Activity of irinotecan and temozolomide in the presence of O6-methylguanine-DNA methyltransferase inhibition in neuroblastoma pre-clinical models.

BACKGROUND: The combination of temozolomide (TMZ) and irinotecan is a regimen used in neuroblastoma patients with recurrent disease. O(6)-methylguanine-DNA methyltransferase (MGMT) may have a function in resistance to TMZ. Using neuroblastoma pre-clinical models, we determined whether the inhibition of MGMT by O(6)-benzylguanine (O6-BG) could enhance the anti-tumour activity of TMZ and irinotecan. METHODS: The cytotoxicity of TMZ and irinotecan, either alone or in combination, was measured in five neuroblastoma cell lines in the presence or absence of O6-BG with a fluorescence-based cell viability assay (DIMSCAN). Anti-tumour activity was measured in three neuroblastoma xenograft models. RESULTS: MGMT mRNA and protein were expressed in 9 out of 10 examined cell lines. Pretreatment of cells with 25 µM O6-BG decreased MGMT protein expression and enhanced The TMZ cytotoxicity by up to 0.3-1.4 logs in four out of five tested cell lines. TMZ (25 mg kg(-1) per day for 5 days every 3 weeks for four cycles) did not significantly improve mice survival, whereas the same schedule of irinotecan (7.5 mg kg(-1) per day) significantly improved survival (P<0.0001) in all three xenograft models. Combining O6-BG and/or TMZ with irinotecan further enhanced survival. CONCLUSION: Our in vitro and in vivo findings suggest that irinotecan drives the activity of irinotecan and TMZ in recurrent neuroblastoma. Inhibitors of MGMT warrant further investigation for enhancing the activity of regimens that include TMZ.

Central nervous system (CNS) tumors in the first six months of life: the Children's Hospital Los Angeles experience, 1979-2005.

BACKGROUND: The authors report the experience at the Children's Hospital Los Angeles with brain tumors diagnosed before 6 months of age, describing the characteristics of the patients, their tumors, treatment strategies, and prognostic factors. METHODS: Thirty-three children who were identified between 1979 and 2005 were included. Twelve were female (36%). There were 11 gliomas, 9 choroid plexus tumors, 8 medulloblastomas and supratentorial primitive neuroectodermal tumors (PNET), 2 atypical teratoid/rhabdoid tumors (ATRT), and 1 each of ependymoma, craniopharyngioma, and immature teratoma. Locations of primary tumors included 21 supratentorial (64%) and 7 posterior fossa, and 5 tumors involved both compartments. The treatment strategies included 5 patients with biopsy only, 18 less than gross total resections (

Marrow-ablative chemotherapy followed by tandem autologous hematopoietic cell transplantation in pediatric patients with malignant brain tumors.

To improve survival in young children with malignant brain tumors, irradiation-avoiding or -minimizing marrow-ablative chemotherapy (HDCx) with autologous hematopoietic cell transplantation (AuHCT) has been investigated. We evaluated the outcome of 44 children with malignant brain tumors treated with HDCx and tandem AuHCT at Children's Hospital Los Angeles between June 1999 and July 2012. Forty-four children with malignant brain tumors were studied. Twenty-one had medulloblastoma/primitive neuro-ectodermal tumor, eight atypical teratoid/rhabdoid tumor (ATRT), five high-grade glioma, four malignant germ cell tumor, three ependymoma and three choroid plexus carcinoma. Twenty-nine patients received three tandem transplants and 15 received two tandem transplants, respectively. The 5-year PFS and overall survivals (OS) for all patients were 46.3±8.2% and 51.7±8.5%, respectively. The PFS and OS for 27 newly diagnosed patients were 68.9±9.9% and 73.5±9.3%, respectively, compared with 17 transplanted at relapse 11.8±9.8% (P<0.001) and 15.1±12.3% (P=0.0231), respectively. The 5-year PFS and OS in 13 previously unirradiated patients were 74±13% and 74±13% versus 33.2±9.8% and 40.2±10.6% in 31 irradiated patients (P=0.11 and P=0.239), respectively. One patient died of transplant-related toxicity. HDCx with tandem AuHCT is feasible and safe in children with malignant brain tumors with encouraging irradiation-free survival in newly diagnosed children.

Age and TP53 mutation frequency in childhood malignant gliomas: results in a multi-institutional cohort.

