Dosimetric feasibility of stereotactic body radiation therapy as an alternative to brachytherapy for definitive treatment of medically inoperable early stage endometrial cancer

National Cancer Database analysis of radiation therapy consolidation modality and dose for inoperable endometrial cancer

OBJECTIVE

We utilized the National Cancer Database (NCDB) to evaluate trends and assess outcomes in radiation therapy (RT) boost modality and total dose among medically inoperable endometrial cancer (EC) patients with locoregional disease.

METHODS

Patients with International Federation of Gynecology and Obstetrics (FIGO) stage I - IIIC2 inoperable EC treated with RT ± chemotherapy were analyzed. Practice patterns compared external beam RT (EBRT) versus high-dose-rate brachytherapy (BT) boost and total RT dose (palliative: ≤3000 cGy, definitive low dose [DLD]: 4500 - 6249 cGy, definitive high dose [DHD]: ≥6250 cGy) over time. Kaplan-Meier method evaluated overall survival (OS) and Cox proportional hazard modeling assessed variables associated with OS.

RESULTS

NCDB included 1755 total cases, of which 1209 received a radiotherapy boost. From 2004 to 2019, boost modality rates differed with increasing utilization of BT consolidation and a decreasing rate of palliation. Predictors of a palliative dose were stage III disease, Black race, N2 disease, and poorly or undifferentiated grade. Multivariable analysis found BT boost was associated with lower mortality compared to EBRT (HR: 0.81, CI: 0.68-0.97; p = 0.019). Mortality rates were higher for palliation versus DHD. Additional factors associated with inferior survival were increasing age, worse Charlson-Deyo score, higher T stage, higher N stage, and moderately, poorly, or undifferentiated grade.

CONCLUSIONS

Utilization of BT boost for locoregionally confined, medically inoperable EC has increased since 2004. Brachytherapy consolidation remains an effective RT modality for medically inoperable EC, associated with lower mortality compared to EBRT consolidation.

Magnetic Resonance Imaging-Guided Stereotactic Body Radiation Therapy for Medically Inoperable Endometrial Cancer

Endometrial carcinoma is the most frequently diagnosed gynecological cancer among women aged 50 and older in developed countries. In patients who are not amenable to surgery, radiotherapy results in improved survival with acceptable adverse effect profiles. Definitive stereotactic body radiotherapy (SBRT) as a monotherapy remains an unaddressed concept in the literature. Here, we present the case of an 86-year-old woman who was diagnosed with early-stage endometrial carcinoma and was medically inoperable due to cardiac comorbidities. She was treated with magnetic resonance imaging-guided online adaptive radiotherapy-based SBRT. She tolerated the treatment well, with mild increased vaginal discharge. Complete metabolic and radiological responses were obtained. She continues to be disease free in the first year of treatment with no long-term side effects. Our protocol presents promising results with a safe toxicity profile for inoperable early-stage endometrial cancer. Future studies are warranted in light of the current knowledge.

Radiation therapy in the definitive management of medically inoperable endometrial cancer

The incidence of endometrial cancer continues to increase worldwide with growing life expectancy and rates of obesity. While endometrial cancer is primarily a surgical disease managed with hysterectomy, a small proportion of patients are deemed to be poor surgical candidates due to their co-morbidities. These medically inoperable patients should be considered for curative treatment with definitive radiation therapy, and brachytherapy is an integral component of their care. Referral to a high-volume center early on in the care of potentially inoperable patients is crucial to optimize their management. These patients should be evaluated by a high-risk surgical and anesthesia team to confirm their medical inoperability. For inoperable patients, use of image-guided brachytherapy is encouraged. Brachytherapy applicator selection is determined based on a patient’s anatomy, uterine size, and extent of tumor. Advances in anatomic and functional imaging including multiparametric magnetic resonance imaging (MRI) have improved clinical staging of these patients and have also allowed for the delivery of three-dimensional image-guided brachytherapy with improved accuracy. With recent consensus guidelines to guide local computed tomography and/or MRI volume-based delineation of targets and organs-at-risk, local outcomes have improved and treatments are delivered with less acute and late morbidity. Ongoing trials are looking at novel systemic agents, such as immunotherapy, to induce a systemic anti-tumor immune response and improve outcomes in these patients.

