Total scalp irradiation is used to treat melanoma, lymphoma, angiosarcoma, mycosis fungoides, basal, and squamous cell carcinoma. Treatment of the total scalp is typically reserved for diffuse disease presentations, recurrences and its intent is mostly palliative1-5. Planning and delivering radiation treatment to whole of the scalp is technically challenging due to the geometry of the head and the close relation of the scalp to the brain, optical structures, and other nearby healthy organs at risk. The main challenge of scalp irradiation is to deliver a homogenous dose while sparing the normal brain and other healthy structures. The thickness of scalp is only 4–6 mm, so traditionally electrons have been the modality of choice because of its high surface dose, rapid dose falloff and its finite range, with acceptable dose received by the brain resulting in only minimal treatment-related toxicity. Nonetheless, electron treatments have its own difficulties in terms of the scattering of electrons at oblique surfaces which can create unusual dose distributions6. Many techniques using photons and mega voltage electron beams have been described in the literature. Most of the techniques have used photons obtaining a good conformation of dose to target and protection of surrounding normal tissue as well7-11. Techniques such as static electron fields, electron arc therapy, intensity modulated electron radiation therapy, helmet mold-based surface brachytherapy, volumetric arc therapy and helical tomotherapy have been used worldwide. In this report, we describe a combination of volumetric arc therapy technique and electron therapy for boost for a patient with recurrent tumours in scalp.
Objective Pretreatment imaging plays a crucial role in determining geometric positional uncertainty of the patient during radiotherapy. Our purpose is to investigate the effect of frequent pretreatment imaging protocol (scenario) on actual dose delivery in radiotherapy. This paper presents a critical analysis of frequent imaging protocol with respect to Idealized daily imaging protocol (IDIP). Methods and materials Retrospective patients of Ca-carcinoma cervix, Ca-buccal mucosa, Ca-tongue treated with intensity-modulated radiation therapy (IMRT) undergoing daily cone beam computed tomography (CBCT) imaging protocol was selected for this study. Every treated fraction of these patients was simulated considering its daily geometrical setup uncertainties occurred. Indirect evaluation of virtual treatment plans was conducted in the treatment planning system (TPS) for 3 days a week, 2 days a week, and 1 day a week frequency imaging protocols. Results obtained from these frequent imaging protocols were compared with IDIP. Result Deviation between predicted and delivered dose found increasing with decreasing frequency of imaging. Significant deviations were observed in all the estimated plan quality parameters for patients treated with frequent imaging protocols and IDIP. Deviations were found more in case of pelvis sites than head and neck sites. Conclusion This study plays a vital role in establishing optimum pretreatment imaging protocols in busy clinics. Three days a week imaging protocol is the best suit protocol found with minimal deviation and ample implementation feasibility. This study proposed an opinion pertaining to the revision of setup margin formula in order to accommodate variation due to imaging techniques and frequency of imaging attempted during radiotherapy.
Objectives Early-stage breast cancer patients survive longer so a radiotherapy technique which can reduce late toxicity is important. In this study, we made a dosimetric comparison of supine and prone breast irradiation techniques in patients with left breast cancer. Methods Ten patients scheduled for whole-breast radiotherapy after lumpectomy were included in this study. The patients underwent computed tomography scans in both supine and prone positions on a breast board. The breast was contoured as per standard guidelines. Treatment planning was done for both the positions. A dose of 40 Gy/15#/3 weeks was prescribed. Mean dose to the heart and left lung was calculated for each patient in the supine and prone positions. Dose-volume histograms were generated and compared between the two sets. Paired t test was applied to test the significance of difference between the mean doses received by the heart and left lung for the two techniques. The difference was considered statistically significant if p value was < 0.05. Results The heart and left lung were better spared in the prone position compared to supine. Mean heart dose in the supine and prone positions was 4.5558 Gy and 2.063 Gy (p = 0.02), respectively. Mean lung dose in the supine and prone positions was 6.5797 Gy and 0.8491 Gy (p = 0.001), respectively. Rotational setup error was noted in 3 and 1 patient in the prone position and supine position, respectively. Conclusion The prone position for the radiotherapy treatment of left breast cancer was dosimetrically better than the supine position in terms of mean dose to the heart and left lung.
