David Neblett

Treatment of extensive carcinoma of the cervix with the “transperineal parametrial butterfly”

In advanced carcinoma of the cervix the associated obliteration of the fornices or contracture of the vagina may interfere with accurate placement of conventional intracavitary applicators. Poorly placed applicators fail to irradiate the pelvis homogeneously. Waterman (and others)10solved this dilemma by transvaginal radium implants many years ago; however, despite good survival figures, this technique has not gained popularity, presumably because of excessive exposure to personnel. In this paper, we describe a technique which largely eliminates the exposure problem and at the same time improves the homogeneity of pelvic endoradiotherapy. We locate what is in essence a pair of “paravaginal intterstitial colpostats” in both parametria in combination with the usual intrauterine randem. This helps to distribute the dose laterally, with relative sparing of bladder and rectum. The technique employs a template to guide the insertion into the parametria of a group of 18 gauge hollow steel needles transperineally. Afterloading with 192Ir is accomplished when the patient has returned to her room (after orthogonal radiography and computer dosimetry). Doses to point B compare very favorably to those at point A.

Iridium-192 afterloaded implant in the retreatment of head and neck cancers

Abstract Retreatment of persistent (or “recurrent”) carcinoma of the head and neck by means of after-loading 192Ir techniques may prove quite satisfactory. A total of 64 patients were retreated by these techniques from February, 1974 to October, 1975 at the Los Angeles County—University of Southern California Medical Center and the Southern California Cancer Center. Follow-up periods, averaging only 24 months (18 to 36 months), are too short for statistically significant evaluation of survival, but the “response rate” has been gratifying. Only 11 of our 64 patients (17%) have shown no satisfactory response to re-irradiation by interstitial implant. Thirty-one of the 64 patients (49%) have had local control with “good palliation”. Twenty-two of the 64 (34%) had at least 50% regression of tumour with “fair” palliation. Thus 83% have had satisfactory response to retreatment. A considerable number of these have survived to the date of this report. Whereas 36 of the 64 (56%) are now dead, 28 of the 64 otherwis...

Interstitial iodine-125 implant in the management of unresectable pancreatic carcinoma.

Eighteen patients with locally advanced adenocarcinoma of the head, body and tail of the pancreas were treated by a combination of biliary bypass, external and interstitial irradiation at Southern California Cancer Center of California Hospital Medical Center, Los Angeles, and Memorial Hospital Medical Center of Long Beach, Long Beach, CA, from July 31, 1975 to December 31, 1980. A dose of 3000 to 5000 rad was delivered to the pancreas and regional lymph nodes by external irradiation utilizing megavoltage units and 10,000 to 15,000 rad to the pancreas and metastatic lymph nodes by permanent Iodine‐125 implants. In this group of 18 patients with unresectable carcinoma of the pancreas, excellent palliation of pain, jaundice and vomiting was achieved, with a median survival of 14 months.

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.

Combination of external and interstitial irradiation in the primary management of breast carcinoma

The authors treated 83 patients with carcinoma of the breast using a combination of external and interstitial irradiation at Los Angeles County–University of Southern California Medical Center and Southern California Cancer Center between February 1, 1974, and May 31, 1977. All 30 patients who had T1 and T2 lesions, and who were followed for a minimum period of 24 months (24–50 months) are clinically still free of disease. Thirty‐nine of 53 patients with T3 and T4 lesions, who were followed for a minimum of 30 months (30–56 months) are still alive with local control. Details of treatment techniques, dosimetry, results and complications are presented.

Primary Treatment of Carcinoma of the Lower Rectum and Anal Canal by a Combination of External Irradiation and Interstitial Implant

Ten patients with carcinoma of the anorectum were treated with a combination of external irradiation and after-loading interstitial 192Ir implant, which seems to be effective in controlling relatively small cancers of the anorectum and providing effective palliation of extensive lesions. Five of the 10 patients remain free of tumor after a minimum follow-up of 15 months. Four of the 10 were treated with one interstitial implant and 4,000--5,000 rads of external irradiation and 6 were treated with the same amount of irradiation and two implants. When two implants were used, complications were minimal.

Initial brachytherapy in the breast conservation approach to breast cancer

The outcome of 100 consecutive newly diagnosed breast cancer patients treated between 1975 and 1985 within a protocol of planned segmental mastectomy and radiation therapy that included an initial brachytherapy boost is reported. Margins were not routinely inked in this study and the tumor bed was determined with the operating surgeon at the time of brachytherapy. There were 30 T1 tumors, 61 T2, and 9 T3. Segmental mastectomy was followed 2 weeks later by an interstitial implant with indium-192 sources given as initial boost dose to the tumor bed, at the time of axillary dissection. All patients received at least 20 Gy as boost dose followed by external beam radiation to a total dose of 45–50 Gy to the breast and regional nodes delivered over a period of 4–5 weeks. With a median follow-up of 7 years a total of 3 (3%) breast recurrences were detected (1/30 in Tl tumors, 2/61 in T2 tumors). Only one of the three recurrences was at the initial tumor bed. None of the nine T3 patients included in this series recurred locally. There were 4 severe complications (2 soft tissue necroses and 2 osteonecroses) occurring in 2/30 T1 and in 2/61 T2. Cosmetic results were good to excellent in 77% of the cases and fair to poor in 23%. The actuarial local control and survival probability rate were, respectively, 95% and 85% at 5 years and 93% and 73% at 10 years. Initial brachytherapy boost to a target volume accurately determined with the operating surgeon followed by subsequent external beam radiotherapy achieved excellent local control in the breast even for lesions larger than 2 cm (70% of the reported cases).

Biological doses with template distribution patterns

Consideration of radiation dose rate effects emphasizes advantages of the template method for lateral distribution of multiple sources in treatment of laterally infiltrating gynecologic cancer, when compared to a conventional technique with colpostats. Biological doses in time dose fractionation (TDF), ret and reu units are calculated for the two treatment methods. With the template method the lateral dose (point B) is raised without significantly increasing the doses to the rectum and bladder, that is, relatively, the calculated biological doses at point A and B are more nearly equivalent and the doses to the rectum and bladder are significantly lower than the dose to point B.

A dynamic wedge: use of a computer controlled dose distribution generation technique for simulation of wedge filters on a teletherapy treatment unit

Mechanical wedge filters currently used to shape teletherapy dose distributions are discrete blocks of metal specially designed to alter the geometry and characteristics of the dose distribution achieved by treatment beams. To provide an infinite number of wedge angles without filtering the treatment beam, a wedge shaped dose distribution is produced in a treatment volume by synchronizing the closing of the jaws of the collimator with the horizontal movement of the treatment couch. The dose rate, total dose delivered and positional information are fed to a computer which calculates and controls the movement of the treatment unit to produce variable wedge angles. Film dosimetry techniques are used to determine the dose distribution of the beam in a phantom. This work initiates a project aimed at producing dynamically shaped dose distributions that can be used in place of standard wedges and tissue compensators.