囊性颅咽管瘤立体定向囊腔内放疗的临床研究

目的　探讨囊性颅咽管瘤囊腔内放疗的有效性和安全性。方法　对 5 6例囊性颅咽管瘤行CT引导立体定向囊腔内放疗 ,根据个体化剂量设计分别置入 1～ 3次、2 .4～ 14 .8MBq不等胶体磷酸铬 (Cr3 2 Po4) ,并进行临床随访观察。结果　 5 6例患者术后神经功能均很快出现不同程度的改善。随访 6个月至 9年 ,49例视力、视野障碍中 ,45例获得逐渐改善 ,4例恶化 ,偏瘫 3例恢复正常 ,所有内分泌功能障碍者均获得稳定或不同程度好转 ,复查CT或MR示 :5例瘤实质增大 (9% ) ,2例新的囊腔形成 ,1例导管在脑室内囊腔略缩小 ,囊腔完全消失 2 4例 (4 3 % ) ,囊腔明显缩小 (>80 % )2 4例 (86% )。无手术死亡及严重并发症。结论　立体定向囊腔内放疗是一种治疗囊性颅咽管瘤的安全而有效方法 ,放射剂量设计的个体化是提高治疗有效率的关键。     

Phosphorus-32 therapy for cystic craniopharyngiomas

Background and purpose

To examine control rates for predominantly cystic craniopharyngiomas treated with intracavitary phosphorus-32 (P-32).

Material and methods

22 patients with predominantly cystic craniopharyngiomas were treated at Indiana University between October 1997 and December 2006. Nineteen patients with follow-up of at least 6 months were evaluated. The median patient age was 11 years, median cyst volume was 9 ml, a median dose of 300 Gy was prescribed to the cyst wall, and median follow-up was 62 months.

Results

Overall cyst control rate after the initial P-32 treatment was 67%. Complete tumor control after P-32 was 42%. Kaplan-Meier 1-, 3-, and 5-year initial freedom-from-progression rates were 68%, 49%, and 31%, respectively. Following salvage therapy, the Kaplan-Meier 1-, 3-, and 5-year ultimate freedom-from-progression rates were 95%, 95%, and 86%, respectively. All patients were alive at the last follow-up. Visual function was stable or improved in 81% when compared prior to P-32 therapy. Pituitary function remained stable in 74% of patients following P-32 therapy.

Conclusions

Intracystic P-32 can be an effective and tolerable treatment for controlling cystic components of craniopharyngiomas as a primary treatment or after prior therapies, but frequently allows for progression of solid tumor components. Disease progression in the form of solid tumor progression, re-accumulation of cystic fluid, or development of new cysts may require further radiotherapy or surgical intervention for optimal long-term disease control.     

Effects of radiosynovectomy with p-32 colloid therapy in hemophilia and rheumatoid arthritis

