Dose-volume histogram analysis of high dose rate intracavitary brachytherapy for uterine cervix cancer

A retrospective study of small-pelvis radiotherapy plus image-guided brachytherapy in stage I-II non-bulky cervical squamous cell carcinoma

We herein report a retrospective analysis of the efficacy of a combination therapy of pelvic irradiation that excluded the common iliac lymph nodes region and image-guided brachytherapy (IGBT) for non-bulky (≤4 cm) cervical cancer. Thirty-three patients with stage I-II cervical squamous cell carcinoma (≤4 cm) and without pelvic/para-aortic lymphadenopathy who were treated with definitive radiotherapy alone between February 2009 and September 2016 were included. The radiotherapy consisted of CT-based small-pelvis irradiation (whole pelvis minus common iliac lymph node area) of 20 Gy/10 fractions followed by pelvic irradiation with a midline block of 30 Gy/15 fractions and IGBT of 24 Gy/4 fractions (6 Gy/fraction for high-risk [HR] clinical target volume [CTV] D90%). In-room computed tomography (CT) imaging with applicator insertion was used for brachytherapy planning, with physical examinations and diagnostic magnetic resonance imaging (MRI) also being referred to for determination of HR CTV. Over a median follow-up of 60.5 months (range, 7-89), two patients developed distant recurrence and one developed local and distant recurrence. Two patients died from cervical cancer, one from hepatocellular carcinoma and one from non-cancerous disease. The 2/5-year local control (LC), progression-free survival (PFS) and overall survival (OS) rates were 100%/96.7%, 93.8%/90.6% and 93.9%/93.9%, respectively. No pelvic/para-aortic lymph node recurrence was observed. There were no late complications of grade 3 or higher in the small bowel, large bowel/rectum, or bladder. Our results suggest that a combination therapy of IGBT plus small-pelvis irradiation excluding common iliac lymph nodes provides reasonable clinical outcomes and can be a treatment option in non-bulky (≤4 cm) cervical squamous cell carcinoma.

Dosimetric feasibility of computed tomography-based image-guided brachytherapy in locally advanced cervical cancer: a Japanese prospective multi-institutional study

The aim of this study was to assess the feasibility of planning dose-volume histogram (DVH) parameters in computed tomography-based 3D image-guided brachytherapy for locally advanced cervical cancer. In a prospective multi-institutional study, 60 patients with stage IIA2-IVA cervical cancer from eight institutions were treated with external beam radiotherapy using central shielding and intracavitary or hybrid (combined intracavitary/interstitial) brachytherapy (HBT). The dose constraints were set as a cumulative linear quadratic equivalent dose (EQD2) of at least 60 Gy for high-risk clinical target volume (HR-CTV) D90, D2cc ≤ 75 Gy for rectum, D2cc ≤ 90 Gy for bladder and D2cc ≤ 75 Gy for sigmoid. The median HR-CTV D90 was 70.0 Gy (range, 62.8-83.7 Gy) in EQD2. The median D2cc of rectum, bladder and sigmoid was 57.1 Gy (range, 39.8-72.1 Gy), 68.9 Gy (range, 46.5-84.9 Gy) and 57.2 Gy (range, 39.2-71.2 Gy) in EQD2, respectively. In 76 of 233 sessions (33%), 23 patients underwent HBT, and the median number of interstitial needles was 2 (range, 1-5). HBT for a bulky HR-CTV (≥40 cm3) significantly improved the HR-CTV D90 compared with intracavitary brachytherapy alone (P = 0.010). All patients fulfilled the dose constrains for target and at risk organs by undergoing HBT in one-third of sessions. We conclude that the planning DVH parameters used in our protocol are clinically feasible.

Impact of CT-based brachytherapy in elderly patients with cervical cancer

PURPOSE

Three-dimensional image-guided brachytherapy (3D-IGBT) has become the standard therapy for patients with cervical cancer. However, in this population, the impact of 3D-IGBT in elderly individuals remains unknown. This study assessed the efficacy of 3D-IGBT for elderly patients with cervical cancer.

METHODS AND MATERIALS

We performed a retrospective chart review of 105 consecutive patients with cervical squamous cell carcinoma aged ≥70 years who received radiotherapy alone between January 2001 and September 2014. All patients were treated with external beam radiotherapy and high-dose-rate intracavitary brachytherapy. We assessed the treatment outcomes in all patients. We then compared outcomes between two groups: patients treated by changing the Point A dose at brachytherapy (Group A, n = 71) and those treated with 3D-IGBT at least twice (Group B, n = 34).

RESULTS

The median followup period was 59 (range, 6-203) months; the median age was 77 years. The 5-year local control and cause-specific survival rates were 89% and 78%, respectively. The 5-year cumulative rates of late toxicities of the rectum and bladder of Grade ≥3 were 2.0% and 4.2%, respectively. No statistically significant differences were observed in the local control and cause-specific survival rates, or in the incidence of rectal toxicities between groups. The 3-year cumulative rates of urinary toxicity of Grade ≥1 were 20.4% and 6.9% in Group A and Group B, respectively (p = 0.035).

CONCLUSION

In elderly patients with cervical cancer, 3D-IGBT could be performed safely and effectively and contributed to decreasing urinary toxicity incidence rates.

The Variability of Applicator Position among High Dose Rate Intracavitary Brachytherapy Applications in Cervical Cancer Patients Treated with Ring & Tandem Applicators

Objective

To evaluate the interindividual and intraindividual applicator position variability in high dose rate ring and tandem intracavitary brachytherapy applications in locally advanced cervical cancer.

Patients and Methods

Eight patients with locally advanced cervical cancer formed the study population. They had been treated in Dokuz Eylül University Department of Radiation Oncology between the years 2000 and 2005 with high dose rate intracavitary brachytherapy using ring and tandem applicators. The 3-dimensional geometric variation of the applicator center in craniocaudal, mediolateral and anteroposterior directions was determined on the basis of bony reference points in 24 pairs of orthogonal films obtained in the conventional simulator. Then the following evaluations were performed: 1) the applicator position variability in all applications (interindividual variability), 2) the intraindividual applicator position variability relative to the first application, 3) the intraindividual applicator position variability relative to the average of three applications. Among the potential factors that might influence the reproducibility of ring and tandem applications, age, stage, the period between external radiotherapy and brachytherapy were evaluated by univariate analysis.

