Robotic radiosurgery as an alternative to brachytherapy for cervical cancer patients

3D-printed Magnetic Resonance (MR)-based gynecological phantom for image-guided brachytherapy training

PURPOSE/OBJECTIVES

There is a clinical need to develop anatomic phantoms for simulation-based learning in gynecological brachytherapy. Here, we provide a step-by-step approach to build a life-sized gynecological training phantom based on magnetic resonance imaging (MRI) of an individual patient. Our hypothesis is that this phantom can generate convincing ultrasound (US) images that are similar to patient scans.

METHODS

Organs-at-risk were manually segmented using patient scans (MRI). The gynecological phantom was constructed using positive molds from 3D printing and polyvinyl chloride (PVC) plastisol. Tissue texture/acoustic properties were simulated using different plastic softener/hardener ratios and microbead densities. Nine readers (residents) were asked to evaluate 10 cases (1 ultrasound image per case) and categorize each as a "patient" or "phantom" image. To evaluate whether the phantom and patient images were equivalent, we used a multireader, multicase equivalence study design with two composite null hypotheses with proportion (pr) at H01: pr ≤ 0.35 and H02: pr ≥ 0.65. Readers were also asked to review US videos and identify the insertion of an interstitial needle into the pelvic phantom. Computed Tomography (CT) and magnetic resonance (MR) images of the phantom were acquired for a feasibility study.

RESULTS

Readers correctly classified "patient" and "phantom" scans at pr = 53.3% ± 6.2% (p values 0.013 for H01 and 0.054 for H02, df = 5.96). Readers reviewed US videos and identified the interstitial needle 100% of the time in transabdominal view, and 78% in transrectal view. The phantom was CT and MR safe.

CONCLUSIONS

We have outlined a manufacturing process to create a life-sized, gynecological phantom that is compatible with multi-modality imaging and can be used to simulate clinical scenarios in image-guided brachytherapy procedures.

Stereotactic Body Radiotherapy Boost with the CyberKnife for Locally Advanced Cervical Cancer: Dosimetric Analysis and Potential Clinical Benefits

(1) Aim: To compare the treatment plans of stereotactic body radiotherapy (SBRT) with CyberKnife (CK) and high-dose-rate (HDR) intracavitary/interstitial brachytherapy (IC/ISBT) and examine the feasibility of CK-SBRT as a viable alternative to BT in patients with locally advanced cervical cancer (LACC). (2) Methods: A BT plan of 28 Gy in four fractions delivered previously to 20 patients with LACC was compared with a CK plan based on the same CT images with structures delineation for BT. The SBRT treatment plan was further divided according to two different approaches, with the high-risk planning target volume (HR-PTV) defined by the high-risk clinical target volume (HR-CTV) without and with a 5 mm margin, which were named CK-CTV plan and CK-PTV plan, respectively. The dose distributions and dosimetric parameters of the target volumes and organs at risk (OARs) were recorded and compared for the three boost plans. Radiobiological metrics were calculated based on the EUD for the hybrid plans. Additionally, the relationship between tumor volume and tolerance doses for the OARs in the BT plan and CK-PTV plan was investigated. (3) Results: Target coverage was better with the CK plan than with the BT plan, as the D95%, D98%, HI and CI of the CK-CTV plan and CK-PTV plan were higher than those of the BT plan; an exception was the D50%. Similarly, the TCP of the target was also significantly in favor of the CK hybrid plans (p < 0.01). For the OARs, the CK-CTV plan was superior to the BT plan as regards the rectum D2cc, bladder D2cc and bladder Dmax. The CK-PTV plan could achieve dosimetric parameters comparable to those of the BT plan for OARs concerning the small residual tumor volume. The NTCP of the rectum for the WPI+CK-CTV plans was significantly lower than that of the WPI+BT plans (p < 0.01). (4) Conclusions: CK-based SBRT can achieve better target coverage, dose sparing for the OARs and radiobiological effects compared with the BT plan for tumors that are not excessively large. CK-based SBRT could be an alternative option to administer a radiation boost for patients with LACC.

