Dosimetric evaluation of manually and inversely optimized treatment planning for high dose rate brachytherapy of cervical cancer.

BACKGROUND: To compare five inverse treatment planning methods with the conventional manually optimized planning approach for brachytherapy of cervical cancer with respect to dosimetric parameters. MATERIAL AND METHODS: Eighteen cervical cancer patients treated with magnetic resonance imaging (MRI)-guided high dose rate (HDR) brachytherapy were included in this study. Six plans were created for each of the 4 HDR brachytherapy fractions for each patient: 1 manually optimized and 5 inversely planned. Three of these were based on inverse planning simulated annealing (IPSA) with and without extra constraints on maximum doses of the target volume, and different constraints on doses to the organs at risk (OARs). In addition there were two plans based on dose to target surface points. The resulting dose-volume histograms were analyzed and compared from the dosimetric point of view by quantifying specific dosimetric parameters, such as clinical target volume (CTV) D90, CTV D100, conformal index (COIN), and D2cm3 for rectum, bladder and the sigmoid colon. RESULTS: Manual optimization led to a mean target coverage of 78.3% compared to 87.5%, 91.7% and 82.5% with the three IPSA approaches (p < 0.001). Similar COIN values for manual and inverse optimization were found. The manual optimization led to better results with respect to the dose to the OARs expressed as D2cm3. Overall, the best results were obtained with manual optimization and IPSA plans with volumetric constraints including maximum doses to the target volume. CONCLUSIONS: Dosimetric evaluation of manual and inverse optimization approaches is indicating the potential of IPSA for brachytherapy of cervical cancer. IPSA with constraints of maximum doses to the target volume is closer related to manual optimization than plans with constraints only to minimum dose to the target volume and maximum doses to OARs. IPSA plans with proper constraints performed better than those based on dose to target surface points and manually optimized plans.

Adaptive brachytherapy of cervical cancer, comparison of conventional point A and CT based individual treatment planning.

BACKGROUND: Locally advanced cervical cancer is commonly treated with external radiation therapy combined with local brachytherapy. The brachytherapy is traditionally given based on standard dose planning with prescription of dose to point A. Dosimetric aspects when changing from former standard treatment to individualized treatment plans based on computed tomography (CT) images are here investigated. MATERIAL AND METHODS: Brachytherapy data from 19 patients with a total of 72 individual treatment fractions were retrospectively reviewed. Standard library plans were analyzed with respect to doses to organs at risk (OARs), and the result was compared to corresponding delivered individualized plans. The theoretical potential of further optimization based on prescription to target volumes was investigated. The treatments were performed with a Fletcher applicator. RESULTS: For standard treatment planning, the tolerance dose limits were exceeded in the bladder, rectum and sigmoid in 26%, 4% and 15% of the plans, respectively. This was observed most often for the smallest target volumes. The individualized planning of the delivered treatment gave the possibility of controlling the dose to critical organs to below certain limits. The dose was still prescribed to point A. An increase in target dose coverage was achieved when additional individual optimization was performed, while still keeping the dose to the OARs below predefined limits. Relatively low average target coverage, especially for the largest volumes was however seen. CONCLUSION: The individualized delivered treatment plans ensured that doses to OARs were within acceptable limits. This was not the case in 42% of the corresponding standard plans. Further optimized treatment plans were found to give an overall better dose coverage. In lack of MR capacity, it may be favorable to use CT for planning due to possible protection of OARs. The CT based target volumes were, however, not equivalent to the volumes described in magnetic resonance imaging (MRI) based recommendations. Prescription and assessment of dose, when introducing such target volumes, should be evaluated and preferably compared to well known treatment regimens.

Assessment of late urinary, bowel and sexual function after dose escalation from 70 to 76 Gy using image-guided radiotherapy in curative treatment of prostate cancer.

OBJECTIVE: The aim of this study was to evaluate the late urinary, bowel and sexual function among men with localized or locally advanced prostate cancer treated with curative radiotherapy after the introduction of image-guided radiotherapy to 76 Gy using the Swedish BeamCath® technique. MATERIAL AND METHODS: All patients treated with curative radiotherapy during 2003-2006 were invited to participate in this retrospective study. In total, 87% (158/181) participated in the study. The median observation time was 35 months. Comparisons were made between the standard 70 Gy (n = 73) and the 76 Gy (n = 85) treatment groups. Assessments of late urinary, bowel and sexual function were questionnaire based, and included function items in the Expanded Prostate Cancer Index Composite. RESULTS: Most late urinary and bowel symptoms were reported to occur seldom or never in the majority of men, while late sexual toxicity was reported in a large proportion (66%) of men. Seven men (4%) used diapers. Only 25% (n = 40) reported having an erection firm enough for intercourse. None of the reported urinary or sexual function symptoms differed between the treatment groups. Rectal urgency at least once daily was a more frequent symptom in the 70 Gy group than the 76 Gy group (28% vs 9%, p = 0.006). Painful bowel movements were a more common symptom in the 70 Gy group (11% vs 1%, p = 0.01). CONCLUSION: Dose escalation up to 76 Gy using the BeamCath technique was not associated with more late toxicities than the standard 70 Gy dose.