Cancer incidence after retinoblastoma. Radiation dose and sarcoma risk

Responsiveness of human retinoblastoma and neuroblastoma models to a non-calcemic 19-nor Vitamin D analog

OBJECTIVES

To investigate the effectiveness of 2-methylene-19-nor-(20S)-1alpha-hydroxybishomopregnacalciferol (2MbisP) in inhibiting the growth of retinoblastoma (RB) and neuroblastoma (NB).

METHODS

For the RB study, the xenograft athymic mouse/human retinoblastoma cell (Y-79) model and the transgenic beta-luteinizing hormone-large T antigen (LHbeta-Tag) mice were systemically treated with 2MbisP or vehicle for 5 weeks. For the NB study, the xenograft athymic mouse/human neuroblastoma cell (SK-N-AS) model was treated with 2MbisP or vehicle for 5 weeks. Tumor size and toxicity were assessed.

RESULTS

In the xenograft models of RB and NB, 2MbisP caused statistically significant inhibition of tumor growth. Tumor growth inhibition was also observed in the transgenic RB mice, but did not achieve statistical significance. In all the groups, no biologically significant toxic effects were observed using the following variables: serum calcium levels, degree of kidney calcification, changes in body weight or survival.

CONCLUSIONS

In athymic mice, 2MbisP was effective in inhibiting RB and NB growth compared with controls. A lesser effect was seen in the transgenic RB model. 2MbisP did not cause hypercalcemia or a significant increase in mortality.

CLINICAL RELEVANCE

2MbisP should be considered for use in clinical trials of RB and NB.

Radiation exposure and familial aggregation of cancers as risk factors for colorectal cancer after radioiodine treatment for thyroid carcinoma

PURPOSE

In thyroid cancer patients, radioiodine treatment has been shown to be associated with an increased risk of colon carcinoma. The aim of this study in thyroid cancer patients was to evaluate the role of familial factors in the risk of colorectal cancer and their potential interaction with radioiodine exposure.

METHODS AND MATERIALS

We performed a case-control study on 15 colorectal cancer patients and 76 matched control subjects, nested in a cohort of 3708 thyroid cancer patients treated between 1933 and 1998. For each patient, the radiation dose delivered to the colon by radioiodine was estimated by use of standard tables. In those who received external radiation therapy, the average radiation doses delivered to the colon and rectum were estimated by use of DOS_Eg software. A complete familial history was obtained by face-to-face interviews, and a familial index was defined to evaluate the degree of familial aggregation.

RESULTS

The risk of colorectal cancer increased with familial aggregation of colorectal cancer (p = 0.02). After adjustment for the radiation dose delivered to the colon and rectum, the risk of colorectal cancer was 2.8-fold higher (95% CI, 1.0-8.0) for patients with at least one relative affected by colorectal cancer than for patients without such a family history (p = 0.05). The radiation dose delivered to the colon and rectum by (131)I and external radiation therapy was associated with an increase of risk near the significance threshold (p = 0.1). No significant interaction was found between radiation dose and having an affected relative (p = 0.9).

CONCLUSIONS

The role of familial background in the risk of colorectal cancer following a differentiated thyroid carcinoma appears to increase with the radiation dose delivered to the colon and rectum. However, the study population was small and no interaction was found between these two factors.

Radiation and breast cancer: a review of current evidence

This paper summarizes current knowledge on ionizing radiation-associated breast cancer in the context of established breast cancer risk factors, the radiation dose-response relationship, and modifiers of dose response, taking into account epidemiological studies and animal experiments. Available epidemiological data support a linear dose-response relationship down to doses as low as about 100 mSv. However, the magnitude of risk per unit dose depends strongly on when radiation exposure occurs: exposure before the age of 20 years carries the greatest risk. Other characteristics that may influence the magnitude of dose-specific risk include attained age (that is, age at observation for risk), age at first full-term birth, parity, and possibly a history of benign breast disease, exposure to radiation while pregnant, and genetic factors.

Causes of chemoreduction failure in retinoblastoma and analysis of associated factors leading to eventual treatment with external beam radiotherapy and enucleation

PURPOSE

To evaluate the causes of chemoreduction failure in retinoblastoma and to analyze the associated factors for eventual treatment with external beam radiotherapy and enucleation.

