The intrinsic radiosensitivity of cervical carcinoma: correlations with clinical data

Characterization of Intrinsic Radiation Sensitivity in a Diverse Panel of Normal, Cancerous and CRISPR-Modified Cell Lines

Intrinsic radiosensitivity is a major determinant of radiation response. Despite the extensive amount of radiobiological data available, variability among different studies makes it very difficult to produce high-quality radiosensitivity biomarkers or predictive models. Here, we characterize a panel of 27 human cell lines, including those derived from lung cancer, prostate cancer, and normal tissues. In addition, we used CRISPR-Cas9 to generate a panel of lines with known DNA repair defects. These cells were characterised by measuring a range of biological features, including the induction and repair of DNA double-strand breaks (DSBs), cell cycle distribution, ploidy, and clonogenic survival following X-ray irradiation. These results offer a robust dataset without inter-experimental variabilities for model development. In addition, we used these results to explore correlations between potential determinants of radiosensitivity. There was a wide variation in the intrinsic radiosensitivity of cell lines, with cell line Mean Inactivation Doses (MID) ranging from 1.3 to 3.4 Gy for cell lines, and as low as 0.65 Gy in Lig4^-/- cells. Similar substantial variability was seen in the other parameters, including baseline DNA damage, plating efficiency, and ploidy. In the CRISPR-modified cell lines, residual DSBs were good predictors of cell survival (R² = 0.78, p = 0.009), as were induced levels of DSBs (R² = 0.61, p = 0.01). However, amongst the normal and cancerous cells, none of the measured parameters correlated strongly with MID (R² < 0.45), and the only metrics with statistically significant associations are plating efficiency (R² = 0.31, p = 0.01) and percentage of cell in S phase (R² = 0.37, p = 0.005). While these data provide a valuable dataset for the modelling of radiobiological responses, the differences in the predictive power of residual DSBs between CRISPR-modified and other subgroups suggest that genetic alterations in other pathways, such as proliferation and metabolism, may have a greater impact on cellular radiation response. These pathways are often neglected in response modelling and should be considered in the future.

Dynamic Characteristics and Predictive Capability of Tumor Voxel Dose-Response Assessed Using 18F-FDG PET/CT Imaging Feedback

Purpose

Tumor voxel dose–response matrix (DRM) can be quantified using feedback from serial FDG-PET/CT imaging acquired during radiotherapy. This study investigated the dynamic characteristics and the predictive capability of DRM.

Methods

FDG-PET/CT images were acquired before and weekly during standard chemoradiotherapy with the treatment dose 2 Gy × 35 from 31 head and neck cancer patients. For each patient, deformable image registration was performed between the pretreatment/baseline PET/CT image and each weekly PET/CT image. Tumor voxel DRM was derived using linear regression on the logarithm of the weekly standard uptake value (SUV) ratios for each tumor voxel, such as SUV measured at a dose level normalized to the baseline SUV₀. The dynamic characteristics were evaluated by comparing the DRM_i estimated using a single feedback image acquired at the ith treatment week (i = 1, 2, 3, or 4) to the DRM estimated using the last feedback image for each patient. The predictive capability of the DRM estimated using 1 or 2 feedback images was evaluated using the receiver operating characteristic test with respect to the treatment outcome of tumor local–regional control or failure.

Results

The mean ± SD of tumor voxel SUV measured at the pretreatment and the 1st, 2nd, 3rd, 4th, and last treatment weeks was 6.76 ± 3.69, 5.72 ± 3.43, 3.85 ± 2.22, 3.27 ± 2.25, 2.5 ± 1.79, and 2.23 ± 1.27, respectively. The deviations between the DRM_i estimated using the single feedback image obtained at the ith week and the last feedback image were 0.86 ± 4.87, −0.06 ± 0.3, −0.09 ± 0.17, and −0.09 ± 0.12 for DRM₁, DRM₂, DRM₃, and DRM₄, respectively. The predictive capability of DRM₃ and DRM₄ was significant (p < 0.001). The area under the curve (AUC) was increased with the increase in treatment dose level. The DRMs constructed using the single feedback image achieved an AUC of 0.86~1. The AUC was slightly improved to 0.94~1 for the DRMs estimated using 2 feedback images.

Conclusion

Tumor voxel metabolic activity measured using FDG-PET/CT fluctuated noticeably during the first 2 treatment weeks and obtained a stabilized reduction rate thereafter. Tumor voxel DRM constructed using a single FDG-PET/CT feedback image after the 2nd treatment week (>20 Gy) has a good predictive capability. The predictive capability improved continuously using a later feedback image and marginally improved when two feedback images were applied.

Inter/intra-tumoral dose response variations assessed using FDG-PET/CT feedback images: Impact on tumor control and treatment dose prescription

PURPOSE

To quantify inter/intra-tumoral variations of baseline metabolic activity and dose response. To evaluate their impact on tumor control and treatment dose prescription strategies.

METHODS AND MATERIALS

Tumor voxel baseline metabolic activity, SUV₀, and dose response matrix, DRM, quantified using the pre-treatment and weekly FDG-PET/CT imaging feedback for each of 34 HNSCC patients (25 HPV+ and 9 HVP-) were evaluated. Inter/intra-tumoral variations of tumor voxel (SUV₀, DRM) for each of the HPV- and HPV+ tumor groups were quantified and used to evaluate the variations of individual tumor control probabilities and the efficiency of uniform vs non-uniform treatment dose prescription strategies.

RESULTS

Tumor voxel dose response variation of all tumor voxels assessed using FDG-PET/CT imaging feedback had the mean(CV) = 0.47(47%), which was consistent with those of previously published in vitro tumor clonogenic assay. The HPV- tumors had the mean(CV) dose response, 0.53(49%), significantly larger than those of the HPV+ tumors, 0.45(43%). However, their baseline SUVs were opposite, 6.5(56%) vs 7.7(65%). Comparing to the inter-tumoral variations, both HPV-/+ tumor groups showed larger intra-tumoral variations, (53%, 58%) vs (20%, 31%) for the baseline SUV and (38%, 37%) vs (31%, 21%) for the dose response. Due to the large dose response variations, treatment dose to control the tumor voxels has very broad range with CV of TCD₅₀ = 97% for the HPV- and 67% for the HPV+ tumor group respectively. As a consequence, heterogeneous prescription dose could potentially reduce the treatment integral dose for 92% of the HPV+ tumors and 78% of the HPV- tumors.

CONCLUSIONS

The study demonstrates that tumor dose response assessed using FDG-PET/CT feedback images had a similar distribution to those assessed conventionally using in vitro tumor clonogenic assay. Inter-tumoral dose response variation seems larger for HPV- tumors, but intra-tumoral dose response variations are similar for both HPV groups. These variations cause very large variation on the individual tumor control probability and limit the efficacy of dose escalation and de-escalation in conventional clinical practice. On the other hand, heterogeneous dose prescription guided by metabolic imaging feedback has a potential advantage in radiotherapy.

Role of Histopathological Differentiation as a Prognostic Factor for Treatment Response in Locally Advanced Squamous Cell Carcinoma Cervix Patients

Introduction: The aim of the study was to evaluate the prognostic significance of histopathological differentiation in treatment outcome of locally advanced carcinoma cervix. Materials and Methods: This retrospective study includes 167 patients of locally advanced carcinoma cervix treated between January 2006 and December 2008 who have received definitive chemoradiation. Results:: The number of patients with well (85 [50.9%]) and moderately differentiated (76 [45.5%]) carcinoma was nearly equal with poorly differentiated variety having only 6 (3.6%) patients. On completion of treatment out of the 167 patients, 133 (79.6%) had a complete response and 34 (20.4%) had residual disease. On mean follow-up of 11 months, 19 (14.2%) patients had local and 5 (3.7%) had a distant relapse. Histopathological differentiation and age had no association with treatment outcome, whereas early-stage disease showed trend favoring better treatment response. Conclusion: Advanced stage along with poor histopathological differentiation influences the aggressiveness of the tumor responsible for distant relapse. However, histopathological differentiation has no correlation with local treatment response and overall survival. The main factor influencing the treatment outcome is the intrinsic radiosensitivity of the tumor and volume of the disease.

