Ocular adnexal MALTomas: case series of patients treated with primary radiation.

BACKGROUND: Ocular adnexal mucosal-associated lymphoid tissue lymphomas (MALTomas) are rare, and there are no phase III trials to guide treatment. Primary radiation therapy has been the typical management. This retrospective series reports the experience of a single institution and adds to the current literature. METHODS: Our electronic medical record system and available paper charts were used to identify patients with MALTomas of the lacrimal gland or sac, conjunctiva, and orbital structures, including extraocular muscles. In order to determine pathology, staging, treatment information, local and distant control, salvage treatments, and late toxicity, records were reviewed. RESULTS: Sixteen patients with ocular adnexal MALTomas had local radiation between 1992 and 2011 for primary or recurrent disease. Fifty percent of patients had lymphoma in the conjunctiva, 25% had lymphoma in the lacrimal sac/gland, and 25% of patients had lymphoma in the posterior orbit. Stage IAE disease occurred in 75% of patients, 6% had stage IIAE disease, and 19% of patients had a positive bone marrow biopsy. One patient received chemotherapy as part of initial therapy. The median radiation dose was 30 Gy (25.5-36 Gy) delivered with electrons (31%) or photons (69%). After a mean follow-up of 62.8 months, 2 patients had residual/progressive disease, 2 had contralateral recurrence, and 1 patient had a distant failure, for local control of 87.5% and overall disease control of 68.75%. Recurrence/progression occurred at a median of 35.45 months. Two patients with residual/progressive disease and 1 patient with a contralateral recurrence were followed, successfully salvaged, and have no evidence of disease. Fourteen patients are still alive, and there were no disease-related/toxicity deaths. Seven patients developed cataracts in the treated eye, 2 patients had radiation retinopathy, 2 had permanent dry eye syndrome, and 1 patient had severe keratopathy requiring enucleation. Six patients (3.75%) had worsening visual acuity of unclear etiology. CONCLUSIONS: Primary radiation therapy for ocular adnexal MALTomas with a median dose of 30 Gy led to excellent local control. Patients who did recur were successfully salvaged. Radiation was generally well tolerated, with expected cataractogenesis, given the dose required to achieve local control (with only 1 patient developing severe keratopathy after receiving the highest dose in this series).

Mutations in the Bacillus subtilis beta clamp that separate its roles in DNA replication from mismatch repair.

The beta clamp is an essential replication sliding clamp required for processive DNA synthesis. The beta clamp is also critical for several additional aspects of DNA metabolism, including DNA mismatch repair (MMR). The dnaN5 allele of Bacillus subtilis encodes a mutant form of beta clamp containing the G73R substitution. Cells with the dnaN5 allele are temperature sensitive for growth due to a defect in DNA replication at 49 degrees C, and they show an increase in mutation frequency caused by a partial defect in MMR at permissive temperatures. We selected for intragenic suppressors of dnaN5 that rescued viability at 49 degrees C to determine if the DNA replication defect could be separated from the MMR defect. We isolated three intragenic suppressors of dnaN5 that restored growth at the nonpermissive temperature while maintaining an increase in mutation frequency. All three dnaN alleles encoded the G73R substitution along with one of three novel missense mutations. The missense mutations isolated were S22P, S181G, and E346K. Of these, S181G and E346K are located near the hydrophobic cleft of the beta clamp, a common site occupied by proteins that bind the beta clamp. Using several methods, we show that the increase in mutation frequency resulting from each dnaN allele is linked to a defect in MMR. Moreover, we found that S181G and E346K allowed growth at elevated temperatures and did not have an appreciable effect on mutation frequency when separated from G73R. Thus, we found that specific residue changes in the B. subtilis beta clamp separate the role of the beta clamp in DNA replication from its role in MMR.