Radiotherapy for recurrent choroidal neovascularisation complicating age related macular degeneration.

AIMS: To report the safety and visual outcome data of external beam irradiation for recurrent choroidal neovascularisation complicating age related macular degeneration. METHODS: Eighteen consecutive eyes received external beam irradiation with seven fractions of 2 Gy (total dose 14 Gy). The next 16 consecutive eyes received external beam irradiation with five fractions of 3 Gy (total dose 15 Gy). Main outcome measure was change in visual acuity. Secondary outcome variables were contrast sensitivity and fundus photographic/fluorescein angiographic progression. RESULTS: The 3 Gy fraction group lost fewer lines of distance visual acuity at the three and six month follow up. At one year follow up, this difference was not maintained with 2 Gy fraction and 3 Gy fraction eyes. At one year follow up a decrease in visual acuity of three or more lines (moderate visual loss) occurred in 58% of 2 Gy and 42% of 3 Gy fraction eyes (p<0.36). At one year follow up a decrease in visual acuity of six or more lines (severe visual loss) occurred in 41% of 2 Gy eyes and 17% of 3 Gy eyes (p<0.23). At three months follow up, 3 Gy eyes were less likely (0%) than 2 Gy eyes (47%) to show moderate visual loss (p<0.003). However, Kaplan Meier curves estimate a significantly lower rate of severe visual loss in the 3 Gy group (p = 0.02). There were no significant differences in contrast sensitivity loss or fluorescein angiographic stabilisation rates. No evidence of radiation toxicity was observed. CONCLUSION: Our results are consistent with trends for a palliative benefit with higher fraction sizes and doses. The radiobiologic differences between low and high fraction size groups in this study are modest and correlate with the modest and short term difference in visual outcomes. These trends support further investigation of radiotherapy using fraction sizes of 4 Gy or higher.

Sham radiation in clinical trials assessing radiotherapy for exudative age-related macular degeneration.

BACKGROUND: To evaluate the effectiveness of sham radiation treatments in masking patients to their randomization group in the Radiation of Age-Related Macular Degeneration (ROARMD) Study. METHODS: Patients with choroidal neovascularization complicating age-related macular degeneration were randomized to a treatment (RAD) group that received external beam irradiation (seven treatment sessions) or to a control (SHAM) group that received sham radiation (one sham treatment session). During a telephone survey, 62 of 73 randomized patients responded to the following questions: Do you think you received radiation? Why do you feel that way? Did the vision in your study eye worsen after enrollment? RESULTS: Eighty-one percent of the RAD group and 59% of the SHAM group thought that they had received radiation. In patients who thought that their vision had stabilized or improved, 82% thought that they had received radiation. In patients who thought that their vision was worse, only 39% thought that they had received radiation. In 54% of patients, subjective perception of vision influenced their guess as to whether they received radiation. CONCLUSIONS: Subjective patient perception of visual outcome was the most influential variable for masking. Variation between radiation treatment and sham session techniques, such as equipment used and duration of treatments, played a lesser role in the masking of patients. Seven treatment days correlated with a higher number of patients who thought that they had received radiation. Although our procedures do not strictly mask the two groups, one sham radiation session was effective in keeping patients guessing their randomization group.

A new approach to film dosimetry for high energy photon beams: lateral scatter filtering.

A method of film dosimetry for high energy photon beams is proposed which reduces the required film calibration exposures to a set of films obtained for a small radiation field size and shallow depth (6 cm x 6 cm at 5 cm depth). It involves modification of a compression type polystyrene film phantom to include thin lead foils parallel to the vertical film plane at approximately 1 cm from both sides of the film emulsion. The foils act as high atomic number filters which remove low energy Compton scatter photons that otherwise would cause the film sensitivity to change with field size and depth. The proposed method is best described as "lateral scatter filtering." To validate the proposed method, central axis depth doses and isodose curves for a 4 MV photon beam were determined from films exposed within the modified phantom and the results compared with ionization chamber measurements. When no lateral filtering was used, for field sizes of 6 cm x 6 cm and 25 cm x 25 cm, this comparison demonstrated up to a 65% difference between film and ionization chamber central axis depth dose measurements. When using the lateral scatter filtering technique, less than a 4% difference was observed for these field sizes.

Ga-67 used to localize the tumor bed for radiation therapy after lumpectomy.

The authors present a new method to locate the tumor bed after lumpectomy. The method relies on accumulation of Ga-67 at the surgical site. This technique was useful in identifying the tumor bed in six candidates for breast conserving surgery and radiation therapy. This method may be applicable in other soft tissue malignancies that require postoperative radiation.

The effects of radiotherapy on the nasolacrimal system as evaluated by dacryoscintigraphy.

By utilizing 61 lacrimal scans, 26 patients who had received radiotherapy for inner canthus and lid lesions were evaluated. Results indicate that the membranous lacrimal passages are relatively immune to radiation therapy. Although dacryoscintigraphy did not delineate the anatomical features quite as well as contrast dacryocystography, it yielded very useful information about flow mechanisms and tear transit times. The study is rapid, simple, non-hazardous, and particularly helpful in documenting the status of the lacrimal drainage system before and after radiotherapy to the inner canthus region.