DESIGN

Prospective noncomparative case series.

PARTICIPANTS

Seventy-one patients with 105 eyes with intraocular retinoblastoma that underwent chemoreduction therapy between October 1998 and January 2003.

INTERVENTION

A 6-treatment cycle of chemoreduction therapy with vincristine, etoposide, and carboplatin was administered at monthly intervals. Unresponsive disease was defined as persistence of retinal tumors, vitreous seeds, or subretinal seeds after the second treatment cycle, with no appreciable sign of regression. Eyes with unresponsive disease were enucleated after the second treatment. Eyes that responded to chemoreduction therapy received focal treatment, including indirect laser photocoagulation, transpupillary thermotherapy, cryotherapy, and ruthenium 106 episcleral plaque radiotherapy after the second chemoreduction treatment, if necessary, to achieve complete tumor regression. Recurrence was defined as the regrowth of retinal tumors, vitreous or subretinal seeds after an initial favorable response, and regression. Recurrent retinal tumor, vitreous seeds, or subretinal seeds were treated with focal treatments and 2 to 3 additional chemoreduction treatments. When these methods failed or were not applicable, external beam radiotherapy and/or enucleation was administered.

MAIN OUTCOME MEASURES

The use of external beam radiotherapy and enucleation for chemoreduction failure, which was defined as unresponsive or recurrent disease.

RESULTS

The mean follow-up was 25.7 months (range: 6-49). Ten of 105 eyes (9.5%) with unresponsive disease were enucleated after the second treatment. Of the remaining 95 eyes, 42 (44.2%) developed recurrence after chemoreduction. Recurrent disease failing to be treated successfully by other methods was treated with external beam radiotherapy in 26 of 95 eyes (27.4%) and enucleation in 22 of 95 eyes (23.2%). External beam radiotherapy was successful in preventing enucleation in 20 of 26 eyes (76.9%). Overall, the globe salvage rate was 69.5%, ranging from 36.1% for Reese-Ellsworth group V disease to 87.0% for groups I to IV disease. Histopathologically, 29 of 31 enucleated eyes (93.5%) had poorly differentiated or moderately differentiated retinoblastoma. Using multivariate logistic regression analysis, factors predictive of eventual treatment with external beam radiotherapy were female gender (P = 0.010), presence of subretinal seeds (P = 0.023), and a greater number of chemoreduction treatments (P = 0.027). By multivariate analysis, the factors associated with the need for eventual treatment with enucleation were recurrence of retinal tumors (P = 0.004), presence of vitreous seeds (P = 0.008), greater tumor thickness (P = 0.015), presence of subretinal fluid (P = 0.040), and older patient age (P = 0.042).

CONCLUSIONS

Chemoreduction failure in this article was defined as unresponsive or, more commonly, recurrent retinoblastoma. Older patient age, greater tumor thickness, presence of vitreous seeds and subretinal fluid at baseline, and retinal tumor recurrence after chemoreduction were factors associated with the need for enucleation.

Causation of nervous system tumors in children: insights from traditional and genetically engineered animal models

Pediatric neurogenic tumors include primitive neuroectodermal tumors (PNETs), especially medulloblastoma; ependymomas and choroid plexus papillomas; astrocytomas; retinoblastoma; and sympathetic neuroblastoma. Meningiomas and nerve sheath tumors, although uncommon in childhood, are also significant because they can result from exposures of children to ionizing radiation. Specific chromosomal loci and specific genes are related to each of these tumor types. Virtually all these genes appear to act as tumor suppressor genes, which are inactivated in tumor cells by mutations or by chromosomal loss. In genetically engineered mice, some genes that are clearly associated with specific human tumors (e.g., RB1 in retinoblastoma and NF2 in meningiomas and schwannomas) have no such effect. Other genetic constructs in mice involving the genes p53, ptc1, and Nf1 have produced tumors remarkably similar to some of the human pediatric neoplasms. Some of these tumors become clinically apparent after only a few weeks, while the mice are still juveniles, especially when two or more tumor suppressor genes are inactivated in the same genetic construct. Conversely, at least one genetic pathway in rodents involving point mutation in the coding region of a transforming gene (neu in malignant schwannomas) does not appear to operate in any human tumors. The nervous system is markedly susceptible to experimental carcinogenesis during early life in rodents, dogs, primates, and other nonhuman species, and there is no obvious reason why this generalization should not also apply to humans. However, except for therapeutic ionizing radiation, no physical, chemical, or biological cause of human pediatric nervous system tumors is known. The failure of experimental transplacental carcinogenesis to mirror human pediatric experience more closely may reflect the need for multiple mutational events in target cells, and for experimental carcinogens that are capable of causing the full spectrum of mutations that occur in cancer-related genes in pediatric neurogenic tumors.

