Chromosomal radiosensitivity in breast cancer patients: influence of age of onset of the disease

The age dependency of onset of the disease on chromosomal radiosensitivity of an unselected group of breast cancer patients (n=100) was investigated and compared to a group of healthy women (n=100). The chromosomal radiosensitivity was assessed with the G2 and the G0 micro-nucleus (MN) assay. For the G2 assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy 60Co gamma-rays after 70 h incubation and chromatid breaks were scored in 50 metaphases. For the G0 MN assay lymphocytes were exposed in vitro to 3.5 Gy 60Co gamma-rays at low dose rate (LDR). 72 h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. The results demonstrated that the group of breast cancer patients was more radiosensitive than a population of healthy women and this with both the G2 and the G0 MN assay. Analyses of the G2 and MN response in different age groups of the breast cancer patients revealed no significant differences in mean G2 and MN scores and suggest that the age of onset of the disease has no effect on chromosomal radiosensitivity in unselected breast cancer patients. Correlations with different clinical parameters were also investigated.     

Radiation-induced micronucleus induction in lymphocytes identifies a high frequency of radiosensitive cases among breast cancer patients: a test for predisposition?

Enhanced sensitivity to the chromosome-damaging effects of ionizing radiation is a feature of many cancer-predisposing conditions. We previously showed that 42% of an unselected series of breast cancer patients and 9% of healthy control subjects showed elevated chromosomal radiosensitivity of lymphocytes irradiated in the G2 phase of the cell cycle. We suggested that, in addition to the highly penetrant genes BRCA1 and BRCA2, which confer a very high risk of breast cancer and are carried by about 5% of all breast cancer patients, there are also low-penetrance predisposing genes carried by a much higher proportion of breast cancer patients, a view supported by recent epidemiological studies. Ideally, testing for the presence of these putative genes should involve the use of simpler methods than the G2 assay, which requires metaphase analysis of chromosome damage. Here we report on the use of a simple, rapid micronucleus assay in G0 lymphocytes exposed to high dose rate (HDR) or low dose rate gamma-irradiation, with delayed mitogenic stimulation. Good assay reproducibility was obtained, particularly with the HDR protocol, which identified 31% (12 out of 39) of breast cancer patients compared with 5% (2 out of 42) of healthy controls as having elevated radiation sensitivity. In the long term, such cytogenetic assays may have the potential for selecting women for intensive screening for breast cancer.     

Chromosomal radiosensitivity in breast cancer patients with a known or putative genetic predisposition

The chromosomal radiosensitivity of breast cancer patients with a known or putative genetic predisposition was investigated and compared to a group of healthy women. The chromosomal radiosensitivity was assessed with the G2 and the G0-micronucleus assay. For the G2 assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy (60)Co gamma-rays after 71 h incubation, and chromatid breaks were scored in 50 metaphases. For the micronucleus assay lymphocytes were exposed in vitro to 3.5 Gy (60)Co gamma-rays at a high dose rate or low dose rate. 70 h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. The results demonstrated that the group of breast cancer patients with a known or putative genetic predisposition was on the average more radiosensitive than a population of healthy women, and this with the G2 as well as with the high dose rate and low dose rate micronucleus assay. With the G2 assay 43% of the patients were found to be radiosensitive. A higher proportion of the patients were radiosensitive with the micronucleus assay (45% with high dose rate and 61% with low dose rate). No correlation was found between the G2 and the G0-micronucleus chromosomal radiosensitivity. Out of the different subgroups considered, the group of the young breast cancer patients without family history showed the highest percentage of radiosensitive cases in the G2 (50%) as well as in the micronucleus assay (75-78%).     

Chromosomal radiosensitivity in two cell lineages derived from clinically radiosensitive cancer patients.