AIM: The aim of this study was to assess the effects of treatment with our locally produced P-32 colloidal suspension on knee synovitic inflammations of hemophilic and rheumatoid arthritis (RA) patients, as well as to compare results with chemical synovectomy or corticoid intra-articular injections and evaluate the cost-benefit ratio. MATERIALS AND METHODS: Thirty-six hemophilic male patients, 4-28 years of age and sent by the Hemophilic Foundation (Buenos Aires, Argentina), were enrolled for knee radiosynovectomy (RS) with P-32 colloid (26 patients), or the antibiotic rifampicin with the cooperation of orthopaedists (10 patients). Parents' informed consent was obtained. The following procedures were performed: routine blood tests, X-ray, ultrasound, a 3-phase bone scan, plus monthly methylene diphosphonate (MDP) controls. Patients were included in this study only if several knee episodes had occurred. Exclusion criteria included bone destruction and big Baker's cyst. Twelve RA patients were included, with similar selection criteria: 6 RA patients received P-32 therapy, and the other 6 patients intra-articular corticoids. Clinical, blind evaluation (state of joint involvement, pain, motility, requirements of antihemophilic factors, corticoids, or analgesics) was registered in follow-up charts. If required, joint aspiration was carried out. Intra-articular instillation of saline plus flushing was done before the needle was withdrawn. P- 32 Bremsstrahlung emission was used in the gamma camera for early and late imaging to confirm the absence of leakage. For intra-articular chemical injections therapy, 4 MBq of Tc-99m MAA (macroaggregates) was used. Immobilization and relative rest for 72 hours followed the procedures. RESULTS: There were neither local or systemic effects, nor leakage during P-32 treatment. Intra-articular rifampicin and corticoids procedures required frequent injections. Comparison of regions of interest (ROIs) in treated knees during soft-tissue scintigraphies in pre- and post-third MDP control showed knee improvement. The follow-up evaluation demonstrated an increase in joint motion, diminished volume, and less requirement and frequency of the use of antihemophilic factors (AHF) in 80% of the radiosynovectomies (21 of 26), thus lowering health costs. Five female RA patients (5 of 6) had decreased joint swelling and pains, resulting in increased joint motion. CONCLUSIONS: Radiosynovectomy in RA showed a 3-month pain palliative effect. One intra-articular knee radiosynoviorthesis in haemophilic patients provides a more than 3- month relief of symptoms after treatment with locally produced P-32 (11 patients). This turned out to be a safe, economic alternative procedure in emerging nations where the availability of AHF is difficult and expensive.     

186Re内放射治疗颅咽管瘤的临床疗效

目的 评价应用立体定向肿瘤囊腔内注射186Re治疗颅咽管瘤的临床效果.方法 应用立体定向穿刺置管注射186Re方法治疗囊性或囊实性颅咽管瘤19例,其中男性12例,女性7例.年龄5～58岁,平均37.2岁.肿瘤呈囊性者12例,囊实性者7例.注射核素186Re前,颅咽管瘤囊性部分的平均体积为8390 mm3.结果 随访6个月至3年,有7例患者囊腔完全消失,囊腔体积缩小>50%以上者5例,囊腔体积缩小≤50%者7例.治疗前视力减退的8例患者中,5例患者治疗后视力显著改善.治疗前垂体功能正常者无一例出现垂体功能低下;而治疗前垂体功能低下的4例患者中,1例治疗后垂体功能改善.治疗前表现为尿崩症的5例患者中,3例治疗后尿崩症状改善.结论 立体定向肿瘤囊腔内注射186Re是治疗囊性或囊实性颅咽管瘤简单、安全、有效的方法.     

Fractionated stereotactic conformal radiotherapy following conservative surgery in the control of craniopharyngiomas.

PURPOSE: To describe the technique and results of stereotactically guided conformal radiotherapy (SCRT) in patients with craniopharyngioma after conservative surgery. METHODS AND MATERIALS: Thirty-nine patients with craniopharyngioma aged 3-68 years (median age 18 years) were treated with SCRT between June 1994 and January 2003. All patients were referred for radiotherapy after undergoing one or more surgical procedures. Treatment was delivered in 30-33 daily fractions over 6-6.5 weeks to a total dose of 50 Gy using 6 MV photons. Outcome was assessed prospectively. RESULTS: At a median follow-up of 40 months (range 3-88 months) the 3- and 5-year progression-free survival (PFS) was 97% and 92%, and 3- and 5-year survival 100%. Two patients required further debulking surgery for progressive disease 8 and 41 months after radiotherapy. Twelve patients (30%) had acute clinical deterioration due to cystic enlargement of craniopharyngioma following SCRT and required cyst aspiration. One patient with severe visual impairment prior to radiotherapy had visual deterioration following SCRT. Seven out of 10 patients with a normal pituitary function before SCRT had no endocrine deficits following treatment. CONCLUSION: SCRT as a high-precision technique of localized RT is suitable for the treatment of incompletely excised craniopharyngioma. The local control, toxicity and survival outcomes are comparable to results reported following conventional external beam RT. Longer follow-up is required to assess long-term efficacy and toxicity, particularly in terms of potential reduction in treatment related late toxicity.     

