Efficacy of tangential irradiation with volumetric modulated arc therapy on scalp angiosarcoma using medical linac

PurposeTo increase the superficial dose and reduce the brain dose for radiotherapy of scalp angiosarcoma, we propose a novel irradiation technique of tangential irradiation volumetric modulated arc therapy (TI-VMAT).MethodsTI-VMAT and the conventional VMAT treatment plans for thirteen scalp angiosarcoma patients were created with a prescribed dose of 70 Gy. Each treatment was normalized to cover 95% of the planning target volume (PTV) with its prescribed dose. To realize TI-VMAT, an avoidance structure (AS) function was applied. AS was defined as a contour subtracted PTV by a certain space from the brain contour. TI-VMAT treatment plans for six different spaces between PTV and AS were developed and compared with the conventional VMAT treatment plan with respect to the following dosimetric parameters: homogeneity index (HI) and conformity index (CI) of the PTV, mean brain dose, and brain volume irradiated with 20% (V_20% [cc]), 40% (V_40% [cc]), 60% (V_60% [cc]), 80% (V_80% [cc]), and 100% (V_100% [cc]) of the prescribed dose.ResultsHI and CI were comparable between TI-VMAT and the conventional VMAT, the mean brain dose for TI-VMAT with AS defined by a space of 2.0 cm and jaw tracking was 14.27 Gy, which was significantly lower than that for the conventional VMAT (21.20 Gy). In addition, dosimetric parameters such as V_20% [cc] were significantly suppressed compared to those for high doses.ConclusionOur proposed irradiation technique TI-VMAT shows the potential to reduce radiation doses in the brain with maintaining higher dose coverage on the PTV.     

Factors influencing the use of adaptive radiation therapy in vulvar carcinoma

AimWe aim to evaluate the variables affecting the frequency of adaptive radiotherapy (ART) in vulvar cancer.BackgroundART may be needed throughout a definitive RT course for vulvar carcinoma due to changes in patient’s anatomy and tumor response.Materials and methodsCharts of patients charts who had been treated with definitive concurrent chemo-radiotherapy for vulvar carcinoma, between January 2015 and December 2019 were inquired. Radiation therapy was delivered using intensity modulated radiotherapy (IMRT) with daily image-guided radiotherapy (IGRT). ART was defined as re-simulation and re-planning based on deformation in the irradiated volume by more than 1 cm. Univariate analysis was conducted to study the impact of patient’s demographics as well as tumor characteristics on the frequency of ART.Results22 patients were eligible for analysis. Median age at diagnosis was 55 years (range 43–82). Radiotherapy dose was 60−66 Gy over 30–35 fractions (fx). Median primary tumor volume was 30cc (9–140). Median Body Mass Index (BMI) was 32 (range 21–40). Thirteen out of 22 patients (59%) required ART, with median timing at 25 fx (19–31). On univariate analysis, larger primary tumor volume (> = 30cc) was associated significantly with increased frequency of ART (p value = 0.0005). There was no significant impact of ART on the frequency with respect to patient’s age, BMI, tumor stage, grade and location.ConclusionChanges in radiation target volume are common among vulvar carcinoma patients who are treated with definitive radiotherapy, especially large primary tumors. This review highlights the importance of ART for patients with vulvar carcinoma treated with definitive radiotherapy.     

Dosimetric accuracy of three dose calculation algorithms for radiation therapy of in situ non-small cell lung carcinoma

