The challenge of p53 as prognostic and predictive factor in gliomas

In recent years, increasing interest in genetic abnormalities and biologic factors such as the tumour suppressor gene p53 as possible predictive and prognostic factor in gliomas has emerged. Inactivation of p53 can result in resistance to apoptosis, one of the mechanisms thought to explain the failure to respond to DNA-damaging agents. Thus, inactivation of p53 might be associated with a worse prognosis. Considering the inconsistent results of several recent studies, it has remained controversial whether p53 actually can be related to response to treatment and patients' prognosis. Therefore, a systematic review of the literature was performed, which included 28 publications. Techniques for assessing the inactivation of p53 varied widely. Overall, approximately 50% or more of astrocytoma specimens evaluated by immunohistochemistry stained positively for p53, regardless of histologic grade. Eight studies were restricted to comparably treated patients within a single histologic group. In most instances, non-restrictive inclusion criteria and use of statistical methods, which were not sufficient to correct the possible bias, make it difficult to reach unequivocal conclusions. However, it appears that the prognostic information of p53 is at best marginal, especially when compared to established parameters such as grading, age, etc. Its predictive value, which most likely is rather limited too, can hardly be judged without prospective studies also evaluating other biological factors as well as end-points other than time to radiological progression.

Long-term adverse effects of radiation inhibition of restenosis: radiation injury to the aorta and branch arteries in a canine model

PURPOSE

To determine the long-term effects of irradiation on large arteries in view of the possible use of radiation to prevent restenosis after angioplasty.

METHODS AND MATERIALS

Groups of dogs received 10-55 Gy single-dose alone, or in combination with 50 Gy in 2-Gy fractions, or 50-80 Gy in 2-2.7-Gy fractions to an 8-cm length of aorta and branch arteries. Single doses were delivered intraoperatively. Two or 5 years after irradiation, aortas and branch arteries were evaluated histomorphometrically to determine areas of intima, media, and adventitia, and qualitatively to determine other adverse effects.

RESULTS

Intimal area increased at single doses < 20 Gy and after all fractionated doses, but was normal at doses > 20 Gy 2 years after irradiation. Intimal area was greater at 5 years than at 2 years after irradiation. Adventitial area increased with increasing dose at 2 and 5 years after irradiation. Thrombosis of the aorta and branch arteries occurred at 4-5 years after irradiation with ED50s of 29.7 Gy and about 25 Gy, respectively, but did not occur after fractionated irradiation.

CONCLUSION

Intimal proliferation is inhibited at single doses > 20 Gy, but may be stimulated at single doses of < 20 Gy or after fractionated irradiation. Adventitial fibrosis increases with increasing dose and could contribute to adverse late vascular remodeling. Severe adverse effects were not evident until 4-5 years after irradiation at does of > 20 Gy to an 8-cm vessel length.

Frequency of first metastatic events in breast cancer: implications for sequencing of systemic and local-regional treatment

PURPOSE

The sequencing of treatment for early breast cancer is controversial. The purpose of this study was to quantify the risk of delaying surgery, using estimates of the frequency of first metastases from breast primary tumors.

PATIENTS AND METHODS

The probability that 560 (node-negative), 657 (with one to three positive nodes), and 505 (with more than three positive nodes) women treated without adjuvant chemotherapy would be free of distant disease at presentation was fit to a mathematical model of the seeding of distant metastases and combined with estimates of the growth rate to calculate the frequency of first distant disseminations per month.

RESULTS

Frequencies of first distant metastases were approximately 1% to 2% per month, 2% to 4% per month, and 3% to 6% per month in T1 patients who were node-negative, had one to three positive nodes, or more than three positive nodes, respectively. As a result, the typical patient with T1 disease, who has a 70% to 80% chance of being free of distant disease, runs a 1% to 4% risk of distant dissemination for each month surgery is delayed. Assuming a 30% reduction in mortality caused by adjuvant chemotherapy, the model predicts that T1 patients treated with neoadjuvant chemotherapy would potentially have a higher rate of distant metastasis development than those treated with an initial surgical resection followed by adjuvant chemotherapy.