Children as a sensitive subpopulation for the risk assessment process

For cancer risk assessment purposes, it is necessary to consider how to incorporate sensitive subpopulations into the process to ensure that they are appropriately protected. Children represent one such potentially sensitive subpopulation that is of quite considerable magnitude. The data needs include sensitivity to the induction of childhood cancers compared to adult cancers and relative sensitivity of early-life exposures for the formation of tumors in adults. These needs as far as human data are concerned are best met for ionizing radiations, for which it has been shown in the atomic bomb survivors that early-life exposures are more effective at inducing cancers later in life. The risk assessment approach for ionizing radiations, however, is based on tumor data itself for total population exposures so that there is no requirement to consider specifically the impact of early-life exposures. In the case of environmental chemicals, the majority of the tumor data used for risk assessments are from rodent bioassays. There is a paucity of data that allow for a comparison of the response to early-life exposures compared to that for adult-only exposures. This presents a fairly difficult challenge to the identification of a general sensitivity factor or a chemical-specific sensitivity factor for early-life exposures. The U.S. Environmental Protection Agency (EPA) has not, until recently, incorporated a general adjustment for early-life exposure to carcinogens into its risk assessment guidelines. The Agency has relied on the fact that, in the absence of specific data to the contrary, the linear extrapolation for rodent tumor data provided appropriate protection. When specific data are available, then an adjustment can be calculated. In its most recent draft guidelines, however, a general adjustment has been proposed for mutagenic chemicals. A 10-fold risk adjustment is recommended for the first 2 years of life, a 3-fold adjustment for years 3-15, and no adjustment for exposures after age 15. For chemicals that do not have a mutagenic mode of action, no adjustment is recommended because the data for deriving such an adjustment are simply not available. Clearly, this is an interim position that is dependent on more pertinent data being collected. A significant component of this is to conduct cancer bioassays that include early-life exposures.

Nonocular Second Primary Tumors After Retinoblastoma

The objective of this study was to assess the role of various clinical and treatment factors involved in the long-term incidence of nonocular second primary tumors following retinoblastoma. The study was based on 111 patients treated between 1963 and 1977 according to the same radiotherapy protocol (electron beam radiotherapy) alone or in combination with triethylene melamine (TEM). Various statistical methods were used to obtain the actuarial survival curve, the cumulative incidence of second primary tumors, and comparisons of patient groups and subgroups. The 5-, 10-, 20-, and 30-year survival rates were 75%, 70%, 63%, and 55% with a follow-up of 23 to 35 years. The study reports the various parameters concerning 111 children and 17 second primary tumors: sex, age at treatment, histology of the retinoblastoma and second primary tumors, site of second tumors (anatomic and compared with irradiation field), radiation dose, time to onset, and chemotherapy with or without TEM. The results are discussed and compared with the data reported in the literature. Electron beam radiotherapy at a dose of 45 Gy does not eliminate the risk of nonocular second primary tumors. TEM also does not modify survival or the overall incidence of second primary tumors, but significantly increases the risk of second primary tumors outside the irradiation field.

Transpupillary thermotherapy as initial treatment for small intraocular retinoblastoma: technique and predictors of success

OBJECTIVE

To determine which small retinoblastoma tumors can be treated with transpupillary thermotherapy (TTT) alone and to clarify the minimum amount of treatment required to prevent recurrence.

DESIGN

Noncomparative interventional case series.

