Arc Therapy Technique Research Articles

Predicting the effect of indirect cell kill in the treatment of multiple brain metastases via single-isocenter/multitarget volumetric modulated arc therapy stereotactic radiosurgery.

PurposeDue to spatial uncertainty, patient setup errors are of major concern for radiosurgery of multiple brain metastases (m‐bm) when using single‐isocenter/multitarget (SIMT) volumetric modulated arc therapy (VMAT) techniques. However, recent clinical outcome studies show high rates of tumor local control for SIMT‐VMAT. In addition to direct cell kill (DCK), another possible explanation includes the effects of indirect cell kill (ICK) via devascularization for a single dose of 15 Gy or more and by inducing a radiation immune intratumor response. This study quantifies the role of indirect cell death in dosimetric errors as a function of spatial patient setup uncertainty for stereotactic treatments of multiple lesions.Material and MethodsNine complex patients with 61 total tumors (2‐16 tumors/patient) were planned using SIMT‐VMAT with geometry similar to HyperArc with a 10MV‐FFF beam (2400 MU/min). Isocenter was placed at the geometric center of all tumors. Average gross tumor volume (GTV) and planning target volume (PTV) were 1.1 cc (0.02–11.5) and 1.9 cc (0.11–18.8) with an average distance to isocenter of 5.4 cm (2.2–8.9). The prescription was 20 Gy to each PTV. Plans were recalculated with induced clinically observable patient setup errors [±2 mm, ±2o] in all six directions. Boolean structures were generated to calculate the effect of DCK via 20 Gy isodose volume (IDV) and ICK via 15 Gy IDV minus the 20 Gy IDV. Contributions of each IDV to the PTV coverage were analyzed along with normal brain toxicity due to the patient setup uncertainty. Induced uncertainty and minimum dose covering the entire PTV were analyzed to determine the maximum tolerable patient setup errors to utilize the ICK effect for radiosurgery of m‐bm via SIMT‐VMAT.ResultsPatient setup errors of 1.3 mm /1.3° in all six directions must be maintained to achieve PTV coverage of the 15 Gy IDV for ICK. Setup errors of ±2 mm/2° showed clinically unacceptable loss of PTV coverage of 29.4 ± 14.6% even accounting the ICK effect. However, no clinically significant effect on normal brain dosimetry was observed.ConclusionsRadiosurgery of m‐bm using SIMT‐VMAT treatments have shown positive clinical outcomes even with small residual patient setup errors. These clinical outcomes, while largely due to DCK, may also potentially be due to the ICK. Potential mechanisms, such as devascularization and/or radiation‐induced intratumor immune enhancement, should be explored to provide a better understanding of the radiobiological response of stereotactic radiosurgery of m‐bm using a SIMT‐VMAT plan.

Dosimetric validation of two different radiobiological models for parotid gland functionality of tongue cancer

AbstractObjectiveThe aim of this study was to investigate the normal tissue complication probability (NTCP) for parotid gland of ca tongue patients from two different radiobiological models and to establish a dosimetric validity.MethodsLyman–Kutcher–Burman (LKB) model and linear quadratic (LQ) model were considered for determination of NTCP and tolerance dose (TD5/5 and TD50/5) for the parotid gland of 67 number of ca tongue patients who were treated with the volumetric arc therapy (VMAT) technique. An in‐house developed software on Excel (VBA) was used for this study.ResultsThe equivalent uniform dose (EUD) was linearly proportional to the effective volume (veff) for parotid glands and there was a strong correlation between EUD and veff. At EUD = 46 to 47 Gy, the NTCP of parotid was 0.5 for both the models. The tolerance doses, TD5/5 (veff) and TD50/5 (veff) were exponentially reduced with increase of veff for LKB model; whereas these parameters were volume‐independent in the LQ model. TD5/5 (veff) and TD50/5 (veff) were 31.98 Gy and 45.98 Gy respectively for all 67 patients in the LQ model. Below TD50/5, NTCP of LKB model was less than the NTCP , calculated from LQ model.ConclusionOne may consider radiobiological LQ model for estimation of clinical tolerance dose for OARs. Due to lack of clinical data, there are inaccuracy in determination of NTCP from LQ model. If sufficient number of tolerance data for partial volumes are available, the prediction of NTCP would be more confident.