Gamma-ray stereotactic radiosurgery systems available commercially contain either stationary or rotational source configuration. Rotational systems reduce the number of sources utilized and can also provide beneficial dosimetric properties. In this study, we explore the dosimetric advantage of a novel rotating gamma-ray design for stereotactic body radiotherapy (SBRT) as compared to the well-established CyberKnife system. CybeRay (OUR United Corp., Xian, China) is a rotating gamma-ray system (RGS). Its treatment head can rotate 360° in the axial plane and swing 35° in the superior direction. It includes 13 Co-60 sources focusing on the isocenter. The RT Pro planning system (Prowess, Concord, CA) was used for CybeRay treatment planning, while the Multiplan software (Accuray, Sunnyvale, CA) was used for CyberKnife treatment planning. Twelve SBRT patients previously treated with CyberKnife were re-planned for CybeRay, and their treatment plans were compared based on isodose distributions, dose volume histograms, conformity index (CI), and the estimated treatment time. The planning target volume ranged from 4.4 to 124.2 cc. Both treatment systems provided excellent SBRT plans that meet our clinical acceptance criteria. The mean value of CI was 1.25 for both CyberKnife and CybeRay (p = 0.03). The estimated treatment delivery time for the CyberKnife plans ranged from 13 to 53 min as compared to 6 to 54 min with CybeRay (p = 0.02). CybeRay was superior concerning peripheral doses appearing as excessive isodose lines extending to distal normal tissues. The new CybeRay machine showed promising dosimetric capabilities for stereotactic radiosurgery and radiotherapy of extra- and intra-cranial lesions.
Objective Many cancer patients are treated at treatment centers staffed by community radiation oncologists (CRO). Patients choose these facilities for location convenience and anticipate equivalent care to "high volume" centers despite contrary literature. Local CROs hypothesized that a two-step quality assurance (QA) program that added early contour and case review would improve confidence in radiation treatment plan quality and reduce variability across facilities. Methods Five physicians at five academic satellites participated in the pilot two-step QA program. This program established an efficient, secure, HIPPA compliant workflow to review case details and contours on CT simulation after uploading to a remote access server on a commercially available platform. Results Over 12 months, 148 patient contours were reviewed by at least one CRO with an average of 2 reviewers per case. Reviewers approved 67% without change, requested clarification or change in 28%, and would not approve 4% of cases unless revised. The most common reasons cited for change request were "review GTV-volume increase" and "review CTV-volume increase." Eighty-eight percent of treated cases that were not approved initially subsequently completed recommended modifications. Published literature was shared for 29% cases and sub-specialist consulted for 19% of cases. Conclusion A two-step QA program was considered highly valuable by all participants allowing easily implanted mechanisms for standardization, higher case volume, and shared educational resources for small academic satellite CROs who are faced with the challenge of caring for a diverse community cancer population. Feasibility suggests the model could serve as a model for other CRO.
Biological subtypes have been strongly correlated with loco-regional recurrence after definitive treatment for localized breast cancer. Brain metastases (BM) occur in 15% of patient diagnosed with breast cancer (BC). Therefore, we sought to determine whether biologic subtype is predictive of local control (LC) in BC patients with BM treated with stereotactic radiosurgery (SRS). This is a single-center retrospective study conducted with Institutional Review Board approval for the period January 1, 2004–December 31, 2018. Eligibility criteria included (1) histopathologic proven BC with documented biologic subtype, (2) presence of BM treated with SRS (single fraction), (3) follow-up MRIs, and (4) clinical follow-up. Patients were subdivided into three biologic subtypes: ER+/HER2- (“luminal”), HER2+, and ER-/PR-/HER2 (TN). All patients were treated with LINAC-based SRS with dose according to published guidelines. Cox proportional hazard model and Kaplan-Meier were used for statistical analysis of LC and overall survival (OS). With a median follow-up of 11.1 months, 17 BC BM in 50 consecutive patients were included in this study. The median disease-specific GPA was 2.0, and all patients received systemic chemotherapy and/or hormonal therapy. The 12-month LC rates for the entire cohort were 85%, 87%, and 49% for luminal, HER2+, and TN, respectively, with a significantly shorter time to local failure for the TN subtype (p = 0.014). The 12-month OS rates were 83%, 88%, and 80% for luminal, HER2+, and TN, respectively, with a trend toward shorter OS in the TN group. This study shows that in BC patients with BM treated with SRS, biologic subtype affects LC. Consideration of radiation treatment intensification or altered fractionation to improve LC may be indicated for the TN subtype. Further multicenter studies are necessary to corroborate our results.