PARTICIPANTS

Ninety-one tumors in 22 eyes of 24 patients were treated with TTT as the primary treatment modality at a single institution from 1995 until 2002.

METHODS

Transpupillary thermotherapy was applied only when a tumor first appeared or if growth subsequently occurred. Treatment was performed while patients were under general anesthesia with the Iris diode laser (810 nm) on continuous mode with a 1.2-mm spot size.

MAIN OUTCOME MEASURES

Local tumor recurrence, failure of TTT requiring the use of salvage therapies.

RESULTS

Mean age at diagnosis was 3 months (range, 0-19 months), and mean initial tumor base was 0.67 disc diameters (DD) (range, 0.1-1.5). Eighty-four tumors (92%) were cured with TTT alone. Seven tumors (8%) required between 1 and 5 salvage treatments: 4 tumors received cryotherapy, 3 tumors received systemic chemotherapy, 2 tumors received external beam radiation, and 1 tumor received periocular chemotherapy. All 7 tumors requiring salvage treatment were cured without enucleation. Twenty-one eyes were preserved (95%), with 1 eye enucleated secondary to growth of other tumors. The mean number of treatment sessions required for cure was 1.7 (median, 1 session, range 1-6), with 64% of the tumors requiring only 1 session. The mean power was 420 mW, the mean total duration for all sessions was 320 seconds, and the mean total energy for all treatments was 139.6 J. Univariate analysis revealed that predictors of tumor recurrence were male gender, increasing age at diagnosis, posterior and inferior tumor location, increasing initial tumor base diameter, and increasing total energy. Multivariate analysis indicated that the predictive combination of variables included male gender, increasing age at diagnosis, and increasing total energy. The predictors of need for salvage treatment on univariate analysis were male gender, inferior tumor location, increasing initial tumor base diameter, and increasing total energy. Multivariate analysis demonstrated that the most important combination of variables was male gender and increasing total energy.

CONCLUSIONS

Retinoblastoma tumors <1.5 DD in base diameter can be successfully treated with TTT alone. Treatment can be implemented only when recurrences occur and can be used at low power settings for a short duration.

Intensity-modulated Radiation Therapy for Children with Intraocular Retinoblastoma:Potential Sparing of the Bony Orbit

AIMS

We have evaluated the potential for intensity-modulated radiation therapy (IMRT) to reduce dose to surrounding normal tissues in children with retinoblastoma confined to the globe of the eye.

MATERIALS AND METHODS

Treatment planning computed tomography (CT) scans from five children were used for comparison of four radiotherapy techniques to treat the eye. IMRT, conformal, anterior-lateral photon and en face electron plans were generated using the Corvus (NOMOS) and PLUNC treatment planning systems. Doses to surrounding critical structures were compared after normalisation of target coverage.

RESULTS

The IMRT treatment technique allowed the greatest sparing of the surrounding bony orbit, with an average of 60% of the ipsilateral bony orbit treated above 20 Gy and 48% treated above 24 Gy when 45 Gy is prescribed to the globe. IMRT techniques reduced dose to the surrounding bony orbit by more than one-third compared with anterior-lateral photon and electron techniques, and by 23% compared with conformal techniques. The application of IMRT also reduced dose to other surrounding normal tissues, including the temporal lobe and contralateral orbit.

CONCLUSION

IMRT shows potential for protecting normal tissues in patients requiring external beam radiation therapy for retinoblastoma.

Study design: evaluating gene-environment interactions in the etiology of breast cancer - the WECARE study

INTRODUCTION

Deficiencies in cellular responses to DNA damage can predispose to cancer. Ionizing radiation can cause cluster damage and double-strand breaks (DSBs) that pose problems for cellular repair processes. Three genes (ATM, BRCA1, and BRCA2) encode products that are essential for the normal cellular response to DSBs, but predispose to breast cancer when mutated.

