Magnetic resonance imaging in the treatment planning of radiation therapy in carcinoma of the cervix treated with the four-field pelvic technique

A practical review of magnetic resonance imaging for the evaluation and management of cervical cancer

Cervical cancer is a leading cause of mortality in women worldwide. Staging and management of cervical cancer has for many years been based on clinical exam and basic imaging such as intravenous pyelogram and x-ray. Unfortunately, despite advances in radiotherapy and the inclusion of chemotherapy in the standard plan for locally advanced disease, local control has been unsatisfactory. This situation has changed only recently with the increasing implementation of magnetic resonance image (MRI)-guided brachytherapy. The purpose of this article is therefore to provide an overview of the benefits of MRI in the evaluation and management of cervical cancer for both external beam radiotherapy and brachytherapy and to provide a practical approach if access to MRI is limited.

MRI simulation for radiotherapy treatment planning

Over the last two decades, the computed tomography simulator became the standard of the contemporary radiotherapy treatment planning (RTP) process. Along the same time, the superb soft tissue contrast of magnetic resonance imaging (MRI) was widely incorporated into RTP through the process of image coregistration. This review summarizes the efforts of incorporation of MRI data into target definition process for RTP based on gained clinical evidence so far and opens a question whether the time is up for bringing a MRI-simulator as an additional standard imaging tool into radiation oncology departments.

Magnetic resonance imaging for adaptive cobalt tomotherapy: A proposal

Magnetic resonance imaging (MRI) provides excellent soft tissue contrast for oncology applications. We propose to combine a MRI scanner with a helical tomotherapy (HT) system to enable daily target imaging for improved conformal radiation dose delivery to a patient. HT uses an intensity-modulated fan-beam that revolves around a patient, while the patient slowly advances through the plane of rotation, yielding a helical beam trajectory. Since the use of a linear accelerator to produce radiation may be incompatible with the pulsed radiofrequency and the high and pulsed magnetic fields required for MRI, it is proposed that a radioactive Cobalt-60 ((60)Co) source be used instead to provide the radiation. An open low field (0.25 T) MRI system is proposed where the tomotherapy ring gantry is located between two sets of Helmholtz coils that can generate a sufficiently homogenous main magnetic field.It is shown that the two major challenges with the design, namely acceptable radiation dose rate (and therefore treatment duration) and moving parts in strong magnetic field, can be addressed. The high dose rate desired for helical tomotherapy delivery can be achieved using two radiation sources of 220TBq (6000Ci) each on a ring gantry with a source to axis-of-rotation distance of 75 cm. In addition to this, a dual row multi-leaf collimator (MLC) system with 15 mm leaf width at isocentre and relatively large fan beam widths between 15 and 30 mm per row shall be employed. In this configuration, the unit would be well-suited for most pelvic radiotherapy applications where the soft tissue contrast of MRI will be particularly beneficial. Non-magnetic MRI compatible materials must be used for the rotating gantry. Tungsten, which is non-magnetic, can be used for primary collimation of the fan-beam as well as for the MLC, which allows intensity modulated radiation delivery. We propose to employ a low magnetic Cobalt compound, sycoporite (CoS) for the Cobalt source material itself.Rotational delivery is less susceptible to problems related to the use of a low energy megavoltage photon source while the helical delivery reduces the negative impact of the relatively large penumbra inherent in the use of Cobalt sources for radiotherapy. On the other hand, the use of a (60)Co source ensures constant dose rate with gantry rotation and makes dose calculation in a magnetic field as easy as the range of secondary electrons is limited.The MR-integrated Cobalt tomotherapy unit, dubbed 'MiCoTo,' uses two independent physical principles for image acquisition and treatment delivery. It would offer excellent target definition and will allow following target motion during treatment using fast imaging techniques thus providing the best possible input for adaptive radiotherapy. As an additional bonus, quality assurance of the radiation delivery can be performed in situ using radiation sensitive gels imaged by MRI.

Ressonância magnética para avaliação dos limites dos campos clássicos de radioterapia em pacientes portadoras de neoplasia maligna de colo uterino

OBJETIVO: Avaliar os limites de campo padronizados para radioterapia de neoplasia maligna de colo uterino com o uso de ressonância magnética e verificar a importância deste exame na redução de possíveis erros de planejamento com técnica convencional. MATERIAIS E MÉTODOS: Foram analisados, retrospectivamente, exames de ressonância magnética do planejamento de 51 pacientes tratadas devido a neoplasia de colo uterino. Os parâmetros estudados foram limites anterior e posterior no corte sagital. RESULTADOS: Observou-se, no corte sagital das ressonâncias magnéticas, que o limite de campo anterior apresentou-se inadequado em 20 (39,2%) pacientes e que houve perda geográfica em 37,3% dos casos no limite posterior. A inadequação de ambos os limites de campo não se relacionou com parâmetros clínicos como idade das pacientes, estadiamento, tipo e grau histológico. CONCLUSÃO: A avaliação dos limites de campo padronizados pela literatura com o uso de ressonância magnética mostrou altos índices de inadequação dos limites do campo lateral, assim como a importância do uso deste exame no planejamento radioterápico de pacientes portadoras de câncer de colo uterino com a finalidade de reduzir a perda geográfica no volume alvo de tratamento.

Evaluation of pelvic lymph node coverage of conventional radiotherapy fields based on bony landmarks in Chinese cervical cancer patients using CT simulation

OBJECTIVE

To evaluate the pelvic lymph node coverage of conventional pelvic fields based on bony landmarks in Chinese patients with cervical cancer by using computed tomography (CT) simulation images to contour pelvic vessels as substitutes for lymph nodes location.

METHODS

A retrospective review of CT simulation images and conventional pelvic radiation planning data sets was performed in 100 patients with cervical cancer at the International Federation of Gynecology and Obstetrics (FIGO) Stage IIB to IIIB in our hospital. Pelvic arteries were contoured on CT simulation images, and the outlines of conventional pelvic fields were drawn as defined by the gynecologic oncology group (GOG) after hiding the contours. The distances between the following vessel contours and field borders were measured: D(1), the superior border of the anterior/posterior (AP) field and the bifurcation of abdominal aorta; D(2), the ipsilateral border of the AP field and the distal end of external iliac artery; and D(3), the anterior border of the lateral (LAT) field and the distal end of the external iliac artery. The distances were recorded as positive values if the measuring point was within the conventional pelvic fields, or they were recorded as negative values. Lymph nodes coverage was considered adequate when D(1)(0 mm, D(2)(17 mm or D(3)(7 mm.

