Assessment of Organ Motion in Postoperative Endometrial and Cervical Cancer Patients Treated With Intensity-Modulated Radiation Therapy

Dosimetric impact of rotational setup errors in volumetric modulated arc therapy for postoperative cervical cancer

We aimed to evaluate the impact of rotational setup errors on the doses received during postoperative volumetric-modulated arc therapy (VMAT) for cervical cancer. Overall, 121 cone-beam computed tomography (CBCT) sets from 20 patients were rigidly registered to reference computed tomography (CT) sets based on bony landmarks. The rotational setup errors (pitch, yaw and roll) were calculated. Then, 121 CT sets involving rotational setup errors were created, and the dose distribution in these CT sets were recalculated. The recalculated dosimetric parameters for the clinical target volume (CTV) and organs at risk (OAR) were compared to the reference values, and the correlation coefficients between the dosimetric parameter differences and rotational setup errors were calculated. Only the pitch setup error was moderately correlated with CTV coverage (r ≥ 0.40) and strongly correlated with V45 for the bladder (r ≥ 0.91) and V40 for the rectum, small bowel and bone marrow (r ≥ 0.91). The maximum dosimetric difference in a single fraction and overall fractions was -1.59% and -0.69% in D98 for the CTV, 11.72% and 5.17% in V45 for the bladder and -8.03% and -4.68% in V40 for the rectum, respectively. In conclusion, rotational setup errors only slightly impact dose coverage during postoperative cervical cancer VMAT. However, the pitch setup error occasionally affected the doses received by the bladder or the rectum in the overall fraction when the error was systematic. Thus, rotational setup errors should be corrected by adjusting six-degree-of-freedom (DOF) couches to reduce dosimetric differences in the OARs.

Impact of a fiducial marker based ART strategy on margins in postoperative IMRT of gynecological tumors

PURPOSE

To investigate the potential of an offline Adaptive Radiotherapy (ART) strategy, based on the interfractional vagina motion (IVM) measured using fiducial markers (FM) during an initial number of fractions, on the CTV to PTV margins in post-operative gynecological patients.

MATERIALS AND METHODS

In 18 patients, treated post-operatively for gynecological tumors, the systematic residual IVM was quantified after simulating an offline ART procedure, utilizing the average IVM measured with FM for a varying initial numbers of fractions to find the optimal moment to adapt the treatment plan and a threshold for selecting patients for replanning. Clinical margins for a zero, 2 and 5 mm threshold based strategy were calculated to assess the possible margin reduction.

RESULTS

Applying an ART strategy based on the average IVM of the initial 5 fractions reduces the systematic IVM significantly (P < 0.025), allowing a reduction of the clinical margin of 3 mm (20%) in the CC direction and 2 mm (13%) in the AP direction. A 2 mm threshold for selecting patients for replanning shows no difference in the reduction of the clinical margin, but reduces the workload with 12%.

CONCLUSION

An ART strategy based on adapting on the average IVM during the initial 5 fractions of treatment provides an opportunity to reduce the CTV to PTV margins in postoperative gynecological tumors. To keep the workload in balance with the best achievable margin reduction, a threshold for selecting patients for plan adaptation is recommended.

Overview of patient preparation strategies to manage internal organ motion during radiotherapy in the pelvis

Introduction:

Pelvic internal organs change in volume and position during radiotherapy. This may compromise the efficacy of treatment or worsen its toxicity. There may be limitations to fully correcting these changes using online image guidance; therefore, effective and consistent patient preparation and positioning remain important. This review aims to provide an overview of the extent of pelvic organ motion and strategies to manage this motion.

Methods and Materials:

Given the breadth of this topic, a systematic review was not undertaken. Instead, existing systematic reviews and individual high-quality studies addressing strategies to manage pelvic organ motion have been discussed. Suggested levels of evidence and grades of recommendation for each strategy have been applied.

Results:

Various strategies to manage rectal changes have been investigated including diet and laxatives, enemas and rectal emptying tubes and rectal displacement with endorectal balloons (ERBs) and rectal spacers. Bladder-filling protocols and bladder ultrasound have been used to try to standardise bladder volume. Positioning the patient supine, using a full bladder and positioning prone with or without a belly board, has been examined in an attempt to reduce the volume of irradiated small bowel. Some randomised trials have been performed, with evidence to support the use of ERBs, rectal spacers, bladder-filling protocols and the supine over prone position in prostate radiotherapy. However, there was a lack of consistent high-quality evidence that would be applicable to different disease sites within the pelvis. Many studies included small numbers of patients were non-randomised, used less conformal radiotherapy techniques or did not report clinical outcomes such as toxicity.

