The equivalent dose contribution from high-dose-rate brachytherapy to positive pelvic lymph nodes in locally advanced cervical cancer.

Definitive radiation therapy for locally advanced cervical cancer involves external beam radiation therapy (EBRT) and high-dose-rate (HDR) brachytherapy. There remains controversy and practice pattern variation regarding the optimal radiation dose to metastatic pelvic lymph nodes (LNs). This study investigates the contribution of the pelvic LN dose from HDR brachytherapy. For 17 patients with 36 positive pelvic LNs, each LN was contoured on a computed tomography (CT) plan for EBRT and on brachytherapy planning CTs using positron emission tomographic images obtained before chemoradiation. The mean delivered dose from each plan was recorded, and an equivalent dose in 2-Gy fractions (EQD2) was calculated. A Student's t test was performed to determine if the mean delivered dose is significantly different from the mean prescribed dose and EQD2. The average prescribed dose from the total EBRT was 54.09 Gy. The average prescribed HDR dose to International Commission on Radiation Units point A was 26.81 Gy. The average doses delivered to the involved LNs from EBRT and brachytherapy were 54.25 and 4.31 Gy, respectively, with the corresponding EQD2 of 53.45 and 4.00 Gy. There was no statistically significant difference (p < 0.05) between the mean delivered and the prescribed doses for EBRT and between the delivered dose and the EQD2 for EBRT and brachytherapy. Our study shows that the HDR contribution is 7% (4.00 Gy) of the total EQD2 (57.45 Gy). The HDR contribution should be accounted for when prescribing the EBRT boost dose to pelvic LNs for the optimal therapeutic dose.

Lee YC ，Rash DL ，Stern RL ，Mayadev JS ... -  《-》

Assessment of radiation doses to the para-aortic, pelvic, and inguinal lymph nodes delivered by image-guided adaptive brachytherapy in locally advanced cervical cancer.

This study evaluated the dose delivered to lymph nodes (LNs) by brachytherapy (BT) and the effect of BT image-guided optimization on the LN dose. Twenty-five patients with locally advanced cervical cancer were retrospectively analyzed, 16 patients of them had LN involvement. The patients received whole pelvis intensity-modulated radiation therapy (45-50 Gy/25-30 fx) to whole pelvis and two fractions of MRI pulsed-dose-rate BT. The delineated LN groups were para-aortic, inguinal, common iliac (CI), external iliac, internal iliac, obturator, and presacral. For each LN group, D98%, D50%, and D2% (the dose that covers 98%, 50%, and 2% of the volume, respectively) were evaluated for optimized and standard BT plans. The correlation between total reference air kerma (TRAK) and D50% of the LN groups was evaluated. BT contributed considerable dose (mean D50% was 3.8-6.2 Gy equivalent total dose in 2-Gy fractions) to the pelvic LN (external iliac, internal iliac, obturator, and presacral) in optimized plans, whereas less-dose contribution to CI, para-aortic, and inguinal (mean D50% was 0.5-1.9 Gy equivalent total dose in 2-Gy fractions) was observed. Optimized plans delivered less dose to the LNs as compared with standard plans, although differences only amounted to a mean of 0.2-0.9 Gy (D50%). TRAK showed a significant correlation with LN D50% for all LN groups except CI, although only 19-38% of the dose variation could be explained by the TRAK. BT contributes considerable dose to pelvic LNs and should be considered in the evaluation of total LN doses.

Mohamed SM ，Aagaard T ，Fokdal LU ，Pedersen EM ，Lindegaard JC ，Tanderup K ... -  《-》

Does external beam radiation boost to pelvic lymph nodes improve outcomes in patients with locally advanced cervical cancer?

Wujanto C ，Choo BA ，Tan D ，Ilancheran A ，Ng J ，Low JJH ，Shen L ，Tang J ，Koh V ... -  《BMC CANCER》

CT based 3-dimensional treatment planning of intracavitary brachytherapy for cancer of the cervix: comparison between dose-volume histograms and ICRU point doses to the rectum and bladder.

Hashim N ，Jamalludin Z ，Ung NM ，Ho GF ，Malik RA ，Phua VC ... -  《-》

Is SBRT Boost Feasible for PET Positive Lymph Nodes for Cervical Cancer? Evaluation using Tumor Control Probability and QUANTEC Criteria.

This study aimed to examine the feasibility of stereotactic body radiation therapy (SBRT) as an external beam radiation therapy boost to positron emission tomography (PET) positive lymph nodes (LN) in patients with cervical cancer and to evaluate overall tumor control probability (TCP) increase. Ten patients with cervical cancer and PET positive LN metastasis who received external beam radiation therapy (45 Gy), followed by a 3-dimensional conformal radiation therapy boost (5.4-9 Gy) and tandem-and-ovoid high-dose-rate brachytherapy (16-30 Gy) were retrospectively enrolled in this study. SBRT plans were generated using 21 Gy, 24 Gy, or 30 Gy as a replacement for 3-dimensional conformal radiation therapy boost. The 2 Gy-per-fraction equivalent dose maps were made using an α/β value of 10 for PET positive LNs and 3 for organs at risk (OARs). TCP values were calculated using a logistic TCP model, where 2 input parameters (D50 and Gamma50 = 2) were modeled by 2 clinical outcomes: our institution and the literature. OAR sparing was evaluated using Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) dose limits. Thirty percent of 10 patients receiving conventional boost experienced recurrence. The TCP of the SBRT schemes was 88% ± 7% (97% ± 2%; 21 Gy), 96% ± 1% (99% ± 0%; 24 Gy), and 99% ± 1% (100% ± 0%; 30 Gy), and the conventional LN-boost TCP value was 25% ± 11% (58% ± 15%) when TCP input parameters were based on published clinical outcome data for LN SBRT treatments (institutional outcome data). The tumor coverage doses (D90) of the SBRT boost plans were on average 32.34 Gyαβ=10 (21 Gy), 37.78 Gyαβ=10 (24 Gy), and 55.54Gyαβ=10 (30 Gy) higher than the conventional LN boost plan. The QUANTEC OAR dose constraints were met for the bladder, rectum, and bowel in all cases for the SBRT LN 21 Gy group, and in 90% and 70% of cases in the SBRT LN 24 Gy and SBRT LN 30 Gy groups, respectively. An SBRT boost dose of 30 Gy can be delivered without compromising QUANTEC OAR limits. The use of SBRT increases TCP values, regardless of the input parameters.

Snyder JE ，Willett AB ，Sun W ，Kim Y ... -  《-》