Poor vision accompanied with other sensory impairments as a predictor of falls in older women

OBJECTIVES

we studied visual acuity (VA) and co-existing hearing impairment and poor standing balance as predictors of falls.

DESIGN

prospective study with 1-year follow-up.

SETTING

research laboratory and residential environment.

PARTICIPANTS

428 women aged 63-76 years from the Finnish Twin Study on Aging.

MEASUREMENTS

participants were followed up for incidence of falls over 1 year. VA, hearing ability and standing balance were assessed at the baseline. The incidence rate ratios (IRR) for falls were computed using the negative binomial regression model.

RESULTS

during the follow-up, 47% of participants experienced a fall. After adjusting for age and interdependence of twin sisters, participants with vision impairment (VA of <1.0) but no other sensory impairments had a higher, but non-significant, risk for falls compared to persons with normal vision (IRR 1.5, 95% CI 0.6-4.2). Co-existing vision impairment and impaired balance increased the risk (IRR 2.7, 95% CI 0.9-8.0), as also did co-existing vision and hearing impairment (IRR 4.2, 95% CI 1.5-11.3), compared to those with normal vision. Among persons with all three impairments, the IRR for falls increased to 29.4 (95% CI 5.8-148.3) compared to participants with good vision.

CONCLUSION

the impact of vision impairment on fall risk was higher when accompanied with other sensory and balance impairments, probably because the presence of other impairments prevented the reception of compensatory information about body posture and environment being received from other sensory sources. When aiming to prevent falls and their consequences in older people, it is important to check whether poor vision is accompanied with other impairments.

Osteodistraction of a previously irradiated mandible with or without adjunctive hyperbaric oxygenation: an experimental study in rabbits

The purpose of this study was to analyse the effects of irradiation and hyperbaric oxygenation (HBO) on mandibular osteodistraction (OD). Eighteen rabbits were divided into three groups: 1. Irradiation (R), 2. Irradiation+HBO (R-HO), and 3. Control group (C). Animals of groups R and R-HO received in the mandible irradiation 22.4 Gy in four 5.6 Gy fractions (equivalent to 50 Gy/25 fractions). In addition, group R-HO was given HBO at 2.5 ATA for 90 min per day 18 times preoperatively. Unilateral osteotomy was made 1 month after completion of radiotherapy. After a 1 week latency period bone distraction was started at rate of 1 mm per day, continued for 2 weeks, and left to consolidate for 4 weeks. Amount of new bone was measured histomorphometrically from midsagittal sections. Area of new bone was equal in all groups. Bone was more mature and bone spicules better organized in group C than in groups R and R-HO. Cartilaginous cells were found in distracted bone in all groups but larger chondroid islands were evident only in group R. It seems that despite delayed bone formation, OD can be performed after radiotherapy. HBO had a beneficial effect on bone quality of a previously irradiated mandible.

Disturbances in craniofacial morphology in children treated for solid tumors

Because of increased survival rates in childhood cancer, special interest has been focused on the side-effects of the therapy and the quality of life in long-term survivors. Our aim was to investigate craniofacial growth in children who had received different kinds of antineoplastic therapies for solid tumors. A total of 40 children treated in the Turku University Central Hospital were examined and divided into three different groups. Group 1 comprised 18 children treated for intracranial tumors with cranial irradiation (CRI) and chemotherapy (CT) including alkylating agents. Seven children out of 18 in this group received growth hormone (GH) therapy. In Group 2, 11 children with extracranial solid tumors also received multiagent CT including alkylating agents, but no CRI. Group 3 consisted of 11 children treated for Wilm's tumor with CT, which did not include alkylating agents or CRI. A total of 19 linear and four angular variables from the lateral cephalograms of the subjects were measured. Most deviations in craniofacial structures were found in children treated with combined CRI and multiagent CT. All disturbances were seen in the vertical measurements which were reduced when compared to the matched controls. It seems reasonable to assume that impaired growth following combined radio- and chemotherapy, as well as GH treatment, particularly affects cartilage-mediated growth. However, the deviations seen in the present study were fairly minor and did not usually require clinical consideration.

Radiotherapy treatment planning and long-term follow-up with [(11)C]methionine PET in patients with low-grade astrocytoma

PURPOSE

To evaluate the feasibility of [(11)C]-methionine positron emission tomography (MET PET) in radiotherapy (RT) treatment planning and long-term follow-up in patients with low-grade glioma.