Malignant astrocytoma is one of the most deadly primary central nervous system tumors. Although significant progress has been made in understanding the molecular pathways that lead to the development of these tumors in adults, comparatively little analysis has been done in childhood astrocytomas, which are less common and have a more favorable prognosis. Our previous studies of an institutional cohort of children with malignant gliomas suggested the existence of distinct molecular pathways of tumorigenesis in younger versus older children, based on the finding of a high frequency of TP53 mutations in tumors from children >3 years of age at diagnosis, compared with those from younger children. In the current study, the association between TP53 mutations and age was examined in greater detail using the multi-institutional group of children enrolled in Children's Cancer Group Study 945, the largest cohort of childhood high-grade gliomas analyzed to date. Seventy-seven tumors with centrally reviewed diagnoses of anaplastic astrocytoma or glioblastoma multiforme had sufficient archival histopathological material for microdissection-based genotyping. Sections were examined histologically, and topographic targets that contained malignant tissue were isolated by microdissection and subjected to PCR-based amplification and sequencing of TP53 exons 5-8. Twenty-six tumors (33.8%) had mutations in those exons. Mutations were observed in 2 of 17 tumors (11.8%) from children <3 years of age at diagnosis versus 24 of 60 tumors (40%) from older children, a difference that was statistically significant (P = 0.04), in agreement with our previous results. Whereas malignant gliomas in older children have a frequency of mutations comparable to tumors that arise in young adults, those from children <3 years old do not. The association between age and frequency of TP53 mutations among pediatric malignant gliomas indicates the probable existence of two distinct pathways of molecular tumorigenesis in younger versus older children.

Outcome of CNS disease at diagnosis in disseminated small noncleaved-cell lymphoma and B-cell leukemia: a Children's Cancer Group study.

PURPOSE: To examine the impact of initial CNS involvement on outcome and patterns of failure in patients with disseminated small noncleaved-cell lymphoma and B-cell leukemia who were treated in four successive Children's Cancer Group trials. PATIENTS AND METHODS: Of 462 patients with disseminated disease, 49 (10.6%) had CNS disease at diagnosis (CNS+). CNS disease included meningeal disease or CNS parenchymal masses with or without cranial neuropathies (CSF+/Mass; CNPs) in 36 patients and isolated CNPs in 13. Of the CNS+ patients, 28 had M2 (5% to 25% blasts) or M3 (> 25% blasts) bone marrow involvement. All patients received protocol-based systemic and intrathecal chemotherapy. Thirty-six patients also received CNS irradiation. RESULTS: Relapses occurred in 21 (43%) of 49 patients, predominantly in the CNS (71%) and bone marrow (52%). The 3-year event-free survival +/- SE for all patients with CNS+ disease was 45% +/- 7%. Patients with CSF+/Mass had a nominally higher treatment failure rate compared with patients with CNS- after adjusting for marrow status and lactate dehydrogenase (LDH) diagnosis, with a relative failure rate (RFR) of 1.52 (95% confidence interval [CI], 0.88 to 2.6; P =.15). In comparison, the RFRs for patients with M2 or M3 marrow and for those with LDH levels greater than 500 IU/L after adjusting for CNS disease were 1.4 (95% CI, 0.96 to 2.0; P =.029) and 2.2 (95% CI, 1.5 to 3.0; P <.001), respectively. The RFR for patients with isolated CNPs was 0.87 (95% CI, 0.36 to 2.1; P =.76). CONCLUSION: We conclude that, with the treatments used during the period covered by these studies, the presence of CSF+/Mass CNS disease at diagnosis was associated with a nominally worse outcome independent of initial bone marrow status and LDH level, but the effect was not statistically significant.

Large-cell lymphoma arising in the mediastinum in children and adolescents is associated with an excellent outcome: a Children's Cancer Group report.

