B Lally | PubMed Health

PubMed2000

Conjunctival melanoma: risk factors for recurrence, exenteration, metastasis, and death in 150 consecutive patients.

OBJECTIVE: To identify the risk factors of conjunctival malignant melanoma that predict local tumor recurrence, orbital exenteration, distant metastasis, and tumor-related mortality. DESIGN: The clinical parameters of the patient, tumor, and treatment were analyzed in a nonrandomized fashion for their relation to 4 main outcome measures using Cox proportional hazards regression models. PARTICIPANTS: One hundred fifty consecutive patients. MAIN OUTCOME MEASURES: Local tumor recurrence, orbital exenteration, distant metastasis, and death from conjunctival melanoma. RESULTS: The Kaplan-Meier estimates of local tumor recurrence was 26% at 5 years, 51% at 10 years, and 65% at 15 years. The mean number of recurrences per patient was 1 (median, 0 recurrences). There was no recurrence in 98 patients (65%), 1 recurrence in 28 patients (19%), 2 recurrences in 11 patients (7%), 3 recurrences in 5 patients (3%), and 4 or more recurrences in 8 patients (5%). Using multivariate analysis, the factors correlated with local tumor recurrence were melanoma location (not touching the limbus) (P =.01) and pathological tumor margins (lateral margin involved) (P =.02). Multivariate analysis for features correlated with ultimate exenteration included initial visual acuity (20/40 OU or worse) (P<. 001), melanoma color red (P =.01), and melanoma location (not touching the limbus) (P =.02). Tumor metastasis was present in 16% of patients at 5 years, 26% of patients at 10 years, and 32% of patients at 15 years. Metastasis was first located in the regional lymph nodes in 17 cases, the brain in 4 cases, the liver in 3 cases, the lung in 2 cases, and was disseminated in 1 case. The risks for metastases using multivariate analysis included pathological tumor margins (lateral margin involved) (P =.002) and melanoma location (not touching limbus) (P =.04). Tumor-related death occurred in 7% patients at 5 years' follow-up and 13% at 8 years' follow-up. The risk factors for death using multivariate analysis included initial symptoms (lump) (P =.004) and pathologic findings (de novo melanoma without primary acquired melanosis) (P =.05). The technique of initial surgery was shown to be an important factor in preventing eventual tumor recurrence (P =.07), metastasis (P =.03), and death (P =.006) in the univariate analysis, but did not reach significance in the multivariate analysis. CONCLUSIONS: Conjunctival malignant melanoma is a potentially deadly tumor. In the present study, metastasis was detected in 26% of patients, and death occurred in 13% of patients at 10 years. Extralimbal melanoma and tumor involvement of the surgical margins were especially poor prognostic factors. Meticulous surgical planning using wide microsurgical excisional biopsy working with the "no touch" technique and supplemental alcohol corneal epitheliectomy and conjunctival cryotherapy is advised. Arch Ophthalmol. 2000;118:1497-1507

Adolescent↗

PubMed1993

Characterization of a multi-leaf collimator system.

Commissioning measurements for a multi-leaf collimator installed on a dual energy accelerator with 6 and 15 MV photons are described. Detailed dosimetric characterization of the multi-leaf collimator is a requirement for modeling the collimator with treatment planning software. Measurements include a determination of the penumbra width, leaf transmission, between-leaf leakage, and localization of the leaf ends and sides. Standard radiographic film was used for the penumbra measurements, and separate experiments using radiochromic film and thermoluminescent dosimeters were performed to verify that distortions of the dose distribution at an edge due to changing energy sensitivity of silver bromide film are negligible. Films were analyzed with a scanning laser densitometer with a 210 micron spot. Little change in the penumbra edge distribution was noted for different positions of a leaf in the field. Experiments localizing the physical end of the leaves showed less than 1 mm deviation from the 50% decrement line. This small difference is attributed to the shaped end on the leaves. One side of a single leaf corresponded to the 50% decrement line, but the opposite face was aligned with a lower value. This difference is due to the tongue and groove used to decrease between-leaf leakage. For both energies, approximately 2% of photons incident on the multi-leaf collimator are transmitted and an additional 0.5% leakage occurs between the leaves. Alignment of the leaves to form a straight edge results in a penumbra profile which compares favorably with the standard technique of using alloy blocks. When the edge is stepped, the isodose lines follow the leaf pattern and the boundary is poorly defined compared to divergent blocks.

Equipment Design↗