L.H. Gray Medal lecture: cell kinetics and radiation oncology

Clinical Results of Unconventional Fractionation Radiotherapy in Central Nervous System Tumors

Malignant brain tumors (primary and metastatic) are apparently resistant to most therapeutic efforts. Several randomized trials have provided evidence supporting the efficacy of radiation therapy. Attempts at improving the results of external beam radiotherapy include altered fractionation, radiation sensitizers and concomitant chemotherapy. In low-grade gliomas, all clinical studies with radiotherapy have employed conventional dose fractionation regimens. In high-grade gliomas, hypofractionation schedules represent effective palliative regimens in poor prognosis subsets of patients; short-term survival in these patients has not allowed to evaluate late toxicity. In tumors arising within the central nervous system, hyperfractionated irradiation exploits the differences in repair capacity between tumour and late responding normal tissues. It may allow for higher total dose and may result in increased tumor cell kill. Accelerated radiotherapy may reduce the repopulation of tumor cells between fractions. It may potentially improve tumor control for a given dose level, provided that there is no increase in late normal tissue injury. In supratentorial malignant gliomas, superiority of accelerated hyperfractionated over conventionally fractionated schedules was observed in a randomized trial; however, the gain in survival was less than 6 months. At present no other randomized trial supports the preferential choice for altered fractionation irradiation. Also in pediatric brainstem tumors there are no data to confirm the routine use of hyperfractionated irradiation, and significant late sequelae have been reported in the few long-term survivors. Shorter treatment courses with accelerated hyperfractionated radiotherapy may represent a useful alternative to conventional irradiation for the palliation of brain metastases. Different considerations have been proposed to explain this gap between theory and clinical data. Patients included in dose/effect studies are not stratified by prognostic factors and other treatment-related parameters. This observation precludes any definite conclusion about the relative role of conventional and of altered fractionation. New approaches are currently in progress. More prolonged radiation treatments, up to higher total doses, could delay time to tumor progression and improve survival in good prognosis subsets of patients; altered fractionation may be an effective therapeutic tool to achieve this goal.

The Efficacy of Different Follow-Up Strategies in Clinical Stage I Non-Seminomatous Germ Cell Cancer: A Markov Simulation Study

OBJECTIVE

There is no universally accepted standard protocol for surveillance of patients with clinical stage I Non Seminomatous Germ Cell Tumors (CS I NSGCT). Prospective studies to compare different follow-up policies have not been performed, even though a great deal of time and resources is spent in surveillance. In this study, we constructed a Markov model to evaluate the impact of different follow-up strategies on disease-specific mortality (DSM) and life expectancy (LE) of patients with CS I NSGCT.

METHODS

A discrete time non-homogeneous semi-Markov model was used to simulate different follow-up strategies for a hypothetical population of CS I NSGCT patients. Estimates of the model parameters were based on the literature. Output parameters were DSM and LE. Three different strategies were compared: (1) the intensive The Netherlands Cancer Institute/Antoni van Leeuwenhoek hospital (NCI/AvL) protocol; (2) the European Association of Urology (EAU) protocol; and (3) a hypothetical minimal protocol (i.e. follow-up limited to the first two years). Furthermore, we evaluated the impact of abdominal CT scans and chest X-rays on DSM.

RESULTS

Comparing with the EAU protocol (DSM: 3.05%; LE: 53.3 years), the intensive NCI/AvL protocol leads to a 1.2% lower DSM and a 6 months higher LE (DSM: 1.81%; LE: 53.9 years). The hypothetical follow-up scenario during the first two years shows a DSM of 6.83% and an LE of 51.4 years. Abdominal CT scans of the retroperitoneal lymph nodes appear to be important, while chest X-rays have little impact on DSM.

CONCLUSION

A follow-up policy limited to the first two years will result in an unacceptable high percentage of death from disease (6.83%). The relatively small benefit of an intensive follow-up protocol as proposed by the NCI/AvL, compared to that of the EAU, must be weighed against its economic and psychological costs. Our model suggests that CT-scanning is essential for a low DSM, whereas the large number of X-rays seem to have little additional effect.

Role of cell cycle in mediating sensitivity to radiotherapy

Multiple pathways are involved in maintaining the genetic integrity of a cell after its exposure to ionizing radiation. Although repair mechanisms such as homologous recombination and nonhomologous end-joining are important mammalian responses to double-strand DNA damage, cell cycle regulation is perhaps the most important determinant of ionizing radiation sensitivity. A common cellular response to DNA-damaging agents is the activation of cell cycle checkpoints. The DNA damage induced by ionizing radiation initiates signals that can ultimately activate either temporary checkpoints that permit time for genetic repair or irreversible growth arrest that results in cell death (necrosis or apoptosis). Such checkpoint activation constitutes an integrated response that involves sensor (RAD, BRCA, NBS1), transducer (ATM, CHK), and effector (p53, p21, CDK) genes. One of the key proteins in the checkpoint pathways is the tumor suppressor gene p53, which coordinates DNA repair with cell cycle progression and apoptosis. Specifically, in addition to other mediators of the checkpoint response (CHK kinases, p21), p53 mediates the two major DNA damage-dependent cellular checkpoints, one at the G(1)-S transition and the other at the G(2)-M transition, although the influence on the former process is more direct and significant. The cell cycle phase also determines a cell's relative radiosensitivity, with cells being most radiosensitive in the G(2)-M phase, less sensitive in the G(1) phase, and least sensitive during the latter part of the S phase. This understanding has, therefore, led to the realization that one way in which chemotherapy and fractionated radiotherapy may work better is by partial synchronization of cells in the most radiosensitive phase of the cell cycle. We describe how cell cycle and DNA damage checkpoint control relates to exposure to ionizing radiation.

Delay in the diagnosis of breast cancer: medico-legal implications

Delay in the diagnosis of breast cancer is an important cause of medical malpractice claims which if trends continue, will threaten healthcare budgets. Most malpractice claims are made by younger women. Delay is most frequently due to the physician failing to be impressed with the clinical findings, or to a false negative mammogram report. Diagnosis of breast cancer is more difficult in younger women, because of the poor sensitivity of diagnostic tests and the high prevalence of benign disease in this age group. Models of tumour growth suggest that the potential to metastasize may be present before the tumour is clinically detectable and that if the growth rate of a given tumour is constant, any clinical delay is a small proportion of the lifespan of the tumour. Patient delay is generally associated with more advanced lesions at presentation, but the effect of delay on survival or what period of delay is significant remains uncertain. Delay in the diagnosis of breast cancer is likely to cause the patient considerable anxiety, especially when the public understands that the aim of mammographic screening is to diagnose breast cancer at an early stage in order to effect a cure. For a plaintiff to successfully claim in court she must prove that she has suffered an injury, and that the injury was the result of negligent medical practice. It is easier to defend a case of delay in diagnosis if the documentation is in order and all the appropriate tests have been performed.