PURPOSE: Despite its prominent contribution to cancer cure and palliation, around 1% to 5% of cancer patients suffer serious side effects from radiotherapy. A cardinal goal in the fields of radiobiology and oncology is to predict normal tissue radiosensitivity of a cancer patient before radiotherapy. Higher tumor control rates are likely if radiotherapy individualization could be achieved by applying predictive approaches. EXPERIMENTAL DESIGN: Here, we make use of the cytokinesis block micronucleus assay to assess radiosensitivity in cell lines derived from two different cell lineages obtained from clinically radiosensitive patients. We determined the micronucleus frequency after graded doses of ionizing radiation to primary fibroblasts and lymphoblast cell lines derived from 36 highly radiosensitive cancer patients. RESULTS: Many cell lines, following exposure to ionizing radiation, from patients with severe clinical reactions to radiotherapy showed statistically significantly higher frequencies of micronuclei than those from patients who had normal reactions to radiotherapy. One individual revealed significantly higher micronucleus frequencies in both cell lineages. Interestingly, lymphoblast cell lines from one patient showed micronucleus frequencies similar to ataxia telangiectasia mutated-deficient cells. CONCLUSIONS: These results indicate that the micronucleus assay may have use for identifying predisposition to clinical radiosensitivity, at least in a subset of patients as a component of a pretreatment radiosensitivity assay for use in the clinic.     

Radiation-induced damage to normal tissues after radiotherapy in patients treated for gynecologic tumors: association with single nucleotide polymorphisms in XRCC1, XRCC3, and OGG1 genes and in vitro chromosomal radiosensitivity in lymphocytes

PURPOSE: To examine the association of polymorphisms in XRCC1 (194Arg/Trp, 280Arg/His, 399Arg/Gln, 632Gln/Gln), XRCC3 (5' UTR 4.541A>G, IVS5-14 17.893A>G, 241Thr/Met), and OGG1 (326Ser/Cys) with the development of late radiotherapy (RT) reactions and to assess the correlation between in vitro chromosomal radiosensitivity and clinical radiosensitivity. METHODS AND MATERIALS: Sixty-two women with cervical or endometrial cancer treated with RT were included in the study. According to the Common Terminology Criteria for Adverse Events, version 3.0, scale, 22 patients showed late adverse RT reactions. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assays were performed to examine polymorphic sites, the G2 assay was used to measure chromosomal radiosensitivity, and patient groups were compared using actuarial methods. RESULTS: The XRCC3 IVS5-14 polymorphic allele was significantly associated with the risk of developing late RT reactions (odds ratio 3.98, p = 0.025), and the XRCC1 codon 194 variant showed a significant protective effect (p = 0.028). Patients with three or more risk alleles in XRCC1 and XRCC3 had a significantly increased risk of developing normal tissue reactions (odds ratio 10.10, p = 0.001). The mean number of chromatid breaks per cell was significantly greater in patients with normal tissue reactions than in patients with no reactions (1.16 and 1.34, respectively; p = 0.002). Patients with high chromosomal radiosensitivity showed a 9.2-fold greater annual risk of complications than patients with intermediate chromosomal radiosensitivity. Combining the G2 analysis with the risk allele model allowed us to identify 23% of the patients with late normal tissue reactions, without false-positive results. CONCLUSION: The results of the present study showed that clinical radiosensitivity is associated with an enhanced G2 chromosomal radiosensitivity and is significantly associated with a combination of different polymorphisms in DNA repair genes.     

Absence of mutations in the ATM gene in breast cancer patients with severe responses to radiotherapy.

The effectiveness of cancer radiotherapy is compromised by the small proportion (approximately 5%) of patients who sustain severe normal tissue damage after standard radiotherapy treatments. Predictive tests are required to identify these highly radiosensitive cases. Patients with the rare, recessively inherited, cancer-prone syndrome ataxia-telangiectasia (A-T) sustain extremely severe normal tissue necrosis after radiotherapy and their cultured cells are also highly radiosensitive. Clinically normal carriers (heterozygotes) of the A-T gene have an increased risk of breast cancer, account for approximately 4% of all breast cancer cases and show a modest increase in cellular radiosensitivity in vitro. It has been suggested that a substantial proportion of highly radiosensitive (HR) breast cancer patients may be A-T heterozygotes, and that screening for mutations in the A-T gene could be used as a predictive test. We have tested this hypothesis in a group of cancer patients who showed adverse reactions to radiotherapy. Sixteen HR breast cancer patients showing mainly acute reactions (and seven HR patients with other cancers) were tested for ATM mutations using the restriction endonuclease fingerprinting assay. No mutations typical of those found in obligate A-T heterozygotes were detected. If the estimate that 4% of breast cancer cases are A-T gene carriers is correct, then ATM mutations do not confer clinical radiosensitivity. These early results suggest that screening for ATM mutations in cancer patients may not be of value in predicting adverse reactions.     

