Impact of tumour bed boost integration on acute and late toxicity in patients with breast cancer: A systematic review

The clinical outcome of postoperative radiotherapy using hybrid planning technique in left breast cancer after breast-conserving surgery

BACKGROUND

The purpose of this study is to observe the preliminary clinical outcome and acute toxicity of hybrid intensity modulated radiotherapy and volumetric modulated arc therapy planning technique with simultaneous integrated boost (SIB).

METHODS

From November 2015 to December 2018, 149 female patients with left-side breast cancer who underwent adjuvant radiotherapy with hybrid IMRT and VMAT planning technique with SIB were reviewed retrospectively. The primary endpoint was acute toxicities and the secondary endpoints were local recurrence-free survival (LRFS), distant metastasis-freesurvival (DMFS), disease-free survival (DFS), and overall survival (OS).

RESULTS

The median age was 52 years old and median follow-up was 43.4 months. Eighty-six percent of patients had acute grade 0 to grade1 dermatitis and 14% had grade 2 dermatitis. No acute radiation pneumonitis, esophagitis, or cardiovascular events were recorded during follow-up. The 3-year LRFS, DMFS, DFS, and OS rates were 95.1%, 95.1%, 90.3%, and 97.9%, respectively. The subgroup analysis revealed that patients with lymphovascular invasion had more local recurrence rate and worse DFS rate. Patients with advanced N stage had the trend of worse DMFS.

CONCLUSION

In conclusion, the hybrid IMRT and VMAT technique is feasible, safe and has less acute radiation related toxicities in SIB postoperative radiotherapy for left-sided breast cancer.

CANTO-RT: Skin toxicities evaluation of a multicenter large prospective cohort of irradiated patients for early-stage breast cancer

Skin damage is the most common and most important toxicity during and after radiotherapy. Its assessment and understanding of the factors influencing its occurrence, is a major issue in the management of patients irradiated for an early breast cancer CANTO is a prospective clinical cohort study of 10 150 patients with stage I-III BC treated from 2012-2017 in 26 cancer centers. In this study, we used CANTO-RT, a sub-cohort of CANTO, including 3480 patients who received RT. We are focus on specifical skin toxicities: Erythema, fibrosis, telangiectasia, and cutaneous pigmentation The prevalence of toxicities of interest varied over time, so at M3-6, 41.1% of patients had erythema while 24.8% of patients had fibrosis. At M12 and M36, the prevalence of erythema decreased respectively while fibrosis remains stable. The prevalence of telangiectasia increases from 1% to 7.1% from M3-6 to M36. After adjustments, we showed an association between the occurrence of skin erythema and obesity; the type of surgery; the presence of axillary dissection; the use of taxane-based CT and the 3DvsIMRT irradiation technique. Regarding fibrosis, an association is found, at M3-6, with age at diagnosis, obesity, tobacco, and the use of boost. Only obesity and the type of surgery received by the patient remained statistically significant at M12 and M36. In this study we identified several risk factors for acute and late skin. The use of a boost was mainly related to the occurrence of fibrosis while the use of IMRT-type technique decreased the occurrence of skin erythema.

Factors Associated with Late Local Radiation Toxicity after Post-Operative Breast Irradiation