Lymph node (LN)–positive cervical cancer is associated with a poor prognosis. We report outcomes for women with LN-positive cervical cancer treated with intensity-modulated radiation therapy (IMRT) with dose-escalated simultaneous integrated boost (SIB) to involved LNs. Between 2005 and 2017, 59 women with LN-positive, non-metastatic, cervical cancer underwent definitive chemoradiotherapy (CRT) with an image-guided LN boost to a median dose of 56.25 Gy in 25 fractions. Acute and late adverse events (AEs) were recorded per common terminology criteria for adverse events. The Kaplan-Meier method was used to estimate the overall survival (OS), progression-free survival (PFS), and locoregional control (LRC). Median age was 49 years (IQR 37–56). Women had involved LNs in the pelvis (56%) or pelvis and para-aortic (PA) LNs (44%), with a median of 3 (IQR 2–6) grossly involved LNs per patient. Median follow-up was 30 months (IQR 11–45). Estimated 3-year OS, PFS, and LRC were 67% (95% CI, 51%–84%), 60% (95% CI, 45%–76%), and 89% (95% CI, 76%–99%), respectively. PA LN involvement (HR 2.51; 95% CI, 1.05–5.99; p = 0.04) and the presence of ≥ 4 grossly involved LNs (HR 2.79; 95% CI, 1.16–6.71; p = 0.02) were associated with a higher risk of disease progression on univariate analysis. The incidence of treatment-related acute grade 3+ acute GI or GU AEs was 3%, while late GI or GU treatment-related AEs occurred in 12%. Chemoradiation with a LN-directed SIB for women with LN-positive cervical cancer is well tolerated and is associated with excellent oncologic outcomes. In this report, we evaluated the oncologic efficacy and adverse events associated with definitive chemoradiotherapy with a simultaneous integrated boost to grossly involved lymph nodes for women with lymph node–positive cervical cancer. We have identified acceptable rates of adverse events and excellent oncologic outcomes, even in a very high risk cohort of women with cervical cancer.
Stereotactic body radiotherapy (SBRT) is increasingly used for pancreatic cancer; however, there is a dearth of data guiding its use after prior SBRT. We conducted an institutional review board (IRB)–approved retrospective study of patients treated with SBRT for pancreatic cancer on two occasions from 2005 to 2018. Patients were followed for response to treatment and toxicity assessment (Common Terminology Criteria for Adverse Events [CTCAE] version 5). Demographic and survival data for the cohort were described using frequencies, medians, and ranges. Survival analysis was performed using the Kaplan-Meier method. Twenty-four patients met the inclusion criteria. Local control at 1 year after the second SBRT treatment was 77.2%. Median survival from 1st SBRT course and 2nd SBRT course was 31 months and 13 months, respectively. Most patients were treated with 24 Gy in 3 fractions for their first course and 25 Gy in 5 fractions for their second course. Thirteen patients did not undergo surgery, and 9 had detailed radiation treatment planning data available with non-distorted GI anatomy. For the total summation dose (first and second courses of SBRT combined), the D0.03cc and D1cc to the duodenum received up to 46.1 Gy and 42.3 Gy, respectively, while the stomach received up to D0.03cc of 49.2 Gy and D1cc of 43.8 Gy. SBRT after prior SBRT for pancreatic cancer is a reasonably safe and efficacious treatment that leads to durable local control and reasonable survival. Retreatment of the duodenum and stomach with a D0.03cc and D1cc of at least 40 Gy may be safe, although more data is needed.