Partial breast brachytherapy after lumpectomy: low-dose-rate and high-dose-rate experience

PURPOSE: The use of partial breast brachytherapy (PBB) after lumpectomy for selected patients with early-stage breast cancer reduces the adjuvant radiotherapy treatment time to <1 week. Despite the advantages of accelerated treatment, maintaining an acceptable cosmetic outcome is important. In a cohort of patients who received low-dose-rate (LDR) or high-dose-rate (HDR) PBB after lumpectomy, the clinical characteristics and treatment parameters were analyzed to identify predictors for an unfavorable cosmetic outcome. METHODS AND MATERIALS: Early-stage breast cancer patients with clear resection margins and 0-3 positive lymph nodes were eligible for PBB. Uniform guidelines for target definition and brachytherapy catheter placement were applied. The HDR PBB dose was 34 Gy in 10 fractions within 5 days, and the LDR dose was 45 Gy given at a rate of 50 cGy/h. The end points included incidence of radiation recall reaction, telangiectasias, and cosmetic-altering fibrosis. RESULTS: Between 1995 and 2000, 44 patients with early-stage breast cancer received PBB without adjuvant external beam radiotherapy after lumpectomy (31 HDR PBB, 13 LDR PBB). After a median follow-up of 42 months (range 18-86), all patients remained locally controlled. The overall rate of good/excellent cosmetic outcome was 79.6% overall and 90% with HDR PBB. Radiation recall reactions occurred in 43% of patients (6 of 14) who received adriamycin. LDR PBB and adriamycin were significant predictors for late unfavorable cosmetic changes in univariate analysis (p = 0.003 and p = 0.005, respectively). CONCLUSION: Although a high rate of local control and good/excellent cosmetic outcome is provided with HDR PBB, the risk of unfavorable cosmetic changes when treated with both LDR PBB and adriamycin is noteworthy. This suggests that HDR PBB is preferred in patients for whom adriamycin is indicated.     

The increment of micronucleus frequency in cervical carcinoma during irradiation in vivo and its prognostic value for tumour radiocurability.

A potential usefulness of micronucleus assay for prediction of tumour radiosensitivity has been tested in 64 patients with advanced stage (II B-IV B) cervical carcinoma treated by radiotherapy. The study of cellular radiosensitivity in vitro was conducted in parallel with the study of cellular damage after tumour irradiation in vivo. Radiosensitivity of in vitro cultured primary cells isolated from tumour biopsies taken before radiotherapy was evaluated using cytokinesis-block micronucleus assay. Frequency of micronuclei per binucleated cell (MN/BNC) at 2 Gy was used as a measure of radiosensitivity. Radiation sensitivity in vivo was expressed as per cent increment of micronucleus frequency in cells isolated from biopsy taken after 20 Gy (external irradiation, 10 x 2 Gy) over the pre-treatment spontaneous micronucleus level and was called MN20. Very low correlation (r = 0.324) was observed between micronucleus frequency in vitro and in vivo. Although micronucleus frequency at 2 Gy differed widely between tumours evaluated (mean MN/BNC was 0.224; range 0.08-0.416), no significant correlation was observed between this parameter and clinical outcome. The average increment of micronucleus frequency after 20 Gy amounted to 193% of spontaneous level (range 60-610%) and was independent of spontaneous micronucleation before radiotherapy. In contrast to in vitro results, these from in vivo assay seem to have a predictive value for radiotherapy of cervix cancer. The micronucleus increment in vivo that reached at least 117.5% of pretreatment value (first quartile for MN20 data set) correlated significantly with better tumour local control (P < 0.008) and overall survival (P < 0.045). Our results suggest that evaluation of increment of micronucleus frequency during radiotherapy (after fixed tested dose of 20 Gy) offers a potentially valuable approach to predicting individual radioresponsiveness and may be helpful for individualization of treatment strategy in advanced stage cervical cancer.     

