Image guided adaptive brachytherapy for cervical cancer: dose contribution to involved pelvic nodes in two cancer centers

Dose Contribution to the Regional Lymph-Node Metastases and Point B from Intracavity and Interstitial Hybrid Brachytherapy in Locally Advanced Cervical Cancer

PURPOSE

Analyzing dose distributions to regional lymph-node metastases (RLNMs) in locally advanced cervical cancer (LACC) patients undergoing intracavitary and interstitial hybrid brachytherapy (IC/IS).

METHODS

Dose distributions of eleven LACC patients with 38 RLNMs, and who received 38 IC/IS sessions were analyzed in EQD2, considering RLNM positions and ipsilateral interstitial needles; these RLNMs, excepting the para-aortic region, were classified into four groups.

RESULTS

RLNMs had a median of two ipsilateral interstitial needles per session. Significant differences were observed in total RLNM D90, depending on whether the position was cranial or caudal of the uterine base (85.5 vs. 378.9 cGy, p < 0.0001), and whether the RLNM D90 was associated with a number of ipsilateral interstitial needles between 0-1 or 2 or more (68.4 vs. 112.2 cGy, p = 0.006) per session. At each session, Group 1 RLNMs (cranial of the uterine base, 0-1 ipsilateral interstitial needle) had a mean D90 of 21.1 cGy; Group 2 (cranial, 2 or more), 73.8; Group 3 (caudal, 0-1), 94.7; and Group 4 (caudal, 2 or more), 136.1.

CONCLUSION

RLNMs located caudal of the uterine base associated with two or more ipsilateral interstitial needles in IC/IS had a higher dose contribution, which should be considered when calculating the RLNMs' dose of external beam boost irradiation.

18F-fluorodeoxyglucose PET-CT-guided pelvic chemoradiation therapy using helical tomotherapy for locally advanced carcinoma cervix without para-aortic nodal disease: Clinical and patient-reported outcomes from a prospective phase 2 study

INTRODUCTION

Locally advanced carcinoma cervix (LACC) is a heterogeneous disease with variable combinations of primary tumour extensions with or without nodal involvement. Metabolic information from 18 fluro-deoxyglucose positron emission tomography combined with contrast-enhanced computerized tomography (FDG PET-CT) may potentially augment treatment decision-making for LACC. This study ascertained FDG-PET CT influence on chemoradiation therapy (CTRT) decisions in LACC. We report oncologic and patient-reported outcome measures (PROMs).

METHODS

FDG PET-CT scans were reviewed independently by two nuclear medicine specialists and two radiation oncologists. Pelvic CTRT plan digressions were documented and therapy was adapted accordingly. Pelvis radiation (50 Gy/25#/5 weeks) using tomotherapy with weekly cisplatin was used in node-negative disease. Dose-escalated simultaneous integrated boost (SIB) 60 Gy/25#/5 weeks was delivered to involved pelvic nodes. All received brachytherapy. Post-treatment PET-CT scans were at 6 months. Functional assessment of cancer therapy scores were calculated at baseline, treatment completion, 3 months, 1 year and 3 years.

RESULTS

Between November 2015 and January 2018, 85 patients were screened, and 77 consented. Extrapelvic disease was seen in 12 (16%) patients (9 para-aortic nodes, 2 distant metastases and 1 synchronous carcinoma breast); 60 patients were included in the final analysis. Decision changes were seen in 10/77 (13%) screened, 8/60 (13%) included and 32 (53.3%) received SIB. Post-treatment, 27 (45%) had grade 2 GI/GU/GYN toxicity, one (2%) had grade 3 GI and five (8.3%) had grade 3 neutropenia. At median overall survival of 54.2 months (95% CI 52.8-58.3), 5-year local failure, pelvic nodal and para-aortic nodal-free survival were 86.8% (95% CI 78.0-96.6), 85.2% (95% CI 76.1-95.3) and 85.2% (95% CI 76.2-95.4). Functional assessment of cancer therapy trial outcome index (FACT TOI) improved by 10.43 at 3 months with no further decline. Grade 3 toxicity was noted for abdominal pain in one (1.7%), cystitis in four (6.7%) and lymphoedema in one (1.7%) at 5 years.

