A technique for combining microwave hyperthermia with intraluminal brachytherapy of the oesophagus

A technique for combining microwave hyperthermia with 192Ir brachytherapy for the treatment of oesophageal carcinoma is described. This approach uses an intraluminal afterloading applicator and up to six microwave antennae to deliver both hyperthermia and brachytherapy, with minimal modification of the existing procedure for brachytherapy alone. Each microwave antenna includes a built-in thermistor to control temperature and balance power. Longitudinal temperature distributions were measured in situ from within the applicator, and at the applicator-tissue interface in vivo. Two-dimensional SAR and steady-state temperature distributions measured in muscle-equivalent phantom are presented and discussed. The technique appears to be capable of elevating tissue temperature to greater than 42 degrees C in a radially symmetric volume of length greater than 5 cm, with radial penetration of 0.5 cm. The clinical technique is relatively simple and well tolerated.

The accuracy of temperature measurement from within an interstitial microwave antenna

Temperature measurement from within microwave interstitial antennas is a promising new development for hyperthermia. These antennas could enable the development of multipoint temperature regulation, leading to improved control of temperature distributions and therefore more effective hyperthermia treatments. In the complex environment of an antenna within a plastic catheter, measured temperatures were found to differ from the estimated local tissue temperature by up to 8 degrees C. In the design evaluated in this report the primary source of this error appears to be self-heating distal to the antenna junction, particularly in the outer copper conductor. The magnitude of self-heating is directly proportional to applied microwave power. Catheter wall thickness, tissue perfusion, and longitudinal temperature gradient also influence the measured temperature.

External beam and intraluminal radiotherapy in the treatment of carcinoma of the esophagus

During a 10-year period, 46 patients with unresectable or inoperable carcinoma of the esophagus were treated with teletherapy-brachytherapy combination at the University of Southern California School of Medicine. Stage distribution was as follows: stage I, 5 (11%) patients; stage II, 23 (50%) patients; stage III, six (13%) patients; and stage IV, 12 (26%) patients. Thirteen patients were treated for recurrent disease, including 11 patients initially treated with teletherapy and two who had had surgical resection. Radiotherapy was given by teletherapy in 33 and brachytherapy in all 46 patients. An average tumor dose was 50 Gy with teletherapy and 20 Gy per application with brachytherapy. There were 25 patients who had more than one brachytherapy application. The 5-year actuarial survival rate for 28 patients with stage I or II disease was 12%, with a median of 13 months. This compared with no 5-year survivals and a median survival of 10 months for the 18 patients with stage III or IV disease. Failure at the primary site was seen in 16 (35%) patients. Complete response was seen in 20%, partial response in 76%, and no response in 4%. Treatment was well tolerated. Complications included esophageal stenosis in two patients and tracheoesophageal fistula in one. Teletherapy-brachytherapy combination is an effective treatment in the management of unresectable or inoperable carcinoma of the esophagus.

Dosimetric calculations and measurements of gold plaque ophthalmic irradiators using iridium-192 and iodine-125 seeds

The dosimetry of ophthalmic plaques designed to hold iridium-192 or iodine-125 seeds is investigated experimentally and by means of a computer model. A phantom for thermoluminescent dosimetry (TLD) which permits measurements to within 2 mm of the plaque surface is described. TLD data are compared with model calculations that take into account the active length of the seeds, anisotropy of dose distribution from single seeds, and scatter within the phantom. An isotropic point source calculational model is accurate for clinical calculations, particularly at depths greater than 5 mm. Relative central axis dose measurements for 125I in a gold plaque are also in agreement with the model. Comparisons of 192Ir, 125I and 60Co plaques are presented. The relative advantages of using these isotopes in eye plaques are discussed.