BackgroundStudy determines differences in calculated dose distributions for non-small cell lung carcinoma (NSC LC) patients. NSC LC cases were investigated, being the most common lung cancer treated by radiotherapy in our clinical practice.Materials and methodsA retrospective study of 15 NSCLC patient dose distributions originally calculated using standard superposition (SS) and recalculated using collapsed cone (CC ) and Monte Carlo (MC) based algorithm expressed as dose to medium in medium (MCD_m) and dose to water in medium (MCD_w,) was performed so that prescribed dose covers at least 99% of the gross target volume (GTV). Statistical analysis was performed for differences of conformity index (CI), heterogeneity index (HI), gradient index (GI), dose delivered to 2% of the volume (D_2%), mean dose (D_mean) and percentage of volumes covered by prescribed dose (V_70Gy). For organs at risk (OARs), D_mean and percentage of volume receiving 20 Gy and 5Gy (V_20Gy, V_5Gy) were analysed.ResultsStatistically significant difference for GTVs was observed between MCD_w and SS algorithm in mean dose only. For planning target volumes (PTVs), statistically significant differences were observed in prescribed dose coverage for CC, MCD_m and MCD_w. The differences in mean CI value for the CC algorithm and mean HI value for MCD_m and MCD_w were statistically significant. There is a statistically significant difference in the number of MUs for MCD_m and MCD_w compared to SS.ConclusionAll investigated algorithms succeed in managing the restrictive conditions of the clinical goals. This study shows the drawbacks of the CC algorithm compared to other algorithms used.     

胸部肿瘤患者放疗中肺功能指标的变化及放射性肺炎的影响因素分析

目的:研究胸部肿瘤患者放疗中肺功能指标的变化并分析放射性肺炎的影响因素。方法:将2018年3月至2019年3月于我院接受放疗的胸部肿瘤患者100例记为观察对象,按照是否发生放射性肺炎分为肺炎组28例与无肺炎组72例。分别比较两组的临床资料、放疗前后肺功能及放疗参数,并采用多因素Logistic回归分析放射性肺炎的影响因素。结果:放疗后两组第1秒用力呼气容积(FEV_1)、FEV_1/用力肺活量(FVC)、一氧化碳弥散量(DLCO)均高于放疗前,且肺炎组放疗前、后FEV_1、FEV_1/FVC、DLCO均低于无肺炎组(均P0.05)。两组年龄、肿瘤类型、化疗史、美国东部肿瘤合作组(ECOG)评分、放疗靶区比较差异有统计学意义(均P0.05)。肺炎组计划靶区(PTV)、受到一定剂量以上照射的肺体积占全肺总体积的百分数(V_(dose))、平均肺计量(MLD)、正常组织并发症概率(NTCP)、总射野数高于无肺炎组(均P0.05)。经多因素Logistic回归分析可得:胸部肿瘤放疗患者放射性肺炎的独立危险因素有肺癌、化疗史、ECOG评分为2分、放疗靶区以肺野为主、PTV、MLD、V_(dose)、NTCP、总射野数、FEV_1、FEV_1/FVC(均P0.05)。结论:放疗可有效改善胸部肿瘤患者的肺功能,其中肺癌、化疗史、ECOG评分为2分、放疗靶区以肺野为主以及PTV、MLD、V_(dose)、NTCP、总射野数、FEV_1、FEV_1/FVC是放射性肺炎的影响因素。     

Post-chemotherapy target volumes are safe as boost volume for intact breast radiotherapy in locally advanced breast cancer

PurposeThe purpose of our study is to evaluate the challenges in identification of postoperative complexes (POC), the utility of clips in delineation of clinical target volume for boost in LABC downstaged with neoadjuvant chemotherapy (NACT) and to correlate this with patterns of recurrence.Methods and materialsLABC patients who underwent NACT followed by BCS and radiotherapy (2007–2014) were the subject of our analysis. The data on visibility and characteristics of postoperative cavity (POC), concordance of its volume with clip volume on radiation planning scan were retrieved. A 1 cm margin beyond POC was delineated as a clinical target volume (CTV). Postoperative whole breast and supraclavicular radiotherapy (50 Gy/25fractions/5wk or 42.4 Gy/16#/3 wk) followed by boost (10−16 Gy/5-8#/1–1.5wk) were delivered. Patterns of recurrence were evaluated.ResultsOut of 60 patients, 28.3% patients had stage II disease and 71.7% had stage III disease. 25% patients achieved pathological CR (complete response). The median POC volume was 30 cc and the median clip volume was 40 cc. The concordance of POC volume with clip volume was seen in 80%. Clips served as a good surrogate for POC in 80% of patients. At a median follow-up of 65 months (IQ range 32–84 months), and a lost to follow-up rate of 11.6 %, 3.3% (n = 2) patients had local recurrence (LR) and 8.3% (n = 5) had regional recurrence (LRR) in the supraclavicular region.ConclusionsDelineation of post NACT excision cavity as POC for boost radiotherapy is safe. Clips serve as a good surrogate for CTV delineation in 75% patients.     