Influence of target dose heterogeneity on dose sparing of normal tissue in peripheral lung tumor stereotactic body radiation therapy

ObjectiveTo evaluate the influence of target dose heterogeneity on normal tissue dose sparing for peripheral lung tumor stereotactic body radiation therapy (SBRT).MethodsBased on the volumetric-modulated arc therapy (VMAT) technique, three SBRT plans with homogeneous, moderate heterogeneous, and heterogeneous (HO, MHE, and HE) target doses were compared in 30 peripheral lung tumor patients. The prescription dose was 48 Gy in 4 fractions. Ten rings outside the PTV were created to limit normal tissue dosage and evaluate dose falloff.ResultsWhen MHE and HE plans were compared to HO plans, the conformity index of the PTV was increased by approximately 0.08. The median mean lung dose (MLD), V5, V10, V20 of whole lung, D2%, D1cc, D2cc of the rib, V30 of the rib, D2% and the maximum dose (Dmax) of the skin, and D2% and Dmax of most mediastinal organs at risk (OARs) and spinal cord were reduced by up to 4.51 Gy or 2.8%. Analogously, the median Dmax, D2% and mean dose of rings were reduced by 0.71 to 8.46 Gy; and the median R50% and D2cm were reduced by 2.1 to 2.3 and 7.4% to 8.0%, respectively. Between MHE and HE plans there was little to no difference in OARs dose and dose falloff beyond the target. Furthermore, the dose sparing of rib V30 and the mean dose of rings were negatively correlated with the rib and rings distance from tumor, respectively.ConclusionsFor peripheral lung tumor SBRT, target conformity, normal tissue dose, and dose falloff around the target could be improved by loosening or abandoning homogeneity. While there was negligible further dose benefit for the maximum target dose above 125% of the prescription, dose sparing of normal tissue derived from a heterogeneous target decreased as the distance from the tumor increased.

Impact of CBCT frequency on target coverage and dose to the organs at risk in adjuvant breast cancer radiotherapy

The current study aims to assess the effect of cone beam computed tomography (CBCT) frequency during adjuvant breast cancer radiotherapy with simultaneous integrated boost (SIB) on target volume coverage and dose to the organs at risk (OAR). 50 breast cancer patients receiving either non-hypofractionated or hypofractionated radiotherapy after lumpectomy including a SIB to the tumor bed were selected for this study. All patients were treated in volumetric modulated arc therapy (VMAT) technique and underwent daily CBCT imaging. In order to estimate the delivered dose during the treatment, the applied fraction doses were recalculated on daily CBCT scans and accumulated using deformable image registration. Based on a total of 2440 dose recalculations, dose coverage in the clinical target volumes (CTV) and OAR was compared depending on the CBCT frequency. The estimated delivered dose (V95%) for breast-CTV and SIB-CTV was significantly lower than the planned dose distribution, irrespective of the CBCT-frequency. Between daily CBCT and CBCT on alternate days, no significant dose differences were found regarding V95% for both, breast-CTV and SIB-CTV. Dose distribution in the OAR was similar for both imaging protocols. Weekly CBCT though led to a significant decrease in dose coverage compared to daily CBCT and a small but significant dose increase in most OAR. Daily CBCT imaging might not be necessary to ensure adequate dose coverage in the target volumes while efficiently sparing the OAR during adjuvant breast cancer radiotherapy with SIB.