32p胶体联合地塞米松治疗甲状腺囊肿的疗效

目的:探讨32p胶体联合地塞米松治疗甲状腺囊肿的疗效及临床价值.方法:采用32p胶体联合地塞米松治疗甲状腺囊肿患者103例,患者按甲状腺囊肿的直径大小分为三组,甲状腺囊肿＜2 cm患者45例,2～ ＜3 cm患者38例,3～ ＜4cm患者20例.患者治疗前后均查FT3、FT4、TSH、TG(甲状腺球蛋白)、TM(甲状腺微粒体)及血常规.用超声及甲状腺显像测量囊肿大小.用药1个疗程之后,经医学影像资料未发现囊肿,则判定治愈;经医学影像资料发现囊肿直径缩小超过1/2,则判定有效;囊肿缩小不到治疗前1/2或无变化,则判定无效.采用卡方检验对结果进行统计.结果:三组的治疗效果比较有显著差异,P ＜0.05.三组治疗前后甲状腺激素及血常规检查未发现异常变化,穿刺液未检出癌细胞.治愈病例随访2年未复发.结论:32p胶体联合地塞米松治疗甲状腺囊肿安全,疗效确切,治愈率高,易被患者接受,具有重要的临床价值.     

32P胶体体外诱导颅咽管瘤细胞凋亡

  目的   探讨32P胶体对颅咽管瘤（craniopharyngioma,CP）体外培养细胞诱导凋亡作用及剂量效应和时间效应关系。   方法   通过原代细胞培养获得CP有限传代细胞系,经不同浓度32P胶体处理不同时间后,应用MTT比色法绘制细胞存活率曲线。流式细胞仪定量检测细胞凋亡率。Hoechst 33342荧光染色检测凋亡细胞形态。TUNEL荧光染色检测DNA特征改变。透射电子显微镜（TEM）检测细胞超微结构。   结果   Hoechst 33342荧光染色、TUNEL荧光染色、TEM均证实32P胶体确能引起CP细胞产生凋亡。随着32P胶体处理浓度（0~14.80 MBq/mL）及时间（1~14 d）的增加,CP细胞存活率减少、凋亡率增高。   结论   32P胶体能明显抑制CP体外培养细胞生长并诱导凋亡,剂量越大及处理时间越长其杀伤作用越强。      

Continuous low-dose-rate radiation of radionuclide phosphorus-32 for hemangiomas

The study goal was to clarify the therapeutic effect and the absorbed dose of radionuclide phosphorus-32 for skin hemangiomas and the consequent risk of side effects in these patients. Phosphorus-32 is an β emitter and is used for skin hemangioma treatment. In comparison with the few Gy per minute of the linear accelerators, the dose rate of phosphorus-32 for hemangiomas is much <1 Gy/hour; so, the latter is called low-dose-rate radiation. To achieve the therapeutic dose, continuous hours or days of radiation is necessary. For strawberry hemangiomas, the phosphorus-32 applicator was tightly placed on the lesion site for several hours until reaching therapeutic dose. The absorbed dose was estimated by radiochromic films. The absorbed dose of phosphorus-32 irradiation declined exponentially with a depth from 0 to 2.5 mm. Of the 316 patients with strawberry hemangiomas, the lesion disappeared completely within 3 months after one-time treatment in 259 cases (82%). For cavernous hemangiomas, 370KBq phosphorus-32 colloid was injected into the hemangioma each square centimeter, and the absorbed radiation was estimated by theoretical calculation. Forty-two of the 58 patients with cavernous hemangiomas (72%) had lesions that completely disappeared within 3 months after receiving one to six treatments. Thus, the phosphorus-32 for strawberry hemangiomas and the chromium phosphate-32 colloid for cavernous hemangiomas were clearly efficacious.     