Automatic cone beam computed tomography (CBCT)–based image matching for set-up verification is recommended as compared with 2D image match for post-operative local/loco-regional radiotherapy of breast cancer patients by volumetric modulated arc therapy (VMAT) technique. However, in a supine position, off-midline peripheral body clinical target volume (CTV) of unilateral breast cancer patients immobilized on breast and lung board of All-in-One (AIO) positioning system may necessitate augmented movement of the couch in ‘x’ and ‘z’ axes thereby raising the risk of collision of x-ray sources/detector system with couch. VMAT was planned by a pair of partial arcs for the whole target volume for seven consecutive post-operative breast cancer patients (five post-mastectomy and two post-breast conservation patients). Tattoo-based set-up by the shift of treatment table in x-, y-, and z-axis as determined by treatment planning system followed by x-rays with planar image acquisition and online 2D image matching with Digitally reconstructed radiographs (DRRs) was performed for set-up verification. In-room 360° rotation of x-ray source and detector system of a linear accelerator (linac) was performed before x-ray planar image acquisition. Completion of 360° in-room rotation of x-ray source and detector system of linac around the machine isocentre was not possible in six out of seven patients due to the possibility of collision of the gantry with contralateral side of the couch. Performing CBCT for generating 3D images for computed tomography (CT) reconstruction may not be practical for patient set-up verification of post-operative radiotherapy of unilateral breast cancer patients positioned supine on breast and lung board.
The aim of this study was to compare dosimetric variations using the three-dimensional conformal radiotherapy (3DCRT), dynamic intensity-modulated radiation therapy (D-IMRT), and static intensity-modulated radiation therapy (S-IMRT) techniques for glottic cancer. Ten patients with early-stage glottic cancer were retrospectively selected and evaluated. The 3DCRT and IMRT treatment plans were performed using the solution commercialized by Varian with the Eclipse treatment planning system (TPS). For each patient, five different treatment plans were created and compared with respect to the doses received by the organs at risk (OARs) including the carotid arteries, thyroid gland, and spinal cord; the dose homogeneity index (DHI); conformity indexes (CI); and total monitor unit (MU) counts required for the treatment. The Mann-Whitney U test was used for statistical analyses. Statistically significant differences for the 3DCRT, D-IMRT, and S-IMRT techniques were observed for the planning target volume (PTV) mean and maximum doses. The results of this study indicated an increase in DHI for 3DCRT compared with D-IMRT and S-IMRT. Furthermore, the S-IMRT technique led to the superior decreased dose to the OAR. The 3DCRT plans performed better at the Dmax of the spinal cord and MU counts. The D-IMRT and S-IMRT techniques allowed more homogeneous dose distributions in PTV. Considering the dose to OAR, S-IMRT was more appropriate rather than 3DCRT and D-IMRT.
Objective Stereotactic body radiation therapy (SBRT) is a definitive treatment option for early-stage non-small cell lung cancer (NSCLC), but access is not universal. This study evaluated trends in SBRT utilization to identify potential disparities. Methods This was a cancer registry study using the National Cancer Database (NCDB). The NCDB was queried for patients diagnosed with early-stage NSCLC from 2004 to 2016. Patients receiving surgery, chemotherapy, radiation not meeting criteria for SBRT, or other ablative procedures were excluded. SBRT use in treatment facilities over time was evaluated, and patients were analyzed by various socioeconomic factors to determine predictors of SBRT vs no-treatment. Multivariate and Cox regression analyses were performed to determine the extent to which decreased treatment with SBRT may be contributing to worse overall survival. Results A total of 65,376 patients were included. There was a significant increase in SBRT use from 2004 (n = 80) to 2016 (n = 7948). Patients treated in academic centers were more likely to get SBRT than community programs, but the use in the community has increased in recent years. Covariates associated with decreased use of SBRT included lack of insurance (OR 0.45, p < 0.0001), Hispanic (OR 0.79, p < 0.001), black (OR 0.59, p < 0.0001), or 'other' race (OR 0.48 p < 0.0001), and living in a less-educated community (OR 0.83, p < 0.001). On multivariate analysis, use of SBRT was associated with decreased risk of death (HR = 0.48, p < 0.001), and patients treated with SBRT had increased median overall survival compared with patients receiving no treatment (39.6 versus 14.9 months, p < 0.001 by log-rank test). Conclusion SBRT use is increasing across all treatment facilities but there are notable health disparities based on socioeconomic factors including race that may be contributing to worse survival outcomes.