Mediastinal and neck follicular dendritic cell sarcoma treated with definitive radiation therapy using the volumetric modulated arc therapy technique: a case report

AbstractFollicular dendritic cell sarcoma (FDCS) is a rare malignancy that affects the nodal and extranodal tissues. The mediastinum is a rare site for this tumor, with few published reports and series. Although surgery is the mainstay of treatment for this disease entity, in this report we present a case of mediastinal FDCS treated with definitive radiation therapy (RT) with a near‐total radiological response. A 28‐year‐old woman presented with chest tightness and neck swelling. Radiological findings were suggestive of a conglomerated nodal mass involving the mediastinum and extending superiorly into the anterior neck. Biopsy results led to a diagnosis of FDCS. The tumor was deemed unresectable, and definitive RT was planned as the treatment. The patient was treated with volumetric modulated arc therapy to a total dose of 54 Gy in 30 fractions over 6 weeks. Her symptoms had completely resolved at the first follow‐up visit, 3 months after RT completion, with a near‐total radiological response on a contrast‐enhanced computed tomography scan. Although surgery is the standard of care in FDCS, based on the favorable response of FDCS to RT, as in this case, the role of definitive RT needs to be studied in more patients to determine its efficacy in long‐term tumor control as an alternative to surgery.

Volumetric modulated arctherapy for locally advanced nasopharyngeal carcinoma: Clinical efficacy and late toxicity

PurposeWe report our experience of 86 consecutive patients with locally advanced nasopharyngeal carcinoma who were treated with volumetric modulated arc therapy. Materials and methodsWe retrospectively reviewed the medical records of 86 patients with histologically proven primary nasopharyngeal carcinoma treated with volumetric modulated arctherapy technique radiotherapy. Primary endpoints were local, regional, distant control, and overall survival, second endpoint was late toxicity. ResultsThe median age was 47.5 years (range: 13–79 years) with sex ratio 1.09. At diagnosis, rhinologic symptoms represented the most common clinical presentation, reported by 61 patients (70.9%). Almost 88.4% of patients presented non-keratinizing undifferentiated carcinoma histology (n=76). Most of the patients presented a locally advanced disease defined by stage III and IVa (95.3%). Therefore, 31 patients were treated by concurrent chemoradiation (36%), 52 patients received induction chemotherapy followed by concurrent chemoradiotherapy (57%), three patients received induction chemotherapy followed by exclusive radiotherapy (3.5%). and three patients treated with exclusive irradiation (3.5%). With a median follow up of 15.7 months (range: 4–33.3 months), nine patients died (10.4%), three presented local or locoregional relapse (3.4%), while nine patients presented distant recurrences (10.4%). The two years overall and disease-free survival rates were 88.7% and 83.1% respectively, locoregional control was 100% at 12 months and 96.2% at 24 months, and the two years distant failure-free survival was 86.7%. Time to relapse was the only prognostic factor in univariate analysis for overall survival in our study. The therapeutic tolerance was good with 61.7% of grade 3 and 2.3% grade 4 hyposialia respectively, 46.5% of otological disorders and no radionecrosis was noted. ConclusionVolumetric modulated arctherapy technique with concurrent chemoradiotherapy is an effective treatment for nasopharyngeal carcinoma with excellent overall and locoregional control without severe toxicity. Distant metastasis is the major site of failure, so induction chemotherapy added to chemoradiotherapy must be discussed in multidisciplinary consultation meeting because it significantly improved recurrence-free survival and overall survival, as compared with chemoradiotherapy alone.

Improving efficiency in the radiation management of multiple brain metastases using a knowledge-based planning solution for single-isocentre volumetric modulated arc therapy (VMAT) technique.

IntroductionThis study aimed to develop a single‐isocentre volumetric modulated arc therapy (si‐VMAT) technique for multiple brain metastases using knowledge‐based planning software, comparing it with a multiple‐isocentre stereotactic radiosurgery (mi‐SRS) planning approach.MethodsTwenty‐six si‐VMAT plans were created and uploaded into RapidPlanTM (RP) to create a si‐VMAT model. Ten patients, with 2 to 6 metastases (mets), were planned with a si‐VMAT technique utilising RP, and a mi‐SRS technique on Brainlab iPlan.Paddick Conformity Index (PCI) was used to compare conformity. The volumes of the brain receiving 15Gy, 12Gy, 10Gy, 7.5Gy and 3Gy were also compared.Retrospective treatment times from the last eight patients treated were averaged for pre‐imaging and beam on time to calculate treatment times for both techniques.ResultsThere was a significant difference in the PCI scores for the mi‐SRS plans (M = 0.667, SD = 0.114) and si‐VMAT plans (M = 0.728, SD = 0.088), with PCI values suggesting better prescription dose conformity with the si‐VMAT technique (P = 0.014). Percentage of total brain volume receiving low‐dose wash at four of the five different dose levels was significantly less (P < 0.05) with mi‐SRS.Average time to treat a single met with current mi‐SRS technique is 25.7 min, with each additional met requiring this same amount of time. The average time to treat 2–3 mets using si‐VMAT would be 25.3 min and 4+ metastases 33.5 min.ConclusionA knowledge‐based si‐VMAT approach was efficient in planning and treating multi metastases while achieving clinically acceptable dosimetry with respect to dose conformity and low‐dose fall off.