External beam management of stage I and II uterine cancer

This review article highlights the treatment paradigms for early-stage endometrial cancer with a focus on the role of external beam radiation therapy. We aim for this review to serve as an introductory resource for gynecological oncologists, radiation oncologists, medical oncologists, and other practitioners to understand the treatments for this disease. The main treatment of endometrial cancer is surgical resection with total hysterectomy and bilateral salpingo-oophorectomy. The benefit of adjuvant radiation after surgery is primarily to prevent local recurrence. Patients with low risk of recurrence can be observed post-operatively. Vaginal cuff brachytherapy, which has been shown to be equally effective as pelvic radiation with fewer side effects, is typically recommended for high–intermediate risk patients (with characteristics such as lymphovascular space invasion, high grade, or significant myometrial invasion). In the adjuvant setting, pelvic radiation therapy is reserved for patients who have deeply invasive stage I grade 2 or 3 disease, stage II disease, and non-endometrioid histologies. In patients who are not medically operable, definitive treatment consists of brachytherapy±pelvic external beam radiation therapy. We have highlighted the main acute and long-term side effects of pelvic radiation as well as recommendations for symptom management and summarized promising evidence showing improved rates of toxicities with more conformal radiation techniques.

Evaluation of the impact of EMBRACE II protocol in Spanish centers, with a large cohort of patients using a ranking index

PURPOSE

The aim of this paper was to assess development of high-dose-rate (HDR) cervix brachytherapy (BT) implants in three Spanish institutions before and after introduction of EMBRACE II protocol.

MATERIAL AND METHODS

392 patients from three different institutions, treated between 2009 and 2019 were analyzed. D90 of high-risk clinical target volume (HR-CTV) and D2cc of organs at risk (OARs) of all patients were collected. Statistical distribution was analyzed for two different periods of time: before and after EMBRACE II publication. Index I was applied based on collected dosimetric quantities (D90 and D2cc) to enhance equilibrium between HR-CTV coverage and doses to OARs. Variation in dosimetry and index depending on CTV and technique used (IC vs. IC/IT) were also evaluated.

RESULTS

Adaptation of institutions to EMBRACE II protocol resulted in a statistically significant increase of D90 HR-CTV (Institution 1; p < 0.00001) or decrease of D2cc OARs (Institution 2; p < 0.04). Increase in the use of interstitial component showed higher coverage of HR-CTV for Institution 3 (p = 0.03), and lower doses to OARs for the same coverage of HR-CTV at Institution 2 (p-OARs < 0.03). Even though index I was only significantly different between periods for Institution 1 (p < 0.0000001), it was able to show a reduction of dose variability related to higher expertise and higher interstitial component.

CONCLUSIONS

Depending on local protocol before EMBRACE II, the adaptation through increasing interstitial component and physician and physicist training, resulted in a significant increase of HR-CTV doses or reduction of OARs doses. Index I was able to describe an evolution of equilibrium between CTV coverage and OARs' sparing.

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.

Endometrial Cancer: When Upfront Surgery Is Not an Option

Background and Summary: The management of endometrial cancer, in an ever-older population with considerable comorbidity, remains a challenge for gynecological and radiation oncologists. Key Message: The present paper reviews literature data on treatment options for endometrial cancer patients unfit for surgery.

Inter-observer and intra-observer variability in reporting vaginal dose points for cervical cancer in high-dose-rate brachytherapy

PURPOSE

The ICRU 89 recommends reporting a set of vaginal dose points for cervical cancer treatments in order to quantify the goodness of implant. This vaginal dose reporting method for combined external beam radiotherapy and brachytherapy has been adopted by the EMBRACE II study protocol. Large variations in dose between patients and centers have been reported. The aim of this study was to determine possible discrepancies with consensus observers from the same institution. Therefore, the inter- and intra-observer variability were analyzed.

MATERIAL AND METHODS

For five patients, five experienced observers reported dose at the proposed vaginal points twice. The effect of inter- and intra-observer variations on total dose was analyzed by estimating biologically equivalent dose EQD2 (α/β = 3 Gy). Coefficient of variation (CV) was used to provide a measure of data dispersion as a proportion to the mean.

