Effect of bladder distension on doses to organs at risk in Pulsed-Dose-Rate 3D image-guided adaptive brachytherapy for locally advanced cervical cancer.

To evaluate the impact of bladder distension on doses to organs at risk in patients treated with 3D image-guided adaptive pulsed-dose-rate (PDR) brachytherapy (BT) for locally advanced cervical cancer. Twenty-two patients who had previously been treated by external beam radiation therapy (EBRT), underwent BT treatment planning to a pelvic MRI (or a CT scan in case of contraindication) after their bladder was filled with 100 cc of physiological saline (full bladder). This was immediately followed by a CT scan after emptying of the bladder. A fusion of these two examinations was conducted, and the dosimetry was duplicated for the study with an empty bladder. Equieffective doses of 2 Gy per fraction from EBRT and BT of bladder/rectum/sigmoid colon/small bowel were compared. A full bladder condition was found to be non-inferior in terms of the bladder D2cc (a difference of -0.9 Gy; 97.5% CI [-∞; 2.6]), and it resulted in a reduction in the bladder D0.1cc (p = 0.038). Bladder expansion resulted in a significant reduction of maximum doses received by the small bowel, both in terms of the D0.1cc (51.2 Gy vs. 63.4 Gy, p < 0.001) and the D2cc (48.5 Gy vs. 53.6 Gy, p < 0.001). A negative correlation was seen between the difference in the small bowel D2cc and the body mass index; (r = -0.55; p = 0.008). No differences were noted in regard to doses to the rectum and sigmoid colon. Bladder distension with 100 cc of physiological saline can reduce maximum doses received by the small bowel without the alteration of the doses received by the other organs at risk during a 3D image-guided adaptive PDR BT for locally advanced cervical cancer. However, the maintenance of a predefined bladder volume is difficult to achieve with PDR BT, whereas it could be easily managed before each session in case of high-dose-rate BT.

Nesseler JP ，Charra-Brunaud C ，Salleron J ，Py JF ，Huertas A ，Meknaci E ，Courrech F ，Peiffert D ，Renard-Oldrini S ... -  《-》

Long term experience with 3D image guided brachytherapy and clinical outcome in cervical cancer patients.

To report our 10years' experience and learning curve of the treatment of cervical cancer patients with chemo radiotherapy and MRI (or CT in 9 selected patients) guided brachytherapy using pulsed dose rate (PDR) brachytherapy (BT). Hundred and seventy consecutive patients with cervical cancer FIGO stage IB-IVB (without metastases beyond the para-aortic nodal region) were treated in our institute between 2002 and 2012. Patients received external beam radiotherapy (nodal boost to the lymph nodes positive at diagnosis)±chemotherapy followed by a pulsed or low dose rate brachytherapy boost. MRI (or CT) images were taken with the applicator in situ. The first 16 patients were treated according to X-ray-based plans, optimized on MRI. High-risk CTV, intermediate-risk CTV, bladder, rectum and sigmoid were retrospectively contoured according to the GEC-ESTRO recommendations. In all other patients, treatment plans were optimized after delineation of the target volumes and organs at risk at MRI (or CT). Doses were converted to the equivalent dose in 2Gy (EQD2) by applying the linear quadratic model. The median age of the patients was 55years (range 16-88). 41% had stage III or IV disease. Of the 170 patients, 91 patients had on imaging metastatic lymph nodes at diagnosis (62 patients pelvic lymph node involvement and 29 para-aortic). In 27 (16%) patients the intracavitary technique was combined with interstitial brachytherapy. The mean D90 and D100 for the high-risk CTV were 84.8±8.36Gy and 67.5±6.29Gy for the entire patient group. Mean D90 and D100 values for the IR CTV were 68.7±5.5Gy and 56.5±6.25Gy. There was an important learning curve between both patient groups, with an increase in mean D90 of 75.8Gy for the first 16 patients compared to 85.8Gy for the second group. At the same time, the mean dose to 2cm3 of bladder and sigmoid decreased from 86.1Gy to 82.7Gy and from 70Gy to 61.7Gy, respectively. At a median follow-up of 37months (range 2-136months), local control rate for all patients was 96%, the regional control (pelvic and para-aortic) rate 81% and crude disease free survival rate 55%. The overall survival at 5years is 65%. The higher dose to the target volume resulted in an increase in local control from 88% in the first 16 patients compared to 97% in the second patient group. Regarding late toxicity, 21 patients (12%) presented grade 3-4 late morbidity. Rectal, urinary, sigmoid and vaginal morbidity was 5%, 6%, 2% and 5%, respectively. A correlation between rectal D2cm3 >65Gy and grade >3 late morbidity was found (p=0.006). Although the majority of the patients presented with locally advanced carcinoma, excellent local and regional control rates were achieved. Rectal, urinary, sigmoid and vaginal grade 3-4 morbidity was 5%, 6%, 2% and 5%, respectively. A correlation between rectal D2cm3 >65Gy and grade >3 late morbidity was found (p=0.006).