Results

Standard deviation of interindividual applicator variability was 3.83 mm in craniocaudal, 0.39 mm in mediolateral and 2.86 mm in anteroposterior directions. The standard deviation of intraindividual variability relative to the first application was 1.91 mm in craniocaudal, 0.4 mm in mediolateral, and 4.26 mm in anteroposterior directions. The standard deviation of intraindividual variability relative to the average of three applications was 0.95 mm in craniocaudal, 1.86 mm in mediolateral, and 1.24 mm in anteroposterior directions. According to univariate analysis, no factor influenced applicator position variability.

Conclusions

In order to extract definitive conclusions about factors that affect positional reproducibility of ring and tandem applicators, studies are needed that include larger numbers of patients.

In-room computed tomography-based brachytherapy for uterine cervical cancer: results of a 5-year retrospective study

Herein, we investigate the long-term clinical outcomes for cervical cancer patients treated with in-room computed tomography-based brachytherapy. Eighty patients with Stage IB1-IVA cervical cancer, who had undergone treatment with combined 3D high-dose rate brachytherapy and conformal radiotherapy between October 2008 and May 2011, were retrospectively analyzed. External beam radiotherapy (50 Gy) with central shielding after 20-40 Gy was performed for each patient. Cisplatin-based chemotherapy was administered concurrently to advanced-stage patients aged ≤75 years. Brachytherapy was delivered in four fractions of 6 Gy per week. In-room computed tomography imaging with applicator insertion was performed for treatment planning. Information from physical examinations at diagnosis, and brachytherapy and magnetic resonance imaging at diagnosis and just before the first brachytherapy session, were referred to for contouring of the high-risk clinical target volume. The median follow-up duration was 60 months. The 5-year local control, pelvic progression-free survival and overall survival rates were 94%, 90% and 86%, respectively. No significant differences in 5-year local control rates were observed between Stage I, Stage II and Stage III-IVA patients. Conversely, a significant difference in the 5-year overall survival rate was observed between Stage II and III-IVA patients (97% vs 72%; P = 0.006). One patient developed Grade 3 late bladder toxicity. No other Grade 3 or higher late toxicities were reported in the rectum or bladder. In conclusion, excellent local control rates were achieved with minimal late toxicities in the rectum or bladder, irrespective of clinical stage.

Dosimetric study for cervix carcinoma treatment using intensity modulated radiation therapy (IMRT) compensation based on 3D intracavitary brachytherapy technique

Purpose

Intensity modulated radiation therapy (IMRT) compensation based on 3D high-dose-rate (HDR) intracavitary brachytherapy (ICBT) boost technique (ICBT + IMRT) has been used in our hospital for advanced cervix carcinoma patients. The purpose of this study was to compare the dosimetric results of the four different boost techniques (the conventional 2D HDR intracavitary brachytherapy [CICBT], 3D optimized HDR intracavitary brachytherapy [OICBT], and IMRT-alone with the applicator in situ).

Material and methods

For 30 patients with locally advanced cervical carcinoma, after the completion of external beam radiotherapy (EBRT) for whole pelvic irradiation 45 Gy/25 fractions, five fractions of ICBT + IMRT boost with 6 Gy/fractions for high risk clinical target volume (HRCTV), and 5 Gy/fractions for intermediate risk clinical target volume (IRCTV) were applied. Computed tomography (CT) and magnetic resonance imaging (MRI) scans were acquired using an in situ CT/MRI-compatible applicator. The gross tumor volume (GTV), the high/intermediate-risk clinical target volume (HRCTV/IRCTV), bladder, rectum, and sigmoid were contoured by CT scans.

Results

For ICBT + IMRT plan, values of D₉₀, D₁₀₀ of HRCTV, D₉₀, D₁₀₀, and V₁₀₀ of IRCTV significantly increased (p < 0.05) in comparison to OICBT and CICBT. The D_2cc values for bladder, rectum, and sigmoid were significantly lower than that of CICBT and IMRT alone. In all patients, the mean rectum V₆₀ Gy values generated from ICBT + IMRT and OICBT techniques were very similar but for bladder and sigmoid, the V₆₀ Gy values generated from ICBT + IMRT were higher than that of OICBT. For the ICBT + IMRT plan, the standard deviations (SD) of D₉₀ and D_2cc were found to be lower than other three treatment plans.

Conclusions

The ICBT + IMRT technique not only provides good target coverage but also maintains low doses (D_2cc) to the OAR. ICBT + IMRT is an optional technique to boost parametrial region or tumor of large size and irregular shape when intracavitary/interstitial brachytherapy cannot be used.

Can combined intracavitary/interstitial approach be an alternative to interstitial brachytherapy with the Martinez Universal Perineal Interstitial Template (MUPIT) in computed tomography-guided adaptive brachytherapy for bulky and/or irregularly shaped gynecological tumors?

Background

Interstitial brachytherapy (ISBT) is an optional treatment for locally advanced gynecological tumours for which conventional intracavitary brachytherapy (ICBT) would result in suboptimal dose coverage. However, ISBT with Martinez Universal Perineal Interstitial Template (MUPIT), in which ~10-20 needles are usually applied, is more time-consuming and labor-intensive than ICBT alone, making it a burden on both practitioners and patients. Therefore, here we investigated the applicability of a combined intracavitary/interstitial (IC/IS) approach in image-guided adaptive brachytherapy for bulky and/or irregularly shaped gynecological tumours for which interstitial brachytherapy (ISBT) was performed.

Methods

Twenty-one consecutive patients with gynecological malignancies treated with computed tomography-guided ISBT using MUPIT were analyzed as cases for this dosimetric study. For each patient, the IC/IS plan using a tandem and 1 or 2 interstitial needles, which was modeled after the combined IC/IS approach, was generated and compared with the IS plan based on the clinical ISBT plan, while the IC plan using only the tandem was applied as a simplified control. Maximal dose was prescribed to the high-risk clinical target volume (HR-CTV) while keeping the dose constraints of D_2cc bladder < 7.0 Gy and D_2cc rectum < 6.0 Gy. The plan with D90 HR-CTV exceeding 6.0 Gy was considered acceptable.

