Recovery of spermatogenesis after treatment for Hodgkin's disease: limiting dose of MOPP chemotherapy.

The sperm production of 25 patients with Hodgkin's disease treated with mechlorethamine, vincristine, procarbazine, and prednisone (MOPP) chemotherapy was studied retrospectively. All but two patients also received radiotherapy treatment to pelvic and/or non-pelvic fields. Sperm counts were obtained from patients treated either with three or fewer (MOPP-2 group) or with five or more (MOPP-6 group) chemotherapy cycles. Recovery of spermatogenesis following treatment-induced azoospermia was significantly higher among the MOPP-2 patients (Mann-Whitney rank sum test, p = 0.001). Patients in this group who did not receive pelvic irradiation appeared to have greater recovery rates (p = 0.06). The results suggest that three cycles of MOPP chemotherapy represent a maximum exposure compatible with the recovery of spermatogenesis.

Utilization of thermoluminescent dosimetry in total skin electron beam radiotherapy of mycosis fungoides.

PURPOSE: The purpose of this report is to discuss the utilization of thermoluminescent dosimetry (TLD) in total skin electron beam (TSEB) radiotherapy to: (a) compare patient dose distributions for similar techniques on different machines, (b) confirm beam calibration and monitor unit calculations, (c) provide data for making clinical decisions, and (d) study reasons for variations in individual dose readings. METHODS AND MATERIALS: We report dosimetric results for 72 cases of mycosis fungoides, using similar irradiation techniques on two different linear accelerators. All patients were treated using a modified Stanford 6-field technique. In vivo TLD was done on all patients, and the data for all patients treated on both machines was collected into a database for analysis. Means and standard deviations (SDs) were computed for all locations. Scatter plots of doses vs. height, weight, and obesity index were generated, and correlation coefficients with these variables were computed. RESULTS: The TLD results show that our current TSEB implementation is dosimetrically equivalent to the previous implementation, and that our beam calibration technique and monitor unit calculation is accurate. Correlations with obesity index were significant at several sites. Individual TLD results allow us to customize the boost treatment for each patient, in addition to revealing patient positioning problems and/or systematic variations in dose caused by patient variability. The data agree well with previously published TLD results for similar TSEB techniques. CONCLUSION: TLD is an important part of the treatment planning and quality assurance programs for TSEB, and routine use of TLD measurements for TSEB is recommended.

Endocrine profiles of patients with testicular tumors treated with radiotherapy.

Blood samples for hormone analysis were obtained 5 to 20 years post-therapy from 12 men with testicular tumors who were originally treated by unilateral orchiectomy followed by abdominal and/or pelvic irradiation. In nine patients (75%) the levels of FSH and LH, and in one patient (8%) the testosterone values, were outside the ranges found in age- and sex-matched controls. From this retrospective study we conclude that, even when the remaining testis is kept outside the field of radiation, significant radiation damage occurs, mainly through scatter. This damage is more likely to occur if the hemiscrotum is irradiated. Methods of shielding are available to reduce the dose received by the contralateral testis.

Radiotherapy during pregnancy for clinical stages IA-IIA Hodgkin's disease.

Between 1956 and 1990, 775 women were treated for Hodgkin's disease at The University of Texas M.D. Anderson Cancer Center. Of these, 25 (3.2%) were pregnant at diagnosis. Seven of these women were in the first trimester, 10 in the second, and eight in the third. Prior to treatment, three women in the third trimester had normal deliveries, and six patients in the first trimester had abortions. Sixteen patients received radiotherapy for supradiaphragmatic presentations during their pregnancies. All these patients had nodular sclerosing Hodgkin's disease: Two had clinical stage IA presentations and 14 had clinical stage IIA. In two patients radiotherapy (35 Gy) was limited to the neck, three patients were treated definitively to the neck and mediastinum (40 Gy), and 11 patients received mantle irradiation (40 Gy). Four to five half-value layers of lead were used to shield the uterus during radiotherapy. The dose to the fetus was estimated individually in nine patients, using a combination of an Alderson-Rando and a water phantom. The estimated total dose to the mid-fetus ranged from 1.4 to 5.5 cGy for treatment with 6 MV photons, and from 10 to 13.6 cGy for Cobalt 60. All 16 patients subsequently delivered full-term, normal infants. Following delivery, all of the patients had further staging procedures; eight received additional treatment. Subsequently, the disease relapsed in four patients; two eventually died of Hodgkin's disease. The 10-year determinant and overall survival rates were 83% and 71%, respectively. Currently, all offspring are physically and mentally normal, and none has developed a malignancy. Radiotherapy is an appropriate initial treatment for supradiaphragmatic presentations of Hodgkin's disease during the second and third trimesters of pregnancy, provided special attention is paid to treatment and shielding techniques. The outcome for women treated with irradiation for clinical stage I and II Hodgkin's disease during pregnancy has not been shown to be adversely affected by pregnancy, and after the first 8 weeks of gestation, the risk to the fetus appears to be minimal.