The link between local recurrence and distant metastases in human breast cancer

PURPOSE

To distinguish between two possible explanations for the increased incidence of distant metastases observed in patients with locoregional recurrences (LR). Either LR is the signature of tumor aggressiveness, and avoiding recurrences (i.e., by radiotherapy) is of little value. The alternative is that LR is a nidus for metastatic dissemination.

METHODS AND MATERIALS

Four thousand patients consecutively treated in the same institution from 1954 to 1975 were studied. None of them had received adjuvant chemotherapy. Tumor characteristics, local recurrence, and distant metastases had been prospectively registered. Duration of metastatic growth and probability of metastatic dissemination were estimated in the subsets of patients.

RESULTS

The proportion of metastasis-free patients was reduced by about 80% in all subsets of patients with LR. In patients without LR, the monthly rate of distant metastases incidence decreases continuously with time after initial treatment. Conversely, in patients with local recurrence, this rate increases during the first year at initial treatment and the metastases in excess appear slightly later than in patients without local recurrence. Using a mathematical model, it can be shown that, in patients with local recurrence, nearly all of the metastases in excess had been initiated after initial treatment. The data also suggest that each year a small proportion of grade 1 residual tumors progresses toward a more malignant histologic type.

CONCLUSIONS

Our results are not consistent with the hypothesis that a greater tumor aggressiveness in patients with LR could explain the excess of metastases. This conclusion is supported by the analysis of the delays between metastases' emergence, and death, which shows that tumors with or without LR have similar biological characteristics.

Studies with bromodeoxyuridine in head and neck cancer and accelerated radiotherapy

Using bromodeoxyuridine (BrdUrd), tumour cell proliferation was assessed, by flow cytometric (FCM) and immunohistochemical methods, in patients treated by the CHART regime of radiotherapy. Of 115 cases studied, data were complete in 90 using both methods. No cell kinetic-related parameter predicted the outcome of patients treated by CHART, in keeping with the view that, with this regime, cellular proliferation had been minimised as a cause of failure. Histological evaluation of the labelling index (LI) revealed a trend for higher LI is in diploid tumours (16.2%) than in aneuploid (13.8%), contrasting to that found by FCM (5.0 and 9.3% respectively). When the Tpot was calculated using a combination of histology LI and FCM TS, diploid tumours showed more rapid proliferation (Tpot 1.8 days) than aneuploid tumours (Tpot 3.2 days); this finding was significant (p < 0.02). A novel parameter, termed proliferation pattern, unique to these studies with BrdUrd in vivo, was assessed. Both proliferation pattern and histological grading had predictive power to discriminate the outcome in univariate analysis (p = < 0.031 and 0.037, respectively). In a Cox multivariate analysis, proliferation pattern was the more important predictor. The studies reported highlight the extra information that can be gained from combining immunohistochemistry with flow cytometry to study the cellular proliferation of human tumours.

The importance of locoregional control in the treatment of breast cancer and its impact on survival

BACKGROUND

Different schools of thought regarding the natural history of breast cancer and how it relates to the importance of local control in affecting survival have generated controversy over the optimal treatment of early breast cancer. Parting with traditional thinking that some disease is localized, in which cases local control is important for survival, another view of the natural history of the disease argues that local control is not of value to survival. This commentary will review the evidence and attempt to evaluate the effect of modern adequate local treatment on survival.

METHODS

A review of the pertinent literature on the treatment of breast cancer and an analysis of recent clinical trials and meta-analysis are presented.

RESULTS

Evaluation of the recent literature and meta-analysis demonstrates that adequate local regional treatment, especially radiation therapy in the treatment of breast cancer, does effect survival significantly.

CONCLUSIONS

Results of modern effective local treatment of breast cancer substantiate the claim that some breast cancer is localized. Data show that tumor size, lymph node involvement, tumor grade, and other prognostic factors are important predictors of whether a tumor is localized and therefore amenable to local treatment. Smaller tumors generally are most likely to be localized. Recent studies on modern irradiation techniques show that adequate effective irradiation of localized disease, including appropriate treatment of all nodal areas when needed and limited radiation to sensitive organs, can significantly improve survival and, in high-risk patients, enhance the effect of systemic treatment in improving survival.

Differential values of Ki-67 index and mitotic index of proliferating cell population. An assessment of cell cycle and prognosis in radiation therapy for cervical cancer

BACKGROUND

Little is known about correlations between the growth fraction determined immunohistochemically with Ki-67 antibody and radiation response or prognosis after radiation therapy.

METHODS

The prognostic value of the growth fraction determined by Ki-67 index and the mitotic index of proliferating cell population (pMI) were assessed in 45 cervical cancers treated with radiation therapy. The specimens from the cervix before radiation therapy were immunohistochemically stained with anti-Ki-67 antibody.

RESULTS

The mean Ki-67 index and pMI for all patients were 36.0% and 2.74%, respectively. The patients with a Ki-67 index of 33% or greater showed significantly better histologic response to radiation at 30 Gy than those with less than 33%. The mean Ki-67 index for patients with good prognosis was significantly higher than for patients with tumor recurrence or metastasis later. Further, the mean values of pMI for patients with good prognosis were significantly lower than for patients with recurrence or metastasis. The 3-year survival rate for higher Ki-67 index (> or = 33%) was significantly better than lower Ki-67 index (less than 33%) (90.9% versus 34.8%; P < 0.001). However, the 3-year survival rate for higher pMI (> or = 3.5%) was significantly poorer than lower pMI (less than 3.5%) (8.3% versus 81.8%; P < 0.001).

CONCLUSIONS

These results suggested that tumors with a high growth fraction showed a good prognosis with radiation therapy. In addition, the inverse prognostic correlation between the Ki-67 index and pMI suggested that both indices have independent values on radiation response and prognosis after radiation therapy.

