[Radiotherapy of carcinomas of the anal canal. Tenon Hospital experience]

Since 1980, curative-intent radiation therapy of epidermoid carcinoma of the anal canal is the standard first line treatment. The combined concomitant chemotherapy and radiation therapy is presently established for locally advanced tumors more than 4 cm in length and/or with nodal involvement. We report the Tenon hospital experience since 1972 concerning the long term results after radiation therapy, the modifications of the radiation technique, and the evolution of treatment strategy.

[Epidermoid carcinomas of the anal canal treated with definitive radiation therapy in a series of 305 patients]

PURPOSE

To identify prognostic factors and treatment toxicity in a serie of epidermoid cancers of the anal canal without evident metastasis.

PATIENTS AND METHODS

Between June 1972 and January 1997, 305 patients (pts) were treated with curative-intent radiation therapy (RT). The T-stages according to the 1987 UICC classification were: 26 T1, 141 T2, 104 T3, and 34 T4. There were 49 pts with nodal involvement at presentation. Pretreatment anal function scoring according to our in-house system was: 22 scored 0, 182 scored 1, 74 scored 2, 7 scored 3, 11 scored 4, and 9 not available pts. The treatment started with external beam RT (EBRT) in 303 pts (median dose: 45 Gy). After a rest period of 4 to 6 weeks, a boost of 20 Gy was delivered by EBRT in 279 pts and by interstitial 192Ir brachytherapy (Bcy) in 17 pts. Seven pts received only one course of EBRT (mean dose: 49.5 Gy) and 2 pts were treated with interstitial 192Ir Bcy alone (55 and 60 Gy, respectively). Concomitant chemotherapy (5-fluoro-uracil and either mitomycin C or cisplatin) was delivered to 19 pts. Mean follow-up was 103 months.

RESULTS

At the end of RT local tumor clinical complete response (cCR) rate was 80%. Out of 61 non responders or local progressive tumors 27 (44%) were salvaged with abdominoperineal resection (APR). The rate of local tumor relapse (LR) was 12%. Out of 37 LTR, 20 (54%) were salvaged with APR and one with interstitial 192Ir Bcy. The orevall local tumor control (LC) rate with or without salvage local treatment was 84%. LC rate with a good anal function scoring (score 0 and 1) was 56.5%. Among 181/186 available pts who preserved their anus, 94% had a good anal function scoring. For a subgroup of 15 pts with length tumor <2 cm-N0, the LC rate after the end of RT was 100%, the LC rate with or without local salvage treatment was 100%, and among 13 available pts who preserved their anus, the anal function scoring was good in 12 pts (92%). The 10-years disease-free survival was 74%. After multivariate analysis, 3 independent predicting factors significantly influenced the disease-free survival: gap duration between 2 courses of RT (>38 days vs < or =38 days, P =0.0025), pretreatment anal function scoring (0 vs 1 vs 2 vs 3 vs 4, P =4.4 10(-6)), and cCR after the end of RT (no complete response vs complete response, P =2.5 10(-14)).

CONCLUSION

We confirm excellent results with RT in T1 and T2 lesions. However, chemoradiotherapy should be prefered to improve survival free of colostomy with a good anal sphincter function for tumors more than or equal to 2 cm in length and locally advanced tumors.

Combination of photon and proton radiation therapy for chordomas and chondrosarcomas of the skull base: the Centre de Protonthérapie D'Orsay experience

PURPOSE

Prospective analysis of local tumor control, survival, and treatment complications in 44 consecutive patients treated with fractionated photon and proton radiation for a chordoma or chondrosarcoma of the skull base.

METHODS AND MATERIALS

Between December 1995 and December 1998, 45 patients with a median age of 55 years (14-85) were treated using a 201-MeV proton beam at the Centre de Protonthérapie d'Orsay, 34 for a chordoma and 11 for a chondrosarcoma. Irradiation combined high-energy photons and protons. Photons represented two-thirds of the total dose and protons one-third. The median total dose delivered within the gross tumor volume was 67 cobalt Gray equivalent (CGE) (range: 60-70).

RESULTS

With a mean follow-up of 30.5 months (range: 2-56), the 3-year local control rates for chordomas and chondrosarcomas were 83.1% and 90%, respectively, and 3-year overall survival rates were 91% and 90%, respectively. Eight patients (18%) failed locally (7 within the clinical tumor volume and 1 unknown). Four patients died of tumor and 2 others of intercurrent disease. In univariate analysis, young age at time of radiotherapy influenced local control positively (p < 0.03), but not in multivariate analysis. Only 2 patients presented Grade 3 or 4 complications.