CONCLUSION

We formulate the hypothesis that optimal sequencing of surgery and systemic treatment of breast cancer may be size-dependent, with a disadvantage or no benefit from neoadjuvant treatment for T1 patients but an increasing benefit with increasing size of the primary tumor.

Radiation therapy for clinically localized prostate cancer: a multi-institutional pooled analysis

CONTEXT

Prostate-specific antigen (PSA) evaluation leads to the early detection of both prostate cancer and recurrences following primary treatment. Prostate-specific antigen outcome information on patients 5 or more years following treatment is limited and available mainly as single-institution reports.

OBJECTIVES

To assess the likelihood and durability of tumor control using PSA evaluation 5 or more years after radical external beam radiation therapy and to identify pretreatment prognostic factors in men with early prostate cancer treated since 1988, the PSA era.

DESIGN AND SETTING

Retrospective, nonrandomized, multi-institutional pooled analysis of patients treated with external beam radiation therapy alone between 1988 and 1995 at 6 US medical centers. Follow-up lasted up to a maximum of 9 years. Outcome data were analyzed using Cox regression and recursive partitioning techniques.

PATIENTS

A total of 1765 men with stage T1b, T1c, and T2 tumors treated between 1988 and 1995 with external beam radiation. The majority (58%) of patients were older than 70 years and 24.2% had initial PSA values of 20 ng/mL or higher. A minimum of 2 years of subsequent follow-up was required for participation.

MAIN OUTCOME MEASURE

Actuarial estimates of freedom from biochemical failure.

RESULTS

The 5-year estimates of overall survival, disease-specific survival, and the freedom from biochemical failure are 85.0% (95% confidence interval [CI], 82.5%-87.6%), 95.1% (95% CI, 94.0%-96.2%), and 65.8% (95% CI, 62.8%-68.0%), respectively. The PSA failure-free rates 5 and 7 years after treatment for patients presenting with a PSA of less than 10 ng/mL were 77.8% (95% CI, 74.5%-81.3%), and 72.9% (95% CI, 67.9%-78.2%). Recursive partitioning analysis of initial PSA level, palpation stage, and the Gleason score groupings yielded 4 separate prognostic groups: group 1, included patients with a PSA level of less than 9.2 ng/mL; group 2, PSA level of at least 9.2 but less than 19.7 ng/mL; group 3, PSA level at least 19.7 ng/mL and a Gleason score of 2 to 6; and group 4, PSA level of at least 19.7 ng/mL and a Gleason score of 7 to 10. The estimated rates of survival free of biochemical failure at 5 years are 81 % for group 1, 69% for group 2, 47% for group 3, and 29% for group 4. Of the 302 patients followed up beyond 5 years who were free of biochemical disease, 5.0% relapsed from the fifth to the eighth year.

CONCLUSIONS

Estimated PSA control rates in this pooled analysis are similar to those of single institutions. These rates indicate the probability of success for subsets of patients with tumors of several prognostic category groupings. These results represent a multi-institutional benchmark for evidence-based counseling of prostate cancer patients about radiation treatment.

Fractionation sensitivities and dose-control relations of head and neck carcinomas: analysis of the randomized hyperfractionation trials

PURPOSE

A therapeutic benefit can be achieved by hyperfractionation (HF) if tumours have small fractionation sensitivities characterized by alpha/beta values greater than those for late effects of dose limiting normal tissues. It is the purpose of the present paper to estimate alpha/beta values for head and neck carcinomas from randomized HF trials.

MATERIALS AND METHODS

Maximum likelihood estimates the alpha/beta ratio were obtained from tumour control data from the randomized HF trials using the LQ model and a logit or probit type dose-response curve. A joint analysis of five randomized HF trials for head and neck carcinomas was performed to estimate overall alpha/beta and gamma50 values for tumour control. In addition, alpha/beta ratios for the individual trials were estimated using fixed gamma50 values (characteristic quantifying the steepness of dose-response curves) between 1.4 and 5 for tumours.

RESULTS

An overall gamma50 of 3.1 (1.5-4.7) was estimated for the dose-tumour control relation from the HF trials, assuming a logit or probit dose-response curve. The tumours showed small fractionation sensitivities characterized by an overall alpha/beta of 10.5 (6.5-29) Gy. One trial allowed quantitative estimation of the alpha/beta values for late normal tissue damage: The alpha/beta estimate for late effects of grade 2 + was 4.0 (3.3-5.0) Gy, assuming a fixed gamma50 of 5 and was even smaller for smaller gamma50 values.