Conclusions:

There is uncertainty as to the clinical benefit of many of the commonly adopted interventions to minimise pelvic organ motion. Given this and the limitations in online image guidance compensation, further investigation of adaptive radiotherapy strategies is required.

Prospective observational study on the safety of an original fiducial marker insertion for radiotherapy in gynecological cancer by a simple method

Our observational study aimed to verify the safety of our original titanium fiducial markers in gynecological cancer by using a simple insertion method. We prospectively evaluated the safety in patients with gynecological cancer who had undergone our insertion procedure of the titanium markers. The decision to implant a titanium marker was at the discretion of each radiation oncologist. The fiducial markers were manufactured by severing ligating clips for surgery into 3-6 mm pieces and were sterilized thereafter. We inserted an 18-gauge injection needle containing the marker before the marker was extruded by a 22-gauge Cattelan needle or shape memory alloy wire into the tumor or tissues close to the tumor. Severe complications within 3 months after implantation were scored according to the National Cancer Institute's Common Terminology Criteria for Adverse Events version 4.0. Between August 2016 and December 2018, we enrolled 46 patients. Of 46, 44 underwent implantation. The median age was 58.5 years. The most common primary site was the cervix. Two patients experienced detachment of the markers after implantation. No Grade 3 or higher level of complications was observed. Our simple insertion technique for original titanium fiducial markers was well-tolerated.

Geometric and dosimetric evaluation of the differences between rigid and deformable registration to assess interfraction motion during pelvic radiotherapy

BACKGROUND AND PURPOSE

Appropriate internal margins are essential to avoid a geographical miss in intensity-modulated radiation therapy (IMRT) for endometrial cancer (EC). This study evaluated interfraction target motion using rigid and non-rigid approximation strategies and calculated internal margins based on random and systematic errors using traditional rigid margin recipes. Dosimetric impact of target motion was also investigated.

MATERIALS AND METHODS

Cone beam CTs (CBCTs) were acquired days 1-4 and then weekly in 17 patients receiving adjuvant IMRT for EC; a total of 169 CBCTs were analysed. Interfraction motion for the clinical target volume vaginal vault and upper vagina (CTVv) was measured using bony landmarks and deformation vector field displacement (DVFD) within a 1 mm internal wall of CTVv. Patient and population systematic and random errors were estimated and margins calculated. Delivered dose to the CTVv and organs at risk was estimated.

RESULTS

There was a significant difference in target motion assessment using the different registration strategies (p < 0.05). DVFD up to 30 mm occurred in the anterior/posterior direction, which was not accounted for in PTV margins using rigid margin recipes. Underdosing of CTVv D95% occurred in three patients who had substantial reductions in rectal volume (RV) during treatment. RV relative to the planning CT was moderately correlated with anterior/posterior displacement (r = 0.6) and mean relative RV during treatment was strongly correlated with mean relative RV at CBCT acquired days 1-3 (r = 0.8).

CONCLUSION

Complex and extensive geometric changes occur to the CTVv, which are not accounted for in margin recipes using rigid approximation. Contemporary margin recipes and adaptive treatment planning based on non-rigid approximation are recommended.

Image-guided radiation therapy for post-operative gynaecologic cancer: patient set up verification with and without implanted fiducial markers

BACKGROUND

Intensity modulated radiotherapy (IMRT) is increasingly being used to treat gynaecological malignancies in the postoperative setting. The purpose of this study was to evaluate the use of image-guided radiotherapy (IGRT) using cone-beam computed tomography (CBCT) with fiducial markers for daily localization.

MATERIAL AND METHODS

A single institution study was performed of consecutive cervical or endometrial cancer patients receiving adjuvant external beam radiotherapy (n = 15). Patients were set up at treatment using daily CBCT and alignment of implanted fiducial markers. Image registration was retrospectively completed based on soft tissue matching and the resulting couch shifts from each IGRT method were compared (n = 122).

RESULTS

The median shift between IGRT methods was 2 mm, 1 mm and 1 mm in the anterior-posterior (A-P), superior-inferior (S-I), and lateral directions, respectively. The largest deviations were observed in the A-P direction; however, more than 90% were within 5 mm and 63.9% were within 2.5 mm.

CONCLUSIONS

IGRT based on soft tissue match provides a noninvasive convenient method for daily localization and is accurate within treatment uncertainty for the majority of cases.