DESIGN

To examine the joint roles of radiation exposure and genetic susceptibility in the etiology of breast cancer, we designed a case-control study nested within five population-based cancer registries. We hypothesized that a woman carrying a mutant allele in one of these genes is more susceptible to radiation-induced breast cancer than is a non-carrier. In our study, 700 women with asynchronous bilateral breast cancer were individually matched to 1400 controls with unilateral breast cancer on date and age at diagnosis of the first breast cancer, race, and registry region, and counter-matched on radiation therapy. Each triplet comprised two women who received radiation therapy and one woman who did not. Radiation absorbed dose to the contralateral breast after initial treatment was estimated with a comprehensive dose reconstruction approach that included experimental measurements in anthropomorphic and water phantoms applying patient treatment parameters. Blood samples were collected from all participants for genetic analyses.

CONCLUSIONS

Our study design improves the potential for detecting gene-environment interactions for diseases when both gene mutations and the environmental exposures of interest are rare in the general population. This is particularly applicable to the study of bilateral breast cancer because both radiation dose and genetic susceptibility have important etiologic roles, possibly by interactive mechanisms. By using counter-matching, we optimized the informativeness of the collected dosimetry data by increasing the variability of radiation dose within the case-control sets and enhanced our ability to detect radiation-genotype interactions.

Ocular preservation after 36 Gy external beam radiation therapy for retinoblastoma

PURPOSE

The purpose of this study was to document the ocular preservation rate after 36 Gy external beam radiation therapy (EBRT) for retinoblastoma.

PATIENTS AND METHODS

Forty-nine eyes of 38 patients were treated with a median dose of 36 Gy EBRT. The patient population included 7 unilateral and 31 bilateral presentations, with a median age at diagnosis of 4 months. Eyes enucleated at the time of diagnosis or treated with other measures were not included in the analysis of ocular preservation. The median age at EBRT was 8 months. Patients were monitored for progression of disease after EBRT and second malignant neoplasms.

RESULTS

The median follow-up was 88.6 months, with an estimated ocular preservation rate of 82.0% +/- 5% at 10 years. There was a difference in the ocular preservation rates for patients with advanced disease (Reese-Ellsworth group III-V) compared with early disease. Metastatic disease developed in two patients, and a second malignant neoplasm developed in three. Patients treated with en face electrons experienced a lower 5-year estimate of ocular preservation than those treated with photons, although patients treated with electrons were more likely to have advanced disease.

CONCLUSIONS

The use of low-dose EBRT (36 Gy) results in ocular preservation rates that are comparable to those of high-dose EBRT. The use of electrons requires careful treatment planning and computerized dosimetry.

The triad of bilateral retinoblastoma, dysplastic naevus syndrome and multiple cutaneous malignant melanomas: a case report and review of the literature

We report a case of a patient with the triad of retinoblastoma, dysplastic naevus syndrome (DNS) and multiple cutaneous melanomas. The combination of retinoblastoma and DNS is a significant risk factor for the development of cutaneous melanoma. This risk extends to family members. We recommend that survivors of (inherited) retinoblastoma and their relatives are closely screened for the presence of dysplastic naevi.

Spectrum of Znfn1a1 (Ikaros) inactivation and its association with loss of heterozygosity in radiogenic T-cell lymphomas in susceptible B6C3F1 mice

Ikaros (now known as Znfn1a1), a Krüppel-type zinc-finger transcription factor that plays a critical role in both lineage commitment and differentiation of lymphoid cells, has recently been shown to function as a tumor suppressor gene. We have previously reported a high frequency of LOH (approximately 50%) at the Znfn1a1 locus in radiation-induced T-cell lymphoma in susceptible B6C3F1 mice. The aim of the present study was to delineate the types of Znfn1a1 inactivation, with special reference to the LOH status, and to determine the relative contribution of each type of Znfn1a1 inactivation in radiation-induced T-cell lymphomas in B6C3F1 mice. We demonstrated that Znfn1a1 was frequently altered (in approximately 50% of T-cell lymphomas), and that its inactivation was caused by a variety of mechanisms, which came under one of the following four categories: (1) null expression (14%); (2) expression of unusual dominant-negative isoforms (11%); (3) amino acid substitutions in the N-terminal zinc-finger domain for DNA binding caused by point mutations (22%); (4) lack of the Znfn1a1 isoform 1 due to the creation of a stop codon by insertion of a dinucleotide in exon 3 (3%). The null expression, amino acid substitutions, and dinucleotide insertion inactivation types were well correlated with LOH at the Znfn1a1 allele (86%) and were consistent with Knudson's two-hit theory. On the other hand, T-cell lymphomas expressing dominant-negative Znfn1a1 isoforms retained both alleles. These results indicate that Znfn1a1 inactivation takes place by a variety of mechanisms in radiation-induced murine T-cell lymphomas and is frequently associated with LOH, this association depending on the type of inactivation.