CONCLUSION

In skull-base chordomas and chondrosarcomas, the combination of photons with a proton boost of one-third the total dose offers an excellent chance of cure at the price of an acceptable toxicity. These results should be confirmed with a longer follow-up.

[Endometrial adenocarcinoma treated with combined radiotherapy and surgery: 437 cases]

PURPOSE

To identify prognostic factors and treatment toxicity in a series of operable endometrial adenocarcinomas.

PATIENTS AND METHODS

Between November 1971 and October 1992, 437 patients (pts) with endometrial carcinoma, staged according to the 1988 FIGO staging system, underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy without (n = 140) or with (n = 297) pelvic lymph node dissection. The chronology of RT was not randomized and depended on the usual practices of the surgical teams. Group I: 79 pts received preoperative uterovaginal brachytherapy (mean total dose [MD]: 57 Gy). Group II: 358 pts received postoperative RT (196 pts received vaginal brachytherapy alone [MD: 50 Gy], 158 pts had external beam pelvis RT [EPRT] [MD: 46 Gy over 5 weeks] followed by vaginal brachytherapy [MD: 17 Gy], and 4 pts had EPRT alone [MD: 46 Gy over 5 weeks]). The mean follow-up was 128 months.

RESULTS

The 10-year disease-free survival rate was 86%. From 57 recurrences, 12 were isolated locoregionally. Multivariate analysis showed that independent factors decreasing the probability of disease-free survival were: histologic type (clear cell carcinoma, p = 0.038), largest histologic tumor diameter > 3 cm (p = 0.015), histologic grade (p = 0.008), myometrial invasion > 1/2 (p = 0.0055), and 1988 FIGO staging system (p = 9.10(-8)). In group II, the addition of EPRT did not seem to improve locoregional control. The postoperative complication rate was 7%. The independent factors increasing the risk of postoperative complications were FIGO stage (p = 0.02) and pelvic lymph node dissection (p = 0.011). The 10-year rate for grade 3 and 4 late radiation complications according to the LENT-SOMA scoring system was 3.1%. EPRT independently increased the 10-year rate for grade 3 and 4 late radiation complications (R.R.: 5.6, p = 0.0096).

CONCLUSION

EPRT increases the risk of late radiation complications. After surgical and histopathologic staging with pelvic lymph node dissection, in a subgroup of intermediate risk patients (stage IA grade 3, IB-C and II), postoperative vaginal brachytherapy alone is probably sufficient to obtain a good therapeutic index. Results for patients with stage III tumor are not satisfactory.

[Second treatment of cAVMs after radiosurgery]

Risks of bleeding from partially or unobliterated cerebral arteriovenous malformations remain unchanged. A complementary treatment should be indicated after radiosurgery. In this brief review the following data are discussed: the reasons of second treatment, imaging follow-up of cerebral arteriovenous malformations after radiosurgery, types of cerebral arteriovenous malformations to be treated, timing and therapeutic modalities.

[Radiosurgery of cerebral arteriovenous malformations: methodology of the dose prescription and its implications for dosimetric results. Retrospective study of 408 cases]

PURPOSE

To study dosimetric implications of our group dose prescription methodology on a series of 408 cerebral arteriovenous malformations.

MATERIAL

and method. Between January 1990 and July 1998, 408 patients with cerebral arteriovenous malformations that had never been irradiated before, were treated radiosurgically in a single fraction at Tenon Hospital. 223 patients were treated with a single isocentre and 185 with multiple isocenters. Dosimetric characteristics have been studied as a function of the global quality index of planning, defined our group as the standard deviation of the differential dose volume histogram calculated in the lesion.

RESULTS

One percent correlation obtained between some dosimetric data and the global quality index of planning allowed to modelize by linear equations the connection between this quality index and minimum isodose in the lesion, mean doses and isodoses in the underdosed part of the lesion and in the complete lesion. This was done for mono isocentric cases and multi isocentric cases.

CONCLUSION

Before the choice of the therapeutic dose and prescription isodose, it is therefore possible from the global quality index of planning to foresee isodoses modelized by the defined equations. So, the radiotherapist can compensate using the prescription since conformity is not perfect and thus attenuate healthy tissues overdosage.

