Interstitial parametrial implants in carcinoma of the cervix stage II-B

Magnetic resonance image-based 3D volume interstitial brachytherapy using polyether ether ketone catheters in advanced cervical cancer - a feasibility study

Purpose

A feasibility study of 3D volume-based interstitial brachytherapy using thermoplastic polyether ether ketone (PEEK) catheters in advanced cervical cancer MR-based brachytherapy, when MR-compatible applicators are not available.

Material and methods

Five cervical cancer patients received EBRT dose of 50 Gy in 25 fractions to whole pelvis using 3D conformal radiotherapy after standard pre-treatment evaluation. In our institute, interstitial brachytherapy (ISBT) is planned in BrachyVision TPS and routinely performed using stainless steel needles with Syed-Neblett template. Standard MR-compatible ISBT applicators were not available; therefore, the implant was carried out using PEEK catheters and Syed-Neblett template. The T1 and T2 MR and CT images of patients were acquired for treatment planning. Gross tumor volume (GTV), high-risk clinical target volume (HR-CTV), intermediate-risk clinical target volume (IR-CTV), and organs at risk (OARs) were delineated with the use of MR T2 weighted images, following GEC-ESTRO guidelines. Volumetric optimization was used for planning, and the treatment plan was executed with high-dose-rate (HDR) ¹⁹²Ir Gammamed Plus device.

Results

The dose prescribed to HR-CTV was 30 Gy low-dose-rate (LDR) equivalent (5 Gy × 4 fractions). Doses to target volume and OARs were analyzed using dose volume histogram (DVH). Dose values were biologically normalized to equivalent doses of 2 Gy fractions (EQD₂). The average tumor volume was 67 cc and the average D₉₀ of HR-CTV was 29 Gy (5.7 Gy/fraction) EQD₂. D₁₀₀ of HR-CTV volume was 18 Gy (3.8 Gy/fraction) EQD₂. The total doses of 2 cc of rectum and bladder were 70 Gy and 76 Gy EQD₂ (3.71 Gy and 4.04 Gy dose/fraction), respectively.

Conclusions

When the facilities for MR-compatible applicators are not available, MR-based ISBT is feasible with PEEK catheters using available resources for advanced cervical cancer. Doses to HR-CTV and IR-CTV were achieved, restricting doses to OARs as per GEC-ESTRO guidelines.

Technical Aspects of the Integration of Three-Dimensional Treatment Planning Dose Parameters (GEC-ESTRO Working Group) into Pre-implant Planning for LDR Gynecological Interstitial Brachytherapy

This study investigates the technical feasibility of pre-implant image-based treatment planning for LDR GYN interstitial brachytherapy(IB) based on the GEC-ESTRO guidelines. Initially, a virtual plan is generated based on the prescription dose and GEC-ESTRO defined OAR dose constraints with a pre-implant CT. After the actual implant, a regular diagnostic CT was obtained and fused with our pre-implant scan/initial treatment plan in our planning software. The Flexi-needle position changes, and treatment plan modifications were made if needed. Dose values were normalized to equivalent doses in 2 Gy fractions (LQED 2 Gy) derived from the linear-quadratic model with α/β of 3 for late responding tissues and α/β of 10 for early responding tissues. D90 to the CTV, which was gross tumor (GTV) at the time of brachytherapy with a margin to count for microscopic disease, was 84.7 ± 4.9% of the prescribed dose. The OAR doses were evaluated by D2cc (EBRT+IB). Mean D2cc values (LQED2Gy) for the rectum, bladder, sigmoid, and small bowel were the following: 63.7 ± 8.4 Gy, 61.2 ± 6.9 Gy, 48.0 ± 3.5 Gy, and 49.9 ± 4.2 Gy. This study confirms the feasibility of applying the GEC-ESTRO recommended dose parameters in pre-implant CT-based treatment planning in GYN IB. In the process, this pre-implant technique also demonstrates a good approximation of the target volume dose coverage, and doses to the OARs.