Third (fourth and fifth) nonocular tumors in survivors of retinoblastoma

OBJECTIVE

This study aimed to investigate the incidence, timing, pattern, and distribution of, as well as survival as a result of, third, fourth, and fifth primary tumors in survivors of retinoblastoma.

DESIGN

This study was a retrospective case series of patients diagnosed with retinoblastoma and a second malignant neoplasm. Records were examined for demographic, prior treatment, and second tumor information, as well as any evidence of the development of a third, fourth, or fifth nonocular tumor. When possible, telephone inquiries were conducted for follow-up.

PARTICIPANTS

The study included 1506 patients followed in the Ophthalmic Oncology Center at New York-Presbyterian Hospital, New York Weill Cornell Medical Center, 211 of whom developed a second tumor and had sufficient treatment data to be useful for analysis.

MAIN OUTCOME MEASURES

The development of third and additional nonocular tumors and survival from these tumors were the primary outcome measures.

RESULTS

Of 211 second-tumor patients, 142 died before an additional malignancy developed (median survival time, 1.8 +/- 0.3 years) and in 28, third tumors developed (5-year incidence rate, 11%; 10-year incidence rate, 22%; median time to third tumor development, 5.8 +/- 8.3 years). The 5- and 10-year survival rates for this group were 41% and 30%, respectively (median survival time, 4.1 +/- 1.0 years). Of 28 patients in whom third tumors developed, 27 (96%) had received radiation therapy for their retinoblastoma. The most common sites for third tumors were soft tissues of the head (36% of all third tumors) and skin (36% of all third tumors). In six patients, a fourth tumor developed, and in two patients a fifth tumor developed. All fourth and fifth tumors were found in the soft tissues of the head, the skin, or the bones.

CONCLUSIONS

Survivors of retinoblastoma in whom second malignant neoplasms develop are at a higher risk for the development of additional tumors than they were for the development of a second tumor. The locations and expected ages at which additional tumors develop are consistent with the patterns we have seen in second tumors.

Second malignancies in children: the usual suspects?

The aim of this article is to provide an up to date review of second malignant neoplasms (SMN's) following treatment for childhood cancer, referring to their incidence, the role of genetic factors, and how the primary malignancy and treatment received influence the type, site and prognosis of SMN's. The role of genetic factors will be discussed as far as they impact upon a predisposition to later development of SMN's. The primary malignancies that have important associations with SMN's will then be discussed, in particular Hodgkin's disease, retinoblastoma and acute lymphoblastic leukaemia. The important second malignancies will be highlighted, including tumours of the CNS and thyroid, osteosarcoma, secondary acute myeloid leukaemia and melanoma. Emphasis will be put upon identifying which patients are most likely to suffer from these tumours. An important part of the article are case histories. These are provided in combination with illustrations as a useful adjunct to the text, with a particular emphasis on radiological features, diagnosis and screening. Finally, the important but different roles of causal agents, in particular chemotherapy and radiotherapy are highlighted.

Frequency of CD59 mutations induced in human-hamster hybrid A(L) cells by low-dose X-irradiation