CONCLUSION

Head and neck carcinomas showed small fractionation sensitivities with alpha/beta values greater than those typical for bone, soft tissues, and skin, as well as steep dose response curves. Thus, important prerequisites for improving the therapeutic benefit of radiotherapy of head and neck carcinomas by HF are fulfilled for patients who met the accession criteria of the trials.

Induction of transforming growth factor alpha in irradiated mouse jejunum

PURPOSE

To determine the involvement of the mitogenic growth factors transforming growth factor alpha (TGF alpha), epidermal growth factor (EGF), and the EGF receptor (EGF-R) in the proliferative response after irradiation of the mouse jejunum.

METHODS AND MATERIALS

C3Hf/Kam mice were whole-body irradiated with 5 and 11 Gy 250 kV X rays. Mice were killed 1-10 days after irradiation, and immunohistochemistry, in situ hybridization (ISH), and RNase protection assays were performed.

RESULTS

Damage to the jejunal crypts caused by irradiation resulted in a strong proliferative response 1-5 days after 5 Gy and 3-6 days after 11 Gy. Expression of TGF alpha, EGF, and EGF-R increased at 1-2 days and decreased at 4-8 days after 5- or 11-Gy irradiation. Also, TGF alpha mRNA increased during the early phase of the proliferative response (1-2 days after 5 or 11 Gy) followed by a decrease at 4 days after 5 Gy and 8 days after 11 Gy.

CONCLUSION

These data indicate that, at the beginning of the proliferative response after irradiation, the transcription of TGF alpha mRNA is increased, and that it is inhibited just before compensatory proliferation decreases. Thus, active regulation of TGF alpha expression takes place at least at the transcriptional level, resulting in upregulation of TGF alpha production and increased TGF alpha levels in the crypts during the proliferative response.

Effects of volume irradiated on the function of the canine ureter

This study was designed to investigate the influence of the volume irradiated on the probability of ureteral complications and to provide data for volume modeling. One hundred thirty-four purpose-bred beagle dogs received single intraoperative doses of 6 MeV electrons ranging from 12 to 54 Gy to three lengths of ureter: 2, 4 or 8 cm. The response was evaluated by excretory urography. The ED50 was 21.9 Gy (95% CI 13.3-30 Gy) for 8 cm 3 years after treatment. The estimated ED50's were greater than 43 Gy for 4 cm and 85 Gy for 2 cm. Reducing the length of ureter irradiated from 8 cm to 4 cm increased the ED50 for ureteral dilation by at least a factor of 2, while reduction from 8 cm to 2 cm increased the ED50 by at least a factor of 4. The ED50 for renal injury secondary to stenosis was 30.5 Gy (95% CI 17.2-232 Gy) when an 8-cm field was irradiated. There was a significant effect of volume irradiated on the frequency of ureteral stenosis. Reducing the length of ureter included in the treatment field should allow delivery of higher doses to tumors without increased complications.

A morphometric analysis of glomerular and tubular alterations following fast-neutron irradiation of the pig and monkey kidney

PURPOSE

The morphologic responses of the pig and monkey kidney to fractionated fast-neutron irradiation were assessed.

METHODS AND MATERIALS

The right kidney of approximately 14-week-old female Large White pigs was irradiated with 6.6-12.2 Gy of fast neutrons (42 MeVd-->Be) given as 12 fractions over 18 days; the left kidney served as the contralateral unirradiated kidney. Both kidneys were removed at necropsy 2 years postirradiation. In addition, the remaining hypertrophied kidney of four unilaterally nephrectomized adult rhesus monkeys was irradiated with a total dose of 11.0 Gy fast neutrons (45 MeVp-->Be) given in an identical fractionation regimen to that used in the pig studies. These kidneys were removed when the animals exhibited renal failure, between 32-94 weeks postirradiation. Glomeruli were assessed for the presence of pathologic features, including intercapillary eosinophilic material (ICE), ectatic capillaries, thrombi, hemorrhage, and sclerosis. The relative proportion of renal cortex occupied by glomeruli, interstitium, normal, or abnormal tubules was determined using a Chalkley point grid.