Predictors of severe gastrointestinal toxicity after external beam radiotherapy and interstitial brachytherapy for advanced or recurrent gynecologic malignancies

PURPOSE

The aim of this retrospective review of patients with gynecologic malignancies treated with external beam radiotherapy (EBRT) and interstitial brachytherapy was to determine the rate of Grade > or =2 rectovaginal fistula and Grade > or =4 small bowel obstruction as defined by the National Cancer Institute Common Toxicity Criteria for Adverse Events, version 3.0.

METHODS AND MATERIALS

Thirty-six patients with primary and recurrent gynecologic cancers were treated with EBRT and interstitial brachytherapy. Median doses to tumor, bladder, and rectum were 75 Gy, 61 Gy, and 61 Gy, respectively. A univariate analysis was performed to identify variables that correlated with toxicity.

RESULTS

At median follow-up of 19 months, the 3-year risk of small bowel obstruction was 6%. Those patients with prior abdomino-pelvic surgery who received EBRT with antero-posterior fields had higher rates of obstruction than patients without prior abdomino-pelvic surgery or those who received EBRT with four fields (50% vs. 0%, p < 0.0001). The 3-year risk of rectovaginal fistula was 18% and was significantly higher in patients who received >76 Gy to the rectum compared with those who received < or =76 Gy (100% vs. 7%, p = 0.009).

CONCLUSIONS

Patients treated with EBRT and interstitial brachytherapy after abdomino-pelvic surgery should receive EBRT with four fields and the cumulative rectal dose should be < or =76 Gy.

Inverse planning for interstitial gynecologic template brachytherapy: truly anatomy-based planning

PURPOSE

Commercially available optimization schemes generally result in an undesirable dose distribution, because of the particular shapes of tumors extending laterally from the tandem. Dose distribution is therefore manually obtained by adjusting relative dwell time values until an acceptable solution is found. The objective of this work is to present the clinical application of an inverse planning dose optimization tool for the automatic determination of source dwell time values in the treatment of interstitial gynecologic templates.

METHODS AND MATERIALS

In cases where the tumor extends beyond the range of the tandem-ovoid applicator, catheters as well as the tandem are inserted into the paravaginal and parametrial region in an attempt to cover the tumor volume. CT scans of these patients are then used for CT-based dose planning. Dose distribution is obtained manually by varying the relative dwell times until adequate dose coverage is achieved. This manual planning is performed by an experienced physician. In parallel, our in-house inverse planning based on simulated annealing is used to automatically determine which of all possible dwell positions will become active and to calculate the dwell time values needed to fulfill dose constraints applied to the tumor volume and to each organ at risk. To compare the results of these planning methods, dose-volume histograms and isodose distributions were generated for the target and each organ at risk.

RESULTS

This procedure has been applied for the dose planning of 12 consecutive interstitial gynecologic templates cases. For all cases, once the anatomy was contoured, the routine of inverse planning based on simulated annealing found the solution to the dose constraints within 1 min of CPU time. In comparison, manual planning took more than 45 min. The inverse planning-generated plans showed improved protection to organs at risk for the same coverage compared to manual planning.

CONCLUSION

This inverse planning tool reduced the planning time significantly and produced improved plans with reduced dose to the organs at risk. Furthermore, the inverse planning approach improves the physician's control over treatment. The focus becomes the physician's prescription to the target and his or her compromise due to dose to normal structures.

Long-term results of low-dose-rate interstitial-intracavitary brachytherapy in the treatment of carcinoma of the cervix

PURPOSE

Brachytherapy plays a major role in the treatment of patients with carcinoma of the cervix. However, routine intracavitary brachytherapy may not be feasible or adequate to treat locally advanced disease. The purpose of this retrospective study (spanning a 20-year period) was to determine the outcome of interstitial low-dose-rate brachytherapy in the treatment of bulky or locally advanced cervical cancer. The long-term survival and safety of this technique were evaluated, along with its impact on local and locoregional control, disease-free survival, and complications.

METHODS AND MATERIALS

A total of 185 previously untreated patients with cervical cancer were treated between 1977 and 1997. According to the International Federation of Gynecology and Obstetrics classification, 21 patients had Stage IB (barrel), 77 Stage II, 77 Stage III, and 10 Stage IV disease. All patients were treated by a combination of external megavoltage irradiation to the pelvis to a dose of 5040 cGy followed by interstitial-intracavitary implants to a dose of 40-50 Gy to the implanted volume in two applications.