Monitoring of radiotherapy-induced morphonuclear modifications in the MXT mouse mammary carcinoma by means of digital cell image analysis

The present work deals with the characterization of the morphological changes induced by ionizing radiation on MXT mouse mammary cancer cell nuclei. The monitoring of the radiotherapy-induced morphonuclear modifications was carried out by means of digital cell image analysis, which made it possible to compute morphometric (nuclear area), densitometric (nuclear DNA content) and textural (chromatin pattern characteristics) parameters assessed on Feulgen-stained nuclei. The biological material was obtained from serial fine needle-aspirations performed on control tumors and 2Gy and 8Gy irradiated tumors. Digital cell image analyses were assessed at the 7th, 18th, and 28th days-post irradiation. We showed that radiotherapy induced specific morphonuclear modifications that appeared in a dose-dependent and time-dependent manner. The 2Gy and 8Gy radiotherapy doses led to an increase in the mean nuclear area value, this feature being observed at both the 1st and the 4th week post-irradiation. The resultant effect on the chromatin pattern characteristics corresponded to a decrease in overall condensation level as compared to the control cell nuclei. Finally, the mean nuclear DNA content increased at the 1st week post-irradiation, but decreased at the 4th week post-irradiation as compared to the MXT control tumor. Computerized cell image analysis, therefore, appears to be a useful tool in helping to monitor the radiotherapy-induced effects that occur in neoplastic cell nuclei and which can be observed by means of optical microscopy.

The effect of two fractions of radiation, delivered in air or in hyperbaric oxygen, on the Fib/T tumour in WHT mice pretreated with a hypoxic gas mixture

The response of the Fib/T tumour to equal fractions of radiation, spaced by an interval of 24 hours, was determined in tumour-bearing mice that were pretreated either with 8% oxygen for 48 h or with air. An increase in tumour cell kill occurred in the group of animals that received a low oxygen pretreatment. Tumour cell kill was further and significantly increased if mice were retained in the low oxygen environment for the 24-h interval between radiation fractions. Possible explanations for these findings are proposed and discussed. The effect of a 48 h 8% oxygen exposure in modifying the response of the Fib/T tumour to two fractions of radiation, both delivered in hyperbaric oxygen, was also investigated. The low oxygen pretreatment did not significantly alter the tumour response to radiation given under conditions of hyperbaric oxygenation.

A meta-analysis of reported correlations between prognostic factors in breast cancer: does axillary lymph node metastasis represent biology or chronology?

A statistical overview of published results on correlations between various prognostic factors in breast cancer was undertaken. A distinction was made between clinical (or anatomical) prognostic factors--namely, axillary lymph node status and tumour size--and eight different biological prognostic factors. The latter included: tumour grade, oestrogen and progesterone receptor status, thymidine labelling index, DNA ploidy, S-phase fraction, epidermal growth factor receptor expression and c-erbB-2 gene amplification (or overexpression). 139 articles were eligible for review which reported a total of 432 individual correlations. A simple form of meta-analysis was employed: the counting method, in which the number of studies achieving a statistically significant correlation or not were counted. For each possible correlation examined, the proportion of studies showing a statistically significant correlation was calculated and an exact binomial 99% confidence interval determined for that proportion. If the 99% confidence interval included 5% (the proportion of correlations that would be expected to be statistically significant if the null hypothesis was true), it was taken as failing to exclude the null hypothesis of a zero correlation, while if it excluded 5% it was taken as rejecting the null hypothesis of a zero correlation. A broad agreement was found among published reports on the existence of a statistically significant correlation between the various biological prognostic factors in breast cancer. Of the 20 correlations examined, 18 had a 99% confidence interval excluding 5%, thus rejecting the null hypothesis of a zero correlation. On the other hand, a completely different result was obtained when reports on possible correlations between lymph node status and tumour size on the one hand and the eight biological prognostic factors on the other were analysed. Of the 16 correlations examined, 13 had a 99% confidence interval including 5%, failing to reject the null hypothesis of a zero correlation. These observations suggest the hypothesis that the prognostic influence of node status and tumour size cannot be explained by an analysis of the biology of breast cancer; and is compatible with the contention that axillary node status is merely a reflection of the relative chronological age of breast cancer.

Feasibility and reproducibility of the [3H]-thymidine labelling index in breast cancer. The SICCAB Group for Quality Control of Cell Kinetic Determination

For several malignancies, autoradiographic evaluation of the S phase cell fraction by means of [3H]-thymidine ([3H]dT) has proved a valid prognostic tool which should be included in a 'risk factor profile system' to estimate prognosis in individual patients. However, its clinical implementation requires a methodological standardization, a high feasibility and an assessment of the reproducibility of results, within and between different laboratories. The recent availability of a kit for in vitro incubation with [3H]dT and histological fixation of solid tumour specimens has contributed to the methodological simplification and standardization of the technical procedure, increasing its feasibility in several institutions. For breast cancer, preliminary results from a quality control study promoted by the Italian Society of Basic and Applied Cell Kinetics (SICCAB) showed a high inter-observer reproducibility within (r = 0.96) and between different laboratories (r = 0.93). Moreover, on a series of 20 autoradiographic samples sent to 15 different institutions, only 2% of tumours shifted from one of the cell kinetic subgroups, defined using the median [3H]dT labelling index (LI) of 2.8% as a cutoff, to the other. In addition, a marked consistency of results was observed among the different Italian institutions involved in cell kinetic studies on breast cancers, both in terms of median [3H]dT LI values and basic correlations. Periodic assessment of the reproducibility of [3H]dT LI evaluation among different laboratories is needed, especially for institutions involved in multicentre clinical protocols based on cell kinetic characteristics.

Transition of Ki-67 index of uterine cervical tumors during radiation therapy. Immunohistochemical study

Histopathologic and Ki-67-staining features of cancer cells were investigated in biopsy specimens before and during radiation therapy in 29 patients with cervical squamous cell carcinoma. No morphologic changes were observed up to doses of 540 cGy. A few intact cancer cells remained up to doses of 2700 cGy. Moderate changes in the cancer cells were noticed in patients who received 900 cGy or more, i.e., multinuclei, swollen nuclei and cytoplasms, and prominent large nucleoli. At doses of 1800 cGy or greater, many cancer nests had severely damaged cancer cells with features such as cytolysis, karyolysis, karyorrhexis, pyknosis, and bizarre giant cells. There was no mitosis in the cells of patients who received doses greater than 1800 cGy. The Ki-67-positive cancer cells showed diffuse nuclear-stainings and dot-stainings before radiation therapy. Radiation doses more than 900 cGy changed the staining pattern of the Ki-67 antibody; large irregular spot-stainings and ring-stainings were observed predominantly. The Ki-67 index initially increased with the radiation dose; the mean Ki-67 indices before radiation therapy and at radiation doses of 180 cGy, 540 cGy, and 900 cGy were 41%, 50%, 63%, and 68%, respectively. The indices decreased when the dose was increased further, and they were 39% and 20% at doses of 1800 cGy and 2700 cGy, respectively. Possible explanations, including recruitment of quiescent cells, for the change in Ki-67 staining are discussed.

