Is simulation necessary for each high-dose-rate tandem and ovoid insertion in carcinoma of the cervix?

Reporting of Inter Fraction Dose Variations of Organs at Risk in Computed Tomography-Guided High Dose Rate Intracavitary Brachytherapy in Carcinoma Cervix

Assess the interfraction dose variations of the organs at risk (OARs) in carcinoma cervix high dose rate (HDR) computed tomography (CT)-guided intra cavitary brachytherapy (ICBT). 120 CT scans of 40 patients who had undergone three fractions of ICBT (7 Gy/fr) were analyzed. Dose to Point A and the minimum doses to the volumes of 2, 1, and 0.1cc of bladder, rectum and sigmoid colon were recorded. Revised plans were generated in 20 patients. Paired t-test was used to compare the difference in the means. Point "A" mean dose difference was statistically significant between the treated and revised plans. For bladder, the difference in means of dosage to all volumes, whilst for the rectum and sigmoid colon, the low volume dosage (0.1cc) was statistically significant. Absence of individualized planning would have resulted in underdosage of tumor and increased dosage of up to 30% to OARs. CT-guided ICBT should be implemented for each HDR fraction treatment.

Computed Tomography-Guided Interstitial Brachytherapy for Locally Advanced Cervical Cancer: Introduction of the Technique and a Comparison of Dosimetry With Conventional Intracavitary Brachytherapy

Objective

We present a new technique of 3-dimensional computed tomography–guided interstitial (IS) brachytherapy (BT) for locally advanced cervical cancer, offering a more advantageous clinical treatment approach.

Materials/Methods

Interstitial BT was performed using an applicator combining uterine tandem and metal needles; needles were inserted freehand under real-time 3-dimensional computed tomography guidance. Twenty-eight patients with bulky tumors and/or parametrial extension (tumor size > 5 cm) after external beam radiotherapy received IS BT. Dosimetric outcomes of the IS BT including the total dose (external beam radiotherapy and high dose-rate BT) D90 for the high-risk clinical target volume (HR-CTV) and D2cc for the organs at risk (OARs) were investigated and compared with a former patient group consisting of 30 individuals who received the conventional intracavitary (IC) BT.

Results

The mean D90 values for HR-CTV in the IC BT and IS BT groups were 76.9 ± 5.7 and 88.1 ± 3.3 Gy, respectively. Moreover, 85.7% of the patients received D90 for HR-CTV of 87 Gy or greater in the IS BT group, and only 6.7% of the patients received D90 for HR-CTV of 87 Gy or greater in the IC BT group. The D2cc for the bladder, rectum, and sigmoid were 84.7 ± 6.8, 69.2 ± 4.2, and 67.8 ± 4.5 Gy in the IC BT group and 81.8 ± 6.5, 66.8 ± 4.0, and 64.8 ± 4.1 Gy in the IS BT group. The mean number of needles was 6.9 ± 1.4, with a mean depth of 2.9 ± 0.9 mm for each IS BT. Interstitial BT was associated with only minor complications.

Conclusions

The IS BT technique resulted in better dose-volume histogram parameters for large volume tumors (>5 cm) compared with the conventional IC BT and acceptable risk of acute complications in locally advanced cervical cancer and is clinically feasible.

A comprehensive evaluation of adaptive daily planning for cervical cancer HDR brachytherapy

The purpose of this study was to evaluate adaptive daily planning for cervical cancer patients who underwent high‐dose‐rate intracavitary brachytherapy (HDR‐BT) using comprehensive interfractional organ motion measurements. This study included 22 cervical cancer patients who underwent 5 fractions of HDR‐BT. Regions of interest (ROIs) including high‐risk clinical tumor volume (HR‐CTV) and organs at risk (OARs) were manually contoured on daily CT images. All patients were clinically treated with adaptive daily plans (ADP), which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans (SP) were retrospectively generated by applying the first treatment fraction's dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similarity metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity (JRARM) score was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between interfractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon signed‐rank tests were used to assess ADP and SP by comparing EQD2D2cc(α/β=3) for OARs. For interfractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM, DSC, and RMSD metrics. Comparisons between paired ROIs showed differences in metrics at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found ADP provided lower EQD2 D2cc of OARs than SP. Specifically, the sigmoid demonstrated statistically significant dose variations (p=0.015). Substantial interfractional organ motion occurs during HDR‐BT based on comprehensive measurements and may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning with the extent of sparing being different among OARs.