Postoperative clinicopathological factors affecting cervical adenocarcinoma: Stages I-IIB

Currently, cervical adenocarcinoma (ADC) receives the same standard treatment as squamous cell carcinoma, but this treatment regimen is not wholly suited for ADC. The present study was conducted to assess the prognostic role of postoperative clinicopathological factors in patients with stage I-IIB cervical ADC.The study examined 312 patients with stage I-IIB cervical ADC who underwent radical hysterectomy, including pelvic lymphadenectomy, at our institutions between October 2006 and September 2014. Overall survival (OS) and relapse-free survival (RFS) was analyzed by the Kaplan-Meier method. Sites of recurrence were classified as local and distant locations.The 5-year OS and RFS rates were 88.2% and 83.8%, respectively. The 5-year OS rates for patients with International Federation of Gynecology and Obstetrics (FIGO) stage IA, IB, IIA, and IIB were 100.0%, 90.7%, 82.8%, and 55.6%, respectively. The Cox model identified number of positive pelvic nodes and age at surgery as independent prognostic factors for survival, and number of positive pelvic nodes and postoperative tumor diameter (≥4 cm) as independent prognostic factors for relapse. Cancer recurrence developed in 35 women. The top three recurrence sites were pelvis, vaginal stump, and lung.A more aggressive therapeutic strategy different from current practice in cervical cancer is urgently required for cervical ADC. As a new prognostic factor, postoperative tumor diameter should receive special attention in ADC treatment.

Ex vivo γH2AX radiation sensitivity assay in prostate cancer: Inter-patient and intra-patient heterogeneity

INTRODUCTION

The aim of the study is to assess inter-patient and intra-patient heterogeneity in tumour cell radiosensitivity using the ex vivo γH2AX assay in prostate cancer specimens.

METHODS

Excised specimens from untreated prostate cancer patients were cultivated 24h in media, irradiated ex vivo and fixed after 24h. Residual γH2AX foci were counted and the slope of the dose response was calculated. Intra-patient heterogeneity was studied from three to seven different biopsies.

RESULTS

In pathology-confirmed tumour samples from 21 patients the slope of residual γH2AX foci and radiation dose showed a substantial heterogeneity ranging from 0.82 to 3.17 foci/Gy. No correlation was observed between the slope values and the Gleason score (p=0.37), prostate specific antigen (p=0.48) and tumour stage (p=0.89). ANOVA indicated that only in 1 out of 9 patients, biopsies from different tumour locations yielded statistically significant differences. Variance component analysis indicated higher inter-patient than intra-patient variability. Bootstrap simulation study demonstrated that one biopsy is sufficient to estimate the mean value of residual γH2AX per dose level and account for intra-patient heterogeneity.

CONCLUSIONS

In prostate cancer inter-patient heterogeneity in tumour cell radiation sensitivity is pronounced and higher than intra-patient heterogeneity supporting the further development of the γH2AX ex vivo assay as a biomarker for individualized treatment.

Effects of Treatment of Uterine Cervical Carcinoma Monitored by Magnetic Resonance Imaging - Sarajevo Experience

GOAL

The goal of this study was the determination of the effects in treatment of early stage (

MATERIAL AND METHODS

The study was a prospective, comparative, analytical, and observational and included 74 patients with cervical cancer (PH confirmed). All 74 patients have initially gone through the pre-therapeutic MRI to determine the tumour FIGO stage. At a renewal of the initial MRI findings, patients were divided into two study groups: group A and group B. Group A consisted from 39 patients with early-stage cervical carcinoma (

RESULTS

An analysis of treatment outcomes in group A showed that most patients had no local recurrence or residuum disease in 89.7%, while local recurrence was observed in only 10.3% cases. An analysis of treatment outcomes in group B showed that most patients had complete regression after local chemoradiotherapy in 68.8%, while 25.7% of patients had local progression of the disease, while the 5.7% cases recorded partial local tumour regression(p<0.05). It has been shown that a complete local regression was more frequent in the case of squamous cell carcinoma in 74.2% vs 25% in adenocarcinoma cases. Also local and partial regression was observed more frequently in the case of squamous cell carcinoma in 6.5% compared to 0% in adenocarcinoma, while progression was more common in adenocarcinoma at 75% compared to 19.4% for squamous cell (p<0.05). MRI results showed positive outcome of treatment group A and B in our study, showed a statistically significant difference in favour of group A (89.7%) compared to group B 68.8% (p<0.05).

CONCLUSION

The results obtained from our studies show that early stage cervical cancer ( Collapse

Key Words

• FIGO stage
• MRI
• cervical cancer
• oncology treatment
• surgical treatment

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Affiliation(s)

Amela Sofic Clinic of Radiology, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Azra Husic-Selimovic Institute of Gastroenterohepatology, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Nermina Beslic Clinic of Nuclear medicine, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Azra Rasic Oncology Clinic, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Dzenana Begic Oncology Clinic, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Anja Tomic-Cica Clinic of obstetrics and gynecology, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina
Nejira Imsirevic Institute of Gastroenterohepatology, Clinical center University of Sarajevo, Sarajevo, Bosnia and Herzegovina

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Intrinsic Radiosensitivity and Cellular Characterization of 27 Canine Cancer Cell Lines

Canine cancer cell lines have progressively been developed, but are still underused resources for radiation biology research. Measurement of the cellular intrinsic radiosensitivity is important because understanding the difference may provide a framework for further elucidating profiles for prediction of radiation therapy response. Our studies have focused on characterizing diverse canine cancer cell lines in vitro and understanding parameters that might contribute to intrinsic radiosensitivity. First, intrinsic radiosensitivity of 27 canine cancer cell lines derived from ten tumor types was determined using a clonogenic assay. The 27 cell lines had varying radiosensitivities regardless tumor type (survival fraction at 2 Gy, SF2 = 0.19-0.93). In order to understand parameters that might contribute to intrinsic radiosensitivity, we evaluated the relationships of cellular radiosensitivity with basic cellular characteristics of the cell lines. There was no significant correlation of SF2 with S-phase fraction, doubling time, chromosome number, ploidy, or number of metacentric chromosomes, while there was a statistically significant correlation between SF2 and plating efficiency. Next, we selected the five most radiosensitive cell lines as the radiosensitive group and the five most radioresistant cell lines as the radioresistant group. Then, we evaluated known parameters for cell killing by ionizing radiation, including radiation-induced DNA double strand break (DSB) repair and apoptosis, in the radiosensitive group as compared to the radioresistant group. High levels of residual γ-H2AX foci at the sites of DSBs were present in the four out of the five radiosensitive canine cancer cell lines. Our studies suggested that substantial differences in intrinsic radiosensitivity exist in canine cancer cell lines, and radiation-induced DSB repair was related to radiosensitivity, which is consistent with previous human studies. These data may assist further investigations focusing on the detection of DSB for predicting individual response to radiation therapy for dogs, regardless of tumor type.

Residual γH2AX foci after ex vivo irradiation of patient samples with known tumour-type specific differences in radio-responsiveness

PURPOSE

To apply our previously published residual ex vivo γH2AX foci method to patient-derived tumour specimens covering a spectrum of tumour-types with known differences in radiation response. In addition, the data were used to simulate different experimental scenarios to simplify the method.