[Technique of Linac radiosurgery for cerebral arteriovenous malformations]

BACKGROUND AND PURPOSE

Description of the irradiation technique used by our group since 1986 for radiosurgery of cerebral arteriovenous malformations using Xrays minibeams from a linear accelerator. Method. The technique was elaborated by O. Betti in the early 80. He used several coronal arcs to irradiate the center of the target with X rays circular minibeams. Their diameter (6 to 20 mm) is chosen according to the size of the nidus. The patient is seated in a specially built armchair. His head is immobilized with the Talairach frame afixed in the calvarium by 4 special screws: they allow to remove the frame after stereotactic angiography and/or CTscan and to replace it to perform the stereotactic irradiation. The frame and the head rotate around an horizontal axis passing by the linac isocenter ie the center of the target volume. The combination of both movements: rotation of the Linac and rotation of the stereotactic frame covers a spherical sector representing the surface of portals of entry of the minibeams. The frame can slide on a plate allowing access to the entire brain. Results. The special seat and the frame are movable on curved rails allowing to avoid or reduce irradiation of the body of the patient.

CONCLUSION

We have been using this system of irradiation in the seated position since 1986 to treat more than 900 patients.

Adenocarcinoma of the endometrium treated with combined irradiation and surgery: study of 437 patients

PURPOSE

To identify prognostic factors and treatment toxicity in a series of operable endometrial adenocarcinomas.

METHODS AND MATERIALS

Between November 1971 and October 1992, 437 patients (pts) with endometrial carcinoma, staged according to the 1988 FIGO staging system (225 Stage IB, 107 Stage IC, 4 Stage IIA, 35 Stage IIB, 30 Stage IIIA, 6 Stage IIIB, and 30 Stage IIIC), underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy without (n = 140) or with (n = 297) pelvic lymph node dissection. The chronology of adjuvant RT was not randomized and depended on the usual practices of the surgical teams. Seventy-nine pts (Group I) received preoperative low-dose-rate uterovaginal brachytherapy (mean dose [MD]: 57 Gy). Three hundred fifty-eight pts (Group II) received postoperative RT. One hundred ninety-six pts received low-dose-rate vaginal brachytherapy alone (MD: 50 Gy). One hundred fifty-eight pts had external beam pelvic RT (MD: 46 Gy) followed by low-dose-rate vaginal brachytherapy (MD: 17 Gy). Four pts had external beam pelvic RT alone (MD: 47 Gy). The mean follow-up from the beginning of treatment was 128 months.

RESULTS

The 10-year disease-free survival rate was 86%. From 57 recurrences, only 12 were isolated locoregional recurrences. The independent factors decreasing the probability of disease-free survival were as follows: histologic type (clear-cell carcinoma, p = 0.038), largest histologic tumor diameter >3 cm (p = 0.015), histologic grade (p = 0.008), myometrial invasion > 1/2 (p = 0.005), and 1988 FIGO staging system (p = 9.10(-8)). In Group II, the addition of external beam pelvic RT did not seem to independently improve vaginal or pelvic control. The postoperative complication rate was 7%. The independent factors increasing the risk of postoperative complications were stage FIGO (p = 0.02) and pelvic lymph node dissection (p = 0.011). The 10-year rate for Grade 3 and 4 late radiation complications according to the LENT-SOMA scoring system was 3.1%. External beam pelvic RT independently increased the rate for Grade 3 and 4 late complication (RR: 5.6, p = 0.0096).

CONCLUSION

Postoperative external beam pelvic RT increases the risk of late radiation complications. After surgical and histopathologic staging with pelvic lymph node dissection, in subgroup of "intermediate-risk" patients (Stage IA Grade 3, IB-C and II), postoperative vaginal brachytherapy alone is probably sufficient to obtain a good therapeutic index. Results for patients with Stage III tumor are not satisfactory.

[Radiotherapeutic basis of radiosurgery as applied to cerebral arteriovenous malformations: dose-volume effects]

BACKGROUND AND PURPOSE

To attempt to analyze the basic effects of radiosurgery as applied to cerebral arteriovenous malformations.

METHODS

We reviewed and discussed the previous issues of the international literature concerning radiobiological principles of radiosurgery of arteriovenous malformations.

RESULTS

The irradiated volume contained both a target volume consisting of abnormal vessels of the nidus often embedded within connective tissue stroma and the surrounding normal brain tissue. These were late-responding tissues after the radiation and sensitive tissues to high dose per fraction. There was not resistant hypoxic cell that could be killed efficiently with fractionated treatment. The therapeutic ratio between damage in the arteriovenous malformation nidus and late complications in the surrounding tissues was independent of fractionation. Furthermore, sterilization of all clonogenic cells in the target volume was not necessary to obtain complete obliteration of arteriovenous malformation. Consequently, there was nothing to be gained by a fractionated course relative to a stereotactic high single-dose irradiation for a small targeted volume (<=25 mm in diameter or<=4 200 mm(3)). The minimum target dose (Dmin) seemed to be the dosimetric independent predicting factor for complete obliteration. The Dmin-response relationship suggested a threshold dose of 5 Gy to 10 Gy and the better effects following Dmin from 20 Gy to 25 Gy. A Dmin above 25 Gy significantly increased the risk of serious late complications. The treated volume seemed to be the significant independent predicting dosimetric factor for developing persistent symptomatic sequelae. The optimum dose to deliver to obtain complete obliteration of an arteriovenous malformation was selected by balancing the expected obliteration rate for each dose with the corresponding risks from radiosurgery depending on size, location, shape and dose distribution.

