International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1992
Comparative StudyPulsed brachytherapy: the conditions for no significant loss of therapeutic ratio compared with traditional low dose rate brachytherapy.
Pulsed brachytherapy consists of using a stronger radiation source than for traditional low dose-rate brachytherapy, but giving a series of short exposures of 10 to 30 min in every hour, to approximately the same total dose in the same overall time as with the low dose-rate. Calculations based on the linear quadratic model, in which the beta x dose squared component only is assumed to be repairable, and at a monoexponential rate, show that there is no significant loss of therapeutic ratio, defined as tumor damage for a given level of late damage. Some loss of therapeutic ratio would in principle be expected when dose rates are increased, but, in the presently proposed applications, there are so many small pulses (fractions at medium or low dose-rate) that even though repair is not usually complete between them, the relative increase of late damage (in units proportional to log cell kill) is less than 10% more than the increase of tumor damage, except in unlikely conditions that we define. Although these calculations suggest that pulsed brachytherapy should be safe for pulse repetition frequencies up to about 2 hr, using dose rates not exceeding about 3 Gy/hr, we discuss the radiobiological reservations and the limitations of such calculations.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1992
Breast recurrence and survival related to primary tumor location in patients undergoing conservative surgery and radiation for early-stage breast cancer.
Between 1977 and 1986, 886 pts with Stage I and II breast cancer underwent excisional biopsy, axillary dissection and radiation. Median follow-up was 5 years (range 2 months-13 years). The patients were divided into four groups according to the primary tumor location: 1) outer (495 patients), 2) inner (202 patients), 3) central (119 patients), and 4) subareolar (70 patients). ⋯ For node-positive patients, the 5 year actuarial overall survival was 87% vs 82% vs 84% vs 90% (p = .59), relapse-free survival was 69% vs 66% vs 77% vs 80% (p = .78), and NED survival was 75% vs 68% vs 85% vs 80% (p = .66). Patterns of first failure were also not significantly different among the four groups: local only first failure (7% vs 4% vs 5% vs 8%, p = .49), any local first failure, i.e., +/- simultaneous distant metastases (8% vs 5% vs 5% vs 9%, p = .61), regional only (2% vs 1% 1% vs 0%, p = .65), any regional (4% vs 3% vs 3% vs 3%), or distant metastases (11% vs 17% vs 9% vs 10%, p = .16). A separate analysis of node negative and node positive patients revealed similar findings.(ABSTRACT TRUNCATED AT 400 WORDS)
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1992
Interstitial brachytherapy for newly diagnosed patients with malignant gliomas: the UCSF experience.
Although interstitial brachytherapy appears to be effective in treating recurrent malignant gliomas, it has been studied less extensively in patients with newly diagnosed tumors. To examine the effect of this treatment when used at the time of primary diagnosis, we retrospectively reviewed the records of 88 patients who received temporary interstitial implants of 125I for newly diagnosed malignant gliomas. This brachytherapy was preceded by a course of external radiation therapy and followed, in some cases, by chemotherapy. ⋯ Our results support the conclusion that interstitial brachytherapy used at the primary diagnosis lengthens survival in selected patients with glioblastoma multiforme. However, the toxicity is significant in terms of the need for surgical resection of symptomatic necrosis. In patients with anaplastic gliomas, the toxicity associated with the treatment probably outweighs its advantages.
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Long-term data on the management of early breast cancer in Australia by conservative surgery and radiation therapy is limited. To examine this issue we reviewed our experience of 131 patients with Stage I or II breast cancer treated between November 1979 and December 1985. Ninety patients had a T1 tumor and 41 a T2 tumor. ⋯ The treatment of the axilla by both surgery plus radiation therapy was associated with a moderate or severe arm edema rate of 29% compared to 8% for surgery alone and 6% for radiation therapy alone. Our long-term data indicate that conservative surgery plus radiation therapy is associated with low rates of breast cancer recurrence which are independent of the extent of surgical resection. Complications were acceptably low provided that the axilla was treated by surgery or radiation therapy but not by both modalities.