RESULTS

All patients had at least 1 inadequate margin, 97 patients (97.0%) had 2, and 22 patients (22.0%) had all the 3. On the AP field, 95 patients (95%) had the measuring point, the bifurcation of the abdominal aorta, out of the field (D(1)<0 mm), and all the patients had a distance less than 17.0 mm between the distal end of the external iliac artery and ipsilateral border (D(2)<17.0 mm). On the LAT field, 24 patients (24%) had a distance less than 7.0 mm between the distal end of the external iliac artery and anterior border (D(3)<7.0 mm).

CONCLUSION

We observed that conventional pelvic fields based on bony landmarks provided inadequate coverage of pelvic lymph nodes in our patients with cervical cancer. CT simulation may be a feasible technique for planning pelvic fields optimally and individually.

Conformal and intensity-modulated radiotherapy for cervical cancer

Three-dimensional radiotherapy planning techniques, including conformal radiotherapy and intensity-modulated radiotherapy, have potential for improving outcomes in cervical cancer. Accurate target volume definition is essential in order to maximise normal tissue sparing while minimising the risk of a geographical miss. This reduction in toxicity provides the option of dose escalation, particularly with simultaneous integrated boost intensity-modulated radiotherapy. The evidence for the current use and potential applications of these techniques in the treatment of cervical cancer are discussed.

An assessment of interfractional uterine and cervical motion: implications for radiotherapy target volume definition in gynaecological cancer

PURPOSE

To assess interfractional movement of the uterus and cervix in patients with gynaecological cancer to aid selection of the internal margin for radiotherapy target volumes.

METHODS AND MATERIALS

Thirty-three patients with gynaecological cancer had an MRI scan performed on two consecutive days. The two sets of T2-weighted axial images were co-registered, and the uterus and cervix outlined on each scan. Points were identified on the anterior uterine body (Point U), posterior cervix (Point C) and upper vagina (Point V). The displacement of each point in the antero-posterior (AP), superior-inferior (SI) and lateral directions between the two scans was measured. The changes in point position and uterine body angle were correlated with bladder volume and rectal diameter.

RESULTS

The mean difference (+/-1 SD) in Point U position was 7 mm (+/-9.0) in the AP direction, 7.1 mm (+/-6.8) SI and 0.8 mm (+/-1.3) laterally. Mean Point C displacement was 4.1 mm (+/-4.4) SI, 2.7 mm (+/-2.8) AP, 0.3 (+/-0.8) laterally, and Point V was 2.6 mm (+/-3.0) AP and 0.3 mm (+/-1.0) laterally. There was correlation for uterine SI movement in relation to bladder filling, and for cervical and vaginal AP movement in relation to rectal filling.

CONCLUSION

Large movements of the uterus can occur, particularly in the superior-inferior and anterior-posterior directions, but cervical displacement is less marked. Rectal filling may affect cervical position, while bladder filling has more impact on uterine body position, highlighting the need for specific instructions on bladder and rectal filling for treatment. We propose an asymmetrical margin with CTV-PTV expansion of the uterus, cervix and upper vagina of 15 mm AP, 15 mm SI and 7 mm laterally and expansion of the nodal regions and parametria by 7 mm in all directions.

Online MRI guidance for healthy tissue sparing in patients with cervical cancer: an IMRT planning study

BACKGROUND AND PURPOSE

During cervical cancer treatment, target volumes change position and shape due to organ motion and tumour regression. An MRI-accelerator will provide information on these changes by online magnetic resonance imaging (MRI) guidance throughout each treatment fraction. The purpose of this intensity-modulated radiation therapy (IMRT) planning study is to assess the benefit of online MRI guidance in healthy tissue sparing.

MATERIALS AND METHODS

Weekly MRI scans of 11 cervical cancer patients were used. We created four IMRT plans per patient, based on these weekly MRI scans, to simulate an online-IMRT approach. We applied a primary and nodal planning target volume (PTV) margin of 4 mm. As reference, we created an IMRT plan based on the pre-treatment MRI scan (pre-IMRT) using a primary and nodal PTV margin of 15 and 10 mm. The weekly defined bladder, rectum, bowel, and sigmoid contours were evaluated on the online-IMRT and pre-IMRT dose distributions at six dose levels (V10(Gy), V20(Gy), V30(Gy), V40(Gy), V42.8(Gy), and V45(Gy)).

RESULTS

Online-IMRT compared to pre-IMRT significantly reduced the volume of healthy tissue irradiated to all dose levels, except V10(Gy).

CONCLUSIONS

Online MRI guidance reduces healthy tissue involvement in patients with cervical cancer.

Motion and deformation of the target volumes during IMRT for cervical cancer: what margins do we need?

BACKGROUND AND PURPOSE

For cervical cancer patients the CTV consists of multiple structures, exhibiting complex inter-fraction changes. The purpose of this study is to use weekly MR imaging to derive PTV margins that accommodate these changes.

MATERIALS AND METHODS

Twenty patients with cervical cancer underwent a T2-weighted MRI exam before and weekly during IMRT. The CTV, GTV and surrounding organs were delineated. PTV margins were derived from the boundaries of the GTV and CTV in the six main directions and correlated with changes in the volumes of organs at risk.

RESULTS

Around the GTV a margin of 12, 14, 12, 11, 4 and 8mm to the anterior, posterior, right lateral, left lateral, superior and inferior directions was needed. The CTV required margins of 24, 17, 12, 16, 11 and 8 mm. The shift of the GTV and CTV in the AP directions correlated weakly with the change in rectal volume. For the bladder the correlations were even weaker.

CONCLUSIONS

We used weekly MRI scans to derive inhomogeneous PTV margins that accommodate changes in GTV and CTV. The weak correlations with rectum and bladder volume suggest that measures to control filling status of these organs may not be very effective.