MATERIALS AND METHODS

Evaluation of residual γH2AX foci in well-oxygenated tumour areas of ex vivo irradiated patient-derived tumour specimens with graded single doses was performed. Immediately after surgical resection, the samples were cultivated for 24h in culture medium prior to irradiation and fixed 24h post-irradiation for γH2AX foci evaluation. Specimens from a total of 25 patients (including 7 previously published) with 10 different tumour types were included.

RESULTS

Linear dose response of residual γH2AX foci was observed in all specimens with highly variable slopes among different tumour types ranging from 0.69 (95% CI: 1.14-0.24) to 3.26 (95% CI: 4.13-2.62) for chondrosarcomas (radioresistant) and classical seminomas (radiosensitive) respectively. Simulations suggest that omitting dose levels might simplify the assay without compromising robustness.

CONCLUSION

Here we confirm clinical feasibility of the assay. The slopes of the residual foci number are well in line with the expected differences in radio-responsiveness of different tumour types implying that intrinsic radiation sensitivity contributes to tumour radiation response. Thus, this assay has a promising potential for individualized radiation therapy and prospective validation is warranted.

Intraoperative Electron Beam Radiotherapy (IOERT) in the management of locally advanced or recurrent cervical cancer

Background

To report outcomes in women with locally recurrent or advanced cervical cancer who received intraoperative electron beam radiotherapy (IOERT) as a component of therapy.

Methods

From 1983 to 2010, 86 patients with locally recurrent (n = 73, 85%) or primary advanced (n = 13, 15%) cervical cancer received IOERT following surgery. Common surgeries included pelvic exenteration (n = 26; 30%) or sidewall resection (n = 22; 26%). The median IOERT dose was 15 Gy (range, 6.25-25 Gy). Sixty-one patients (71%) received perioperative external beam radiotherapy (EBRT; median dose, 45 Gy). Forty-one patients (48%) received perioperative chemotherapy.

Results

Median follow-up was 2.7 years (range, 0.1-25.5 years). Resections were classified as R0 (n = 35, 41%), R1 (n = 30, 35%), or R2 (n = 21, 24%). Cumulative incidences of central (within the IOERT field) and locoregional relapse at 3 years were 23 and 38%, respectively. The 3-year cumulative incidence of distant relapse was 43%. Median survival was 15 months, and 3-year Kaplan-Meier estimates of cause-specific (CSS) and overall survival (OS) were 31 and 25%, respectively. On multivariate analysis, pelvic exenteration (p = 0.02) and perioperative EBRT (p = 0.009) were associated with improved central control in patients with recurrent disease. Recurrence within 6 months of initial therapy was associated with reduced CSS (p = 0.001). Common IOERT-related toxicities included peripheral neuropathy (n = 16), ureteral stenosis (n = 4), and bowel fistula/perforation (n = 4). Eleven of 16 patients with neuropathy required long-term pain medication.

Conclusions

Long-term survival is possible with combined modality therapy including IOERT for advanced cervical cancer. Distant relapse is common, yet a significant number of patients experienced local progression in spite of aggressive treatment. In addition to consideration of disease- and treatment-related morbidity, other factors to be considered when selecting patients for this approach include the time interval from initial therapy to recurrence and whether the patient is able to receive perioperative EBRT and pelvic exenteration in addition to IOERT.

Early response and local control of stage I non-small-cell lung cancer after stereotactic radiotherapy: difference by histology

To investigate the possible influences of various factors on tumor response to radiation, regression speeds and long-term local control rates of primary adenocarcinoma and squamous cell carcinoma of the lung after stereotactic body radiotherapy were evaluated. Ninety-one patients (65 men and 26 women) with a median age of 76 years were serially examined using computed tomography at 2, 4 and 6 months after treatment. Tumor histology was adenocarcinoma in 62 patients and squamous cell carcinoma in 29 patients. The prescribed dose was 48 Gy in four fractions given twice a week for T1 tumors (≤ 3 cm) and 52 Gy in four fractions given twice a week for T2 tumors (3-5 cm). Tumor shrinkage speed and 3-year local control rates were similar between T1 and T2 tumors and between patients with normal pulmonary function and those with impaired function. Squamous cell carcinomas shrank faster than adenocarcinomas at 2 and 4 months after radiation, but mean relative tumor size at 6 months and local control rates at 3 years did not differ significantly between the two histologies. Tumors in patients with a higher hemoglobin level tended to shrink faster but the control rates were not different. It is concluded that, although squamous cell carcinoma shrinks faster than adenocarcinoma, the two types of lung cancer are of similar radiosensitivity in terms of long-term control rates. Radiosensitivity should not be evaluated by early tumor response.

Regression curves of brain metastases after gamma knife irradiation: Difference by tumor and patient characteristics

Regression curves and local control rates of brain metastases after gamma knife treatment were evaluated to investigate differences in tumor response to radiation. A total of 203 metastases were serially evaluated using contrast-enhanced MRI (or computed tomography) at 1, 2, 3, 4.5 and 6 months after a 20-Gy dose. Differences were evaluated in regression curves and control rates between tumors ≥10 mm and tumors <10 mm in mean diameter, among three major histological subtypes of lung cancer, among adenocarcinomas of the lung, breast and colorectum, and between tumors in patients with above and below median hemoglobin levels. Smaller tumors shrank faster and yielded better control rates than larger tumors. Metastases from small cell and squamous cell carcinomas of the lung shrank faster than those from lung adenocarcinoma, but 6-month control rates were not different. Breast adenocarcinomas tended to shrink faster than lung adenocarcinomas, but the control rates were not different among adenocarcinomas of the lung, breast and colorectum. Tumors in patients with higher hemoglobin levels tended to shrink faster but the control rates were not different. Small cell and squamous cell carcinomas of the lung regress more rapidly than adenocarcinomas, although local control rates might not differ significantly.

Impact of various treatment modalities on the outcome of stage IB1-IIA cervical adenocarcinoma

OBJECTIVE

To evaluate the outcomes of patients with stage IB1-IIA cervical adenocarcinoma treated by various modalities in order to formulate a better treatment strategy.

METHODS

The impact of various treatment modalities on the prognosis of 258 patients with stage IB1-IIA cervical adenocarcinoma was investigated. The therapeutic modalities included radical surgery (n=174); radical surgery followed by adjuvant radiation therapy (RT), such as RT alone or concurrent chemo-radiotherapy (CCRT) (n=46); or primary RT or CCRT (n=38).

RESULTS

As compared with patients in the surgery-only group, patients with 1 postoperative major risk who underwent surgery followed by RT or CCRT had a significantly higher likelihood of disease relapse (2.3-fold, P=0.041) and disease-related death (2.9-fold, P=0.014). The likelihood of recurrence (P=0.32) and death (P=0.58) did not differ between patients who underwent adjuvant RT or CCRT for 1 major risk factor and those who underwent primary RT or CCRT. By contrast, patients with more than 1 major risk factor had a higher likelihood of disease recurrence (2.9-fold, P=0.037) and disease-related death (3.4-fold, P=0.051) than those who underwent primary RT or CCRT.

CONCLUSION

Radical surgery is recommended for patients with stage IB1-IIA cervical adenocarcinomas without contraindications. Those with more than 1 postoperative pathologic risk factor had the worst prognosis despite adjuvant RT or CCRT.

Biological impact of geometric uncertainties: what margin is needed for intra-hepatic tumors?

Background

To evaluate and compare the biological impact on different proposed margin recipes for the same geometric uncertainties for intra-hepatic tumors with different tumor cell types or clinical stages.