Stereotactic body radiotherapy boost in patients with cervical cancer

Our aim was to evaluate the oncological outcomes of stereotactic body radiotherapy (SBRT) boost in patients with cervical cancer. The data of 21 patients who received SBRT boost after definitive radiotherapy (RT) or chemoradiotherapy (CRT) between March 2012 and April 2019 were retrospectively evaluated. External beam radiotherapy (EBRT) was applied to patients with a total dose of 50.4 Gy in 28 fractions. Kaplan-Meier method was used for survival analysis (IBM SPSS 23 software) and p < .05 value was considered significant. After definitive RT or CRT, there was a complete response in 9 (43%) patients, partial response in 11 (52%) patients and stable disease in 1 (5%) patient. The median follow-up period was 28 months (range, 7.5-88 months). Two-years cancer-specific survival rate was 80%. While 2-year LC rate was 75% in patients with residual tumour size <4 cm, it was 50% when there was ≥4 cm residual tumour after definitive CRT (p = .1). The treatment was well-tolerated and no acute or late toxicity was observed. Although brachytherapy (BRT) is an essential part of the treatment in locally advanced cervical cancer, SBRT may be used in patients with small residual disease who are not candidate for BRT. IMPACT STATEMENTCervical cancer is one of the most common cancers in the world, and external beam radiotherapy (EBRT) and brachytherapy (BRT) are the main treatment options. However, in rare cases where BRT is not feasible, it has been questioned whether stereotactic body radiotherapy (SBRT) as an alternative to BRT.What is already known on this subject? Nowadays, BRT still appears to be the gold standard treatment. However, studies with a small number of patients and short follow-up periods in the literature show that SBRT can be a good alternative in cases where BRT cannot be performed.What do the results of this study add? Our study is one of the series with the largest number of patients in the literature and with the longest follow-up period. In this area where there is no prospective study, we think that retrospective data with high patient numbers are enlightening.What are the implications of these findings for clinical practice and/or further research? Our study shows that SBRT is an alternative option in cases with small residual disease where BRT cannot be applied, and it provides a basis for a prospective randomised study.

The value of brachytherapy in the age of advanced external beam radiotherapy: a review of the literature in terms of dosimetry

Brachytherapy (BT) has long been used for successful treatment of various tumour entities, including prostate, breast and gynaecological cancer. However, particularly due to advances in modern external beam techniques such as intensity-modulated radiotherapy (IMRT), volume modulated arc therapy (VMAT) and stereotactic body radiotherapy (SBRT), there are concerns about its future. Based on a comprehensive literature review, this article aims to summarize the role of BT in cancer treatment and highlight its particular dosimetric advantages. The authors conclude that image-guided BT supported by inverse dose planning will successfully compete with high-tech EBRT in the future and continue to serve as a valuable modality for cancer treatment.

Brachytherapy or external beam radiotherapy as a boost in locally advanced cervical cancer: a Gynaecology Study Group in the Italian Association of Radiation and Clinical Oncology (AIRO) review

This review analyzes the experience and trends in external beam radiotherapy for delivering a boost in locally advanced cervical cancer, identifying whether radiation therapy modalities impact clinical outcomes with the ultimate aim of evaluating alternatives to brachytherapy. Three independent Italian radiation oncologists conducted a literature search on different external beam radiotherapy boost modalities in locally advanced cervical cancer. The search yielded 30 studies. Eight dosimetric studies, evaluating target coverage and dose to organs at risk, and nine clinical investigations, reporting clinical outcomes, were analyzed. Dosimetric studies comparing external beam radiotherapy boost with brachytherapy produced divergent results, while clinical studies were limited by their retrospective nature, heterogeneous doses, radiation schedules, volumes and techniques, diverse follow-up times, and small cohorts of patients. Evidence emerged that high-tech external beam radiotherapy seemed no better than image-guided brachytherapy for delivering a boost in locally advanced cervical cancer. Prospective clinical studies comparing high-tech external beam radiotherapy and image-guided brachytherapy should be encouraged.

Long-term results of robotic radiosurgery for non brachytherapy patients with cervical cancer

BACKGROUND

Consolidation brachytherapy is a critical treatment component for cervical cancer patients undergoing primary chemoradiation. Some patients are unsuitable for brachytherapy for a variety of reasons. The use of alternatives (LINAC-based stereotactic radiosurgery or external beam boosts) compromise oncologic results in cervical cancer patients. Thus, we evaluated the value of brachytherapy-like doses prescriptions using robotic radiosurgery (CyberKnife®, CR, Acuuray, Sunnyvale, CA, USA).

METHODS

From 06/2011 to 06/2015, 31 patients (median age 53 years; range 30-77 years) with histologically proven FIGO stages IB-IVB cervical cancer underwent primary chemoradiation. All patients were either not suitable for intracervical brachytherapy for a variety of reasons or refused the brachytherapy. To achieve an adequate dose within the tumor, a CK boost was applied after fiducial implantation. In 29 patients, a dose of either five times 6 Gy or five times 5 Gy was prescribed to the target volume. Two patients received three times 5 Gy. The target dose was prescribed to the 70% isodose. Treatment toxicity was documented once weekly regarding vaginal mucositis, bladder, and bowel irritation according to CTCAE v. 4.03. If possible 3 months after completion of treatment intracervical curettage was performed to exclude residual tumor and the patients were followed up clinically. Sparing of organs at risk (OAR) and outcome in terms of local control (LC), overall survival (OS), and progression-free survival (PFS) were assessed.