Purpose. To assess determinants associated with late local radiation toxicity in patients treated for breast cancer. Methods. A systematic review was performed. All studies reporting ≥2 variables associated with late local radiation toxicity after treatment with postoperative whole breast irradiation were included. Cohort studies, randomized controlled trials, and cross-sectional studies were eligible designs. Study characteristics and definitions of determinants and outcome measures were extracted. If possible, the measure of association was extracted. Results. Twenty-one studies were included in this review. Six out of seven studies focused on the association between radiotherapy (boost) dose or irradiated breast volume and late radiation toxicity found significant results. Tumor bed boost was associated with late radiation toxicity, fibrosis, and/or edema in six out of twelve studies. Lower age was associated with late breast toxicity in one study, while in another study, higher age was significantly associated with breast fibrosis. Also, no association between age and late radiation toxicity was found in eight out of twelve studies. Similar inconsistent results were found in the association between late radiation toxicity and other patient-related factors (i.e., breast size, diabetes mellitus) and surgical and systemic treatment-related factors (i.e., complications after surgery, chemotherapy, and time between surgery and radiotherapy). Conclusion. In modern 3D radiotherapy, radiotherapy (boost) dose and volume are—like in 2D radiotherapy—associated with late local radiation toxicity, such as breast fibrosis and edema. Treatment de-escalation, for example, partial breast irradiation in selected patients might be important to decrease late local toxicity without compromising locoregional control and survival.

Risk Factors Related to Acute Radiation Dermatitis in Breast Cancer Patients After Radiotherapy: A Systematic Review and Meta-Analysis

Background

Acute radiation dermatitis (ARD) is the most common acute response after adjuvant radiotherapy in breast cancer patients and negatively affects patients’ quality of life. Some studies have reported several risk factors that can predict breast cancer patients who are at a high risk of ARD. This study aimed to identify patient- and treatment-related risk factors associated with ARD.

Methods

PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, and WanFang literature databases were searched for studies exploring the risk factors in breast cancer patients. The pooled effect sizes, relative risks (RRs), and 95% CIs were calculated using the random-effects model. Potential heterogeneity and sensitivity analyses by study design, ARD evaluation scale, and regions were also performed.

Results

A total of 38 studies composed of 15,623 breast cancer patients were included in the analysis. Of the seven available patient-related risk factors, four factors were significantly associated with ARD: body mass index (BMI) ≥25 kg/m² (RR = 1.11, 95% CI = 1.06–1.16, I² = 57.1%), large breast volume (RR = 1.02, 95% CI = 1.01–1.03, I² = 93.2%), smoking habits (RR = 1.70, 95% CI = 1.24–2.34, I² = 50.7%), and diabetes (RR = 2.24, 95% CI = 1.53–3.27, I² = 0%). Of the seven treatment-related risk factors, we found that hypofractionated radiotherapy reduced the risk of ARD in patients with breast cancer compared with that in conventional fractionated radiotherapy (RR = 0.28, 95% CI = 0.19–0.43, I² = 84.5%). Sequential boost and bolus use was significantly associated with ARD (boost, RR = 1.91, 95% CI = 1.34–2.72, I² = 92.5%; bolus, RR = 1.94, 95% CI = 1.82–4.76, I² = 23.8%). However, chemotherapy regimen (RR = 1.17, 95% CI = 0.95–1.45, I² = 57.2%), hormone therapy (RR = 1.35, 95% CI = 0.94–1.93, I² = 77.1%), trastuzumab therapy (RR = 1.56, 95% CI = 0.18–1.76, I² = 91.9%), and nodal irradiation (RR = 1.57, 95% CI = 0.98–2.53, I² = 72.5%) were not correlated with ARD. Sensitivity analysis results showed that BMI was consistently associated with ARD, while smoking, breast volume, and boost administration were associated with ARD depending on study design, country of study, and toxicity evaluation scale used. Hypofractionation was consistently shown as protective. The differences between study design, toxicity evaluation scale, and regions might explain a little of the sources of heterogeneity.

Conclusion

The results of this systematic review and meta-analysis indicated that BMI ≥ 25 kg/m² was a significant predictor of ARD and that hypofractionation was consistently protective. Depending on country of study, study design, and toxicity scale used, breast volume, smoking habit, diabetes, and sequential boost and bolus use were also predictive of ARD.