The scientific bases of cancer management: at the interface between fundamental research and clinical practice

From 1950 to 1985 the 5-year survival rate of cancer patients in industrialized countries, has slowly increased from 25% in 1950 to 50% in 1985. This progress has been due to earlier diagnosis and to a gradual improvement of treatment modalities. Clinical needs have stimulated basic research and clinical investigation. In turn, biological research has introduced new concepts and new agents. Clinical investigation and applied research have brought about an improvement in therapeutic methods and a better understanding of the growth and progression of human cancers which has, in particular, led to the concept of adjuvant treatment of occult metastases. The major recent breakthroughs in fundamental research have reinforced the value of close cooperation between clinicians and fundamentalists. Most of the new biologic tools are specific and only active on tumors cells with well-defined characteristics. Furthermore some new techniques such as adoptive immunotherapy can induce complete tumor regression in some patients and have no detectable effects in other patients with apparently similar tumors. Some cytokines have different effects on experimental and human tumors. The cytokine network is so complex that the administration of one of them can induce unpredictable effects. It has been recognized that experimental tumors and in vitro studies can be misleading and there is no substitute for clinical studies on patients. Moreover clinical experience has documented the amazing ability of tumors to become resistant to all these new agents. Numerous new therapeutic methods are being explored, however with the current state of knowledge it appears that although they can help to control tumors, they still fail to eradicate them. We must therefore learn how to integrate them with conventional therapies. Advances in therapy shall be achieved only by well-designed clinical trials. Thus at the interface between fundamental research and clinical practice there is an urgent need for oncologists with a strong scientific background and laboratory scientists with a deep interest in clinical investigations.

Changes in cell kinetics induced by primary chemotherapy in breast cancer

Changes in the 3H-thymidine labelling index (3H-TdR LI) of primary tumor induced by cytoreductive chemotherapy were evaluated in 26 patients with locally advanced breast cancer subjected to mastectomy after different systemic therapies. A significant reduction of 3H-TdR LI by primary chemotherapy was observed in 11 cases. Changes in cell kinetics were related to the pretreatment proliferative activity: significant increases were observed in 70% of tumors with a very low 3H-TdR LI (less than 25%) and significant decreases in 100% of tumors with a very high 3H-TdR LI (greater than 7.0%). There was no correlation between pretreatment 3H-TdR LI and the objective clinical response, which was conversely related to posttreatment cell kinetics. The 2-year progression rate was lower for patients whose residual tumors after treatment had remained (2/7) or become (1/8) slowly proliferating than for patients whose tumors had remained (5/7) or become (4/4) rapidly proliferating.

The accuracy of computed tomography of the liver in colo-rectal carcinoma

A prospective study in 71 patients with colo-rectal carcinoma was undertaken to evaluate the accuracy of computed tomography (CT) of the liver and arterially enhanced liver CT (CTA). The results were initially based on the findings at surgery. The accuracy of CT was 82% and CTA 84%. Since the evaluation of the liver at surgery is not always correct, a clinical follow-up and repeat CT in the same group of patients was performed. The intention was to search for occult metastatic disease of the liver and thus more accurately evaluate the results of CT, CTA and the surgical evaluation at laparotomy. Both the presence or absence of tumour, as well as the distribution of tumour growth in the liver were considered. In comparison with the results of the follow-up, CT detected the presence and correctly described the tumour distribution in 86%, CTA in 87%, and the surgeon in 88% of the cases, respectively. CTA is recommended if the CT scan is negative or if a more detailed evaluation is required prior to liver resection.

Growth of metastases of the mouse adenocarcinoma EO 771: an allometric relationship between growth of the primary tumors and their metastases

Growth and cell kinetic parameters have been studied of paraaortal lumbar lymph node metastases of the mouse adenocarcinoma EO 771 growing intramuscularly in the thigh. An allometric relationship was found between the growth of the metastasis and that of the primary tumor, i.e. a linear relationship exists between the logarithm of the size of the metastasis and that of the primary tumor which permits the estimation of the growth rate of the metastasis based on the growth curve of the primary tumor. However, growth of metastases differs quantitatively from that of the primary tumor: the specific growth rate (growth rate per unit size) of the metastasis (1) is greater than that of the simultaneously growing primary tumor but (2) is smaller than that of the primary tumor of the same size as the metastasis. The allometric growth relationship further suggests that metastases originate later than is generally predicted presuming exponential growth of metastasis.

Cytokinetic investigation of lung tumors using the anti-bromodeoxyuridine (BUdR) monoclonal antibody method: comparison with DNA flow cytometric data

In order to investigate the cytokinetics of malignant tumors and non-malignant lesions of the lung, tissue samples from 57 patients affected by non-small-cell carcinoma (NSCLC), small-cell carcinoma (SCLC), and benign and inflammatory lesions have been analyzed using the BUdR monoclonal antibody (MAb) method. This method is based on the preparation, at the time of surgery, of viable monocellular suspensions (using collagenase and DNase treatment) and the concomitant administration of BudR. The percentage of BudR-labelled cells was monitored by fluorescent microscopy using an FITC-labelled second antibody. In NSCLC, each histological group showed a wide range of labelling index (LI) values. On the contrary, SCLC exhibited a more homogeneous kinetic behaviour as evidenced by a narrowly distributed, higher LI. Tumors shown to be diploid by flow cytometry did not show a lower LI than aneuploid tumors. Furthermore, differences were constantly observed between the S-phase percent calculated using BUdR and that calculated using the DNA flow cytometric (FC) histogram, the latter always showing higher S-phase values. In an attempt to study the intra-tumor proliferative heterogeneity, multiple-site sampling was performed. Proliferative heterogeneity seemed to be higher inter-tumor than intra-tumor. Finally, a positive correlation (p less than 0.05) was found between LI and the actual doubling time (DT) of the primary tumor mass, evaluated using sequential radiographs. In conclusion, the present BUdR method can be considered a useful source of relevant information on in vivo cell growth, in parallel to other clinical (DT) and biological (DNA content) approaches.