RESULTS

Of the 31 patients, 30 have completed CK boost therapy. The median follow-up time was 40 months (range 5-84 months). General treatment tolerability was good. Except for 1 patient, who had diarrhea grade 3, no treatment related side effects above grade 2 were reported. Sparing of OAR was excellent. The 1‑, 3‑, and 5‑year OS rates were 89, 60, and 57% respectively across all stages. Seven patients showed progression (28%), only two of them with local relapse (8%), resulting in an LC rate of 92% after 3 and 5 years. Mean PFS was 41 months (range 2-84 months). Patients with local recurrence had PFS of 5 and 8 months. Five patients developed distant metastases. Fifteen patients (48%) underwent intracervical curettage 3 months after completion of treatment of which 14 (93%) had complete pathologic response.

CONCLUSION

Brachytherapy remains the standard of care for patients diagnosed with cervical cancer and indication for primary chemoradiation. In terms of local control, CyberKnife®-based boost concepts provide excellent local control. It can be an alternative for patients who cannot receive adequate brachytherapy. Distant relapse still remains a challenge in this context.

IMRT and brachytherapy comparison in gynaecological cancer treatment: thinking over dosimetry and radiobiology

Background

The role of radiotherapy and brachytherapy in the management of locally advanced cervical and endometrial cancer is well established. However, in some cases, intracavitary brachytherapy (ICBRT) is not recommended or cannot be carried out. We aimed to investigate whether external-beam irradiation delivered by means of intensity-modulated radiation therapy (IMRT) might replace ICBRT in gynaecological cancer when the standard ICBRT boost delivering cannot be administered for technical or clinical reasons.

Materials and methods

Fifteen already delivered treatments for gynaecological cancer patients were analysed. The treatments were performed through 3-dimensional conformal radiotherapy (3D-CRT) to the whole-pelvis up to the dose of 45–50.4 Gy followed by a boost dose administered with ICBRT in high-dose-rate or pulsed-dose-rate modality. For each patient, IMRT plans were elaborated to mimic the ICBRT. We analysed the ICBRT boost versus IMRT boost in terms of dosimetric and radiobiological aspects.

Results

Mean conformity index value calculated on boost volume was 0.73 for ICBRT and 0.97 for IMRT. Mean conformation number was 0.24 for ICBRT boost and 0.78 for IMRT boost. Mean normal tissue complication probability (NTCP) values for 3D-CRT plus ICBRT and for IMRT (pelvis plus boost) were, respectively, 28% and 5% for rectum; 1.5% and 0.1% for urinary bladder and 8.9% and 6.1% for bowel.

Conclusions

Our findings suggest that IMRT may represent a viable alternative in delivering the boost in patients diagnosed with gynaecological cancer not amenable to ICBRT.

The Potential Value of MRI in External-Beam Radiotherapy for Cervical Cancer

The reference standard treatment for cervical cancer is concurrent chemoradiotherapy followed by magnetic resonance imaging (MRI)-guided brachytherapy. Improvements in brachytherapy have increased local control rates, but late toxicity remains high with rates of 11% grade ≥3. The primary clinical target volume (CTV) for external-beam radiotherapy includes the cervix and uterus, which can show significant inter-fraction motion. This means that generous margins are required to cover the primary CTV, increasing the radiation dose to organs at risk and, therefore, toxicity. A number of image-guided radiotherapy techniques (IGRT) have been developed, but motion can be random and difficult to predict prior to treatment. In light of the development of integrated MRI linear accelerators, this review discusses the potential value of MRI in external-beam radiotherapy. Current solutions for managing pelvic organ motion are reviewed, including the potential for online adaptive radiotherapy. The impacts of the use of MRI in tumour delineation and in the delivery of stereotactic ablative body radiotherapy (SABR) are highlighted. The potential role and challenges of using multi parametric MRI to guide radiotherapy are also discussed.

External beam techniques to boost cervical cancer when brachytherapy is not an option-theories and applications

The management of locally advanced cervical cancer relies on brachytherapy (BT) as an integral part of the radiotherapy delivery armamentarium. Occasionally, intracavitary BT is neither possible nor available. In these circumstances, post-external beam radiotherapy (EBRT) interstitial brachytherapy and/or hysterectomy may represent viable options that must be adequately executed in a timely manner. However, if these options are not applicable due to patient related or facility related reasons, a formal contingency plan should be in place. Innovative EBRT techniques such as intensity modulated and stereotactic radiotherapy may be considered for patients unable to undergo brachytherapy. Relying on provocative arguments and recent data, this review explores the rationale for and limitations of non-brachytherapy substitutes in that setting aiming to establish a formal process for the optimal execution of this alternative plan.

Modern radiation therapy and potential fertility preservation strategies in patients with cervical cancer undergoing chemoradiation

Young patients with cervical cancer who undergo chemoradiation might be interested in fertility preservation, not only dependent upon the use of a gestational carrier as maybe achieved by the use of ovarian transposition and cryo-conservation of oocytes or ovarian tissue, but may prefer to carry pregnancy to term after cancer treatment. The latter approach is a non-established concept needing both modern radiation therapy approaches as well as modifications -if at all possible- in current recommendations for target volume delineation to spare dose to the unaffected uterus. Future strategies to serve selected patients in this respect should only be conducted in prospective clinical evaluations and are critically discussed in this article.