Radiodermatitis and Fibrosis in the Context of Breast Radiation Therapy: A Critical Review

Simple Summary

Skin toxicity is the main complication during irradiation in the management of early-stage breast cancer. In some cases, it may cause treatment to stop. These toxicities may be acute (mainly radiodermatitis) and/or late (mainly fibrosis). Their understandings, their mechanisms of occurrence, as well as their management is indispensable in order to improve the management of these patients. Through this study we propose to provide a clear picture of these toxicities in relation to the modalities of radiotherapy, advances in their quantification, and management to help practitioners improve their knowledge and clinical practices on this topic.

Abstract

Background: Radiation therapy has been progressively improved in order to maintain a satisfactory tumour response, while reducing toxicity. We will review the incidence of radiodermatitis and fibrosis according to the various radiation and fractionation techniques. We will then focus on the various methods used to manage, prevent, and quantify this toxicity. Method: More than 1753 articles were identified using the various search terms. We selected 53 articles to answer the questions addressed in this study according to criteria set in advance. Result: The literature reports lower acute toxicity with IMRT compared to 3DCRT, but no significant differences in terms of late toxicities. Partial breast irradiation appears to be less effective in terms of local control with a higher rate of late toxicity. Intra operative radiation therapy appears to provide good results in terms of both local control and late toxicity. The hypofractionation has equivalent efficacy and safety to the normofractionated regimen, but with lower rates of radiodermatitis and fibrosis. The adddition of a boost, particularly a sequential boost, increases the risk of fibrosis and radiodermatitis during treatment. Conclusion: The development of IMRT has significantly reduced acute toxicity and has improved tolerability during treatment. Modified fractionation has reduced treatment time, as well as adverse effects.

LINCS gene expression signature analysis revealed bosutinib as a radiosensitizer of breast cancer cells by targeting eIF4G1

Radioresistance is the predominant cause for radiotherapy failure and disease progression, resulting in increased breast cancer‑associated mortality. Using gene expression signature analysis of the Library of Integrated Network‑Based Cellular Signatures (LINCS) and Gene Expression Omnibus (GEO), the aim of the present study was to systematically identify potential candidate radiosensitizers from known drugs. The similarity of integrated gene expression signatures between irradiated eukaryotic translation initiation factor 4 γ 1 (eIF4G1)‑silenced breast cancer cells and known drugs was measured using enrichment scores (ES). Drugs with positive ES were selected as potential radiosensitizers. The radiosensitizing effects of the candidate drugs were analyzed in breast cancer cell lines (MCF‑7, MX‑1 and MDA‑MB‑231) using CCK‑8 and colony formation assays following exposure to ionizing radiation. Cell apoptosis was measured using flow cytometry. The expression levels of eIF4G1 and DNA damage response (DDR) proteins were analyzed by western blotting. Bosutinib was identified as a promising radiosensitizer, as its administration markedly reduced the dosage required both for the drug and for ionizing radiation, which may be associated with fewer treatment‑associated adverse reactions. Moreover, combined treatment of ionizing radiation and bosutinib significantly increased cell killing in all three cell lines, compared with ionizing radiation or bosutinib alone. Among the three cell lines, MX‑1 cells were identified as the most sensitive to both ionizing radiation and bosutinib. Bosutinib markedly downregulated the expression of eIF4G1 in a dose‑dependent manner and also reduced the expression of DDR proteins (including ATM, XRCC4, ATRIP, and GADD45A). Moreover, eIF4G1 was identified as a key target of bosutinib that may regulate DNA damage induced by ionizing radiation. Thus, bosutinib may serve as a potential candidate radiosensitizer for breast cancer therapy.

Intensity Modulated Radiation Therapy (IMRT) With Simultaneously Integrated Boost Shortens Treatment Time and Is Noninferior to Conventional Radiation Therapy Followed by Sequential Boost in Adjuvant Breast Cancer Treatment: Results of a Large Randomized Phase III Trial (IMRT-MC2 Trial)

PURPOSE

In the modern era, improvements in radiation therapy techniques have paved the way for simultaneous integrated boost irradiation in adjuvant breast radiation therapy after breast conservation surgery. Nevertheless, randomized trials supporting the noninferiority of this treatment to historical standards of care approach are lacking.