Results

The average D90 HR-CTV was 77%, 118% and 140% in the IC, IC/IS and IS plans, respectively, where 6 Gy corresponds to 100%. The average of the ratio of D90 HR-CTV to D_2cc rectum (gain factor (GF) _rectum) in the IC, IC/IS and IS plans was 0.8, 1.3 and 1.5 respectively, while GF_bladder was 0.9, 1.4 and 1.6, respectively. In the IC/IS plan, D90 HR-CTV, GF_rectum and GF_bladder exceeded 100%, 1.0 and 1.0, respectively, in all patients.

Conclusions

These data demonstrated that the combined IC/IS approach could be a viable alternative to ISBT for gynecological malignancies with bulky and/or irregularly shaped tumours.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-014-0222-6) contains supplementary material, which is available to authorized users.

Comparison of intracavitary brachytherapy and stereotactic body radiotherapy dose distribution for cervical cancer

PURPOSE

To compare the dose distribution characteristics of stereotactic body radiotherapy (SBRT) with intracavitary high-dose-rate (HDR) brachytherapy in patients with cervical carcinoma.

METHODS AND MATERIALS

HDR intracavitary brachytherapy treatment plans for 11 women with cervical carcinoma were evaluated in this analysis. The total HDR brachytherapy dose was 28Gy given in four fractions. HDR brachytherapy was delivered with the microSelectron HDR therapy unit (Nucletron B. V., Veenendaal, The Netherlands). SBRT plans for each patient were generated with MultiPlan for CyberKnife Robotic Radiosurgery System (Accuray Inc., Sunnyvale, CA). The dose distributions, dose-volume histograms, and maximum dose points of the target and critical organs were recorded for both plans.

RESULTS

SBRT yielded significantly better target coverage; the median target coverage for the 100% isodose line was 50.7% for HDR brachytherapy plans, whereas it was 99.1% for SBRT plans. The dose distributions for critical organs were similar in both types of plans. The exceptions were the 25% isodose being significantly better in brachytherapy plans for rectum, and the 100% isodose exposure being higher in brachytherapy plans for rectum, bladder, and sigmoid colon. Some significant differences were also found in maximum doses received by a 2-cc volume of bladder in favor of SBRT plans. In addition, maximum bone marrow doses were significantly higher in SBRT plans.

CONCLUSION

SBRT plans achieved better target coverage and better dose distributions to critical organs except bone marrow compared with HDR brachytherapy plans in patients with locally advanced cervical cancer.

Slice-based plan evaluation methods for three dimensional conformal radiotherapy treatment planning

Dose volume histograms (DVHs) play a vital role in determining the optimal plan for radiotherapy treatment delivery. The current concepts of conformality index (CI), equivalent uniform dose (EUD) derived from dose volume histogram (DVH) does not provide any spatial information. In this study, slice-based evaluation methods have been proposed for spatially analyzing the radiotherapy treatment plans. A case of prostate cancer has been selected for demonstrating the proposed tools for evaluating the dose distribution. Three dimensional conformal radiotherapy treatment planning (3D-CRT) was performed to a dose of 27 Gy/15# with three fields (6 MV anteroposterior and two 15 MV lateral fields) employing multileaf collimator after delivering 45 Gy/25#. The dose was normalized to isocenter and the treatment plan was evaluated with DVH. The dose maximum point, conformality index, planning target volume coverage index (PCI), planning target volume overdose index (POI) and equivalent uniform dose (EUD) were evaluated for every single slice along the cranio-caudal direction for all the planning target volume (PTV) contours and plotted against the slice location. The dose maximum point plotted against the slice position helps in identifying the slices where the dose maximum point is outside the target volume. The plot of conformality index gives the information about the location of those slices where excess of surrounding normal tissues is encompassed inside the prescription isodose. POI quantifies the high dose regions inside the PTV slices that receive doses above 107% of the prescription dose. Similarly, the plot of PCI and EUD with slice position gives the information about those slices where the tumor is not covered adequately. The proposed methods in this study forms as a simpler way to assess the spatial distribution of the dose inside the target volume. It could be used in combination with the current plan evaluation tools and will be very helpful in analyzing the treatment plans.

Image-guided intracavitary high-dose-rate brachytherapy for cervix cancer: A single institutional experience with three-dimensional CT-based planning

PURPOSE

To evaluate and report volumetric dose specification of clinical target volume (CTV) and organs at risk with three-dimensional CT-based brachytherapy. In this study, we analyzed CTV volumes and correlated the dose specification from CT-based volumes with doses at classical point A and International Commission on Radiation Units and Measurements (ICRU) points.

METHODS AND MATERIALS

Ten patients who underwent definitive high-dose-rate brachytherapy for cervical cancer between May 2006 and March 2007 were retrospectively identified for this study. Each patient underwent five intracavitary insertions with CT-compatible ring and tandem applicators using a universal cervical Smit sleeve. Dose of 6.0Gy per fraction was prescribed to the 100% isodose line. The dose distribution was modified using the feature of "geometry optimization" to achieve maximum CTV coverage and to spare the organs at risk. The minimal doses for most irradiated 2, 1, 0.1cm(3) of bladder (D(BV2) , D(BV1), and D(BV0.1)) and rectum (D(RV2), D(RV1), and D(RV0.1)) were determined from dose-volume histograms and were compared with the doses estimated at the ICRU reference points.

RESULTS

The mean CTV of the 10 patients had a shrinkage trend over the five fractions, with a mean of 77.4cm(3) from the first fractions and a mean of 65.5cm(3) from the last fractions (r=-0.911, p=0.031). CTV volumes directly correlated with dose to point A (r=0.785, p=0.007). Eight of 10 patients achieved an average dose received by at least 90% of volume (D(90)) >/=6.0Gy. For bladder, the doses determined from the 3-dimensional (3D) plan correlated significantly with the doses to the ICRU reference bladder point, for example, D(BV2) (r=0.668, p<0.001), D(BV1) (r=0.666, p<0.001), and D(BV0.1) (r=0.655, p<0.001). However, for rectum, the estimated doses to the ICRU reference rectal point did not correlate significantly with doses determined from 3D plan, for example, D(RV2) (r=0.251, p=0.079), D(RV1) (r=0.279, p=0.049), and D(BV0.1) (r=0.282, p=0.047).