Radiosensitivity in breast cancer assessed by the Comet and micronucleus assays

Spontaneous and radiation-induced genetic instability of peripheral blood mononuclear cells derived from unselected breast cancer (BC) patients (n=50) was examined using the single-cell gel electrophoresis (Comet) assay and a modified G2 micronucleus (MN) test. Cells from apparently healthy donors (n=16) and from cancer patients (n=9) with an adverse early skin reaction to radiotherapy (RT) served as references. Nonirradiated cells from the three tested groups exhibited similar baseline levels of DNA fragmentation assessed by the Comet assay. Likewise, the Comet analysis of in vitro irradiated (5 Gy) cells did not reveal any significant differences among the three groups with respect to the initial and residual DNA fragmentation, as well as the DNA repair kinetics. The G2 MN test showed that cells from cancer patients with an adverse skin reaction to RT displayed increased frequencies of both spontaneous and radiation-induced MN compared to healthy control or the group of unselected BC patients. Two patients from the latter group developed an increased early skin reaction to RT, which was associated with an increased initial DNA fragmentation in vitro only in one of them. Cells from the other BC patient exhibited a striking slope in the dose-response curve detected by the G2 MN test. We also found that previous RT strongly increased both spontaneous and in vitro radiation-induced MN levels, and to a lesser extent, the radiation-induced DNA damage assessed by the Comet assay. These data suggest that clinical radiation may provoke genetic instability and/or induce persistent DNA damage in normal cells of cancer patients, thus leading to increased levels of MN induction and DNA fragmentation after irradiation in vitro. Therefore, care has to be taken when blood samples collected postradiotherapeutically are used to assess the radiosensitivity of cancer patients.     

Low-dose-rate brachytherapy is superior to high-dose-rate brachytherapy for bladder cancer

PURPOSE: To determine the efficacy and safety of a high-dose-rate (HDR) brachytherapy schedule in the treatment of bladder cancer and to investigate the impact of different values of repair half-times and alpha/beta ratios on the design of the HDR schedule. METHODS AND MATERIALS: Between 2000 and 2002, 40 patients with T1G3 and T2 bladder carcinoma were treated with 30 Gy external beam radiotherapy followed by interstitial HDR brachytherapy to a total dose of 32 Gy in 10 sessions of 3.2-Gy fractions in two fractions daily with a 6-h interfraction interval. The local control rate and toxicity were compared with a historical group of 108 patients treated with 30 Gy external beam radiotherapy followed by 40-Gy interstitial low-dose-rate (LDR) brachytherapy. The HDR schedule was designed to be biologically equivalent to the previously used LDR schedule with the linear-quadratic model, including incomplete mono-exponential repair. RESULTS: The local control rate at 2 years was 72% for HDR vs. 88% for LDR brachytherapy (p = 0.04). In the HDR group, 5 of 30 evaluable patients encountered serious late toxicity: 4 patients developed a contracted bladder with inadequate capacity (<100 mL), and 1 patient required cystectomy because of a painful ulcer at the implant site. In the LDR group, only 2 of 84 assessable patients developed serious late toxicity. One patient developed a persisting vesicocutaneous fistula and the other a urethral stricture due to fibrosis. The difference in observed late toxicity for HDR vs. LDR was statistically significant (p = 0.005). The increased late toxicity with the HDR schedule compared with the LDR schedule suggests a short repair half-time of 0.5-1 h for late-responding normal bladder tissue. CONCLUSION: Local control of HDR brachytherapy for bladder cancer was disappointing and late toxicity unexpectedly high. The increase in late toxicity suggested a short repair half-time of 0.5-1 h for late-responding normal bladder tissue, which would not support HDR brachytherapy in the treatment of bladder cancer. The analysis demonstrated that the calculation of equivalent HDR schedules on the basis of the LDR schedules used in clinical practice might be hazardous.     