CONCLUSION

PET-CT resulted in major decision changes in 13%. PET-adapted CTRT was associated with acceptable toxicity, encouraging long-term survival and improvement in PROMS.

Evaluation of doses to pelvic lymph node regions from image-guided high-dose-rate interstitial brachytherapy for carcinoma of the uterine cervix

Purpose

Interstitial brachytherapy (ISBT) is indicated for intact cervical carcinoma (IN-CC) if intracavitary brachytherapy (ICRT) is not feasible and also in vault carcinoma (VA-C). We aimed to evaluate the doses to pelvic lymph node regions in IN-CC and VA-C treated with ISBT.

Material and methods

Ten patients (6 IN-CC, 4 VA-C) were chosen for this dosimetric study. IN-CC had a central tandem in addition to the needles. External iliac (EI-N), internal iliac (II-N), obturator (OB-N) and sacral (SA-N) groups of lymph nodes were delineated. A dose of 10 grays (Gy) and 8 Gy each × 2 fractions was prescribed to the target in IN-CC and VA-C respectively. Doses received by 100%, 90% and 50% volume (D100, D90, D50) and D2cc, D1cc, D0.1cc were evaluated. Doses to lymph nodal groups in IN-CC vs. VA-C were compared using Student's t-test.

Results

For 20 implants, the median number of needles was 18 (range, 16-20). Mean D90 and D2cc of the combined bilateral OB-N, II-N, EI-N and SA-N groups were 33.62 ±3.46% and 102.94 ±10.71%, 6.98 ±0.65% and 39.69 ±3.64%, 5.1 ±0.51% and 15.4 ±0.8%, 7.76 ±0.95% and 15.36 ±1.09% of the prescribed doses respectively. Patients with a central tandem (IN-CC) received significantly higher doses to external, internal iliac and sacral group of lymph nodes (p < 0.001) as compared to VA-C.

Conclusions

In patients with cervical carcinoma treated with ISBT, pelvic lymph node groups received significant doses. The dose contribution to pelvic lymph nodes is higher in patients with intact cervical cancer where a central tandem is used as compared to post-operative patients.

Inter-Fractional Variations in Volume and Radiation Dose to the Organs at Risk, High-Risk Clinical Target Volume and Implication of Image-Guided Adaptive Planning During Intracavitary Brachytherapy of Carcinoma Cervix

Background

Geometrical and anatomical variations occur during the brachytherapy of carcinoma cervix and dose optimization is necessary for every fraction of high‑dose rate intracavitary brachytherapy (HDR-ICBT) for carcinoma of the cervix. A single planned treatment is usually delivered for multiple fractions without consideration of inter-fractional applicator positioning variations and organ motion, which may lead to substantial differences between the planned and delivered doses.

Aim and objectives

This study was aimed at evaluating the inter-fractional variation in volume and radiation dose to organs at risk during ICBT for cervical cancer. Furthermore, the doses to high-risk clinical target volume (HRCTV) and the role of adaptive planning in ICBT were assessed.

Materials and methods

Twenty-two patients with carcinoma of the cervix Stage IB2-IVA receiving ICBT were enrolled in the study. All the patients were treated with ICBT four fractions in two applications. For the first application, magnetic resonance imaging-based planning was done, and for the next three fractions, computed tomography (CT) scans were done before every treatment fraction. The CT images were contoured and replanned by keeping the First (I) fraction of each application as the reference. Dose-volume histograms (DVH) were generated, and details of D2cc (DVH on a volume of 2cc) of bladder, rectum, and sigmoid colon (organs at risk-OAR) and D90 HRCTV (dose covering 90%) were documented.

