Comparative analysis of rectal dose parameters in image-guided high-dose-rate brachytherapy for cervical cancer with and without a rectal retractor

Radical radiotherapy in patients with cervix uteri carcinoma: experience of Ondokuz Mayis University

Background

Radical radiotherapy is the standard treatment for patients with locally advanced cervix uteri carcinoma (FIGO stage IB2–IVA). Worldwide, incidence and mortality rates vary among regions because of differences in lifestyles and treatment standards. Herein, we evaluated the outcomes of radical radiotherapy in patients with locally advanced cervix uteri carcinoma from the middle Black Sea region of Turkey.

Methods

We retrospectively reviewed the records of 64 consecutive patients with locally advanced cervix uteri carcinoma who were treated from January 2013 to 2016 in our radiation oncology department. All patients staging and radiotherapy planning were performed with modern imaging techniques including magnetic resonance imaging and positron-emission-tomography/computed tomography before radical radiotherapy. Thereafter, all of them were treated with external beam radiotherapy and concurrent cis-platinum-based chemotherapy followed by three-dimensional intra-cavitary high-dose-rate brachytherapy.

Results

The median age at diagnosis was 54.5 years. The median follow-up period was 21 months. Acute grade 3 toxicity was detected in 3.1% of patients. Late toxicity was not detected in any patient. The 1- and 3-year progression-free survival rates were 83.6 and 67.5%, respectively. The 1- and 3-year overall survival rates were 95.7 and 76.9%, respectively. The most important prognostic factor was the FIGO stage. Distant metastasis was the most common cause of death in patients with locally advanced cervix uteri carcinoma despite radical radiotherapy.

Conclusions

In patients with locally-advanced cervix uteri carcinoma from the middle Black Sea region of our developing country, acceptable toxicity and survival rates are achieved similar to the recent literature from developed countries with using of modern staging, planning and radical radiotherapy techniques. However, recurrence was mostly in the form of distant metastases and further investigations on systemic therapies are required.

Initial experience using superflab as intravaginal packing during interstitial brachytherapy for advanced gynecologic cancer

Purpose

Interstitial brachytherapy implemented for locally advanced gynecologic cancer can result in toxicity due to the proximity of organs at risk (OAR). We report our experience using superflab bolus as vaginal packing to displace OAR during interstitial brachytherapy.

Material and methods

Twelve patients with stage IB-IVA gynecologic cancer were treated with definitive chemoradiation including interstitial brachytherapy. A Syed template was used for a computed tomography (CT)-based pre-plan with magnetic resonance imaging (MRI) fusion. A 1-2 cm superflab bolus was cut and sterilized. The tandem and obturator were placed, and superflab was then inserted into the vagina. Interstitial needles were then placed through the template and superflab as per the pre-plan under transabdominal ultrasound guidance. Prescription doses ranged from 85-90 Gy EQD₂ including external beam radiation therapy (EBRT). 5-6 Gy per fraction was delivered biologically effective dose (BID) over 2-3 days in 1-2 implants. Toxicities were evaluated post-treatment, 1 month, and 3 months.

Results

The rectum, bladder, and sigmoid had significant average displacement from the prescription isodose line. The average reduction in D_2cc between pre- and post-implant was 5.19 Gy per fraction (p < 0.0001), 7.19 Gy (p < 0.0004), and 1.78 Gy (p < 0.003) for the rectum, bladder, and sigmoid, respectively. The high-risk target volume (HR-TV) received a median D₉₀ of 104% (range, 58-122%) of the prescription dose, and 92% (range, 71-131%) in the pre-/post-implant plans, respectively (p = 0.4).

Conclusions

Our initial experience with superflab as vaginal packing demonstrates technical feasibility and dosimetric improvement for OAR.

High dose-rate tandem and ovoid brachytherapy in cervical cancer: dosimetric predictors of adverse events

Background

Brachytherapy (BT) is a vital component of the curative treatment of locally advanced cervical cancer. The American Brachytherapy Society has published guidelines for high dose rate (HDR) BT with recommended dose limits. However, recent reports suggest lower doses may be needed to avoid toxicity. The purpose of this study is to investigate incidence and predictive factors influencing gastrointestinal (GI) and genitourinary (GU) toxicity following HDR intracavitary brachytherapy for locally advanced cervical cancer.

Methods

We retrospectively evaluated a cohort of patients with locally advanced cervical cancer who received CT-based HDR BT. Cumulative doses were calculated using the linear-quadratic model. Statistical analyses were used to investigate clinical and dosimetric predictors of GI and GU toxicity following HDR brachytherapy according to CTCAE v4.0 grading criteria.

Results

Fifty-six women with FIGO IB1 – IVA cervical cancer were included. The overall rate of any GU adverse event (Grade 1+) was 23.3% (n = 13) and severe adverse events (Grade 3+) was 7.1% (n = 4). Of those, the bladder equivalent dose in 2- Gray (Gy) fractions (EQD₂) D_2cc was ≥80 for three of the four patients. The overall rate of any GI adverse event was 26.8% (n = 15) and the rate of severe adverse events was 14.3% (n = 8). Of those, six of the eight patients had a rectal EQD₂ D_2cc ≥ 65 Gy and seven patients had a sigmoid D2cc ≥ 65 Gy. Amongst clinically meaningful factors for development of adverse events (i.e. diabetes, smoking status, ovoid size, and treatment duration), there were no statistically significant prognostic factors identified.

Conclusions

Severe adverse events are observed even with adherence to current ABS guidelines. In the era of recent multi-institutional study results, our data also supports more stringent dosimetric goals. We suggest cumulative D2cc dose limits of: less than 80 Gy for the bladder and less than 65 Gy for the rectum and sigmoid.