Purpose To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose delivered to the organs at risk (OARs) during lung stereotactic body radiation therapy (SBRT). Materials and methods This study included 55 patients (30 males and 25 females) with lung cancer who had a small gross tumor volume (GTV). SBRT lung cancer patients were treated with a prescribed dose of 60 Gy in 4 to 8 fractions. Radiotherapy plans were planned in Pinnacle 9.10 with two partial dynamic conformal arcs (DCAs) for the peripheral region (PR) and three to four partial DCAs for the central region (CR). The amplitude of tumor motion and their impact on the maximum dose delivered (D-max) to the OARs were evaluated in the upper lobe (UL) and lower lobe (LL) in cases of CR and PR tumor's localizations. Results The median tumor motions between CR and PR were 4.5 vs 2.2 mm in the UL and 12.5 vs 7.0 mm in the LL. Max dose delivered to the OARs between CR and PR in the UL and LL were as follows: 6.7 vs 8.9 Gy and 9.1 vs 11.7 Gy for the spinal cord; 15.2 vs 0.6 Gy and 22.4 vs 7.6 Gy for the heart; and 11.7 vs 10.8 Gy and 14.8 vs 9.8 Gy for the esophagus, respectively. Conclusion The dose received by the OARs depends on the amplitude of tumor motion and is relative to the OAR's location and motion, due to patient respiration and heart contribution.
Early postoperative nodal recurrence (EPNR) of oral squamous cell carcinoma (OSCC) is not uncommon. Such recurrences may change the intent of treatment and/or volumes of radiotherapy. Contrast-enhanced computed tomography (CECT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have a similar ability to detect lymph node metastasis. However, obtaining postoperative imaging for detecting early recurrence and the initiation of postoperative radiotherapy (PORT) are competing priorities. Hence, we assessed the feasibility of simulation computed tomography (CTSim) for the detection of EPNR in OSCC. CECTSim of 5-mm slice thickness with thermoplastic immobilization was performed in 21 consecutive postoperative patients with OSCC. Treating radiation oncologists and trained radiologists used CECTSim to screen and evaluate the presence of early regional lymph node recurrence. Six out of twenty-one consecutive postoperative OSCC patients had radiological evidence of EPNR on CECTSim. Except for one patient, all EPNRs were limited to contralateral level 1–3 regional nodes in this small series of postoperative OSCC patients. The detection of EPNR on CECTSim necessitated a change in the radiation treatment volume and the corresponding prescribed dose to the target volume. CECTSim may be helpful in the detection of EPNR in OSCC and may preclude the need for additional imaging before the start of PORT. CECTSim may also facilitate the appropriate determination of the radiation volume and appropriate dose to the corresponding target volume.