RESULTS

The incidence of normal glomeruli, ectatic capillaries, thrombosis, and periglomerular fibrosis were significantly different in the irradiated pig kidneys compared with the unirradiated contralateral kidneys (p < or = 0.02). Linear regression analysis demonstrated a significant dose relationship in terms of normal glomeruli, ectatic capillaries, and ICE (r > or = 0.64; p < or = 0.04). Irradiation was also associated with a significant (p < 0.0001) decrease and increase in the volume of renal cortex occupied by normal and abnormal tubules, respectively. Similar morphometric changes were noted in the irradiated monkey kidneys.

CONCLUSIONS

The morphologic changes seen in the pig and monkey kidney after fractionated irradiation with fast neutrons are similar to those previously noted after single-dose or fractionated-photon irradiation. These findings support the hypothesis that the development of radiation nephropathy in these various models involves common pathophysiological mechanisms.

Fractionation effect on radiation-induced growth retardation of tibia in rabbits and rats

A study of the sensitivity to fractionation of the growing tibia of rabbits and rats was conducted by comparing the growth of the treated right bone to that of the untreated left side in each individual animal using radiographic measurements. The experimental endpoint was the percentage of normal growth 24 weeks after irradiation in rabbits and 14 weeks after treatment in rats. The results show clear dose-response relationships in all experimental arms. A clear-cut fractionation effect was demonstrated in both species. The alpha/beta-ratios determined by maximum likelihood analysis according to the LQ-model with graded responses were 3.2 Gy (95% C.I. 1.1; 5.6) in rabbits and 6.9 Gy (5.3; 8.7) in rats, when all data were included in the calculations. When single-dose data were excluded the alpha/beta-values were -0.6 Gy (-3.1; 2.3) in rabbits and 5.0 Gy (3.5; 7.0) in rats. Our data provide further evidence that low doses per fraction should be used when irradiation of the epiphysis cannot be avoided in pediatric patients.

Tumor volume: a basic and specific response predictor in radiotherapy

BACKGROUND AND PURPOSE

Predictive assays of the response of tumor and normal tissues in individual patients offer the possibility of individualized prognosis and treatment decisions. For this purpose a variety of assays are currently being explored. The impact of tumor volume on radiotherapy outcome has long been recognized and in this paper its predictive potential is investigated.

METHODS

Re-evaluation of clinical data from the literature.

RESULTS

Tumor volume significantly influences radiotherapy outcome and in many sites it is likely a superior prognostic indicator to tumor stage, which reflects tumor size only partially and is mainly correlated to operability. Tumors even of identical stage may vary by factors of more than 100 in volume and neglect of this heterogeneity clearly reduces the power of a study considerably. The precision requirements for the measurement of tumor volume are small; +/-50% is sufficient for reasonable results.

CONCLUSION

The data evaluated here suggest that tumor volume is the most precise and most relevant predictor of radiotherapy outcome. Its determination is achievable with sufficient accuracy in most radiotherapy departments. Individual tumor volume should always be reported in clinical studies and considered in data analyses.

Tumor response, mucosal reactions and late effects after conventional and hyperfractionated radiotherapy

BACKGROUND

Relationships between normal tissue reactions and tumor response to radiotherapy have generally been investigated in retrospective studies, with the attendant difficulties such as different times of treatment and lack of standard scales for scoring of normal tissue reactions. This study analyses the correlation between normal tissue reactions and tumor response in a randomized trial of hyperfractionation versus conventional radiotherapy.

MATERIALS AND METHODS

EORTC trial 22791, which accrued 325 T2-3, N0-1 and M0 oropharynx squamous cell carcinomas, compared conventional radiotherapy (70 Gy in 7 weeks) to a hyperfractionated regime (two daily irradiations of 1.15 Gy up to 80.5 Gy in 7 weeks). Acute and late toxicities were assessed according to the RTOG/EORTC scales. The variables were tumor regression at treatment completion, tumor control for unlimited follow-up, severity of acute mucosal reactions (grade of the peak reaction, time to onset of grade 2 mucositis, or duration of acute reactions of grade 3) and severity of late effects in normal tissues (late ulceration, cervical edema secondary to lymphatic drainage damage, late muscular fibrosis, or late mucosal necrosis as consequential damage). Kendall's rank correlation was used to assess the levels of significance of the correlation. The 95% confidence interval (95% CI) was calculated for each correlation tau-b coefficient.