Risk factors for breast recurrence in premenopausal and postmenopausal patients with ductal cancers treated by conservation therapy

Risk factors for local failure were evaluated for 496 clinical Stage I-II patients with infiltrating ductal carcinomas (median follow-up, 71 months) treated by conservative surgery and radiotherapy. Monofactorial analysis identified the following factors to be correlated with increased risk: moderate/marked mononuclear cell reaction (MCR), high histologic grade (G), extensive intraductal component (EIC), tumor necrosis, macroscopic multiplicity, estrogen receptor negativity, anatomic tumor size, age younger than 40 years, and vascular invasion. Only MCR, G, and EIC proved significant in Cox multivariate analysis. These risk factors were highly age dependent, with EIC markedly more prevalent in women younger than 50, MCR and G in women younger than 40. Separate Cox analysis for premenopausal patients showed that MCR/EIC determined risk independent of resection margins: tumors with MCR had a 28%, and with EIC a 22% probability of recurring locally by 5 years. Premenopausal patients with neither risk factor had a very low failure rate (2.6% at 5 years), regardless of age. For postmenopausal patients risk of breast recurrence was determined both by adequacy of resection margins and grade, with a high local failure rate for patients having G3 tumors with positive or indeterminate margins (31% at 5 years). The authors conclude that the microscopic examination is the only useful tool for assessing the risk of local failure, which is quite low for the majority of patients treated with breast conservation. High-risk patients can be recognized morphologically. The age dependence of morphologic risk factors appears to explain the high local failure rate seen in patients younger than 40.

Cell population kinetics of the rhabdomyosarcoma R1H of the rat after single doses of X-rays

The kinetics of depopulation and repopulation of the solid transplantable rhabdomyosarcoma R1H of the rat following local irradiation with single subcurative X-ray doses of 7.5, 15 and 30 Gy was studied. Several parameters were sequentially measured over a time interval of 4 weeks after irradiation: the ratio of the number of tumour to host cells, and the cellular DNA content of tumour and host cells, were determined by flow cytometry; the amount of DNA per gram of tumour tissue was determined biochemically; the clonogenic fraction of tumour cells was obtained from in vitro colony assay; and the tumour volume was assessed by in situ caliper measurements. From the amount of DNA per gram and the average DNA content per cell, the total number of cells per gram of tumour tissue was obtained. From this and the other parameters measured, the number of clonogenic tumour cells, non-clonogenic tumour cells and nucleated host cells per tumour, as well as their variation with time and dose, could be derived. The results showed that there was a lag period prior to depopulation amounting to 3.8 +/- 1.4, 1.4 +/- 0.8 or 0 +/- 0.7 days for 7.5, 15 or 30 Gy, respectively. The rate of depopulation of non-clonogenic tumour cells increased with dose; the halving times of non-clonogens were 4.7 +/- 1.8, 2.6 +/- 0.7 or 2.1 +/- 0.4 days for the three doses applied. There were no indications that proliferation of doomed cells contributed significantly to tumour growth after irradiation. After lag periods that were similar in length to those prior to depopulation, a massive immigration of host cells was observed. Under certain conditions more than 97 per cent of the cells present in irradiated tumours were found to be of host origin. There was a lag period before the onset of repopulation by clonogenic tumour cells, the length of which increased from 2.7 +/- 0.7 to 5.0 +/- 0.8 or 6.3 +/- 1.0 days for 7.5, 15 or 30 Gy, respectively. The initial rate of repopulation increased with radiation dose; after the end of the lag period the doubling time of clonogenic tumour cells (in controls amounting to 3.7 +/- 0.2 days) was 3.1 +/- 0.1, 2.1 +/- 0.1 and 1.1 +/- 0.1 days for the three doses applied.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell proliferation kinetics in human solid tumors: relation to probability of metastatic dissemination and long-term survival

A large number of studies have investigated the relationship between the long-term survival and the percentage of tumor cells in S phase assessed by autoradiography after tritiated thymidine labelling, image cytometry, flow cytometry or labelling with an halogenated analog of thymidine, in various types of human solid tumors. The survey of the results clearly shows that the S-phase fraction (SPF) is of high prognostic significance in several types of cancers, in particular in breast cancers, non-Hodgkin lymphomas, ovarian cancers, neuroblastoma, bladder cancers and lung cancers. SPF was found of high independent significance in 10 of the 11 studies in which multivariate analyses of prognostic factors had been carried out. Proliferation appears generally to be of higher prognostic significance than ploidy. In view of the wide differences in the biological characteristics of the tumors studied, it is likely that the association between a high proliferation rate and the degree of tumor aggressiveness is a general feature of human solid tumors. However, high proliferative rate of tumor cells is probably not the cause of tumor biological aggressiveness but a variable associated with it. The extent to which cells escape from the regulatory systems which control their proliferation appears to be a good index of tumor progression.

Intensive induction chemotherapy for poor risk non-seminomatous germ cell tumours

An increase in initial chemotherapy intensity was evaluated in 29 patients with high risk metastatic non-seminomatous germ cell tumours (NSGCT) of the testis, defined by the presence of multiple large lung metastases, liver, bone or brain metastases, or the combination of large abdominal mass with high serum concentration of the tumour markers alpha-foetoprotein (AFP) or beta subunit of human chorionic gonadotrophin (HCG) (AFP greater than 500 ku/l or HCG greater than 1000 iu/l). Four courses of bleomycin, vincristine and cisplatin (BOP) were given at 7 day intervals, followed by three courses of etoposide, cisplatin with or without bleomycin (BEP or EP) at 21 day intervals for a total of 13 weeks of chemotherapy. Twenty-three (85%) of 27 evaluable patients have remained continuously free from disease progression at a median of 24 months (range 14-38 months) from chemotherapy and the actuarial 2 year freedom from progression rate is 86% (95% CI = 73-99%). Three patients died from non-malignant causes, two of bleomycin pneumonitis and one from complications of cystic fibrosis. Thus cause specific overall survival in the total population of treated patients is 79%. With appropriate limitation of bleomycin dosage, this approach is well tolerated and results compare favourably with less intensive induction schedules based on initial 21-28 day cycles.

Tumor cell proliferation kinetics and tumor growth rate

The present knowledge on the growth rate and the proliferation kinetics of human tumor is based on the measurement of the tumor doubling times (DT) in several hundred patients and on the determination of the proportion of proliferating cells with radioactive thymidine or by flow cytometry in large numbers of patients. The results show that the DT of human tumor varies widely, from less than one week to over one year with a median value of approximately 2 months. The DTs are significantly correlated with the histological type. They depend upon 1) the duration of the cell cycle whose mean duration is 2 days with small variations from tumor to tumor, 2) the proportion of proliferating cells and consequently the cell birth rate which varies widely among tumors and which is significantly correlated to the DT, 3) the cell loss factors which also vary widely and which are the greatest when proliferation is most intensive. These studies have several clinical implications: a) they have further increased our understanding of the natural history of human tumor, b) they have therapeutic implications since tumor responsiveness and curability by radiation and drugs are strongly influenced by the cell kinetic parameters of the tumor, c) the proportion of proliferating cells is of great prognostic value in several types of human cancers. The investigation of the molecular defects, which are correlated with the perturbation of control of cell proliferation, should lead to significant fundamental and therapeutic advances.