Present and future in brachytherapy--from the discovery of radium to the 21st century]

Brachytherapy can deliver high doses of radiation to a tumor with only low doses to the normal tissue. Brachytherapy can be classified as intracavitary, intraluminar and interstitial radiotherapy. It can be also divided into three groups according to dose rate: low (LDR), medium (MDR) and high (HDR) dose rates. In recent years, HDR remotely controlled afterloading systems are widespread in Japan. HDR brachytherapy has solved the problem of radiation exposure for medical staff, and patients need not be isolated in highly sealed rooms. Local control rates of T1 and T2 tongue cancer treated with LDR interstitial radiation using 226Ra and 192Ir were 80% and 67%. A phase III trial of HDR versus LDR interstitial brachytherapy for early tongue cancer revealed the same local control rates between the two groups. For uterine cervix cancer, the cause-specific survival rates of patients treated with HDR intracavitary brachytherapy were almost the same as those treated with LDR. HDR brachytherapy can be applied against recurrent tumors. Almost half of recurrent tumors can be controlled with HDR treatment. Brachytherapy is widely used for prostate cancer in the USA. LDR brachytherapy using 125I seeds is used for prostate cancer. In Japan, 125I seeds can not be used because of the regulation of radioisotopes, so we treat prostate cancer patients with HDR brachytherapy. The two-year biochemical NED rate is 83%. Brachytherapy has a long history of nearly 100 years. In recent years, the development of an HDR remotely controlled afterloading system and treatment planning system allows us to make a precise treatment plan and a uniform dose distribution. In the next century, HDR-brachytherapy will continue to play an important role in the field of radiotherapy.     

Phase II trial of brachytherapy alone after lumpectomy for select breast cancer: toxicity analysis of RTOG 95-17

PURPOSE: Accelerated partial breast irradiation (APBI) can be delivered with brachytherapy within 4-5 days compared with 5-6 weeks for conventional whole breast external beam radiotherapy. Radiation Therapy Oncology Group 95-17 is the first prospective phase I-II cooperative group trial of APBI alone after lumpectomy in select patients with breast cancer. The toxicity rates are reported for low-dose-rate (LDR) and high-dose-rate (HDR) APBI on this trial. METHODS AND MATERIALS: The inclusion criteria for this study included invasive nonlobular tumors < or =3 cm after lumpectomy with negative surgical margins and axillary dissection with zero to three positive axillary nodes without extracapsular extension. The patients were treated with either LDR APBI (45 Gy in 3.5-5 days) or HDR APBI (34 Gy in 10 twice-daily fractions within 5 days). Chemotherapy (> or =2 weeks after APBI) and/or tamoxifen could be given at the discretion of the treating physicians. RESULTS: Between August 1997 and March 2000, 100 women were enrolled in this study, and 99 were evaluated. Of the 99 women, 33 were treated with LDR and 66 with HDR APBI. The median follow-up for all patients was 2.7 years (range, 0.6-4.4 years) and was 2.9 years for LDR and 2.7 years for HDR patients. Toxicities attributed to APBI included erythema, edema, tenderness, pain, and infection. Of the 66 patients treated with HDR APBI, 2 (3%) had Grade 3 or 4 toxicity. Of the 33 patients treated with LDR, 3 (9%) had Grade 3 or 4 toxicity during brachytherapy. Late toxicities included skin thickening, fibrosis, breast tenderness, and telangiectasias. No patient experienced late Grade 4 toxicity; the rate of Grade 3 toxicity was 18% for the LDR and 4% for the HDR groups. CONCLUSION: Acute and late toxicity for this invasive breast radiation technique was modest and acceptable. Patients receiving chemotherapy, a nonprotocol therapy, had a greater rate of Grade 3 toxicity. The study design did not allow for this to be tested statistically.     