RESULTS

Irradiation doses and overall treatment times were consistent between the treatment arms. The time to onset of patchy mucosal reactions was inversely correlated to tumor regression at treatment completion in the hyperfractionated arm (arm 2) but not in the conventional fractionation arm (arm 1). The other significant correlations were restricted to the following pairs of end-points and patient subgroups: acute mucositis of grade 3 versus tumor regression at the end of treatment in arm 2 for T2 tumors, late ulceration versus tumor control in arm 2 and acute mucosal reactions versus late effects in normal tissues in arm 2 for T3 tumors. By and large, the 95% CIs for Kendall's tau-b included zero and did not include 0.5, an indication that the comparison had sufficient power to detect a difference, if indeed one existed.

CONCLUSIONS

These results do not represent clinical evidence strong enough to demonstrate that individual differences in sensitivity influence the response of tumors to radiation.

Diurnal variations in the expression of radiation-induced apoptosis

Experiments were performed to determine whether diurnal variations in apoptosis in the mouse small intestine after irradiation with 2.5 Gy gamma rays depended on the time of day that the mice were irradiated, the time of day that the mice were sacrificed or the interval between irradiation and sacrifice. Experiments were performed with a 12-h light:dark regimen with the light period from 6:00 to 18:00 h. With fixed intervals of 6 h and 24 h between irradiation and sacrifice, a peak in induced apoptosis (16%) was observed in mice sacrificed at 8:00 h, two times higher than the nadir of response at 23:00 h (8%). When variable intervals were used between irradiation and measurement of apoptosis, i.e. sacrifice, at 8:00 h or 23:00 h, the induced apoptosis was dependent on the interval, with a peak for 18-h intervals. However, the level of apoptosis was always about twofold higher when measured at 8:00 h than at 23:00 h. No correlation was observed between diurnal variations in apoptosis and survival of mouse intestinal crypts. The diurnal variations in apoptosis after irradiation can be interpreted either in terms of expression of apoptosis during the G2/M phase of the cell cycle in partially synchronized cells, or in terms of a systemic mechanism such as diurnal variation in the neurohormone melatonin.

Volume effects in the irradiated canine spinal cord: do they exist when the probability of injury is low?

PURPOSE

The purpose of this study was to investigate volume effects in the irradiated canine spinal cord.

MATERIALS AND METHODS

Eighty-nine beagle dogs were given 44-84 Gy photons in 4 Gy fractions to 4 or 20 cm lengths of thoracic spinal cord. As controls, 36 dogs were given 60-84 Gy in 2 Gy fractions to a 20 cm length of spinal cord and six dogs were unirradiated. Dogs were evaluated for clinical signs, and after euthanasia, for occurrence of gross lesions, severe lesions of massive hemorrhage, white matter necrosis and/or parenchymal atrophy and mild lesions of focal fiber loss. White matter vacuoles, meningeal thickness and dorsal root ganglia lesions were quantified. Data were analyzed to test for an effect of volume on dose-response curves.

RESULTS

Significant volume effects were found between 4 and 20 cm lengths of irradiated spinal cord for gross lesions, severe lesions and mild lesions (8.3-15.0 Gy difference at the ED50 level). The ED50 in 4 Gy fractions for severe lesions was 56.9 Gy (95% CI 53.1-60.6) for 20 cm and 68.8 Gy (95% CI 64.5-75.1) for 4 cm fields. Significant improvements in the fit of data to dose-response curves resulted when using models with either parallel or non-parallel curves, but in either case an appreciable difference existed between curves at low probabilities of injury. Volume effects were present for meningeal thickness and slopes of dose-response curves were different. Clinical signs correlated well with severe lesions for 20 cm (ED50 = 54.0 Gy), but not for 4 cm fields (ED50 = 77.6 Gy).