Comparison of S-phase fractions measured by flow cytometry and autoradiography in human transplant tumors

The 3H-thymidine labeling index (TLI) and the percentage of cells in the S-phase have been determined by autoradiography and by flow cytometry, (FCM), respectively, in six malignant tumors of human origin transplanted on athymic nude mice. The Dean and Jett model and the graphical model were used to determine the percent of S-phase cells by FCM. Cell cycle analysis was performed using 1) no correction for background; 2) an algebraic function for background correction; and 3) an exponential function for background subtraction. Each of these three data sets was evaluated using both the Dean and Jett model and a graphical model for the evaluation of DNA histograms. The S-phase fractions (SPF) were compared to the corresponding labeling index results. SPF without background correction were 1.54 times higher than the TLI. SPF, after correction using the algebraic model, were 1.29-fold higher than the TLI, whereas SPF obtained after background subtraction according to the exponential model were only 1.05-fold higher than the TLI. Student's t-test revealed significant differences between the mean TLI values (16.25 +/- 9.06) and the mean SPF obtained by FCM without background correction (mean 25.0 +/- 9.36, P less than 0.01), but not between the mean TLI values and the mean SPF percentages after algebraic (mean 21.0 +/- 10.29) and exponential background correction (mean 17.11 +/- 11.59), P greater than 0.05 each. There was no difference between the results obtained using the Dean and Jett model and those obtained using the graphic evaluation.(ABSTRACT TRUNCATED AT 250 WORDS)

Mammographic screening and mortality from breast cancer: the Malmö mammographic screening trial

STUDY OBJECTIVE

To determine whether mortality from breast cancer could be reduced by repeated mammographic screening.

DESIGN

Birth year cohorts of city population separately randomised into study and control groups.

SETTING

Screening clinic outside main hospital.

PATIENTS

Women aged over 45; 21,088 invited for screening and 21,195 in control group.

INTERVENTIONS

Women in the study group were invited to attend for mammographic screening at intervals of 18-24 months. Five rounds of screening were completed. Breast cancer was treated according to stage at diagnosis.

END POINT

Mortality from breast cancer.

MEASUREMENTS AND MAIN RESULTS

All women were followed up and classed at end point as alive without breast cancer, alive with breast cancer, dead from breast cancer, or dead from other causes. Cause of death was taken from national mortality registry and for patients with breast cancer was validated independently. Mean follow up was 8.8 years. Altogether 588 cases of breast cancer were diagnosed in the study group and 447 in the control group; 99 v 94 women died of all causes and 63 v 66 women died of breast cancer (no significant difference; relative risk 0.96 (95% confidence interval 0.68 to 1.35)). In the study group 29% more women aged less than 55 died of breast cancer (28 v 22; relative risk 1.29 (0.74 to 2.25)). More women in the study group died from breast cancer in the first seven years; after that the trend reversed, especially in women aged greater than or equal to 55 at entry. Overall, women in the study group aged greater than or equal to 55 had a 20% reduction in mortality from breast cancer (35 v 44; relative risk 0.79 (0.51 to 1.24)). OTHER FINDINGS: In the study group 100 (17%) cancers appeared in intervals between screenings and 107 (18%) in non-attenders; 51 of these women died from breast cancer. Cancers classed as stages II-IV comprised 33% (190/579) of cancers in the study group and 52% (231/443) in the control group.

CONCLUSIONS

Invitation to mammographic screening may lead to reduced mortality from breast cancer, at least in women aged 55 or over.

Growth fractions in human prostatic carcinoma determined by Ki-67 immunostaining

Until recently, [3H]-thymidine incorporation, DNA analysis by flow cytometry, and cell doubling times have been the main methods of studying tumour cell kinetics. All these techniques are laborious, expensive, and difficult to perform in a routine diagnostic laboratory. This study examined fresh frozen sections from 31 prostatic biopsy specimens with the hybridoma antibody Ki-67, a marker of proliferating cells, using a modified avidin-biotin-peroxidase complex technique. The percentage of glandular cells decorated by this antibody, representing the growth fraction, was determined for both benign and malignant samples. Benign prostatic glands showed an average Ki-67 score of 4 per cent, significantly less than the 16.3 per cent mean growth fraction found in prostatic carcinomas. There was a significant correlation between the tumour growth fraction as assessed by Ki-67 staining, and the histological grade. A positive correlation was also found between the Ki-67 score and the intensity of staining, and a definite trend was noted between the Ki-67 score and the tumour clinical stage. Ki-67 promises to be a useful marker in determining the prognosis of prostatic cancer.

Repopulation in human tumors. A biological background for fractionation in radiotherapy

Tumor repopulation plays a major role in the response of tumors to radiotherapy or chemotherapy but its degree varies widely among human tumors. Its mechanism has not been elucidated, however it is unlikely that repopulation can be simply explained by the greater availability of oxygen and nutrients resulting from the reduction in tumor mass. In normal tissues, such as bone marrow, treated cells release stimulating factors which are able to recruit quiescent cells into proliferation. Similar mechanisms have been observed in experimental tumors and their existence is probable in human tumors. A low pretreatment proliferation index and low cell density indicate that the control mechanisms which regulate cell proliferation in normal tissues are still partially operating in these tumors. In such tumors an increase in the level of cell proliferation during or after treatment has often, but not always, been observed. There is not yet a clear guide for predicting tumor proliferation rate under treatment and further investigations are needed.

Split-course versus continuous radiotherapy. Analysis of a randomized trial from 1964 to 1967

A randomized clinical trial was performed from 1964 to 1967 to compare the therapeutic results of split-course external beam radiotherapy with those of continuously fractionated treatment. Altogether 439 consecutive patients with carcinoma of larynx, nasopharynx, hypopharynx, oropharynx, oral cavity, oesophagus and urinary bladder were included in the series. 227 patients received split-course treatment and 212 were treated by the continuous-course method. In the split-course treatment there was a 2-3 weeks' interruption after 25-30 Gy. This break was compensated by a 10% increase in the total dose. For each tumour site local control and failure rates for the 2 treatment techniques were similar. No significant differences in 5- and 10-year survival were noted. Acute side effects were milder in all patients treated with split-course. The occurrence of late reactions was similar in both treatment groups. However, severe late reactions in the urinary bladder were somewhat more frequent in patients treated with split-course technique; the difference was not statistically significant. We conclude that there were no significant differences in local control, long-term survival and late normal tissue reactions between the treatment groups. The acute normal tissue reactions were milder in the split-course treated groups. We still regard split-course as a useful treatment modality provided the interruption is compensated with about 10% increase in total dose. However, more studies are needed to show which tumours proliferate during prolonged radiotherapy.

