Biomedical subjects

Alan T Monroe

Publications and source records attributed to Alan T Monroe.

5 recordsLinked to original sources

PubMed2005

Does altered fractionation influence the risk of radiation-induced optic neuropathy?

PURPOSE: To analyze the parameters that influence the risk of radiation-induced optic neuropathy (RION) after radiotherapy for head-and-neck tumors. METHODS AND MATERIALS: Between 1964 and 2000, 273 patients with tumors of the nasopharynx, paranasal sinuses, nasal cavity, and hard palate adenoid cystic carcinomas were treated with curative intent and had radiation fields that included the optic nerves and/or chiasm. Patients were followed for at least 1 year after radiotherapy. RESULTS: Radiation-induced optic neuropathy developed in 32 eyes of 24 patients (9%). The 5-year rates of freedom from RION according to the total dose and once- vs. twice-daily fractionation were as follows: < or =63 Gy once daily, 95%; < or =63 Gy twice daily, 98%; >63 Gy once daily, 78%; and >63 Gy twice daily, 91%. Multivariate analysis revealed that the total dose affected the risk of RION (p = 0.0047), with patient age (p = 0.0909), once-daily vs. twice-daily fractionation (p = 0.0684), and overall treatment time (p = 0.0972) were marginally significant. The use of adjuvant chemotherapy did not significantly influence the likelihood of developing RION. CONCLUSION: The likelihood of developing RION is primarily influenced by the total dose. Hyperfractionation may reduce the risk of experiencing this complication.

Adrenal Cortex Hormones↗

PubMed2005

Preventing radiation retinopathy with hyperfractionation.

PURPOSE: The purpose of this study was to determine factors associated with the development of radiation retinopathy in a large series of patients with head-and-neck cancer. In particular, we addressed whether the use of hyperfractionated radiation therapy was effective in reducing the risk of retinopathy. METHODS AND MATERIALS: One hundred eighty-six patients received a significant dose to the retina as part of curative radiotherapy. Primary sites included: nasopharynx, 46; paranasal sinus, 64; nasal cavity, 69; and palate, 7. Prescription doses varied depending on primary site and histology. Hyperfractionated (twice-daily) radiation was delivered to 42% of the patients in this study, typically at 1.10 to 1.20 Gy per fraction. The remainder were treated once-daily. Retinal doses were determined from computerized dosimetry plans when available. For all other patients, retinal doses were retrospectively calculated using reconstructed off-axis dosimetry taken from contours through the center of the globes. Retinal dose was defined as the minimum dose received by at least 25% of the globe. The median retinal dose was 56.85 Gy. Patients were followed for a median of 7.6 years. RESULTS: Thirty-one eyes in 30 patients developed radiation retinopathy, resulting in monocular blindness in 25, bilateral blindness in 1, and decreased visual acuity in 4. The median time to the diagnosis of retinopathy was 2.6 years (range, 11 months to 5.3 years). The actuarial incidence of developing radiation retinopathy was 20% at both 5 and 10 years. The incidence of developing ipsilateral blindness due to retinopathy was 16% at 5 years and 17% at 10 years. Site-specific incidences varied considerably, with ethmoid sinus (9 of 25, 36%), nasal cavity (13 of 69, 19%), and maxillary sinus (6 of 35, 17%) being the most common sites associated with radiation retinopathy. Three of 72 patients (4%) receiving retinal doses less than 50 Gy developed retinopathy. Higher retinal doses resulted in a steady increase in the incidence of retinopathy, with 25 of the 30 cases occurring after 60 Gy or more. Of the patients receiving more than 50 Gy to the retina, hyperfractionation was associated with a significantly lower incidence of radiation retinopathy (37% vs. 13%; p = 0.0037). On multivariate analysis, retinal dose (p < 0.0001), fractionation schedule (p = 0.0003), age (p = 0.0365), and prolonged overall treatment time (p = 0.0213) were significant predictors of radiation retinopathy. CONCLUSION: The incidence of ipsilateral radiation retinopathy after treatment of nasal cavity/paranasal tumors is 20% at 5 and 10 years. Retinal dose and fractionation schedule are the strongest predictors of retinopathy. Hyperfractionated radiotherapy is associated with a significant reduction in the incidence of radiation retinopathy, especially when the retina receives more than 50 Gy.