Clinical analysis of speculum-based vaginal packing for high-dose-rate intracavitary tandem and ovoid brachytherapy in cervical cancer

Purpose

Intra-vaginal packing is used to fix the applicator and displace organs at risk (OAR) during high-dose-rate intracavitary tandem and ovoid brachytherapy (HDR-ICB). We retain the speculum from applicator placement as a dual-function bladder and rectum retractor during treatment. Our objective is to review salient techniques for OAR displacement, share our packing technique, and determine the reduction in dose to OAR and inter-fraction variability of dose to OAR, associated with speculum-based vaginal packing (SBVP) in comparison to conventional gauze packing during HDR-ICB.

Material and methods

We reviewed HDR-ICB treatment plans for 45 patients, including 10 who underwent both conventional gauze packing and SBVP. Due to institutional inter-provider practice differences, patients non-selectively received either packing procedure. Packing was performed under conscious sedation, followed by cone beam computed tomography used for dosimetric planning. Maximum absolute and percent-of-prescription dose to the International Commission of Radiation Units bladder and rectal points in addition to D_0.1cc, D_1.0cc, and D_2.0cc volumes of the bladder and rectum were analyzed and compared for each packing method using an independent sample t-test.

Results

Of the 179 fractions included, 73% and 27% used SBVP and gauze packing, respectively. For patients prescribed 6 Gy to point A, SBVP was associated with reduced mean D_0.1cc bladder dose, inter-fraction variability in D_0.1cc bladder dose by 9.3% (p = 0.026) and 9.0%, respectively, and statistically equivalent rectal D_0.1cc, D_1.0cc, and D_2.0cc. Patients prescribed 5.5 Gy or 5 Gy to point A after dose optimization, were less likely to benefit from SBVP. In the intra-patient comparison, 80% of patients had reduction in at least one rectum or bladder parameter.

Conclusions

In patients with conducive anatomy, SBVP is a cost-efficient packing method that is associated with improved bladder sparing and comparable rectal sparing relative to gauze packing during HDR-ICB without general anesthesia.

Prospective comparison of rectal dose reduction during intracavitary brachytherapy for cervical cancer using three rectal retraction techniques

PURPOSE

To compare three rectal retraction methods on dose to organs at risk, focusing on rectal dose, in cervix cancer patients treated with high-dose-rate intracavitary brachytherapy.

METHODS AND MATERIALS

A prospective study was conducted on patients with cervical carcinoma treated with chemoradiotherapy, including external beam radiation and four fractions of high-dose-rate intracavitary brachytherapy prescribed to Point A using a ring and tandem applicator under conscious sedation. Rectal retraction methods included: a rectal retractor blade (RR), vaginal gauze packing (VP), and a tandem Foley balloon (FB). All three methods were used in all patients. The RR was used first, and the following applications were randomly assigned to VP or FB. CT planning was used to calculate D2cc for rectum, sigmoid, small bowel, and bladder. The Wilcoxon signed rank test was used to determine if the median dose differences between methods were statistically significant.

RESULTS

In these 11 patients, median dose (min, max) in cGy to the rectum using RR, FB, and VP was 131 (102, 165), 199 (124, 243), and 218 (149, 299), respectively. The RR demonstrated lower median intrapatient doses to rectum compared with FB and VP (-55 cGy; p = 0.014 and -76 cGy; p = 0.004, respectively). The RR also resulted in lower sigmoid doses. No differences in dose were observed between the VP and FB methods.

CONCLUSION

The rectal retractor significantly reduced the dose to rectum and sigmoid compared with FP and VP. In patients treated under conscious sedation, the RR method provides the best rectal sparing. There were no significant differences in dose observed between the FB and VP techniques.

Bladder-Rectum Spacer Balloon versus Vaginal Gauze Packing in High Dose Rate Brachytherapy in Cervical Cancer: A Randomised Study. Part II

AIMS

To compare the inter-fraction dose variation for bladder and rectum using a bladder-rectum spacer balloon (BRSB) versus vaginal gauze packing (VGP) in patients treated with high dose rate intracavitary brachytherapy for carcinoma cervix.

MATERIALS AND METHODS

After the completion of external radiotherapy, 80 patients were randomised to receive intracavitary brachytherapy using either the BRSB or VGP. The procedure was carried out under general anaesthesia using tandem ovoid applicators. Computed tomography-based planning was carried out and the dose was prescribed to point A. Doses to 0.1, 1 and 2 cm(3) volumes were reported for bladder and rectum for each fraction. The absolute inter-fraction dose variation for each subvolume was compared using the independent sample t-test.

RESULT

The mean bladder and rectal volumes, as well as the inter-fraction volume variation, were comparable for the BRSB and VGP. The BRSB resulted in a significant reduction in absolute dose as well as the inter-fraction variation for dose to 2 cm(3) rectum volumes (BRSB 0.80 Gy, standard deviation 0.71 Gy versus VGP 1.16 Gy, standard deviation 0.83 Gy; P = 0.04). Cumulative bladder D2cm(3) doses of more than 90 Gy3 were observed in six patients in the BRSB arm versus four patients in the VGP arm (P = 0.73). In both the arms, the rectal D2cm(3) doses did not exceed 75 Gy3.

CONCLUSIONS

Use of a BRSB resulted in a significant reduction in inter-fraction variation in D2cm(3) rectal dose. However, no significant difference in the inter-fraction dose variation for the other subvolumes of bladder and rectum could be shown between the BRSB and VGP. The use of a BRSB may enable rectal dose reduction and inter-fraction variation where anaesthesia is not routinely used or where there is limited physician expertise. The modification suggested in the BRSB may facilitate its additional usage.