Method

Three different margin recipes based on tumor motion were applied to sixteen IMRT plans with a total of twenty two intra-hepatic tumors. One recipe used the full amplitude of motion measured from patients to generate margins. A second used 70% of the full amplitude of motion, while the third had no margin for motion. The biological effects of geometric uncertainty in these three situations were evaluated with Equivalent Uniform Doses (EUD) for various survival fractions at 2 Gy (SF₂).

Results

There was no significant difference in the biological impact between the full motion margin and the 70% motion margin. Also, there was no significant difference between different tumor cell types. When the margin for motion was eliminated, the difference of the biological impact was significant among different cell types due to geometric uncertainties. Elimination of the motion margin requires dose escalation to compensate for the biological dose reduction due to the geometric misses during treatment.

Conclusions

Both patient-based margins of full motion and of 70% motion are sufficient to prevent serious dosimetric error. Clinical implementation of margin reduction should consider the tumor sensitivity to radiation.

Combined use of hyperthermia and radiation therapy for treating locally advanced cervix carcinoma

BACKGROUND

Hyperthermia is a type of cancer treatment in which body tissue is exposed to high temperatures to damage and kill cancer cells. It was introduced into clinical oncology practice several decades ago. Positive clinical results, mostly obtained in single institutions, resulted in clinical implementation albeit in a limited number of cancer centres worldwide. Because large scale randomised clinical trials (RCTs) are lacking, firm conclusions cannot be drawn regarding its definitive role as an adjunct to radiotherapy in the treatment of locally advanced cervix carcinoma (LACC).

OBJECTIVES

To assess whether adding hyperthermia to standard radiotherapy for LACC has an impact on (1) local tumour control, (2) survival and (3) treatment related morbidity.

SEARCH STRATEGY

The electronic databases of the Cochrane Central Register of Controlled Trials (CENTRAL), (Issue 1, 2009) and Cochrane Gynaecological Cancer Groups Specialised Register, MEDLINE, EMBASE, online databases for trial registration, handsearching of journals and conference abstracts, reviews, reference lists, and contacts with experts were used to identify potentially eligible trials, published and unpublished until January 2009.

SELECTION CRITERIA

RCTs comparing radiotherapy alone (RT) versus combined hyperthermia and radiotherapy (RHT) in patients with LACC.

DATA COLLECTION AND ANALYSIS

Between 1987 and 2009 the results of six RCTs were published, these were used for the current analysis.

MAIN RESULTS

74% of patients had FIGO stage IIIB LACC. Treatment outcome was significantly better for patients receiving the combined treatment (Figures 4 to 6). The pooled data analysis yielded a significantly higher complete response rate (relative risk (RR) 0.56; 95% confidence interval (CI) 0.39 to 0.79; p < 0.001), a significantly reduced local recurrence rate (hazard ratio (HR) 0.48; 95% CI 0.37 to 0.63; p < 0.001) and a significantly better overall survival (OS) following the combined treatment with RHT(HR 0.67; 95% CI 0.45 to 0.99; p = 0.05). No significant difference was observed in treatment related acute (RR 0.99; 95% CI 0.30 to 3.31; p = 0.99) or late grade 3 to 4 toxicity (RR 1.01; CI 95% 0.44 to 2.30; p = 0.96) between both treatments.

AUTHORS' CONCLUSIONS

The limited number of patients available for analysis, methodological flaws and a significant over-representation of patients with FIGO stage IIIB prohibit drawing definite conclusions regarding the impact of adding hyperthermia to standard radiotherapy. However, available data do suggest that the addition of hyperthermia improves local tumour control and overall survival in patients with locally advanced cervix carcinoma without affecting treatment related grade 3 to 4 acute or late toxicity.

Combined use of hyperthermia and radiation therapy for treating locally advanced cervical carcinoma

BACKGROUND

Hyperthermia is a type of cancer treatment in which body tissue is exposed to high temperatures to damage and kill cancer cells. It was introduced into clinical oncology practice several decades ago. Positive clinical results, mostly obtained in single institutions, resulted in clinical implementation albeit in a limited number of cancer centres worldwide. Because large scale randomised clinical trials (RCTs) are lacking, firm conclusions cannot be drawn regarding its definitive role as an adjunct to radiotherapy in the treatment of locally advanced cervical carcinoma (LACC).

OBJECTIVES

To assess whether adding hyperthermia to standard radiotherapy for LACC has an impact on (1) local tumour control, (2) survival and (3) treatment related morbidity.

SEARCH STRATEGY

The electronic databases of the Cochrane Central Register of Controlled Trials (CENTRAL), (Issue 1, 2009) and Cochrane Gynaecological Cancer Groups Specialised Register, MEDLINE, EMBASE, online databases for trial registration, handsearching of journals and conference abstracts, reviews, reference lists, and contacts with experts were used to identify potentially eligible trials, published and unpublished until January 2009.

SELECTION CRITERIA

RCTs comparing radiotherapy alone (RT) versus combined hyperthermia and radiotherapy (RHT) in patients with LACC.

DATA COLLECTION AND ANALYSIS

Between 1987 and 2009 the results of six RCTs were published, these were used for the current analysis.

MAIN RESULTS

74% of patients had FIGO stage IIIB LACC. Treatment outcome was significantly better for patients receiving the combined treatment (Figures 1 to 3). The pooled data analysis yielded a significantly higher complete response rate (relative risk (RR) 0.56; 95% confidence interval (CI) 0.39 to 0.79; p < 0.001), a significantly reduced local recurrence rate at 3 years (hazard ratio (HR) 0.48; 95% CI 0.37 to 0.63; p < 0.001) and a significanly better overall survival (OS) at three years following the combined treatment with RHT(HR 0.67; 95% CI 0.45 to 0.99; p = 0.05). No significant difference was observed in treatment related acute (RR 0.99; 95% CI 0.30 to 3.31; p = 0.99) or late grade 3 to 4 toxicity (RR 1.01; CI 95% 0.44 to 2.30; p = 0.96) between both treatments.

AUTHORS' CONCLUSIONS

The limited number of patients available for analysis, methodological flaws and a significant over-representation of patients with FIGO stage IIIB prohibit drawing definite conclusions regarding the impact of adding hyperthermia to standard radiotherapy. However, available data do suggest that the addition of hyperthermia improves local tumour control and overall survival in patients with locally advanced cervical carcinoma without affecting treatment related grade 3 to 4 acute or late toxicity.

Equivalent uniform dose concept evaluated by theoretical dose volume histograms for thoracic irradiation

BACKGROUND AND PURPOSE

The goal of our study was to quantify the limits of the EUD models for use in score functions in inverse planning software, and for clinical application.

MATERIALS AND METHODS

We focused on oesophagus cancer irradiation. Our evaluation was based on theoretical dose volume histograms (DVH), and we analyzed them using volumetric and linear quadratic EUD models, average and maximum dose concepts, the linear quadratic model and the differential area between each DVH.

RESULTS

We evaluated our models using theoretical and more complex DVHs for the above regions of interest. We studied three types of DVH for the target volume: the first followed the ICRU dose homogeneity recommendations; the second was built out of the first requirements and the same average dose was built in for all cases; the third was truncated by a small dose hole. We also built theoretical DVHs for the organs at risk, in order to evaluate the limits of, and the ways to use both EUD(1) and EUD/LQ models, comparing them to the traditional ways of scoring a treatment plan. For each volume of interest we built theoretical treatment plans with differences in the fractionation.

