Cervical tumor control evaluated with ICRU 38 reference volumes and integrated reference air kerma

Excess dose-related parameters (Vex, Rex, and iRex): novel predictors and late toxicity correlations in cervical cancer image-guided adaptive brachytherapy

Purpose

In this paper, excess dose is originally proposed to represent the dose outside the target volume that encompass only organs at risk (OARs), not the whole dose volume of isodose surface volume (ISV). By means of spatial consideration, excess dose-related parameters would also compensate inconsistent applicator positions and OARs motion, which may deviate the identical dose small-volume assumption of D_2cc. Late toxicity correlations of these parameters were investigated.

Material and methods

A retrospective review was performed on cervical cancer high-dose-rate image-guided adaptive brachytherapy (HDR-IGABT). From ISVs of 60 to 100 Gy EQD₂ (a/β = 3), excess dose-related parameters were derived as following: toxicity negligible volume (Vneg = V₆₀ of toxicity negligible organs; high-risk clinical target volume – HR-CTV, uterus, and vagina), excess dose volume (Vex = ISV – Vneg), Vneg normalized parameters of excess dose volume ratio (Rex = Vex/Vneg), and indirect excess dose volume ratio (iRex = ISV/Vneg). Relationships between toxicity and these parameters were analyzed using a mean difference and a probit analysis method. Net reclassification indices (NRIs) were used to compare iRex60 and D_2cc gastrointestinal (GI) toxicity prediction.

Results

From 143 cases with an incidence of 34.9% and 10.5% of 3-year grade 2-4 GI and genitourinary (GU) toxicity, respectively, comparisons of means showed significant difference between grade 0-1 and 2-4 toxicities for late GI toxicity for all parameters, except ISV. There was a dose-response relationship with toxicity for each parameter across the range of 60-100 Gy EQD₂. ED₁₀ of iRex60 and iRex70 were 2.1 and 1.2, respectively. By comparing iRex60 and D_2cc, additive and absolute NRIs were +6.45 and +7.69%, respectively. The reclassification significantly occurred in range of 65-75 Gy of rectum D_2cc.

Conclusions

Excess dose-related parameters, including Vex, Rex, and iRex, showed significant mean differences and parameter-toxicity relationships for late GI but not for GU toxicities. Positive NRIs suggest iRex60 utilization for spatial control of dose expansion, in addition to high-dose control with OAR small volumes. Further investigations are needed to define the optimum use of these predictors.

Dosimetric comparison of graphical optimization and inverse planning simulated annealing for brachytherapy of cervical cancer

Purpose

Graphical optimization (GO) and inverse planning simulated annealing (IPSA) are the main treatment planning optimization techniques used in patients undergoing 3D brachytherapy treatment. This study aims to compare the dosimetric difference of plans optimized by GO and IPSA in cervical cancer brachytherapy.

Material and methods

21 cervical cancer patients data sets consisted of computed tomography (CT) and magnetic resonance imaging (MRI), acquired with the Fletcher applicator in situ were transferred to the Oncentra brachytherapy planning system. For each patient, the treatment plan was initially optimized with GO to reach a maximal D₉₀ tumor dose (6 Gy/fraction, 5 fractions), while keeping the dose to organs at risk (OARs) as low as possible. A second plan was then optimized with IPSA on the same CT images and data set (i.e., contours, catheters, and location of dwell points). Targets and OARs dose volume histograms and irradiation time were compared; data were analyzed with paired t-test; p value < 0.05 was considered statistically significant.

Results

The plans with both optimizations meet the clinical requirements. The mean D₉₀ of the clinical target volume was comparable for GO and IPSA. Similar values (p > 0.05) of target V₁₀₀, V₁₅₀, V₂₀₀, HI, and CI were registered for GO and IPSA optimizations. Bladder and rectum D_1cc and D_2cc obtained by GO resulted in larger values than those obtained by IPSA (p = 0.002). V₇₅ for bladder and rectum were slightly higher for IPSA, but without statistical difference (p > 0.05). The irradiation time was comparable (p > 0.05).