RESULTS

Clinical local control was achieved in 152 (82%) of the 185 patients. A 5-year disease-free survival rate of 65%, 67%, 49%, and 17% was achieved for patients with Stage IB, II, III, and IV disease, respectively. Eighteen (10%) of the 185 patients developed Radiation Therapy Oncology Group Grade 3 or 4 late complications.

CONCLUSION

Patients with locally advanced cervical cancer, or with distorted anatomy, may be treated adequately with interstitial brachytherapy to achieve excellent locoregional control and a reasonable chance of cure with acceptable morbidity.

A comparison between tandem and ovoids and interstitial gynecologic template brachytherapy dosimetry using a hypothetical computer model

PURPOSE

To evaluate the dose distribution within the clinical target volume between two gynecologic brachytherapy systems---the tandem and ovoids and the Syed-Neblett gynecologic template---using a hypothetical computer model.

METHODS AND MATERIALS

Source positions of an intracavitary system (tandem and ovoids) and an interstitial system (GYN template) were digitized into the Nucletron Brachytherapy Planning System. The GYN template is composed of a 13-catheter implant (12 catheters plus a tandem) based on the Syed-Neblett gynecologic template. For the tandem and ovoids, the dwell times of all sources were evenly weighted to produce a pear-shaped isodose distribution. For the GYN template, the dwell times were determined using volume optimization. The prescribed dose was then normalized to point A in the intracavitary system and to a selected isodose line in the interstitial system. The treated volume in the two systems was kept approximately the same, and a cumulative dose-volume histogram of the treated volume was then generated with the Nucletron Brachytherapy Planning System to use for comparison. To evaluate the dose to a hypothetical target, in this case the cervix, a 2-cm-long, 3-cm-diameter cylinder centered along the tandem was digitized as the clinical target volume. The location of this hypothetical cervix was based on the optimal application of the brachytherapy system. A visual comparison of clinical target coverage by the treated volume on three different orthogonal planes through the treated volume was performed. The percentage dose-volume histograms of the target were generated for comparison. Multiple midline points were also placed at 5-mm intervals away from the tandem in the plane of the cervix to simulate the location of potential bladder and rectal dose points. Doses to these normal structures were calculated for comparison.

RESULTS

Although both systems covered the hypothetical cervix adequately, the interstitial system had a better coverage of the region lateral to the cervix. Smaller volumes of the vagina and uterine fundus received the full dose from the interstitial implant. The cumulative dose-volume histograms revealed larger high-dose regions within the treatment volume for the intracavitary system. The volumes receiving > or = 180% of the prescription dose were 31 cc and 17 cc for the intracavitary system and interstitial system, respectively. The isodose lines showed that most of this difference results from the high-dose region around the tandem. The percentage dose-volume histograms showed that a larger percentage of cervix received a higher dose in the intracavitary system. Fifty-two percent of the target volume received 200% or higher of the prescription dose with tandem and ovoids, compared with only 20% with the template system. Analysis of dose points outside of the 100% isodose lines showed a slightly more rapid dose drop-off with the interstitial system compared to the intracavitary system. Point doses at 20, 25, and 30 mm from the tandem in the interstitial system were 100%, 69%, and 51% of prescribed dose, and from the intracavitary system were 101%, 76%, and 58%, respectively.

CONCLUSIONS

Our dosimetric analysis revealed a better coverage in the parametrial regions, but underdosage of the central cervical region, for the interstitial system. On the other hand, because of the increased distance of source to dose point, there is a more rapid dose drop-off outside the treated volume with the interstitial system, which has the potential to improve tissue sparing. Based on this analysis, we caution against using a radiotherapy system with a homogeneous central dose distribution when treating cervical cancer with an intact uterus. We recommend differential loading of the implant catheters with the majority of dose delivered from the tandem when using an interstitial GYN template with remote afterloader.

The American Brachytherapy Society recommendations for low-dose-rate brachytherapy for carcinoma of the cervix

PURPOSE

This report presents guidelines for using low-dose-rate (LDR) brachytherapy in the management of patients with cervical cancer.

METHODS

Members of the American Brachytherapy Society (ABS) with expertise in LDR brachytherapy for cervical cancer performed a literature review, supplemented by their clinical experience, to formulate guidelines for LDR brachytherapy of cervical cancer.