PATIENTS

Thirteen patients with low-grade astrocytoma and 1 with anaplastic astrocytoma underwent sequential MET PET and magnetic resonance imaging (MRI) before and 3, 6, 12, and 21-39 months after RT, respectively. Ten patients were studied after initial debulking surgery or biopsy and 4 in the recurrence phase.

METHODS

A total of 58 PET scans were performed. After transmission scanning, a median dose of 425 MBq of MET was injected intravenously and emission data was acquired 20 min after injection for 20 min. The uptake of MET in tumor area was measured as standardized uptake value (SUV) and tumor-to-contralateral brain SUV ratios were generated to assess irradiation effects on tumor metabolism. Functional imaging with PET was compared with concurrent MRI in designing the RT planning volumes and in assessment of response to RT during a median follow-up time of 33 months.

RESULTS

In 12 patients (86%), tumor area was clearly discernible in the baseline PET study. In the remaining 2 patients with a suspected residual tumor in MRI, PET showed only a diffuse uptake of MET interpreted as negative in the original tumor area. In the dose planning of RT, MET PET was helpful in outlining the gross tumor volume in 3 of 11 cases (27%), whereas PET findings either coincided with MRI (46%) or were less distinctive (27%) in other cases. In quantitative evaluation, patients with a low tumor SUV initially had significantly better prognosis than those with a high SUV. Tumor-to-contralateral brain uptake ratios of MET discriminated well patients remaining clinically stable from those who have since relapsed or died of disease.

CONCLUSION

Quantitative MET PET has prognostic value at the time of initial treatment planning of low-grade glioma. Some patients may benefit of RT volume definition with MET PET, which seems to disclose residual tumor better than MRI in selected cases. Stable or decreasing uptake of MET in tumor area after RT during follow-up seems to be a favorable sign.

Adhesion of inactivated probiotic strains to intestinal mucus

It has been suggested that probiotics should be viable in order to elicit beneficial health effects. Inactivation of probiotics has been suggested to interfere with the binding to the mucosa and thereby with the immune modulating activity of probiotics. The effect of different inactivation methods on the mucus adhesion of nine probiotic strains was studied. Inactivation by heat or gamma-irradiation generally decreased the adhesive abilities. However, heat treatment increased the adhesion of Propionibacterium freudenreichii and gamma-irradiation enhanced the adhesion of Lactobacillus casei Shirota. Inactivation by u.v. was not observed to modulate the adhesion of the tested strains and it was concluded to be the most appropriate method for studying non-viable probiotics and preparing control products.

The effect of irradiation on mitotic and apoptotic frequency in head and neck cancer cell lines, the correlation to p53 mutations and clonogenic survival

It was our intention to enlighten the controversy between the mainstream of studies and our previous results showing a correlation between the intrinsic radiosensitivity and the p53 allele status of 20 human head and neck squamous cell carcinoma (HNSCC) cell lines. In our study cell lines carrying a wild-type (WT) p53 allele were significantly more radioresistant than cell lines which lacked a WT gene. We observed nine HNSCC cell lines with known intrinsic radiosensitivity and p53 allele status with time-lapse video microscopy after irradiation with 2 and 3 Gy. We studied the mitotic and apoptotic frequencies and scored the apoptoses as to whether they occurred morphologically in mitosis or in interphase. Irradiation with 2 or 3 Gy did not induce apoptosis in the cell lines studied. As expected the mitotic frequency was reduced by the irradiation. This was statistically significant in the cell lines which were radiosensitive when measured with a clonogenic assay. p53 allele status did not have an independent effect on the cell lines, except that the irradiation favoured the apoptosis in mitosis in the cell lines with WT p53 and the apoptosis in the interphase in the cell lines with a mutated or non-functional p53 gene. We conclude that although the apoptosis is not induced by irradiation with 2 Gy or 3 Gy, the p53 suppressor gene seems to influence the process of apoptosis after irradiation in the cell lines studied.

Genome size variation in Hordeum spontaneum populations

Populations of wild barley, Hordeum spontaneum (C. Koch), originating from 10 ecologically and geographically different sites in Israel, were assessed for genome size. Measurements were obtained by flow cytometry using propidium iodide staining. Genome sizes ranged from 9.35 to 9.81 pg. Variance analysis indicated a significant difference between populations. Genome sizes were positively correlated with mean January temperature. Our results corroborate previous findings of intraspecific variation in genome size from different plant species. The positive correlations between climate and genome size suggest that the latter is adaptive and determined by natural selection.