Ribeiro I ，Janssen H ，De Brabandere M ，Nulens A ，De Bal D ，Vergote I ，Van Limbergen E ... -  《-》

Image-based 3D treatment planning for vaginal cylinder brachytherapy: dosimetric effects of bladder filling on organs at risk.

To investigate the dosimetric effects of bladder filling on organs at risk (OARs) using three-dimensional image-based treatment planning for vaginal cylinder brachytherapy. Twelve patients with endometrial or cervical cancer underwent postoperative high-dose rate vaginal cylinder brachytherapy. For three-dimensional planning, patients were simulated by computed tomography with an indwelling catheter in place (empty bladder) and with 180 mL of sterile water instilled into the bladder (full bladder). The bladder, rectum, sigmoid, and small bowel (OARs) were contoured, and a prescription dose was generated for 10 to 35 Gy in 2 to 5 fractions at the surface or at 5 mm depth. For each OAR, the volume dose was defined by use of two different criteria: the minimum dose value in a 2.0-cc volume receiving the highest dose (D(2cc)) and the dose received by 50% of the OAR volume (D(50%)). International Commission on Radiation Units & Measurements (ICRU) bladder and rectum point doses were calculated for comparison. The cylinder-to-bowel distance was measured using the shortest distance from the cylinder apex to the contoured sigmoid or small bowel. Statistical analyses were performed with paired t tests. Mean bladder and rectum D(2cc) values were lower than their respective ICRU doses. However, differences between D(2cc) and ICRU doses were small. Empty vs. full bladder did not significantly affect the mean cylinder-to-bowel distance (0.72 vs. 0.92 cm, p = 0.08). In contrast, bladder distention had appreciable effects on bladder and small bowel volume dosimetry. With a full bladder, the mean small bowel D(2cc) significantly decreased from 677 to 408 cGy (p = 0.004); the mean bladder D(2cc) did not increase significantly (1,179 cGy vs. 1,246 cGy, p = 0.11). Bladder distention decreased the mean D(50%) for both the bladder (441 vs. 279 cGy, p = 0.001) and the small bowel (168 vs. 132 cGy, p = 0.001). Rectum and sigmoid volume doses were not affected by bladder filling. In high-dose rate vaginal cylinder brachytherapy, treatment with a distended bladder preferentially reduces high dose to the small bowel around the vaginal cuff without a significant change in dose to the bladder, rectum, or sigmoid.

Hung J ，Shen S ，De Los Santos JF ，Kim RY ... -  《-》

Bladder distension improves the dosimetry of organs at risk during intracavitary cervical high-dose-rate brachytherapy.