Enhanced chromosomal radiosensitivity in peripheral blood lymphocytes of larynx cancer patients

PURPOSE: The chromosomal radiosensitivity in peripheral blood lymphocytes of cancer patients was reported to be higher than that of healthy donors. This effect is especially prominent when aberrations induced in the G2 phase of the cell cycle are analyzed. The aim of our study was to investigate if the G2 aberration frequencies in lymphocytes of patients with larynx cancer are higher than in the case of control individuals. Also, we tested if the frequencies of G2 aberrations correlate with side effects of radiotherapy. METHODS AND MATERIALS: Peripheral blood of 38 patients was collected before the onset of radiotherapy, cultured for 72 h, and irradiated with 2 Gy after 67 h. Lymphocytes of 40 healthy donors were treated in the same way. RESULTS: The spontaneous and radiation-induced aberration frequencies in lymphocytes of patients were on average higher than in those of healthy donors. No statistically significant correlation was observed between aberration frequencies in lymphocytes and the degree of both early and late normal tissue reactions. CONCLUSIONS: The chromosomal radiosensitivity of lymphocytes of patients with larynx cancer may be a marker of cancer predisposition; however, it does not appear to have a predictive value for the risk of developing side effects to radiotherapy.     

High-dose-rate brachytherapy may be radiobiologically superior to low-dose rate due to slow repair of late-responding normal tissue cells

BACKGROUND AND PURPOSE: Recent analysis of morbidity for patients treated with the continuous hyperfractionated accelerated radiotherapy (CHART) regimen demonstrates that repair half-times for late-reacting normal tissue cells are of the order of 4-5 h, which is considerably longer than previously believed. This would reduce repair of these tissue cells during a course of low-dose rate (LDR) brachytherapy, but have no effect at high-dose-rate (HDR), where there is no repair during, and full repair between fractions, regardless of repair half-time. The effect this has upon radiobiologic comparison of LDR and HDR is the topic of this paper. METHODS AND MATERIALS: The linear-quadratic (L-Q) model is used to compare late-effect biologically effective doses (BEDs) of LDR and HDR, for constant BED (tumor). The effects of dose rate (for LDR), fractionation (for HDR), and geometrical sparing of normal tissues are all considered. Repair half-times observed in the CHART study are used to investigate the potential impact of long repair times on the comparison of LDR and HDR. RESULTS: It is demonstrated that, for a repair half-time of 1.5 h for tumor cells, if the half-time for repair of late-reacting normal tissue cells exceeds about 2.5 h, LDR becomes radiobiologically inferior to HDR. Even with the least HDR-favorable combinations of parameters, HDR at over about 5 Gy/fraction ought to be radiobiologically superior to LDR at 0.5 Gy/h, so long as the time between HDR fractions is long compared to the repair half time. It is also shown that any geometrical sparing of normal tissues will benefit HDR more than LDR. CONCLUSION: The previously held belief that LDR must be inherently superior radiobiologically to HDR is wrong if the long repair times demonstrated in the recent CHART study are applicable to other late-reacting normal tissues. This could explain why HDR has been so successful in clinical practice, especially for the treatment of cervical cancer, despite previous convictions of radiobiologic inferiority of this modality.     

Individual radiosensitivity measured with lymphocytes may predict the risk of acute reaction after radiotherapy

PURPOSE: We tested whether the chromosomal radiosensitivity of in vitro irradiated lymphocytes could be used to predict the risk of acute reactions after radiotherapy. METHODS AND MATERIALS: Two prospective studies were performed: study A with 51 patients included different tumor sites and study B included 87 breast cancer patients. Acute reaction was assessed using the Radiation Therapy Oncology Group score. In both studies, patients were treated with curative radiotherapy, and the mean tumor dose applied was 55 Gy (40-65) +/- boost with 11 Gy (6-31) in study A and 50.4 Gy +/- boost with 10 Gy in study B. Individual radiosensitivity was determined with lymphocytes irradiated in vitro with X-ray doses of either 3 or 6 Gy and scoring the number of chromosomal deletions. RESULTS: Acute reactions displayed a typical spectrum with 57% in study A and 53% in study B showing an acute reaction of Grade 2-3. Individual radiosensitivity in both studies was characterized by a substantial variation and the fraction of patients with Grade 2-3 reaction was found to increase with increasing individual radiosensitivity measured at 6 Gy (study A, p = 0.238; study B, p = 0.023). For study B, this fraction increased with breast volume, and the impact of individual radiosensitivity on acute reaction was especially pronounced (p = 0.00025) for lower breast volume. No such clear association with acute reaction was observed when individual radiosensitivity was assessed at 3 Gy. CONCLUSION: Individual radiosensitivity determined at 6 Gy seems to be a good predictor for risk of acute effects after curative radiotherapy.     