CONCLUSION

We concluded that both volumetric and linear quadratic EUDs should be used. Volumetric EUD(1) takes into account neither hot-cold spot compensation nor the differences in fractionation, but it is more sensitive to the increase of the irradiated volume. With linear quadratic EUD/LQ, a volumetric analysis of fractionation variation effort can be performed.

Correlation between initial chromatid damage and survival of various cell lines exposed to heavy charged particles

The biophysical characteristics of heavy ions make them a rational source of radiation for use in radiotherapy of malignant tumours. Prior to radiotherapy treatment, a therapeutic regimen must be precisely defined, and during this stage information on individual patient radiosensitivity would be of very great medical value. There are various methods to predict radiosensitivity, but some shortfalls are difficult to avoid. The present study investigated the induction of chromatid breaks in five different cell lines, including one normal liver cell line (L02), exposed to carbon ions accelerated by the heavy ion research facility in Lanzhou (HIRFL), using chemically induced premature chromosome condensation (PCC). Previous studies have reported the number of chromatid breaks to be linearly related to the radiation dose, but the relationship between cell survival and chromatid breaks is not clear. The major result of the present study is that cellular radiosensitivity, as measured by D0, is linearly correlated with the frequency of chromatid breaks per Gy in these five cell lines. We propose that PCC may be applied to predict radiosensitivity of tumour cells exposed to heavy ions.

A correlation between radiation sensitivity and initial chromatid breaks in cancer cell lines revealed by Calyculin A-induced premature condensation

Three human malignancy cell lines were irradiated with 60Co γ-rays. Initial chromatid breaks were measured by using the chemically induced premature chromosome condensation technique. Survival curves of cells exposed to gamma rays was linear-quadratic while the efficiency of Calyculin A in inducing PCC of G2 PCC was about five times more than G1 PCC. A dose-dependent increase in radiation-induced chromatid/isochromatid breaks was observed in G1 and G2 phase PCC and a nearly positive linear correlation was found between cell survival and chromatin breaks. This study implies that low LET radiation-induced chromatid/isochromatid breaks can potentially be used to predict the radiosensitivity of tumor cells either in in vitro experimentation or in in vivo clinical radiotherapy.

What is the difference between squamous cell carcinoma and adenocarcinoma of the cervix? A matched case–control study

The objective of this study was to investigate the efficacy of treatment strategies in patients with adenocarcinoma (AC) of the cervix and compare it with those with squamous cell carcinoma (SCC) of the cervix. Women with FIGO (1994) stage IB1 AC, especially pathologic tumor size of 2-4 cm, treated with class III hysterectomy, were compared with those with SCC treated with comparable strategy in a case-controlled study. Eighty patients (20 cases, 60 controls) were analyzed. Lymphvascular space invasion (P = 0.01) and lymph node metastasis (P = 0.07) were more frequent in patients with SCC than in those with AC. However, there was no significant difference in depth of stromal invasion (P = 0.51) and invasion of the parametrium (P = 0.44) between two groups. And there was also no statistically significant difference in disease-free survival (P = 0.86) and overall survival (P = 0.89) between two groups. Primary radical surgery followed by adjuvant therapy, same as for SCC, would be acceptable for AC with pathologic tumor size of 2-4 cm. Although it was difficult to determine whether AC recurred more systemically, more effective treatment strategies than those currently available for AC should be considered to reduce the systemic recurrence.

Comparison of clonogenic assay with premature chromosome condensation assay in prediction of human cell radiosensitivity

AIM: To determine whether the number of non-rejoining G2-chromatid breaks can predict the radiosensitivity of human cell lines.

METHODS: Cell lines of human ovary carcinoma cells (HO8910), human hepatoma cells (HepG2) and liver cells (L02) were irradiated with a range of doses and assessed both of cell survival and non-rejoining G2-chromatid breaks at 24 h after irradiation. Cell survival was documented by a colony assay. Non-rejoining G2-chromatid breaks were measured by counting the number of non-rejoining G2 chromatid breaks at 24 h after irradiation, detected by the prematurely chromosome condensed (PCC) technique.

RESULTS: A linear-quadratic survival curve was observed in three cell lines, and HepG2 was the most sensitive to γ-radiation. A dose-dependent linear increase was observed in radiation-induced non-rejoining G2-PCC breaks measured at 24 h after irradiation in all cell lines, and HepG2 was the most susceptible to induction of non-rejoining G2-PCC breaks. A close correlation was found between the clonogenic radiosensitivity and the radiation-induced non-rejoining G2-PCC breaks (r = 0.923). Furthermore, survival-aberration correlations for two or more than two doses lever were also significant.

CONCLUSION: The number of non-rejoining G2 PCC breaks holds considerable promise for predicting the radiosensitivity of normal and tumor cells when two or more than two doses lever is tested.

Molecular targets for altering radiosensitivity: lessons from Ras as a pre-clinical and clinical model

Ras activation has been correlated with malignant and metastatic cancer phenotypes and poor prognosis for cancer patients. In the preclinical setting, Ras activation by mutation or EGFR amplification results in increased clonogenic cell survival and decreased tumor growth delay following irradiation. Activation of the Ras pathway has also been associated with increased risk of local failure and decreased overall survival in patients receiving radiotherapy. Prenyltransferase inhibitors target the post-translational processing of Ras and have been shown to increase the radiosensitivity of human cancer cell lines. In the clinical setting, these inhibitors have been used with concurrent radiotherapy in a small number of phase I clinical trials with acceptable toxicity. Therefore, inhibiting Ras activation represents a promising molecular approach for radiosensitization in cancer therapy.

Comparative study on radiosensitivity of various tumor cells and human normal liver cells

AIM: To investigate the radiation response of various human tumor cells and normal liver cells.

METHODS: Cell lines of human hepatoma cells (SMMC-7721), liver cells (L02), melanoma cells (A375) and cervical tumor (HeLa) were irradiated with ⁶⁰Co γ-rays. Cell survive was documented by a colony assay. Chromatid breaks were measured by counting the number of chromatid breaks and isochromatid breaks immediately after prematurely chromosome condensed by Calyculin-A.

RESULTS: Linear quadratic survival curve was observed in all of four cell lines, and dose-dependent increase in radiation-induced chromatid and isochromatid breaks were observed in GB2B phase. Among these four cell lines, A375 was most sensitive to radiation, while, L02 had the lowest radiosensitivity. For normal liver cells, chromatid breaks were easy to be repaired, isochromatid breaks were difficult to be repaired.

CONCLUSION: The results suggest that the γ-rays induced chromatid breaks can be possibly used as a good predictor of radiosensitivity, also, unrejoined isochromatid breaks probably tightly related with cell cancerization.

Apoptotic index as predictive marker for radiosensitivity of cervical carcinoma: Evaluation of membrane fluidity, biochemical parameters and apoptosis after the first dose of fractionated radiotherapy to patients

BACKGROUND

This study was aimed to develop possible predictive response of cervical carcinoma in stage IIIA and B patients by evaluating the changes in physical parameter, such as, membrane fluidity, biochemical parameters, such as, intracellular calcium, antioxidant enzymes [superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx)] and apoptotic cell death in cervical cancer cells from patients after treating with the first fractionated dose of 2 Gy in radiation therapy protocol.

METHODS

Biopsies of cervical carcinoma patients were collected before and 24h after first fractionated radiation dose of 2 Gy. Cell suspensions and tissue of cervix cancer biopsies were used to measure various physical and biochemical parameters.