The use of MRI in planning radiotherapy for gynaecological tumours

Parameters that significantly influence results in radiation treatment of gynaecological malignancies are mainly related to the tumour characteristics and the radiotherapy technique used. High-dose radiotherapy requires accurate localisation of the tumour volume and its relationship to surrounding normal tissues. For many years the standard technique used for irradiation of the pelvic area was the four-field box technique which offered the potential benefit of the lateral fields to shield the rectum and small bowel. However, this conventional technique was designed according to bony landmarks and offered limited information regarding the topography of the tumour and the flexion of the uterus which are influenced by the tumour burden and bladder and rectal filling. CT and MRI enable the visualisation of the cervix, uterus, vagina, iliac vessels and organs at risk, but MRI allows tumour depiction in all planes. In the early 1990s, several studies reported on the value of pelvic MRI in designing the lateral fields of the box technique. They demonstrated that conventional lateral portals would have resulted in a marginal tumour miss and incomplete coverage of the uterine fundus in more than 50% of cases, thus leading to the conclusion that if a box technique is used its design should be based on sagittal MRI. CT-based 3D planning systems are now routinely used in the vast majority of radiotherapy departments. Target volumes and organs at risk are delineated by the physician on each CT slice in order to conform the radiotherapy fields to the tumour volume. For several reasons, such as distortion and lack of electron density which is essential for dose calculation, the implementation of MRI into radiation treatment planning has its limitations. However, MRI can still be used if planning systems integrate tools for CT/MR image registration. There is little experience in the literature for gynaecological malignancies demonstrating that image fusion allows an improvement of the definition of the target and the organ at risk compared to CT alone. Only a few papers in the literature report on the use of CT/MR image registration in planning the external irradiation of gynaecological tumours. Most demonstrate feasibility, but they fail to quantify the improvement for volume definition compared to the use of CT alone. Finally, recent possibilities offered by MRI technology are promising in the area of brachytherapy planning as the full potential of individually defining and evaluating GTV and CTV based on tumour extent and anatomical structures is exploited.

Evaluation of Late Toxicities of Patients with Carcinoma of the Cervix Treated with Radical Radiotherapy: An Audit from India

AIMS

To evaluate the incidence of, and factors affecting, late toxicities of women with carcinoma of the cervix treated with radical radiotherapy.

MATERIALS AND METHODS

Between 1996 and 2001, 1069 women with carcinoma of the cervix (stage I-IVA) were treated at our centre with external-beam radiotherapy (EBRT) and intra-cavitary radiotherapy (ICRT) (n = 871) or EBRT alone (n = 198). Median follow-up was 34 months. Median dose to point A was 81 Gy.

RESULTS

Five-year actuarial incidence of overall (all grades) and severe (grade 3/4) late toxicities in the rectum, bladder, small intestine and subcutaneous tissue were 12.3% and 1.1%, 11.2% and 1.2%, 9.2% and 0.2%, and 23.1% and 1.2%, respectively. Vaginal adhesions were seen in 29.6% of cases and stenosis in 33.9% of cases. On multivariate analysis, factors adversely affecting overall incidence of proctitis were anterior-posterior (AP) separation of patient more than 18 cm and presence of comorbid diseases. Presence of comorbid diseases was the only factor affecting the incidence of severe proctitis (grade 3/4). AP separation more than 18 cm adversely affected the incidence of cystitis, both overall and severe. Late toxicities (all grades) in small bowel were increased in subsets, like women younger than 50 years and women with comorbid diseases, but no factor emerged as significant for incidence of severe toxicities. Subcutaneous fibrosis was significantly higher in patients with AP separation over 18 cm, those treated by cobalt machines and those who received EBRT only. Severe subcutaneous fibrosis was influenced by the use of EBRT alone. Overall incidence of vaginal toxicity was higher in women whose overall treatment time (OTT) was shorter and in women who received ICRT. Vaginal stenosis was higher in elderly women and in women who received ICRT by low dose rate.

CONCLUSIONS

Even with telecobalt machines, impressive results with acceptable late toxicity can be achieved in the treatment of cancer of the cervix using an ideal combination of EBRT with ICRT.

Assessment of tumor regression by consecutive pelvic magnetic resonance imaging and dose modification during high-dose-rate brachytherapy for carcinoma of the uterine cervix

PURPOSE

To assess tumor regression, as determined by pelvic magnetic resonance imaging (MRI), and evaluate the efficacies and toxicities of the interim brachytherapy (BT) modification method, according to tumor regression during multi-fractionated high-dose-rate (HDR) BT for uterine cervical cancer.

MATERIALS AND METHODS

Consecutive MRI studies were performed pre-radiotherapy (RT), pre-BT and during interfraction of BT (inter-BT) in 69 patients with cervical cancer. External beam radiotherapy (EBRT) was performed, using a 10 MV X-ray, in daily fraction of 1.8 Gy with 4-fields, 5 d/wk. Radiation was delivered up to 50.4 Gy, with midline shielding at around 30.6 Gy. Of all 69 patients, 50 received modified interim BT after checking the inter-BT MRI. The BT was delivered in two sessions; the first was composed of several 5 Gy fractions to point A, twice weekly, using three channel applicators. According to the three measured orthogonal diameters of the regressed tumor, based on inter-BT MR images, the initial BT plan was modified, with the second session consisting of a few fractions of less than 5 Gy to point A, using a cervical cylinder applicator.

RESULTS

The numbers of patients in FIGO stages Ib, IIa, IIb and IIIb+IVa were 19 (27.5%), 18 (26.1%), 27 (39.2%) and 5 (7.2%), respectively. Our treatment characteristics were comparable to those from the literatures with respect to the biologically effective dose (BED) to point A, rectum and bladder as reference points. In the regression analysis a significant correlation was observed between tumor regression and the cumulative dose to point A on the follow-up MRI. Nearly 80% regression of the initial tumor volume occurred after 30.6 Gy of EBRT, and this increased to 90% after an additional 25 Gy in 5 fractions of BT, which corresponds to 73.6 Gy of cumulative BED(10) to point A. The median total fraction number, and those at the first and second sessions of BT were 8 (5 approximately 10), 5 (3 approximately 7) and 3 (1 approximately 5), respectively. The median follow-up time was 53 months (range, 9 approximately 66 months). The 4-year disease-free survival rate of all patients was 86.8%. Six (8.7%) patients developed pelvic failures, but major late complications developed in only two (2.9%).

CONCLUSION

Our study shows that effective tumor control, equivalent survival and low rates of major complications can be achieved by modifying the fraction size during BT according to tumor regression, as determined by consecutive MR images. We recommend checking the follow-up MRI at a cumulative BED(10) of around 65 Gy to point A, with the initial BT modified at a final booster BT session.

