Abstract
Background/Aim: Adjuvant radiotherapy is an integral part of the interdisciplinary curative treatment of breast cancer. We aimed to examine the long-term clinical results of helical tomotherapy in female patients with local restricted, lymph node negative breast cancer after breast-conserving surgery. Patients and Methods: In this single-centre analysis, 219 female patients with early-stage breast cancer (T1/2) and no lymph node metastasis (N0) following breast-conserving surgery and sentinel-node biopsy were treated with adjuvant fractionated whole breast radiation therapy using helical tomotherapy. When boost irradiation was indicated, it was administered sequentially or using the simultaneous-integrated boost technique. Local control (LC), metastasis and survival rates, acute toxicity, late toxicity, and secondary malignancy rates were analysed retrospectively. Results: The mean follow-up time was 71 months. The 5- and 8-year overall survival (OS) rates were 97.7% and 92.1%, respectively. The 5- and 8-year LC rates were 99.5% and 98.2%, while the 5- and 8-year metastasis-free survival (MFS) rates of 97.4% and 94.3%, respectively. Patients with G3 grading or negative hormone receptor status did not show significantly different results. Acute erythema occurred in 79% (grade 0-2) and 21% (grade 3) of the patients. Lymphedema of the ipsilateral arm and pneumonitis occurred in 6.4% and 1.8% of the treated patients. None of the patients developed >grade 3 toxicities during follow-up, while 1.8% developed a secondary malignancy during follow-up. Conclusion: Helical tomotherapy showed excellent long-term results and low toxicity rates. The incidence rates of secondary malignancy were relatively low and correlated with pre-existing data on radiotherapy, suggesting wider implementation of helical tomotherapy in adjuvant radiotherapy for breast cancer patients.
- Breast cancer
- radiotherapy
- helical IMRT
- tomotherapy
- lymph node negative
- secondary malignoma
- lymphedema
- long-term results
Breast cancer is the most common cancer type affecting women (1). Breast-conserving surgery and adjuvant radiotherapy are essential for the curative treatment of early-stage lymph node negative breast cancer. Screening enables the early detection of breast tumours, and breast-conserving surgery combined with adjuvant radiotherapy (RT) lead to higher cure rates. In this context, additional radiotherapy of the whole breast significantly increases the local control (LC) and overall survival (OS) rates (2, 3).
In particular, even women with small, low-risk breast tumours benefit from adjuvant radiotherapy following breast-conserving surgery. The significant and positive impact on local tumour control has been reported in several randomised studies (4-7). Even in breast cancer patients with an extremely favourable prognosis, failure to undergo adjuvant radiotherapy can significantly lead to local recurrence at a later point in time (5). Previous population-based data analyses showed that additional, adjuvant radiotherapy significantly reduces the breast-cancer mortality rates among patients with advanced age (8).
In addition to whole breast irradiation, a radiation boost to the tumour bed can significantly improve the LC rates. Additional boost irradiation was previously applied in all patients until the age of 70 (based on old guidelines). According to current guidelines, boost irradiation should only be applied in patients with pre-menopausal status, poorly differentiated G3 tumours, T2 tumours, human epidermal growth factor receptor (HER2/neu) positivity, or narrow resection margins (9, 10).
Three-dimensional conformal radiation therapy (3D-CRT) has been and is continuously used as the standard whole breast radiation therapy. Intensity-modulated radiotherapy (IMRT) is an advanced type of radiation therapy. Previous literature frequently reported on step-and-shoot IMRT and volumetric arc therapy (VMAT) (11-13).
IMRT is an alternative radiation technique that is especially useful for patients with complex planning target volumes (PTV) or difficult anatomical situations, such as unfavourable positioning of the heart or parts of the lungs, if the chest wall has a complex shape, e.g., a funnel chest. Within the field of photon-IMRT, tomotherapy, also known as helical IMRT, is a new advancement. Tomotherapy obtains the steepest dose gradient (conformity index near to 1), has excellent dose homogeneity within the target volume, and has the lowest dose maxima values compared with other IMRT and rotational techniques (14, 15).