PURPOSE: Large-cell lymphoma (LCL) arising in the mediastinum (LCL-M) is a heterogeneous group of non-Hodgkin's lymphoma (NHL) that includes B-cell lymphomas as well as T-cell lymphomas, including anaplastic LCL. LCL-M is well recognized in young adults but is less well characterized and infrequent in children and adolescents. METHODS: A retrospective review of Children's Cancer Group therapeutic studies for nonlymphoblastic lymphomas (CCG-551, CCG-503, CCG-552, and CCG-5911) identified 20 patients with LCL-M, representing 7.2% of all LCLs classified by central pathology review. RESULTS: The patients ranged in age from 4 to 19 years (median, 12.5 years; mean, 12 years); 55% of the patients were male. Although a variety of chemotherapy regimens were used, response was excellent, with all 20 patients (100%) achieving a complete response. Four patients (20%) experienced relapse locally or in distant sites including brain and kidney. One patient died of sepsis during therapy. For the 20 patients with LCL-M, the product-limit estimated 5-year event-free survival (EFS) and 5-year overall survival (OS) rates are 75% +/- 10% and 85% +/- 8%, respectively. For disseminated LCLs (192 cases), the EFS and OS rates were 50% +/- 4% and 63% +/- 4%, respectively, which differ significantly from the those of the LCL-M cases (EFS, P =.025; OS, P =.034). The 5-year EFS and OS rates for patients with localized LCL (67 cases) were 92 +/- 3% and 97 +/- 2%, respectively. CONCLUSION: LCL-M is a heterogeneous group of NHLs that makes up approximately 7.2% of LCL in children and adolescents. Response to therapy and OS in this young age group seems excellent and superior to that of disseminated LCLs but inferior to that of other localized LCL. Future studies of LCL-M will evaluate short intense chemotherapy administered without radiation therapy.

Similar efficacy of 6 and 18 months of therapy with four drugs (COMP) for localized non-Hodgkin's lymphoma of children: a report from the Childrens Cancer Study Group.

Successful treatment of localized non-Hodgkin's lymphoma (NHL) in childhood with 18 months of cyclophosphamide, vincristine, methotrexate (MTX), and prednisone (COMP) prompted a randomized clinical trial to determine whether a 6-month course of the same therapy was as effective as an 18-month course when combined with local irradiation. Two successive Childrens Cancer Study Group (CCSG) protocols (CCG 551 and CCG 501) entered 232 eligible patients from October 1979 until April 1986. Initially, all children with localized disease were considered eligible, but by a subsequent amendment, those with lymphoblastic (LB) histology were excluded. Hence, the study population consisted of 211 patients with nonlymphoblastic (NLB) and 21 with LB disease. Early relapses (before 6 months) occurred in 13 patients with NLB histology. Late relapses were seen in seven patients, three with LB histology. Among the 104 randomized patients who followed the prescribed therapy, there were four recurrences and no differences between 6-month and 18-month therapy. The overall survival for NLB disease was 91% on CCG 551 and 98% on CCG 501. We conclude that 6 months of COMP is excellent therapy for children with localized NLB NHL.

Long-term follow-up of patients treated with COMP or LSA2L2 therapy for childhood non-Hodgkin's lymphoma: a report of CCG-551 from the Childrens Cancer Group.

PURPOSE: We analyzed the long-term results of a Childrens Cancer Group (CCG) randomized study comparing cyclophosphamide, vincristine, methotrexate, and prednisone (COMP) versus LSA2L2 as treatment for childhood non-Hodgkin's lymphoma. The initial results were previously reported (N Engl J Med 308:559, 1983). PATIENTS AND METHODS: A total of 429 patients are reported here, 68 with localized disease and 361 with disseminated disease. The distribution of disseminated-disease patients by histologic type was 164 lymphoblastic, 60 large-cell, and 137 undifferentiated lymphomas. Median follow-up duration of surviving patients is 8 years. RESULTS: Event-free survival (EFS) of patients with localized disease was 84% at 5 years. No differences were seen between the two treatment regimens. Results for patients with disseminated disease was dependent on histologic subtype: patients with lymphoblastic lymphoma did better when treated with LSA2L2 (5-year EFS of 64% v 35% for COMP); COMP produced better results for patients with undifferentiated lymphoma (5-year EFS of 50% v 29% for LSA2L2). Results for large-cell lymphoma patients were similar (5-year EFS of 52% for COMP v 43% for LSA2L2). Five percent of patients died of treatment-related complications while on therapy (primarily infections). Only four deaths without progression have been observed off-therapy (two from restrictive lung disease, one from an acute asthma attack, one from colon cancer). Patient survival rates after recurrence were poor. CONCLUSION: Treatment success can be expected in 84% of pediatric patients with localized non-Hodgkin's lymphoma. For patients with disseminated disease, treatment success can be expected in 64% of those with lymphoblastic and 50% of those with undifferentiated or large-cell disease. To date, late adverse events are rare.