Accuracy of finite element model-based multi-organ deformable image registration

As more pretreatment imaging becomes integrated into the treatment planning process and full three-dimensional image-guidance becomes part of the treatment delivery the need for a deformable image registration technique becomes more apparent. A novel finite element model-based multiorgan deformable image registration method, MORFEUS, has been developed. The basis of this method is twofold: first, individual organ deformation can be accurately modeled by deforming the surface of the organ at one instance into the surface of the organ at another instance and assigning the material properties that allow the internal structures to be accurately deformed into the secondary position and second, multi-organ deformable alignment can be achieved by explicitly defining the deformation of a subset of organs and assigning surface interfaces between organs. The feasibility and accuracy of the method was tested on MR thoracic and abdominal images of healthy volunteers at inhale and exhale. For the thoracic cases, the lungs and external surface were explicitly deformed and the breasts were implicitly deformed based on its relation to the lung and external surface. For the abdominal cases, the liver, spleen, and external surface were explicitly deformed and the stomach and kidneys were implicitly deformed. The average accuracy (average absolute error) of the lung and liver deformation, determined by tracking visible bifurcations, was 0.19 (s.d.: 0.09), 0.28 (s.d.: 0.12) and 0.17 (s.d.: 0.07) cm, in the LR, AP, and IS directions, respectively. The average accuracy of implicitly deformed organs was 0.11 (s.d.: 0.11), 0.13 (s.d.: 0.12), and 0.08 (s.d.: 0.09) cm, in the LR, AP, and IS directions, respectively. The average vector magnitude of the accuracy was 0.44 (s.d.: 0.20) cm for the lung and liver deformation and 0.24 (s.d.: 0.18) cm for the implicitly deformed organs. The two main processes, explicit deformation of the selected organs and finite element analysis calculations, require less than 120 and 495 s, respectively. This platform can facilitate the integration of deformable image registration into online image guidance procedures, dose calculations, and tissue response monitoring as well as performing multi-modality image registration for purposes of treatment planning.

Conventional 4-field box radiotherapy technique for cancer cervix: potential for geographic miss without CECT scan-based planning

BACKGROUND

The advantage of 4-field radiation to the pelvis is that the use of lateral portals spares a portion of the small bowel anteriorly and rectum posteriorly. The standard lateral portals defined in textbooks are not always adequate especially in advanced cancer cervix.

METHODS

An analysis was done to determine adequacy of margins of standard lateral pelvic portals with CECT defined tumor volumes. The study included 40 patients of FIGO stage IIB and IIIB treated definitively for cancer cervix between 1998 and 2000. An inadequate margin was defined if the cervical growth and uterus were not encompassed by the 95% isodose.

RESULTS

An inadequate posterior margin was common with bulky disease (P = 0.06) and with retroverted uterus (P = 0.08). Menopausal status, FIGO stage, associated myoma, and age were of no apparent prognostic significance. Bulk retained significant on multivariate analysis. An inadequate anterior margin was common in premenopausal (P = 0.01); anteverted uterus (P = 0.02); associated myoma (P = 0.01); and younger patients (P = 0.03). It was not influenced by bulk or stage. Menopausal status and associated myoma retained significant on multivariate analysis.

CONCLUSION

Without the knowledge of precise tumor volume, the 4-field technique with standard portals is potentially risky as it may under dose the tumor through lateral portals and the standard AP/ PA portals are a safer option.

Clinical and anatomical guidelines in pelvic cancer contouring for radiotherapy treatment planning

BACKGROUND AND PURPOSE

Many observations on potential inadequate coverage of tumour volume at risk in advanced cervical cancer (CC) when conventional radiation fields are used, have further substantiated by investigators using MRI, CT or lymphangiographic imaging. This work tries to obtain three dimensional margins by observing enlarged nodes in CT scans in order to improve pelvic nodal chains clinical target volumes (CTVs) drawing, and by looking for corroborative evidence in the literature for a better delineation of tumour CTV.

METHOD

Eleven consecutive patients (seven males, four females, mean age 62 years, range 43-78) with CT diagnosis of nodal involvement caused by pathologically proved carcinoma of the cervix (n = 2), carcinoma of the rectum (n = 2), carcinoma of the prostate (n = 2), non-Hodgkin lymphoma (n = 2), Hodgkin lymphoma (n = 1), carcinoma of the penis (n = 1) and carcinoma of the corpus uteri (n = 1) were retrospectively reviewed. Sixty CT scans with 67 enlarged pelvic nodes were reviewed in order to record the more proximal structures (muscle, bone, vessels, cutis or subcutis and other organs) to each enlarged node or group of nodes according to the four surfaces (anterior, lateral, posterior and medial) in a clockwise direction.

RESULTS

A summary of the observations of each nodal chain and the number of occurrences of every marginal structure on axial CT slices is presented. Finally, simple guidelines are proposed.

CONCLUSIONS

Tumour CTV should be based on individual tumour anatomy-mainly for lateral beams as it results from sagittal T2 weighted MRI images. Boundaries of pelvic nodes CTVs can be derived from observations of enlarged lymph nodes in CT scans.

Association concomitante préopératoire de radiothérapie et de chimiothérapie dans les cancers du col utérin opérables de stades IB2, IIA et IIB proximal de gros volume

PURPOSE

To evaluate preliminary results in terms of toxicity, local tumour control, and survival after preoperative concomitant chemoradiation for operable bulky cervical carcinomas.

PATIENTS AND METHODS

Between December 1991 and October 2001, 42 patients (pts) with bulky cervical carcinomas stage IB2 (11 pts), IIA (15 pts), and IIB (16 pts) with 1/3 proximal parametrial invasion. Median age was 45 years (range: 24-75 years) and clinical median cervical tumour size was 5 cm (range: 4.1-8 cm). A clinical pelvic lymph node involvement has been observed in 10 pts. All patients underwent preoperative external beam pelvic radiation therapy (EBPRT) and concomitant chemotherapy during the first and the fourth radiation weeks combining 5-fluorouracil and cisplatin. The pelvic dose was 40.50 Gy over 4.5 weeks. EBPRT was followed by low-dose-rate uterovaginal brachytherapy with a total dose of 20 Gy in 17 pts. After a rest period of 5-6 weeks, all pts underwent class II modified radical hysterectomy with bilateral lymphadenectomy. Para-aortic lymphadenectomy was performed in eight pts without pathologic para-aortic lymph node involvement. Twenty-one of 25 pts who had not received preoperative uterovaginal brachytherapy underwent postoperative low-dose-rate vaginal brachytherapy of 20 Gy. The median follow-up was 31 months (range: 3-123 months).