Carboplatin-paclitaxel- and carboplatin-docetaxel-induced cytotoxic effect in epithelial ovarian carcinoma in vitro

BACKGROUND

The combination of paclitaxel and cisplatin is standard for patients with newly diagnosed epithelial ovarian carcinoma. The role of another taxane, docetaxel, currently is being studied. Due to its milder nonhematologic toxicity carboplatin increasingly is being substituted for cisplatin in taxane-based combinations. The purpose of this study was to compare the combination of carboplatin-paclitaxel with carboplatin-docetaxel in ovarian carcinoma in vitro, and to assess the type of interaction, if any.

METHODS

Sensitivity to carboplatin and the concomitant use of a taxane and carboplatin was studied in 4 ovarian carcinoma cell lines using the 96-well plate clonogenic assay. Chemosensitivity was expressed as the IC50 value (i.e., the drug concentration causing 50% inhibition of clonogenic survival). IC50 values were obtained from dose-response curves after fitting the data to the linear quadratic equation. Synergism was studied by the area under the survival curve ratios (AUC ratios), obtained by numeric integration. The AUC ratio and the surviving fraction (SF) value after the administration of taxane alone were compared using the Student t test for paired data.

RESULTS

The IC50 values for carboplatin were between 0.5-1.6 microgram/mL; there was only a 3.2-fold difference between individual cell lines. Carboplatin administered concomitantly with a taxane had either an additive or supra-additive growth inhibitory effect on all four ovarian carcinoma cell lines. A supra-additive effect occurred after simultaneous exposure of the cells to carboplatin at all tested paclitaxel concentrations in three of four cell lines (UT-OC-3, UT-OC-5, and SK-OV-3). The carboplatin-docetaxel combination had a supra-additive effect at the two highest docetaxel concentrations in two cell lines (UT-OC-4 and UT-OC-5) and at the highest docetaxel concentration in the other two cell lines (UT-OC-3 and SK-OV-3).

CONCLUSIONS

Carboplatin has a synergistic effect when used with paclitaxel or docetaxel. A supra-additive effect is achieved with a wider range of paclitaxel concentrations than docetaxel concentrations.

Effects of paclitaxel with or without cremophor EL on cellular clonogenic survival and apoptosis

Paclitaxel is currently formulated in a vehicle of 50% ethanol and 50% polyethoxylated surfactant cremophor EL. Cremophor EL has been reported to reverse P-glycoprotein-mediated multidrug resistance (MDR) at doses which are clinically achievable. It has also been reported to have a cytotoxic effect per se. In this study we used two different methods to evaluate the survival of cells exposed to paclitaxel with or without cremophor EL and the vehicle alone. Two laryngeal SCC cell lines (UT-SCC-19A and UT-SCC-29) and two ovarian adenocarcinoma cell lines (UT-OC-3 and UT-OC-5) established in our laboratory were investigated. Northern hybridisation was used to study the mdr-1 mRNA expression of the cell lines. With sensitive Northern analyses, these four lines yielded mdr-1 mRNA signals of the expected 4.5 kb size and of variable intensity, generally at higher levels than those in the positive control cell line KB. The 96-well plate clonogenic assay was used to obtain the fraction survival data and apoptosis was recorded by time-lapse video microscopy. Both methods indicate that cremophor EL alone has no effect on cellular survival. Consequently, paclitaxel without cremophor EL is as active as paclitaxel with cremophor EL in vitro.

Characterization of prethymic progenitors within the chicken embryo

The thymic primordium in both birds and mammals is first colonized by cells emerging from the intra-embryonic mesenchyme but the nature of these precursors is poorly understood. We demonstrate here an early embryonic day 7 prethymic population with T lymphoid potential. Our work is a phenotypic analysis of, to date, the earliest embryonic prethymic progenitors arising in the avian para-aortic area during ontogeny. The phenotype of these cells, expressing the cell surface molecules alpha2beta1 integrin, c-kit, thrombomucin/MEP21, HEMCAM and chL12, reflects functional properties required for cell adhesion, migration and growth factor responsiveness. Importantly, the presence of these antigens was found to correlate with the recolonization of the recipient thymus following intrathymic cell transfers. These intra-embryonic cells were also found to express the Ikaros transcription factor, the molecular function of which is considered to be prerequisite for embryonic lymphoid development.