Positional uncertainty of vaginal cuff and feasibility of implementing portable bladder scanner in postoperative cervical cancer patients

PURPOSE

To propose a geometrical margin for definition of the vaginal cuff PTV using only CT images of the full bladder (CT_full) in postoperative cervical cancer patients.

METHODS

Twenty-nine operated cervical cancer patients underwent volumetric arc therapy with a bladder filling protocol. This study assessed bladder filling using a portable bladder scanner and cone-beam computed tomography (CBCT) during the entire treatment period. The measured bladder volumes with a BladderScan® were compared with the delineated volume on CBCT. Titanium clips in the vaginal cuff were analysed to assess geometrical uncertainty and the influence of rectal and bladder volume changes.

RESULTS

BladderScan® showed good agreement with the delineated volume (R = 0.80). The volume changes in the bladder have a greater influence on the clip displacements than in the rectum. The 95th percentile of uncertainty of the clips in reference to CT_full in the right-left (RL), the superoinferior (SI), and the anteroposterior (AP) was 0.32, 0.65, and 1.15 cm, respectively. From this result and intra-fractional movements of the vaginal cuff reported by Haripotepornkul, a new geometrical margin was proposed for definition of the vaginal cuff planning target volume (PTV): 0.5, 0.9, and 1.4 cm in the RL, SI, and AP directions, respectively.

CONCLUSIONS

A new geometrical margin was proposed for definition of the vaginal cuff PTV based on CT_full, which will be needless of empty bladder at the planning CT scan. This method allows patients to reduce the burden and efficient routine CT scans can be improved.

Rectal balloon use limits vaginal displacement, rectal dose, and rectal toxicity in patients receiving IMRT for postoperative gynecological malignancies

Pelvic radiotherapy for gynecologic malignancies traditionally used a 4-field box technique. Later trials have shown the feasibility of using intensity-modulated radiotherapy (IMRT) instead. But vaginal movement between fractions is concerning when using IMRT due to greater conformality of the isodose curves to the target and the resulting possibility of missing the target while the vagina is displaced. In this study, we showed that the use of a rectal balloon during treatment can decrease vaginal displacement, limit rectal dose, and limit acute and late toxicities. Little is known regarding the use of a rectal balloon (RB) in treating patients with IMRT in the posthysterectomy setting. We hypothesize that the use of an RB during treatment can limit rectal dose and acute and long-term toxicities, as well as decrease vaginal cuff displacement between fractions. We performed a retrospective review of patients with gynecological malignancies who received postoperative IMRT with the use of an RB from January 1, 2012 to January 1, 2015. Rectal dose constraint was examined as per Radiation Therapy Oncology Group (RTOG) 1203 and 0418. Daily cone beam computed tomography (CT) was performed, and the average (avg) displacement, avg magnitude, and avg magnitude of vector were calculated. Toxicity was reported according to RTOG acute radiation morbidity scoring criteria. Acute toxicity was defined as less than 90 days from the end of radiation treatment. Late toxicity was defined as at least 90 days after completing radiation. Twenty-eight patients with postoperative IMRT with the use of an RB were examined and 23 treatment plans were reviewed. The avg rectal V40 was 39.3% ± 9.0%. V30 was65.1% ± 10.0%. V50 was 0%. Separate cone beam computed tomography (CBCT) images (n = 663) were reviewed. The avg displacement was as follows: superior 0.4 + 2.99 mm, left 0.23 ± 4.97 mm, and anterior 0.16 ± 5.18 mm. The avg magnitude of displacement was superior/inferior 2.22 ± 2.04 mm, laterally 3.41 ± 3.62 mm, and anterior/posterior 3.86 ± 3.45 mm. The avg vector magnitude was 6.60 ± 4.14 mm. For acute gastrointestinal (GI) toxicities, 50% experienced grade 1 toxicities and 18% grade 2 GI toxicities. For acute genitourinary (GU) toxicities, 21% had grade 1 and 18% had grade 2 toxicities. For late GU toxicities, 7% had grade 1 and 4% had grade 2 toxicities. RB for gynecological patients receiving IMRT in the postoperative setting can limit V40 rectal dose and vaginal displacement. Although V30 constraints were not met, patients had limited acute and late toxicities. Further studies are needed to validate these findings.

A comparison of treatment plan quality between Tri-Co-60 intensity modulated radiation therapy and volumetric modulated arc therapy for cervical cancer

PURPOSE

To investigate the plan quality of tri-Co-60 intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for cervical cancer.