Conclusions

In 3D brachytherapy of cervical cancer, GO and IPSA optimizations do not present a significant difference in target dose coverage; nevertheless, IPSA may reduce the maximum dose to normal tissue when compared with GO.

Escalated radiation and prophylactic extended field nodal irradiation are beneficial for FIGO IIIB cervical cancer patients' prognosis

Background

Currently, the standard treatment for locally advanced cervical cancer patients is concurrent chemoradiotherapy. Here we aim to evaluate therapeutic efficacy, treatment failure, toxicity and prognostic factors for FIGO IIIB cervical cancer patients.

Methods

A comprehensive retrospective analysis was performed to understand various factors which contribute to IIIB cervical cancer prognosis. In total 223 well defined patients were assigned according to their pathological subtype, age, pre-treatment HGB level, tumor size, pelvic lymph node (LN) metastasis, para-aortic LN metastasis as well as external irradiation technologies, treatment duration, point A EQD2 dose and concurrent chemotherapy cycles. We then performed correlation studies of these factors and OS, DFS, LCR, DMFS using univariate and multivariate analysis respectively.

Results

We managed to achieve 207 (92.8%) complete response (CR) and 16 (7.2%) partial response (PR) with acceptable adverse effects. Notably, the 5 years OS, DFS, LCR, DMFS for these patients were 61.1, 55.2, 83.6 and 66.4% respectively. Importantly, our studies suggest that escalated point A EQD2 can significantly improve OS, DFS and LCR for FIGO IIIB cervical cancer patients, furthermore, patients without para-aortic LN metastasis who received prophylactic extended field irradiation have significant survival advantage for DFS and a tendency to improve OS and DMFS.

Conclusions

Our results suggest that FIGO IIIB cervical cancer patients should receive higher EQD2 (≥98Gy₁₀) radiotherapy, moreover, patients without para-aortic LN metastasis should receive prophylactic extended field nodal irradiation to improve prognosis.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-1172-1) contains supplementary material, which is available to authorized users.

Cervical gross tumor volume dose predicts local control using magnetic resonance imaging/diffusion-weighted imaging-guided high-dose-rate and positron emission tomography/computed tomography-guided intensity modulated radiation therapy

PURPOSE

Magnetic resonance imaging/diffusion weighted-imaging (MRI/DWI)-guided high-dose-rate (HDR) brachytherapy and (18)F-fluorodeoxyglucose (FDG) - positron emission tomography/computed tomography (PET/CT)-guided intensity modulated radiation therapy (IMRT) for the definitive treatment of cervical cancer is a novel treatment technique. The purpose of this study was to report our analysis of dose-volume parameters predicting gross tumor volume (GTV) control.

METHODS AND MATERIALS

We analyzed the records of 134 patients with International Federation of Gynecology and Obstetrics stages IB1-IVB cervical cancer treated with combined MRI-guided HDR and IMRT from July 2009 to July 2011. IMRT was targeted to the metabolic tumor volume and lymph nodes by use of FDG-PET/CT simulation. The GTV for each HDR fraction was delineated by use of T2-weighted or apparent diffusion coefficient maps from diffusion-weighted sequences. The D100, D90, and Dmean delivered to the GTV from HDR and IMRT were summed to EQD2.

RESULTS

One hundred twenty-five patients received all irradiation treatment as planned, and 9 did not complete treatment. All 134 patients are included in this analysis. Treatment failure in the cervix occurred in 24 patients (18.0%). Patients with cervix failures had a lower D100, D90, and Dmean than those who did not experience failure in the cervix. The respective doses to the GTV were 41, 58, and 136 Gy for failures compared with 67, 99, and 236 Gy for those who did not experience failure (P<.001). Probit analysis estimated the minimum D100, D90, and Dmean doses required for ≥90% local control to be 69, 98, and 260 Gy (P<.001).

CONCLUSIONS

Total dose delivered to the GTV from combined MRI-guided HDR and PET/CT-guided IMRT is highly correlated with local tumor control. The findings can be directly applied in the clinic for dose adaptation to maximize local control.