Adolescent↗

PubMed2004

Tracheobronchial amyloidosis: a case report of successful treatment with external beam radiation therapy.

Tracheobronchial amyloidosis (TBA) refers to the deposition of localized amyloid deposits within the upper airways. Treatments have historically focused on bronchoscopic techniques including debridement, laser ablation, balloon dilation, and stent placement. Local excisions often prove temporarily effective, with multiple local recurrences and progressive compromise pulmonary function occurring frequently. We present a case of TBA managed with definitive external beam radiation therapy. Eighteen months after moderate-dose radiation, the patient demonstrated improvements in functional status, pulmonary function, bronchoscopic visualization, and CT-based luminal diameters. The literature involving the role of radiation therapy in the treatment of TBA is reviewed.

Amyloidosis↗

PubMed2003

Angiosarcoma after breast-conserving therapy.

BACKGROUND: Angiosarcoma arising in the irradiated breast after breast-conserving therapy is being reported with increasing frequency. As more women undergo breast-conserving therapy, the incidence can be expected to increase. Surgeons, medical oncologists, and radiation oncologists will be faced with difficult management decisions for this aggressive disease. METHODS: A comprehensive review of all English-language reports of angiosarcomas after breast-conserving therapy was performed. Approximately 100 cases were reviewed for treatment details and outcome analysis was performed. RESULTS: Surgical excision is associated with very high rates of disease recurrence (55 of 75 patients with at least 1 year of follow-up; 73%). Local disease recurrences in the tumor bed or along the mastectomy scar are a component of almost all recurrences (96%). Distant metastases develop simultaneously or shortly after local recurrences. Hyperfractionated radiotherapy has successfully prevented local disease recurrences in a limited number of patients. CONCLUSIONS: Angiosarcoma after breast-conserving therapy is increasingly diagnosed in a small but significant portion of breast carcinoma survivors. The aggressive nature of this disease demands further investigation of adjuvant therapy to prevent recurrence of disease after surgery.

Aged↗

PubMed2003

Radiation therapy for esthesioneuroblastoma: rationale for elective neck irradiation.

PURPOSE: Esthesioneuroblastoma is an uncommon malignancy of neural crest origin arising in the upper nasal cavity. We describe the University of Florida experience using radiation therapy (RT) in the treatment of this neoplasm, particularly the use of elective nodal irradiation. MATERIALS AND METHODS: Between May 1972 and August 1998, 22 patients received RT for esthesioneuroblastoma. Two additional patients were treated with palliative intent and were excluded from analysis. Equal numbers of male and female patients were treated, with a median age of 54 years (range, 3-82). The modified Kadish stage was A in 1 patient, B in 4 patients, C in 15 patients, and D in 2 patients. Treatment modalities included primary RT in 6 patients, preoperative RT in 1 patient, postoperative RT after craniofacial resection in 12 patients, and salvage RT in 3 patients treated for recurrence after surgery. Elective neck RT was performed in 11 of 20 patients; 2 patients had cervical metastases at presentation for RT. RESULTS: Rates of local control, cause-specific survival, and absolute survival at 5 years were 59%, 54%, and 48%, respectively. The cause-specific survival rate at 5 years was lower after primary RT (17%) than after craniofacial resection and postoperative RT (56%). Cervical metastases occurred in 6 of 22 patients (27%). No neck recurrences occurred in 11 patients treated with elective neck RT compared with 4 neck recurrences in 9 patients (44%) not receiving elective neck RT (p =.02). CONCLUSIONS: Combined modality therapy is preferred over RT alone in advanced-stage esthesioneuroblastoma. Our data and review of the current literature suggest a higher cervical failure rate than previously recognized. Elective neck RT seems to correlate with improved nodal control and should be considered in the treatment of esthesioneuroblastoma.

Adolescent↗