Flow cytometric DNA measurements in paraffin-embedded bladder carcinoma tissue before and after precystectomy radiotherapy

From 1976 through 1983, 48 patients with T2/T3 bladder carcinomas were treated with pre-operative radiotherapy (46 Gy) and total cystectomy. DNA histograms were recorded by flow cytometry (FCM) from all pre-treatment paraffin-embedded tumour biopsies and, if still present after radiotherapy, from tumour tissue from the cystectomy specimen. Five patients were excluded from the study because no DNA histograms could be recorded due to extensive destruction of the cell nuclei during preparation. Thus, 43 patients are completely evaluable. Before the start of radiotherapy, 32 bladder carcinomas were interpreted as non-diploid, whereas 11 were diploid. Non-diploidy of the pre-treatment biopsy was associated with radiotherapy-induced stage reduction (p = 0.13). The survival rates in patients with diploid and non-diploid tumours were 65% and 45% respectively at 4 years (p = 0.13). Although not statistically significant, our results suggest that DNA-FCM may provide clinically relevant information about the tumour biology and response to radiotherapy concerning bladder carcinomas.

Growth rate analysis of lung metastases from histologically benign giant cell tumor of bone

A growth rate analysis of lung metastases of benign giant cell tumor (GCT) of bone, histologically indistinguishable from the primary benign tumor, is presented. The doubling time (DT) was 186 days in the first 13 months of growth, and 465 days in the last 4 months. These DTs are much longer than DT of lung metastases of any other tumors, and have a good correlation with a long survival time. Backward extrapolation showed that the lung metastases began to develop years before the primary tumor was diagnosed and treated. If this can be confirmed in a larger number of patients, it could be concluded that there will be no indication for amputation as a treatment for benign GCT whether or not lung metastases are present. The growth rate analysis supports the concept that these metastases might represent a benign process, and as such are a unique histologic and clinical phenomenon.

Klaas Breur Medal lecture 1985. The growth and progression of human tumors: implications for management strategy

The natural history of human cancers can be stimulated assuming an exponential growth pattern. This simple model shows that the duration of the tumor growth during the occult phase is always much shorter than the interval between the carcinogenic stimulus and the clinical emergence of the tumor; this is consistent with the existence of several stages of precancerous lesions which precede the development of the neoplastic clone. Metastatic spread can be simulated and a model of tumor growth can be used to predict the proportion of patients in whom metastatic dissemination can be avoided by an earlier diagnosis. The model predicts also that in the subsets of patients in whom metastatic spread occurs early the occult metastases will be large at the time of the treatment of the primary tumor and therefore adjuvant chemotherapy (CT) will be less effective; this is in keeping with clinical data. The model can also help to understand the relationship between the local control of a tumor and the cure of the patient, and to explain the discrepancy between the great reduction in the local incidence of local recurrence obtained with post-operative radiotherapy and its relatively small impact on survival. However, this simple model is insufficient to explain several features of the course of a human cancer, in particular the heterogeneity of the neoplastic cell population and the inexorable tendency for some cancers to progress towards a more malignant type and to become progressively more resistant to any treatment. Genetic instability appears to be an essential characteristic of human cancers and variations in its degree may be the cause of differences in the aggressiveness and in the severity of the various types of cancers. The recent advances in the molecular biology of cancers has already given to clinicians new and powerful prognostic indicators. These will probably, in the near future help, towards a better understanding of the biology of tumor growth and tumor progression.

Lymphokine-induced monocyte procoagulant activity is depressed in patients with advanced malignancies

Fibrin deposition in the microenvironment of tumor cells may be critical to tumor growth and metastasis formation. Procoagulant activities of tumor cells themselves, or of infiltrating macrophages, activated by the host's immune system to the tumor, may both contribute to coagulopathies associated with metastases. Lymphokine (LK) supernatant activated procoagulant activity on normal peripheral blood monocytes but failed to induce activity on mononuclear cells from 18/22 patients with locally advanced or disseminated non-lymphoid tumors. Monocytes from the remaining patients had very low basal levels of MPCA and were less sensitive than normal cells to LK. Monocytes from 4 patients (3 with tumors with a high growth fraction) had extremely elevated levels of basal procoagulant activity, possibly due to maximal activation in vivo. Neither LK nor bacterial lipopolysaccharide (LPS) stimulated procoagulant production of these cells. By contrast, cells from 8/13 patients produced procoagulant in response to LPS. This study indicated that monocyte function of patients with disseminated cancer is suppressed with respect to LK stimulation, but that cells with normal basal levels of MPCA respond to LPS. Preactivation of mononuclear procoagulant in vivo precluded subsequent stimulation by either LPS or LK.

Potential for increasing the differential response between tumors and normal tissues: can proliferation rate be used?

Rapid proliferation of malignant cells has not previously been emphasized as a major source of failure to control tumors. Evidence is presented that the effective doubling times of clonogenic cells in human tumors during multifraction radiotherapy are in the range of a few days, that is, similar to the pre-treatment Potential Doubling Times and much shorter than Volume Doubling Times. Evidence from animal tumor studies leads to the same conclusion. Accelerated fractionation should be considered for individual human tumors whose LI is measured (e.g., by flow cytometry and the BUdR antibody) and found to be too high.