CONCLUSIONS

Our experience showed that excellent dose coverage of CTV can be achieved with image-guided CT-based planning with geometric optimization although maximal sparing of rectum was not achieved. Careful dose constraints and standardization of D(90) should be considered when optimizing doses to target tissues such that normal tissue constraints can be met.

Conformal and intensity-modulated radiotherapy for cervical cancer

Three-dimensional radiotherapy planning techniques, including conformal radiotherapy and intensity-modulated radiotherapy, have potential for improving outcomes in cervical cancer. Accurate target volume definition is essential in order to maximise normal tissue sparing while minimising the risk of a geographical miss. This reduction in toxicity provides the option of dose escalation, particularly with simultaneous integrated boost intensity-modulated radiotherapy. The evidence for the current use and potential applications of these techniques in the treatment of cervical cancer are discussed.

Low-dose-rate vs. high-dose-rate intracavitary brachytherapy for carcinoma of the cervix: The University of Alabama at Birmingham (UAB) experience

PURPOSE

To review the clinical outcome retrospectively of cervical cancer patients treated definitively with either high-dose-rate (HDR) or low-dose-rate (LDR) brachytherapy.

METHODS AND MATERIALS

One hundred sixty patients (44 Stage I, 83 Stage II, and 33 Stage III) were treated from 1990 to 2000 with curative intent for carcinoma of the cervix. One hundred three LDR patients were compared to 57 HDR patients. Two groups were treated during the same period. An external beam dose of 45 Gy to the entire pelvis was delivered at 1.8 Gy per fraction to most patients before the first intracavitary insertion in both groups. Brachytherapy was delivered in one to two LDR implants or four to five HDR implants at 6 Gy per fraction. The prescribed dose to Point A for LDR was at least 80-85 Gy. Patient characteristics were similar for each cohort. Point A doses were similar for each stage. The primary endpoints assessed were survivals and failure sites. Endpoints were estimated using the Kaplan-Meier method and comparisons between treatment groups were performed using the log-rank test.

RESULTS

The median followup was 48 months for the LDR group and 59 months for the HDR group. For all stages combined and stage for stage in both groups, there was no statistically significant difference in locoregional control, cause-specific survival, and overall survival for LDR compared with HDR. Locoregional control and overall survival were 78% and 60% for LDR compared to 76% and 55% for HDR at 3 years, respectively (p = 0.96 and p = 0.48). Median cause-specific survival values for LDR vs. HDR were 71 and 81 months, respectively (p = 0.62). The cause-specific survival for LDR patients was 62% compared with 59% for HDR patients at 3 years. For Stage IB2, II, and III LDR patients, cause-specific survival rates were 62%, 67%, and 45%, compared to 67%, 57%, and 33% for HDR at 3 years, respectively (p = 0.75, p = 0.95, and p = 0.48). For patients with a recorded site of first failure, the most common site was locoregional (56%) and then distant metastases (26%). Eight patients who were cancer free developed late complications requiring surgical intervention. Two patients were in the HDR group (3.5%) and 5 in the LDR group (4.8%).

CONCLUSIONS

Similar outcome was observed for LDR compared with HDR intracavitary brachytherapy for the entire cohort. In this review, HDR group was not inferior to LDR group in advanced stages. This is likely because our patients were treated with brachytherapy after a high dose of external pelvic radiotherapy in both LDR and HDR patients.

CT-guided intracavitary radiotherapy for cervical cancer: Comparison of conventional point A plan with clinical target volume-based three-dimensional plan using dose–volume parameters

PURPOSE

To perform an intracavitary radiotherapy (ICR) plan comparison between the conventional point A plan (conventional plan) and computed tomography (CT)-guided clinical target volume-based plan (CTV plan) by analysis of the quantitative dose-volume parameters and irradiated volumes of organs at risk in patients with cervical cancer.

METHODS AND MATERIALS

Thirty plans for 192Ir high-dose-rate ICR after 30-40-Gy external beam radiotherapy were investigated. CT images were acquired at the first ICR session with artifact-free applicators in place. The gross tumor volume, clinical target volume (CTV), point A, and International Commission on Radiation Units and Measurements Report 38 rectal and bladder points were defined on reconstructed CT images. A fractional 100% dose was prescribed to point A in the conventional plan and to the outermost point to cover all CTVs in the CTV plan. The reference volume receiving 100% of the prescribed dose (V(ref)), and the dose-volume parameters of the coverage index, conformal index, and external volume index were calculated from the dose-volume histogram. The bladder, rectal point doses, and percentage of volumes receiving 50%, 80%, and 100% of the prescribed dose were also analyzed.

RESULTS

Conventional plans were performed, and patients were categorized on the basis of whether the 100% isodose line of point A prescription dose fully encompassed the CTV (Group 1, n = 20) or not (Group 2, n = 10). The mean gross tumor volume (11.6 cm3) and CTV (24.9 cm3) of Group 1 were smaller than the corresponding values (23.7 and 44.7 cm3, respectively) for Group 2 (p = 0.003). The mean V(ref) for all patients was 129.6 cm(3) for the conventional plan and 97.0 cm3 for the CTV plan (p = 0.003). The mean V(ref) in Group 1 decreased markedly with the CTV plan (p < 0.001). For the conventional and CTV plans in all patients, the mean coverage index, conformal index, and external volume index were 0.98 and 1.0, 0.23 and 0.34, and 3.86 and 2.15, respectively. Statistical analysis showed that the conformal index and external volume index improved significantly with the CTV plan, and this improvement was more marked in Group 1. The mean values of the bladder and rectal point doses and volume fractions receiving 50%, 80%, and 100% of the reference dose did not differ between plans for all patients. The reduction in the mean rectal and bladder point doses and irradiated volumes for the CTV plan was statistically significant in Group 1.