RESULTS

Pathologic residual tumour or lymph node involvement was observed in 23 pts. Among the 22 pts with pathologic residual cervical tumour (<0.5 cm: nine pts; >or=0.5 to <or=1 cm: three pts; >1 cm: 10 pts), seven underwent preoperative EBRT followed by uterovaginal brachytherapy vs. 15 treated with preoperative EBRT alone (P = 0.23). Four pts had pathologic lymph node involvement, three pts had vaginal residual tumour, and four pts had pathologic parametrial invasion. The 2- and 5-year overall survival rates were 85% and 74%, respectively. The 2- and 5-year disease-free survival (DFS) rates were 80% and 71%, respectively. After multivariate analysis, the pathologic residual cervical tumour size was the single independent factor decreasing the probability of DFS (P = 0.0054). The 5-year local control rate and metastatic failure rate were 90% and 83.5%, respectively. Haematological effects were moderate. However, six pts had grade 3 acute intestinal toxicity. Four severe late complications requiring surgical intervention were observed (one small bowel complication, three ureteral complications).

CONCLUSION

Primary concomitant chemoradiation followed surgery for bulky operable stage I-II cervical carcinomas can be employed with acceptable toxicity. However, systematic preoperative uterovaginal brachytherapy should increase local tumour control.

Radiation fields in gynecologic oncology: correlation of soft tissue (surgical) to radiologic landmarks

OBJECTIVES

(1). To determine if radiation fields defined by bony structure landmarks correlate to anatomic boundaries of lymph node dissection marked intraoperatively; and (2). to determine if a patient's body mass index (BMI) correlates with these anatomic or radiographic boundaries.

METHODS

One hundred patients undergoing exploratory laparotomy with pelvic and paraaortic lymph node dissection had three medium hemoclips placed at vascular junctions considered of clinical significance to lymph node dissection: insertion of the left ovarian vein into the renal vein, insertion of the right ovarian vein into the vena cava, inferior mesenteric artery (IMA), bifurcation of the aorta, bifurcation of the common iliacs (bilateral), and the insertion of the deep circumflex vein (DCV) in to the external iliac vein (bilateral). Postoperatively, an abdominal X-ray was obtained. Comparisons were made between these eight major vascular landmarks and radiographic bony landmarks that are used to define radiation field boundaries. The percentage of vascular landmarks that were encompassed or fell outside of traditional radiation fields was determined with a 1-cm margin considered an adequate boundary for radiation. These measurements were also compared to patient BMIs.

RESULTS

Radiation fields defined by traditional bony landmarks would adequately encompass the paraaortic lymph nodes in the majority of patients (91%). For pelvic radiation fields, there was a significant "miss" (39%) of common iliac lymph nodes. Approximately one quarter (26%) of patients would receive inadequate coverage of one or both of the lateral boundaries of pelvic radiation. There was no apparent correlation of BMI to vascular or bony landmarks.

CONCLUSIONS

Radiation fields determined by traditional bony landmarks do not adequately reflect the anatomic (surgical) landmarks associated with the lymphatic drainage of the female reproductive organs. Although the majority of tertiary care centers now use advanced imaging techniques (e.g. computed tomography) to plan their radiation treatments, the historical guidelines of radiographic landmarks are still used in smaller institutions and continue to be referenced in Gynecologic Oncology Group protocols. For centers still using radiographic landmarks, the application of hemoclips with X-ray identification is a low-cost modality that is easily reproducible and may be clinically useful in guiding treatment.

Operable Stages IB and II cervical carcinomas: a retrospective study comparing preoperative uterovaginal brachytherapy and postoperative radiotherapy

PURPOSE

To evaluate our data concerning prognostic factors and treatment toxicity in a series of operable cervical carcinomas.

METHODS AND MATERIALS

Between May 1972 and January 1994, 414 patients with cervical carcinoma, staged according to the 1995 FIGO staging system (286 Stage IB1, 38 Stage IB2, 56 Stage IIA, and 34 Stage IIB with 1/3 proximal parametrial involvement), underwent radical hysterectomy with (n = 380) or without (n = 34) bilateral pelvic lymph node dissection (N+: n = 68). Group I included 168 patients who received postoperative radiation therapy (RT): 64 patients had low-dose-rate vaginal brachytherapy with a median total dose (MTD) of 50 Gy; 93 patients had external beam pelvic RT (EBPRT) with an MTD of 45 Gy over 5 weeks, followed by low-dose-rate vaginal brachytherapy (MTD: 20 Gy); and 11 patients had EBPRT alone (MTD: 50 Gy over 6 weeks). Group II included 246 patients treated with preoperative low-dose-rate uterovaginal brachytherapy (MTD: 65 Gy); 32 of these 246 patients also received postoperative EBPRT (MTD: 45 Gy over 5 weeks) delivered to the parametria and pelvic nodes. Mean follow-up from the beginning of treatment was 106 months.

RESULTS

First events included isolated locoregional recurrences (35 patients), isolated distant metastases (27 patients), and locoregional recurrences with synchronous metastases (13 patients). The 10-year disease-free survival (DFS) rate was 88% for Stage IB1, 44% for Stage IB2, 65% for Stage IIA, and 48% for Stage IIB. Multivariate analysis showed that independent factors influencing the probability of DFS were as follows: cervical site (exocervical or endocervical vs. both endo- and exocervical, relative risk [RR]: 1.77, p = 0.047), vascular space invasion (no vs. yes, RR: 1.95, p = 0.041), age (>51 years vs. <or=51 years, RR: 1.90, p = 0.013), 1995 FIGO staging system (IB1 vs. IIA, RR: 2.95, p = 0.004; IB1 vs. IB2, RR: 3.49, p = 0.0009; and IB1 vs. IIB, RR: 4.54, p = 0.00002), and histologic pelvic lymph node involvement (N- vs. N+, RR: 2.94, p = 0.00009). The sequence of adjuvant RT did not influence the probability of DFS (Group I vs. Group II, p = 0.10). In Group II, after univariate analysis, DFS was significantly influenced by histologic residual cervical tumor in the hysterectomy specimen (yes vs. no: 71% vs. 93%, respectively, p < 10(-6)) and by the size of the residual tumor (<or=1 cm vs. >1 cm: 83% vs. 41%, respectively, p = 0.001). The overall postoperative complication rate was 10% in Group I and 9% in Group II (p = 0.7). The rate of postoperative ureteral complications requiring surgical intervention was lower in Group I than in Group II (0.6% vs. 2.3%, respectively, p = 0.03). The overall 10-year rate for Grade 3 and 4 late radiation complications was 10.4%. Postoperative EBPRT significantly increased the 10-year rate for Grade 3 and 4 late radiation complications (yes vs. no: 22% vs. 7%, respectively, p = 0.0002).