Intraoperative MR-guided instillation of phosphorus-32 for cystic craniopharyngiomas: case report

Intraoperative magnetic resonance imaging has been applied to a number of neurosurgical disease processes since the late 1990's. The ability to visualize the operative site in near-real time has added a significant degree of safety to the treatment of lesions such as a cystic craniopharyngioma which can be located in regions of the brain where an untoward consequence can result in significant neurological morbidity. Previous surgical techniques, although often successful, did not allow the neurosurgeon to directly visualize whether the goals of surgery had been met or whether there was an inadvertent complication associated with the surgical approach until after the event had occurred. The safe and accurate instillation of radioactive phosphorus into this cystic tumor resulted in clinical improvement and the maintenance of normal pituitary function for this patient. The extreme accuracy and safety of this surgical technique is demonstrated by the imaging examples provided.     

An early phase II study of intratumoral P-32 chromic phosphate injection therapy for patients with refractory solid tumors and solitary metastases

BACKGROUND: In this early Phase II study, the authors investigated the efficacy of intratumoral injection of P-32 chromic phosphate in 17 patients with refractory solid tumors or solitary metastases in terms of response rates and overall survival. METHODS: Seventeen patients (median age, 60 years) with either cytostatic drug-resistant tumors or tumors known to be primarily chemotherapy-resistant were entered into the study. After sonographic determination of the tumor volume, P-32 chromic phosphate (74-555 MBq) was injected into the central part of the tumor under sonographic guidance. Follow-up investigations included serial scintigraphy, sonographic examinations, and hematologic studies. RESULTS: Injection of P-32 chromic phosphate into refractory tumors resulted in remarkable regression. The median survival of all patients was 13 months (range, 8-25 months). The response rate was 71% (12 patients). A complete remission was seen in 7 patients (41%), and the rate of partial remissions was 29% (5 patients). However, 5 patients (30%) did not respond to the treatment. In one patient thrombocytopenia was observed, but no other side effects were apparent. Important pathologic and anatomic changes within the tumor tissue were demonstrated in solitary liver metastases of gastrointestinal malignancies excised in second-look operations. In all cases examined, formation of a cyst within the area of central activity, surrounded by a centrifugal necrotic ring and a marginal fibrotic structure, was found. CONCLUSIONS: Lack of persistent systemic or local side effects, as well as noteworthy efficacy, are properties of this optimal regional treatment modality with P-32 chromic phosphate. This modality deserves consideration for further clinical trials.     

颅咽管瘤的MRI诊断及鉴别诊断颅咽管瘤的MRI诊断及鉴别诊断

目的:研究颅咽管瘤的MRI诊断及鉴别诊断。方法:回顾性分析经病理证实的13例颅咽管瘤的MRI表现。结果:9例呈圆形或类圆形,4例呈不规则形。平扫6例表现为长T1长T2信号,3例表现为等T1长T2信号,2例短T1长T2信号,1例等T1短T2信号,1例混杂T1混杂T2信号。其中囊内见出血1例,分层征象2例,钙化3例,壁结节4例,3例DWI弥散不受限呈低信号。增强后3例实性颅咽管瘤和5例囊实性颅咽管瘤实性部分明显均匀或不均匀强化,5例囊实性和4例囊性颅咽管瘤囊壁呈弧形或环形强化,4例囊性颅咽管瘤壁结节明显强化,1例囊性颅咽管瘤未见明显强化。结论:颅咽管瘤的MRI影像表现具有一定特征,但需注意与垂体腺瘤、Rathke囊肿、生殖细胞瘤等鉴别。     

Intracavitary brachytherapy using stereotactically applied phosphorus-32 colloid for treatment of cystic craniopharyngiomas in 53 patients