CONCLUSION

Computed tomography-guided CTV planning of ICR is superior to conventional point A planning in terms of conformity of target coverage and avoidance of overdosed normal tissue volume. To ascertain the potential benefit of treatment outcome, ICR with image-guided three-dimensional plans will be pursued and correlated with the dose-volume parameters.

From 'points' to 'profiles' in intracavitary brachytherapy of cervical cancer

PURPOSE OF REVIEW

This article reviews some recent developments that have occurred with the widespread use of imaging modalities during intracavitary brachytherapy in cervical cancer.

RECENT FINDINGS

The practice of dose prescription with intracavitary brachytherapy continues to be largely based on the traditional hypothetical point - point A. Recent studies have indicated that significant uncertainties could result with such point dose prescriptions. Gradually a shift is perceived towards the incorporation of target and normal structure outlines for dose prescription and treatment planning during intracavitary brachytherapy.

SUMMARY

Dose prescriptions during brachytherapy could be framed with certainty if various imaging modalities are integrated during the intracavitary procedure. With the availability of computerized tomography/magnetic resonance imaging-compatible applicators, dose prescriptions and distributions could be based on either anatomical images of the diseased and normal organs obtained from computerized tomography or magnetic resonance imaging studies or on anatometabolic images after co-registration of the anatomical and functional images obtained from computerized tomography/magnetic resonance imaging and positron emission tomography. A shift from traditional two-dimensional 'points' to three-dimensional 'profiles' for targets and normal tissue doses could be expected in the near future with the use of image-guided intracavitary brachytherapy in cervical cancer.

Fractionated stereotactic radiotherapy boost for gynecologic tumors: an alternative to brachytherapy?

PURPOSE

A brachytherapy (BT) boost to the vaginal vault is considered standard treatment for many endometrial or cervical cancers. We aimed to challenge this treatment standard by using stereotactic radiotherapy (SRT) with a linac-based micromultileaf collimator technique.

METHODS AND MATERIALS

Since January 2002, 16 patients with either endometrial (9) or cervical (7) cancer have been treated with a final boost to the areas at higher risk for relapse. In 14 patients, the target volume included the vaginal vault, the upper vagina, the parametria, or (if not operated) the uterus (clinical target volume [CTV]). In 2 patients with local relapse, the CTV was the tumor in the vaginal stump. Margins of 6-10 mm were added to the CTV to define the planning target volume (PTV). Hypofractionated dynamic-arc or intensity-modulated radiotherapy techniques were used. Postoperative treatment was delivered in 12 patients (2 x 7 Gy to the PTV with a 4-7-day interval between fractions). In the 4 nonoperated patients, a dose of 4 Gy/fraction in 5 fractions with 2 to 3 days' interval was delivered. Patients were immobilized in a customized vacuum body cast and optimally repositioned with an infrared-guided system developed for extracranial SRT. To further optimize daily repositioning and target immobilization, an inflated rectal balloon was used during each treatment fraction. In 10 patients, CT resimulation was performed before the last boost fraction to assess for repositioning reproducibility via CT-to-CT registration and to estimate PTV safety margins around the CTV. Finally, a comparative treatment planning study between BT and SRT was performed in 2 patients with an operated endometrial Stage I cancer.

RESULTS

No patient developed severe acute urinary or low-intestinal toxicity. No patient developed urinary late effects (>6 months). One patient with a vaginal relapse previously irradiated to the pelvic region presented with Grade 3 rectal bleeding 18 months after retreatment. A second patient known to suffer from irritable bowel syndrome presented with Grade 1 abdominal pain after treatment. The estimated PTV margins around the CTV were 9-10 mm with infrared marker registration. External SRT succeeded in improving dose homogeneity to the PTV and in reducing the maximum dose to the rectum, when compared to BT.

CONCLUSION

These results suggest that the use of external SRT to deliver a final boost to the areas at higher risk for relapse in endometrial or cervical cancer is feasible, well tolerated, and may well be considered an acceptable alternative to BT.

Problems and uncertainties with multiple point A's during multiple high-dose-rate intracavitary brachytherapy in carcinoma of the cervix

AIMS

This study evaluates the consequences of point A as a dose prescription point during multiple high-dose-rate (HDR) intracavitary brachytherapy (ICBT) in cancer cervix.

MATERIALS AND METHODS

Fifty patients who had received teletherapy were randomised into two groups of 25 to receive three HDR ICBT fractions of 6 Gy each at point A with either a flexible Ralstron (Shimadzu Corporation, Japan) or rigid Rotterdam (Nucletron, Netherlands) applicator. The orthogonal radiographs of the 150 applications were evaluated for applicator geometry and point A co-ordinates.

RESULTS

Irrespective of the nature and rigidity of the applicators, its various components exhibited a highly significant variation during multiple fractionated HDR ICBT. The Cartesian co-ordinates of point A (left and right) for the applicator geometry also showed significant variation during multiple HDR ICBT procedures. This resulted in an average shift of 9.5 mm (SD= +/-4.4) and 11.1 mm (SD= +/-6.4) in right point A, 10.2 mm (SD= +/-4.5) and 10.8 mm (SD= +/-6.6) in left point A for Ralstron and Rotterdam applicator, respectively, during the three HDR ICBT. Consequently, doses to both right and left point A's showed significant variation during multiple ICBT application and were independent of the applicator type.

CONCLUSION

Applicator variation in the components and spatial position in the pelvis during multiple HDR ICBT results in multiple point A's irrespective of the nature of applicator, leading to uncertainty in the dose prescription. These uncertainties, which have a bearing on clinical end points, could be minimised by shifting from point-based dose prescription to image-based target localisation and treatment planning in ICBT.

The impact of sectional imaging on dose escalation in endocavitary HDR-brachytherapy of cervical cancer: results of a prospective comparative trial

PURPOSE

The purpose of this comparative prospective study was to assess the effect of CT and MR based individualisation and adaptation on the dose distribution in the target volume and organs at risk compared to a radiography based procedure.