Outcomes of treatment of children and adolescents with recurrent non-Hodgkin's lymphoma and Hodgkin's disease with dexamethasone, etoposide, cisplatin, cytarabine, and l-asparaginase, maintenance chemotherapy, and transplantation: Children's Cancer Group Study CCG-5912.

PURPOSE: To determine the toxicity and response rate in children treated with dexamethasone, etoposide, cisplatin, high-dose cytarabine, and L-asparaginase (DECAL) for recurrent non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). PATIENTS AND METHODS: Ninety-seven children with recurrent NHL (n = 68) or HD (n = 29) were enrolled. Treatment consisted of two cycles of DECAL, then bone marrow transplantation or up to four cycles of ifosfamide, mesna, and etoposide alternating with DECAL maintenance therapy. RESULTS: After two cycles of DECAL induction therapy, complete response (CR) or partial response (PR) was reported in 19 (65.5%; 10 CRs and nine PRs) of 29 patients with HD and 29 (41.6%; 23 CRs and six PRs) of 68 patients with NHL. When only 24 patients with HD and 58 patients with NHL who were assessable for response were considered, the response rates were 79.2% (19 of 24 patients) and 50.0% (29 of 58 patients), respectively. Five-year event-free survival was 26% +/- 9% and 23% +/- 5% in patients with HD and NHL, respectively. Five-year survival was 31% +/- 14% and 30% +/- 6%, respectively. Although median time to treatment failure was significantly longer in patients with HD (EFS, P =.002; survival, P =.011), this difference did not translate into a higher long-term survival. Grade 3 or 4 toxic effects were observed during induction in 70 (72%) of 97 patients and during maintenance in 45 (70%) of 64 courses of DECAL therapy. Pancytopenia and systemic infections in particular were frequently observed. Other toxic effects were uncommon. Although not a formal part of the therapy or the study design, 42 patients who responded to therapy who underwent bone marrow transplant did not show any benefit from this approach. CONCLUSION: DECAL is an effective and tolerable salvage regimen for treating patients with recurrent NHL and HD.

The treatment of localized non-Hodgkin's lymphoma in children: a report from the Children's Cancer Study Group.

Investigators of the Children's Cancer Study Group entered 73 children with previously untreated localized non-Hodgkin's lymphoma on a prospective randomized trial of systemic treatment with either a four-drug program (cyclophosphamide, vincristine, methotrexate, prednisone [COMP]) or a 10-drug (LSA2-L2 modified) program of 18 months duration. All patients received central nervous system prophylaxis with intrathecal methotrexate and most received local or regional radiation treatment. The three-year relapse-free survival rate for all patients (N = 73) was 84%; for COMP (N = 42) was 85%, and for LSA2-L2 (N = 31) was 84%. Of the 12 patients who suffered adverse events eight relapsed and four died of toxicity. Histopathology was reviewed centrally. Of 32 patients with nonlymphoblastic disease treated with COMP only one relapsed. Of 26 patients treated with LSA2-L2, four relapsed. Patients with localized lymphoblastic disease were uncommon. None of three patients treated with LSA2-L2 relapsed compared with three of nine treated with COMP. COMP is an excellent treatment for patients with localized disease of nonlymphoblastic type, but the relative value of the two regimens for patients with localized lymphoblastic disease is uncertain.

Treatment outcome and prognostic factors for infants with acute lymphoblastic leukemia treated on two consecutive trials of the Children's Cancer Group.

PURPOSE: Infants represent a very poor risk group for acute lymphoblastic leukemia (ALL). We report treatment outcome for such patients treated with intensive therapy on consecutive Children's Cancer Group (CCG) protocols. PATIENTS AND METHODS: Between 1984 and 1993, infants with newly diagnosed ALL were enrolled onto CCG-107 (n = 99) and CCG-1883 (n = 135) protocols. Postconsolidation therapy was more intensive on CCG-1883. On both studies, prophylactic treatment of the CNS included both high-dose systemic chemotherapy and intrathecal therapy, in contrast to whole-brain radiotherapy, which was used in earlier studies. RESULTS: Most patients (>95%) achieved remission with induction therapy. The most frequent event was a marrow relapse (46 patients on CCG-107 and 66 patients on CCG- 1883). Four-year event-free survival was 33% (SE = 4.7%) on CCG-107 and 39% (SE = 4.2%) on CCG- 1883. Both studies represent an improvement compared with a 22% (SE = 5.1%) event-free survival for historical controls. Four-year cumulative probabilities of any marrow relapse or an isolated CNS relapse were, respectively, 49% (SE = 5%) and 9% (SE = 3%) on CCG-107 and 50% (SE = 5%) and 3% (SE = 2%) on CCG-1883, compared with 63% (SE = 6%) and 5% (SE = 3%) for the historical controls. Independent adverse prognostic factors were age less than 3 months, WBC count of more than 50,000/microL, CD10 negativity, slow response to induction therapy, and presence of the translocation t(4;11). CONCLUSION: Outcome for infants on CCG-107 and CCG- 1883 improved, compared with historical controls. Marrow relapse remains the primary mode of failure. Isolated CNS relapse rates are low, indicating that intrathecal chemotherapy combined with very-high-dose systemic therapy provides adequate protection of the CNS. The overall unsatisfactory outcome observed for the infant ALL population warrants the future use of novel alternative therapies.