RESULTS

The ABS strongly recommends that radiation treatment for cervical carcinoma (with or without chemotherapy) should include brachytherapy as a component. Precise applicator placement is essential for improved local control and reduced morbidity. The outcome of brachytherapy depends, in part, on the skill of the brachytherapist. Doses given by external beam radiotherapy and brachytherapy depend upon the initial volume of disease, the ability to displace the bladder and rectum, the degree of tumor regression during pelvic irradiation, and institutional practice. The ABS recognizes that intracavitary brachytherapy is the standard technique for brachytherapy for cervical carcinoma. Interstitial brachytherapy should be considered for patients with disease that cannot be optimally encompassed by intracavitary brachytherapy. The ABS recommends completion of treatment within 8 weeks, when possible. Prolonging total treatment duration can adversely affect local control and survival. Recommendations are made for definitive and postoperative therapy after hysterectomy. Although recognizing that many efficacious LDR dose schedules exist, the ABS presents suggested dose and fractionation schemes for combining external beam radiotherapy with LDR brachytherapy for each stage of disease. The dose prescription point (point A) is defined for intracavitary insertions. Dose rates of 0.50 to 0.65 Gy/h are suggested for intracavitary brachytherapy. Dose rates of 0.50 to 0.70 Gy/h to the periphery of the implant are suggested for interstitial implant. Use of differential source activity or loading minimizes excessive central dose rates. These recommendations are intended only as guidelines. The responsibility for medical decisions ultimately rests with the treating radiation oncologist.

CONCLUSION

Guidelines are suggested for LDR brachytherapy for cervical cancer. Practitioners and cooperative groups are encouraged to use these guidelines to formulate their treatment and dose-reporting policies.

Gynecologic brachytherapy I: Proper incorporation of brachytherapy into the current multimodality management of carcinoma of the cervix

The incidence of carcinoma of the cervix has continuously declined over the past decades because of effective screening. The International Federation of Gynecology and Obstetrics (FIGO) clinical staging, though universally used, is considered inadequate either to determine the type of treatment or to predict treatment outcome. Over the last 10 years, treatment of cervical cancer has become increasingly sophisticated with advances in external beam and brachytherapy in the radiotherapeutic management of this carcinoma. In particular, brachytherapy plays a major role in enhancing both local control and survival. Experience to date suggests that either high-dose-rate (HDR) or low-dose-rate (LDR) brachytherapy, when properly applied, can be effective and give similar rates of local control with minimal complications. This article analyzes the current literature regarding treatment techniques of radiotherapy with special emphasis on brachytherapy integration to optimize radiotherapy treatment outcome.

Low dose rate brachytherapy in the treatment of cervical carcinoma

The use of ICRT is a critical component in the successful treatment of cervical carcinoma with radiation therapy. Low dose rate ICRT allows optimization of the therapeutic ratio by utilizing physical and radiobiological principles. An optimal geometric relationship among the intracavitary applicators, the tumor, and other pelvic tissues is critically important in maximizing tumor control rates while simultaneously minimizing normal tissue complication rates. Treatment policies that have judiciously combined EBRT and LDR ICRT have achieved very high tumor control rates while maintaining acceptable complication rates. The use of HDR ICRT forfeits some of the radiobiological advantage of LDR ICRT. It remains to be determined whether this difference will have significant clinical consequences.

A new technique for performing Syed template interstitial implants for anterior vaginal tumors using an open retropubic approach