RESULTS AND CONCLUSIONS

A negative correlation was found to exist between observed fluidity of membrane/SOD level with the degree of apoptosis in cervical cells. On the other hand, a positive correlation was observed between intracellular calcium level and percent cellular apoptosis. These results suggest that changes in membrane fluidity, SOD and calcium level were involved in the mechanism of radiation induced cervical apoptosis as measured by TUNEL assay. Moreover, apoptotic sensitivity of these cells after the first dose of radiation treatment showed a direct correlation with the radiation treatment outcome in patients after completion of radiotherapy protocol (70 Gy) in the clinic suggesting that apoptotic index may form a basis for prognosis in radiotherapy in stage III cervix cancer patients.

Targeting tumor cells by enhancing radiation sensitivity

The work of Al Knudson created the paradigm in which we see cancer as a result of the accumulation of multiple mutations. Our goal has been to exploit these mutations to develop strategies to enhance therapy for cancer by targeting the malignant cell while sparing the normal tissue. In studying the RAS oncogene, we observed that its expression when activated resulted in enhanced radioresistance. Conversely, inhibition of RAS made cells with activated RAS more radiosensitive. Hence, we postulated that it would be possible to sensitize tumors with RAS mutations to radiation without affecting the sensitivity of the normal tissue in patients with such tumors. This proved to be the case in animal models and has led to current clinical trials. These studies raised the question of identifying the downstream effectors of RAS that are responsible for altering the radiosensitivity of cells. We have found that phosphoinositide-3-kinase (PI3 kinase) is a critical component of this pathway. Blocking PI3 kinase enhanced the radiation response in vitro or in vivo of cells actively signaling through that pathway, but did not affect cells not actively signaling through PI3 kinase at the time of irradiation. Identification of tumors with active signaling in this pathway by immunohistochemical staining for phosphorylated AKT, the downstream target of PI3 kinase correlated with those patients for which radiation failed to achieve local control. Thus, characterization of the active signaling pathways in a given tumor might enable the selection of patients likely to respond to radiation. Pathways upstream from RAS may also be useful targets to consider for enhancing radiation therapy. Epidermal growth factor receptor (EGFR), which is upstream of PI3 kinase, may also mediate resistance through a common pathway. In addition to EGFR and RAS, PTEN can also regulate the PI3 kinase pathway. Identifying a common signal for EGFR, RAS, and PTEN that results in radiation resistance may uncover targets for developing molecular-based radiosensitization protocols for tumors resistant to radiation and thus lead to improvement of local control.

The RAS signal transduction pathway and its role in radiation sensitivity

RAS has been shown to increase radiation resistance. Upstream and downstream pathways from RAS could thus be targets for manipulation of radiosensitivity. EGFR expression and AKT phosphorylation are also associated with the response to radiation. A retrospective study evaluating EGFR and AKT in patients treated with multimodality therapy found a significant association between P-AKT and treatment failure. Moreover, these data are strengthened by in vitro studies showing that inhibition of EGFR, RAS, PI3K, and AKT radiosensitized cancer cell lines. We have previously shown that PI3K is a mediator of RAS-induced radiation resistance. We now suggest that EGFR, which is upstream of PI3K, may also mediate resistance through a common pathway. In addition to EGFR and RAS, PTEN can also regulate the PI3K pathway. Identifying a common signal for EGFR, RAS, or PTEN that results in radiation resistance may uncover targets for developing molecular-based radiosensitization protocols for tumors resistant to radiation and thus improve local control.

Radiosensitivity of human tumour cells is correlated with the induction but not with the repair of DNA double-strand breaks

Nine human tumour cell lines (four mammary, one bladder, two prostate, one cervical, and one squamous cell carcinoma) were studied as to whether cellular radiosensitivity is related to the number of initial or residual double-strand breaks (dsb). Cellular sensitivity was measured by colony assay and dsb by means of constant- and graded-field gel electrophoresis (CFGE and GFGE, respectively). The nine tumour cell lines showed a broad variation in cellular sensitivity (SF2 0.17-0.63). The number of initial dsb as measured by GFGE ranged between 14 and 27 dsb/Gy/diploid DNA content. In contrast, normal fibroblasts raised from skin biopsies of seven individuals showed only a marginal variation with 18-20 dsb/Gy/diploid DNA content. For eight of the nine tumour cell lines, there was a significant correlation between the number of initial dsb and the cellular radiosensitivity. The tumour cells showed a broad variation in the amount of dsb measured 24 h after irradiation by CFGE, which, however, was not correlated with the cellular sensitivity. This residual damage was found to be influenced not only by the actual number of residual dsb, but also by apoptosis and cell cycle progression which had impact on CFGE measurements. Some cell line strains were able to proliferate even after exposure to 150 Gy while others were found to degrade their DNA. Our results suggest that for tumour cells, in contrast to normal cells, the variation in sensitivity is mainly determined by differences in the initial number of dsb induced.

Does skin fibroblast radiosensitivity predict squamous cancer cell radiosensitivity of the same individual?

Individualization of radiation doses is presumed to result in better radiotherapy outcome. Success rate in measuring radiosensitivity is probably the most limiting factor for present radiosensitivity assays to be introduced into clinical routine. To find a simpler predictive parameter, we compared the radiosensitivity of dermal fibroblasts and head and neck squamous cell carcinoma (SCC) cell lines established from the same individuals. The radiosensitivity was tested using the clonogenic 96-well plate assay. The surviving fraction at 2.0 Gy (SF2) was determined, as well as the mean inactivation dose (AUC) of cancer cells. SF2 of SCC cell lines and skin fibroblasts were 0.25-0.44 and 0.11-0.43, respectively. AUC of SCC cells was 1.4-2.1 Gy. Dermal fibroblasts were more radiosensitive than SCC cells in 14 of 15 cases. In 1 patient (UT-SCC-8), cancer cells were found to be more radiosensitive than corresponding dermal fibroblasts. There was a clear tendency to a correlation between radiosensitivities of these 2 cell types, but statistical significance was reached only when the data of UT-SCC-8 was excluded. In our material, the intrinsic radiosensitivity of head and neck SCC cells could in most cases be predicted from the intrinsic radiosensitivity of dermal fibroblasts established from the same individual.

Chromatin compaction and tumor cell radiosensitivity at 2 gray

Mammalian cells at mitosis, differentiated lymphocytes, and some radiation-hypersensitive mutants in interphase contain all or a measurable portion of their chromatin in condensed/compacted form and are hypersensitive to ionizing radiation by the mechanism described by single-hit inactivation kinetics (alpha). These observations led to the investigation as to whether compacted chromatin in interphase is the target that determines the widely variable alpha-parameters and surviving fractions of 2 Gy (SF2Gy) measured for human tumor cell lines. Six cell lines whose SF2Gy ranged from 0.29 to 0.73 were used for this study. Their different radiosensitivities were associated mainly with differences in their single-hit inactivation parameters (alpha). Electron microscope images of interphase nuclei were optically scanned, and the pixel densities were digitized for quantitative analyses. A significant correlation between the percentage of nuclear pixels with densities similar to those found in mitotic chromosomes (percent compacted chromatin) and the alpha-inactivation parameters was observed. Digital analyses of electron and/or confocal microscope images of chromatin in interphase tumor cells in biopsy specimens could become a rapid assay for predicting the intrinsic radiosensitivity of tumor clonogens. This research has also identified some inhibitors of protein (histone) phosphatases that promote chromatin compaction and radiosensitize cells to 2-Gy dose fractions.

Optimizing radiation treatment for cervical cancer

The technical and radiobiological improvements in the science of radiotherapy, coupled with the use of cisplatin-containing regimens concurrent with radiation therapy, have improved dramatically the cure rate and quality of Life for cervical cancer survivors. Further research is necessary to understand the complex dose distribution of external beam and intracavitary radiation and their relationship to tumor control and complications. With the use of CT-compatible applicators for intracavitary radiation, CT simulation and three-dimensional treatment planning for EBRT, the radiation oncology community should meet this challenge.