Objective For patients presenting with recurrent, inoperable, or metastatic sarcoma, treatment options are limited. The inherent low radiosensitivity of many sarcoma histologies can limit effectiveness of palliative radiation for these patients. Stereotactic radiation (SBRT) allows escalation of biologically effective dose while limiting dose to normal tissues, which is particularly important in previously irradiated tissues. In this retrospective cohort study, we examine the efficacy of SBRT in the palliation of sarcoma. Methods A retrospective cohort study was performed of patients treated at a single large tertiary academic medical center with SBRT for management of sarcoma from 2011 through 2016. Details regarding patient demographics, treatment context, tumor histology, treatment parameters, and disease outcomes were recorded. Descriptive statistics and Cox analysis of factors associated with improved local control were examined. Results Results were available on 22 tumors treated with SBRT in 14 patients. Median follow-up was 6.7 months. Median tumor size was 4.8 cm, with a median total dose and dose per fraction of 27.5 Gy and 6 Gy/fraction, respectively. There were 6 recurrences, with a 1-year local control of 62%. Seventy-nine percent of symptomatic lesions had improvement in their pain. On univariate Cox-analysis, total dose, performance status, and BMI were found to be significantly associated with local control, and dose per fraction was significantly associated with local failure. One-year overall survival was 37%. Conclusion Our institutional experience provides encouraging evidence of the feasibility of SBRT in the palliation of sarcoma. Poor overall survival is a substantial competing risk in these patients. Further studies will be required to identify the ideal dose and fractionation across histological subtypes. Prospective clinical trials may be warranted.
Objective SARS-CoV-2 infection may manifest with minimal or no clinical symptoms. However, signs of infection may appear on routine imaging obtained in the care of patients with cancer. The management of patients planned for chemoradiation with asymptomatic or mildly symptomatic SARS-CoV-2 infection is uncertain. Methods Here, we present a case study of a mildly symptomatic patient with anal cancer diagnosed with SARS-CoV-2 from a staging PET-CT scan. Results PET-CT scan for anal cancer staging demonstrated pulmonary avidity suspicious for an infectious, rather than malignant, process. In the setting of these imaging findings and new-onset anosmia, viral polymerase chain reaction was ordered and found to be positive for SARS-CoV-2. To avoid myelosuppression in the setting of active infection, planned chemoradiation was delayed until cessation of viral shedding. Conclusion In the COVID-19 era, oncologists obtaining routine staging imaging should have high diagnostic suspicion for subclinical SARS-CoV-2 infection. To avoid precipitating severe pneumonia and hospitalization, multidisciplinary discussion with risk-benefit analysis is recommended before initiating immunosuppressive therapies such as chemoradiation.
Aim To compare quality of life and radiation toxicity in patients applied with Tomo-helical intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiation therapy (3D-CRT) as adjuvant radiotherapy because of breast cancer. Material and method The study included a total of 403 patients. Fifty-eight percent of patients were treated with 3D-CRT, and 42% of patients were treated with Tomo-helical IMRT. Radiation toxicity was evaluated according to the Radiation Therapy Oncology Group (RTOG) toxicity criteria. Quality of life was evaluated using the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 Quality of life scale version 3-Turkish and the EORTC QLQ-BR23 questionnaires. These questionnaires were completed by all patients at 4 different time points: the start of RT (T-1); the end of RT (T-2); 1 month after completion of RT (T-3); and 6 months after completion of RT (T-4). Statistical data were analysed using the Chi-square and MANOVA tests. Results Radiotherapy-related skin, upper gastro-intestinal system, white blood count and neutrophil toxicity were observed to be higher in the patients treated with 3D-CRT (p < 0.001). No difference was determined between the radiotherapy techniques according to the EORTC-C30 (p > 0.050). In the patients treated with Tomo-helical IMRT, the scores of breast symptoms (p = 0.014), sexual function (p = 0.003) and sexual pleasure (p = 0.020) in the sub-dimension scales of the EORTC-BR23 were found to be better compared with those of patients treated with 3D-CRT. Conclusion The findings of RT toxicity and quality of life appear to be superior in patients applied with Tomo-helical IMRT compared with patients treated with 3D-CRT.