MATERIAL AND METHODS

In 15 patients MR scans, in 10 patients additional axial CT-scans with compatible tube-ring applicator in situ were performed and digitally transferred to the PLATO(R) planning system. Considering clinical examination and MR-scan before radiotherapy individual 3-D dose distribution was calculated and adapted based on (1) two orthogonal radiographs; (2) isodoses superimposed on the CT images; and (3) isodoses superimposed on the MR images. Adaptation was strictly limited by the dose level at 2 cm(3) bladder or rectum volume (D(2)) to allow comparison of CT and MR plans. All three individualised dose distributions were superimposed on the MR images and cumulative dose-volume histograms were calculated for comparison.

RESULTS

3-D individualisation based on sectional imaging enabled higher dose to the target volume (isodose enclosing 95% of the CTV=CTV(95)) compared to individualised treatment plans based on orthogonal radiographs by a mean factor of 1.2 (1-1.7). The dose to bladder and/or rectum wall was at the same time not increased beyond the prescribed tolerance level (71% of the prescribed target dose). In a subgroup of 10 patients MRI based treatment plans were superior to CT based treatment plans allowing for a higher dose (138% vs. 124%).

CONCLUSION

Sectional imaging based treatment planning, in particular using MR, was superior to radiography allowing for a clinical meaningful dose escalation without increasing the dose to bladder and rectum beyond the tolerance level.

Long-term results of proton beam therapy for carcinoma of the uterine cervix

PURPOSE

To determine the role of proton therapy in patients with carcinoma of the uterine cervix.

METHODS AND MATERIALS

Between 1983 and 1991, 25 patients with squamous cell carcinoma of the uterine cervix (stages IIB-IVA) were treated with a curative intent by external photon irradiation to the pelvis, followed by proton irradiation to the primary tumor, delivering a median total tumor dose of 86 Gy (range 71 Gy/26 Fr-101 Gy/46 Fr), and were followed for a median period of 139 months (range 11-184 months).

RESULTS

Ten-year overall survival rates for stages IIB and IIIB/IVA patients were 89% and 40%, respectively. Five-year local control rates for stages IIB and IIIB/IVA patients were 100% and 61%, respectively. Four percent of patients experienced severe (Grade 4 or more) late complications in the intestine or urinary bladder at 5 years.

CONCLUSION

External photon and proton therapy is effective for those who are not eligible for intracavitary irradiation, and who otherwise have a poor prognosis. The results show that tumor control, survival, and morbidity are similar to those after conventional therapy.

Radiography-based treatment planning compared with computed tomography (CT)-based treatment planning for intracavitary brachytherapy in cancer of the cervix: Analysis of dose-volume histograms

PURPOSE

To analyze the dose-volume histograms (DVHs) of the tumor volume and organs at risk by CT-based treatment planning compared with conventional radiography-based treatment planning for intracavitary brachytherapy in cancer of the cervix.

METHODS AND MATERIALS

Fifteen consecutive patients with cancer of the cervix (1 IB1, 3 IB2, 7 IIB, 4 IIIB) were treated with plastic CT-compatible HDR intracavitary applicators and underwent postimplant pelvic CT scans with applicators in place. CT-images were transferred to the PLATO treatment planning system. The gross tumor volume (GTV) and organs at risk were digitized. Dwell positions in the uterine tandem and colpostats were identified and registered for each patient. All patients were treated with 6 Gy per fraction to Point A using radiography-based planning. For the CT-based planning, DVHs were performed for the GTV, bladder, rectum, sigmoid colon, and small bowel in the pelvis. The dose delivered to 3% volume of the organs at risk (D3%) was compared with the respective ICRU reference doses.

RESULTS

For stage IB(I), IB2, IIB, and IIIB disease the mean GTV was 20.5 cc, 56.6 cc (54.2-57.2), 63.7 cc (55.4-118.9), and 77.6 cc (49.4-102.9), respectively. The 6 Gy pear-shaped volume (PSV) encompassed an average GTV of 98.5%, 89.5%, 79.5%, and 59.5% for stages IBI, IB2, IIB, and IIIB, respectively. The mean dose for the ICRU bladder point and D3% was 3.72 Gy (1.51-5.53) and 4.74 Gy (1.70-10.10), respectively. The mean dose for the ICRU rectal point and D3% was 3.97 Gy (2.09-5.37) and 3.52 Gy (2.05-4.08), respectively. The D3% for the sigmoid colon was highest (3.88 Gy), followed by the rectum (3.52 Gy), and the small bowel (3.36 Gy).

CONCLUSION

Radiography-based conventional treatment planning overestimates tumor dose, especially those with more advanced tumors. To correlate DVHs for tumor control, improved tumor imaging is necessary.

Image fusion of CT and MRI data enables improved target volume definition in 3D-brachytherapy treatment planning

PURPOSE

To integrate MRI into CT-based 3D-brachytherapy treatment planning using a software system for image registration and fusion.

METHODS AND MATERIALS

Sixteen patients with recurrent head-and-neck cancer, vulvar cancer, liposarcoma, and cervical cancer were treated with interstitial (n=12) and endocavitary (n=4) brachytherapy. CT and MRI scans were performed after implantation and prior to treatment planning. Image registration to integrate the CT and MR information into a single geometric framework was performed using a software algorithm based on mutual information. Conventional 3D-brachytherapy planning based on CT-information alone was compared to brachytherapy planning based on fused CT and MRI data. The accuracy of the image fusion was measured using predefined corresponding landmarks in the CT and MRI data.

RESULTS

The presented automated algorithm proved to be robust and reliable (mean registration error 1.8 mm, range 0.8-4.1 mm, SD 0.9 mm). Tumor visualization was difficult using CT alone in all cases. Brachytherapy treatment planning based on fused CT and MRI data enabled better definition of target volume and risk structures as compared to treatment planning based on CT alone.

CONCLUSIONS

Image registration and fusion is feasible for afterloading brachytherapy treatment planning. Treatment planning based on fused CT and MRI data resulted in improved target volume and risk structure definition.