Normal lung tissue complication probability in MR-Linac and conventional radiotherapy

PurposeTo study normal lung tissue (NLT) complications in magnetic resonance (MR) image based linac and conventional radiotherapy (RT) techniques.Materials and MethodsThe Geant4 toolkit was used to simulate a 6 MV photon beam. A homogenous magnetic field of 1.5 Tesla (T) was applied in both perpendicular and parallel directions relative to the radiation beam.Analysis of the NLT complications was assessed according to the normal lung tissue complication probability (NTCP), the mean lung dose (MLD), and percentage of the lung volume receiving doses greater than 20 Gy (V₂₀), using a sample set of CT images generated from a commercially available 4D-XCAT digital phantom.ResultsThe results show that the MLD and V₂₀ were lower for MR-linac RT. The largest reduction of MLD and V₂₀ for MR-linac RT configurations were 5 Gy and 29.3%, respectively.ConclusionMR-linac RT may result in lower NLT complications when compared to conventional RT.     

Dosimetric predictors of acute bone marrow toxicity in carcinoma cervix — experience from a tertiary cancer centre in India

BackgroundThe objective of this study was To determine the dose volume parameters predicting acute haematological toxicity in carcinoma cervix patients undergoing concurrent chemoradiotherapy.Materials and methodsAll patients that presented to the hospital between Jan 2019 and Dec 2019 were prospectively analyzed. Patients diagnosed to have Carcinoma Cervix and planned for concurrent chemoradiation by volumetric modulated arc therapy (VMAT) were included for analysis. Patients were assessed at baseline and every week during treatment for acute haematological toxicities. Dose volume parameters from treatment plans were correlated with RTOG grade of haematological toxicities.ResultsA total of 34 patients diagnosed to have squamous cell carcinoma of cervix were treated by radical radiotherapy by VMAT technique and concurrent chemotherapy. The most common stage of presentation was stage IIB (61.7%). 29 patients (85.2%) completed five cycles of weekly cisplatin. Statistical analysis for sensitivity and specificity of dosimetric parameters was performed using receiver operating characteristic (ROC) curve. The probability of developing bone marrow toxicity was analyzed using T test. Mean dose to bone marrow exceeding 28.5 Gy was significantly associated with bone marrow toxicity (sensitivity — 82.4%, specificity — 70.6%). On analyzing dose volume parameters, volume of bone marrow receiving 20 Gy, 30 Gy and 40 Gy (V20, V30 and V40) more than 71.75%, and 49.75% and 22.85%, respectively, was significantly associated with bone marrow toxicity.ConclusionsOur study concludes that mean dose to bone marrow exceeding 28.5 Gy has high sensitivity and specificity for predicting bone marrow toxicity in patients receiving IMRT. Volume of bone marrow receiving 20 Gy, 30 Gy and 40 Gy significantly correlated with acute haematological toxicity.     

Proton re-irradiation of unresectable recurrent head and neck cancers

BackgroundThis study presents a retrospective analysis (efficacy and toxicity) of outcomes in patients with unresectable recurrence of previously irradiated head and neck (H&N) cancers treated with proton therapy. Locoregional recurrence is the main pattern of failure in the treatment of H&N cancers. Proton re-irradiation in patients with relapse after prior radiotherapy might be valid as promising as a challenging treatment option.Materials and methodsFrom November 2015 to January 2020, 30 patients with in-field recurrence of head and neck cancer, who were not suitable for surgery due to medical contraindications, tumor localization, or extent, received re-irradiation with intensity-modulated proton therapy (IMPT). Sites of retreatment included the aerodigestive tract (60%) and the base of skull (40%). The median total dose of prior radiotherapy was 55.0 Gy. The median time to the second course was 38 months. The median re-irradiated tumor volume was 158.1 cm³. Patients were treated with 2.0, 2.4, and 3.0 GyRBE per fraction, with a median equivalent dose (EQD₂) of 57.6 Gy (α/β = 10). Radiation-induced toxicity was recorded according to the RTOG/EORTC criteria.ResultsThe 1- and 2-year local control (LC), progression-free survival (PFS), and overall survival (OS) were 52.6/21.0, 21.9/10.9, and 73.4/8.4%, respectively, with a median follow-up time of 21 months. The median overall survival was 16 months. Acute grade 3 toxicity was observed in one patient (3.3%). There were five late severe side effects (16.6%), with one death associated with re-irradiation.ConclusionRe-irradiation with a proton beam can be considered a safe and efficient treatment even for a group of patients with unresectable recurrent H&N cancers.     