Evaluation of volumetric modulated arc therapy technique for cranio-spinal irradiation: A rando - phantom based dosimetric study

Evaluation of volumetric modulated arc therapy technique for cranio-spinal irradiation: A rando - phantom based dosimetric study

Evaluation of the correlation between dosimetric, geometric, and technical parameters of radiosurgery planning for multiple brain metastases

PurposeTo evaluate the correlation between dosimetric, geometric, and technical parameters for radiosurgery planning of multiple brain metastasis treatments treated with a linear accelerator with volumetric modulated arc therapy (VMAT) technique.Materials and methodsData were collected retrospectively from 55 patients who underwent radiosurgery in a single institution from August 2017 to February 2020. Patients presented 4–21 brain metastases were treated with a single fraction with doses between 18 and 20 Gy. Dosimetric variables were collected including V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, conformity index (CI), heterogeneity index (HI), maximum dose (Dmax), and the CI_R50. Geometric variables including the number of lesions, target volumes, the smallest target volume, the largest target volume, and the distance between the isocenter and the most distant lesion (DIL) and technical variables such as the numbers of total arcs, noncoplanar arcs, and isocenters were collected for analysis.ResultsThe number of lesions had a moderate positive correlation with V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, HI, Dmax, and with the number of total arcs. The target volumes had a positive medium–high correlation with V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, and moderate positive correlation with HI, Dmax, number of arcs and noncoplanar arcs. The CI and CI_R50 had a negative correlation with all volumes related to the target: the target volumes, the smallest, and the largest lesion. A positive correlation was observed between the distance of the isocenter and the most DIL with V5Gy, V8Gy, V10Gy, V12Gy, V14Gy, HI, Dmax, and the number of isocenters.ConclusionIt was found that the number of lesions and the target volumes are good predictors of dosimetric indexes of plan evaluation and that the distance between the isocenter and the most DIL harms them.

Evaluation of volumetric modulated arc therapy technique for cranio-spinal irradiation: A rando - phantom based dosimetric study

Evaluation of volumetric modulated arc therapy technique for cranio-spinal irradiation: A rando - phantom based dosimetric study

Dosimetric Comparison of Whole Breast Radiotherapy Using Field-in-Field and Volumetric Modulated Arc Therapy Techniques in Left-Sided Breast Cancer Patients.