PACS number(s): 87.55.D, 87.55.de, 87.55.kh, 87.57.nj

Clinical feasibility of interstitial brachytherapy using a "hybrid" applicator combining uterine tandem and interstitial metal needles based on CT for locally advanced cervical cancer

PURPOSE

To explore the dosimetric advantage of target volume and surrounding normal tissue by using interstitial (IS) brachytherapy (BT) based on three-dimensional CT in locally advanced cervical cancer, as a simple and effective clinical treatment approach.

METHODS AND MATERIALS

Fifty-two patients with poor tumor response to external beam radiotherapy and a residual tumor >5 cm at the time of the first BT were included. IS BT was performed using a "hybrid" applicator combining uterine tandem and free metal needles based on three-dimensional CT. The high-risk clinical target volume (HR-CTV), intermediate-risk clinical target volume, and organs at risk were contoured. The total dose, including external beam radiotherapy (45 Gy in 25 fractions) and high-dose-rate BT (30 Gy in 5 fractions), was biologically normalized to conventional 2-Gy fractions. D90 and D100 for HR-CTV and intermediate-risk clinical target volume and D2cc for the bladder, rectum, and sigmoid were analyzed.

RESULTS

The mean D90 value for HR-CTV was 88.4 ± 3.5 Gy. Totally, 88.5% of the patients received D90 for HR-CTV ≥87 Gy. The D2cc for the bladder, rectum, and sigmoid were 81.1 ± 5.6, 65.7 ± 5.1, and 63.1 ± 5.4 Gy, respectively. The mean number of needles was 6.9 ± 1.3 for each application. IS BT was associated with minor complications.

CONCLUSION

IS BT using the "hybrid" applicator provides a dosimetric advantage for target volume and organs at risk in large-volume (>5 cm) tumors and is, thereby, clinically feasible. However, the long-term curative effect and possible toxicity need further clinical observation.

Image-Based Brachytherapy for the Treatment of Cervical Cancer

Cervical cancer is a disease that requires considerable multidisciplinary coordination of care and labor in order to maximize tumor control and survival while minimizing treatment-related toxicity. As with external beam radiation therapy, the use of advanced imaging and 3-dimensional treatment planning has generated a paradigm shift in the delivery of brachytherapy for the treatment of cervical cancer. The use of image-based brachytherapy, most commonly with magnetic resonance imaging (MRI), requires additional attention and effort by the treating physician to prescribe dose to the proper volume and account for adjacent organs at risk. This represents a dramatic change from the classic Manchester approach of orthogonal radiographic images and prescribing dose to point A. We reviewed the history and currently evolving data and recommendations for the clinical use of image-based brachytherapy with an emphasis on MRI-based brachytherapy.

Magnitude and Implications of Interfraction Variations in Organ Doses during High Dose Rate Brachytherapy of Cervix Cancer: A CT Based Planning Study

Background. Quantifying the interfraction dose variations in the organs at risk (OAR) in HDR intracavitary brachytherapy (HDR ICBT). Methods. Rectum and bladder were contoured in 44 patients of cervical carcinoma on CT after each fraction of HDR ICBT (9 Gy/2 fractions). Interfraction dose variations (VAR_act) were calculated. Rigid image registration of consecutive fraction images allowed quantification of the hypothetical variation in dose (VAR_hypo) arising exclusively due to changes in applicator placement and geometry. VAR_hypo was regressed against the VAR_act to find out to what extent the applicator variation could explain the VAR_act in the OAR. The rest of the variation was assumed to be due to organ deformation. Results. The VAR_act in the dose to 2 cc of bladder and rectum were 1.46 and 1.16 Gy, respectively. Increased dose was seen in 16 and 23 patients in the subsequent fraction for bladder and rectum, respectively. Doses to OAR would have exceeded constraints in 16% patients if second fraction was not imaged. VAR_hypo explained 19% and 47% of the VAR_act observed for the bladder and rectum respectively. Conclusions. Significant interfraction variations in OAR doses can occur in HDR ICBT. Organ deformations are mostly responsible for this variation.

Single magnetic resonance imaging vs magnetic resonance imaging/computed tomography planning in cervical cancer brachytherapy

AIMS

To compare differences in dose to the target volume and organs at risk (OARs) for ring and tandem brachytherapy using individualised magnetic resonance imaging (MRI)/computed tomography-based three-dimensional treatment plans for each application vs plans based on a single scan for all fractions.