METHODS

A total of 20 patients who received postoperative radiotherapy for cervical cancer were selected. For each patient, a tri-Co-60 IMRT plan for which the target volume was the planning target volume (PTV) generated by adding 1mm isotropic margins from the clinical target volume (CTV) and a VMAT plan for which the target volume was the PTV generated by adding 7mm and 10mm margins from the CTV were generated. The tri-Co-60 IMRT plans were generated with the ViewRay™ system while the VMAT plans were generated with 15-MV photon beams from a linear accelerator (prescription dose=50.4Gy in 28 fractions).

RESULTS

The average volumes of the PTVs and CTVs were 704.9cc±87.8cc and 271.6cc±51.6cc, respectively. No noticeable differences in the dose-volumetric parameters for the target volumes were observed between the tri-Co-60 IMRT and VMAT plans. The values of V_40Gy for the small bowel and rectal wall, V_45Gy of the bladder, and V_35Gy of the femoral heads for the VMAT plans were 14.6%±7.8%, 54.4%±4.2%, 30.0%±4.7%, and 8.9%±3.3%, respectively. Those of the tri-Co-60 IMRT plans were 2.8%±2.1%, 23.0%±8.9%, 17.1%±6.1%, and 0.3%±0.4%, respectively.

CONCLUSIONS

Owing to the target margin reduction capability, the tri-Co-60 IMRT plans were more favorable than the VMAT plans for cervical cancer.

Predictive factors of uterine movement during definitive radiotherapy for cervical cancer

To determine the predictive factors affecting uterine movement during radiotherapy (RT), we quantified interfraction uterine movement using computed tomography (CT) and cone-beam CT (CBCT). A total of 38 patients who underwent definitive RT for cervical cancer were retrospectively analyzed. We compared pre-RT planning CT (n = 38) and intratreatment CBCT (n = 315), measuring cervical and corporal movement in each direction. Correlations between uterine movement and volume changes of the bladder and rectum on all CBCT scans were analyzed using Spearman rank correlation analysis. Relationships between the mean uterine movement and patient factors were analyzed using the Mann-Whitney test. The mean corpus movement was: superior margin (cranio-caudal direction), 7.6 ± 5.9 mm; anterior margin (anteroposterior direction), 8.3 ± 6.3 mm; left margin (lateral direction), 3.3 ± 2.9 mm; and right margin (lateral direction), 3.0 ± 2.3 mm. Generally, the mean values for cervical movement were smaller than those for the corpus. There was a significant, weak correlation between changes in bladder volume and the movement of the superior margin of the corpus (ρ = 0.364, P < 0.001). There was a significant difference in movement of the superior margin of the corpus between the subgroups with and without a history of previous pelvic surgery (P = 0.007). In conclusion, change in bladder volume and a history of previous surgery were significantly related to intrafractional corpus movement; however, our observations suggest that the accurate prediction of uterine movement remains challenging.

Proposed definition of the vaginal cuff and paracolpium clinical target volume in postoperative uterine cervical cancer

PURPOSE

The aim of this study was to develop an appropriate definition for vaginal cuff and paracolpium clinical target volume (CTV) for postoperative intensity modulated radiation therapy in patients with uterine cervical cancer.

METHODS AND MATERIALS

A working subgroup was organized within the Radiation Therapy Study Group of the Japan Clinical Oncology Group to develop a definition for the postoperative vaginal cuff and paracolpium CTV in December 2013. The group consisted of 5 radiation oncologists who specialized in gynecologic oncology and a gynecologic oncologist. A comprehensive literature review that included anatomy, surgery, and imaging fields was performed and was followed by multiple discreet face-to-face discussions and e-mail messages before a final consensus was reached.

RESULTS

Definitions for the landmark structures in all directions that demarcate the vaginal cuff and paracolpium CTV were decided by consensus agreement of the working group. A table was created that showed boundary structures of the vaginal cuff and paracolpium CTV in each direction.

CONCLUSIONS

A definition of the postoperative cervical cancer vaginal cuff and paracolpium CTV was developed. It is expected that this definition guideline will serve as a template for future radiation therapy clinical trial protocols, especially protocols involving intensity modulated radiation therapy.

Should we customize PTV expansions for BMI? Daily cone beam computerized tomography to assess organ motion in postoperative endometrial and cervical cancer patients

AIM

A single-institution review assessing patient characteristics contributing to daily organ motion in postoperative endometrial and cervical cancer patients treated with intensity-modulated radiotherapy (IMRT).