Results of low- and high-dose-rate interstitial brachytherapy for T3 mobile tongue cancer.

PURPOSE: To evaluate the treatment results of low-dose-rate (LDR) and high-dose-rate (HDR) interstitial brachytherapy (ISBT) for T3 mobile tongue cancer. MATERIAL AND METHODS: Between 1974 and 1992, 61 patients with T3 mobile tongue cancer were treated with LDR ISBT using (192)Ir hairpins with or without single pins. In addition, between 1991 and 1999, 14 patients were treated with HDR ISBT. For nine patients treated with ISBT alone, the total dose was 59-94 Gy (median 72 Gy) within one week in LDR ISBT and 60 Gy/10 fractions/5 days in HDR ISBT. For 66 patients treated with a combination therapy of external beam radiotherapy (EBRT) and ISBT, the total dose was 12.5-60 Gy (median 30 Gy) of EBRT and 50-112 Gy (median 68 Gy) within 1 week in LDR ISBT or 32-60 Gy (median 48 Gy)/8-10 fractions/5-7 days in HDR ISBT. RESULTS: The 2- and 3-year local control rates of all patients were both 68%. The 2- and 3-year local control rates of patients treated with LDR ISBT were both 67%, and those with HDR ISBT were both 71%. The local control rate of patients treated with HDR ISBT was similar to those with LDR ISBT. CONCLUSIONS: ISBT for T3 mobile tongue cancer is effective and acceptable. The treatment result of HDR ISBT is almost similar to that of LDR ISBT for T3 mobile tongue cancer.     

Chromosomal instability and radiosensitivity in myelodysplastic syndrome cells.

Myelodysplastic syndrome (MDS) is a clonal disorder of hematopoietic stem cells. To investigate whether chromosomal instability and/or DNA repair defects are involved in the development of MDS, we measured the micronucleus (MN) frequency in peripheral blood lymphocytes exposed to various doses of X-rays, using a cytokinesis-block micronucleus assay. The spontaneous MN frequencies in RAEB and RAEB-T patients were significantly higher than those in normal individuals (P = 0.0224, P = 0.008, respectively). Also, the X-ray-induced MN frequencies in RA/RARS, RAEB, and RAEB-T patients were significantly higher than those in normal individuals (P = 0.007, P = 0.003, P = 0.003, respectively, at 2 Gy). In order to elucidate the cause of unusual radiosensitivity, we measured the expression levels of nucleotide excision repair (NER) genes in peripheral blood mononuclear cells using a RT-PCR method. Reduction of NER gene expression was found in only one of 10 patients with low risk MDS, but in four of 11 patients with high risk MDS. Our data suggest that chromosomal instability and DNA repair defects may be involved in the pathophysiology of disease progression of MDS.     

Phase III trial of high and low dose rate interstitial radiotherapy for early oral tongue cancer

: Oral tongue carcinomas are highly curable with radiotherapy. In the past, patients with tongue carcinoma have usually been treated with low dose rate (LDR) interstitial radiation. This Phase III study was designed to compare the treatment results obtained with LDR with those obtained with high dose rate (HDR) interstitial radiotherapy for tongue carcinoma.

: The criteria for patient selection for the Phase III study were: (a) presence of a T1T2N0 tumor that could be treated with single-plane implantation, (b) localization of tumor at the lateral tongue border, (c) tumor thickness of 10 mm or less, (d) performance status between O and 3, and (e) absence of any severe concurrent disease. From April 1992 through December 1993, 15 patients in the LDR group (70 Gy/4 to 9 days) and 14 patients in the HDR group (60 Gy/10 fractions/6 days) were accrued. The time interval between two fractions of the HDR brachytherapy was more than 6 h.