MATERIALS AND METHODS

The study was carried out in 10 patients with carcinoma of the uterine cervix, treated with external beam radiotherapy and five fractions of high dose rate brachytherapy. Planning was carried out using MRI for the first fraction and computed tomography for each of the four subsequent fractions. The MRI-based plan was taken as the reference and the single-plan procedure was calculated by using the weights from the reference plan to calculate the dose distribution for each subsequent computed tomography-based plan. The high-risk clinical target volume (HRCTV) and OARs were delineated as per GEC-ESTRO guidelines. Total doses from external beam radiotherapy and brachytherapy were summated and normalised to a 2 Gy fraction size.

RESULTS

The mean D(90) for the HRCTV was 81.9 Gy when using one plan and 84 Gy when using individual treatment plans. Similarly, the mean D(2 cc) was 75.68 Gy vs 74.99 Gy for the bladder, 55.84 Gy vs 56.56 Gy for the rectum and 64.8 Gy vs 65.5 Gy for the sigmoid. Ring rotation was identified in three patients, resulting in a change in dwell positions, which otherwise could have led to either a high bladder dose or suboptimal coverage of the HRCTV.

CONCLUSIONS

Our study has shown that a single-plan procedure achieved acceptable dosimetry in most patients. However, the individualised plan improved dosimetry by accounting for variations in applicator geometry and the position of critical organs.

An analysis of simulation for adjuvant intracavitary high-dose-rate brachytherapy in early-stage endometrial cancer

PURPOSE

The utility of serial simulations in vaginal vault irradiation is controversial. Our primary endpoint was to assess the significance of simulation in women who received adjuvant intracavitary high-dose-rate brachytherapy (HDR-BT) for early-stage endometrial adenocarcinoma. Secondary endpoints included assessment of acute and late treatment toxicity, medication requirements, and charges related to the HDR-BT simulation and procedure.

METHODS AND MATERIALS

Twenty-four consecutive women with early-stage endometrial cancer treated with adjuvant HDR-BT were evaluated. Descriptive statistical analyses were performed on the ratio of calculated to prescription BT dose at predefined dosimetric points. Data on acute and late toxicities, medication usage, and simulation charges were evaluated and compared.

RESULTS

The intravaginal cylinder was placed three times over 10-14 days (median 6.5Gy prescribed to 5mm). No substantial deviation in the means of the calculated ratios was observed except at the bladder point (mean 0.77+/-0.23). Early toxicity was found to be no greater than Grade 1 (n=5). Serious late toxicities were uncommon; one woman developed a Grade 3 gastrointestinal toxicity. Half of the women required prescription medication incident to simulation. The average simulation charge was $1252.80.

CONCLUSIONS

Despite the broad range of doses calculated at the bladder point, genitourinary toxicity was minimal. Simulation proved useful in recording dose and represented a small, yet important portion of the total treatment charge but did not alter treatment in this series. The necessity of simulation for intracavitary high-dose-rate vaginal brachytherapy remains unclear.

Uncertainties when using only one MRI-based treatment plan for subsequent high-dose-rate tandem and ring applications in brachytherapy of cervix cancer

BACKGROUND AND PURPOSE

This retrospective study compares individual MRI based 3D treatment planning for each intracavitary applicator insertion and the use of only one MRI treatment plan for cervical cancer brachytherapy.

MATERIALS AND METHODS

GTV, high risk (HR) CTV and OAR were delineated and analysed for 14 patients. Data using the individual approach were taken from the actual irradiated plans. The "single plan procedure" was simulated by matching the dose distribution of the first plan to the MRI datasets of each subsequent implantation. Total doses from brachytherapy were added up and normalized to 2Gy fractionation (EQD2).

RESULTS

The mean D90 for HR CTV was 6Gy higher when using one plan than when using individual treatment plans. The D(2cc) increased 3.5Gy for the bladder, 4.2Gy for the rectum and 5.8Gy for the sigmoid. The use of only one treatment plan would have resulted in 2, 1 and 5 extra cases exceeding total D(2cc) constraints for bladder (90Gy), rectum (75Gy) and sigmoid (75Gy), respectively.

CONCLUSION

The use of only one treatment plan for several applications results in higher dose to target and OAR structures. CT, clinical examination and X-ray findings can help to reduce certain situations of overdosage, when individual MRI based treatment planning is not available for each fraction.

Patterns of brachytherapy practice for patients with carcinoma of the cervix (1996–1999): A Patterns of Care Study

PURPOSE/OBJECTIVE

To analyze the details of brachytherapy practice in patients treated for carcinoma of the cervix in the United States between 1996 and 1999.