Postirradiation sarcomas in Sprague-Dawley rats.

A series of radiation-induced neoplasms occurred in Sprague-Dawley rats 4-8 months after irradiation of a single hind leg with 60Co gamma rays. The rats were exposed to fractionated cumulative doses that ranged from 0 to 106 Gy. Osteosarcomas, malignant fibrous histiocytomas and fibrosarcomas developed in the radiation fields of a number of the rats in the higher-dose groups. Tumors did not develop throughout an 8-month observation period in rats that received doses of only 0 or 46 Gy. The most common postirradiation sarcomas in humans are osteosarcoma, malignant fibrous histiocytoma and fibrosarcoma. The Sprague-Dawley rat may serve as a good animal model in studying the development of sarcoma in humans after regional radiotherapy.

Calibration in water versus calibration in air for cobalt-60 gamma rays.

In the United States it is common practice to calibrate Cobalt-60 teletherapy machines "in air," despite recommendations by the International Commission on Radiation Units and Measurements (ICRU) and other organizations that calibration be accomplished by measurement at 5-cm depth in a water phantom. A comparison has been made between the results of ionization measurements in air at 80.5-cm distance from the source and in water at 80-cm source-skin distance (SSD) for the determination of absorbed dose at three depth (5, 10, and 15 cm) for each of three fields sizes (6 X 6, 10 X 10, and 20 X 20 cm2), for a total of 42 Cobalt-60 machines. The mean of the ratio, absorbed dose from in-water measurements to absorbed dose at the same depth calculated from in-air measurements, ranged frt 5-cm depth for a 20 X 20-cm2 field size. Reasons for the differences are offered, and compliance with ICRU recommendations is suggested.

A review of the reliability of chamber factors used clinically in the United States (1968--1976).

One of the principal concerns of a physicist responsible for calibrating megavoltage radiotherapy equipment is the validity and stability of the 60Co exposure correction factor assigned to his ionization-chamber and electrometer system. It is the practice of the AAPM Radiological Physics Center (RPC) to perform an intercomparison between the RPC chamber and electrometer system and the chamber and electrometer in use at each of the various institutions visited by the RPC. The results of 202 such intercomparisons are reviewed to determine (1) the consistency in the assignment of exposure correction factors by a calibrating agency with itself and with other calibrating agencies, and (2) the dependence of the reliability of the exposure correction factors upon the type of field instrument and the time since calibration.

Dose enhancement from backscattered radiation at tissue-metal interfaces irradiated with high energy electrons.

Irradiation of a tissue-metal interface with 13 MeV to 20 MeV electrons results in an increased dose to the tissue on the entrance side of the metal. Ionization measurements were made with a thin-window parallel-plate chamber to determine the magnitude of the dose enhancement as a function of incident electron energy, thickness and atomic number of metals introduced into the electron beam. The presence of a metal resulted in a dose ranging from 6% to approximately 50% greater than that measured with no metal in the beam. Most of this increase in dose may be eliminated by the addition of 1-2 g/cm2 of low Z material between tissue and metal.

Use of auxiliary collimating devices in the treatment for breast cancer with 60Co teletherapy units. I. Dosimetric considerations.

The dosimetry of tangential field treatment for breast cancer using an auxiliary collimating device on 60Co teletherapy machines is reviewed. The position of the device with respect to the source axis has negligible effect on either the dose rate or the dose distribution. Measurements with thermoluminescent dosimeters in an anatomic phantom verify the accuracy of the method of correction of isodose distributions for sloping skin. Possible systematic errors in dosimetry are identified.

Directional dependence of radiation fluence from 192Ir and 198Au sources.

Radiation fluence distribution around 192Ir and 198Au seeds of the type used for brachytherapy application was measured using a NaI crystal connected to a multi-channel analyzer. The radiation fluence, determined as a function of the angle between the seed axis and the direction of detection, is anisotropic with the fluence along the seed axis amounting to 78% of that perpendicular to the seed axis for seeds of both isotopes. The region of fluence reduction is broader for 198Au seeds, extending from 0-45 degrees; for 192Ir the decrease in fluence is evident for angles of 0-20 degrees. Integration of the angular distribution over 4 pi geometry indicated the effective activity of the implants to be 4% and 1% less than the nominal activity for the 198Au and 192Ir seeds, respectively, based on calibration measurements perpendicular to the seed axis.

Radiobiological considerations in the use of total-body irradiation for bone-marrow transplantation.

On radiobiological grounds, a therapeutic advantage should result when total body irradiation (TBI) in preparation for bone-marrow engraftment is given as a fractionated course, rather than as a single exposure at logistically reasonable dose rates. This is because cells of hemopoietic origin in general show less capacity for repair of sublethal radiation injury than do cells of other organs. Dose-limiting lung tolerance, in the context of fractionated TBI, is estimated to be at least 12 Gy (without correction) in increments of 2 Gy regardless of dose rate. A practical method for delivering TBI using a high-energy linear accelerator is described.