Localizing intracavitary brachytherapy applicators from cone-beam CT x-ray projections via a novel iterative forward projection matching algorithm

PURPOSE

To present a novel method for reconstructing the 3D pose (position and orientation) of radio-opaque applicators of known but arbitrary shape from a small set of 2D x-ray projections in support of intraoperative brachytherapy planning.

METHODS

The generalized iterative forward projection matching (gIFPM) algorithm finds the six degree-of-freedom pose of an arbitrary rigid object by minimizing the sum-of-squared-intensity differences (SSQD) between the computed and experimentally acquired autosegmented projection of the objects. Starting with an initial estimate of the object's pose, gIFPM iteratively refines the pose parameters (3D position and three Euler angles) until the SSQD converges. The object, here specialized to a Fletcher-Weeks intracavitary brachytherapy (ICB) applicator, is represented by a fine mesh of discrete points derived from complex combinatorial geometric models of the actual applicators. Three pairs of computed and measured projection images with known imaging geometry are used. Projection images of an intrauterine tandem and colpostats were acquired from an ACUITY cone-beam CT digital simulator. An image postprocessing step was performed to create blurred binary applicators only images. To quantify gIFPM accuracy, the reconstructed 3D pose of the applicator model was forward projected and overlaid with the measured images and empirically calculated the nearest-neighbor applicator positional difference for each image pair.

RESULTS

In the numerical simulations, the tandem and colpostats positions (x,y,z) and orientations (alpha, beta, gamma) were estimated with accuracies of 0.6 mm and 2 degrees, respectively. For experimentally acquired images of actual applicators, the residual 2D registration error was less than 1.8 mm for each image pair, corresponding to about 1 mm positioning accuracy at isocenter, with a total computation time of less than 1.5 min on a 1 GHz processor.

CONCLUSIONS

This work describes a novel, accurate, fast, and completely automatic method to localize radio-opaque applicators of arbitrary shape from measured 2D x-ray projections. The results demonstrate approximately 1 mm accuracy while compared against the measured applicator projections. No lateral film is needed. By localizing the applicator internal structure as well as radioactive sources, the effect of intra-applicator and interapplicator attenuation can be included in the resultant dose calculations. Further validation tests using clinically acquired tandem and colpostats images will be performed for the accurate and robust applicator/sources localization in ICB patients.

Radiotherapy versus radiochemotherapy with cisplatin in treatment of cervical cancer

AIM

To compare effects of concomitant radiochemotherapy (RCTh) and radiotherapy (RTh) alone in patients with cervical carcinoma and with 36-months follow-up analysis.

MATERIAL AND METHODS

106 stage IIA-IVA cervical carcinoma women were divided in two groups. RCTh group was treated with teleradiotherapy (50.4 Gy/T), intracavitary brachytherapy (46 Gy), and iv cisplatin (40 mg/m(2)). RTh group was treated with pelvic teletherapy (52-54 Gy/T) and intracavitary brachytherapy (50-55 Gy).

RESULTS

In RCTh group absorbed radiation dose was significantly lower (50.4 vs. 52.7 Gy) and the duration of treatment was significantly shorter (45.1 days vs. 47.8 days). There were no statistical differences in both groups in survival (59% in RCTh group vs. 56% in RTh group), response to treatment (86% vs. 90%), local recurrence (42% vs. 49%) metastasis occurrence (21% vs. 17%), anemia (40% vs. 26%), early postradiation reactions in intestines (77% vs. 65%) and bladder (71% vs. 61%) as well as in incidence of rectovaginal (10% vs. 4%) and vesicovaginal formation of fistulas (6% vs. 4%), respectively. There were significant differences between two groups in: nausea (77% vs. 6%), vomiting (65% vs. 3.7%), leucopenia (69% vs. 26%) and thrombocytopenia (35% vs. 9%), and late postradiation bladder effects (94% vs. 74%). RCTh patients with anemia had lower 36-months survival rates (42% vs. 71%), more frequent local recurrences (77% vs. 31%) and metastasis-free survival rates (61% vs. 90%) than RCTh patients without anemia.