BACKGROUND

The Radiation Therapy Oncology Group has established consensus guidelines for postoperative pelvic IMRT, recommending a 7 mm margin on all three axes of the target volume.

MATERIALS AND METHODS

Daily shifts on 457 radiation setups for 18 patients were recorded in the x axis (lateral), y axis (superior-inferior) and z axis (anterior-posterior); daily positions of the planning tumor volume were referenced with the initial planning scan to quantify variations.

RESULTS

Of the 457 sessions, 85 (18.6%) had plan shifts of at least 7 mm in one of the three dimensions. For obese patients (body mass index [BMI] ≥ 30), 75/306 (24.5%) sessions had plan shifts ≥7 mm. Odds of having a shift ≥7 mm in any direction was greater for obese patients under both univariate (OR 4.227, 95% CI 1.235-14.466, p = 0.021) and multivariate (OR 5.000, 95% CI 1.341-18.646, p = 0.016) analyses (MVA). Under MVA, having a BMI ≥ 30 was associated with increased odds of shifts in the anterior-posterior (1.173 mm, 95% CI 0.281-2.065, p = 0.001) and lateral (2.074 mm, 95% CI 1.284-2.864, p < 0.000) directions but not in the superior-inferior axis (0.298 mm, 95% CI -0.880 to 1.475, p = 0.619) exceeding 7 mm.

CONCLUSIONS

Based on these findings, the standard planned tumor volume expansion of 7 mm is less likely to account for daily treatment changes in obese patients.

An assessment of interfractional bladder, rectum and vagina motion in postoperative cervical cancer based on daily cone-beam computed tomography

Interfractional variations of the bladder, rectum and vagina may affect the accuracy of postoperative intensity-modulated radiotherapy in patients with cervical cancer. This study aimed to assess the interfractional variations with daily kV cone-beam computed tomography (CBCT). All the patients were instructed to control the filling status of the bladder and rectum. CBCT images were obtained daily after set-up and the bladder, rectum and vagina were contoured on each CBCT scan. All the contours were transferred to the planning CT following image fusion. Interfractional variations in pelvic organs were assessed with CBCT based on two reference lines, which were identified as A (the midsaggital line across the superior border of pubic symphysis) and B (a parallel line 1.5 cm above line A). The mean volume (range) of the bladder and rectum was 156.5 (1.7-626.5) and 48.2 (11.3-139.7) ml, respectively. The uniform planning target volume (PTV) margin of 10 mm failed to encompass the vagina in 17.3 and 18.1% of the fractions on lines A and B, respectively. The motion of the vagina (standard deviation) was 0.3 (0.3) and 0.1 (0.5) cm on lines A and B, respectively. The anteroposterior dimension and position of the vagina were significantly affected by the filling status of the bladder (P<0.05), but not by that of the rectum. Although instructions were given, the interfractional variations of the vagina and other pelvic organs were significant, which may exceed the uniform PTV margin; therefore, more effective methods to decrease these variations should be investigated.

Internal target volume for post-hysterectomy vaginal recurrences of cervical cancers during image-guided radiotherapy

OBJECTIVE

The outcome of post-surgical recurrences of cervical cancer may be improved through radiation dose escalation, which hinges on accurate identification and treatment of the target. The present study quantifies target motion during course of image-guided radiotherapy (IGRT) for vault cancers.

METHODS

All patients underwent planning CT simulation after bladder-filling protocol. A daily pre-treatment megavoltage CT was performed. All translations and rotations were recorded. Post-registration displacement of gross tumour volume (GTV) and centre of mass (COM) of GTV was independently recorded by two observers for fractions one to seven. Day 1 image sets served as reference images against which the displacements of COM were measured. We calculated the displacements of common volume (CV) and encompassing volume (EV) of GTV for both the observers.

RESULTS

A total of 90 image data sets of 15 patients were available for evaluation. Individual patient GTV and average GTV by both the observers were comparable. The average shifts for EV were 2.4 mm [standard deviation (SD) ±1.2] in the mediolateral, 4.2 mm (SD ±2.8) in the anteroposterior and 4.0 mm (SD ±2.1) in superoinferior directions. Similarly, the average shifts for CV were 1.9 mm (SD ±0.6) in the mediolateral, 3.7 mm (SD ±2.7) in the anteroposterior and 4.4 mm (SD ±2.7) in superoinferior directions. Using Stroom's/van Herk's formula, the minimum recommended margins would be 4.5/5.2, 8.2/9.4 and 7.3/8.3 mm, respectively, for lateral, anteroposterior and superoinferior directions.