Additive and supra-additive cytotoxicity of cisplatin-taxane combinations in ovarian carcinoma cell lines

The purpose of this study was to compare the growth-inhibitory effect of cisplatin-paclitaxel with that obtained with a cisplatin-docetaxel combination and to assess the type of interaction. Concomitant use of taxanes and cisplatin was studied in seven human ovarian carcinoma cell lines, using the 96-well plate clonogenic assay. Chemosensitivity was expressed in terms of IC50 values, the drug concentration causing 50% inhibition of clonogenic survival. The type of interaction was studied using the area under the survival curve ratios (AUC ratios) obtained by numerical integration. Comparison of the AUC ratio and the surviving fraction (SF) value after taxane alone was made using Student's t-test. The influence of the drug concentration was tested by one-way analysis of variance (Anova). A supra-additive or additive effect was seen when seven ovarian carcinoma cell lines were exposed to paclitaxel or docetaxel concomitantly with cisplatin. A supra-additive effect was found in four cell lines (UT-OC-3, UT-OC-4, UT-OC-5 and SK-OV-3) after simultaneous use of cisplatin with all docetaxel concentrations tested, and in two cell lines (UT-OC-4 and SK-OV-3) when cisplatin was used concomitantly with paclitaxel. A more pronounced supra-additive effect was seen with the combination of cisplatin and docetaxel. The degree of supra-additivity was dose dependent, with increasing synergy after a higher taxane dose. The data obtained in this study suggest that a supra-additive or additive effect can be achieved in ovarian carcinoma with the concomitant use of cisplatin and a taxane.

Radiosensitivity of dermal and tumor fibroblasts derived from the same patient

The in vitro radiosensitivity of dermal fibroblasts has been found to vary between individuals, and a number of studies have also shown that this parameter correlates with radiation-induced late injuries in clinical radiotherapy. In addition, certain genetic disorders are known to effect radiosensitivity, e.g. normal tissues of patients homozygous or heterozygous for the ataxia teleangiectasia gene show unusual sensitivity to radiation both in vivo and in vitro. Thus, it has been assumed that there is a genetically determined component resulting in a certain intrinsic cellular radiation response in an individual. To study this possible relationship between different cells of a specific patient, we established eight pairs of dermal and tumor fibroblast cultures. The donor patients had either adenocarcinoma of the uterus or squamous cell carcinoma (SCC) of the head and neck. The radiosensitivity of these strains was determined by a 96-well plate clonogenic assay, previously used by us for radiosensitivity testing of cancer cells. From a paired comparison, the values for the cell fraction surviving 2.0 Gy (SF2), of both fibroblast strains, were found to be on the same level in five out of eight cases. In patient 6, the SF2 of tumor fibroblasts was significantly higher than that of dermal fibroblasts (P=0.0014). In two additional cases the tendency was the same, but not statistically significant. As groups, the two types of fibroblasts did not differ from each other, mean SF2 values of 0.24+/-0.07 and 0.21+/-0.05, respectively. The SF2 of tumor fibroblasts from SCC patients proved to be significantly higher than that of the adenocarcinoma patients (P=0.030). These preliminary results indicate that the in vitro radiosensitivity of tumor fibroblasts correlates with normal cell sensitivity in many cases, but not in all. The radiosensitivity of tumor fibroblasts also seems to follow the level of in vitro radiosensitivity determined for the corresponding histological type of tumor cells. Further studies are needed to determine more closely the relationship between the radiosensitivities of tumor cells and tumor fibroblasts, thus evaluating the possibility of testing radiosensitivity from tumor fibroblasts in order to estimate tumor response.

Taxane sensitivity of ovarian carcinoma in vitro

Paclitaxel, the first clinically available taxane, has proven to be effective in the treatment of ovarian carcinoma. Docetaxel is the second taxoid derivative which has also shown activity in ovarian carcinoma. These two compounds have clear differences in pharmacokinetics and side-effects. In the present study we have tested the cytotoxic effect of docetaxel in seven ovarian carcinoma cell lines using the 96-well plate clonogenic assay. These results have been compared with data obtained from our recent study on cisplatin and paclitaxel sensitivities of the same cell lines. Chemosensitivity has been expressed as IC50 value, the drug concentration causing 50% inhibition of clonogenic survival. The IC50 values for docetaxel were 0.23-2.30 nM showing a 10-fold difference between individual cell lines. On a molar basis, docetaxel was 1.2 to 2.6 times more active than paclitaxel in six out of seven cell lines. This may be explained by differences in the mechanism of action or by differences in other pharmacological properties.