The technical characteristics of tomotherapy have been discussed in previous studies (16-19). A tomotherapy unit is a hybrid imaging tool comprising a 6-MV linear accelerator and a helical computed tomography (CT) scanner. Treatment is administered using a rotating fan beam; as the patient is moved through the gantry bore, the treatment beam forms a helix (16, 17). The beam is modulated by an extremely fast-moving, pneumatically driven, binary multileaf collimator (MLC). In an inverse treatment planning process, MLC conformation is optimised in order to deliver highly conformal radiation doses to the target tumour (18). TomoEDGE is a recently introduced tomotherapy technique that minimises dose penumbra at cranial and caudal field borders by modulating the primary collimators. This shortens the treatment duration by a factor of two without compromising the plan quality (19). The use of high fraction doses may be related to the potential increase in the risk of late-onset side effects. However, recent data on hypofractionated radiotherapy for breast radiation did not show an increase in the incidence of side effects (20-22).
A recent planning study analysed several radiotherapy strategies that used tomotherapy to investigate different fractionation schemes (normofractionated and hypofractionated) and boost application methods (sequential and simultaneous integrated) in adjuvant radiotherapy following breast-conserving surgery (23). The dosimetric results did not provide evidence to support that a simultaneous integrated boost or hypofractionation lead to disadvantages in tumour control rates or late-onset side effects when using tomotherapy (23).
This retrospective single-centre clinical study is the first to examine the long-term results of tomotherapy in patients with locally limited and lymph node-negative breast cancer following breast-conserving surgery in a larger cohort. The OS, LC, metastasis-free survival (MFS), early and late side effects, and rates of secondary cancer occurrence were analysed.
Patients and Methods
Patients. This retrospective single-centre clinical study included all patients (n=219) with locally limited, nodal-negative breast cancer who required adjuvant tomotherapy (helical IMRT) between 2011 and 2019 at the Clinic and Practice of Radiotherapy in Konstanz (Germany). All patients were women, underwent breast-conserving surgery and were indicated for adjuvant RT. All patients showed tumour-free lymph nodes on sentinel lymph node biopsy. Tomotherapy was indicated when conventional, tangential 3D-RT was insufficient to cover the PTV or when the radiation doses delivered to the OARs were not within the tolerable range. Patients with synchronous bilateral breast cancer, recurrent cancer, or history of radiotherapy in the thorax area were excluded. Patients were staged using the TNM classification system (American Joint Committee on Cancer, 7th Edition) (24).
The study was conducted in accordance with the World Medical Association’s Declaration of Helsinki and the International Committee of Medical Journal Editors Recommendations for the Protection of Research Participants and approved by the ethics committee of the Landesärztekammer (state medical association) Baden-Württemberg, Stuttgart, Germany (AZ: F-2021-082). All patients provided written informed consent to undergo the proposed treatment investigated in the study.
Imaging and regions of interest. To plan the radiotherapy, the patients underwent an imaging examination using a CT scanner with a slice thickness of 5 mm. For optimal dorsal positioning, a breast tilting board (wing-step) was used, and the lower extremities were secured in place. The scans were performed in resting expiratory position. The right and left lungs, the entire heart, the left ventricle, and the right breast were delineated on the CT images as OAR (25).
Target volumes were defined according to the institutional standards. The PTV of the treated breast included the entire mammary gland and chest wall behind it with safe lateral, cranial, and caudal margins of 2 cm and a safe medial margin of 1 cm. When additional boost radiation was administered, the PTV of the boost included the tumour bed with a safe margin of 8 mm in all directions.
Radiotherapy. All patients received radiation therapy delivered using the TomoTherapy® system (Accuray, Sunnyvale, CA, USA). This linear accelerator is a helical IMRT system with a 6-MV photon beam and integrated planning software for inverse planning. A beam field width of 2.5 cm or 5 cm was applied to all treatment plans, and the calculations were performed using a fine dose grid. The set pitch for each plan was chosen according to the previous report (26), and a modulation factor between 2.4 and 3 was applied. Each radiation plan was optimised with the aim of reducing the dose in all OARs (especially the left lung, heart, and contralateral breast), while covering the PTV of the treated breast and boost volume with at least 95% of the prescribed dose (Figure 1). Delivery of a maximum dose of >107% was avoided. Radiation doses were delivered to the entire breast, either normofractionated (28×1.8 Gy) or hypofractionated (16×2.65 Gy) with a cumulative dose of 50.4 Gy or 42.4 Gy, respectively (Table I). Where additional boost radiation was indicated, it was administered sequentially (8×2 Gy) or using simultaneous integrated boost technique (28×2.3 Gy).
An example of the dose distribution in adjuvant radiotherapy (whole breast with integrated boost of the tumour bed; 50.4/64.4Gy in 28 fractions) of a female patient with right-sided lymph node negative early breast cancer after breast-conserving surgery using helical tomotherapy is shown. In the computer-tomography slice, the planning target volume (PTV) of the whole left breast is marked with red outlines and of the boost volume/tumour bed is marked with violet outlines. The relative isodoses of the described median PTV dose (50.4 Gy) are shown.