CONCLUSION

The prognosis for patients with cervical carcinoma was not influenced by the sequence of adjuvant RT (preoperative uterovaginal brachytherapy vs. postoperative RT) for Stages IB, IIA, and IIB with 1/3 proximal parametrial involvement. However, postoperative EBPRT increased the risk of late radiation complications.

[Operable stage IB and II cancer of the uterine neck: retrospective comparison between preoperative utero-vaginal curietherapy and initial surgery followed by radiotherapy]

PURPOSE

To identify prognostic factors and treatment toxicity in a series of operable stages IB and II cervical carcinomas.

PATIENTS AND METHODS

Between May 1972 and January 1994, 414 patients (pts) with cervical carcinoma staged according to the 1995 FIGO staging system underwent radical hysterectomy with (n = 380) or without (n = 34) bilateral pelvic lymph node dissection. Lateral ovarian transposition to preserve ovarian function was performed on 12 pts. The methods of radiation therapy (RT) were not randomised and depended on the usual practices of the surgical teams. Group I: 168 pts received postoperative RT (64 pts received vaginal brachytherapy alone [mean total dose (MD): 50 Gy], 93 pts had external beam pelvis RT (EBPRT) [MD: 45 Gy over 5 weeks] followed by vaginal brachytherapy [MD: 20 Gy], and 11 pts had EBPRT alone [MD: 50 Gy over 6 weeks]. Group II: 246 pts received preoperative utero-vaginal brachytherapy [MD: 65 Gy], and 32 of theses 246 pts also received postoperative EBPRT [MD: 45 Gy over 5 weeks] delivered to the parametric and the pelvic lymph nodes with a midline pelvic shield. The mean follow-up was 106 months.

RESULTS

The 10-year disease-free survival (DFS) rate was 80%. From 75 recurrences, 35 were isolated locoregional. Multivariate analysis showed that independent factors decreasing the probability of DFS were: both exo and endocervical tumour site (p = 0.047), lymph-vascular space invasion (p = 0.041), age < or = 51 yr (p = 0.013), 1995 FIGO staging system (stage IB1 vs stage IIA, p = 0.004, stage IB1 vs stage IB2, p = 0.0009, and stage IB1 vs stage IIB with 1/3 proximal parametrical infiltration, p = 0.00002), and histological pelvic involved lymph nodes (p = 0.00009). Methods of adjuvant RT did not influence the probability of DFS (group I vs group II, p = 0.10). The postoperative complication rate was 10.2% in group I and 8.9% in group II (p = 0.7) but the postoperative urethral complication rate necessitating surgical intervention with reimplantation was lower in group I than in group II (0.6% vs 2.3%, respectively, p = 0.03). The 10-year rate for grade 3 and 4 late radiation complications according to the LENT-SOMA scoring system was 10.4%. EPRT significantly increased the 10-year rate for grade 3 and 4 late radiation complications (yes vs no: 22% vs 7%, respectively, p = 0.0002).

CONCLUSION

In our series, the methods of adjuvant RT (primary surgery vs preoperative uterovaginal brachytherapy) do not seem to influence the prognosis of the stage IB, IIA, and IIB (with 1/3 proximal parametrical involvement only) cervical carcinomas. The postoperative EPRT applied according to histopathological risk factors after surgical treatment increases the risk of late radiation complications.

[Epidermoid carcinoma of the uterine cervix at operable bulky stages IB and II treated with combined primary radiation therapy and surgery]

PURPOSE

To identify prognostic factors and treatment toxicity in a series of operable bulky stages I and II cervical carcinomas treated with a therapeutic modality combining primary irradiation and surgery.

PATIENTS AND METHODS

Between July 1982 and May 1996, 66 patients with bulky squamous-cell cervical carcinomas (stage IB2, IIA, and IIB with 1/3 proximal parametrial invasion) underwent primary external beam pelvic radiation therapy (37.40 Gy to 40 Gy over 4.5 weeks) and low-dose-rate uterovaginal brachytherapy (20 Gy) followed, 5 to 6 weeks later, by class II modified radical hysterectomy with bilateral pelvic lymphadenectomy. The four last patients received concomitant chemotherapy during the first and the fourth radiation week combining 5-FU and cisplatin. A clinical pelvic lymph node involvement had been observed in 7 patients. The clinical median tumor size was 5 cm in diameter (range: 4.5-8 cm). The median follow-up was 97 months.

RESULTS

Pathologic complete tumor response in specimen of hysterectomy were observed in 46 patients. Six patients had pathologic unilateral iliac lymph node involvement. The 5- and 10-year specific survival rates were 79 and 74%, respectively. The 5- and 10-year disease-free survival rates were 76% and 71%, respectively. The 10-year local control rate was 85%. The 10-year probability for pelvic recurrence was significantly influenced by the pathologic tumor response: 26% in the residual group vs 5% in the complete tumor response group, P = 0.024). After multivariate analysis, the independent factors decreasing the probability of disease-free survival were: pathologic pelvic lymph node involvement (P = 0.029), and parametrial invasion (P = 0.031). Five late severe complications requiring surgical intervention were observed: 2 bowel obstructions, 1 ureteral stenosis, 1 vesicovaginal fistula, and 1 radiation induced unilateral femoral necrosis.

CONCLUSION

A good local control is obtained after combined primary radiation therapy and surgery for bulky stages I and II cervical carcinomas. In our more recent practice, the treatment combines primary concomitant chemoradiation followed by surgery including pelvic and para-aortic lymphadenectomy.

