amount of energy in a well-defined range with insignificant scatter in surrounding tissues based on well-localized energy deposition. Over the past 28 years, more than 14,000 patients with various types of cancer have been treated by carbon ion radiotherapy (CIRT) with promising results at QST. I have provided an overview of the basic and translational research on carbon-ion radiobiology including mechanisms underlying high linear energy transfer (LET) carbon-ion IR-induced cell death (apoptosis, autophagy, senescence, mitotic catastrophe etc.) and high radiocurability produced by carbon-ion beams in combination with DNA damaging drugs or with molecular-targeted drugs, micro-RNA therapeutics and immunotherapy. Additionally, I have focused on the application of these treatment in human cancer cells, especially cancer stem cells (CSCs). Finally, I have summarized the current studies on the application of basic carbon-ion beam IR according to the cancer types and clinical outcomes.

Stereotactic Partial Breast Irradiation: What Does the Future Hold?

Breast irradiation has evolved significantly over the last several decades. Accelerated partial breast and stereotactic breast irradiation have evolved as strategies to reduce irradiated volumes, preserve appropriate oncologic control, and improve cosmetic outcome. The sequencing and/or combination of stereotactic partial breast irradiation with novel systemic agents is of great interest to the oncologic community. Here we explore the landscape of modern trials and opine on the future of partial breast irradiation.

Definitive radiotherapy with stereotactic or IMRT boost with or without radiosensitization strategy for operable breast cancer patients who refuse surgery

For breast cancer (BC) patients who refused surgery, we developed a definitive treatment employing modern sophisticated radiation techniques. Thirty-eight operable BC patients were treated by conventionally fractionated whole-breast (WB) radiotherapy in combination with stereotactic (for primary tumor) or intensity-modulated (for primary tumor with/without regional lymph nodes [LN]) radiotherapy (IMRT) boost. Standard doses were 50 Gy/25 fractions, 21 Gy/3 fractions and 20 Gy/8 fractions, respectively, for the three radiation modalities. Disease stages were 0 (ductal carcinoma in situ [DCIS]) in seven patients, I in 12, II in 16 and III in three. In 26 patients, intratumoral hydrogen peroxide injection or hyperthermia with oral tegafur-gimeracil-oteracil potassium (S-1) was also used to sensitize the tumors to radiation. Hormonal and standard systemic therapy were administered in 25 and 13 patients, respectively. Complete and partial responses were obtained in 19 patients each; in patients with partial response, no further regrowth of the residual mass was observed, except for two patients who developed local recurrence. During a follow-up of 8-160 months (median, 50 months for living patients), two, one and two patients developed local relapse, sub-clavicular node metastasis and distant metastasis, respectively. The 5-year rates for overall, progression-free and local relapse-free survival were 97.2, 90.9 and 93.4%, respectively. Fourteen patients developed Grade 3 radiation dermatitis but all recovered after treatment. In 47%, the affected breast became better-rounded, and the nipple of the irradiated breast became higher by ≥1 cm than the contralateral nipple. Our method might be a treatment option for operable BC patients.

Combining Carbon-Ion Irradiation and PARP Inhibitor, Olaparib Efficiently Kills BRCA1-Mutated Triple-Negative Breast Cancer Cells

Background:

Triple-negative breast cancer (TNBC) exhibits poor prognosis due to the lack of targets for hormonal or antibody-based therapies, thereby leading to limited success in the treatment of this cancer subtype. Poly (ADP-ribose) polymerase 1 (PARP1) is a critical factor for DNA repair, and using PARP inhibitor (PARPi) is one of the promising treatments for BRCA-mutated (BRCA mut) tumors where homologous recombination repair is impaired due to BRCA1 mutation. Carbon ion (C-ion) radiotherapy effectively induces DNA damages in cancer cells. Thus, the combination of C-ion radiation with PARPi would be an attractive treatment for BRCA mut TNBC, wherein DNA repair systems can be severely impaired on account of the BRCA mutation. Till date, the effectiveness of C-ion radiation with PARPi in BRCA mut TNBC cell killing remains unknown.