METHODS

A prospective, multicenter, randomized phase 3 trial (NCT01322854) was performed to analyze noninferiority of conventional fractionated intensity modulated radiation therapy with simultaneous integrated boost (IMRT-SIB) to 3-D conformal radiation therapy with sequential boost (3-D-CRT-seqB) for breast cancer patients. Primary outcomes were local control (LC) rates at 2 and 5 years (noninferiority margin at hazard ratio [HR] of 3.5) as well as cosmetic results 6 weeks and 2 years after radiation therapy (evaluated via photo documentation calculating the relative breast retraction assessment [pBRA] score [noninferiority margin of 1.25]).

RESULTS

A total of 502 patients were randomly assigned from 2011 to 2015. After a median follow-up of 5.1 years, the 2-year LC for the IMRT-SIB arm was noninferior to the 3-D-CRT-seqB arm (99.6% vs 99.6%, respectively; HR, 0.602; 95% CI, 0.123-2.452; P = .487). In addition, noninferiority was also shown for cosmesis after IMRT-SIB and 3-D-CRT-seqB at both 6 weeks (median pBRA, 9.1% vs 9.1%) and 2 years (median pBRA, 10.4% vs 9.8%) after radiation therapy (95% CI, -0.317 to 0.107 %; P = .332). Cosmetic assessment according to the Harvard scale by both the patient and the treating physician as well as late-toxicity evaluation with the late effects normal tissues- subjective, objective, management, analytic criteria, a score for the evaluation of long-term adverse effects in normal tissue, revealed no significant differences between treatment arms. In addition, there was no difference in overall survival rates (99.6% vs 99.6%; HR, 3.281; 95% CI: -0.748 to 22.585; P = .148) for IMRT-SIB and 3-D-CRT-seqB, respectively.

CONCLUSIONS

To our knowledge, this is the first prospective trial reporting the noninferiority of IMRT-SIB versus 3-D-CRT-seqB with respect to cosmesis and LC at 2 years of follow-up. This treatment regimen considerably shortens adjuvant radiation therapy times without compromising clinical outcomes.

Intensity-Modulated Radiotherapy with Concomitant Boost After Breast Conserving Surgery: A Phase I-II Trial

Purpose

A concomitant boost (CB) in patients treated with postoperative radiotherapy after conservative surgery of invasive breast cancer (BC) has been suggested for treatment time reduction and therapy intensification. The aim of this analysis was to assess long-term tolerability of a CB in patients treated with postoperative intensity Modulated Accelerated RAdiotherapy (MARA).

Patients and Methods

In this phase I–II trial, 321 patients with intermediate-high risk BC (pT1-4 with at least one of the following characteristics: pre or perimenopausal status, pN2-3, positive or close margins) were enrolled. Patients were treated with forward-planned intensity modulated radiotherapy (IMRT) and CB. A total dose of 50 Gy (2 Gy/fraction) and 60 Gy (2.4 Gy/fraction) was prescribed to the whole breast and the tumor bed, respectively. The potential impact of hypertension, diabetes, smoking habit, alcohol consumption, chemotherapy, and hormone therapy on both skin and subcutaneous late toxicity-free survival (LTFS) was evaluated. Survival curves were calculated using the Kaplan–Meier method.

Results

Median follow-up was 52 months (range: 3–115). Regional node irradiation, adjuvant chemotherapy and hormonal therapy were prescribed to 29.3%, 65.4% and 81.0% of patients, respectively. Five-year G2 and G3 skin LTFS were 95.6% and 100.0%, respectively. Five-year G2 and G3 subcutaneous LTFS were 80.0% and 98.6%, respectively. Only diabetes showed a significant correlation with worse G3 subcutaneous LTFS (p: 0.024). Five-year loco-regional control, metastasis-free survival, disease-free survival, and overall survival were 98.0%, 91.8%, 89.7% and 96.3%, respectively.