CONCLUSION

Differential directional internal margin is recommended in patients undergoing IGRT for post-surgical recurrence of cervical cancers.

ADVANCES IN KNOWLEDGE

Internal organ motion of vault cancers can be accounted for by a directional margin to the gross tumour.

Positioning accuracy during VMAT of gynecologic malignancies and the resulting dosimetric impact by a 6-degree-of-freedom couch in combination with daily kilovoltage cone beam computed tomography

Background

To improve the delivery of radiotherapy in gynecologic malignancies and to minimize the irradiation of unaffected tissues by using daily kilovoltage cone beam computed tomography (kV-CBCT) to reduce setup errors.

Methods

Thirteen patients with gynecologic cancers were treated with postoperative volumetric-modulated arc therapy (VMAT). All patients had a planning CT scan and daily CBCT during treatment. Automatic bone anatomy matching was used to determine initial inter-fraction positioning error. Positional correction on a six-degrees-of-freedom (6DoF) couch was followed by a second scan to calculate the residual inter-fraction error, and a post-treatment scan assessed intra-fraction motion. The margins of the planning target volume (M_PTV) were calculated from these setup variations and the effect of margin size on normal tissue sparing was evaluated.

Results

In total, 573 CBCT scans were acquired. Mean absolute pre-/post-correction errors were obtained in all six planes. With 6DoF couch correction, the M_PTV accounting for intra-fraction errors was reduced by 3.8–5.6 mm. This permitted a reduction in the maximum dose to the small intestine, bladder and femoral head (P = 0.001, 0.035 and 0.032, respectively), the average dose to the rectum, small intestine, bladder and pelvic marrow (P = 0.003, 0.000, 0.001 and 0.000, respectively) and markedly reduced irradiated normal tissue volumes.

Conclusions

A 6DoF couch in combination with daily kV-CBCT can considerably improve positioning accuracy during VMAT treatment in gynecologic malignancies, reducing the M_PTV. The reduced margin size permits improved normal tissue sparing and a smaller total irradiated volume.

Whole pelvic intensity-modulated radiotherapy for gynecological malignancies: A review of the literature

Radiation therapy has long played a major role in the treatment of gynecological malignancies. There is increasing interest in the utility of intensity-modulated radiotherapy (IMRT) and its application to treat gynecological malignancies. Herein, we review the state-of-the-art use of IMRT for gynecological malignancies and report how it is being used alone as well as in combination with chemotherapy in both the adjuvant and definitive settings. Based on dosimetric and clinical evidence, IMRT can reduce gastrointestinal, genitourinary, and hematological toxicities compared with 3D-conformal radiotherapy for gynecologic malignancies. We discuss how these attributes of IMRT may lead to improvements in disease outcomes by allowing for dose escalation of radiation therapy, intensification of chemotherapy, and limiting toxicity-related treatment breaks. Currently accruing trials investigating pelvic IMRT for cervical and endometrial cancers are discussed.

[What technique for what tumor? Ethical and methodological issues: cervical cancer]

Cancers of the uterus are on the list of cancer sites for which the interest of the use of conformal radiotherapy with intensity modulation is being evaluated by the French Health Authority. In 2014, many consider that many challenges still lie ahead for the integration of this technique in routine management of cervical cancer on intact uterus. These challenges, are they really a barrier to diffusion of this technique for a tumor location where the radiation keeps an important role? The purpose of this review is to discuss, in terms of the risk-benefit balance, the prescription of intensity-modulated radiotherapy compared to non-modulated three-dimensional conformal radiotherapy.

[Evidence based medicine and high performance irradiation techniques: endometrial cancer]

Radiation oncology is a field in which many technologic improvements have been made over the past decades. External beam radiotherapy has evolved from treatment fields planned on X-rays to 3-dimensional planning with fusion with MRI's and PET images. Recently, intensity-modulated radiotherapy has been tested for many cancer localizations, and its role in the treatment of gynecologic cancers is still under evaluation. Potential benefits are well known: decrease of treatment toxicity, improvement of efficacy through better dose delivery. But the implementation of this technique requires a careful target and organs at risk delineation. The goal of this review is to evaluate the use of intensity-modulated radiotherapy in endometrial cancers with respect of dosimetric and clinical studies to date. In addition, challenges and perspectives of intensity-modulated radiotherapy integration are discussed.

