Prioritising locations for radiotherapy equipment in Brazil: a cross-sectional, population-based study and development of a LINAC shortage index.

BACKGROUND: Similarly to several other upper-middle-income countries, there is a major shortfall in radiotherapy services for the treatment of cancer in Brazil. In this study, we developed the linear accelerator (LINAC) shortage index to assess the LINAC shortage and support the prioritisation of new LINAC distribution in Brazil. METHODS: This cross-sectional, population-based study used data from the National Cancer Institute 2020 Cancer estimates, the Ministry of Health 2019 radiotherapy census, the Minister of Health radiotherapy expansion programme progress reports, and the Fundação Oncocentro de São Paulo public database of the Cancer Hospital Registry of the State of São Paulo to calculate the LINAC shortage index. Data collected were number of new cancer cases in Brazil, number of LINACs per region and state, number of cancer cases treated with radiotherapy, patient state of residence, and radiotherapy treatment centre and location. National, regional, and state-level data were collected for analysis. LINAC numbers, cancer incidence, geographical distribution, and radiotherapy needs were estimated. A LINAC shortage index was calculated as a relative measure of LINAC demand compared with supply based on number of new cancer cases, number of patients requiring radiotherapy, and the number of LINCAS in the region or state. We then built a prioritisation framework using the LINAC shortage index, cancer incidence, and geographical factors. Finally, using patient-level public cancer registry data from the Fundação Oncocentro de São Paulo and Google maps, we estimated the geospatial distance travelled by patients with cancer from their state of residence to radiotherapy treatment in São Paulo from 2005-14. Non-parametric statistics were used for analysis. FINDINGS: Data were collected between Feb 2 and Dec 31, 2021. In 2020, there were 625 370 new cancer cases in Brazil and 252 LINAC machines. The number of LINACs was inadequate in all Brazilian regions, with a national LINAC shortage index of 221 (ie, 121% less than the required radiotherapy capacity). The LINAC shortage index was higher in the midwest (326), north (313), and northeast (237) regions, than the southeast (210) and south (192) regions. Four states (Tocantins, Acre, Amapá, and Roraima) in the north region were ranked first on the prioritisation rank due to no availability of LINACs. There was an association between LINAC shortage index and the number of patients who travelled to receive radiotherapy (p<0·0001). Patients living in the midwest (793 km), north (2835 km), and northeast (2415 km) regions travelled significantly longer average distances to receive radiotherapy treatment in São Paulo than patients living in the southeast or south regions (p=0·032). The reduced number of LINACs in these regions was associated with longer distance travelled (p=0·032). INTERPRETATION: There is substantial discordance between distribution of cancer cases and LINAC availability in Brazil. We developed a tool using the LINACs shortage index to help prioritise the development of radiotherapy infrastructure across Brazil; this approach might also be useful in other health systems. FUNDING: None.

Stereotactic body radiotherapy to treat breast cancer oligometastases: A systematic review with meta-analysis.

OBJECTIVES: Stereotactic ablative radiotherapy (SABR) has been reported to be an effective treatment for oligometastatic disease from different primary cancer sites. Here we assess the effectiveness and safety of SABR for oligometastatic breast cancer patients by performing a meta-analysis. METHODS: Following PRISMA and MOOSE guidelines, a systematic review and meta-analysis was performed. Eligible studies were identified on Medline, Embase, Cochrane Library, and annual meetings proceedings from 1990 to June 2021. A meta-regression analysis was performed to assess if there was a correlation between moderator variables and outcomes, and a p-value <0.05 was considered significant. RESULTS: Ten studies met criteria for inclusion, comprising 467 patients and 653 treated metastases. The 1- and 2-year local control rates were 97% (95% CI 95-99%), and 90% (95% CI 84-94%), respectively. Overall survival (OS) was 93% (95% CI 89-96%) at 1 year, 81% (95% CI 72-88%) at 2 years. The rate of any grade 2 or 3 toxicity was 4.1 % (95% CI 0.1-5%), and 0.7% (0-1%), respectively. In the meta-regression analysis, only prospective design (p = 0.001) and bone-only metastases (p = 0.01) were significantly associated with better OS. In the subgroup analysis, the OS at 2y were significantly different comparing HER2+, HR+/HER2(-) and triple negative breast cancer 100%, 86% and 32%, p = 0.001. For local control outcomes, hormone receptor status (p = 0.01) was significantly associated on meta-regression analysis. CONCLUSION: SABR for oligometastatic breast cancer is safe and associated with high rates of local control. Longer follow-up of existing data and ongoing prospective trials will help further define the role of this management strategy.

