International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 1997
Clinical TrialPulsed low dose rate brachytherapy for pelvic malignancies.
The pulsed low dose rate remote afterloading unit was designed to combine the radiation safety and isodose optimization advantages of high dose rate technology with the radiobiologic advantages of continuous low dose rate brachytherapy. This is the first report of a prospective clinical trial evaluating the relative incidence of acute toxicity and local control in patients with pelvic malignancies who underwent interstitial or intracavitary brachytherapy with the pulsed low dose rate remote afterloader. ⋯ Using the parameters described for this initial clinical study in patients treated for pelvic malignancies, pulsed low dose rate brachytherapy shows no significant increase in acute toxicity above that seen with the standard continuous low dose rate approach. Using the isodose optimization possible with pulsed brachytherapy, local control is excellent in patients treated at initial presentation, although longer follow-up is required for full assessment of local control and late toxicity. Further trials will need to be carried out to determine if larger doses per pulse and shorter total treatment times have comparable therapeutic ratios.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 1997
Metastatic carcinoma in the cervical lymph nodes from an unknown primary site: results of bilateral neck plus mucosal irradiation vs. ipsilateral neck irradiation.
To compare the outcome for patients with squamous cell carcinoma of cervical lymph nodes metastatic from an unknown primary site who were irradiated to both sides of the neck and potential mucosal sites with opposed photon beams, and for those irradiated to the ipsilateral side of the neck alone with an electron beam. ⋯ Bilateral neck and mucosal irradiation is superior to ipsilateral neck irradiation in preventing contralateral cervical lymph node metastases and the subsequent appearance of an occult primary cancer. Both techniques combined with cervical lymph node dissection were equally effective in controlling the ipsilateral neck disease.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 1997
Biological effect of pulsed dose rate brachytherapy with stepping sources if short half-times of repair are present in tissues.
To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR) for local tissue dose rates between those "averaged over the whole pulse" and the instantaneous high dose rates close to the dwell positions. Increased effect is more likely for tissues with short half-times of repair of the order of a few minutes, similar to pulse durations. ⋯ Therefore, about 75% of the total dose is delivered at HDR in a PDR implant of moderate volume, reducing to 40% as the source decays from 1 to 0.3 curies. Even so, restricting the dose per pulse to 0.5 or 0.6 Gy should avoid ratios of increased effect larger than about 10%. It appears likely that PDR delivered by stepping source might behave more like HDR than LDR, especially for tissues with a substantial component of repair of very short T1/2.