An analysis of the relationship between radiosensitivity and volume effects in tumor control probability modeling

The dependence of local tumor control probability (tcp) on tumor volume is analyzed and discussed with the help of radiobiological modeling; in particular the impact of possible correlations between mean tumor radiosensitivity and tumor dimensions on the tcp volume dependence is explored. The linear-quadratic Poissonian tumor control probability (tcp) model was modified to account for the possible dependence of clonogenic cell density and radiosensitivity parameters on tumor volume; then the original and modified versions of the model were fitted to published clinical and laboratory tumor control data. These different versions of the tcp model often fitted tumor control data equally well, because of the high degree of correlation between the parameters. Nevertheless the results were very different from a physical point of view and we suggest that sometimes it is possible to choose between equally good fits on the basis of physical considerations. Possible links between the volume dependence of the mean radiosensitivity and the degree of tumor hypoxia were also analyzed through a comparison of the results of the tcp fit to published measurements of oxygen tension in tumors.

Optimizing radiation parameters for cervical cancer

The treatment of cervical cancer has become increasingly sophisticated with evidence-based guidelines generated from randomized trials directing combined modality programs. The radiotherapeutic guidelines have been derived largely from single institutional experiences coupled with data from the Patterns of Care Studies. The design of external-beam fields has improved because of a better understanding of the anatomy of the cervix, uterus, parametrium, and draining lymph nodes from surgical, lymphangiogram, computed tomography scan, and magnetic resonance imaging series. An improvement in survival and local control with dose intensity (a reduction in overall treatment time and increase in overall dose) has been shown for cervical cancer, especially for locally advanced disease, and these series are highlighted. The use of intracavitary radiation, which is technically accurate, dramatically improves outcome and allows for dose intensity. Alternative brachytherapy techniques, such as high-dose-rate, and interstitial, are discussed. Ways to improve the therapeutic ratio for radiation, including biological factors, are reviewed. More research is necessary to understand the complex dose distribution of external-beam and intracavitary brachytherapy and its relationship to tumor control.

Treatment results and prognostic factors in inoperable carcinoma of the cervix treated with external plus high dose brachytherapy

Patients with inoperable carcinoma of the cervix treated with external plus high dose rate brachytherapy (HDRB), between 1988 and 1995 were evaluated retrospectively. According to stage, 5 year survival rates were 67.3% in stage IIb and 52.6% in stage III (P = 0001) and disease free survival (DFS) rates were 54.0% in stage IIb and 43.9% in stage III (P = 0.01). The following parameters were studied: age; stage; external beam dose; brachytherapy dose; total dose to point A; tumor mass; tumor response rate; bilateral or unilateral invasion of parametria in stage IIb; and bilateral or unilateral invasion of pelvic wall in stage IIIb; and the existence of hydronephrosis. The only significant parameter of 5 year survival and local control was tumor mass (P = 0.003).

Comparison of high dose rate, low dose rate, and high dose rate fractionated radiation for optimizing differences in radiosensitivities in vitro

Radiotherapy is administered with the assumption that all patients respond similarly to radiation although radiosensitivity does vary from patient to patient, resulting in different degrees of early and late effects. Because the dose given to a patient is limited by the response of normal tissue in the treatment field, it would be beneficial to determine the sensitivity of this normal tissue prior to therapy. Previous studies to predict radiosensitivity have used surviving fractions after a single dose given in vitro, however, differences in cell survival at this low level of kill are not easy to resolve. In this study, we set out to evaluate the use of alternative dose regimens which may better resolve differences in radiosensitivity. We have examined several radiation protocols for predictive value, including survival after high doses (6 Gy) at both high (112 cGy/min) and low (.882 cGy/min) dose rates and after fractionated doses of 2 Gy (6 fractions). A sensitive human fibroblast line (S11358) cultured from a patient showing severe effects after therapy is compared with a cell line (OMB1) cultured from an apparently normal subject. Differences between these cell lines have been compared with those between two human melanoma cell lines (SKMEL3 and HT144) which have shown resistant and sensitive response to radiation in vitro respectively. In both fibroblast and melanoma cell lines, the difference in the survival of normal and sensitive cells increased with increasing dose regardless of whether irradiation was delivered as low dose rate, high dose rate, or as fractionated doses. We propose that radiation doses which more closely mimic clinical treatment are more suitable than surviving fraction after 2 Gy (SF2) for in vitro evaluation of relative radiosensitivities of cell populations.

Rapid assay of intrinsic radiosensitivity based on apoptosis in human CD4 and CD8 T-lymphocytes

PURPOSE

An assay for radiosensitivity has numerous applications in the clinic. Avoidance of acute responses, prediction of normal tissue toxicity, and individualization of patient radiotherapy are included among these. We have developed a rapid assay (about 24 h) able to predict intrinsic radiosensitivity of CD4 and CD8 T-lymphocytes based on radiation-induced apoptosis.

METHODS AND MATERIALS

Fresh blood samples (1-2 ml in heparinized tubes) were irradiated with 0-, 2-, and 8-Gy X rays at a dose rate of approximately 3 Gy/min. Following irradiation, the cells were collected and prepared for flow-cytometric analysis and cell sorting. In conjunction with the CellQuest software available with the FACSVantage cell sorter (Becton-Dickinson), two T-lymphocyte types were analyzed on the basis of their cell-specific antigens (CD4 and CD8), and DNA was stained with DAPI. Following the separation of these cell types, radiation-induced cell death was assessed. Cytotoxicity was characterized by gradual degradation of internucleosomal DNA which results in a sub-G1 peak on the DNA histogram, and by the associated loss of surface antigens causing an intermediate positive peak in the antibody histogram. Using the assay, we investigated the interdonor variation in a cohort of 45 healthy adult blood donors and 5 children [one had immunodeficiency, centromeric instability, and facial anomalies syndrome (ICF), and one had ataxia telangiectasia (AT)]. Intradonor variation was assessed with 10 different experiments from a single donor.

RESULTS

CD4 and CD8 T-lymphocyte radiosensitivities were correlated (r = 0.63 and 0.65 for 2 and 8 Gy, respectively) in 45 adult donors. Both for CD4 and CD8 cells, 2 and 8 Gy irradiation responses showed a good correlation (r = 0.77 for both). Interdonor variation was significantly higher than intradonor variation (p < 0.0005) for all CD4 and CD8 data. We observed a decrease in the antigen fluorescence of dying cells, a phenomenon referred to as antigen-ebb. Antigen-ebb was clearly observed in both cell types, and correlated significantly with cytotoxicity. A trend was observed between radiosensitivity and donor age, but there was no correlation for gender. Blood from a 4-year-old girl presenting with ICF demonstrated compromised radiation-induced cytotoxicity in her CD4 T-lymphocytes, and an 11-year-old boy presenting with AT demonstrated compromised radiation-induced cytotoxicity in both his CD4 and CD8 T-lymphocytes.

CONCLUSION

We conclude that the assay provides a rapid means of determining radiosensitivity, can discriminate differences in radiation-induced cytotoxicity between individuals, and can be used as a rapid screen for genetically hypersensitive patients. Antigen-ebb offers interesting possibilities for molecular biological investigations, permitting characterization and isolation of abnormal but vital cells in the absence of clastogenic agents.

Proliferation and hypoxia in human squamous cell carcinoma of the cervix: first report of combined immunohistochemical assays

PURPOSE

To characterize the distribution of hypoxia and proliferation in human squamous cell carcinoma of the cervix via an immunohistochemical approach prior to initiation of therapy.