Interstitial thermoradiotherapy for recurrent or persistent tumours

Between 1984 and 1986, 31 sites in 27 patients with biopsy proven tumours were treated with a combination of interstitial microwave hyperthermia (HT) and iridium 192 implants (RT). The 31 sites treated included fifteen (48 per cent) head and neck, six (20 per cent) breast, four (13 per cent) vagina and cervix, and six (20 per cent) others. All patients had prior surgery, RT, or chemotherapy. Of the 31 sites treated, 19 (61 per cent) had complete response (CR) with no recurrence in the volume treated. Additionally, eight patients remained free of tumour from 3 to 24 months. Partial response (PR) was seen in 11 (36 per cent) sites while one (3 per cent) had lesser degree tumour regression. Tumour control rate correlated well with the dose of radiation, p = 0.02, and tumour volume, p = 0.02, but not with thermal dose. Treatment complications of significance occurred in one (3 per cent) site, which developed soft tissue necrosis. This study again has demonstrated the effectiveness of RT-HT combination in treatment of recurrent tumours.

Backscatter measurements from a single seed of 125I for ophthalmic plaque dosimetry

To determine the dosimetric effect of a gold plaque applicator used in 125I ophthalmic irradiation, relative dose rates at points 2-18 mm transverse to the axis of a single seed of 125I were measured in an acrylic phantom under three different measurement conditions. The detectors were 1-mm diameter X 3-mm length LiF thermoluminescent dosimeters (TLD's). Conditions corresponded to the following: (i) full scatter, (ii) the presence of an ophthalmic gold plaque, and (iii) no scatter material on the side of the seed opposite to the TLD's. The dose rate with the gold plaque is less than that with full scatter phantom. There is no significant decrease in dose rate at 2.2 mm from the seed. Dose rate is significantly reduced at greater distances. The does rate decrease ranges from 4% at 5 mm to 10% at 18 mm. The 125I seed in the gold plaque gives 3%-5% higher dose rate than in the absence of backscatter material.

Treatment of carcinoma of the skin with bone and/or cartilage involvement

From 1956 to 1978, 23 patients with stage T4 carcinoma of the skin of the head and neck were treated with radiotherapy (RT). There were nine patients with cancer of the skin of the nose, eight with tumors of the pinna, and six with lesions of the eyelids. Basal cell carcinoma (BCC) was seen in 61%, squamous cell carcinoma (SCC) in 26%, and 13% of patients had tumors with BCC and SCC features. The majority of patients had large tumors. Less than one-third of patients had smaller lesions, whereas three patients had intermediate-size tumors (greater than 2 cm to less than or equal to 5 cm). Of the 23 patients treated, nine had prior surgical therapy and recurrent or persistent tumor. The remaining 14 patients had no prior therapy. RT was given up to an average total dose of 55 Gy. The 5-year actuarial tumor control rate was 80%. Of the 23 patients treated, four had recurrent tumors. There were no recurrences among the 14 BCC patients, whereas there were four recurrences among the nine SCC and mixed histology patients. Of the four patients who had tumor recurrence, one was salvaged by subsequent radical surgery and three died of their tumor. No serious complications were observed in this group of 23 patients. There was no cartilage, bone, or soft-tissue necrosis noted. RT is a good treatment option and it may be treatment of choice in patients with BCC and SCC of the skin with cartilage or bone involvement. It provides an excellent chance of tumor control, good cosmesis, preservation of function, and a low incidence of complications.

Characteristics of the high-energy photon beam of a 25-MeV accelerator

The CGR Saturne 25 is an isocentrically mounted standing wave medical linear accelerator that produces dual-energy photon beams and a scanned electron beam with six selectable energies between 4 and 25 MeV. The highest energy photon beam is nominally referred to as 23 MV. For this beam the mean energy of the accelerated electron beam on the 1.3 radiation length (4 mm) tungsten x-ray target is found to be approximately 21 MeV, with the energy acceptance stated to be +/- 5%. The electron beam traverses a 270 degrees bending magnet upstream of the x-ray production target. The resulting bremsstrahlung beam passes through a combination steel and lead flattening filter, 4-cm maximum thickness. Dosimetric data for the 23-MV beam are presented with respect to rectangular field output factor, depth of maximum dose as a function of field size, surface and buildup dose, central axis percent depth dose, tissue-phantom ratios, beam profile, applicability of inverse square, and block transmission. Some data are also presented on the effect of different flattening filter designs on apparent beam energy.