Effects of lung tissue characterization in radiotherapy of breast cancer under deep inspiration breath hold when using Monte Carlo dosimetry

PurposeTo investigate the sensitivity of Monte Carlo (MC) calculated lung dose distributions to lung tissue characterization in external beam radiotherapy of breast cancer under Deep Inspiration Breath Hold (DIBH).MethodsEGSnrc based MC software was employed. Mean lung densities for one hundred patients were analysed. CT number frequency and clinical dose distributions were calculated for 15 patients with mean lung density below 0.14 g/cm³. Lung volume with a pre-defined CT numbers was also considered. Lung tissue was characterized by applying different CT calibrations in the low-density region and air-lung tissue thresholds. Dose impact was estimated by Dose Volume Histogram (DVH) parameters.ResultsMean lung densities below 0.14 g/cm³ were found in 10% of the patients. CT numbers below −960 HU dominated the CT frequency distributions with a high rate of CT numbers at −990 HU. Mass density conversion approach influenced the DVH shape. V_4Gy and V_8Gy varied by 7% and 5% for the selected patients and by 9% and 3.5% for the pre-defined lung volume. V_16Gy and V_20Gy, were within 2.5%. Regions above 20 Gy were affected. Variations in air- lung tissue differentiation resulted in DVH parameters within 1%. Threshold at −990 HU was confirmed by the CT number frequency distributions.ConclusionsLung dose distributions were more sensitive to variations in the CT calibration curve below lung (inhale) density than to air-lung tissue differentiation. Low dose regions were mostly affected. The dosimetry effects were found to be potentially important to 10% of the patients treated under DIBH.     

Segmented photon beams technique for irradiation of postmastectomy patients

AimTo present the segmented photon beams technique (SPBT) for irradiation of postmastectomy patients.BackgroundIn majority of techniques for irradiation of posmastectomy patients, a few adjacent photon or electron beams were usually implemented in order to encompass different parts of the target. In the presented SPBT technique, the radiotherapy plan consists of 6 isocentric photon beams and the area CTV includes both the chest wall and the supraclavicular area. This makes it possible to provide a uniform dose to the CTV with no hot and cold points and enables the determination of doses for the entire volume of critical organs.Methods and materialThe treatment forward-IMRT plan comprises six isocentric 4 and 15 MV photon beams. Modulation of the dose distribution for each field was obtained by applying three segments on average. The total dose of 45 Gy was administered in 20 fractions. Dose distributions in target volume and organs at risk were evaluated for 70 randomly chosen patients.ResultsOn average, 94.8% of the CTV volume received doses within 95–107% of the prescribed dose. The average volume of the heart receiving a dose of 30 Gy and lager was 2% for patients with left breast cancer. The average dose to the lung on the irradiation side was always lower than 15.5 Gy and the average V20 Gy was below 35.5%.ConclusionsThe SPBT complies with requirements for high dose homogeneity within the target volume and satisfactory level of sparing of organs at risk.     