CONCLUSION

Although the basic pathological process is still uncertain there is a strong rationale for stereotactic radiotherapy delivered in a high single-dose for small arteriovenous malformations.

[Radiosurgery of choroidal and cisternal cerebral arteriovenous malformations]

PURPOSE

Cerebral arteriovenous malformations surrounded by cerebrospinal fluid seemed to exhibit worse response to radiosurgery than others. We searched to verify if this is was true and to find causes.

MATERIAL

and methods. From our series of 705 patients with cerebral arteriovenous malformations treated by radiosurgery, 3,8% (27/705) had choroidal or cisternal arteriovenous malformations. Revelation mode was hemorrhage in 86% of cases but sometimes headaches occurred before hemorrhage; thus overall hemorrhage rate was 96%. Mean age of revelation was 24. Mean size was 20 mm, mean volume was 4 cc. Spetzler & Martin's grades were 35% in grade II, 43% in grade III and 22% in grade IV. Location was ventricular in 63% of cases and cisternal in 37%. Mean dose at reference isodose was 24 Gy with a higher rate of monoisocenters. We looked for differences between this population of arteriovenous malformations and the rest of the series for patients, treatments prior radiosurgery, cerebral arteriovenous malformations's characteristics, dosimetric parameters and complications. Statistical analysis was done with a Pearson chi2 test and Spearman non parametric correlation test.

RESULTS

Obiteration rate was 47.6% with a mean delay of 26 months. Differential characteristics of choroidal or cisternal arteriovenous malformations were: younger age of revelation, higher frequency of hemorrhage, of intra or paranidal aneurysms, of deep unique drainage, a higher Spetzler grade and a smaller rate of complete recovering. Mortality and clinical morbidity due to radiosurgery were 0%. Actuarial rate of hemorrhage after radiosurgery was 4,34% per year and per patient or per hemorrhage. This rate was higher than in the global series. Parenchymal changes seen on MRI were less frequent (26,6%) and less serious (no grade 4 radionecrosis-like parenchymal changes).

CONCLUSION

Choroidal or cisternal arteriovenous malformations seem to respond less to radiosurgery than others. One potential explanation is the higher frequency of multiafferences of these arteriovenous malformations with anastomoses of anterior and posterior choroidal arteries. However, radiosurgery still stay a treatment of choice for these arteriovenous malformations with little adaptations of the irradiation strategy.

[Radiosurgery of cerebral arteriovenous malformations in children]

BACKGROUND AND PURPOSE

Radiosurgery has been used in a few cases of cerebral arteriovenous malformations in children. From data of our series and from literature, we tried to determine the place of this therapeutic modality for treatment of pediatric cAVMs.

PATIENTS AND METHOD

From the whole series of 705 patients treated by radiosurgery between January 84 and December 1998, 55 were under 15 years of age. Revelation mode was hemorrhage (70.9%), seizures (12.7%), headaches (10.9%) and neurological progressive deficits (1.8%). Size ranged from 5 to 50 mm (mean: 22 mm) and volume ranged from 1 to 16 cc (mean: 4 cc). Treatments prior radiosurgery were embolization alone (28%), surgery alone (16.7%), embolization plus surgery (5.5%). Distribution of cerebral arteriovenous malformations according to Spetzler & Martin's grading were 10% in grade I, 35% in grade II, 40% in grade III, 15% in grade IV and 0% in grade V.

RESULTS

Overall obliteration rate was 59% with an exaustibility rate of 80%. Obliteration rate was dependent on size and volume (100% for<1 cc cerebral arteriovenous malformations sized, 73% from 1-4 cc, 40% from 4-10 cc and 100% (but n=1)>10 cc; p=0.019), sex (84.2% for boys and 40% for girls), of angioarchitecture and Dmin (p=0.01). After multivariate analysis, only Dmin was nearly correlated with the obliteration rate (b=0.462 7; SE=0.244 0; p=0.057). Actuarial risk of hemorrhage was 2.12% per year per patient. Patients with seizures were seizure-free without any drugs after radiosurgery in 80% of cases. Parenchymal changes were mainly hypersignals spT2 in MRI.