Output factor constituents of a high-energy photon beam

Measurements designed to separate primary and various scatter components of central axis dose of the highest energy photon beam of the CGR Saturne 25 linear accelerator are described. This beam has an unusually large output variation with field size. The measurements are performed both in air and in a water phantom, with and without an aperture external to the collimator system. Results are presented in the form of relative output factors for different field sizes due to (i) flattening filter scatter, (ii) water phantom scatter, (iii) collimator backscatter into the monitor chamber, and (iv) collimator forward scatter onto the central axis. It is found that the flattening filter is the single largest scatter component, but that each of the other factors is significant in determining the output dose per monitor unit as a function of field size.

Interstitial radiotherapy combined with interstitial hyperthermia in the management of recurrent tumors

During a 2-year period 31 sites in 27 patients with recurrent, previously treated tumors received a combination of interstitial 192Ir radiation (RT) with microwave hyperthermia (HT). Head and neck sites were treated most frequently (48%), with breast and vagina each representing about 20% of sites. Complete response (CR) with no local recurrence was obtained in 61%, partial response (PR) in 11 (36%), and one (3%) had less than 50% tumor regression. Of these patients, nine had no evidence of tumor following HT-RT therapy, 8/18 in the CR group and 1/11 in the PR group. Significant factors influencing CR were: radiation dose, tumor volume and duration of tumor control following the initial therapy (p less than 0.02). Treated site, histology and thermal dose were not significant factors influencing tumor regression. Complications of significance developed in one patient who had local skin necrosis. Interstitial HT-RT combination provides an effective palliative therapy for recurrent and/or persistent tumors. Randomized trials are necessary to assess the effectiveness of this combination as a component part of primary management of selected tumors.

Treatment results and patterns of failure in 646 patients with carcinoma of the eyelids, pinna, and nose

From 1956 to 1978, 646 patients were treated with radiotherapy for carcinoma of the nose (350 patients, 54 percent), eyelids (159 patients, 25 percent), pinna (93 patients, 14 percent), and skin adjacent to the lip (44 patients, 7 percent). The histologic distribution was 72 percent basal cell carcinoma, 18 percent squamous cell carcinoma, and 10 percent mixed basal and squamous cell features. Tumors less than 2 cm in diameter were found in 602 patients (93 percent), whereas 44 patients (7 percent) had larger tumors. Tumor involvement of cartilage and bone was seen in 23 patients at the time of diagnosis. The 5, 10, and 20 year control rates were 99 percent, 98 percent, and 98 percent, respectively, for 502 tumors less than 2 cm in diameter. This compared favorably with control rates of 92 percent at 5 years and 79 percent at 10 years for tumors from 2 to 5 cm in diameter and 60 percent at 5 years and 53 percent at 8 years for 12 patients with massive tumors (p less than 0.0001). The histologic characteristics of the lesion had a strong influence on tumor control (p less than 0.02). Of the patients with cartilage or bone invasion, tumor was controlled in 19 (83 percent). Of these 19 patients, 11 had no evidence of disease for 3 years or more. Of all 646 patients treated, failure was seen in 60 (9 percent). It correlated well with the size of the lesion, being 7 percent for tumors of less than 2 cm and 50 percent for tumors of greater than 5 cm. Of the 60 patients in whom treatment failed, 48 (80 percent) had prior definitive therapy. Radiotherapy was an efficient modality to control operative failures; however, it was not as efficient at control in patients in whom previous radiotherapy failed. Operation was the treatment of choice to salvage patients in whom radiotherapy failed. Of the patients in whom retreatment failed, 10 were known to have died from skin cancer, and an additional 6 patients were presumed to have died from the cancer. This study has demonstrated a good control rate and good cosmetic results for small tumors of the eyelids, pinna, and nose. In addition, a good control rate was obtained in patients with cartilage and bone involvement. Treatment of massive tumors should involve planned operative resection with adjuvant radiotherapy.