This paper summarizes outcomes of a single-center study of intracavitary brachytherapy (IBT) with stereotactically applied phosphorus-32 ((32)P) colloid for treatment of cystic craniopharyngiomas. We assessed its efficacy and safety, on the basis of clinical and radiological outcomes in one of the largest reported patient series. Between 1992 and 2011, 53 patients were treated with IBT, 14 without previous treatment and 39 who had previously been treated for recurrent cysts. Intervention was performed by applying 200?Gy to the internal cyst wall (median volume 6.1?ml). Median clinical and radiological follow-up were 60.2 and 53.0?months, respectively. Actuarial tumor cyst control was 86.0?±?5.3?% at 12, 24, and 60?months. Actuarial out-of-field control (development of new cysts or progression of solid tumor parts) was 90.9?±?4.3, 84.0?±?5.6, and 54.5?±?8.8?% after 12, 24, and 60?months, respectively. Corresponding actuarial overall progression-free survival was 79.4?±?6.1, 72.4?±?6.8, and 45.6?±?8.7?% at 12, 24, and 60?months, respectively. Visual function improved for 12 patients (23.5?%), remained unchanged for 34 patients (66.7?%), and worsened for five patients (9.8?%), correlating with tumor progression in each case. Endocrinological deterioration occurred for ten patients (19.6?%); for nine patients this was a result of tumor progression or after tumor resection and for one it was attributed to irradiation. Within six months of IBT seven patients (13.7?%) experienced transient neurological deficits and two patients (3.9?%) deteriorated permanently (hemiparesis and third nerve palsy). Stereotactically applied (32)P is highly efficacious for control of cystic components of craniopharyngiomas and is associated with a low risk of permanent morbidity. The procedure does not, however affect the development of new cysts or the progression of solid tumor parts.     

A geometrically based method for automated radiosurgery planning

Purpose: A geometrically based method of multiple isocenter linear accelerator radiosurgery treatment planning optimization was developed, based on a target’s solid shape.

Methods and Materials: Our method uses an edge detection process to determine the optimal sphere packing arrangement with which to cover the planning target. The sphere packing arrangement is converted into a radiosurgery treatment plan by substituting the isocenter locations and collimator sizes for the spheres.

Results: This method is demonstrated on a set of 5 irregularly shaped phantom targets, as well as a set of 10 clinical example cases ranging from simple to very complex in planning difficulty. Using a prototype implementation of the method and standard dosimetric radiosurgery treatment planning tools, feasible treatment plans were developed for each target. The treatment plans generated for the phantom targets showed excellent dose conformity and acceptable dose homogeneity within the target volume. The algorithm was able to generate a radiosurgery plan conforming to the Radiation Therapy Oncology Group (RTOG) guidelines on radiosurgery for every clinical and phantom target examined.

Conclusions: This automated planning method can serve as a valuable tool to assist treatment planners in rapidly and consistently designing conformal multiple isocenter radiosurgery treatment plans.     

Therapeutic benefits of combination chemotherapy with vincristine,BCNU, and procarbazine on recurrent cystic craniopharyngioma

Summary The authors report a case of recurrent cystic craniopharyngioma managed with chemotherapy. The patient refused adamantly the alternative therapy methods, such as surgery and radiotherapy, initially offered. Eight courses of chemotherapy with vincristine (2 mg/M², i.v.) on day 1, 1,3-bis(2-chloroethyl)-1-nitrosourea (100 Mg/M², i.v.) on day 2, and procarbazine (50 mg, b.i.d., p.o.) on days 3 to 21 were administered at 6 week intervals. The effectiveness of this treatment modality has been evaluated by the unequivocal neurological improvement and by the decreases in size of the cyst using serial computerized tomography. Toxocities were mild and chiefly hematological.     

Intracystic bleomycin therapy for craniopharyngioma in children: the Canadian experience