: Local recurrence occurred in two patients treated with LDR brachytherapy but in none of the patients treated with HDR. One- and 2-year local control rates for patients in the LDR group were both 86%, compared with 100% in the HDR group (p = 0.157). There were four patients with nodal metastasis in the LDR group and three in the HDR group. Local recurrence occurred in two of the four patients with nodal metastases in the LDR group. One- and 2-year nodal control rates for patients in LDR group are were 85, compared with 79% in the HDR group.

: HDR fractionated interstitial brachytherapy can be an alternative to traditional LDR brachytherapy for early tongue cancer and eliminate the radiation exposure for medical staffs.     

Radiation-induced micronuclei in human fibroblasts in relation to clonogenic radiosensitivity.

As part of our programme for developing predictive tests for normal tissue response to radiotherapy, we have investigated the efficacy of the cytokinesis-block micronucleus (MN) assay as a means of detecting interindividual differences in cellular radiosensitivity. A study was made of nine fibroblast strains established from vaginal biopsies of pretreatment cervical cancer patients and an ataxia telangiectasia (A-T) cell strain. Cells were irradiated in plateau phase, replated and treated with cytochalasin B 24 h later. MN formation was examined 72 h after irradiation as the number of MN in 100 binucleate cells. The method yielded low spontaneous MN yields (<7 per 100 cells), and mean induced MN frequencies after 3.5 Gy varied between cell strains from 18 to 144 per 100 cells. However, in repeat experiments, considerable intrastrain variability was observed (CV = 32%), with up to twofold differences in MN yields, although this was less than interstrain variability (CV = 62%). An analysis was made of the relationship between MN results and previously obtained clonogenic survival data. There was a significant correlation between MN yields and clonogenic survival. However, when the A-T strain was excluded from the analysis, the correlation lost significance, mainly because of one slow-growing strain which was the most sensitive to cell killing but had almost the lowest MN frequency. With current methodology, the MN assay on human fibroblasts does not appear to have a role in predictive testing of normal tissue radiosensitivity.     

Individual radiosensitivity measured with lymphocytes may be used to predict the risk of fibrosis after radiotherapy for breast cancer.

BACKGROUND AND PURPOSE: To analyse the relationship of individual cellular radiosensitivity and fibrosis after breast conserving therapy. A new model was used describing the percentage of patients developing fibrosis per year and per patient at risk. PATIENTS AND METHODS: In a retrospective study, 86 patients were included, who had undergone breast conserving surgery and irradiation of the breast with a median dose of 55 Gy (54-55 Gy) given at 2.5 Gy/fraction (n=57) or 2 Gy/fraction (n=29). Median age was 62 years (range 44-86) and median follow-up was 7.5 years (range 5-17). Patients were examined for fibrosis according to the LENT/SOMA score. For analysis, fibrosis was classified as grade 0 and grade 1 (G0-1) or present grade 2 and grade 3 (G2-3). The time to complete development of fibrosis was determined by analysis of yearly mammograms. Individual cellular radiosensitivity was determined by scoring lethal chromosomal aberrations in in vitro irradiated (6 Gy) lymphocytes using metaphase technique. Patients with low/intermediate cellular radiosensitivity were compared with patients with high cellular radiosensitivity using actuarial methods. RESULTS: Ten patients developed fibrosis at 1-8 years after radiotherapy. Individual cellular radiosensitivity was described by normal distribution of lethal chromosomal aberrations, the average was 5.47 lethal aberrations per cell (standard deviation (SD) 0.71). Cellular radiosensitivity was defined as low/intermediate (< or =6.18 lethal aberrations) in 73 patients and high (>6.18 lethal aberrations; mean+SD) in 13 patients. In both groups, the actuarial rate of fibrosis-free patients decreased exponentially with time after radiotherapy. Patients with high cellular radiosensitivity showed a 2.3-fold higher annual rate for fibrosis than patients with intermediate and low radiosensitivity (3.6 versus 1.6% per year). CONCLUSIONS: In breast cancer patients, high individual cellular radiosensitivity as determined by the number of lethal chromosome aberrations in in vitro irradiated lymphocytes might be associated with an enhanced annual rate of fibrosis.