CONCLUSION

Radiosurgery seems to be an efficient treatment with a low morbidity for cerebral arteriovenous malformations in children.

[Parenchymal changes after radiosurgery of cerebral arteriovenous malformations. Clinical and MRI data]

BACKGROUND AND PURPOSE

Purposes of this study are to describe different parenchymal changes seen after radiosurgery of cerebral arteriovenous malformations and the clinical symptoms which can be associated, and risk factors correlated with them.

PATIENTS

and method. From the whole population of 705 patients with a cerebral arteriovenous malformations treated by radiosurgery between 1984 and 1998, clinical from 615 patients and post radiosurgery MRI data from 367 patients were reviewed. Neurological deficit occurred in 5.37% of cases and was still persistant in 1.46% of cases. Delay of occurrence of deficits ranged from 6 to 83 months (mean: 27 months, median: 15 months). Parenchymal changes seen in MRI were classified in 4 grades: 1 without parenchymal changes, 2 hypersignal in sp T2, 3=2 with homogenous enhancement with gadolinium, 4 with hyposignal in spT1 and annular irregular enhancement. Several parameters (size, volume, angioarchitecture of the cerebral arteriovenous malformation, dosimetric parameters) were studied and correlations were searched by uni and multivariate analysis with occurrence and delay of occurrence of deficits or parenchymal changes.

RESULTS

In multivariate analysis, only size was significantly correlated with occurrence of parenchymal changes (p=0.0016); only size of the malformation was significantly correlated with delay of occurrence of parenchymal changes (p=0.0082); only grade 4 was correlated with occurrence of neurological deficit (p<0.00001). However, when only "a priori" parameters (known before radiosurgery) are introducted in logistic model, size taille (p=0.02) and hypoplasy of a sinus (p=0.0049) are significantly correlated with occurrence of neurological deficit. Only parenchymal changes grade 4 was significantly correlated with delay of occurrence of a neurological deficit (p<0.00001). However, when only a priori parameters (known before radiosurgery) are introducted in logistic model, only arterial steal (p=0.054) was significantly correlated with delay of occurrence of a neurological deficit.

CONCLUSION

Parenchymal changes are various in expression, signification and clinical symptoms associated with them. They must be known and recognized for better prevention and symptomatic treatment as well.

[Importance of quantitative evaluation in the planning of the stereotactic irradiation of complex cAVMs]

BACKGROUND AND PURPOSE

The purpose was to present the successive steps of dosimetric planning and the different means used to allow the choice of the best solution among several planning projects considering the anatomical and clinical features of arteriovenous malformation. Method. Four successive steps were: A study of these factors for 5 different plannings of a clinical case using different isocenters is presented and the results are discussed.

CONCLUSION

For complex arteriovenous malformations several hours are often necessary to permit physicians/radiotherapists to elaborate planning which is often a compromise among several solutions.

[Technologic developments in radiotherapy and stereotactic radiosurgery]

We present a review of current technological progress enabling improvement in the quality of stereotactic irradiations: imaging fusion; individual adaptation of dosimetric planning to the shape of the target thanks to several collimation systems, spatial modulation of the beam with the use of multileaf microcollimators, beam intensity modulation, robotisation of the materials, owing to hardware and software developments.

[Radiosurgery for large cerebral arteriovenous malformations]

BACKGROUND AND PURPOSE

Treatment of large cerebral arteriovenous malformations is a challenge for embolization, surgery and radiosurgery too. The purposes of this study is to review results of RS for these large cerebral arteriovenous malformations and to study recent methods which can allow to improve results.

PATIENTS

and method. From our series, 112 patients had cerebral arteriovenous malformations higher than 30 mm or 10 cc at time of the radiosurgery. Revelation mode was hemorrhage in 47%, seizures in 42%, headaches in 16%, and progressive neurological deficits in 7%. Discovery was fortuitous in 2.7% of cases. Before radiosurgery, 57% were embolized, 5% were operated, 4.5% were reirradiated and 1.8% were operated and embolized. Distribution according to Spetzler & Martin's grade was following: 0% in grade I, 12% in grade II, 41% in grade III and 46% in grade IV. No patient was in grade V.

RESULTS

Global obliteration rate was 39% for large cerebral arteriovenous malformations. In multivariate analysis, only recovering (positive correlation), and previous embolization (negative correlation) were correlated with obliteration rate.

CONCLUSION

Current procedures of radiosurgery allow obliteration in a limited number of large cerebral arteriovenous malformations treated. Other strategies as fractioned irradiation, multileaf microcollimators with single isocenter, radiosurgery before surgery or radiosurgery with protons should improve obliteration rate.