BACKGROUND: Surgical removal and radiation therapy are associated with significant risk for morbidity in the pediatric population with craniopharyngioma. Intracystic therapies have been utilized in some centers to potentially decrease morbidity associated with cystic craniopharyngioma. The aim of the study was to review the Canadian experience with intracystic bleomycin therapy (ICB). METHODS: All centers in the Canadian Pediatric Brain Tumor Consortium (CPBTC) were invited to participate in a retrospective review of this treatment. A questionnaire was sent to each center. The data were analyzed at British Columbia's Children's Hospital. RESULTS: In all, 6 of 17 centers utilized ICB and submitted data. A total of 17 of 19 patients with the intention to treat received bleomycin. Twelve were treated at the time of diagnosis, and 5 at the time of recurrence. Five patients achieved a complete response, 6 achieved a partial response, and 5 achieved a minor response to bleomycin. One patient was stable for 2.8 years. At the time of last follow-up, 8 patients have not required further intervention. Complications included transient symptomatic peritumoral edema (2 patients), precocious puberty (1 patient) and panhypopituitarism (2 patients). The median follow-up was 4 years (range, 0.5-10.2 years). The median progression-free survival was 1.8 years (range, 0.3-6.1 years). One patient died of a massive infarct secondary to radiation-induced moyamoya syndrome. CONCLUSIONS: ICB was found to be well tolerated in this group of children. ICB may be a feasible and effective therapy for certain children with craniopharyngioma. Bleomycin may delay the need for aggressive surgery or radiation therapy for several years. Prospective multiinstitutional clinical trials are required to further evaluate the feasibility, effectiveness, and dose schedules of this treatment.     

卵巢癌组织及腹腔积液中肿瘤干细胞的分离与培养

目的:从人卵巢癌组织和腹腔积液中分离培养肿瘤干细胞,分析细胞表型和化疗药物敏感性。方法:取卵巢浆腺癌患者的原发肿瘤组织及腹腔积液,通过无血清培养形成悬浮生长的球体。采用FCM及免疫荧光法检测干细胞标志物的表达。体外药敏实验检测获得的球体细胞和分化细胞对紫杉醇和卡铂的药物敏感性。结果:卵巢癌组织及腹腔积液中的卵巢癌细胞经无血清悬浮培养可以形成球体,后者具有CD44+CD24-表型并表达Oct4、Nanog及Sox2等干细胞标志物;腹腔积液及组织来源的球体细胞经血清培养液培养3周后发生分化,CD44+CD24-细胞比例分别下降至47%和3%;分化细胞对紫杉醇和卡铂的敏感性均显著高于球体细胞(P<0.01)。结论:卵巢癌的肿瘤干细胞属于CD44+CD24-细胞,后者表达Oct4等干细胞标志并具有显著耐药性。     

Initial clinical results of stereotactic radiotherapy for the treatment of craniopharyngiomas

The efficacy and toxicity of stereotactic radiotherapy (SRT) for the treatment of craniopharyngioma has been retrospectively evaluated in 16 patients. The median tumor diameter was 2.8 cm (range 1.5-6.1) and the median tumor volume was 7.7 cc (range 0.7-62.8). SRT was delivered to a single isocenter using a dedicated 6 MV linear accelerator to patients immobilized with a relocatable stereotactic head frame. The three-year actuarial overall survival was 93% and the rate of survival free of any imaging evidence of progressive disease was 75%. The three-year actuarial survival rates free of solid tumor growth or cyst enlargement were 94% and 81% respectively. Our results suggest that SRT is a safe and effective treatment approach for patients with craniopharyngioma. Long-term follow-up is required to determine whether the normal tissue-sparing inherent with SRT results in reduction of the neurocognitive effects of conventional radiotherapy for craniopharyngioma. SRT can be delivered to craniopharyngioma that may be difficult to treat with stereotactic radiosurgery due to proximity of the optic chiasm. Further clinical experience is necessary to determine the clinical utility of beam shaping in the setting of SRT.     

High precision conformal radiotherapy employing conservative margins in childhood benign and low-grade brain tumours.

