External Beam Radiotherapy in Western Africa: 1969-2019.

AIMS: We describe the absolute and per capita numbers of megavoltage radiotherapy machines (MVMs) in Western Africa from 1969 to 2019. MATERIALS AND METHODS: Western Africa was defined in accordance with the United Nations' delineation and inclusive of 16 countries. A literature search for publications detailing the number of cobalt-60 machines (COs) and linear accelerators (LINACs) in radiotherapy centres was carried out. Population data from the World Bank Group and crude cancer rates from the International Agency for Research on Cancer were used to calculate ratios of million persons per MVM and MVMs per 1000 cancer cases. RESULTS: The numbers of MVMs in Western Africa in 1969, 1979, 1989, 1999 and 2009 were zero, two, three, six and nine, respectively. In 2019 there were 22 MVMs distributed across Ghana (five), Côte d'Ivoire (two), Mali (one), Mauritania (two), Nigeria (nine) and Senegal (three). Nine countries (56.3%) had no history of external beam radiotherapy (EBRT). The largest increase in absolute EBRT capacity occurred from 2017 to 2019, during which 13 MVMs were commissioned. The largest decrease in EBRT capacity occurred from 2015 to 2017, during which four LINACs and three COs were rendered non-operational. The ratio of million persons per MVM improved from 67.0 in 1979 to 17.8 in 2019. As of 2019, there was 0.09 MVM per 1000 cancer cases. CONCLUSIONS: Western African nations have experienced an increase in the absolute number of MVMs and per capita radiotherapy capacity during the last 50 years, especially in the last decade. As non-functional LINACs contributed to a temporary decline in the EBRT infrastructure, dual use of CO/LINAC technologies may act to promote the availability of EBRT treatment in centres with capacity for multiple MVMs.

Deformable image registration for dose mapping between external beam radiotherapy and brachytherapy images of cervical cancer.

For locally advanced cervical cancer (LACC), anatomy correspondence with and without BT applicator needs to be quantified to merge the delivered doses of external beam radiation therapy (EBRT) and brachytherapy (BT). This study proposed and evaluated different deformable image registration (DIR) methods for this application. Twenty patients who underwent EBRT and BT for LACC were retrospectively analyzed. Each patient had a pre-BT CT at EBRT boost (without applicator) and a CT and MRI at BT (with applicator). The evaluated DIR methods were the diffeomorphic Demons, commercial intensity and hybrid methods, and three different biomechanical models. The biomechanical models considered different boundary conditions (BCs). The impact of the BT devices insertion on the anatomy was quantified. DIR method performances were quantified using geometric criteria between the original and deformed contours. The BT dose was deformed toward the pre-CT BT by each DIR method. The impact of boundary conditions to drive the biomechanical model was evaluated based on the deformation vector field and dose differences. The GEC-ESTRO guideline dose indices were reported. Large organ displacements, deformations, and volume variations were observed between the pre-BT and BT anatomies. Rigid registration and intensity-based DIR resulted in poor geometric accuracy with mean Dice similarity coefficient (DSC) inferior to 0.57, 0.63, 0.42, 0.32, and 0.43 for the rectum, bladder, vagina, cervix and uterus, respectively. Biomechanical models provided a mean DSC of 0.96 for all the organs. By considering the cervix-uterus as one single structure, biomechanical models provided a mean DSC of 0.88 and 0.94 for the cervix and uterus, respectively. The deformed doses were represented for each DIR method. Caution should be used when performing DIR for this application as standard techniques may have unacceptable results. The biomechanical model with the cervix-uterus as one structure provided the most realistic deformations to propagate the BT dose toward the EBRT boost anatomy.

Time Dependence of Radiation-induced Hypothalamic-Pituitary Axis Dysfunction in Adults Treated for Non-pituitary, Intracranial Neoplasms.

AIMS: Hypothalamic-pituitary axis (HPA) dysfunction is a sequela of cranial radiotherapy. The purpose of this study was to use endocrine data from existing publications to characterise the baseline endocrine status, the effects of radiotherapy on the HPA during the first follow-up year and the time dependence of radiation-induced HPA dysfunction in patients treated with radiotherapy for non-pituitary intracranial neoplasms. MATERIALS AND METHODS: A systematic search of databases was carried out for articles that reported the results of endocrine testing for patients aged 16 years and older who were treated with neurosurgery for non-pituitary intracranial neoplasms or radiotherapy for nasopharyngeal neoplasms. To analyse the radiotherapy-related changes in hormone levels over time, long-term prospective endocrine data from nasopharyngeal studies were normalised to baseline hormone data and fitted to an exponential decay model. This process was repeated with normalisation to year 1 hormone data. RESULTS: Eight unique articles met eligibility criteria. HPA dysfunction occurred in 21.6-64.7% of patients who were assessed for endocrinopathies following neurosurgery. Studies on the early effects of radiotherapy on nasopharyngeal patients showed statistically significant changes in growth hormone, luteinizing hormone and follicle stimulating hormone levels during the first year of follow-up. Time dependence modelling showed that normalisation to year 1 hormone levels yield exponential equations with stronger measures of goodness of fit. CONCLUSION: HPA dysfunction in patients treated for non-pituitary intracranial neoplasms is probably a result of both neurosurgery and radiotherapy treatments. Although statistically significant endocrine changes can occur during this first year of follow-up, those documented at year 1 may be more predictive of subsequent HPA dysfunction.