IntroductionThe radiotherapy of left-sided breast cancers is challenging because of neighboring critical organs, posing an increased risk of complications. Various radiation delivery techniques have been used to deliver the desired dose of radiation to the target area while keeping the doses to nearby structures within constraints.The main aim of this study is to quantify doses delivered to the organs at risk (OARs) including heart, left lung, spinal cord, and contralateral breast, and to the planning target volume (PTV) using Field-in-Field (FIF) and Volumetric Modulated Arc Therapy (VMAT).Patients and methodsA retrospective review of 15 left-sided breast cancer patients was done. All the patients underwent breast-conserving surgery and adjuvant radiation. For every patient, two different radiation treatment plans were formulated and compared for the PTV coverage and doses to OARs, including heart, ipsilateral lung, spinal cord, and contralateral breast.The radiation treatment techniques utilized for this purpose were FIF and VMAT. The homogeneity index (HI), and conformity index (CI) required for the treatment planning were also calculated. Data was analyzed using Statistical Package for the Social Sciences (IBM Corp., Armonk, USA). An Independent T-test was used for statistical analysis.ResultsThe mean age was 41 years and the majority of them were stage II. Total nine patients were given 4005centi Gray (cGy) in 15 fractions (fr) followed by 10Gy boost, hence receiving a total dose of 5005cGy in 20fr. While remaining six patients were given a total dose 4005cGy in 15fr without any boost.All patients were hypofractionated and the dose was delivered at a rate of 267cGy per fr. The FIF technique utilized in breast cancer radiation significantly reduced the mean doses to OARs: mean heart dose (3.81cGy), ipsilateral lung dose (V16- 15cGy), mean contralateral breast dose (0.03cGy), and maximum spinal cord dose (0.18cGy); as compared to VMAT technique which delivered comparatively higher doses: mean heart dose (8.85cGy), ipsilateral lung dose (V16- 19.82cGy), mean contralateral breast dose (4.59cGy), and maximum spinal cord dose (7.14cGy).There was a significant mean difference between doses of OARs and all p-values were statistically significant (p<0.005). Moreover, the FIF technique also improves the dose distribution of PTV in terms of dose homogeneity. However, the conformity index is more enhanced with VMAT as opposed to FIF.ConclusionThe FIF technique is more advantageous than the VMAT planning technique because it provides better dose distribution in terms of PTV coverage and significantly lower doses to OARs in radiotherapy to left-sided breast cancer.

Dosimetric evaluation of IMRT (SS / SW) and VMAT treatment plans for nasopharyngeal cancer

Introduction: Radiotherapy of the sphere ORL is still difficult by the presence of complex geometries and very sensitive organs around the target volume.This weapon has benefited from the advances of the VMAT (Volumetric Modulated Arc Therapy) technique, introduced in 2009, it combines the advantages of dynamic arc therapy techniques with the advantages of conformational radiotherapy techniques with intensity modulation (RCMI) by stationary beams.Materials and Methods: The treatment plans of the 4 patients were compared and treated with SS, SW, and VMAT (6MV X-ray beam). The target volumes were three: PTV 70, PTV 63, and PTV56. The organs at risk delineated were the spinal cord, the brainstem, the parotid gland .The dose was delivered once a day, five days a week and in 35 sessions in Integrated Boost (Simultaneaous Integrated Boost (SIB)), aiming to deliver the prescribed dose to the tumor volume while respecting the dose constraints in the organs at risk and minimizing their degree of toxicity.Results: Similar results were found for target volume coverage (Dmax). The SS technique allowed better parotid sparing, which explains its contribution to limiting late complications such as xerostomia. The VMAT technique allows better protection of the brainstem by reducing about 6 Gy, for the spinal cord the doses received were almost equal. Finally, there is no statistically significant difference between the different techniques.Conclusion: All these results conform the conformational capacities of these innovative techniques from a dosimetric and above all clinical point of view. Their ability to cover the target volumes while largely respecting the constraints on organs at risk.

Treatment planning of volumetric modulated arc therapy and positioning optimization for hippocampal-avoidance prophylactic cranial irradiation.

BackgroundHippocampal‐avoidance prophylactic cranial irradiation (HA‐PCI) offers potential neurocognitive benefits but raises technical challenges to treatment planning. This study aims to improve the conventional planning method using volumetric modulated arc therapy (VMAT) technique and investigate a better patient’s head positioning to achieve a high quality of HA‐PCI treatment plans.MethodsThe improved planning method set a wide expansion of hippocampus as a special region for dose decline. The whole brain target was divided into two parts according to whether the slice included hippocampus and their optimization objectives were set separately. Four coplanar full arcs with partial field sizes were employed to deliver radiation dose to different parts of the target. The collimator angle for all arcs was 90°. Tilting patient’s head was achieved by rotating CT images. The improved planning method and tilted head positioning were verified using datasets from 16 patients previously treated with HA‐PCI using helical tomotherapy (HT).ResultsFor the improved VMAT plans, the max and mean doses to hippocampus were 7.88 Gy and 6.32 Gy, respectively, significantly lower than those for the conventional VMAT plans (P < 0.001). Meanwhile, the improved planning method significantly improved the plan quality. Compared to the HT plans, the improved VMAT plans result in similar mean dose to hippocampus (P > 0.1) but lower max dose (P < 0.02). Besides, the target coverage was the highest for the improved VMAT plans. The tilted head positioning further reduced the max and mean doses to hippocampus (P < 0.05), significantly decreased the max dose to lens (P < 0.001) and resulted in higher plan quality as compared to nontilted head positioning.ConclusionsThe improved planning method enables the VMAT plans to meet the clinical requirements of HA‐PCI treatment with high plan quality and convenience. The tilted head positioning provides superior dosimetric advantages over the nontilted head positioning, which is recommended for clinical application.