CONCLUSIONS

Volume effects exist for the occurrence of pathologic lesions in irradiated canine spinal cord. Clinical compensation for pathologic lesions occur at small, but not large irradiated volumes. There is insufficient data to support a decreased slope of dose-response curves with decreased volume. Volume effects estimated at the 50% level of spinal cord injury could also hold at low probabilities of injury characteristic of the clinic.

The effect of proliferative status and clonogen content on the response of mouse jejunal crypts to split-dose irradiation

The rate of cell production in hierarchical tissues is affected by the differentiation probability after each clonogen division and the frequency with which divisions take place. We have modified the latter by a high-fiber diet, which caused an increase in the BrdUrd labeling index (LI) in jejunal crypts of mice, and have tested for a change in tolerance using the in vivo colony assay. Clonogens were counted using the in vivo colony assay of crypt regeneration with Poisson correction. The LI was estimated by counting BrdUrd-labeled cells in longitudinal sections of complete crypts. Arrest in mitosis induced by injection of paclitaxel was used to test for a difference in the rate of crypt cell production in mice fed low- and high-fiber diets. Split-dose studies were used to test whether the change in proliferative status of the crypts was accompanied by changes in either the number of clonogens per crypt or their radiosensitivity, or an increased proliferative response to radiation-induced cell killing. We found an increase in the crypt LI induced by the high-fiber diet was 15-25% and was dependent on the time of day. The data on arrest in mitosis did not demonstrate a difference in cell production rates based on diet, possibly because of insufficient resolution of the assay. We conclude that the high-fiber diet had no effect on radiosensitivity, the number of clonogens per crypt (again, within the resolution of the assay) or the "repopulated dose," the dose represented by the shift in the dose-response curve for 2.5 days relative to that for 6 h. When the number of clonogens at the start of rapid proliferation was different (on account of different first doses), the repopulated dose was the same when 5 Gy X rays was given first but was higher for the animals on the high-fiber diet when 12 Gy was given first. The high-fiber diet caused an increase in the LI in the crypts that was not accompanied by any change in radiosensitivity or, within the resolution of the assay, numbers of clonogens per crypt. The increased LI also did not result in an increase in clonogen repopulation between split (and equal) doses. However, in split-dose experiments where the first dose was higher and as a consequence the number of clonogens at the start of the proliferative response was lower, there was evidence of a higher rate of clonogen production with the high-fiber diet than with the low-fiber diet.

Hyperfractionated radiotherapy of human tumors: overview of the randomized clinical trials

PURPOSE

Hyperfractionation (HF) is the altered fractionation schedule most frequently studied in clinical Phase III trials. In this overview, surviving fractions, rates of complete responses, and estimates of the long-term locoregional tumor control probabilities after HF and conventional fractionated irradiation (CF) available from the various reports were compared.

METHODS AND MATERIALS

A metaanalysis was performed of the randomized studies on hyperfractionation vs. conventional fractionation published since 1980 on different tumor types in various locations.

RESULTS

Compared with CF, HF significantly reduced the odds of death for patients with head and neck tumors (three studies, odds ratio 0.48 (0.40-0.58), p < 0.0001) and bladder cancer (two studies, odds ratio 0.53 (0.36-0.78), p = 0.001), while there was a trend in nonsmall cell lung cancer (three studies, odds ratio 0.69 (0.51-0.95), p = 0.02), and malignant gliomas (three studies, odds ratio 0.67 (0.48-0.93), p = 0.02). The probability of long-term loco-regional control of head and neck tumors was significantly enhanced after HF (four studies, odds ratio for loco-regional recurrence or related events 0.35 (0.28-0.45), p < 0.0001). In trials on head and neck tumors and bladder cancer, complete responses were seen more often after HF compared with CF (odds ratio for failure of complete response: 0.43 (0.32-0.57), p < 0.0001, and 0.43 (0.27-0.70), p = 0.0007).

CONCLUSIONS

This overview demonstrates that the effectiveness of radiotherapy is consistently higher for HF than for CF. The assumption that tumors have a small effective fractionation sensitivity (alpha/beta > 5 Gy) seems to be fulfilled especially for head and neck cancers.