The impact of patient positioning on the adequate coverage of the uterus in the primary irradiation of cervical carcinoma: a prospective analysis using magnetic resonance imaging

BACKGROUND AND PURPOSE

The intention of this prospective study is to assess the influence of different patient positionings and the use of belly boards on the coverage of the uterus by standard radiation fields.

MATERIAL AND METHODS

In 21 women with carcinoma of the uterine cervix magnetic resonance imaging (MRI) scans in prone patient position with and without belly board and computed tomography (CT) scans in supine position were analysed after superimposing standard pelvic box fields. Further, all patients underwent a second MRI field control in prone position with belly board to detect intraindividual variations in the uterus position during treatment.

RESULTS

Standard portals did not completely cover the uterus in supine position in 7/21 (33%), in prone position with belly board in 7/21 (33%) and without belly board in 5/21 (24%). Insufficient uterine coverage was found only in the anteroposterior direction. The mean distance (+/- standard deviation) between the field borders of the lateral portals and the uterus was in supine position anteriorly 3.4 cm (+/-2.2 cm) and posteriorly 1.8 cm (+/-1.3 cm), in prone position with belly board anteriorly 2.2 cm (+/-2.7 cm) and posteriorly 2.6 cm (+/-1.6 cm), prone without belly board anteriorly 3.3 cm (+/-2.4 cm) and posteriorly 1.9 cm (+/-1.1 cm). The difference was statistically significant between supine and prone position with belly board and between prone position with and without belly board. Repeated MRI controls during therapy showed no significant changes compared to the MRIs at the beginning of therapy.

CONCLUSIONS

The use of standard radiation fields results in a high percentage of geographical misfits. Three-dimensional treatment planning is a prerequisite for adequate uterus coverage.

[Gross tumor volume and clinical target volume in radiotherapy: tumors of the corpus uteri]

Surgery is the major treatment of the tumours of the corpus uteri. The imaging workup is essentially used to detect locally advanced lesions which are not suitable for surgery, because the preoperative knowledge of prognostic factors seldom influences treatment strategy in the early stages. The 3D planning of external irradiation for corpus uteri tumours is not very widespread, despite its real impact in preoperative irradiation strategy or irradiation alone. In postoperative strategy its importance is less evident; however, CT planning leads to a better knowledge of the dose distribution to the critical organs, which will probably contribute to a better control of late complications.

[Radiotherapy for tumors of the uterine cervix. Gross tumor volume and clinical target volume]

Treatment of carcinoma of the uterine cervix needs a multidisciplinary approach. External irradiation and brachytherapy are highly curative because of the tumor radiosensitivity. The main prognostic factors are tumoral volume and nodal involvement. Tumoral extent is evaluated by diagnostic MR imaging, and gynecological exam. Nodal involvement can be assessed, accurately by coelioscopic pelvic node sampling and by imaging modalities such as CT scan. The knowledge of these two factors helps to choose the treatment strategy. The use of imaging (MRI and CT) added to clinical findings allows to design external irradiation fields. 3D treatment planning in external irradiation and brachytherapy is based upon the use of imaging (CT and MRI). It leads to a better knowledge of dose distribution to the target and critical organs and allows more individualized and conformal treatment.

The use of a permanent magnetic resonance imaging system for radiotherapy treatment planning of bone metastases

PURPOSE

To evaluate the usefulness of magnetic resonance (MR) imaging-based radiotherapy treatment planning (RTTP) for bone metastases in clinical applications.

METHODS AND MATERIALS

MR imaging-based RTTP was carried out for 28 patients with bone metastases using a permanent magnetic MR unit. Twenty-three patients received MR imaging-assisted X-ray simulation, and five underwent MR simulation. In MR imaging-assisted X-ray simulation, the radiation fields defined by an X-ray simulator were modified based on MR information scanned in the exact treatment position using MR skin markers. In MR simulation, both isocenter position and field size were determined on MR images and projected onto the patient's skin.

RESULTS

All lesions unclear on other imaging modalities could be clearly identified on MR imaging. Of the 23 patients receiving MR imaging-assisted X-ray simulation, modification of the original radiation field was necessary in 14 patients (extended in 9, reduced in 4, and completely changed in 1). In MR simulation, appropriate radiation fields could be easily and quickly determined using MR imaging.

CONCLUSION

Methods for MR imaging-based RTTP were developed and clinically implemented for patients with bone metastases, and they were shown to be useful for improving the accuracy of the tumor location. They would provide better therapeutic/palliative benefit to particular patients with bone metastases and could also be applied to other lesions in the future.

Reproducibility of geometric distortion in magnetic resonance imaging based on phantom studies

BACKGROUND AND PURPOSE

Image distortion is one of the major drawbacks of magnetic resonance (MR) imaging for use in radiotherapy treatment planning (RTTP). In this study, the reproducibility of MR imaging distortion was evaluated by repeated phantom measurements.

MATERIALS AND METHODS

A grid-pattern acrylic phantom was scanned with a 0.2-Tesla permanent magnetic unit. We repeated a series of scans three times to evaluate the reproducibility of the distortion. In each series, co-ordinates at 432 intersections of the grid were measured for both T1- and T2-weighted spin-echo (SE) pulse sequences. Positional displacements and their variations at the intersections were calculated.

RESULTS

Averages of the displacements were distributed between 1.58 and 1.74 mm, and maximum values (MAX) between 12.6 and 15.0 mm. Within 120 mm of the image center, the average values ranged from 0.73 to 0.80 mm, and from 3.4 to 5.0 mm for MAX. The absolute values of the positional variations among three series were distributed between 0.41 and 0.88 mm for average values, and between 1.4 and 4.5 mm for MAX.

CONCLUSIONS

The positional variations were mostly within 3 pixels, and most of the positional displacements within the radius of 120 mm of the image center were 2 mm or less. Therefore, it will be possible to use this MR system in RTTP under limited situations, although careful applications are required for RTTP of the body. The development of a computer program to correct image distortion is expected.

[Contribution of imaging in radiotherapy planning in uterine cervix cancers]

External irradiation and brachytherapy are curative in the treatment of carcinoma of the cervix. The aim of radiotherapy is to optimize the irradiation of the target volume and to reduce the dose to critical organs. The use of imaging (computed tomography and magnetic resonance imaging added to clinical findings and standard guidelines) are studied in the treatment planning of external irradiation and brachytherapy in carcinoma of the cervix. Imaging allows an individualized and conformal treatment planning.