Characteristics of the 219 participants in the study.
Acute and late toxicities. Acute and late toxicities were scored according to the Common Terminology Criteria for Adverse Events version 5 published by the Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer (27). Severe radiation-related toxicity was defined as >grade 3 late toxicity. Late toxicities without total loss of function but with severe impact on patient’s quality of life were also considered as severe radiation-induced late toxicity. None of the patients developed grade 4 or 5 toxicities. Changes were determined and documented during patients’ follow-up visits through a clinical interview conducted 6 weeks after radiotherapy and once a year thereafter. The follow-up examinations included mammography and breast ultrasound.
Statistical analysis. The endpoints used in this retrospective analysis were LC, distant MFS, disease-free survival (DFS), tumour-specific survival (TSS), and OS. LC after irradiation was defined as absence of infield tumour progression or recurrence. All time-to-event data were calculated using the Kaplan-Meier method from the first day of radiotherapy until the last follow-up or death. The differences of the Kaplan-Meier curves for subgroups were analysed using log-rank tests (e.g., T1 vs. T2), while absolute values were compared with Fisher’s exact test. In both cases, differences with a p-value <0.05 were considered statistically significant. All statistical analyses and plots were performed with “RStudio” (V2022.07.01 Build 554) using the “survival”- (V3.3-1) and “survminer”- (V0.4.9) package as well as further sub-packages.
Results
The mean age of all 219 female patients with early lymph node negative breast cancer who underwent breast-conserving surgery was 62.8 years (SD=11.5, range=32-90) at the time of adjuvant helical IMRT initiation. The mean follow-up time was 71.3 months (range=5-129).
A total of 190 patients were indicated for auxiliary boost irradiation. Table I provides an overview of the different boost application techniques and fractionation schemata used in tomotherapy. Additional chemotherapy was administered in 37% of the patients: neoadjuvant in 30%, adjuvant in 11%, and both neoadjuvant and adjuvant in 5%. Most of the patients received anthracycyline- and/or taxane- based chemotherapy regimens. Approximately 86% of the patients showed hormone receptor positivity and received additional adjuvant anti-hormonal therapy. In addition, 16% of patients exhibited human epidermal growth factor receptor 2 (HER2) overexpression and were treated with trastuzumab for 1year.
Outcomes. The 5- and 8-year LC rates of the whole cohort were 99.5% [95% confidence interval (CI)=98.5-100%] and 98.2% (95% CI=95.5%-100%). Only 3 of the 219 patients experienced local tumour recurrence (Figure 2). Regarding MFS, the 5- and 8-year rates were 97.4% (95%CI=95.1-99.7%) and 94.3% (95% CI=90.2-98.5%). Patients with T2 tumours showed a decreased MFS compared to patients with T1 tumours, but this difference was not considered significant (Figure 3). Further analysis of MFS among groups with different grades (grade 1-3), as well as among groups with different receptor expression profiles (hormone positive and HER2-negative, HER2-positive, and triple negative), showed no significant differences. Nevertheless, the HER2-positive group tended to have the highest values of MFS (Figure 3).
Kaplan-Meier curve for local control (LC) in all patients (n=219) (A), or according to grade (G1, G2, G3) (B), tumour stage (T1, T2) (C) and receptor expression [hormone-positive and human epidermal growth factor receptor 2 (HER2)-negative, HER2 positive (3+), and triple negative] (D).
Kaplan-Meier curve for metastasis free survival (MFS) in all patients (n=219) (A), or according to grade (G1, G2, G3) (B), tumour stage (T1, T2) (C) and receptor expression [hormone-positive and human epidermal growth factor receptor 2 (HER2)-negative, HER2-positive (3+), and triple negative] (D).
The 5- and 8-year OS rates were 97.7% (95% CI=95.7-99.7%) and 92.1% (95% CI=87.1-97.4%). Patients with T2 tumours also showed a decreased OS compared to patients with T1 tumours; however, this difference was not statistically significant. Further analysis showed that OS did not significantly differ among patients with different grades or receptor expression profiles. However, the HER2-positive group showed the highest OS values (Figure 4).
Kaplan-Meier curve for overall survival (OS) in all patients (n=219) (A), or according to grade (G1, G2, G3) (B), tumour stage (T1, T2) (C) and to receptor expression [hormone positive and human epidermal growth factor receptor 2 (HER2)-negative, HER2-positive (3+), and triple negative] (D).