CONCLUSIONS

RCTh gives better treatment results in patients without than in patients with anemia and higher overall survival rates than RTh in patients without anemia. The only clinical prognostic factor for advance cervical carcinoma is the clinical stage of the disease.

Intercomparison of treatment concepts for MR image assisted brachytherapy of cervical carcinoma based on GYN GEC-ESTRO recommendations

PURPOSE

To perform a multicentre intercomparison study of treatment concepts for MRI assisted brachytherapy of cervix cancer based on recommendations of the Gynaecological GEC-ESTRO Working Group.

METHODS

Each participating centre (IGR Paris, University Hospital Leuven, Medical University of Vienna) contributed data of one patient with comparable clinical features. GTV, High Risk CTV (HR CTV), Intermediate Risk CTV (IR CTV) and organ walls of bladder, rectum and sigmoid colon were delineated at the time of each brachytherapy fraction on axial MR images with the applicator in place. Dose-volume histograms were calculated to evaluate doses to tumour, target volumes and organs at risk. Dose values were biologically normalised to equivalent doses in 2 Gy fractions (EQD(2), equivalent to 50 cGy/h low dose rate) applying the linear-quadratic model.

RESULTS

Total doses to point A from external beam therapy plus brachytherapy ranged from 85 to 91 Gy and were close to the dose covering 90% of HR CTV (D90=85-87 Gy). D90 of IR CTV was within 69-73 Gy. Doses to organs at risk were comparable.

CONCLUSIONS

This study indicates the feasibility of the GEC-ESTRO recommendations. Despite different treatment concepts, biologically normalised total doses to tumour, target volumes and organs at risk were comparable.

Dose and volume parameters for MRI-based treatment planning in intracavitary brachytherapy for cervical cancer

PURPOSE

Magnetic resonance imaging (MRI)-based treatment planning in intracavitary brachytherapy allows optimization of the dose distribution on a patient-by-patient basis. In addition to traditionally used point dose and volume parameters, dose-volume histogram (DVH) analysis enables further possibilities for prescribing and reporting. This study reports the systematic development of our concept applied in clinical routine.

METHODS AND MATERIALS

A group of 22 patients treated with 93 fractions using a tandem-ring applicator and MRI-based individual treatment planning for each application was analyzed in detail. High-risk clinical target volumes and gross tumor volumes were contoured. The dose to bladder, rectum, and sigma was analyzed according to International Commission of Radiation Units and Measurements (ICRU) Report 38 and DVH parameters (e.g., D(2cc) represents the minimal dose for the most irradiated 2 cm(3)). Total doses, including external beam radiotherapy and the values for each individual brachytherapy fraction, were biologically normalized to conventional 2-Gy fractions (alpha/beta 10 Gy for target, 3 Gy for organs at risk).

RESULTS

The total prescribed dose was about 85 Gy(alphabeta10), which was mainly achieved by 45 Gy external beam radiotherapy plus 4 x 7 Gy brachytherapy (total 84 Gy(alphabeta10)). The mean value was 82 Gy(alphabeta10) for the point A dose (left, right) and 84 cm(3) for the volume of the prescribed dose. The average dose to the clinical target volume was 66 Gy(alphabeta10) for the minimum target dose, 87 Gy(alphabeta10) for the dose received by at least 90% of the volume, with a mean volume treated with at least the prescribed dose of 89%. The mean D(2cc) for the bladder was 83 Gy(alphabeta3), the ICRU point dose was 75 Gy(alphabeta3), and the dose at the ICRU point plus 1.5 cm cranially was 100 Gy(alphabeta3). The average dose to the rectum was 64 Gy(alphabeta3) for D(2cc) and at ICRU point 69 Gy(alphabeta3). The sigma D(2cc) was 63 Gy(alphabeta3).