Comparison between two different patient specific QA systems for detection of errors introduced to VMAT plans

Volumetric Arc Therapy (VMAT) technique involves varying the gantry angle, MLC position, and the dose rate as the radiation is delivered. To ensure the integrity of VMAT plans, each plan must be verified through a quality assurance (QA) process, which is known as patient-specific QA. The quality assurance system should detect the planning and machine errors. This study aims to investigate the sensitivity of two different patient specific QA systems to detect errors in VMAT plans.

Radiotherapy plan evaluation indices

To classify the available plan evaluation indices and compare the dosimetric suitability of these indices. Available published plan evaluation indices were categorized. Conformity index (CI) into two groups, one group contains those CI formulas which do not consider critical structure and other group contains those CI formulas which consider planning target volume (PTV) coverage, normal tissue and critical structure sparing simultaneously. Various homogeneity index (HI) formulas extracted from literature. Structure data sets of 25 patients were taken under consideration comprising of various sites. For each patient, two plans were created using Volumetric Arc Therapy technique. First type of plan (Plan-A) were generated considering all tissue objectives for targets and Organ at Risks (OARs) whereas second type of plan (Plan-B) were generated considering only targets tissue objectives and excluding OARs tissue objectives during plan optimization and dose calculation. Planning evaluation parameters were compared between Plan-A and Plan-B. CI calculated by various formulas in two different scenarios presented <2% variation. Any commonly used CI formula failed to differentiate the two different planning situations. On comparison between HI of two different scenario, it is observed that there are four formulas of HI which showed negligible variation but two formulae: S-index and HI (D) showed marginal variation. It is also observed that when OARs are removed from optimization dose homogeneity improved which is specifically pointed by sigma index formula. CI, which has assimilated the presence of OAR in their formulation, shows more reliability in plan evaluation. Sigma index was found to be more efficient formula while evaluating homogeneity of a treatment plan.

Superficial radiotherapy and volumetric modulated Arc therapy for skin cancers within hamartomatous skin in patient with PTEN mutation: A case report

Phosphatase and tensin homolog (PTEN) gene acts as a tumour suppressor gene. Mutations of this gene are a step in the development of many cancers. Sufferers can have large fields of symptomatic hamartomatous skin change especially in sun exposed areas. RT has been reported to cause increased acute toxicity in this cohort. A 78-year-old fit male had a confirmed PTEN variant LRG_311t1 Exon 5, c353A&gt;C. Symptomatic skin lesions of left frontal scalp and left nasal ala were confirmed on punch biopsy to be basal cell carcinoma (BCC) and he was referred for definitive radiotherapy (RT). He was treated with lesion based superficial radiotherapy to the left nasal ala to a total dose of 50 Gy in 25 fractions given at 5 fractions per week using a Xstrahl 300 machine via a 3cm circle applicator at 30cm source surface distance with a generating energy of 100 kV. The left frontal scalp was treated with a field-based volumetric modulated arc therapy technique to a planning target volume (PTV) of 74.8cm3 to 45 Gy with a simultaneous integrated boost PTV to 55 Gy of 4.1 cm3 to the BCC, all in 25 fractions. He developed the expected desquamation, erythema and mucositis within the nasal field and desquamation and erythema in the left temple. The PTEN mutation had no visible increase on the acute side effect profile compared with those without the mutation. After more than 6 months, the areas treated with RT remained clear of symptomatic hamartomatous skin change with no late toxicities. To our knowledge this is the longest benefit received of any treatment for fields of symptomatic hamartomatous skin change associated with PTEN mutation. It is also a report of not observing increased acute toxicity of RT in the definitive treatment of skin cancer in those with proven PTEN mutation. This one case adds evidence that definitive RT to skin may be delivered safely in this cohort. More studies with multiple patients with longer follow up are needed to confirm that those suffering with PTEN mutation can be safely and successfully treated with definitive RT for skin cancer and fields of symptomatic hamartomatous skin change with no increase in late effects.