Purpose:

Triple-negative breast cancer cell lines carrying either wild type BRCA1, BRCA wt, (MDA-MB-231), or the BRCA1 mutation (HCC1937) were used, and the effectiveness of PARPi, olaparib, combined with C-ion beam or the conventional radiation, or X-ray, on TNBC cell killing were investigated.

Methods:

First, effective concentrations of olaparib for BRCA mut (HCC1937) cell killing were identified. Using these concentrations of olaparib, we then investigated their radio-sensitizing effects by examining the surviving fraction of MDA-MB-231 and HCC1937 upon X-ray or C-ion irradiation. In addition, the number of γH2AX (DSB marker) positive cells as well as their expression levels were determined by immunohistochemistry, and results were compared between X-ray irradiated or C-ion irradiated cells. Furthermore, PARP activities in these cells were also observed by performing immunohistochemistry staining for poly (ADP-ribose) polymer (marker for PARP activity), and their expression differences were determined.

Results:

Treatment of cells with 25 nM olaparib enhanced radio-sensitivity of X-ray irradiated HCC1937, whereas lower dose (5 nM) olaparib showed drastic effects on increasing radio-sensitivity of C-ion irradiated HCC1937. Similar effect was not observed in MDA-MB-231, not possessing the BRCA1 mutation. Results of immunohistochemistry showed that X-ray or C-ion irradiation induced similar number of γH2AX-positive HCC1937 cells, but these induction levels were higher in C-ion irradiated HCC1937 with increased PARP activity compared to that of X-ray irradiated HCC1937. Elevated induction of DSB in C-ion irradiated HCC937 may fully activate DSB repair pathways leading to downstream activation of PARP, subsequently enhancing the effectiveness of PARPi, olaparib, with lower doses of olaparib exerting noticeable effects in cell killing of C-ion irradiated HCC1937.

Conclusions:

From this study, we demonstrate that C-ion irradiation can exert significant DSB in BRCA mut TNBC, HCC1937, with high PARP activation. Thus, PARPi, olaparib, would be a promising candidate as a radio-sensitizer for BRCA mut TNBC treatment, especially for C-ion radiotherapy.

Particle Therapy for Breast Cancer

Particle therapy has received increasing attention in the treatment of breast cancer due to its unique physical properties that may enhance patient quality of life and reduce the late effects of therapy. In this review, we will examine the rationale for the use of proton and carbon therapy in the treatment of breast cancer and highlight their potential for sparing normal tissue injury. We will discuss the early dosimetric and clinical studies that have been pursued to date in this domain before focusing on the remaining open questions limiting the widespread adoption of particle therapy.

Hadrontherapy techniques for breast cancer

Radiotherapy plays a key role in breast cancer treatment, and recent technical advances have been made to improve the therapeutic window by limiting the risk of radiation-induced toxicity or by increasing tumor control. Hadrontherapy is a form a radiotherapy relying on particle beams; compared with photon beams, particle beams have specific physical, radiobiological and immunological properties, which can be valuable in diverse clinical situations. To date, available hadrontherapy techniques for breast cancer irradiation include proton therapy, carbon ion radiation therapy, fast neutron therapy and boron neutron capture therapy. This review analyzes the current rationale and level of evidence for each hadrontherapy technique for breast cancer.

Particle Therapy for Breast Cancer: Benefits and Challenges

Hadron therapy with protons and carbon ions is widely attracting interest as a potential competitor of conventional photon radiotherapy. Exquisite dose distribution of charged particles allows for a higher local control of the tumor and lower probability of damage to nearby healthy tissues. Heavy ions have presumed biological advantages rising from their high-linear energy transfer (LET) characteristics, including greater cell-killing effectiveness and reduced heterogeneity dependence of radiation response. Although these advantages are clear and supported by data, only 18.0% of proton and carbon ion radiotherapy (CIRT) facilities in Europe are treating breast cancers. This review summarizes the physical and radiobiological properties of charged particles, clinical use of particle beam for breast cancer, and suggested approaches to overcome technical and financial challenges.