Vulvar squamous cell carcinoma cell lines are sensitive to paclitaxel in vitro

In the current study, paclitaxel sensitivity of eight vulvar squamous cell carcinoma (SCC) cell lines was tested using a 96-well plate clonogenic assay. The chemosensitivity was expressed as IC50 corresponding to the drug concentration causing 50% inhibition in clonogenic survival. IC50 values were obtained from dose-response curves after fitting the data to the linear quadratic equation. The paclitaxel sensitivity of the eight vulvar SCC cell lines expressed as IC50 varied from 0.6 to 2.9 nM. The observed differences between the individual cell lines were surprisingly small, only 4.8-fold at the most. Paclitaxel sensitivity of vulvar SCC cell lines is of the same magnitude as the paclitaxel sensitivity of endometrial and ovarian carcinoma cell lines tested in our preliminary experiments with the same assay. We have previously studied the intrinsic radiosensitivity of these vulvar SCC cell lines. No correlation could be found between radiosensitivity and paclitaxel sensitivity. These results indicate that vulvar SCC is consistently sensitive to paclitaxel in vitro. The role of chemotherapy in the treatment of vulvar carcinoma has not been clarified yet. The efficacy of paclitaxel should be tested further in clinical trials.

Paclitaxel and cisplatin sensitivity of ovarian carcinoma cell lines tested with the 96-well plate clonogenic assay

Platinum based chemotherapy is the cornerstone of treatment in advanced ovarian carcinoma. Paclitaxel, an unique antimicrotubule agent has shown significant clinical activity in cisplatin-resistant tumours, indicating a lack of cross-resistance. To compare the in vitro sensitivity of ovarian carcinoma to cisplatin and paclitaxel, we tested 7 ovarian carcinoma cell lines with the 96-well plate clonogenic assay. Chemosensitivity was expressed as the IC50 value i.e. the drug concentration causing 50% inhibition of clonogenic survival. IC50 values were obtained from dose-response curves after fitting the data to the linear quadratic equation. The IC50 values for paclitacel were 0.4-3.4 nM, showing an 8.5-fold difference between various cell lines. The IC50 values for cisplatin were 0.1-0.45 ug ml-1 showing only a 4.5-fold difference. This variance is clearly smaller than the 25-fold difference observed with the same method in endometrial carcinoma cell lines (Rantanen et al, Br J Cancer 69: 482-86, 1994). In accordance with clinical findings, no cross-resistance or correlation between sensitivity to paclitaxel and cisplatin could be demonstrated.

Stage-specific apoptosis in the rat seminiferous epithelium: quantification of irradiation effects

The effects of 3 Gy local X-irradiation on the adult rat testis were studied together with exact determination of the radiation dose distribution in the testis. Seminiferous tubule segments were isolated 8-66 hours postirradiation (p.i.), squashed between a microscope slide and a coverslip, and the exact stage of the seminiferous epithelial cycle was identified under a phase-contrast microscope. The squash preparations were subjected to in situ end labeling (ISEL) for visualization and quantification of apoptotic cells. In controls, the highest numbers of apoptotic cells were scored in stages XII-XIV and I. In situ end-label staining of cells was observed in A3-A4 spermatogonia, spermatocytes at zygotene, pachytene, and meiotic division phases, as well as in early spermatids. In irradiated testes, from 8 hours p.i. and onward, intermediate- and B-type spermatogonia were sensitive at stages II-VI. At 42 hours, in stage I, elevated numbers of degenerating spermatocytes were seen. Most of them had not undergone meiotic divisions at stage XIV and showed an apoptotic type of degeneration at stage I. At the time of irradiation, the cells were in stage XIII, suggesting that diakinetic spermatocytes are particularly sensitive to irradiation. Also, preleptotene-zygotene spermatocytes in stages VII-XII were sensitive to irradiation. Apoptotic-type of cell degeneration was confirmed by living cell squash preparations, electron microscopy, and DNA electrophoresis. In conclusion, irradiation may provide a useful model system for studying apoptosis, and its control in spermatogonia and meiotically dividing cells.