Stereotactic Body Radiation Therapy (SBRT) for Liver Oligometastases: Outcomes and Safety.

The aim of this study was to investigate adverse effects, progression free survival (PFS), one-year local control (LC) and one-year overall survival (OS) of patients with liver oligometastases treated with stereotactic body radiotherapy (SBRT), and whether there was a significant difference in these parameters in patients with primary colorectal cancer compared to other tumor localizations. Patients were simulated using four-dimensional computed tomography (4DCT). Using volumetric modulated arc therapy (VMAT) technique, SBRT was performed on 16 patients with <3 liver metastases. The prescribed dose was 60 Gy in 8 fractions (BED 105 Gy). Cone beam CT (CBCT) was used for image guidance before each fraction with online correction. There were no adverse effects. Median PFS for all patients, patients with primary colorectal cancer, and patients with primary non-colorectal cancer was 11 months (SE 2.1), 16 months (SE 2.8), 6 months (SE 2.4), respectively. There was no significant difference in the PFS for these two observed groups (P=0.09). The one-year LC was 62.5%. Patients with primary colorectal cancer had one-year LC of 87.5%, while the group of patients with primary non-colorectal cancer had one-year LC of 37.5% (P=0.063). The total one-year OS was 87.5%. In the group of patients with primary colorectal cancer, the one-year OS was 100%, while in the group of patients with primary non-colorectal cancer, the one-year OS was 75% (P=0.317). SBRT with 8 × 7.5 Gy can be safely delivered and is effective method of treating liver oligometastases.

The patient-reported outcome measures in oropharyngeal, laryngeal and hypopharyngeal cancer patients treated with Volumetric Modulated Arc based simultaneous integrated boost radiotherapy.

To assess the change in the quality of life (QOL) in head and neck cancer patients treated with Simultaneous Integrated Boost (SIB) by Volumetric Modulated Arc Therapy (VMAT) technique. Thirty patients with localised head and neck cancers (Stage II- IVa) were treated with VMAT and SIB technique. The three-dose levels prescribed were 68.2 Gy at 2.2 Gy/fraction, 62 Gy at 2 Gy/fraction and 55.8 Gy at 1.8 Gy/fraction to the high, intermediate and low-risk volumes respectively. Concurrent chemotherapy with cisplatin 100 mg/m2 was administered once in three weeks. Acute toxicities were evaluated and scored according to the RTOG grading system. Quality of life (QOL) was assessed using European Organization of Research and Treatment of Cancer (EORTC) QLQC30 and HN35 questionnaires at baseline and in three instances (immediately, one month and three months after the radiotherapy). Out of the total 30, 80% patients had a complete response (CR) at the median follow up of 12 months, while three patients died because of progression, and the remaining 3 had stable disease. All planning objectives were achieved for organs at risk and planning target volume(PTV). There was a statiscally significant(p value < 0.001) reduction in global quality of life scores at the end of treatment when compared to baseline scores, but by three months, there was the return in the QOL scores in most scales similar to the baseline value. VMAT based Simultaneous boost radiotherapy is a feasible and safe strategy in terms of toxicityprofile with an acceptable transient change in the quality of life and allows a faster return to baseline quality of life.

Examining the utility of lower dose radiotherapy for localised primary ocular adnexal MALT lymphoma.