To evaluate dose-volume histograms (DVHs) and dose-surface histograms (DSHs) to analyze bladder distension during cervical brachytherapy. Twenty brachytherapy fractions from five cervical cancer patients were selected. For each fraction, empty and full (200cc of contrasted saline) bladder simulation CT scans existed, one of which was used to plan treatment. An alternative plan was then created with the unused scan. DVH for each fraction was generated for the bladder, rectum, sigmoid colon, and small bowel. Mean DVH dose, D0.1cc, and D2cc were calculated for each organ at risk. Plans were then exported to a MATLAB-based program to generate a DSH. Full bladder plans showed no difference in bladder D2cc or D0.1cc compared with empty bladder plans; however, bladder mean DVH dose and DSH dose were both significantly reduced. Full bladder plans showed a significant reduction in small intestine D2cc from 2.81 Gy to 1.83 Gy and reduction in D0.1cc from 4.07 Gy to 2.57 Gy (p < 0.05); similarly, sigmoid D2cc was significantly reduced from 4.24 Gy to 3.87 Gy (p < 0.05) and D0.1cc was reduced from 6.12 Gy to 5.61 Gy (p < 0.05) in full bladder plans. Both small intestine and sigmoid also showed reduced mean DVH and DSH dose in full bladder plans. The rectum showed no significant difference in D2cc, D0.1cc, mean DVH, or DSH dose between plans. Bladder distension during cervical brachytherapy significantly reduced dose in all DVH and DSH parameters for sigmoid and small intestine with no change in bladder parameters. It reduces dose to organ at risk, but the correlation to toxicity requires further investigation.

Harmon G ，Chinsky B ，Surucu M ，Harkenrider M ，Small W Jr ... -  《-》

Radiobiological optimization comparison between pulse-dose-rate and high-dose-rate brachytherapy in patients with locally advanced cervical cancer.

Only scarce data are available on the possibility to include radiobiological optimization as part of the dosimetric process in cervical cancer treated with brachytherapy (BT). We compared dosimetric outcomes of pulse-dose-rate (PDR) and high-dose-rate (HDR)-BT, according to linear-quadratic model. Three-dimensional dosimetric data of 10 consecutive patients with cervical cancer undergoing intracavitary image-guided adaptive PDR-BT after external beam radiation therapy were examined. A new HDR plan was generated for each patient using the same method as for the PDR plan. The procedure was intended to achieve the same D90 high-risk clinical target volume with HDR as with PDR planning after conversion into dose equivalent per 2 Gy fractions (EQD2) following linear-quadratic model. Plans were compared for dosimetric variables. As per study's methodology, the D90 high-risk clinical target volume was strictly identical between PDR and HDR plans: 91.0 Gy (interquartile: 86.0-94.6 Gy). The median D98 intermediate-risk clinical target volume was 62.9 GyEQD2 with HDR vs. 65.0 GyEQD2 with PDR (p < 0.001). The median bladder D2cc was 65.6 GyEQD2 with HDR, vs. 62 GyEQD2 with PDR (p = 0.004). Doses to the rectum, sigmoid, and small bowel were higher with HDR plans with a median D2cc of 55.6 GyEQD2 (vs. 55.1 GyEQD2, p = 0.027), 67.2 GyEQD2 (vs. S 64.7 GyEQD2, p = 0.002), and 69.4 GyEQD2 (vs. 66.8 GyEQD2, p = 0.014), respectively. For organs at risk (OARs), the effect of radiobiological weighting depended on the dose delivered. When OARs BT contribution to D2cc doses was <20 GyEQD2, both BT modalities were equivalent. OARs EQD2 doses were all higher with HDR when BT contribution to D2cc was ≥20 GyEQD2. Both BT modalities provided satisfactory target volume coverage with a slightly higher value with the HDR technique for OARs D2cc while intermediate-risk clinical target volume received higher dose in the PDR plan. The radiobiological benefit of PDR over HDR was predominant when BT contribution dose to OARs was >20 Gy.

Annede P ，Dumas I ，Schernberg A ，Tailleur A ，Fumagalli I ，Bockel S ，Mignot F ，Kissel M ，Deutsch E ，Haie-Meder C ，Chargari C ... -  《-》