Results of a pilot study of hyperfractionated radiation therapy for children with brain stem gliomas.

The majority of children with brain stem gliomas develop progressive disease within 18 months of diagnosis and treatment. Radiotherapy (RT) is of transient benefit in most patients and higher total doses of RT have been related to improved survival. The amount of RT which can be given is limited by the tolerance of the surrounding brain. Hyperfractionated RT theoretically allows higher doses of RT to be tolerated by the brain. Sixteen children with brain stem gliomas were treated on a hyperfractionated RT schedule, receiving 120 cGy of RT twice daily, to a total dose of 6480 cGy. All patients tolerated treatment well. Eleven of 15 (73%) evaluable patients had a response to treatment and two (13%) others had stable disease. One patient developed progressive disease during treatment. All patients were tapered off steroids by the completion of treatment. Thirteen of 16 (81%) patients developed progressive disease at a median of 7 months after diagnosis and three remain in remission 8, 12, and 15 months following diagnosis. These results were similar to those of historical controls. Two patients were surgically explored at time of relapse and 5 have had an autopsy. No acute or subacute neurologic toxicity was seen; but long-term detrimental effects on brain could not be assessed. The implications of this study are that escalations of the dose of hyperfractionated RT can be entertained for children with brain stem gliomas.

Brachytherapy for primary and recurrent nasopharyngeal carcinoma: 20 years' experience at Long Beach Memorial.

PURPOSE: We evaluated treatment outcomes of patients with mostly locally advanced primary and recurrent cancer of the nasopharynx managed with interstitial and intraluminal brachytherapy. METHODS AND MATERIALS: This is a retrospective analysis of 56 patients with cancer arising from the nasopharynx treated with interstitial and intracavitary afterloading brachytherapy from 1978 to 1997. Patients were divided into three treatment groups: 15 patients with primary cancer (Group 1), 34 patients with recurrent or persistent disease (Group 2), and 7 patients with cancer in the nasopharynx who had history of previous definitive radiation therapy to the nasopharynx for head and neck cancer (Group 3). Fifty-three percent of patients in Group 1 had 1992 AJCC Stage IV disease, and 49% of patients in Groups 2 and 3 had extensive disease (defined as T3, T4, or parapharyngeal extension). Group 1 received megavoltage radiation to 50-60 Gy followed by a boost to the primary site and neck (in cases of persistent neck disease) with a combination of interstitial and intracavitary brachytherapy (mean dose 33-37 Gy). Five patients received chemotherapy, and 6 patients received hyperthermia. Groups 2 and 3 patients were treated with brachytherapy implants (mean dose 50-58 Gy) without external beam radiation. Twenty-five patients received chemotherapy either before or during radiation, and 21 patients received hyperthermia. RESULTS: The overall survival at 2, 5, and 10 years for patients in Group 1 was 79%, 61%, and 61%, respectively, and for patients in Groups 2 and 3 combined was 48%, 30%, and 20%, respectively. Cause-specific survival at 2, 5, and 10 years was 87%, 74%, and 74%, respectively, for patients in Group 1; and 82%, 60%, and 60%, respectively, for patients in Groups 2 and 3. Local control at 2, 5, and 10 years was 93%, 93%, and 77%, respectively, for patients in Group 1; and 81%, 59%, and 49%, respectively, for patients in Groups 2 and 3. Control in the neck at 2, 5, and 10 years was achieved in 93%, 93%, and 93% of patients, respectively, in Group 1; and 88%, 81%, and 81%, respectively, for patients in Groups 2 and 3. Disease-free survival was 87%, 74%, and 62%, respectively, for patients in Group 1, and 56%, 41%, and 34%, respectively, for patients in Groups 2 and 3. There were 4 peri-operative deaths. One death (2%) was attributable to the development of late complications. Forty-five percent of patients experienced some form of late complications. CONCLUSION: Interstitial afterloading brachytherapy can provide effective treatment for nasopharyngeal cancers, especially for locally persistent/recurrent and locally extensive lesions.