Conclusion

IMRT combined with CB was associated with a low risk of > G2 late toxicities (0.0% and 1.4% for skin and subcutaneous tissue, respectively). The cumulative actuarial incidence of local recurrences was 2.0% despite the exclusion of low-risk patients. Our results suggest that CB is safe and effective in patients with intermediate-high risk BC.

Trial Registration

ClinicalTrials.gov: NCT03471741.

Five-year survival outcomes of intensity-modulated radiotherapy with simultaneous integrated boost (IMRT-SIB) using forward IMRT or Tomotherapy for breast cancer

Intensity-modulated radiotherapy with simultaneous integrated boost (IMRT-SIB) reduces overall treatment duration and results in less radiotherapy (RT)-induced dermatitis. However, the use of traditional sequential approach or IMRT-SIB is still under debate since there is not enough evidence of long-term clinical outcomes. The present study investigated 216 patients who underwent breast conserving surgery (BCS) between 2010 and 2013. The median age was 51 years (range, 21-81 years). All patients received IMRT-SIB, 50.4 Gy at 1.8 Gy per fraction to the whole breast and 60.2 Gy at 2.15 Gy per fraction to the tumor bed by integral boost. Among 216 patients, 175 patients received post-operative RT with forward IMRT and 41 patients had Tomotherapy. The median follow-up was 6.4 years. Forty patients (97.6%) in the Tomotherapy arm and 147 patients (84%) in the IMRT arm developed grade 0-1 skin toxicity (P = 0.021). For the entire cohort, the 5-year and 7-year overall survival (OS) rates were 94.4% and 93.1% respectively. The 7-year distant metastasis-free survival rates were 100% vs 89.1% in the Tomotherapy and IMRT arm respectively (P = 0.028). In conclusion, Tomotherapy improved acute skin toxicity compared with forward IMRT-SIB. Chronic skin complication was 1.9%. IMRT-SIB resulted in good long-term survival.

Adjuvant whole breast radiotherapy with simultaneous integrated boost to tumor bed with intensity modulated radiotherapy technique in elderly breast cancer patients

Background

Adjuvant whole breast radiotherapy is the standard of care for breast cancer patients after partial mastectomy. Intensity-modulated radiation therapy (IMRT) has been reported to reduce acute toxicities compared to conventional radiotherapy. IMRT with simultaneous integrated boost (SIB) technique can deliver higher doses to tumor bed and irradiate whole breast with a lower dose level to shorten overall treatment duration. This study presents the long-term results of adjuvant IMRT with SIB in elderly breast cancer patients who received partial mastectomy.

Methods

From January 2007 to January 2018, 93 elder breast cancer patients (≥65-year-old) who received IMRT with SIB technique after partial mastectomy were reviewed retrospectively. The axillary areas were managed with either sentinel lymph node biopsies or axillary lymph node dissection. The dose to whole breast was 50.4 Gy in 28 fractions in all patients and the dose to tumor bed was 61.6 to 66.4 Gy in 28 fractions. The primary end point is locoregional control. Secondary end points include: overall survival, breast cancer-specific survival, distant-metastases-free survival, disease-free survival, and acute and chronic toxicities.

Results

The median follow-up was 56.1 months. One patient had ipsilateral breast tumor recurrence, 3 patients had regional lymph node recurrence, and 9 patients had distant metastases. Death occurred in 5 patients, including 3 patients died of breast cancer progression. Five-year overall survival is 96.3% and 5-year locoregional recurrence-free survival is 96.4%. The 5-year breast cancer specific survival and 5-year distant metastases-free survival is 97.5% and 87.2%, respectively. Seven patients developed second primary cancer after RT. Eighty-one point seven percent patients had acute grade 1 dermatitis while 18.3% suffered from grade 2 dermatitis. The incidence of grade 1 pneumonitis and grade 1 stomatitis was 4.3% and 8.6%, respectively.