METHODS AND MATERIALS

Radiation facilities were selected from a stratified random sample. Patients were randomly selected from lists of eligible patients treated at each facility. A total of 442 patients' records were reviewed in 59 facilities to obtain data about patients' characteristics, evaluation, tumor extent, and treatment. National estimates were made using weights that reflected the relative contribution of each institution and of each patient within the sampled institutions. From our survey we estimate that 16,375 patients were treated in the United States during this study period. Unless otherwise specified, brachytherapy practice was based on the 408 patients who had their brachytherapy or all their treatment at the surveyed facility.

RESULTS

A total of 91.5% of patients underwent brachytherapy at the initial treating institution; 8.5% were referred to a second site for brachytherapy. Forty-two percent of U.S. facilities referred at least some patients to a second facility for brachytherapy. Of U.S. facilities that treated < or =2 eligible patients per year, 61% referred all of their patients to a second facility for brachytherapy or treated with external RT alone; none of the U.S. facilities with larger experience (>2 eligible patients per year) referred all their patients to a second facility for brachytherapy treatment, but 28% referred some patients to an outside facility for brachytherapy. Overall, 94% of patients who completed treatment with curative intent received brachytherapy. Of these patients who had brachytherapy, 77.8%, 13.3%, and 0.9%, respectively, were treated with low-dose-rate (LDR), high-dose-rate (HDR), or a combination of HDR and LDR brachytherapy; 7.9% had interstitial brachytherapy (5.7% LDR and 1.9% HDR, 0.3% mixed). In facilities that treated >2 patients per year, 15.5% and 9.4% of brachytherapy procedures included HDR or interstitial, respectively; in facilities that treated fewer patients, 3.4% had HDR brachytherapy, and only 1.2% had interstitial brachytherapy. Patients treated with LDR intracavitary radiotherapy had one (23.5%), two (74.1%), or three (2.4%) implants. For patients treated with curative intent who completed radiation therapy with LDR intracavitary radiation therapy without hysterectomy, the median brachytherapy dose to Point A was 40.3 Gy, and the median total dose to Point A was 82.9 Gy. Patients were treated with HDR intracavitary radiation therapy using a variety of treatment schedules using 1-2 fractions (7.5%), 3-4 fractions (17.4%), 5-6 fractions (38.5%), 7-9 fractions (33.5%), or 12 fractions (3%). Fraction sizes were <500 cGy (29.5%), 500-<600 (25.2%), 600 (28.1%), >600 (8%), or unknown (9.2%). For patients treated with HDR, the median total dose to Point A (corrected for fraction size using a alpha/beta = 10) was 85.8 Gy (range: 56.2-116.1 Gy). At institutions treating <500 new patients per year, the percentage of patients receiving a brachytherapy dose <40 Gy was significantly higher than at institutions treating > or =500 new patients per year (p < 0.0001). For LDR intracavitary radiation therapy, 5.8% had neither bladder nor rectal doses recorded for any of their implants, whereas in HDR intracavitary radiation therapy, 73.4% had neither bladder nor rectal doses recorded for any of their implants. The median total duration of radiation therapy was identical for patients who had HDR or LDR intracavitary radiation therapy (57 days). For LDR at institutions treating <500 new patients per year, the percentage of patients with treatment duration >56 days was significantly greater than at institutions > or =500 new patients per year (p = 0.002). Of the patients who had LDR intracavitary radiation therapy implants, 65% were treated using tandem and shielded Fletcher-Suit-Delclos colpostats; other patients had mini ovoids (10.9%), cylinders (3.9%), Henschke (3.7%), or other/mixed applicators (16.5%). In contrast, of patients treated with HDR intracavitary radiation therapy, 68.7% had tandem and rings, 18.2% Fletcher-Suit-Delclos ovoids, 7.5% mini ovoids, 2.3% cylinders, and 3.2% other or mixed applicators.

CONCLUSIONS

The median duration of treatment and median Point A dose were very similar for patients treated with HDR or LDR. Patients with HDR were treated using a variety of treatment schedules. Different applicator types were favored for LDR vs. HDR. Of patients treated with HDR, 73.4% had no brachytherapy bladder or rectal doses recorded, suggesting that full dosimetric calculations were performed only for the first fraction in many institutions. Facility size significantly impacted on referral to another institution for brachytherapy, brachytherapy dose, and treatment duration.