Determination of the genotoxic effects of ionizing radiation, especially at low-doses, is of great importance for risk assessment, e.g. in radiological diagnostics. The human-hamster hybrid A(L) cell line has been shown previously to be a well-suited in vitro model for the study of mutations induced by various mutagens. The A(L) cells contain a standard set of hamster chromosomes and a single human chromosome 11, which confers the expression of the human cell surface protein CD59. Using CD59 specific antibodies, cells mutated in the CD59 gene can be detected and quantified by the loss of the cell surface marker. In contrast to previous studies, prior to irradiation we removed spontaneous mutants by magnetic cell separation (MACS) which allows analysis of radiation-induced mutation events only. We exposed A(L) cells to 100kV X-rays at 0.1 to 5Gy. The proportions of X-irradiation-induced CD59(-) mutants were quantified by flow cytometry after immunofluorescence labeling. Between 0.2 and 5Gy the yield of CD59 mutants was a linear function of dose. The molecular analysis of individual CD59-negative clones induced after exposure of 1, 3 and 5Gy of X-ray revealed a dose-dependent linear increase of large deletions (>6Mbp), whereas, point mutations could be seen only in spontaneous CD59 mutants or after low-dose exposure (< or =1Gy). We conclude that the modified A(L) assay presented here is appropriate for detection and quantification of non-lethal DNA lesions induced by low-dose ionizing radiation.

Proton therapy for uveal melanomas and other eye lesions

Charged particle beams are ideal for treating intra-ocular lesions, since they can be made to deposit their dose in the target, while significantly limiting dose received by non-involved ocular and orbital structures. Proton beam treatment of large numbers of uveal melanoma patients consistently achieves local control rates in excess of 95%, and eye retention rates of approximately 90%. Visual preservation is related to initial visual acuity, tumor size and location, and dose received by the macula, disc, and lens. The probability of distant metastasis is increased by larger tumor diameter, more anterior tumor location, and older patient age. Proton therapy is also effective treatment for patients with ocular angiomas, hemangiomas, metastatic tumors, and retinoblastomas, and may be beneficial for patients with exudative ("wet") age-related macular degeneration.

Retinoblastoma in transgenic mice: models of hereditary retinoblastoma

Retinoblastoma, the most common intraocular malignancy ill childhood, has served as a paradigm for the study of genetic mechanisms of oncogenesis. The retinoblastoma susceptibility gene RB1 was the first tumor suppressor gene to be cloned, and genetic and molecular biologic studies of this tumor have greatly expanded the understanding of the mechanics of tumorigenesis. Human retinoblastoma has essentially no naturally occuring animal counterpart. The development of transgenic murine models of retinoblastoma have created an experimental tool for manipulation of a tumor gene system in vivo. These models have also enabled studies of new therapeutic modalities. This review outlines the development of the transgenic murine models of retinoblastoma, together with the genetic mechanisms of retinoblastoma origin. Current therapeutic innovations developed by means of the transgenic models are described.

Second nonocular tumors in survivors of bilateral retinoblastoma: a possible age effect on radiation-related risk

OBJECTIVE

This study aimed to investigate the relationship in bilateral retinoblastoma survivors between the incidence of second tumors and the age when external beam radiation (EBR) was used.

DESIGN

A retrospective analysis of patients diagnosed with retinoblastoma was performed by examining records for background information and treatment information as well as reviewing documentation of patients with second nonocular tumors. Two telephone interviews were conducted for follow-up as well as inquiries directed to tumor registries and state databases.

PARTICIPANTS

The original study included 1729 patients treated in New York and Boston; the current study includes only the 1506 patients treated in New York. Of those, 816 patients were diagnosed with bilateral retinoblastoma, had sufficient treatment data to be useful, and survived at least 1 year from diagnosis.

MAIN OUTCOME MEASURES

The subjects were observed for evidence of the development of second nonocular tumors.

RESULTS

There was a significant decrease in tumor-free survival among patients treated with EBR before the age of 12 months, but no significant difference between the group treated with EBR after the age of 12 months and the group not treated with EBR. For tumors in the field of radiation, patients treated with early EBR showed a significant decrease in tumor-free survival when compared to patients treated with late EBR, with no significant difference between late radiation and no radiation. There were no significant differences between groups for tumors out of the field of radiation. Significant differences attributable to the use of EBR were found only for tumors of the skull and face bones and for tumors of the soft tissue of the head.

CONCLUSIONS

The long-term effect of radiation treatment on survivors of bilateral retinoblastoma is to increase the incidence and affect the distribution of second tumors. However, no increased risk is observed for tumors out of the field of radiation among patients who underwent radiation, and the risk for tumors in the field of radiation is heavily dependent on the age at which EBR is given and may be acceptably small to the patient after the age of 12 months.