In vitro concurrent paclitaxel and radiation of four vulvar squamous cell carcinoma cell lines

BACKGROUND

The antitubule agent paclitaxel causes a cell cycle blockage in the most radiosensitive part of the cell cycle, the G2/M phase. The possible radiosensitizing effect of paclitaxel was tested in four vulvar (UM-SCV-1A, UM-SCV-1B, UM-SCV-2, and UM-SCV-4) squamous cell carcinoma (SCC) cell lines.

METHODS

A 96-well plate clonogenic assay was performed with paclitaxel and radiation, both separately and concomitantly. Survival data were fitted to the linear quadratic model. The area under the curve, equivalent to the mean inactivation dose (D), was obtained by numerical integration. The effect of paclitaxel on radiosensitivity was measured as the AUC ratio (paclitaxel plus radiation: radiation alone). This ratio was compared with the surviving fraction (SFP) after paclitaxel alone.

RESULTS

Paclitaxel concentrations of 0.4 to 2.0 nanomolar (nM) caused 1 to 70% inhibition of clonogenic survival. The AUC values of the cell lines were 1.9 to 2.9 gray. A full additive effect was observed when paclitaxel and radiation were administered concurrently; however, a supra-additive effect never occurred. The type of paclitaxel radiation interaction was not affected by the concentration of the drug nor did the type of interaction vary between cell lines studied.

CONCLUSIONS

Paclitaxel and radiation used concomitantly produced a clear additive effect at all concentrations and in all vulvar carcinoma cell lines tested. Although no supra-additive effect was observed, the additive effect already in nM concentrations could be beneficial in clinical use and, therefore, requires further investigation.

Endometrial cancer cell lines are sensitive to paclitaxel

We have previously reported a 24 fold difference in the cisplatin sensitivity and a 12 fold difference in carboplatin sensitivity of endometrial carcinoma cell lines. In this study as evaluate paclitaxel sensitivity of the same cell lines. We tested nine endometrial cancer cell lines with the 96-well plate clonogenic assay using limiting dilution. The chemosensitivity was expressed as IC50 value, the drug concentration causing 50% inhibition of clonogenic survival. IC50 values were obtained from dose-response curves after fitting the data to the linear quadratic equation. The IC50 values for paclitaxel were 0.49 - 2.3 nM showing only a 4.7 fold difference between various cell lines. No correlation could be demonstrated between in vitro paclitaxel and platinum analog sensitivities of endometrial adenocarcinoma cell lines. The variance in paclitaxel sensitivity of different cell lines was little. Our results suggest that endometrial adenocarcinoma cell lines tested with the same methods. The clinical efficacy of paclitaxel in the treatment of endometrial cancer should further be evaluated in clinical trials.

Comparison of cellular radiosensitivity between different localizations of head and neck squamous-cell carcinoma

The prognosis of carcinomas arising from various sites in the head and neck varies even when the stage of the disease is taken into consideration, e.g. laryngeal carcinoma has a more favourable prognosis compared to oral-cavity malignancies. The purpose of this study was to evaluate intrinsic cellular radiosensitivity as one possible explanation for the observed differences in the survival rates of different anatomical groups. The radiation survival curves were determined for well characterized cell lines derived from laryngeal carcinoma (n = 14), pharyngeal carcinoma (n = 6), carcinoma of the oral cavity (n = 14) and the skin of the face (n = 3). The intrinsic radiosensitivity was expressed as area under the survival curve (AUC) values, and this cellular parameter was compared with clinical data and survival of the patients. The intrinsic radiosensitivity in the whole group varied between 1.0 Gy and 2.8 Gy with an average of 1.9 Gy. The mean AUC values for the laryngeal cell lines were 2.0 Gy +/- 0.2, for the oral cavity 1.8 +/- 0.3 Gy, for the pharynx 1.8 +/- 0.2 Gy and for cutaneous carcinoma 2.1 +/- 0.1 Gy. There was a slight difference between the groups of glottic and supraglottic cell lines (mean 1.8 +/- 0.2 Gy and 2.1 +/- 0.3 Gy, respectively), which is consistent with the differences in clinical curability of these cancers. Otherwise, the differences in cellular radiosensitivity of the carcinoma groups studied did not reach statistical significance. These results indicate that the intrinsic radiosensitivity of squamous-cell carcinoma (SCC) of the larynx does not significantly differ from that of SCC of other sites of the head and neck. Variations in the intrinsic radiosensitivity do not as such seem to explain the observed differences in radiocurability of SCC variously localized in the head and neck.