The Syed template (Alpha-Omega Services, Bellflower, CA) has been established as an advance in interstitial gynecologic brachytherapy. Unfortunately, enthusiasm for the technique is often tempered by certain tumor geometries which require blind insertion of the interstitial needles, potentially risking inaccurate placement of the radioactive sources and viscus perforation. These concerns arise particularly in the management of anterior vaginal tumors where difficulties in negotiating the pubic arch can prevent optimal needle placement. In answer to this problem, a technique utilizing an open retropubic approach for Syed template interstitial implants in anterior vaginal tumors under direct visualization is described. To date, six procedures have been performed. The disease entities include advanced cervical squamous cell carcinoma, clear cell carcinoma of the vagina, recurrent vaginal carcinoma, recurrent endometrial carcinoma, and urethral adenocarcinoma. Complete response was noted in five of six patients but persistent local control of disease was achieved in only one of five complete responses over a relatively short follow-up interval. Complications included paravaginal abscess (n = 1), postoperative deep venous thrombosis (n = 1), abdominal incision cellulitis (n = 1), and radiation enteritis (n = 1). An open retropubic approach allows direct visualization of the bladder and urethra during interstitial implantation of anterior vaginal malignancies and facilitates negotiation of the pubic arch. In our experience, this technique results in improved needle positioning and is thus intuitively likely to aid in avoiding injury to surrounding normal tissues. Additional accrual of a larger cohort will be necessary to arrive at any meaningful objective conclusions regarding the technique's benefit over current modalities.

Feasibility and tolerance of pulsed dose rate interstitial brachytherapy

PURPOSE

Pulsed dose rate (PDR) treatment is a new approach that associates the physical advantages of high-dose-rate (HDR) technology with the potential radiobiological advantages of low-dose-rate (LDR) brachytherapy. This retrospective study analyzes the feasibility, toxicity, and preliminary oncologic results in a series of 43 patients treated with PDR interstitial brachytherapy.

METHODS AND MATERIALS

Twenty-four patients with pelvic, 17 patients with head and neck, and 2 patients with breast cancers were treated. Twenty-eight patients had primary and 15 recurrent tumors; 14 had received prior external irradiation to the same site. The doses per pulse at the prescription isodose were 0.4-1 Gy (median 0.5 Gy), delivered using a single cable-driven 0.3-1.0 Ci 192-iridium source (PDR Nucletron Micro-Selectron).

RESULTS

The median treated volumes (at the prescribed isodose) were 28 cc for pelvic, 8.33 cc for head and neck, and 40 cc for breast malignancies. Of 14,499 source and 14,499 dummy source transfer procedures, 3 technical machine failure events were observed (0.02%). Grade 3 acute toxicities were seen in 5/43 patients (4 oral stomatitis, 1 vaginal mucositis) and grade 4 acute toxicity in one patient (rectovaginal fistula). Grade 3-4 late complications were observed in 4/41 (9.8%) patients: 1 pubic fracture, 1 rectovaginal fistula, 1 vesicovaginal fistula and 1 local necrosis. With a median follow-up of 18 months, 10/41 patients progressed locoregionally (6 pelvic, 4 head and neck), 3 developed local recurrence and distant metastasis (3 pelvic), 3 only distant metastasis (2 pelvic, 1 head and neck). Two patients are lost to follow-up.

CONCLUSION

PDR interstitial brachytherapy for pelvic, head and neck, and breast malignancies is feasible and the acute and late toxicities seem acceptable. Although the physical advantages of PDR are clear, further follow-up is required to determine how results compare with those obtained with standard LDR brachytherapy.

Customized gynecologic interstitial implants: CT-based planning, dose evaluation, and optimization aided by laparotomy

PURPOSE

Interstitial perineal implants may be utilized to deliver a high local radiation dose in the treatment of advanced gynecologic malignancies. Lack of knowledge of the precise anatomic relationships between the implant and the target and critical organs may limit efficacy and increase complication risks. Computed tomography (CT)-based planning, dose evaluation, and optimization of customized interstitial implants, aided by laparotomy, have been developed to overcome these limitations.

METHODS AND MATERIALS

Twenty patients with locally advanced gynecologic malignancies treated between May 1990 to October 1996 with external irradiation and one or two implants. Interstitial implants were performed when intracavitary brachytherapy was judged to be inadequate or when the response to external radiation and an intracavitary implant was not satisfactory. Customized interstitial implants were planned using preimplantation CT to determine catheter angles and paths that best implanted the target while avoiding pelvic bones and organs. Laparotomy aimed at lysing bowel adhesions, placement of omental carpet, and refining needle placement. Postimplantation CT was used for loading optimization and dose evaluation.