Conclusions

Adjuvant IMRT with SIB technique is a safe and effective treatment strategy for elderly breast cancer patients after partial mastectomy.

A Phase 2 Study of 2 Weeks of Adjuvant Whole Breast/Chest Wall and/or Regional Nodal Radiation Therapy for Patients With Breast Cancer

PURPOSE

To report the results in terms of feasibility and early toxicity of hypofractionated adjuvant whole breast/chest wall and/or regional nodal radiation therapy for patients with breast cancer.

METHODS AND MATERIALS

From June 2013 to October 2014, 50 patients with breast cancer after mastectomy or after breast conservation surgery (BCS) were prospectively included. The institutional ethics committee approved the study, which was registered with ClinicalTrials.gov (ClinicalTrials.gov identifier no. NCT02460744). Treatment planning was performed using a simulator with 2 tangential fields to the breast/chest wall and an incident field to the supraclavicular fossa. The radiation dose delivered was 34 Gy in 10 fractions within 2 weeks, followed by a boost of 10 Gy in 5 fractions within 1 week for patients who underwent BCS. Acute skin toxicities were recorded during and after treatment according to the Radiation Therapy Oncology Group acute radiation toxicity scoring criteria. The primary objective was to obtain estimates of the acute toxicity rates and cosmetic outcomes that could be used to design a subsequent phase III comparative study. Acute skin and late toxicities were recorded during and after treatment. Cosmetic outcomes were assessed before and after treatment and during the regular follow-up period. A cost/benefit analysis was also performed and compared with that for standard treatment of 35 Gy in 15 fractions within 3 weeks.

RESULTS

The median follow-up was 39 months (range 14-48). The mean age was 51 years (range 26-75). A left-sided tumor was present in 25 patients (50%). Total mastectomy with axillary clearance was performed in 40 (80%) and BCS in 10 (20%) patients. Acute grade 2 and 3 skin toxicity was seen in 16 (32%) and 1 (2%) patient, respectively. In the BCS patients, grade 2 skin and subcutaneous toxicity was seen in 2 (20%) and 1 (10%) patient, respectively. Grade 2 edema was seen in 1 patient (10%). The cosmesis was excellent or good in 8 (80%) and fair or poor in 2 (20%) patients. The cost/benefit analysis revealed significantly less financial burden on the patients with 2 weeks of treatment. Disease-free and overall survival at 3 years was 94% and 96%, respectively.

CONCLUSIONS

Hypofractionated radiation therapy within 2 weeks appears to be feasible for patients with breast cancer and was associated with acute and late skin toxicity profiles similar to those observed with 3 weeks of treatment. The financial burden on the patient and family could be reduced with 2 weeks of treatment. Long-term follow-up data and a prospective comparative study are needed to strengthen these results. Hypofractionation might help radiation centers worldwide to meet the increasing need for radiation for breast cancer, especially in developing countries where resources are limited and patients must travel long distances for treatment.

Short course hypofractionated whole breast irradiation after conservative surgery: a single institution phase II study

Background

To assess the oncologic outcomes of hypofractionated whole breast irradiation (Hypo-WBI).

Methods

Eligible patients had undergone breast conservative surgery for early breast cancer (pTis-2) and none/limited nodal involvement. Hypo-WBI consisted of 34 Gy in 10 daily fractions over 2 weeks to the whole breast three-dimensional conformal radiotherapy (3DCRT), followed by a single fraction of 8 Gy to the tumor bed after 1 week (electrons). Primary endpoint is freedom from ipsilateral breast tumor recurrence (IBTR). Minimum follow up for living & event-free patients is 3 yrs.; median follow up time of the whole analyzed patient population is 5.4 yrs. (range: 1.8–11.4 yrs).