A 500 KHz localized current field hyperthermia system for use with ophthalmic plaque radiotherapy

Ophthalmic plaque radiotherapy has been demonstrated to be a useful alternative to enucleation in the treatment of small choroidal melanomas. The prognosis for tumours larger than 8 mm in height, however, continues to be poor. Treatment complications limit the radiation dose which may be delivered to these larger tumours. Hyperthermia has been shown to enhance the effectiveness of radiotherapy for many tumours, particularly malignant melanoma. The use of hyperthermia in conjunction with plaque radiotherapy may improve local tumour control for larger choroidal melanomas, allowing patients to maintain useful vision. We have developed an instrument which enables the combination of localized current field hyperthermia with radiotherapy using an episcleral plaque. The system is simple and inexpensive. We have measured temperature distributions in tissue-like phantoms, in excised bovine eyes, and in vivo in normal rabbits. In each of the cases studied, temperature varied by less than 1 degree C within 3 mm of, and across the concave surface of the plaque. At distances greater than 3 mm, the temperature gradient was approximately -0.3 degree C per millimetre.

Interstitial radiobrachytherapy of malignant cerebral neoplasms: rationale, methodology, prospects

The local use of radionuclides in the management of neoplastic processes was initially considered over 80 yr ago and has enjoyed increasing enthusiasm in the treatment of somatic and central nervous system tumours during the past 30 yr. The marriage of complex neuroimaging techniques and modern stereotactic devices has markedly enhanced the technical precision of interstitial radiobrachytherapy of malignant cerebral neoplasms. In applying these techniques, it is imperative to achieve an optimal placement of radionuclide sources in order to develop a geometrically homogenous, controlled distribution of radiation. Critical considerations include determination of tumour volume and contour, and development of a homogenous dose rate (dependent upon multiple sources at varying intensity) that will not only effect tumour cell kill but do this without excessive production of radionecrosis which necessitates craniotomy because of mass. Using the Brown-Roberts-Wells (BRW) stereotactic guidance system and an image-defined, volumetrically determined target, implants of multiple iridium 192(192Ir) sources were used to establish appropriate isodose envelopes. A methodology for achieving the described objectives is detailed as it applies to a variety of malignant intracerebral neoplasms (glioblastoma multiforme, malignant astrocytoma, malignant mixed glioma, primary cerebral lymphoma, metastatic carcinoma and malignant pineal region tumours). Technical realization of precision implantation relying upon imaging data may be acheived with this method with satisfactory responses that are dependent upon histological tumour type and the morphology of the tumour distribution as related to the image. Early and late complications related to the surgical technique and radionuclide applications were less than 5%. Although encouraging, these techniques require further definition and greater data accrual before uniform application outside major medical centres can be justified. It is anticipated that improvement in results with intrinsic gliomas and other invasive neoplasms will be realized with further definition of tumour boundaries by tract biopsy techniques and concurrent utilization of hyperthermia and brain protective methods.

Carcinoma of the lip and selected sites of head and neck skin. A clinical study of 896 patients

During a period of over 20 years, 896 patients were treated with radiation in Wadsworth Medical Center, Los Angeles, for carcinoma of the lip and selected sites of skin of the head and neck. Basal cell carcinoma (BCC) was found in 467 (52%) patients, squamous cell carcinoma (SCC) in 362 (40%), and the remaining 67 (8%) had tumors with mixed basal and squamous cell features. BCC was the most common tumor (72%) among the 646 skin cancer patients while SCC predominated (99%) among the 250 lip cancer patients. Tumor control correlated well with the size of the lesion, p less than 0.0001. Histology of the lesion also had a significant (p = 0.021) influence on the tumor control rate, which was the highest among the BCC patients when compared with SCC or mixed cell patients. This study has again demonstrated the effectiveness of radiotherapy in controlling small and intermediate size epithelial tumors of the skin and lip. Additionally, irradiation, if administered properly, results in excellent cosmesis and a low incidence of treatment complications. Severe complications of radiotherapy reported in the literature took place at the beginning of this century and are no longer pertinent in the practice of modern radiation oncology. Larger lesions remain a challenge to radiation or surgical dermato-oncologists. A lack of tumor control in such lesions frequently results in a death of patient.

Initial performance of the Stanford Medical pion generator

A novel, cylindrical geometry, superconducting pion channel has been constructed at Stanford. It can simultaneously deliver up to 60 radially converging pion beams of the same mean momentum but with individually variable momentum spread (0.0-4.3%). Virtually no tuning of the pion beam is required Preliminary tests have demonstrated many of the performance characteristics which facilitate the treatment of selected human tumors.