RESULTS

Catheter angles 15-25 degrees were found to adequately implant anteriorly laying targets while avoiding pubic bones and bladder. Adhesiolysis of bowel loops from the vaginal apex was required in patients with prior hysterectomy. Small modifications in catheter placements were made during laparotomy in all implants. Postimplantation CTs showed deviations of the catheter positions compared with the planning CTs and were essential in determining target and organ doses and loading optimization. At a median follow-up of 42 months (range: 9-80 months), local control rate is 55% and disease-free survival 40%. Late complications occurred in 2 of 11 of patients without local recurrence.

CONCLUSIONS

CT-based planning, loading optimization, and dose evaluation of customized implants improve radiation dose delivery. Laparotomy enhances implant accuracy and safety. Local tumor control rate is still unsatisfactory. It reflects the shortcomings of technical advances alone in poor prognosis tumors like those selected for this series.

A comparison of intracavitary versus interstitial irradiation in the treatment of cervical cancer

OBJECTIVE

Management of locally advanced cervical cancer consists primarily of combination external and internal radiation. In order to investigate the impact of intracavitary brachytherapy versus interstitial brachytherapy on local tumor control, survival, and complications, we retrospectively reviewed the concomitant experience of two institutions, each of which practice exclusively one of these radiotherapeutic techniques.

METHODS

Between 1979 and 1989, 61 patients with bulky stage II, III, or IVA cervical cancer were treated using a combination of teletherapy and intracavitary brachytherapy at one institution, while 70 similar patients were treated with teletherapy and interstitial brachytherapy at another institution. Patients in both groups were similar with respect to age, FIGO stage, tumor size, surgical stage, and histologic subtype. Patients treated with intracavitary therapy received a mean cumulative dose of 7706 cGy to point A and 5523 cGy to point B using standard Fletcher-Suit techniques. Those who received interstitial irradiation were treated with a mean external dose of 5050 cGy and 2 interstitial implants using a transperineal Syed-Neblett template with a mean tumor dose of 2239 and 1,942 cGy with each application, respectively. Patients treated with chemoradiation were excluded from this review.

RESULTS

Although initial rates of local control were not different, prolonged 5-year disease-free survival (50% vs 21%, P = 0.01) and improved 5-year local control (61% vs 32%, P = 0.01) were observed among patients with stage II disease treated with intracavitary irradiation. No statistical differences in survival could be detected among stage III and IVA patients. Women treated with intracavitary irradiation received a larger dose of brachytherapy than those treated with interstitial therapy (4608 vs 3504 radium milligram hours equivalent, P < 0.0001) because a tandem was only used in 17 (24%) interstitial implants. Major complications occurred in 21% of patients in each group.

CONCLUSION

When a tandem is infrequently used during interstitial brachytherapy, the toxicity is similar to that of intracavitary techniques. However, more relapses are observed among patients with stage II lesions treated with interstitial irradiation.

Pulsed low dose rate brachytherapy for pelvic malignancies

PURPOSE

The pulsed low dose rate remote afterloading unit was designed to combine the radiation safety and isodose optimization advantages of high dose rate technology with the radiobiologic advantages of continuous low dose rate brachytherapy. This is the first report of a prospective clinical trial evaluating the relative incidence of acute toxicity and local control in patients with pelvic malignancies who underwent interstitial or intracavitary brachytherapy with the pulsed low dose rate remote afterloader.

METHODS AND MATERIALS

From 5/11/92-6/21/95, 65 patients underwent 77 brachytherapy procedures as part of their treatment regimen for pelvic malignancies. Using the pulsed low dose rate Selectron, equipped with a single cable-driven 0.3-1.0 Ci Ir192 source, target volume doses of 0.40-0.85 Gy per pulse were prescribed to deliver the clinically determined dose. Forty-five intracavitary and 32 interstitial procedures were performed. Fifty-four patients had primary and 11 recurrent disease. Patients were followed closely to assess incidence of Grade 3-5 acute and delayed toxicity, local control, and survival.

RESULTS

With a median follow-up of 16.1 months (range 1-29), 33 patients are NED, 10 alive with disease, 13 dead with disease, 4 dead of intercurrent disease, and 5 lost to follow-up. Local control was maintained until last follow-up or death in 48 cases, local failure occurred in 11, unknown in 5. Grade 3-5 acute toxicities (requiring medical or surgical intervention) occurred in 5 out of 77 procedures (6.5%), delayed complications in 10 patients (15% actuarial incidence at 2 years). In the 52 procedures performed for 42 patients with cervix cancer, the acute toxicity incidence was 5.8%, with a 14% 2-year actuarial incidence of delayed complications. Of 32 interstitial templates performed on 30 patients for pelvic malignancies, there were three incidences of acute toxicity and five delayed toxicities.