Vaginal displacement during course of adjuvant radiation for cervical cancer: results from a prospective IG-IMRT study

OBJECTIVE

To compare internal target volume (ITV) generated using population-based displacements (ITV_study) with empty and full bladder scan fusion (ITV_EBFB) for organ-at-risk (OAR) doses during adjuvant intensity-modulated radiation therapy (IMRT) for cervical cancer.

METHODS

From January 2011 to October 2012, patients undergoing IMRT were included. CT simulation was carried out after inserting vault markers. Planning target volume (PTV)_EBFB received 50 Gy per 25 fractions. Pre-treatment megavoltage CT (MVCT) was performed. MVCTs were registered using bony landmarks with Day 1 MVCT. Displacement of the centre of mass of markers was measured along each axis. Directional ITV was calculated using mean ± 2 standard deviations (SDs) (ITV_study). Replanning was performed using PTV study, and OAR doses were compared with PTV_EBFB using Wilcoxon test.

RESULTS

A total of 348/386 data sets were evaluable for 16 patients. The median vaginal displacement was 1.2 mm (SD, 1.3 mm), 4.0 mm (SD, 3.5 mm) and 2.8 mm (SD, 3.3 mm) in the mediolateral, superoinferior and anteroposterior directions, respectively. The ITV margins were 4.1, 10.3 and 10.6 mm. ITV_study and ITV_EBFB were 115.2 cm(3) (87.7-152.2 cm(3)) and 151 cm(3) (95.7-277.1 cm(3)) (p < 0.0001), respectively. PTV_study and PTV_EBFB were 814 and 881 cm(3) (p < 0.0001), respectively. Median doses to the bladder were lower with the PTV_study (46.2 Gy vs 43.2 Gy; p = 0.0001), and a similar trend was observed in the volume of the small bowel receiving 40 Gy (68.2 vs 60.1 cm(3); p = 0.09).

CONCLUSION

Population-based PTV margins can lead to reduction in OAR doses.

ADVANCES IN KNOWLEDGE

Population-based ITV may reduce OAR doses while executing adjuvant IMRT for cervical cancer.

Does obesity hinder radiotherapy in endometrial cancer patients? The implementation of new techniques in adjuvant radiotherapy - focus on obese patients

The increasing incidence of obesity in Poland and its relation to endometrioid endometrial cancer (EEC) is resulting in the increasing necessity of treating obese women. Treatment of an overweight patient with EEC may impede not only the surgical procedures but also radiotherapy, especially external beam radiotherapy (EBRT). The problems arise both during treatment planning and when delivering each fraction due to the difficulty of positioning such a patient – it implies the danger of underdosing targets and overdosing organs at risk. Willingness to use dynamic techniques in radiation oncology has increased for patients with EEC, even those who are obese. During EBRT careful daily verification is necessary for both safety and treatment accuracy. The most accurate method of verification is cone beam computed tomography (CBCT) with soft tissue assessment, although it is time consuming and often requires a radiation oncologist. In order to improve the quality of such treatment, the authors present the practical aspects of planning and treatment itself by means of dynamic techniques in EBRT. The authors indicate the advantages and disadvantages of different types of on-board imaging (OBI) verification images. Considering the scanty amount of literature in this field, it is necessary to conduct further research in order to highlight proper planning and treatment of obese endometrial cancer patients. The review of the literature shows that all centres that wish to use EBRT for gynaecological tumours should develop their own protocols on qualification, planning the treatment and methods of verifying the patients’ positioning.

Role of image guided radiation therapy in obese patients with gynecologic malignancies

PURPOSE

We investigated the effect of body mass index on setup errors by analyzing daily shifts required in treating patients undergoing image guided radiation therapy (IGRT) for gynecologic malignancies.

METHODS AND MATERIALS

Forty successive patients treated with daily kV-based IGRT for gynecologic malignancies between April 2009 and June 2012 were identified. Directional setup corrections were analyzed according to patient body mass index. Random and systematic setup errors were calculated. Image acquisition dose was estimated by performing ionization chamber measurements in a phantom.

RESULTS

Obese patients had larger random setup errors, particularly in the right-left (R-L) direction, with a setup error of 7.6 mm, versus 3.9 mm for nonobese patients. The range of individual patient random errors in the R-L direction was 1.5 to 7.6 mm among nonobese patients versus 2.0 to 17.0 mm among obese patients (P = .03, F-test). For obese patients, daily IGRT prevented treating outside the planning target volume in 33% of fractions, versus 16% in the nonobese group (P = .001). The mean total image acquisition dose from daily kV-IGRT was approximately 3 cGy, versus 150 cGy if daily megavoltage portal imaging were used to correct for erratic setup errors.