[Radiotherapy for tumors of the uterine cervix. Gross tumor volume and clinical target volume]

Treatment of carcinoma of the uterine cervix needs a multidisciplinary approach. External irradiation and brachytherapy are highly curative because of the tumor radiosensitivity. The main prognostic factors are tumoral volume and nodal involvement. Tumoral extent is evaluated by diagnostic MR imaging, and gynecological exam. Nodal involvement can be assessed, accurately by coelioscopic pelvic node sampling and by imaging modalities such as CT scan. The knowledge of these two factors helps to choose the treatment strategy. The use of imaging (MRI and CT) added to clinical findings allows to design external irradiation fields. 3D treatment planning in external irradiation and brachytherapy is based upon the use of imaging (CT and MRI). It leads to a better knowledge of dose distribution to the target and critical organs and allows more individualized and conformal treatment.

Inter fraction variations in rectum and bladder volumes and dose distributions during high dose rate brachytherapy treatment of the uterine cervix investigated by repetitive CT-examinations

PURPOSE

To evaluate variation of dose to organs at risk for patients receiving fractionated high dose rate gynaecological brachytherapy by using CT-based 3D treatment planning and dose-volume histograms (DVH).

MATERIALS AND METHODS

Fourteen patients with cancer of the uterine cervix underwent three to six CT examinations (mean 4.9) during their course of high-dose-rate brachytherapy using radiographically compatible applicators. The rectal and bladder walls were delineated and DVHs were calculated.

RESULTS

Inter fraction variation of the bladder volume (CV(mean)=44.1%) was significantly larger than the inter fraction variation of the mean dose (CV(mean)=19.9%, P=0.005) and the maximum dose (CV(mean)=17.5%, P=0.003) of the bladder wall. The same trend was seen for rectum, although the figures were not significantly different. Performing CT examinations at four of seven brachytherapy fractions reduced the uncertainty to 4 and 7% for the bladder and rectal doses, respectively. A linear regression analysis showed a significant, negative relationship between time after treatment start and the whole bladder volume (P=0.018), whereas no correlation was found for the rectum. For both rectum and bladder a linear regression analysis revealed a significant, negative relationship between the whole volume and median dose (P<0.05).

CONCLUSION

Preferably a CT examination should be provided at every fraction. However, this is logistically unfeasible in most institutions. To obtain reliable DVHs the patients will in the future undergo 3-4 CT examinations during the course of brachytherapy at our institution. Since this study showed an association between large bladder volumes and dose reductions, the patients will be treated with a standardized bladder volume.

HDR brachytherapy applied to cervical carcinoma with moderate lateral expansion: modified principles of treatment

BACKGROUND AND PURPOSE

In order to meet the deficiencies of endocavitary applications, a combined technique was introduced with the aim of achieving better target coverage for improvement of loco-regional tumour control. In high dose rate (HDR) endocavitary applications with tandem and ovoids, enlargement of the distance between the ovoids, shifting of dwell times and also optimization often fail to achieve sufficient expansion of the cervical parametrial area encompassed by the reference isodose.

MATERIALS AND METHODS

The Deventer method, whereby HDR endocavitary and HDR interstitial brachytherapy are applied in the same session, was applied for tumours with a lateral expansion of 25 mm or more from the axis of the cervical canal. For the addition of HDR interstitial brachytherapy, each ovoid was provided with a channel which allowed insertion of an afterloading needle into the cervix up to a fixed depth. The dose specifications and dosimetry in neighbouring organs are presented in detail.

RESULTS

Seventy-six combined applications were given to 41 patients. The follow-up averaged at 23 months, with a maximum of 59 months. No severe early or persistent late complications were observed. In stage IIB tumours, the most important evaluation of the merits of this technique, the disease-free 3-year survival determined with the Kaplan-Meier method was 75% (n=20).

CONCLUSIONS

The Deventer method of HDR endocavitary and HDR interstitial brachytherapy applied in the same session is a feasible method for enlargement of the reference isodose envelope in the cervical parametrial area. The 3-year disease-free survival in stage IIB patients and the low complication rates in all stages together, justify its continuation.

Inter-observer variation in delineation of bladder and rectum contours for brachytherapy of cervical cancer

BACKGROUND AND PURPOSE

In 3D treatment planning of low dose rate brachytherapy of cervical carcinoma the dose in bladder and rectum can be estimated from dose-volume histograms (DVHs). In this study, the influence of inter-observer variation in delineation of bladder and rectum on DVHs and dose at specific bladder and rectum points was investigated.

MATERIALS AND METHODS

Three observers delineated bladder and rectum on axial CT images of ten patients. The highest minimum dose in bladder and rectum was determined for, respectively, 2 cm(3) (D(2)) and 5 cm(3) (D(5)), as well as the dose at specific points placed on the bladder and rectum wall.

RESULTS

The inter-observer variation in D(2) was 10% (1 average relative SD) in bladder and 11% (1 SD) in rectum. In D(5) the variation was 8% (1 SD) in bladder and 11% in rectum. The variation in the bladder point was 13% (1 SD) and in the rectum point 11% (1 SD). Differences in delineation among the observers were caused by unclear organ boundaries on the CT images.

CONCLUSIONS

Taking the inter-observer variation caused by delineation differences into account, dose in bladder and rectum can be determined within an accuracy of about 10% (1 SD).

[Contribution of imaging in radiotherapy planning in uterine cervix cancers]

External irradiation and brachytherapy are curative in the treatment of carcinoma of the cervix. The aim of radiotherapy is to optimize the irradiation of the target volume and to reduce the dose to critical organs. The use of imaging (computed tomography and magnetic resonance imaging added to clinical findings and standard guidelines) are studied in the treatment planning of external irradiation and brachytherapy in carcinoma of the cervix. Imaging allows an individualized and conformal treatment planning.

Analysis of the relationship between tumor dose inhomogeneity and local control in patients with skull base chordoma

PURPOSE

When irradiating a tumor that abuts or displaces any normal structures, the dose constraints to those structures (if lower than the prescribed dose) may cause dose inhomogeneity in the tumor volume at the tumor-critical structure interface. The low-dose region in the tumor volume may be one of the reasons for local failure. The aim of this study is to quantitate the effect of tumor dose inhomogeneity on local control and recurrence-free survival in patients with skull base chordoma.