CONCLUSION

A standard loading pattern should be used as the starting point for MRI-based optimization. Individual changes of active dwell positions and dwell weights are guided by a concept of DVH constraints for target and organs at risk. In our clinical routine, the dose to point A and dose received by at least 90% of the volume for the clinical target volume are both comparable to the prescribed dose. The DVH constraints for organs at risk allow reproducible treatment plans, helping to detect and avoid severe overdosage.

Proposed guidelines for image-based intracavitary brachytherapy for cervical carcinoma: Report from Image-Guided Brachytherapy Working Group

PURPOSE

To present issues to be considered in, and make proposals for, image-based brachytherapy for cervical cancer.

METHODS AND MATERIALS

The Image-Guided Brachytherapy Working Group, consisting of representatives from the Gynecology Oncology Group (GOG), Radiologic Physics Center (RPC), American Brachytherapy Society (ABS), American College of Radiology (ACR), American College of Radiology Imaging Network (ACRIN), American Association of Physicists in Medicine (AAPM), Radiation Therapy Oncology Group (RTOG), and American Society for Therapeutic Radiology and Oncology (ASTRO), proposed guidelines for image-based brachytherapy for cervical cancer. This report was based on their aggregate clinical experience and a review of the literature. It reflects only the personal opinions of the authors and is not meant to be an endorsement from any of the above organizations.

RESULTS

The Group recommended T(2)-weighted MRI using a pelvic surface coil with MRI-compatible brachytherapy applicators in place for image-based intracavitary brachytherapy for cervical cancer. Imaging must be performed with the patient in the treatment position, with all other treatment conditions duplicated as closely as possible. Future use of positron emission tomography or positron emission tomography/CT may obviate the need for special applicators. The group proposed the following terminology for image-based brachytherapy. The GTV((I)) is defined as the gross tumor volume as defined through imaging, GTV is defined as the GTV((I)) plus any clinically visualized or palpable tumor extensions, and GTV + cx is defined as the GTV plus the entire cervix. The dose-volume histograms (DVH) of the GTV, GTV((I)), GTV + cx should be performed, and the dose to 100%, 95%, or 90% of the GTV (D(100), D(95), and D(90), respectively) and the percentage of the GTV covered by Point A dose (V(100)) should be reported. Similarly, the DVH of the bladder and rectum wall should be performed, and the maximal dose at any point within the bladder and rectal wall should be reported, along with the maximal dose to a contiguous 1, 2, and 5 cm(3) volume of the bladder and rectum, respectively. In addition, the dose at the International Commission on Radiation Units and Measurements reference point for the bladder and rectum should be reported. The Group thought that the current dose prescription method in use for cervical cancer brachytherapy (i.e., to prescribe to Point A in most institutions) should not be changed as yet, because image-based dosimetry is not ready for routine practice. The Group proposes that for research purposes, individual centers and cooperative groups (e.g., GOG, RTOG, ACRIN) collect image-based dosimetry information and perform DVHs and correlate these data with the clinical outcome to determine which of the above parameters are relevant. The Group encourages external funding for image-based dosimetry and recommends that brachytherapy manufacturers develop image-compatible applicators.

CONCLUSION

Although current institutional brachytherapy prescription for cervical cancer should continue, image-based data collection and analysis are needed to optimize cervical cancer brachytherapy. Proposals are made for research in image-based brachytherapy for cervical cancer.

Total reference air kerma: to what extent can it predict intracavitary volume enclosed by isodose surfaces during multiple high-dose rate brachytherapy?

BACKGROUND

The International Commission on Radiation Units and Measurements (ICRU) report 38 recommends reporting of total reference air kerma (TRAK) and reference ICRU isodose volumes during intracavitary brachytherapy (ICBT) in cancer of the cervix. The present study attempts to estimate the volumes enclosed by isodose surfaces from TRAK and evaluate its utility to represent doses to organs of interest.

MATERIAL AND METHODS

Volumes encompassed by isodose surfaces of 3 Gy, 6 Gy, 9 Gy, and 12 Gy were obtained for 90 high-dose rate (HDR) ICBT procedures. These were used to derive a relation between isodose volumes, TRAK/dose (K/D), and rectal and bladder doses.