Results

In patients receiving ICBT, variations in OAR D2cc ranged from 1.5 to 2.5Gy for the bladder (p- 0.001), from 2.0 to 3.2Gy (p-0.005) for the rectum and from 1.5 to 3.5Gy for the sigmoid colon (p 0.103). The p-value was significant for D2cc when compared with the OAR volume for the bladder and rectum in both applications, whereas it was not significant for the sigmoid colon. The percentage change in HRCTV coverage was 7% in the first application and by 16% in the second application because of adaptive planning.

Conclusion

Significant variations in doses received by D2cc of the bladder and rectum as well as significant improvement in HRCTV coverage between the fractions were observed because of replanning. Hence, image-guided HDR-ICBT should be incorporated with adaptive planning when delivering in multiple fractions.

Verification of high-dose-rate brachytherapy treatment planning dose distribution using liquid-filled ionization chamber array

Purpose

This study aims to investigate the dosimetric performance of a liquid-filled ionization chamber array in high-dose-rate (HDR) brachytherapy dosimetry. A comparative study was carried out with air-filled ionization chamber array and EBT3 Gafchromic films to demonstrate its suitability in brachytherapy.

Material and methods

The PTW OCTAVIUS detector 1000 SRS (IA 2.5-5 mm) is a liquid-filled ionization chamber array of area 11 x 11 cm² and chamber spacing of 2.5-5 mm, whereas the PTW OCTAVIUS detector 729 (IA 10 mm) is an air vented ionization chamber array of area 27 x 27 cm² and chamber spacing of 10 mm. EBT3 films were exposed to doses up to a maximum of 6 Gy and evaluated using multi-channel analysis. The detectors were evaluated using test plans to mimic a HDR intracavitary gynecological treatment. The plan was calculated and delivered with the applicator plane placed 20 mm from the detector plane. The acquired measurements were compared to the treatment plan. In addition to point dose measurement, profile/isodose, gamma analysis, and uncertainty analysis were performed. Detector sensitivity was evaluated by introducing simulated errors to the test plans.

Results

The mean point dose differences between measured and calculated plans were 0.2% ± 1.6%, 1.8% ± 1.0%, and 1.5% ± 0.81% for film, IA 10 mm, and IA 2.5-5 mm, respectively. The average percentage of passed gamma (global/local) values using 3%/3 mm criteria was above 99.8% for all three detectors on the original plan. For IA 2.5-5 mm, local gamma criteria of 2%/1 mm with a passing rate of at least 95% was found to be sensitive when simulated positional errors of 1 mm was introduced.

Conclusion

The dosimetric properties of IA 2.5-5 mm showed the applicability of liquid-filled ionization chamber array as a potential QA device for HDR brachytherapy treatment planning systems.

Interfraction Variations in Organ Filling and Their Impact on Dosimetry in CT Image Based HDR Intracavitary Brachytherapy

Aim:

Since anatomical and geometric variations occur with every fraction, planning, and dose optimization is necessary for every fraction of high-dose rate intracavitary brachytherapy of carcinoma cervix. In this study, we have tried to quantify the differences in doses to organs at risk (OAR) for each fraction of brachytherapy.

Methods and Materials:

One hundred and seventy computed tomography datasets of cervical cancer patients receiving intracavitary brachytherapy at our institution between January and April 2015 were analyzed. The volumes of the high-risk clinical target volume and OAR contoured were recorded for every insertion. Dose-volume histograms were generated and D90 and D100CTV and D0.1, D1, and D2cc were recorded for bladder, rectum, and sigmoid for each insertion.

Results:

Sixty-one percent had a decrease in bladder volume in the second fraction, 35% had an increase in bladder volume and 4% had no change in bladder volume. There was a strong positive correlation between increase in volume and dose (D2cc), which was statistically significant, r_s = 0.441, P = 0.013. Nearly 49.4% of patients had an increase in rectal volume during the second fraction. 45.9% had decrease in rectal volume during the second fraction. There was a positive correlation between the increase in volume and dose (D2cc), which was statistically significant, r_s = 0.393, P = 0.010. About 63.5% of the patients had a decrease in sigmoid volume during the second fraction, whereas 30.6% had an increase in volume and 5.9% had no change in volume.