CONCLUSION

Using the parameters described for this initial clinical study in patients treated for pelvic malignancies, pulsed low dose rate brachytherapy shows no significant increase in acute toxicity above that seen with the standard continuous low dose rate approach. Using the isodose optimization possible with pulsed brachytherapy, local control is excellent in patients treated at initial presentation, although longer follow-up is required for full assessment of local control and late toxicity. Further trials will need to be carried out to determine if larger doses per pulse and shorter total treatment times have comparable therapeutic ratios.

CT-guided interstitial implantation of gynecologic malignancies

PURPOSE

To establish the efficacy of computed tomography (CT)-based planning and analysis of transperineal implants.

METHODS AND MATERIALS

For patients with bulky disease or geometrically unfavorable anatomy, transperineal interstitial implantation of gynecologic tumors offers an alternative to standard intracavitary techniques. Control of dose rate and total dose distributions to produce a homogenous, low dose rate implant presents a challenge to the radiation oncologist in these complex implants, as does the relationship of these distributions to the patients's anatomy. We have used CT imaging following needle implantation, prior to source loading, in 25 patients (28 implants), as an aid in both the planning of the implant and the analysis of the dosimetry.

RESULTS

The spatial relationship between the needles and the normal anatomy can be clearly defined, despite the presence of some artifacts. Tumor volume is less clearly visualized but the adequacy of needle placement can be assessed and adjusted if necessary. Modifications of the planned source placement, based upon the location of specific needles and critical structures, can be made prior to loading the patient. Dose rate and total dose distributions are displayed with the appropriate anatomy on axial images and on reconstructed sagittal and coronal planes. Multiple points of dose specification for the rectum and the bladder are easily defined. Dose rate adjustment can be made by selectively changing the activity associated with a particular needle or needles. Multiple implants as well as external beam irradiation can also be integrated.

CONCLUSIONS

CT-based dosimetry has permitted intelligent planning decisions to be made prior to and during these implants. It has further allowed more accurate anatomically based dosimetric analysis, with visualization and control of dose rate and total dose distributions displayed together with the patient's anatomy. This more elaborate analysis should ultimately lead to a better understanding of the reasons for local control and complications and their relationships to dose rate, total dose, and volume.

A new perineal template assembly for high-dose-rate interstitial brachytherapy of gynecologic malignancies

This technical note introduces a modified Syed-Neblett type perineal template for high-dose-rate interstitial brachytherapy of gynecologic malignancies. The template can easily be disassembled after the insertion of the central needles into the pelvis allowing the cystoscopic and rectoscopic control of the needle positions. Thus needles penetrating the bladder or the rectum are recognized and can be repositioned before reassembling the template. Elimination of hot irradiation zones in tumor-free bladder and rectum walls might lead to reduction of severe late complications without compromising the therapeutic efficacy.