The TSS was also analysed in the cohort. The 5- and 8-year TSS rates were 99.5% (95%CI=98.6-100%) and 95.9% (95%CI=91.9-100%), while no difference was found among groups with different grades or different receptor expression profiles (Figure 5).
Kaplan-Meier curve for tumour specific survival (TSS) in all patients (n=219) (A), or according to grade (G1, G2, G3) (B), tumour stage (T1, T2) (C) and to receptor expression [hormone positive and human epidermal growth factor receptor 2 (HER2) negative, HER2-positive (3+), and triple negative] (D).
The 5- and 8-year DFS rates were 95.6% (95% CI=92.7-98.5%) and 90.4% (95% CI=85.4-95.8%). Patients with T2 tumours showed a decreased DFS compared to patients with T1 tumours; however, this difference was not statistically significant. Further analysis of DFS and grading or receptor expression status showed no significant differences.
Acute toxicity. Of the 219 female patients treated with tomotherapy after breast-conserving surgery, 79% showed no or mild acute erythema (grade 0-2, Common Toxicity Criteria), while 21% showed grade 3 toxicity (epitheliolysis). None of the patients developed severe acute skin toxicity (grade 4-5).
A slight hyperpigmentation of the irradiated skin was observed in 43.8% of the patients, with more intense hyperpigmentation in 3.2%. In 1.8% of the treated patients, acute infection of the mammary gland occurred during the course of radiotherapy or after 6 weeks.
Changes in the hemogram during radiotherapy rarely occurred. Leucopoenia was reported in 8.2% (grade 1) and 0.9% (grade 2) of the patients. All of these patients received neoadjuvant or adjuvant chemotherapy prior to radiotherapy. Approximately 29.2% of the patients experienced fatigue during the course of radiation therapy.
Four patients developed signs of subacute pneumonitis after radiotherapy, but their clinical symptoms eventually resolved after several weeks (Table II).
Side effects (acute and late) experienced by the 219 participants in the study.
Late toxicity. A total of 39 patients showed a lymphedema of the ipsilateral arm or/and the irradiated breast. In particular, lymphedema of the ipsilateral arm occurred in 5.9% (grade 1) and 0.5% (grade 2) of the patients. Lymphedema of the treated breast was observed in 11% (grade 1) and 0.5% (grade 2) of the patients. Notably, 51.3% of these 39 patients received chemotherapy before or after surgery, whereas only 36.5% of all patients received chemotherapy. Fisher’s exact test showed a significant increase in lymphedema in patients who have received chemotherapy compared to those without chemotherapy (25.0 % vs. 13.7%, p<0.05).
Fibrosis of the treated mammary gland was noted in 5.5%, fat necrosis in 2.3%, and mastalgia in 6.4% of the irradiated patients. Cardiac toxicities, or damage to the brachial plexus were not reported in the cohort. Table II presents the radiation-related late-onset toxicities.
Second primary malignomas were rarely detected after adjuvant radiotherapy of the breast using tomotherapy (Figure 6). Only four patients (1.8%) developed secondary malignomas such as lymphoma, anal carcinoma, or rectum carcinoma.
Kaplan-Meier curve for secondary malignoma free survival (SMFS) regarding all patients (n=219).
Discussion
Adjuvant radiotherapy of lymph node negative early-stage breast cancer using tomotherapy following breast-conserving surgery provided favourable long-term oncological effects in our cohort. To our knowledge, this cohort of 219 patients is the largest sample used in a study of this nature. Smaller cohorts of 35, 71, and 93 patients have already been described by Zolcsak et al., Joseph et al., and Lee et al. (28-30).
The LC and TSS rates of over 99% after 5 years and over 95.9% after 8 years indicate favourable results. The OS rates of 97.7% after 5 years and 92.1% after 8 years were achieved at an average age of 63 years. These rates are approximately equivalent to those of the general population of the same age. Triple negative tumours are normally correlated with worse prognosis in breast cancer disease (31). Interestingly the triple-negative subgroup in this collective of early-stage tumours showed equal good results to the whole cohort. These findings can be seen as a strong argument for breast cancer screening programs for detecting aggressive tumours as early as possible.
In the study by Joseph et al., 2 of the 71 patients treated with tomotherapy developed local recurrence, with a 5-year OS rate of 97.4% (29). A comparable cohort analysed by Lee et al. (n=35) showed a loco-regional DFS rate of 95.1% with an OS of 95.1% after 5 years (30).