CONCLUSIONS

Daily kV-based IGRT in obese patients allows for correction of erratic setup error and minimizes excess dose from portal imaging.

Clinical outcomes of image guided radiation therapy (IGRT) with gold fiducial vaginal cuff markers for high-risk endometrial cancer

OBJECTIVE

To report two year clinical outcomes of image guided radiation therapy (IGRT) to the vaginal cuff and pelvic lymph nodes in a series of high-risk endometrial cancer patients.

METHODS

Twenty-six consecutive high-risk endometrial cancer patients requiring adjuvant radiation to the vaginal cuff and regional lymph nodes were treated with vaginal cuff fiducial-based IGRT. Seventeen (65%) received sequential chemotherapy, most commonly with a sandwich technique. Brachytherapy followed external radiation in 11 patients to a median dose of 18 Gy in 3 fractions. The median external beam dose delivered was 47.5 Gy in 25 fractions.

RESULTS

All 656 fractions were successfully imaged and treated. The median overall translational shift required for correction was 9.1 mm (standard deviation, 5.2 mm) relative to clinical set-up with skin tattoos. Shifts of 1 cm, 1.5 cm, and 2 cm or greater were performed in 43%, 14%, and 4% of patients, respectively. Acute grade 2 gastrointestinal (GI) toxicity occurred in eight patients (30%) and grade 3 toxicity occurred in one. At two years, there have been no local or regional failures and actuarial overall survival is 95%.

CONCLUSION

Daily image guidance for high-risk endometrial cancer results in a low incidence of acute GI/genitourinary (GU) toxicity with uncompromised tumor control at two years. Vaginal cuff translations can be substantial and may possibly result in underdosing if not properly considered.

Intensity modulated radiotherapy in gynecologic cancers: hope, hype or hyperbole?

Significant advances have occurred within the field of radiation oncology within the past few decades. Treatment with external beam radiotherapy has progressed from treatment fields planned from bony anatomy seen on planar X-rays, to 3-dimensional planning utilizing fused MRI's and PET images. Recently, intensity modulated radiotherapy (IMRT) has been integrated into many areas within radiation oncology, and its role in the treatment of gynecologic cancers is evolving. Potentials exist for improvements in both treatment toxicity, as well as improved efficacy through advances in treatment delivery. Unique challenges are also raised, however. With increased accuracy of treatment delivery comes the need for greater accuracy in target delineation and incorporation of motion to prevent marginal misses. The goal of this review is to evaluate the use of IMRT in cervical and endometrial cancers, including the results of dosimetric and clinical studies to date. In addition, potential disadvantages and challenges of IMRT integration are discussed.

Postoperative pelvic intensity-modulated radiotherapy in high risk endometrial cancer

OBJECTIVE

According to national surveys, the use of intensity-modulated radiation therapy (IMRT) in gynecologic cancers is on the rise, yet there is still some reluctance to adopt adjuvant IMRT as standard practice. The purpose of this study is to report a single-institution experience using postoperative pelvic IMRT with or without chemotherapy in high-risk endometrial cancer.

METHODS

From 11/2004 to 12/2009, 46 patients underwent hysterectomy/bilateral salpingo-oophorectomy for stage I-III (22% stage I/II and 78% stage III) endometrial cancer. Median IMRT dose was 50.4Gy. Adjuvant chemotherapy was given to 30 (65%) patients.

RESULTS

With a median follow-up of 52months, 4 patients recurred: 1 vaginal plus lung metastasis, 2 isolated para-aortic recurrences, and 1 lungs and liver metastasis. Five-year relapse rate was 9% (95% CI, 0-13.6%). Five-year disease-free survival (DFS) was 88% (95% CI, 77-98%) and overall survival (OS) was 97% (95% CI, 90-100%). There were 2 patients with non-hematological grade 3 toxicity: 1 (2%) acute and 1 (2%) chronic gastrointestinal toxicity. In patients treated with IMRT and chemotherapy (n=30), 5 had grade 3 leukopenia, 8 grade 2 anemia, and 2 grade 2 thrombocytopenia.

CONCLUSIONS

Oncologic outcomes with postoperative IMRT were very good, with DFS and OS rates of >88% at median follow-up of 52months, despite a preponderance (78%) of stage III disease. Toxicity was minimal even in the setting of an aggressive trimodality (65% of patients) approach. Data from this study and emerging data from RTOG trial 0418 demonstrate the advantages of IMRT in high-risk endometrial cancer.