Image guidance procedures in radiotherapy for prostate cancer and the influence of body mass index

Abstract

Purpose: To investigate possible optimisation of the image guidance procedure for the prostate cancer patients with respect to imaging frequency and patient body mass index (BMI).Methods: The 6,085 setup correction shifts and BMI for 216 prostate cancer patients treated on tomotherapy units in two centres were analysed. Margins needed to account for inter-fraction target motion with daily only automatic correction and with automatic and manual corrections during one, three or five first fractions as a reference for further treatment without imaging were calculated.Results: The planning target volume margin calculated for the daily automatic correction only scheme was significantly lower than the margins calculated for the image guidance limited to a few initial fractions. Manual corrections after automatic fusion were more important for patients with higher BMI. On average, the patients with normal BMI had manual correction shift of 0?7 mm in anterioposterior direction, while overweight and obese patients required, correspondingly, the shifts of 1?3 and 1?4 mm. Conclusion:Overweight and obese patients require daily imaging with time saving available by performing automatic kV/MV computed tomography registration only. The patients with normal BMI may be treated with imaging guidance during a few initial treatment fractions.

Target margins in radiotherapy of prostate cancer

“…For example, one study demonstrated benefits to daily imaging for obese and overweight patients (BMI .25), whereas the patients with normal BMI could be treated with imaging guidance restricted to the first few initial treatment fractions with calculated patientspecific set-up corrections applied thereafter. 79 Schulze et al 80 evaluated the possible effect of online daily replanning and estimated better organ-at-risk sparing: the rectum and bladder doses were lower by 11% and 14%, respectively. With CBCT pretreatment imaging, matching based on bony anatomy, soft tissue and online reoptimization was evaluated using the 10-and 5-mm PTV margins.…”

Porównanie dwóch metod weryfikacji geometrycznej podczas radioterapii raka prostaty

“…Podstawowym celem weryfikacji obrazowej jest ocena zgodności pomiędzy aktualną anatomią pacjenta (przed podaniem dawki frakcyjnej) z anatomią pacjenta zobrazowaną przed rozpoczęciem kursu radioterapii, dla której został utworzony plan leczenia, oraz redukcja wykrytych w trakcie powyższej oceny rozbieżności poprzez korekcję ułożenia pacjenta [5][6][7][8][9].…”

“…Dlatego też korekcja ułożenia pacjenta poddanego radioterapii raka stercza na podstawie struktur kostnych obarczona jest błędem [22]. Błąd ten jest zredukowany w przypadku korekcji ułożenia przeprowadzonego na podstawie dopasowania tkanek miękkich (CBCT) [7]. Celem niniejszej pracy było określenie błędu, jakim obarczona jest metoda 2D-kV w porównaniu z metodą CBCT.…”

“…[24] dla przesunięć wewnątrzfrakcyjnych oraz przez Piotrowskiego i wsp. [25] dla przesunięć międzyfrakcyjnych.…”

In regard to “Setup error analysis in helical tomotherapy based image-guided radiation therapy treatments”

“…have shown that daily IG is needed for obese patients while the patients with body mass index <30 will benefit from IG procedures performed only during a few first treatment fractions. [ 4 ] A limited number of pretreatment IG sessions presents as an interesting compromise that allows for savings on labor, time, and imaging dose while taking into account specific information about target motion with the construction of personalized margins for the subsequent fractions without IG. [ 5 ]…”