Carcinoma of the cervical stump: a review of 213 cases

From 1970 to 1987, 213 cases of carcinoma of the cervical stump were accrued in a multi-institutional prospective cooperative study. This group accounted for 5.5% of cervical carcinoma diagnosed during the same period. 13 had in situ carcinoma and 200 had invasive carcinoma (96% squamous cell carcinoma, 4% adenocarcinoma). Radiotherapy alone (external and brachytherapy) was given to 77%, brachytherapy and surgery to 15% and surgery alone to 8%). FIGO stage distribution was: I (31%), IIa (15%), IIb (27%), IIIa (5%), IIIb (17%) and IV (5%). Five-year locoregional control per stage was 100% in Ia, 85% in Ib, 82% in IIa, 71% in IIb, 45% in IIIa, 54% in IIIb and 30% in IV. Corrected 5-year survival per stage was 82% in Ib, 78% in IIa, 73% in IIb, 69% in IIIa, 38% in IIIb and 0% in IV. The diameter of disease in stage II strongly influenced the 5-year locoregional control (81% for tumours of less than 3 cm vs. 68% for tumours more than 3 cm). Lymphangiogram was associated with a 44.5% 5-year locoregional control when positive vs. 74% when non-positive. Brachytherapy was advantageous in obtaining locoregional control in patients receiving external irradiation and brachytherapy: 81.5% vs. 38.5% in patients treated with external radiotherapy alone. Surgery was performed only for in situ carcinoma and for part of stages Ia, Ib and IIa. There is no significant difference in locoregional control at equal stage between radiotherapy alone and treatment schemes including surgery. However, lethal complications were observed in 6% of the patients of the surgical group as compared to 0.6% of the patients treated with radiotherapy alone. Radical radiotherapy seems to provide similar results of locoregional control and survival at equal stages in carcinoma of the cervical stump compared to carcinoma developed on an intact uterus. The rate of severe complications reported with the French-Italian glossary is 13% for G3 and 3% for G4, which is close to the observed rate during the same period in our series of radical radiotherapy to the intact uterus.

The use of CT-based 3-D anatomical modeling in the design of customized perineal templates for interstitial gynecologic implants

A system for preplanning interstitial treatment of gynecologic malignancies with a CT-based 3-dimensional planning system is presented. The preplan produces a custom template design that optimizes catheter placement. The procedure begins with a CT scan with a vaginal cylinder and blank template in place. Contours of the anatomic structures of interest, cylinder, and template are entered into the system, and 3-D surfaces are generated. The first view evaluated is oriented in a "cylinder's-eye view," which shows the path of the catheters placed parallel to the cylinder. In most cases this path to the tumor is obstructed by the pubic bones and bladder. By rotating the view posteriorly, the catheters can travel under the symphysis and bladder to the tumor. Once the optimum angle for visualization of the tumor has been determined, an array of catheters is designed to optimize the dose to the tumor. This array includes the special distribution in the oblique plane as well as the depth of insertion for each catheter. The design is then used in drilling the appropriate guide holes in the template. Orthogonal film dosimetry as well as CT verification of source placement will be compared to the preplan distribution.

Transperineal templates for brachytherapy treatment of pelvic malignancies--a comparison of standard and customized templates

A technique is described for the design and construction of customized templates for transperineal implants and interstitial hyperthermia of pelvic malignancies. The design of the template and the distribution of the transperineal Iridium-192 seed ribbons are based on prior optimization of the dose distribution. The target volume is defined by means of pelvic examination and pertinent radiographic studies including a CT. The pelvic CT study is obtained with a plastic obturator in the rectum or the vagina. The obturator is used as a reference structure for aligning the target contour from each image plane to form a composite 2-dimensional contour of maximum tumor extent in a plane perpendicular to the obturator. Dose distributions are calculated to determine the placement of the Iridium-192 seed ribbons in the template. Laparoscopic guidance is used for actual placement of brachytherapy source needles together with a rectal or vaginal obturator to stabilize the template and to assure that the needle placement conforms with the planned geometry. Dose distributions for 10 consecutive patients calculated for customized templates as well as for five commercially available standard templates show that the customized templates are superior to standard templates in that the planned dose distribution matches the configuration of the target volume and is more uniform than with standard templates.

Advances in radiotherapy in the gynecologic malignancies

We review, for their wider applicability, four advances in the radiotherapeutic management of the gynecologic malignancies. Attempts at improving upon results obtained with radiotherapy by the addition of chemotherapy have usually followed one of two temporal strategies: Sequential chemotherapy-radiotherapy (so-called neo-adjuvant chemotherapy), or chemotherapy given concurrently with radiotherapy. The pros and cons of both models are discussed. Recent work suggests that there is a differential response between the acutely reacting normal tissues, as well as tumor, and the late-reacting normal tissues, which is dependent upon the radiation fraction size. The rationale and some important clinical applications are reviewed. Advances in brachytherapy include the high dose rate treatment and the use of rigid templates to guide the accurate placement of the interstitial implant. The controversies surrounding these approaches require further study before the precise place of these techniques is known. Finally, in vulvar cancer, the addition of radiotherapy to surgery is being studied to permit less radical operations in early disease, and greater local tumor control in advanced disease.