The pathology of non-Hodgkin's lymphoma of childhood: II. Reproducibility and relevance of the histologic classification of "undifferentiated" lymphomas (Burkitt's versus non-Burkitt's).

The Children's Cancer Study Group conducted prospective clinical trials of 608 children with non-Hodgkin's lymphoma from 1977 to 1983. In 1980, significant differences in survival of children with disseminated disease correlated with histologic diagnosis and the randomized treatment employed. A pathology reproducibility review showed the lymphoblastic lymphoma cases to be virtually 100 per cent distinguishable histologically from the nonlymphoblastic lymphomas (Burkitt's, non-Burkitt's, and "histiocytic"). However, diagnostic reproducibility of the pathologist-of-record was 59 per cent in the Burkitt's and non-Burkitt's lymphoma group. Therefore, 159 cases, agreed on by the pathologist-of-record and the "lymphoma panel" as Burkitt's (77 cases) or non-Burkitt's lymphoma (82 cases) and designated as the "reference diagnosis," were blindly reviewed twice each by two hematopathologists to yield the "review diagnoses." Consensus agreement was achieved in 67 per cent of cases overall, 82 per cent of Burkitt's and 54 per cent of non-Burkitt's lymphoma. Using the "reference diagnoses," we found that the relative frequency of Burkitt's and non-Burkitt's lymphoma was associated with the extent of disease at diagnosis (P = 0.06) but not with other prognostic factors. Despite the difficulties in histologic classification, analyses that used either "reference diagnoses" or "consensus review diagnoses" and that were adjusted for extent of disease consistently demonstrated significantly shorter event-free survival for patients having Burkitt's lymphoma; their failure rate was four times that for patient's with non-Burkitt's lymphoma. Newer cell biologic techniques hopefully will enhance histopathologic distinctions that remain the basis for diagnosis.

Dose survival of G0 lymphocytes irradiated in vitro: a test for a possible population bias in the cohort of atomic bomb survivors exposed to high doses.

This study was intended to test for a possible early selective loss of relatively radiosensitive individuals from those atomic bomb survivors exposed to high doses using an in vitro X-ray dose-survival assay of peripheral blood lymphocytes. The assay was reasonably reproducible since the coefficient of variation (CV) was 8.2% for the mean D10 (the dose required to kill 90% of cells) of 3.39 Gy after 15 repeat tests for one control donor during the study period. The CV for single tests for 201 survivors was essentially the same, i.e., 7.7% with a mean D10 of 3.37 Gy, indicating very little heterogeneity of lymphocyte radiosensitivity among individuals. Linear regression analysis of D10 on the DS86 dose showed no evidence for the consistent change in average D10 values among the survivors exposed to high doses. The results might imply that the G0 lymphocytes do not express full variations in radiosensitivity and may not be suitable for quantitative measurements of relative radiosensitivity. Alternatively, the very small variation in lymphocyte radiosensitivity may be real and detection of the rare individuals with altered radiosensitivity may require much larger-scale testing. Therefore, no conclusive answer to the question of population bias was provided for the survivors.

An estimate of the magnitude of random errors in the DS86 dosimetry from data on chromosome aberrations and severe epilation.

An analysis of the proportion of cells with chromosome aberrations in cultured blood lymphocytes from A-bomb survivors in Hiroshima and Nagasaki reveals that the dose-response relationship using DS86 assigned dose is significantly steeper in the subsample of individuals who reported severe epilation after the bombings than in those who did not report severe epilation. This effect is due either to random errors in the DS86 dose assignments or to individual differences in sensitivity to radiation, or to both. In this paper, working within a class of dosimetry error models, we estimate the magnitude of random dosimetry errors which would be required to account for all of the difference in the observed dose response between people who did and did not report severe epilation under the assumption that random dosimetry error is the only cause of the effect. We conclude that random dosimetry errors in the range 45 to 50% of true dose are necessary to explain completely the difference in dose response between the two epilation groups. We discuss evidence that the contribution of individual differences in radiation sensitivity to the observed epilation effect is likely to be small, so that random dosimetry errors may be the major cause of this effect.