METHODS AND MATERIALS

Patients with primary squamous cell carcinoma of the cervix uteri received a single infusion of the 2-nitroimidazole, pimonidazole (0.5 g/m2 i.v.), and 24 h later punch biopsies of the primary tumor were taken. Tissue was formalin fixed, paraffin embedded, and sectioned for immunohistochemistry. Hypoxia was detected by monoclonal antibody binding to adducts of reductively activated pimonidazole in malignant cells. Staining for endogenous MIB-1 and PCNA was detected in tumor cells via commercially available monoclonal antibodies. Point counting was used to quantitate the fraction of tumor cells immunostained for MIB-1, PCNA, and hypoxia marker binding.

RESULTS

Immunostaining for pimonidazole binding was distant from blood vessels. There was no staining in necrotic regions, and only minimal nonspecific staining, mostly in keratin. In general, cells immunostaining for MIB-1 and PCNA did not immunostain for pimonidazole binding. Cells immunostaining for MIB-1 and PCNA showed no obvious geographic predilection such as proximity to vasculature. Quantitative comparison showed an inverse relationship between hypoxia marker binding and proliferation.

CONCLUSIONS

Immunohistochemical staining for pimonidazole binding is consistent with the presence of hypoxic cells in human tumors and may be useful for estimating tumor hypoxia prior to radiation therapy. Immunostaining for pimonidazole binding is an ideal complement to immunohistochemical assays for endogenous proliferation markers allowing for comparisons of tumor hypoxia with other physiological parameters. These parameters might be used to select patients for radiation protocols specifically designed to offset the negative impact of hypoxia and/or proliferation on therapy. The inverse relationship between pimonidazole binding and proliferation markers is a preliminary result requiring verification.

Theory and practice of predictive assays in radiation therapy

PURPOSE

An overview of the field of predictive assays is presented. It has been written with the many clinicians and scientists in mind who would like to become better acquainted with the general scope, principles and themes in the field.

RESULTS

Predictive assays have yielded much valuable information about the radiobiology of tumors e.g. the overall treatment time for rapidly proliferating tumors should be kept to a minimum. However, alteration of current treatment protocols based on results from predictive assays is still a matter of debate. What justification do we have to change established treatment protocols? A necessary and sufficient justification would be when the test value indicated an alternative treatment producing a better outcome, i.e. higher survival, improved local control, etc. Necessary but not always sufficient justification is correlation between the parameter measured and clinical outcome, if insufficient clinical benefit can be derived even when this is known. It is not sufficient that a test be demonstrated to be discriminatory. It must discriminate a sufficient number of patients, and its use must provide the patient with useful therapeutic alternatives. These parameters measured by predictive assays may well interact radiobiologically, and restricting observations to just one assay is probably insufficient for reliable indications. In the future, it is more likely that a panel of tests will be performed, and clinical decisions based on multi-parametric analysis of biopsy material.

CONCLUSION

In the following overview general predictive assay theory is presented followed by a brief introduction to some of the more established assays and finally some guidelines are suggested for the development of new assays.

Biologic basis of radiation therapy

The biologic effects of ionizing radiation are well understood. The limitations of radiation therapy time-dose schemes typically used in veterinary medicine are also well understood. Before expensive and potentially toxic combinations of treatment, such as radiation combined with chemotherapy or radiation combined with hyperthermia, can be fully understood, the effect of optimizing the manner in which radiation itself is administered must first be defined. This will only occur after a sufficient period of observation after improvement of the radiation time-dose schemes in use today. Also, when evaluating historic data regarding the response of canine and feline tumors to irradiation, the time-dose scheme used must be considered. Many papers were published based on coarsely fractionated schemes using large doses per fraction and relatively low total doses. Thus, the response rates published must be tempered by the fact that it may be possible to obtain better tumor control rates using smaller doses per fraction and a larger total dose.

The p53 gene as a modifier of intrinsic radiosensitivity: implications for radiotherapy

BACKGROUND AND PURPOSE

Experimental studies have implicated the normal or "wild type' p53 protein (i.e. WTp53) in the cellular response to ionizing radiation and other DNA damaging agents. Whether altered WTp53 protein function can lead to changes in cellular radiosensitivity and/or clinical radiocurability remains an area of ongoing study. In this review, we describe the potential implications of altered WTp53 protein function in normal and tumour cells as it relates to clinical radiotherapy, and describe novel treatment strategies designed to re-institute WTp53 protein function as a means of sensitizing cells to ionizing radiation.

METHODS AND MATERIALS

A number of experimental and clinical studies are critically reviewed with respect to the role of the p53 protein as a determinant of cellular oncogenesis, genomic stability, apoptosis, DNA repair and radioresponse in normal and transformed mammalian cells.

RESULTS

In normal fibroblasts, exposure to ionizing radiation leads to a G1 cell cycle delay (i.e. a "G1 checkpoint') as a result of WTp53 mediated inhibition of G1-cyclin-kinase and retinoblastoma (pRb) protein function. The G1 checkpoint response is absent in tumour cells which express a mutant form of the p53 protein (i.e. MTp53), leading to acquired radioresistance in vitro. Depending on the cell type studied, this increase in cellular radiation survival can be mediated through decreased radiation-induced apoptosis, or altered kinetics of the radiation-induced G1 checkpoint. Recent biochemical studies support an indirect role for the p53 protein in both nucleotide excision and recombinational DNA repair pathways. However, based on clinicopathologic data, it remains unclear as to whether WTp53 protein function can predict for human tumour radiocurability and normal tissue radioresponse.

CONCLUSIONS

Alterations in cell cycle control secondary to aberrant WTp53 protein function may be clinically significant if they lead to the acquisition of mutant cellular phenotypes, including the radioresistant phenotype. Pre-clinical studies suggest that these phenotypes may be reversed using adenovirus-mediated gene therapy or pharmacologic strategies designed to re-institute WTp53 protein function. Our analysis of the published data strongly argues for the use of functional assays for the determination of WTp53 protein function in studies which attempt to correlate normal and tumour tissue radioresponse with p53 genotype, or p53 protein expression.

Relationship between DNA damage, rejoining and cell killing by radiation in mammalian cells

The prevailing hypothesis on the mechanism of radiation-induced cell killing identifies the genetic material deoxyribonucleic acid (DNA) as the most important subcellular target at biologically relevant doses. In this review we present new data and summarize the role of the DNA double-strand breaks (dsb) induced by ionizing radiation and DNA dsb rejoining as determinants of cellular radiosensitivity. When cells were irradiated at high dose-rate, two molecular end-points were identified which often correlated with radiosensitivity: (1) the apparent number of DNA dsb induced per Gy per DNA unit and (2) the half-time of the fast component of the DNA dsb rejoining kinetics. These two molecular determinants, not mutually exclusive, may be linked through a common factor such as the conformation of DNA.

Younger age as a bad prognostic factor in patients with carcinoma of the cervix

OBJECTIVE

To verify the influence of age on the prognosis of cervix carcinoma.

STUDY DESIGN

Five hundred and sixty eight patients treated for a FIGO stage IB-IVA with radical irradiation in the Centre Hospitalier Universitaire Vaudois of Lausanne were subdivided according to the following age categories: < or = 45, 46-60, 61-69 and >70 years. Taking the 46-60 years age group as the reference, the hazard ratios (HR) of death and corresponding 95% confidence intervals (95% CI) were estimated by means of a Cox multivariate analysis.

RESULTS

The 5-year survival rates were, respectively, 57%, 67%, 60% and 45%. For the youngest women the risk of death was significantly increased (HR = 2.00, 95% CI [1.32-3.00]) and was even more accentuated in advanced stages.

CONCLUSION

Age under 45 years is a bad prognostic factor in carcinoma of the cervix.