The MFS rate was significantly high in this cohort (T1/T2 N0), with a 5-year rate of 97.4% and an 8-year rate of 94.3%. This can be explained by the low probability of metastasis in early-stage carcinomas as well as the low probability of secondary metastasis due to the prevention of local recurrence. The equivalent cohorts in the studies conducted by Zolcsak et al. in 2022, K. Joseph et al. in 2021, and H. Lee et al. in 2020 also achieved high rates of MFS after 5 years (≥94%) (28-30).
Compared with other IMRT techniques, tomotherapy achieves the highest dose homogeneity and dose coverage in the planning target volume (PTV) of the breast and the boost volume. It also effectively facilitates prevention of dose minima in <95% of the prescribed dose and dose maxima in >107% of the prescribed dose within the PTV (according to the International Commission on Radiation Units and Measurements criteria) (23, 32, 33). Obtaining the described dose range (95-107%) is an important precondition for preventing local tumour recurrence while minimising the risk of side effects. A previous comparative study showed significantly better long-term results using tomotherapy compared to standard IMRT techniques following adjuvant radiotherapy in breast cancer patients who underwent breast-conserving surgery (30).
Of the 219 patients, 190 received additional boost radiation. This is likely contributed to the exceptionally high LC rates after 5 and 8 years (99.5% and 98.2%, respectively). The literature shows that patients across all age groups with even small breast tumours benefit from additional boost radiation and this additional treatment significantly lowers the local recurrence rate (34). However, the updated guidelines, especially in Germany, only recommend boost radiation in patients with T2 or T1 tumours with G3 grading, HER2 positivity, or premenopausal status, now. Hence, future studies are warranted to determine the impact of missing boost radiation on the long-term incidence of recurrence for small tumours with no risk factors. In this context, we refer to a recently published study conducted by Chua et al. This phase 3 study was conducted in patients treated for ductal carcinoma in situ (DCIS) and showed that, alongside surgery and adjuvant radiotherapy of the breast, additional boost radiation significantly improved the LC and DFS rates (35).
The data from smaller patient cohorts with early-stage breast cancer who were treated with tomotherapy (helical IMRT) and other IMRT techniques were compared; results demonstrated that the tomotherapy group showed better results, although the differences were not considered significant due to the relatively small sample size. In the study by Lee et al., the tomotherapy group (n=35) had an OS rate of 95.1% at 7 years, which was superior to that of the forward IMRT group (n=175) (92.6%). The distant MFS rate at 7 years was 100%, markedly better than that of the forward IMRT group. The tumour-specific survival rate at 7 years was also higher (97.6%) compared with that of the forward IMRT group (94.3%) (30).
The study by Joseph et al. investigated patient groups in the same situation; the tomotherapy group (n=71) achieved a 5-year OS of 97.4%, while the field-in-field IMRT group (n=73) achieved a 5-year OS of 96% (29).
Toxicity. Previous comparative studies were conducted on IMRT (IMRT techniques grouped together), which showed that IMRT has several advantages compared to the traditional 3D or 2D techniques. Patients treated with IMRT showed lower rates of late-onset fibrosis (36) and telangiectasia (37) compared to those treated with conventional radiation-technique. The lungs and heart were also more effectively protected by IMRT (38).
To date, only the data of individual, small cohorts with acute toxicity following adjuvant radiotherapy of the breast using tomotherapy are available. Taken together, these data can confirm the extremely low incidence of acute side effects such as higher-grade erythema, breast infections, and mastalgia (29). Only one study reported a radiogenic hyperpigmentation rate of 60%; however, the field-in-field IMRT comparison group reported a radiogenic hyperpigmentation rate of 78% (29). The cohort of the current study showed mild hyperpigmentation in 44% of the patients. Pronounced hyperpigmentation occurred in 3%. Hyperpigmentation is harmless but represents a cosmetic issue. Generally, hyperpigmentation is mild and eventually lightens after a few months.
Fatigue symptoms appeared in 29% of our cohort, and this finding is comparable to the data provided by Van Parijs et al., in which 25% of the patients were affected (39).
Hemogram changes rarely occurred in this patient cohort. Approximately 9% of patients developed grade 1-2 leukopenia during the course of radiotherapy, whereupon most of these patients received neoadjuvant or adjuvant chemotherapy before radiotherapy. None of the patients developed anaemia or thrombocytopenia during therapy. The severity of hemogram changes is based on the volume irradiated, and the volume of the breast is relatively small compared to the overall volume of the body (40).