RESULTS

The maximum inter-observer deviation among all patients and all points ranged from 0.5 Gy to 24.1 Gy in EQD2. The higher inter-observer discrepancies were found at points at 3 o'clock and at 6 o'clock, with respect to ovoids. In case of the maximum intra-observer deviation, it ranged from 0.5 Gy to 14.2 Gy, with higher deviation points at 12 o'clock and 9 o'clock, with respect to ovoids.

CONCLUSIONS

There is a need to ensure consistency in vaginal points reporting. The impact of the dosimetric inter- and intra-observer variability should also be considered when dealing with dose tolerances and limits due to the potential dose gradient.

Review of strategies for MRI based reconstruction of endocavitary and interstitial applicators in brachytherapy of cervical cancer

Brachytherapy plays an essential role in the curative intent management of locally advanced cervical cancer. The introduction of the magnetic resonance (MR) as a preferred image modality and the development of new type of applicators with interstitial components have further improved its benefits. The aim of this work is to review the current status of one important aspect in the cervix cancer brachytherapy procedure, namely catheter reconstruction. MR compatible intracavitary and interstitial applicators are described. Considerations about the use of MR imaging (MRI) regarding appropriate strategies for applicator reconstruction, technical requirements, MR sequences, patient preparation and applicator commissioning are included. It is recommendable to perform the reconstruction process in the same image study employed by the physician for contouring, that is, T2 weighted (T2W) sequences. Nevertheless, a clear identification of the source path inside the catheters and the applicators is a challenge when using exclusively T2W sequences. For the intracavitary component of the implant, sometimes the catheters may be filled with some substance that produces a high intensity signal on MRI. However, this strategy is not feasible for plastic tubes or titanium needles, which, moreover, induce magnetic susceptibility artifacts. In these situations, the use of applicator libraries available in the treatment planning system (TPS) is useful, since they not only include accurate geometrical models of the intracavitary applicators, but also recent developments have made possible the implementation of the interstitial component. Another strategy to improve the reconstruction process is based on the incorporation of MR markers, such as small pellets, to be used as anchor points. Many institutions employ computed tomography (CT) as a supporting image modality. The registration of CT and MR image sets should be carefully performed, and its uncertainty previously assessed. Besides, an important research work is being carried out regarding the use of ultrasound and electromagnetic tracking technologies.

Definitive Radiation Therapy for Stage I-II Endometrial Cancer: An Observational Study of Nonoperative Management

OBJECTIVE

There is limited evidence to inform the management of patients with endometrial cancer who are not candidates for hysterectomy, and treatment alternatives have not been compared directly in randomized trials. We analyzed the prognostic factors and outcomes for patients with stage I or II endometrial adenocarcinoma in the National Cancer Institute's Surveillance, Epidemiology, and End Results public database.

METHODS

We identified a cohort of patients with stage I-II endometrial adenocarcinoma who were managed without hysterectomy and who were diagnosed during 1989 to 2010. Patients with prior primary tumors were excluded. Statistical analyses were performed to test associations between patient characteristics, radiotherapy modality, and overall and endometrial cancer-specific survival. Multivariable analyses were performed to evaluate the impact of radiation therapy (RT) type on survival outcomes after adjusting for other factors.

RESULTS

Among the 997 women included in the analyses, 605 received no RT (60.7%), 207 (20.8%) received external-beam radiation therapy (EBRT) alone, and 185 (18.6%) received brachytherapy, either alone or in combination with EBRT. After adjusting for other tumor and demographic factors, RT type was not associated with overall or endometrial cancer-specific survival. Significant predictors of survival included: tumor stage and grade, age at diagnosis, and marital status.

CONCLUSIONS

For patients in this population-based cohort with early-stage endometrial cancer managed without hysterectomy, the delivery of brachytherapy was not associated with improved survival, compared with EBRT alone. It seems worthwhile to pursue future clinical trials to evaluate definitive EBRT-alone strategies, omitting brachytherapy, for selected patients with medically inoperable endometrial cancer.