Results

Two hundred fifty-one patients were accrued from 2004 to 2013. All patients underwent local excision of the primary tumor to negative margins. Four patients failed in the ipsilateral breast after a median time of 3.2 years (range: 1.7–5.7 yrs) for a 5-year IBTR-free survival of 98.7% (95%CI: 97.3%–100%). IBTR-free survival was significantly higher for patients with invasive cancer than for patients with intraductal carcinoma (p = 0.036). Within patients with invasive tumors, no clear trends or associations were detected between IBTR and age, grading, molecular subtype, pT or pN stage. At 5 years, the actuarial rates of GR2 fibrosis and GR2+ teleangectasia are 2.4% (95%CI: 0–6.5%) and 7.1% (95%CI: 0.4–13.7%), respectively. Cosmesis was scored as excellent/good by ≈95% of patients and ≈60% of clinicians.

Conclusions

Hypo-WBI in 3 weeks allows excellent oncologic outcomes for invasive breast cancer after conservative surgery. Patients with intraductal carcinoma should be treated with Hypo-WBI only within a controlled study.

Trial registration

IRE-IFO Ethical and Scientific Committee (cod. RS61/04).

Recent advances in radiation oncology

Radiotherapy (RT) is very much a technology-driven treatment modality in the management of cancer. RT techniques have changed significantly over the past few decades, thanks to improvements in engineering and computing. We aim to highlight the recent developments in radiation oncology, focusing on the technological and biological advances. We will present state-of-the-art treatment techniques, employing photon beams, such as intensity-modulated RT, volumetric-modulated arc therapy, stereotactic body RT and adaptive RT, which make possible a highly tailored dose distribution with maximum normal tissue sparing. We will analyse all the steps involved in the treatment: imaging, delineation of the tumour and organs at risk, treatment planning and finally image-guidance for accurate tumour localisation before and during treatment delivery. Particular attention will be given to the crucial role that imaging plays throughout the entire process. In the case of adaptive RT, the precise identification of target volumes as well as the monitoring of tumour response/modification during the course of treatment is mainly based on multimodality imaging that integrates morphological, functional and metabolic information. Moreover, real-time imaging of the tumour is essential in breathing adaptive techniques to compensate for tumour motion due to respiration. Brief reference will be made to the recent spread of particle beam therapy, in particular to the use of protons, but also to the yet limited experience of using heavy particles such as carbon ions. Finally, we will analyse the latest biological advances in tumour targeting. Indeed, the effectiveness of RT has been improved not only by technological developments but also through the integration of radiobiological knowledge to produce more efficient and personalised treatment strategies.

Advantages of a technique using two 50 degree arcs in simultaneous integrated boost radiotherapy for left-sidebreast cancer

This study evaluated radiotherapy techniques with 15 cases for simultaneous integrated boost to treat whole left breast and tumor bed following breast conserving surgery. Treatment plans were generated using three techniques: volumetric modulated arc therapy (VMAT) with a partial arc of 190° (1ARC), VMAT with two tangential mini-arcs of 50° each (2TARC) and intensity modulated radiation therapy with four fixed angle fields (4IMRT). Dosimetric parameters for the whole breast (Target), the boost tumor bed (Boost), and surrounding normal organs were compared. Chair Index (CHI) was introduced to evaluate the dose homogeneity in Target given the two levels of prescription dose. The dose coverage in Target was better in 1ARC and 2TARC than that in 4IMRT. The mean CHI in 1ARC (2.47) and 2TARC (2.62) were higher than that in 4IMRT (1.71, p < 0.05), and this indicated the dose homogeneity of Target was better in 1ARC and 2TARC than that in 4IMRT. The mean doses to right lung, and contralateral breast in 4IMRT were lower than those in 2TARC but the differences between them were small. 2TARC was better than 4IMRT with respect to the dose to ipsilateral lung and heart. Overall, 2TARC was optimal among three techniques.