Statistical control of processes applied to geometric uncertainties for CTV expansion margins determination in prostate cancer patients treated with VMAT: a prospective study in 57 patients

Purpose To study the control graphs applicability for the geometric uncertainties of VMAT treatments in prostate cancer patients, and their use to verify the hypothesis of the data obtained randomness, to apply the margins of Van Herk expression. Material and methods During the first 5 days of treatment, and then once a week, a Kv CBCT was performed, compared with the simulation CT and adjusted the displacements, to determine the inter-fraction errors. Immediately after radiation therapy, another CBCT was performed (for intra-fraction errors). With these data, the X, R position control charts have been made. The patients, not maintained the deviations within the charts control limits, were called “anomalies”. Then, we compared the deviations and margins calculated with the van Herk expression for all patients and for those without anomalies. Results The margins determined show appreciable differences if there were calculated for the total set of patients or for the set of them without anomalies in the control charts. For the overall set of patients, the lateral, longitudinal, and vertical margins were 0.45 cm, 0.52 cm, 0.56 cm, while for the set of patients without anomalies were 0.29 cm, 0.35 cm, and 0.38 cm. Conclusions The use of control charts allows tracking geometric deviations both inter and intra-fraction, variability real-time control and to detect situations in which it can change for non-random reasons, and require immediate investigation. Maintaining geometric deviations in the control state decreases the margins needed to administer a high dose to CTV in a high percentage of cancer prostate patients (AU)

Statistical control of processes applied to geometric uncertainties for CTV expansion margins determination in prostate cancer patients treated with VMAT: a prospective study in 57 patients.

PURPOSE: To study the control graphs applicability for the geometric uncertainties of VMAT treatments in prostate cancer patients, and their use to verify the hypothesis of the data obtained randomness, to apply the margins of Van Herk expression. MATERIAL AND METHODS: During the first 5 days of treatment, and then once a week, a Kv CBCT was performed, compared with the simulation CT and adjusted the displacements, to determine the inter-fraction errors. Immediately after radiation therapy, another CBCT was performed (for intra-fraction errors). With these data, the X, R position control charts have been made. The patients, not maintained the deviations within the charts control limits, were called "anomalies". Then, we compared the deviations and margins calculated with the van Herk expression for all patients and for those without anomalies. RESULTS: The margins determined show appreciable differences if there were calculated for the total set of patients or for the set of them without anomalies in the control charts. For the overall set of patients, the lateral, longitudinal, and vertical margins were 0.45 cm, 0.52 cm, 0.56 cm, while for the set of patients without anomalies were 0.29 cm, 0.35 cm, and 0.38 cm. CONCLUSIONS: The use of control charts allows tracking geometric deviations both inter and intra-fraction, variability real-time control and to detect situations in which it can change for non-random reasons, and require immediate investigation. Maintaining geometric deviations in the control state decreases the margins needed to administer a high dose to CTV in a high percentage of cancer prostate patients.

Effects of prenatal stress on anxiety- and depressive-like behaviours are sex-specific in prepubertal rats.

The foetal brain is highly susceptible to stress in late pregnancy, with lifelong effects of stress on physiology and behaviour. The present study aimed to determine the physiological and behavioural effects of prenatal stress during the prepubertal period of female and male rats. We subjected pregnant Sprague-Dawley rats to a restraint stress protocol from gestational day 14 to 21, a critical period for foetal brain susceptibility to stress effects. Male and female offspring were subsequently assessed at postnatal day 24 for anxiety- and depressive-like behaviours, as well as spontaneous social interaction. We also assessed maternal behaviours and 2 stress markers: basal vs acute-evoked stress levels of serum corticosterone and body weight gain. Prenatal stress did not affect the maternal behaviour, whereas both female and male offspring had higher body weight gain. On the other hand, lower levels of corticosterone after acute stress stimulation, as well as anxiety- and depressive-like behaviours, were only evident in stressed males compared to control males. These results suggest that prenatal stress induced sex-specific effects on hypothalamic-pituitary-adrenal (HPA) axis activity and on behaviour during prepuberty. The HPA axis of prenatally stressed male rats was less active compared to control males, and they were also more anxious and experienced depressive-like behaviours. These results are useful with respect to studying the neurobiological basis of childhood depression at a preclinical level.