METHODS AND MATERIALS

132 patients with skull base chordoma were treated with combined photon and proton irradiation between 1978 and 1993. This study reviews 115 patients whose dose-volume data and follow-up data are available. The prescribed doses ranged from 66.6 Cobalt-Gray-Equivalent (CGE) to 79.2 CGE (median of 68.9 CGE). The dose to the optic structures (optic nerves and chiasm), the brain stem surface, and the brain stem center was limited to 60, 64, and 53 CGE, respectively. We used the dose-volume histogram data derived with the three-dimensional treatment planning system to evaluate several dose-volume parameters including the Equivalent Uniform Dose (EUD). We also analyzed several other patient and treatment factors in relation to local control and recurrence-free survival.

RESULTS

Local failure developed in 42 of 115 patients, with the actuarial local control rates at 5 and 10 years being 59% and 44%. Gender was a significant predictor for local control with the prognosis in males being significantly better than that in females (P = 0.004, hazard ratio = 2.3). In a Cox univariate analysis, with stratification by gender, the significant predictors for local control (at the probability level of 0.05) were EUD, the target volume, the minimum dose, and the D5cc dose. The prescribed dose, histology, age, the maximum dose, the mean dose, the median dose, the D90% dose, and the overall treatment time were not significant factors. In a Cox multivariate analysis, the models including gender and EUD, or gender and the target volume, or gender and the minimum target dose were significant. The more biologically meaningful of these models is that of gender and EUD.

CONCLUSION

This study suggests that the probability of recurrence of skull base chordomas depends on gender, target volume, and the level of target dose inhomogeneity. EUD was shown to be a useful parameter to evaluate dose distribution for the target volume.

Computed tomography analysis of causes of local failure in radiotherapy for cervical carcinoma

BACKGROUND

The authors analyzed the radiation dose to the periphery of the cervix and area of the cervix in relation to local failure of radiotherapy for carcinoma of the cervix using computed tomography (CT) images.

METHODS

Between 1981-1990, 127 consecutive patients were treated with definitive radiotherapy. Ninety-nine of these patients had CT images taken at the time of intracavitary therapy. Of these 99 patients, 80 were eligible for this analysis. After CT scanning, isodose curves relative to the point A dose were superimposed on the CT images. The minimum percent dose and minimum dose at the periphery of the cervix were estimated. The area of the cervix also was measured. These factors were examined in relation to the local tumor control rate.

RESULTS

Histograms of both the minimum percent dose and the cervical area showed significant differences between the local control and local failure groups (P <0.001). The local control rates were related to both the minimum percent dose and the cervical area, and differed significantly over and below the values of 60% and 18 cm2 (P <0.001 each), respectively. The local control patients, over and below the line: Y = -0.220X + 21.2, in which X (gray [Gy]) and Y (Gy) are the whole pelvis dose and the minimum dose, respectively, could be well differentiated with significance (91.7% vs. 25.0%; P <0.001).

CONCLUSIONS

Computed tomography analysis indicated that the local tumor control rate was related strongly to the minimum percent dose, the cervical area, and the pair of whole pelvis and minimum dose values. These factors were found to be more useful than the point A dose in predicting local tumor control.

Definitive radiotherapy combined with high-dose-rate brachytherapy for Stage III carcinoma of the uterine cervix: retrospective analysis of prognostic factors concerning patient characteristics and treatment parameters

PURPOSE

To assess treatment outcome after definitive radiotherapy for Stage III cervical carcinoma retrospective analysis of the clinical data was performed.

METHODS AND MATERIALS

We enrolled 265 patients with Stage III cervical carcinoma who were treated with combined external beam radiotherapy [mean +/- standard deviation (SD), 50.3 +/- 1.8 Gy; range 40-70) and intracavitary brachytherapy (ICBT) (mean +/- SD, 19.8 +/- 2.4 Gy; range 10-32) using a high-dose-rate 60Co source. We retrospectively analyzed, as measures of the therapeutic outcome, the overall survival rate (OAS), relapse-free survival rate (RFS), locoregional event-free rate (LREF), distant metastasis (DM), and late complication.

RESULTS

The 5-year OAS, RFS, and LREF rates (n = 265) were 50.7%, 57.1%, and 71.2%, respectively. Univariate analysis revealed a significant favorable effect on the OAS rate for complete response (CR) (p = 0.024), maximum tumor diameter < 6 cm (SML) (p = 0.0009), Karnofsky performance score > or =70 (p = 0.046), age <75 years (p = 0.0043), hemoglobin (Hb) concentration of > or =9 g/dl (p = 0.0005), and histopathological diagnosis of squamous cell carcinoma (SCC) (p = 0.0089). In the multivariate analysis, Hb, SCC, SML, and CR remained significant prognostic factors. In both univariate and multivariate analysis, SML, Hb, age, and SCC showed significant effects on the RFS rate. Age > or =60 years (p = 0.017), Hb > or =9 g/dl (p = 0.0039), and SML (p = 0.0046) were significant favorable prognostic factors for the LREF rate identified by univariate analysis. In addition, advanced age, SML, and SCC showed significant beneficial effects on the LREF rate in the multivariate analysis. DM developed in 21.1% of patients, and the groups with Hb < 9 g/dl (p < 0.005), Karnofsky performance score of <70 (p < 0.001), and dose at point A in the ICBT < 16 Gy (p < 0.005) developed a significantly greater incidence of DM than did the groups without. The 5-year incidence was 2.6% for major bladder complication and 8.3% for major rectal complication. The radiation dose in the subgroup with rectal complication was significantly greater than that in the subgroup without complications.

CONCLUSION

In patients with Stage III cervical carcinoma, tumor size, concentration of Hb, and histopathological diagnosis are strong prognostic factors for the therapeutic outcome. The ICBT dose in our study was small compared to the reported data, but the outcome was quite comparable. Thus, the dose we used might be the minimum required. However, locoregional control still remains an important problem. It is necessary to attain the optimal dose distribution in both the target volume and in critical organs. In high-risk patients, combined use of chemotherapy is crucial to improve the response to radiation.