Radiation-induced pneumonitis occurred in 1.8% of the patients in this cohort; it was diagnosed via a CT examination and successfully treated with cortisone administered for several weeks. This pneumonitis incidence is very low and comparable to the results attained by Arsene-Henry et al., who reported no relevant lung damage after a follow-up of 38 months (41).
Lymphedema of the irradiated breast occurred in 11.4% and of the ipsilateral arm in 6.4% of all patients. However, it was generally mild. In women, who received chemotherapy prior to irradiation, the incidence of lymphedema occurring in the ipsilateral arm and/or in the irradiated breast was significantly increased in this cohort. In the literature, the incidence of lymphedema diagnosed through a sentinel node biopsy and following adjuvant radiotherapy was approximately 11% (42).
In this cohort, fibrosis and fat necrosis of the irradiated mammary gland occurred in 5.5% and 2.3% of patients, respectively. The study conducted by Joseph et al. reported a fibrosis incidence of 13.8% among the patients treated with helical tomotherapy (29).
Previously, normofractionated radiotherapy was the standard curative therapy for breast cancer. To date, large, randomised studies conducted in >7,000 patients showed equally high tumour control and low late-onset toxicity rates when moderate hypofractionation was used as treatment for breast cancer. This can markedly shorten the overall duration of treatment (43-45).
This cohort included patients who received normofractionated (cumulative dose: 50.4 Gy; single dose: 1.8 Gy) and hypofractionated (cumulative dose: 42.4 Gy; single dose: 2.65 Gy) radiation. No significant differences were observed in the therapeutic outcome or toxicity rates. Across this whole group, four secondary malignomas (1.8%) were detected within the observation window. The literature reported the occurrence of secondary malignomas in only 1%-2% of patients following radiotherapy; however, more recent data showed that only <10% of the secondary malignomas were caused by radiotherapy (46, 47). The rates of radiotherapy of the breast for secondary malignomas were also described. In a cohort of 375,000 patients, the proportion of patients who developed secondary malignancies was significantly higher than the proportion of patients with breast cancer who did not receive radiation therapy (1.33% vs. 1.2%) after a median follow-up of 8.9 years. Approximately 3.4% of cases of secondary malignancies were attributable to radiation therapy. The increased risk of secondary malignancies in breast cancer patients treated with radiation therapy compared with those without radiation therapy was significant regardless of age at breast cancer diagnosis (48). In a French collective research of 17,745 women with breast cancer with a median follow-up of 13.4 years, the 15-year cumulative incidence of second malignancies was 1.807 per 100,000 individuals (49). In both studies, women were irradiated using 3D conformal techniques. Meanwhile, treatment plan studies estimated a higher radiation-induced cancer risk due to breast radiation therapy using multi-beam-IMRT or VMAT compared with 3D-CRT (50, 51). Clinical data about secondary cancer rates after IMRT of the breast are rare. With regard to the effect of helical tomotherapy, only the study by Zolcsak et al. was published (T1/2 N0, n=93) and showed a secondary cancer rate of 3% (28). In the present study, in a cohort of 219 patients who underwent helical tomotherapy, a secondary cancer rate of 1.8% was reported. This result indicates that adjuvant radiotherapy via helical tomotherapy induces a radiation-induced cancer risk that is similar to that of other irradiation methods like the 3D-conformale technique.
Conclusion
Tomotherapy of lymph node negative early-stage breast cancer after breast-conserving surgery showed excellent long-term tumour control, survival, and toxicity rates. Additional chemotherapy prior to irradiation significantly increased the risk of lymphedema. The secondary cancer rate was low and analogous to those of other radiation techniques. The results of this study indicate that a wider implementation of helical tomotherapy in adjuvant radiotherapy can contribute benefit to breast cancer patients.
Footnotes
Authors’ Contributions
F.Z., M.S. and R.K. initiated and supervised the project. F.Z., R.K., L.R. and M.S. collected the data. M.S., F.Z. and S.H. performed the data analysis. M.S., F.Z., H.H, P.H., J.D. and S.H. interpreted the experimental data and were responsible for creating figures. F.Z. and M.S. wrote the manuscript with input from all Authors. All Authors have been involved in manuscript revisions.
Conflicts of Interest
The Authors declare that there are no conflicts of interest in relation to this study.
- Received January 25, 2023.
- Revision received March 23, 2023.
- Accepted March 27, 2023.
- Copyright © 2023 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.