RESULTS

Actual volumes (V) encompassed by isodose surfaces were reflected as a quadratic function of K/D (r(2)=0.998) and the expression, V=-23.09+1295.99(K/D)+5661.65(K/D)(2) gave the best estimates for various volumes. No correlation was observed between TRAK and bladder (r(2)=0.086) or rectal doses (r(2)=0.082).

CONCLUSIONS

Estimates of volumes encompassed by different dose levels from TRAK could be derived with reasonable certainty. However, TRAK fails to correlate with rectal and bladder doses.

Problems in reporting doses and volumes during multiple high-dose-rate intracavitary brachytherapy for carcinoma cervix as per ICRU Report 38: a comparative study using flexible and rigid applicators

OBJECTIVE

The objective was to evaluate the extent of geometric and positional variations of two different applicators during multiple high-dose-rate (HDR) intracavitary brachytherapy (ICBT) in carcinoma cervix and its implication on reporting as per International Commission on Radiation Units and Measurement (ICRU) Report 38.

METHODS

Fifty patients, following teletherapy, were randomly allocated to two groups of 25 each. They received a dose of 6 Gy to point A during each of the three HDR ICBT applications by either a flexible Ralstron or a rigid geometry Rotterdam applicator. The various applicator components related to its geometry and their Cartesian coordinates were evaluated from orthogonal films. The doses to ICRU bladder, rectal, pelvic, lymphatic trapezoid points, and dimensions of 6-Gy ICRU height, width, thickness, and volume were estimated for each application.

RESULTS

Significant variation was observed with the three HDR ICBT applications for each group, for all components and for both applicators, although it was relatively more with the flexible Ralstron applicator. The average shift in each of the coordinates of os, uterine tip, and ovoids was around 10 mm for both groups. These resulted in significant variations in all the ICRU Report 38 reporting parameters for three insertions in any given patient and across 25 patients of both groups.

CONCLUSIONS

Multiple HDR ICBT applications led to significant variation in the applicator geometry and its positions in pelvis, irrespective of the applicator rigidity. This results in uncertainties in reporting as per ICRU Report 38 guidelines, and thus calls for its revision.

Physiologic FDG-PET three-dimensional brachytherapy treatment planning for cervical cancer

PURPOSE

To compare conventional two-dimensional (2D) orthogonal radiography-based brachytherapy treatment planning for cervical cancer with a three-dimensional (3D) treatment planning technique based on 18F-fluoro-deoxyglucose-positron emission tomography (FDG-PET).

METHODS AND MATERIALS

Eleven cervical cancer patients were included in this prospective study that evaluated one tandem and ovoid brachytherapy procedure for each patient. The patient underwent FDG-PET of the pelvis to visualize the tumor followed by a second FDG-PET scan with the FDG isotope placed inside the tandem and ovoid applicators to visualize the treatment source positions for 3D treatment planning. The tumor volumes were delineated using a binary threshold technique in which the threshold FDG-PET image intensity was 40% of the peak tumor intensity.

RESULTS

FDG-PET provides a reliable estimate of the cervical cancer volume and 3D spatial relationship of the tumor to the tandem and ovoid applicators. The maximal bladder and rectal doses determined from the 3D FDG-PET dose-volume histograms were found to be higher than those obtained using 2D treatment planning. The minimal dose to the tumor volume defined by FDG-PET ranged from 50 to 475 cGy for treatment plans designed to deliver 650 cGy to Point A and exhibited an inverse correlation with tumor volume.

CONCLUSION

Physiologic FDG-PET brachytherapy treatment planning is feasible and accurate relative to conventional 2D treatment planning. The use of FDG-PET offers a unique method for tumor visualization and identifies the limitations of conventional brachytherapy treatment planning for coverage of large tumors and estimation of the dose to normal structures. This technique has the potential for improving isodose tumor coverage for patients with cervical cancer while sparing critical structures.