Resistance to cancer chemotherapy

Human cancers are either refractory to chemotherapy, or acquire resistance to it. Although acquired resistance to chemotherapy is generally ascribed to the drug itself, it may be linked with the nature of neoplasia, since normal tissues e.g. gastrointestinal mucosa or bone marrow, do not seem to acquire resistance and their perpetuating sensitivity even undermines effective treatment. According to the theory presented herewith, chemotherapy ultimately fails since it is based on wrong premises. Cancer is regarded here as a metabolic deficiency, originating in stem cell destruction. Besides serving as tissue progenitors, stem cells are postulated to secrete a vital substance 'A' necessary for proper tissue function. Carcinogens interfere with 'A' production mainly by destroying stem cells, which the organism is incapable of fully replenishing, so that less 'A' is produced. This irreversible 'A' deficiency may be replenished solely by a substitute, or substance 'B', produced by a specialized organ, the neoplasm. Since carcinogens continue depleting additional stem cells, the deficiency worsens. In order to keep up with increasing demand the neoplasm has to proliferate more and more until it reaches a stage of decompensation when the harm inflicted by it outweighs its benefit. Stem cell depletion is regarded here as the common final pathway of carcinogens. The theory predicts that following a supply of 'A' producing stem cells or inactivated 'B' producing neoplastic stem cells, the tumor will regress. Tumor regression is achievable also by diminishing the demand for the missing metabolites, which may be accomplished by chemotherapy. 'A' and 'B' are consumed mainly by transitional cells. Upon their elimination the demand for 'A' declines and the tumor may wane. This is regarded here as the main role of chemotherapy in cancer, while its tumoricidal potency is indicated solely for repairing tumor induced function loss. It is proposed here that the good response to chemotherapy by Hodgkin's disease and seminoma is linked with their being partially infective. Both start as genuine smouldering infections turning later into neoplasms. While chemotherapy is adequate only during the infective phase, it is met with mounting resistance when applied during the neoplastic phase.

Solid tumor models for the assessment of different treatment modalities: XXIII. A new approach to the more effective utilization of radiotherapy alternated with chemotherapy

This study with the rat hepatoma 3924A demonstrated the marked improvement in tumor cure rates and control of tumor growth that can be achieved by the addition of cyclophosphamide (CP) to multiple fractions of radiation per day (MFD) schedules given intermittently. MFD radiation was delivered over a 2-day period followed by CP (150 mg/kg or 0.9 g/m2) 1 day later; this combined course was repeated at 11-day intervals (to allow for gastrointestinal tract and bone marrow recovery) for a total of 3 courses over a 23-day period. Cure rates of 30, 50 and 60% were achieved with total radiation doses of 4500, 6000 and 7500 rad, respectively, when the MFD radiation was given with CP. No cures and no complete responses were realized when the same intermittent MFD schedules for radiation were employed up to 9000 rad without CP. Other groups of 10 animals each were treated with daily fractions of 100, 150, 188, 250 and 375 rad given on days 0-9, 11-20 and 22-31. A 150 mg/kg or 0.9 g/m2 dose of CP was given after each course of daily radiation on days 10, 21 and 32 in the combined treatment groups. No complete responses or tumor cures occurred with radiation alone given daily for total radiation doses, which were increased from 3000 to 11,250 rad. Only the highest radiation dose given, 375 rad per day to a total of 11,250 rad, resulted in a complete response rate and tumor cure rate of 50% when CP was added. The addition of CP to the daily fractionation schedules reduced the total dose needed to give a growth delay of 100 days by 39% (5600 rad versus 9200 rad). The addition of CP to the intermittent MFD schedules further reduced the total dose needed to give a growth delay of 100 days to 4200 rad. Major improvements in some types of cancer treatment may be realized if we can develop clinical protocols for the alternate use of chemotherapy and radiotherapy as we have done successfully in our experimental program. The finding that intermittent MFD radiation schedules are as effective as daily schedules when given alone suggests that greater flexibility of patient management in clinical radiotherapy may be possible without a major loss of therapeutic effectiveness. These alternated fractionated schedules offer the possibility of optimizing treatment in terms of patient convenience and economy as well as the potential for improving the effectiveness of the interaction of radiotherapy with radiosensitizers, radioprotectors, and hyperthermia in addition to chemotherapy.

A simulation model of the natural history of human breast cancer

In order to assess the time at which the distant metastases were initiated, a model has been developed to simulate the natural history of human breast cancer. The metastasis appearance curves were fitted to those observed for tumours of various sizes among the 2648 patients treated at the Institut Gustave Roussy from 1954 to 1972. The model assumes that metastases are initiated when the tumour reaches a threshold volume (distribution of this volume was estimated in a previous article). Two patterns of growth were considered: exponential and Gompertzian. Distributions of tumour and metastases doubling times are fixed according to the literature. A relationship between tumour and metastasis doubling time is estimated. Simulations were used to optimize metastases growth duration as a function of the metastasis doubling time. The ages of the metastases at tumour diagnosis are calculated. With exponential growth, it was necessary to introduce correlations to obtain a satisfactory fit of the metastases appearance curves: between the tumour volume at diagnosis and the doubling time (R1 = -0.3), and between the tumour volume at metastasis initiation and the doubling time (R2 = 0.3). The growth duration of the metastases before their detection was found to equal about 18 metastases doubling times at detection and the mean ratio between the doubling time of a tumour and its metastases equal to 2.2. With Gompertzian growth, it was impossible to adjust satisfactorily the proportions of metastases at diagnosis as a function of the primary tumour volume. However, when we ignore this, the best fit was obtained when the duration of metastases growth before detection was about the same as for exponential growth. With either growth pattern, the model predicts that the proportion of patients with metastases would be reduced by approximately 30% if the primary tumours were treated 12 months earlier. This prediction is consistent with the results of the screening programs for breast cancer.

The estimation of host-resistance in cancer

From the third year after its clinical diagnosis and onward the cancer hazard rate continuously declines. This phenomenon is common to all cancers irrespective of stage, and far less pronounced in other chronic diseases. It is so typical of cancer as to be regarded as a "law of the improving chances of the cancer patient". Although the cancer hazard rate itself is higher than in most other chronic diseases, it always declines while in other chronic diseases it rises. Two kinds of processes operate in cancer: a noxa and host resistance. Throughout cancer progression the organism maintains a delicate equilibrium with the noxa, only its reserves are continuously depleted and when exhausted the noxa overpowers the host's resistance and the patient dies. The hazard rate is inversely proportional to the patient's reserve. Its decline indicates that the host resists the noxa better and better, since however his reserves are limited, he ultimatelly succumbs to it. This phenomenon also shapes cancer age specific incidence and mortality rates. From the age of 15 years and onward the curves ascend in an exponential fashion, gradually tapering off, which is viewed here as a token of a mounting resistance of the organism to the carcinogenic noxa. Host resistance operates also during tumor growth, accounting for the Gompertzian shape of its growth curve. The growth rate of most human tumors progressively decreases and is therefore best described by the Gompertz function which initially rises in an exponential fashion and gradually tapers off. Tumor size and growth rate indirectly reflect the host's condition or reserve. The two tumor attributes are related to the hazard rate in the following manner: Tumor size is proportional to the hazard rate, indicating host reserve. Tumor growth rate is proportional to the hazard rate change, indicating host resistance. Both indicators may be estimated independently and applied to the assessment of the host's reserve and resistance during cancer progression.