Is interindividual variation of cellular radiosensitivity real or artifactual?

A recently developed dose-survival assay using human G0 T lymphocytes from peripheral blood was employed to assess possible interindividual variation of cellular radiosensitivity by comparing variability between a single test for different individuals and repeated tests for a single donor. The surviving fraction at each X-ray dose level fluctuated similarly between the two groups, and the X-ray dose required to kill 90% of the cells (D10) was 3.59 +/- 0.18 Gy (mean +/- SD) for 31 different individuals and 3.66 +/- 0.21 Gy for 28 repeated tests of one individual. Analysis of variance to compare the two sets of data showed that variation in the D10 value was not significantly greater in the former group. Analysis of D50 and D90 showed similar results. These results support the hypothesis that interindividual variation in cellular radiosensitivity is quite small, if it exists at all, as far as can be determined by the loss of colony-forming ability of irradiated G0 lymphocytes.

X-ray-induced mutations in cultured human thyroid cells.

Cultured human thyroid cells were X-irradiated in vitro and assayed for resistance to 6-thioguanine. The average mutant frequency was 1.69 +/- 1.34 X 10(-5) (mean +/- SD) in controls, 3.74 +/- 2.21 X 10(-5) in cells exposed to 1 Gy, and 7.19 +/- 5.37 X 10(-5) in cells exposed to 2 Gy. The positive association between mutant frequency and dose was statistically significant. The estimated mutation induction rate was 2.54 +/- 0.71 X 10(-5) per gray, which is in close agreement with published results for human skin fibroblasts and mammary epithelial cells. These results extend and confirm earlier reports that mutation induction rates for fibroblasts and epithelial cells after exposure to X rays are similar.

Stable chromosome aberrations among A-bomb survivors: an update.

Analysis of data on stable chromosome aberrations collected between 1968 and 1985 by the Radiation Effects Research Foundation (RERF) on 1703 individuals exposed to A-bomb radiation in Hiroshima and Nagasaki, Japan, reveals different dose-response relationships in the two cities, as well as significant effects of both time of assay and age at exposure. In Hiroshima, the proportion of cells with aberrations increased by 0.080 per sievert at low doses, assuming a constant neutron radiation RBE of 10 relative to gamma radiation, for assays performed during the latest period (1981-1985). In Nagasaki, the low-dose increase was 0.0126 per sievert. There was evidence that radiation exposure was more effective for producing stable aberrations at some younger ages at exposure, although the interpretation of this interaction is difficult. Modeling neutron and gamma-ray components of dose separately in a way which allows the neutron RBE to vary with dose yielded an estimated low-dose limiting value of RBE of 707 (95% confidence bound 200-infinity), with a low-dose response of approximately 0.008 aberrations per sievert. This RBE is much higher than the published RBEs for induction of aberrations in vitro. The high estimated RBE and the differences in dose response by city both are suggestive of systematic dose estimation errors in which either neutrons were underestimated in Hiroshima or gamma rays were overestimated in Nagasaki.

Hyperparathyroidism among atomic bomb survivors in Hiroshima.

To determine the effect of exposure to atomic bomb radiation on the occurrence of hyperparathyroidism, the prevalence was determined among a population of 3,948 atomic bomb survivors and their controls in Hiroshima. The diagnosis of hyperparathyroidism was based upon histopathological findings or the presence of consistent hypercalcemia and elevated levels of serum parathyroid hormone. Primary hyperparathyroidism was diagnosed in 19 persons (3 males, 16 females). Females had approximately a threefold higher overall prevalence of hyperparathyroidism than males (P less than 0.05). The prevalence rates of hyperparathyroidism increased with radiation dose (chi2(1) = 12, P less than 0.001) after adjusting for sex and age at the time of the bombing. The estimated relative risk was 4.1 at 1 Gy (95% confidence limits 1.7 to 14). There was some evidence that the effect of radiation was greater for individuals who were younger at the time of the bombing. In conclusion, exposure to atomic bomb radiation affected the occurrence of hyperparathyroidism, suggesting that doses of radiation lower than those used in radiotherapy may also induce this disorder.