The benefit of Beam's eye view based 3D treatment planning for cervical cancer

PURPOSE

The aim of this study was to evaluate the possibility of Beam's eye view (BEV) based three dimensional (3D) treatment planning, to reduce portions of organs at risk included in the treated volume without increasing the risk of geographical miss in external beam therapy of cervical cancer.

MATERIALS AND METHODS

Three dimensional dose distribution of BEV based 3D treatment plans was compared to the 3D dose distribution derived from a four-field-box-technique using standard portals. A total of 20 patients with cervical cancer stage FIGO IIB and FIGO IIIB was included. Dose distribution in the target volumes and in the organs at risk of BEV based treatment planning, was compared to the dose distribution of the standard field technique using dose-volume-histograms.

RESULTS

In 4/20 patients (20%) a geographical miss at the cervix uteri was observed for the standard field technique. The BEV based treatment planning resulted in an adequate coverage of target volume and additionally in a reduction of portions of bladder and bowel volume included in the treated volume (-13.5, -10%). In contrast the BEV based technique resulted in an increase of portions of the rectum volume included in the treated volume compared to standard portals due to a shift of the rectum by the enlarged cervix uteri from its posterior to a lateral position. An overall 7% reduction of treated volume was observed, although the maximum width of lateral fields increased for the BEV technique. Moreover, we have found a remarkable impact of bladder fillings on the amount of bowel and bladder volume included in the treated volume.

CONCLUSION

BEV based 3D treatment planning for external beam therapy of cervical cancer offers a possibility to avoid geographical miss of part of the CTV with reduced portions of bladder and bowel volume included in the treated volume.

[A comparison of CT-supported 3D planning with simulator planning in the pelvic irradiation of primary cervical carcinoma]

BACKGROUND

Using standardized simulator planning guided by bony landmarks for pelvic irradiation of primary cervical carcinoma with some patients a geographical miss regarding tumor or potential tumor spread can happen because of insufficient knowledge of the individual anatomical situation. The question arises whether for patients with this indication the higher effort in terms of time and personnel for 3D treatment planning is justified.

PATIENTS AND METHOD

In a prospective study on 20 subsequent patients with primary cervical carcinoma in Stages I to III simulator planning of a 4-field box-technique was performed. After defining the planning target volume (PTV) in the 3D planning system the field configuration of the simulator planning was transmitted. The resulting plan was compared to a second one based on the defined PTV and evaluated regarding a possible geographical miss and encompassment of the PTV by the treated volume (ICRU). Volumes of open and shaped portals were calculated for both techniques.

RESULTS

Planning by simulation resulted in 1 geographical miss and in 10 more cases the encompassment of the PTV by the treated volume was inadequate. For a PTV of mean 1,729 cm3 the mean volume defined by simulation was 3,120 cm3 for the open portals and 2,702 cm3 for the shaped portals (Figure 1). The volume reduction by blocks was 13.4% (mean). With CT-based 3D treatment planning the volume of the open portals was 3.3% (mean) enlarged to 3,224 cm3 (Figure 2). The resulting mean volume of the shaped portals was 2,458 ccm. The reduction compared to the open portals was 23.8% (mean). The treated volumes were 244 cm3 or 9% (mean) smaller compared to simulator planning. The "treated volume/planning target volume ratio" was decreased from 1.59 to 1.42.

CONCLUSION

The introduction of 3D treatment planning for pelvic irradiation of cervical carcinoma is to be recommended for reasons of quality assurance. Reduction of the treated volume is possible but further research has to be done to determine whether the rate of complications can be decreased as well.

Defining the superior border of posterior fossa radiation treatment fields

PURPOSE

Lateral posterior fossa treatment fields are usually defined on traditional simulation films based on bony landmarks. The superior field border, intended to include the apex of the tentorium cerebelli, is frequently difficult to define. While sagittal magnetic resonance imaging (MRI) images or three-dimensional treatment planning tools are good means to locate the tentorial apex, these are not always available. We herein describe a method for locating the tentorial apex based on bony landmarks.

METHODS AND MATERIALS

Midsagittal magnetic resonance images of 53 patients were reviewed. Using a Cartesian grid, the geometric relationship between the tentorial apex and several bony landmarks was assessed. Two lines were defined: the first connected the posterior clinoid and the internal occipital protuberance (AB). The second was perpendicular to the first, included the tentorial apex, and extended from the base of the skull inferiorly to the "crown" of the skull superiorly (DE). Relationships between measurements were made using linear regression and least square fits.

RESULTS

Line DE was within 5 mm of the perpendicular bisector of line AB in 83% (44/53) of patients. The tentorial apex was located within 10 mm of the midpoint of DE in 91% (48/53) of patients.

CONCLUSION

In the majority of patients, the location of the tentorial apex can be estimated based on bony landmarks, to within approximately 10 mm. The technique described is a useful means of estimating the location of the tentorial apex in patients where sagittal MRI imaging or three-dimensional treatment planning tools are not available.

[Practice of virtual simulation at the Saint-André hospital]

PURPOSE

Prospective evaluation of a virtual simulation technique.

PATIENTS AND METHODS

From September 1993 to February 1997, 343 patients underwent radiation therapy using this technique. Treated sites were mostly: brain (132), rectum (59), lung (43), and prostate (28). A CT-scan was performed on a patient in treatment position. Twenty-five to 70 jointive slices widely encompassed the treated volume. The target volume (CTV according to ICRU 50) and often critical organs were controured, slice by slice, by the radiation oncologist. Beams covering the CTV plus a security margin (PTV) were placed on the "virtual patient". Digital radiographs were reconstructed (DRR) as simulator radiographs for each field. Thus, the good coverage of PTV was assessed. Fields and beam arrangements were further optimized. Definitive isocenter was then placed using a classical simulator. Perfect matching of DRR and actual simulator radiographs had to be obtained.

RESULTS

Nineteen patients presented grade 3, and 1 grade 4 acute radiation effects. With a median follow-up of 18 months, five patients suffered from grade 3, and one from grade 4 complications. Fifty-five patients had tumor recurrence in the treated volume, and 19 had marginal relapse.

CONCLUSION

In our department, virtual simulation has become a routine technique of treatment planning for deep-seated tumors. This technique remains time-consuming for radiation oncologists: about 2 hours. But it stimulates reflexion on anatomy, tumor extension pathways, target volumes; and is becoming an excellent pedagogical tool.