BACKGROUND AND PURPOSE: To report local control and follow up outcome data of high precision conformal radiotherapy in childhood brain tumours. MATERIALS AND METHODS: Between December 1999 and December 2002, 26 children (17 boys and 9 girls, median age 11.5 years) with incompletely excised or recurrent benign and low-grade brain tumours [13 craniopharyngiomas, 11 low-grade gliomas (LGG) and 2 others] were treated with three-dimensional (3D) conformal radiotherapy (CRT) (12 patients) and stereotactic conformal radiotherapy (SCRT) (14 patients). Gross tumour volume (GTV) included neuro-imaging based visible tumour and/or resected tumour bed. Clinical target volume (CTV) consisted of GTV+ 5 mm margin and planning target volume (PTV) consisted of additional 5 mm margin for CRT and 2 mm for SCRT. Treatment was delivered with 3-9 conformal fixed fields to a median dose of 54 Gy/30 fractions. RESULTS: The actuarial 2 and 3 year disease free and overall survival was 96 and 100%, respectively (median follow up: 25 months, range 12-47 months). Radiological follow up available in 25 patients revealed complete response in 1, partial regression in 10, stable disease in 13 and progression in 1 patient (within the CTV). One patient with craniopharyngioma on a routine imaging revealed a mild asymptomatic cyst enlargement, which resolved with conservative management. A patient with chiasmatic glioma developed cystic degeneration and hydrocephalus 9 months after SCRT requiring cyst drainage and placement of a ventriculoperitoneal shunt. CONCLUSION: High-precision conformal techniques delivering irradiation to a computer generated target volume employing 7-10 mm 3D margins beyond the visible tumour and/or resected tumour bed appear to be safe in children with incompletely resected or recurrent benign and low-grade brain tumours, based on these data.     

Monitor units are not predictive of neutron dose for high-energy IMRT

ABSTRACT: BACKGROUND: Due to the substantial increase in beam-on time of high energy intensity-modulated radiotherapy (>10 MV) techniques to deliver the same target dose compared to conventional treatment techniques, an increased dose of scatter radiation, including neutrons, is delivered to the patient. As a consequence, an increase in second malignancies may be expected in the future with the application of intensity-modulated radiotherapy. It is commonly assumed that the neutron dose equivalent scales with the number of monitor units. METHODS: Measurements of neutron dose equivalent were performed for an open and an intensity-modulated field at four positions: inside and outside of the treatment field at 0.2 cm and 15 cm depth, respectively. RESULTS: It was shown that the neutron dose equivalent, which a patient receives during an intensity-modulated radiotherapy treatment, does not scale with the ratio of applied monitor units relative to an open field irradiation. Outside the treatment volume at larger depth 35% less neutron dose equivalent is delivered than expected. CONCLUSIONS: The predicted increase of second cancer induction rates from intensity-modulated treatment techniques can be overestimated when the neutron dose is simply scaled with monitor units.     

Kinetics of depression and recovery of murine hepatic cytochrome P-450 levels after treatment with the interferon inducer polyriboinosinic-polyribocytidylic acid

In vivo treatment of randombred Swiss Webster mice with polyriboinosinic-polyribocytidylic acid (poly l X poly C) inhibited the induction of cytochrome P-450's by both 3-methylcholanthrene [(MCA) CAS: 56-49-5] and phenobarbitol [(PB) CAS: 50-06-6]. Concomitant treatments with poly l X poly C and a single dose of MCA inhibited the induction of P-450's for 24 hours and delayed the obtainment of the MCA-induced P-450 levels for approximately 48-72 hours. When cytochrome P-450 levels were induced by four successive daily treatments of MCA or PB and when poly l X poly C was given on only the 1st day, induction of P-450's was completely suppressed for 24 hours and obtainment of the maximal P-450 level was delayed by 72-96 hours. Treatment with poly l X poly C of animals preinduced for P-450's by four successive daily treatments with either PB or MCA decreased the P-450 content to the noninduced basal level within 24 hours. The effect was temporary in the MCA-treated mice since P-450 content recovered to the MCA-preinduced levels within 72 hours. PB-dependent P-450 induction was short lived, and no recovery occurred after poly l X poly C treatment of PB-preinduced mice. Reduced hepatic cytochrome P-450 contents correlated with decreased abilities of liver homogenates to metabolically activate benzo [a]pyrene (CAS: 50-32-8) and N-acetyl-2-aminofluorene (CAS: 53-96-3), as scored in an Ames Salmonella typhimurium revertant assay.