Intracranial chordoma: radiosurgery,hypofractionated stereotactic radiotherapy and treatment outcomes

BackgroundThe aim of the study was to assess the results of stereotactic radiosurgery and hypofractionated stereotactic radiotherapy (SRS/SRT) for skull base chordomas.Materials and methodsTwenty-three patients aged 12–75 were treated with SRS/SRT due to skull base chordoma. In 19 patients SRS/SRT was a part of the primary therapy, while in 4, a part of the treatment of recurrence. In 4 patients SRS/SRT was used as a boost after conventional radiotherapy and in 19 cases it was the only irradiation method applied. Patients were irradiated to total dose of 6–35 Gy and median total equivalent dose of 52 Gy.ResultsDuring median follow-up of 39 months, 4 patients died. One-, two- and five-year OS was 95%, 89% and 69%, respectively. In nine patients, progression of the disease was diagnosed during study period. One-, two- and five-year progression free survival (PFS) from the end of radiotherapy was 81%, 59% and 43%, respectively. Radiotherapy was well tolerated and only two patients in our group experienced moderate treatment-related toxicity.ConclusionSRS/SRT alone or in combination with surgery is a safe and effective method of irradiation of patients with skull base chordomas. High EQD₂ is necessary to achieve satisfactory treatment results.     

The impact of the time factor on the outcome of a combined treatment of patients with laryngeal cancer

PurposeTo investigate the impact of the time factor on the locoregional control in combined treatment (surgery and postoperative radiotherapy) in patients with advanced laryngeal cancer.Materials and MethodsBetween January 1993 and December 1996, 254 patients with pT3 or pT4 and pN0-pN2 laryngeal cancer were treated by surgery and postoperative radiotherapy (RT). The median age of patients was 56.3 years (range: 30–70 years). The analyzed group consisted of 236 males (92%) and 18 females (8%). In all cases total laryngectomy was performed. 196 out of 254 patients underwent homolateral neck dissection and 58 out of 254 bilateral neck dissection. RT began 45 days postoperatively (range: 22 to 78 days) and continued for 47 days (range: 40–74 days). The primary tumour bed was irradiated to the median total dose of 61.2 Gy (range: 57 – 64 Gy) and all regional lymph nodes were treated in all patients to a dose of 50 Gy. Postoperative RT was indicated in case of close postoperative margins at the tumour site or pathological status of lymph nodes described as pN1 or pN2. Univariate and multivariate analyses were used to determine the predictors for locoregional failure. The following factors were studied for their prognostic importance of locoregional outcome: the overall treatment time (OTT), radiotherapy treatment time (RTT), the interval between surgery and the beginning of radiotherapy, age, sex, pT and pN categories.Results: The actuarial 5-year overall survival rate was 49%, the actuarial loco regional control rate was 70%. The univariate analysis, using a log-rank test indicated that prolongation of the overall treatment time (OTT), the time of radiotherapy (RTT), the interval time between surgery and radiotherapy, and the pN status were predicted for the loco regional control of postoperative radiotherapy. The multivariate analysis using Cox proportional hazard model indicated that only RTT, OTT, and the pathological status of lymph nodes were independent prognostic factors for the loco regional control.Conclusions: The analysis showed that the prolongation of the overall treatment time of the combined modality (OTT) and the time of radiotherapy course (RTT) were independent prognostic time factors correlated with lower loco regional control.     