Conclusion:

First, this study emphasizes the importance of imaging and planning for every fraction of brachytherapy to quantify the exact doses to the target and OAR s. Second, it is important to follow a uniform bladder protocol for every fraction, and adequate bowel preparation is needed for every fraction to minimize the interfraction variations. Finally, it also opens the realm of an adaptive planning strategy in cervical cancers which are known for rapid tumor regression during radiotherapy.

Optimum organ volume ranges for organs at risk dose in cervical cancer intracavitary brachytherapy

PURPOSE

To analyze the optimum organ filling point for organs at risk (OARs) dose in cervical cancer high-dose-rate (HDR) brachytherapy.

MATERIAL AND METHODS

In a retrospective study, 32 locally advanced cervical cancer patients (97 insertions) who were treated with 3D conformal external beam radiation therapy (EBRT) and concurrent chemotherapy during 2010-2013 were included. Rotterdam HDR tandem-ovoid applicators were used and computed tomography (CT) scanning was performed after each insertion. The OARs delineation and GEC-ESTRO-based clinical target volumes (CTVs) contouring was followed by 3D forward planning. Then, dose volume histogram (DVH) parameters of organs were recorded and patients were classified based on their OARs volumes, as well as their inserted tandem length.

RESULTS

The absorbed dose to point A ranged between 6.5-7.5 Gy. D0.1cm(3) and D2cm(3) of the bladder significantly increased with the bladder volume enlargement (p value < 0.05). By increasing the bladder volume up to about 140 cm(3), the rectum dose was also increased. For the cases with bladder volumes higher than 140 cm(3), the rectum dose decreased. For bladder volumes lower than 75 cm(3), the sigmoid dose decreased; however, for bladder volumes higher than 75 cm(3), the sigmoid dose increased. The D2cm(3) of the bladder and rectum were higher for longer tandems than for shorter ones, respectively. The divergence of the obtained results for different tandem lengths became wider by the extension of the bladder volume. The rectum and sigmoid volume had a direct impact on increasing their D0.1cm(3) and D2cm(3) , as well as decreasing their D10, D30, and D50.

CONCLUSIONS

There is a relationship between the volumes of OARs and their received doses. Selecting a bladder with a volume of about 70 cm(3) or less proved to be better with regards to the dose to the bladder, rectum, and sigmoid.

The air matters - sleeve air cavity as a marker guiding image-guided helical tomotherapy to target cervical cancer

Purpose

Radiotherapy with concurrent chemotherapy has been recommended as standard treatment for locally advanced cervical cancer. To validate the main tumor location before each high-precision helical tomotherapy (HT) fraction, the development of a more reliable marker or indicator is of clinical importance to avoid inadequate coverage of the main tumor.

Material and methods

A 61-year-old woman with cervical cancer, TMN stage cT2b2N1M1, FIGO stage IVB was presented. Extended field external beam radiotherapy (EBRT) with concurrent chemotherapy and the interdigitated delivery of intracavitary brachytherapy was performed. Helical tomotherapy equipped with megavoltage cone beam computed tomography (MV-CBCT) was used for image-guided radiotherapy. For the insertion of tandem of brachytherapy applicator, a silicone sleeve with a central hollow canal was placed into the endocervical canal with the caudal end stopping at the outer surface of the cervical os, and making contact with the distal boundary of the cervical tumor during the entire brachytherapy course.

Results

In the remaining EBRT fractions, we found that the air cavity inside the central hollow canal of the sleeve could be clearly identified in daily CBCT images. The radiation oncologists matched the bony markers to adjust the daily setup errors because the megavoltage of the CBCT images could not provide a precise boundary between the soft tissue and the tumor, but the sleeve air cavity, with a clear boundary, could be used as a surrogate and reliable marker to guide the daily setup errors, and to demonstrate the primary tumor location before delivery of each HT fraction.

Conclusions

The application of the sleeve during the interdigitated course of HT and brachytherapy in this patient provided information for the feasibility of using the sleeve air cavity as a surrogate marker for the localization of the main primary tumor before the daily delivery of image-guided HT.