Gel and thermoluminescence dosimetry for dose verifications of a real anatomy simulated prostate conformal radiation treatment in the presence of metallic femoral prosthesis.

This study aims to verify the dose delivery of prostate radiotherapy treatments in an adult pelvic phantom with two metallic hip and femur prosthesis using a four-field box technique. The prostate planned target volume (PTV) tridimensional (3D) dose distribution was evaluated using gel dosimetry, and thermoluminescent dosimeters (TLD) were used for point-dose measurements outside it. Both results were compared to the treatment planning system (TPS) dose calculation without using heterogeneity corrections to evaluate the influence of the metal in the dose distribution. MAGIC-f gel dosimeter (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper with Formaldehyde) associated with magnetic resonance imaging was used. TLD were positioned at several points at the bone metal interface and the sacrum region. The comparison of the gel measured and the TPS calculated dose distributions were done using gamma analysis (3%/3 mm), and a pass rate of 93% was achieved. The TLD dose values at the bone-metal interface showed variations from the planned dose. However, at the sacrum region, where the beams did not intercept the prosthesis, there was a good agreement between TPS planning and TLD measurements. Our results show how the combination of 3D dosimetry and measurements at specific points in the phantom allowed a comprehensive view of the dose distribution and identified that care must also be paid to regions outside the PTV.

Long-Term Survival Rates and Prognostic Factors of Cervix Cancer Treated by Different Modalities.

OBJECTIVE: To assess the overall survival (OS) and prognostic factors in patients with cervix cancer treated by different modalities. MATERIAL AND METHODS: The authors studied a cohort of patients with cervix cancer International Federation of Gynecology and Obstetrics stage I-IVa treated in the last 15 years. Patients were treated with surgery followed by radiotherapy (S+RT), or surgery plus chemoradiation (S+CRT), or radiotherapy alone (RT), or chemoradiation alone (CRT). Univariate and multivariate analyses were conducted to identify significant prognostic factors (P<0.05). RESULTS: A total of 380 patients with cervix cancer were included. The treatment groups were S+CRT (37.5%), CRT (33%), RT (20%), and S+RT (9.5%). The median follow-up was 7.6 years, the OS in 5 and 10 years according to the treatment groups was 43.3%, and 17.3% for S+RT, 47.8% and 41.9% for S+CRT, 40.7% and 27.9% for CRT, and 29.1% and 19.4% for RT (P<0.0001). The stage IIb-IVa, age 60 years or older, RT, and 2DRT were significant factors in the univariate and multivariate analyses. In stage I-IIa, no significant difference was found among the treatment groups (P=0.907). In stage IIb-IVa, a significant difference was observed (P=0.0001). CRT versus RT had significance, and no difference between S+RT versus S+CRT, and S+CRT versus CRT was seen for stage IIb-IVa. CONCLUSIONS: In a long-term follow-up, no significant difference among the treatment modalities was found for early disease. For stage IIb-IVa, significant differences were observed, with RT having the worst survival, and CRT similar to S+CRT. These outcomes show that tumor and patients characteristics can be used to decide the best treatment option outside a clinical trial.

A new transmission methodology for quality assurance in radiotherapy based on radiochromic film measurements.

Despite individual quality assurance (QA) being recommended for complex techniques in radiotherapy (RT) treatment, the possibility of errors in dose delivery during therapeutic application has been verified. Therefore, it is fundamentally important to conduct in vivo QA during treatment. This work presents an in vivo transmission quality control methodology, using radiochromic film (RCF) coupled to the linear accelerator (linac) accessory holder. This QA methodology compares the dose distribution measured by the film in the linac accessory holder with the dose distribution expected by the treatment planning software. The calculated dose distribution is obtained in the coronal and central plane of a phantom with the same dimensions of the acrylic support used for positioning the film but in a source-to-detector distance (SDD) of 100 cm, as a result of transferring the IMRT plan in question with all the fields positioned with the gantry vertically, that is, perpendicular to the phantom. To validate this procedure, first of all a Monte Carlo simulation using PENELOPE code was done to evaluate the differences between the dose distributions measured by the film in a SDD of 56.8 cm and 100 cm. After that, several simple dose distribution tests were evaluated using the proposed methodology, and finally a study using IMRT treatments was done. In the Monte Carlo simulation, the mean percentage of points approved in the gamma function comparing the dose distribution acquired in the two SDDs were 99.92% ± 0.14%. In the simple dose distribution tests, the mean percentage of points approved in the gamma function were 99.85% ± 0.26% and the mean percentage differences in the normalization point doses were -1.41%. The transmission methodology was approved in 24 of 25 IMRT test irradiations. Based on these results, it can be concluded that the proposed methodology using RCFs can be applied for in vivo QA in RT treatments.