[Surgical removal of radio-induced lesions after radiosurgery of cerebral arteriovenous malformations]

Radioinduced lesions after radiosurgery of cerebral arteriovenous malformations may be associated with an increased signal on T2-weighted and gadolinium enhancement on T1-weighted MR images. They do not have necessarily a poor prognosis. These lesions are mostly asymptomatic. But in a few cases they can be associated with severe clinical symptoms which can become corticodependant or corticoresistant. We present the 5 cases of such cerebral arteriovenous malformations treated by radiosurgery, out of our series of 705 patients. The removal was easier than that of untreated cerebral arteriovenous malformations, and led to a complete recovery of symptoms and progressive decrease of imaging abnormalities. Such surgery should be proposed in case of symptomatic radioinduced lesions which fail to respond to steroids.

[Cerebral arteriovenous malformations treated by radiosurgery: a series of 705 cases]

BACKGROUND AND PURPOSE

After a review of the main radiosurgical published series, to evaluate our own series of 705 patients with cerebral arteriovenous malformations treated by radiosurgery alone or in combination with embolization or surgery.

PATIENTS

and method. From January 1984 to December 1998, 705 patients were treated by a multidisciplinary team including neurosurgeons, neuroradiologists, radiophysicians and radiotherapists. Age of revelation of the cerebral arteriovenous malformations ranged between birth to 73 years (mean 27, median 25). Age at time of radiosurgery ranged between 7 and 75 years (mean 33, median 31). There were 410 males for 295 females (sex- ratio 1.4). Symptoms of revelation were hemorrhage for 59%, seizures for 23%, headaches for 14% and progressive deficits for 4%. Discovery of cerebral arteriovenous malformation was fortuitous in 4% of cases. Repartition following Spetzler's grading was 12% in grade I, 36% in grade II, 40% in grade III, 12% in grade IV and 0% in grade V. Maximal size ranged between 4 and 60 mm (mean 23, median 20). Volume ranged between 0.2 and 24.3 cc (mean 3.8, median 2.8). Majority of cerebral arteriovenous malformations were large size (42% with size higher than 25 mm) and large volume (54% higher than 10 cc. 54% of patients had treatment prior radiosurgery: 38% had embolization, 10% were operated, 4% were treated by radiosurgery (reirradiation) and 3% were operated and embolized.

RESULTS

Overall complete obliteration rate was 55%. The obliteration rate was correlated with size (77% for cAVMs lower than 15 mm, 62% for cerebral arteriovenous malformations between 15 and 25 mm, and 44% for cerebral arteriovenous malformations higher than 25 mm), with volume (94% for cerebral arteriovenous malformations lower than 1 cc, 64% between 1 and 4 cc, 48% between 4 and 10 cc, and 62% for cerebral arteriovenous malformations higher than 10 cc), dose at reference isodose, minimal dose, morphological parameters (presence of dural components, arteriolovenous fistula, plexiform angioarchitecture, arterial steal, arterial recruitment, deep exclusive drainage, venous plicature, venous confluence, venous ectasia, venous reflux), sectional topography and good recovery of the target. Embolization was a confusion factor not associated with obliteration rate. After multivariate analysis, only Dmin and complete coverage of the cerebral arteriovenous malformations were correlated with obliteration rate. Delay of obliteration was significantly correlated after multivariate analysis with Dmin, complete coverage, arteriolovenulary angioarchitecture (positive correlation) and venous ectasia (negative correlation).

CONCLUSION

Overall complete obliteration rate is unreliable data to assess efficacy of radiosurgical method in the tretment of cerebral arteriovenous malformations. The obliteration rate must be interpretated after stratification on several morphological and dosimetric parameters.

[Hemorrhage after radiosurgery of cerebral arteriovenous malformations]

BACKGROUND AND PURPOSE

Obliteration is progressive after radiosurgery of cerebral arteriovenous malformations. Thus the hemorrhage risk still remains until obliteration. Purposes of this study are to appreciate severity of post-radiosurgery hemorrhages, actuarial risk of hemorrhage and parameters associated with it.

PATIENTS

and method. Over 705 patients treated, 46 (6.5%) had one or several hemorrhages. Clinical, anatomic, dosimetric parameters and obliteration rates before hemorrhage were studied. Then, actuarial risks per patient and per hemorrhage were calculated. Correlations between parameters and risk were searched by uni and multivariate analysis by drawing hemorrhage-free survival curves (limit-product Kaplan-Meier) and Cox model.