食管癌患者放射治疗中照射体积和时间与外周血淋巴细胞绝对值的相关性研究

摘要 目的：探究照射体积和时间与食管癌患者外周血淋巴细胞绝对值的相关性。方法：本研究方案将纳入2019年1月~2019年12月蚌埠医学院第一附属医院放疗科收治的放疗或同步放化疗食管癌患者84例,其中单独放疗患者24例,同步放化疗患者60例,采用血液细胞分析仪测定患者放疗期间每周复查外周血白细胞（WBC）、中性粒细胞（N）、淋巴细胞（L）、血红蛋白（HB）及血小板（PLT）计数等指标。Pearson相关性分析照射时间、剂量及体积与外周血指标之间的相关性。结果：食管癌放疗患者,包括同步放化疗及单纯放疗亚组,在治疗1-6周,照射时间与外周血指标均无相关性（P>0.05）。但在放疗第5-6周,患者放疗剂量与WBC、N、L、HB呈负相关（P<0.05）,同步放化疗亚组患者照射剂量与WBC、N、L、HB呈负相关（P<0.05）。在治疗1-4周,不同照射剂量下各梯度照射剂量对应照射体积与外周血指标均无相关性（P>0.05）。但在第5-6周时,患者不同梯度照射剂量下各照射体积与WBC、N呈负相关（P<0.05）,同时在20Gy-60Gy照射剂量,尤其20Gy和30Gy照射剂量下照射体积与L呈负相关（P<0.05）。同步放化疗亚组患者不同照射剂量下各照射体积与WBC、N呈负相关（P<0.05）,同时在20Gy-60Gy照射剂量下照射体积与L呈负相关（P<0.05）,而且在60Gy照射剂量下照射体积与HB呈负相关（P<0.05）。结论：放疗患者特别是同步放化疗亚组患者照射体积、照射剂量与食管癌患者外周血淋巴细胞计数成负相关,基线淋巴细胞与食管癌患者外周血淋巴细胞计数成正相关,而照射时间与食管癌患者外周血淋巴细胞计数无相关性。     

Comparison of dose distributions and organs at risk (OAR) doses in conventional tangential technique (CTT) and IMRT plans with different numbers of beam in left-sided breast cancer

Aim

Our aim was to improve dose distribution to the left breast and to determine the dose received by the ipsilateral lung, heart, contralateral lung and contralateral breast during primary left-sided breast irradiation by using intensity modulated radiotherapy (IMRT) techniques compared to conventional tangential techniques (CTT). At the same time, different beams of IMRT plans were compared to each other in respect to CI, HI and organs at risk (OAR) dose.

Background

Conventional early breast cancer treatment consists of lumpectomy followed by whole breast radiation therapy. CTT is a traditional method used for whole breast radiotherapy and includes standard wedged tangents (two opposed wedged tangential photon beams). The IMRT technique has been widely used for many treatment sites, allowing both improved sparing of normal tissues and more conformal dose distributions. IMRT is a new technique for whole breast radiotherapy. IMRT is used to improve conformity and homogeneity and used to reduce OAR doses.

Materials and methods

Thirty patients with left-sided breast carcinoma were treated between 2005 and 2008 using 6, 18 or mixed 6/18 MV photons for primary breast irradiation following breast conserving surgery (BCS). The clinical target volume [CTV] was contoured as a target volume and the contralateral breast, ipsilateral lung, contralateral lung and heart tissues as organs at risk (OAR). IMRT with seven beams (IMRT7), nine beams (IMRT9) and 11 beams (IMRT11) plans were developed and compared with CTT and among each other. The conformity index (CI), homogeneity index (HI), and doses to OAR were compared to each other.

Results

All of IMRT plans significantly improved CI (CTT: 0.76; IMRT7: 0.84; IMRT9: 0.84; IMRT11: 0.85), HI (CTT: 1.16; IMRT7: 1.12; IMRT9: 1.11; IMRT11: 1.11), volume of the ipsilateral lung receiving more than 20 Gy (>V_20 Gy) (CTT: 14.6; IMRT7: 9.08; IMRT9: 8.10; IMRT11: 8.60), and volume of the heart receiving more than 30 Gy (>V_30 Gy) (CTT: 6.7; IMRT7: 4.04; IMRT9: 2.80; IMRT11: 2.98) compared to CTT. All IMRT plans were found to significantly decrease >V_20 Gy and >V_30 Gy volumes compared to conformal plans. But IMRT plans increased the volume of OAR receiving low dose radiotherapy: volume of contralateral lung receiving 5 and 10 Gy (CTT: 0.0–0.0; IMRT7: 19.0–0.7; IMRT9: 17.2–0.66; IMRT11: 18.7–0.58, respectively) and volume of contralateral breast receiving 10 Gy (CTT: 0.03; IMRT7: 0.38; IMRT9: 0.60; IMRT11: 0.68). The differences among IMRT plans with increased number of beams were not statistically significant.

Conclusion

IMRT significantly improved conformity and homogeneity index for plans. Heart and lung volumes receiving high doses were decreased, but OAR receiving low doses was increased.