IntroductionMost primary ocular adnexal lymphomas are those involving mucosa‐associated lymphoid tissue (MALT). Radiotherapy (RT) dose regimens in the literature vary from the historically used high doses (up to 56 Gy) to lower dose RT. We aimed to examine our institution’s experience with the use of orbital RT for treating early‐stage primary ocular adnexal MALT lymphoma (POAML).MethodsPatients treated for stage I or II POAML over a 12‐year period (July 2006 to June 2018) were identified through institutional databases. Data were retrospectively collated through review of patient records. Descriptive statistical methods were employed to analyse the data.ResultsEighteen patients (median age of 67; range 44‐87yrs) with localised POAML (3 cases of bilateral disease) were identified, resulting in a total of 21 evaluable orbits. Eight (44%) patients were female, and all were documented to be of good performance status (ECOG 0‐1). The median follow‐up was 34 months (range 8‐75 months). The commonest dose fractionation used was 20 Gy in 10 fractions (n = 13 orbits) and a 3D conformal or volumetric modulated arc therapy (VMAT) technique was used in the majority of cases. None of the patients experienced an in‐field recurrence. One patient had experienced a contralateral orbital recurrence two years post‐unilateral orbital RT for orbital MALT lymphoma. Three patients experienced distant relapse.ConclusionThe use of lower dose orbital RT such as 20 Gy in 10 fractions (or radio biologically equivalent) yields excellent local disease control in the management of ocular adnexal MALT lymphoma. The durability of the response appears to be favourable. Given the indolent nature of the disease and the low levels of toxicity associated with lower dose orbital RT, this regimen remains our favoured approach to the management of localised POAML.

The Hippocampus: A New Organ at Risk for Postoperative Radiation Therapy for Bucco-alveolar Cancer? A Dosimetric and Biological Analysis

PurposeA significant proportion of patients with bucco-alveolar cancer are long-term survivors, warranting attention to survivorship issues. Decline in neurocognitive function after cranial irradiation for brain tumors correlates with a hippocampal maximum dose (Dmax) of more than 16 Gy, minimum dose (Dmin) of more than 9 Gy, and dose to 40% of the hippocampal volume (D40%) exceeding 7.3 Gy in 2-Gy equivalent dose (EQD2), respectively. We analyzed the utility of sparing the hippocampus in postoperative radiation therapy (PORT) for patients with bucco-alveolar cancer, given the proximity of target volumes to the hippocampus, by virtue of inclusion of the infratemporal fossa. Methods and MaterialsWe instituted hippocampal sparing for patients with bucco-alveolar cancer receiving PORT in March 2018. Ten prior and 10 subsequent consecutive patients with pathologically staged I-IVA cancers of the buccal mucosa, alveolus, and retromolar trigone formed the control group (no hippocampal sparing) and the study group (hippocampal sparing), respectively. The brain and temporal lobes were prescribed dose constraints in both groups. Patients received doses of 60 to 66 Gy at 2 Gy per fraction using the image-guided intensity modulated radiation therapy / volumetric modulated arc therapy technique. Treatment plans were evaluated for (1) hippocampal dosimetric parameters, (2) planning target volume dosimetry and plan-quality indices, and (3) biological indices of equivalent uniform dose (EUD) and normal-tissue complication probability (NTCP) for impaired neurocognitive function. ResultsHippocampal sparing significantly reduced the hippocampal DmaxEQD2, DmeanEQD2, and D40%EQD2 from 27 Gy to 10.9 Gy (P = .002), 14.3 Gy to 6.4 Gy (P = .002), and 15.5 Gy to 6.6 Gy (P = .005), respectively, with comparable plan-quality indices. The radiobiologically robust endpoints of ipsilateral hippocampal EUD (P = .005) and NTCP (P = .01) were statistically significantly improved. ConclusionsMeaningful dosimetric benefit, corroborated with radiobiological indices, was observed with hippocampal sparing. The feasibility and benefit of hippocampal sparing supports our view that the hippocampus should be incorporated as an organ at risk and attention should be given to neurocognitive function in patients with bucco-alveolar cancer who are receiving PORT.