RESULTS

Except one pure ventricular hemorrhage causing death of one patient, only parenchymal hemorrhages were associated with morbidity (80% of cases with 45% of permanent deficits). Overall mortality rate by hemorrhage was 6.5%. Overall morbidity rate was 34.8% and 13.6% for permanent deficit. Mean obliteration rate before hemorrhage was 25%. Actuarial hemorrhage rate were 2.98% per patient and 3.24% per hemorrhage. Actuarial rate per patient increased from 1.46% first year to 5.95% 4(th) year after radiosurgery. Parameters correlated with hemorrhage risk were in univariate analysis size (p=0.01), Spetzler and Martin's grade (p<0.001), dose to reference isodose (p=0.03), Dmin (p=0.08), intra or paranidal aneurysms (p<0.001), and recoverage (p<0.001). After multivariate analysis, only intra or paranidal aneurysms, recovering and Dmin were significantly associated with hemorrhage-free survival after RS.

CONCLUSIONS

Post-radiosurgery hemorrhages are often sum of hemorrhage risk factors of the cerebral arteriovenous malformation and factors predicting low rate of obliteration. They can be in some cases foreseen but rarely avoided.

[Retrospective analysis of failures in radiosurgery treatment of cerebral arteriovenous malformations]

The aim of this paper is to analyze retrospectively the reasons for the failure in cerebral arteriovenous malformations radiosurgery. Several factors are evoked and discussed mainly: inaccurate target, intentional partial irradiation, repermeabilization of a previously embolized cerebral arteriovenous malformation. The results suggest the necessity of a complete irradiation of the nidus. The strategy of partial volume irradiation should be avoided, even if it necessitates lowering of the doses in large cerebral arteriovenous malformations. Accuracy in the target determination is required and a complete stereoangiography is necessary.

[Re-irradiation of cerebral arteriovenous malformations. Experience of the Sainte-Anne-Tenon Group]

BACKGROUND AND PURPOSE

Between 20 to 50% of cerebral arteriovenous malformations treated with radiosurgery (RS) fail to obliterate 2 to 5 years after irradiation. Patients are not protected against the risks leading to treatment. Two therapeutic options can be used to eradicate the persisting nidus: micro-surgery and a second irradiation. Our group has reirradiated 39 such patients.

MATERIAL

From 1989 to 2000, 39 patients have been reirradiated (14 females and 25 males; median age 31 years). There were more left lesions: 59% than right (35%) and 5% on midline. The most frequent locations were: temporal 12 cases; parietal 8 cases; frontal 7 cases; thalamus 7 cases. The predominant first symptoms were hemorrhage (68.5%) and seizure (15.8%). Prior RS, 21/39 patients had embolization (53.8%) and 3 surgery. Method. Treatment has been performed with the same system for the first and the second radiosurgery for 37 patients. Planification and dosimetry improved during that period. The level of dose was similar for the 2 RS. MRI has been used as a non invasive follow-up tool.

RESULTS

Only 28 patients were evaluable because 7/39 patients had the second radiosurgery in 1999 or in 2000 and data were lacking at the time of writing for 4 patients. Obliteration rate was 17/28 (60.7%). Nine patients bled between the two radiosurgery procedures.

COMPLICATIONS

4 new regressive deficits occurred after the second radiosurgery. The rate of parenchymal changes were higher, after the second radiosurgery. Except one patient who died of a non-related affection 2 years after obliteration of his cerebral arteriovenous malformation, thus 38/39 patients were alive.

CONCLUSION

This series was small compared to the potential number of candidates suffering from failure of the first radiosurgery, but the results are promising.

[Treatment of cerebral arteriovenous malformations: decision making strategy]

We have evaluated our therapeutic strategy through the results of modalities used alone or in association. Should the place of each modality be modified? What could be the influence of the first consulting physician? We feel at the present time that small cerebral arteriovenous malformations could be treated by radiosurgery, surgery and embolization according to their characteristics and location. For middle size and some large cerebral arteriovenous malformations, we consider that embolization and/or surgery are adjuvant modalities, specifically when the cerebral arteriovenous malformation is located in an eloquent area.

Définition automatique de l’isodose de prescription pour les irradiations stéréotaxiques de malformations artérioveineuses

PURPOSE

To evaluate dosimetric consequences generated by the automatic definition based on lesion coverage of prescription isodose. A clinical series of 124 arteriovenous malformations was analysed. Plan quality was quantified by the standard deviation of the differential dose volume histogram calculated in the lesion.

MATERIAL AND METHODS

We define two quantitative protocols based on lesion coverage for the automatic definition of prescription isodose using a volumetric definition of coverage (90% of lesion volume), and an isodose-based definition proposed by RTOG (prescription isodose equals minimum isodose in the lesion divided by 0.9).