Extending the superior border of the breast tangent fields to include the low axilla is a technique employed to target the axillary lymph node (LN) without adding additional fields. This technique, commonly referred to as high tangents, is typically done in the supine position. The feasibility of delivering high tangents in the prone position has never been reported. Patients from 2012 to 2018 at a single institution who were prescribed treatment with high tangents using two tangentially opposed beams in the prone position were identified. The levels I–III axillary LNs were retrospectively contoured. The dose delivered to the LN, breast, and organs at risk was calculated using the original treatment plan. For LN, coverage was defined as > 90% of the prescribed dose. Forty-one patients treated with high tangents were identified. The median age was 62. Most patients underwent sentinel LN biopsy (88%), of which 59% had macroscopic disease and 30% had micrometastatic disease. Four patients had no axillary staging. Most patients (76%) were treated with hypofractionated radiation. The median distance from the superior border of the anterior oblique field to the humeral head was 0.6 cm (range: 0–1.5 cm). The mean coverage of the level I and level II axilla was 88.7% and 40.0% respectively. Axillary level I coverage for distance from the humeral head < 1 cm was 95.1%, whereas distance > 1 cm was 76.4% (p = 0.017). This series demonstrates the feasibility of high tangents in the prone position, offering good coverage of level I LN, particularly with < 1 cm distance from the humeral head.
Objective Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques were compared in terms of their dosimetric quality, treatment efficiency, and delivery accuracy for hippocampal sparing prophylactic whole brain radiotherapy. Methods Ten previously treated patients were selected for this study. All plans were prescribed to deliver 30 Gy in 10 fractions to 90% of the target volume. RTOG 0933 recommendations were applied for treatment planning. Plans were compared based on the organ at risk (OAR) sparing, homogeneity and conformity indexes, monitor unit (MU), and beam on time (BOT). Delivery accuracy of the plans was also compared. Results VMAT plans had better homogeneity index and conformity index than IMRT plans. In terms of hippocampus sparing, VMAT plans were superior to other plans. Since brainstem, optic nerves, and chiasm were in the PTV, their doses were nearly equal to each other for both techniques. So, there were no statistical differences between techniques. Although both eyes were not in the PTV, there was no significant dose difference between techniques. However, due to the posterior gantry angles of IMRT plans, lens doses were lower in IMRT plans than those in VMAT plans. The VMAT technique had lower MU and BOT values than the IMRT technique. In terms of delivery accuracy, VMAT plans were superior than IMRT plans. Conclusion VMAT plans provide better target volume coverage, homogeneity, conformity, and hippocampus sparing when compared with IMRT plans. VMAT plans are also the best in terms of treatment efficiency since they require a much smaller number of MUs and thus a shorter treatment time than IMRT plans.
Objective We used quantitative analytics to assess the efficiency of the clinical workflow for radiation therapy delivery in children and adults focusing on our experience with volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI). Methods We retrospectively collected clinical and treatment specific data between June 2013 and November 2018 for 614 VMAT CSI sessions of 41 pediatric patients and 48 VMAT CSI sessions of 6 adult patients treated at two hospitals within the same academic institution. Descriptive statistics were generated and a multiple linear regression model was created to predict total radiation time (TRT) based on these predictors. Prolonged treatment sessions were filtered using the interquartile range outlier detection method for quality assurance review. Results The median pediatric TRT for all VMAT CSI treatment sessions was 21.07 min (interquartile range (IQR) 9.05). Pediatric patient height, fraction number (fractions 1-3 vs. fractions > 3), and number of isocenters were significant predictors for TRT (p < 0.01). In the case of adult patients, the median TRT for all VMAT CSI treatment sessions was significantly longer at 37.23 min (IQR 45.92,p < 0.05), even in subgroup analyses comparing plans adjusted for the same number of isocenters and IGRT modality in non-sedated patients. Only in pediatric patients did the median TRT decrease after the first three treatments. Qualitative causal factor analysis revealed plausible causes for prolonged TRT as anxiety, anticipatory nausea and vomiting, challenging setups, anesthesia tolerance, and delay to allow for physician online IGRT review of setup. Conclusions Simple descriptive statistics and regression modeling can be used to assess workflow efficiency and estimate radiation treatment times based on patient and technique-specific factors. We modeled VMAT CSI treatment delivery times at our pediatric and adult hospitals to set time expectations for IGRT and beam delivery. Workflow analytics can identify opportunities to minimize time inefficiencies and optimize coordination of care.