RESULTS

We have evaluated the plans obtained for these two protocols, calculating several dose-volume indices. These indices are presented as a function of dose-volume histogram standard deviation in order to quantify the consequences of their variations for this representative series of plans. The margin our team tolerates is such that the sum of underdosed lesion and overdosed healthy tissues factors remains lower than one. Protocol based on volumetric coverage gives results situated within this margin. Protocol based on RTOG definition produces conformation indices that could be greater than 1.

CONCLUSION

The absolute dose would be decided taking into account examined dose-volume indices and clinical data. A protocol for automatic definition of prescription isodose using volumetric lesion coverage seems to be more judiciously adapted to arteriovenous malformation conformal plans in stereotactic conditions because of variations observed in the overdosage of healthy tissues.

Dose-volume analysis of different stereotactic radiotherapy mono-isocentric techniques

Several stereotactic irradiation techniques, using Linacs with the patient in lying and sitting position and a Gamma Knife Unit, were compared with regard to mono-isocentric three-dimensional dose distributions. Three types of target volumes, a sphere and two ellipsoids, were used for the comparisons. All three targets were centered on a real head, reconstructed from transversal CT scans. The ARTEMIS 3D Treatment Planning System, developed by the Tenon Hospital, Paris, was used for the dosimetry and the dose-volume histogram (DVH) calculation. For the comparative study, several quantitative parameters were used, derived from the dose-volume histogram calculation. Differential DVHs were plotted for each target volume and beam arrangement. Irradiation techniques were compared by deriving quantitative parameters from the DVHs such as mean and integral dose delivered to the target and normal tissue irradiated, as well as by the relative volume of the examined areas. All techniques used in this study produced very similar dose distributions. The small differences confirm the capability of the studied techniques to produce the same irradiation effects. By changing from the spherical target shape to a more elliptical shape, more of the normal tissue was irradiated with higher doses. For elliptical cases we therefore identified a need for more conformal stereotactic planning.

Linac radiosurgery for cerebral arteriovenous malformations: results in 169 patients

PURPOSE

To present the SALT group results using Linac radiosurgery (RS) for AVM in 169 evaluable patients treated from January 1990 thru December 1993.

METHODS AND MATERIALS

Median age was 33 years (range 6-68 years). Irradiation was the only treatment in 55% patients. Other treatment modalities had been used prior to RS in 45%: one or more embolizations in 36%, surgery in 6%, and embolization and surgery in 3% patients. Nidus were supratentorial in 94% patients, infratentorial in 6% patients. Circular 15 MV x-ray minibeams (6-20 mm) were delivered in coronal arcs by a GE-CGR Saturne 43 Linac. Patient set-up included a Betti arm-chair, a Talairach frame. Prescribed peripheral dose was 25 Gy on the 60%-70% isodose (max dose 100%). Arteriographic results were reassessed in December 1997 at 48 to 96 months follow-up.

RESULTS

The overall obliteration rate (OR) was 64% (108/169). AVM volumes ranged from 280 to 19,920 mm(3), median 2460 mm(3). OR was 70% for AVM </= 4200 mm(3) 4200 mm(3) (p 25 mm (p = 0.04). OR was 71%, in the absence of embolization, vs. 54% for previously embolized nidus (p = 0.03). OR was 71% for monocentric RS vs. 54% for multi-isocenters (p 28 Gy vs. 55% for values </= 28 Gy (p 79% vs. 57% for lower values (p 17 Gy, vs. 59% for mLd </= 16 Gy (p 40%, vs. 54% for mLi </= 40% (p 85% vs. 60% for CR </= 84% (NS). For patients treated according to our protocol, i.e., 24-26 Gy on the 60%-70% isodoses, OR was higher (68%) than for other patients (47%) (p = 0.02). After multivariate analysis, absence of previous embolization and mono isocentric-irradiation were independent factors predicting obliteration. Complications were: recurrent hemorrhage, 4 patients (1 patient died); brain necrosis on MRI, 2 patients; subsequent epilepsy, 4 patients; other subsequent neurologic deficits, 3 patients.

CONCLUSION

Overall OR was 64% (48-96 months follow-up). After monovariate analysis higher ORs were associated with smaller volumes </= 4200 mm(3), smaller nidus size </= 25 mm, absence of prior embolization, monoisocentric RS, higher values for mean and minimum lesion doses and compliance to our protocol. Higher values for the peripheral dose and isodose tended to give better results. Multivariate analysis showed that the absence of prior embolization and monoisocentric irradiation were independent factors predicting successful irradiation.