RATES OF GROWTH OF PULMONARY METASTASES AND HOST SURVIVAL

Bayesian versus Empirical Calibration of Microsimulation Models: A Comparative Analysis

Calibration of a microsimulation model (MSM) is a challenging but crucial step for the development of a valid model. Numerous calibration methods for MSMs have been suggested in the literature, most of which are usually adjusted to the specific needs of the model and based on subjective criteria for the selection of optimal parameter values. This article compares 2 general approaches for calibrating MSMs used in medical decision making, a Bayesian and an empirical approach. We use as a tool the MIcrosimulation Lung Cancer (MILC) model, a streamlined, continuous-time, dynamic MSM that describes the natural history of lung cancer and predicts individual trajectories accounting for age, sex, and smoking habits. We apply both methods to calibrate MILC to observed lung cancer incidence rates from the Surveillance, Epidemiology and End Results (SEER) database. We compare the results from the 2 methods in terms of the resulting parameter distributions, model predictions, and efficiency. Although the empirical method proves more practical, producing similar results with smaller computational effort, the Bayesian method resulted in a calibrated model that produced more accurate outputs for rare events and is based on a well-defined theoretical framework for the evaluation and interpretation of the calibration outcomes. A combination of the 2 approaches is an alternative worth considering for calibrating complex predictive models, such as microsimulation models.

The epidemiology and biology of pulmonary metastases

Our goal in this chapter is to explore the complex processes of metastasis and why there is a predisposition for this to occur in the lung. In addition, we aim to describe the incidence of pulmonary metastases in various contexts and based on the origin of the primary tumor. There are unique characteristics of the pulmonary system that make metastases more likely to occur in the lung than anywhere else in the body. Some of these characteristics include receiving the entire cardiac output every minute, having the densest capillary bed in the body, and being the first reservoir of most lymphatic drainage entering the venous system. There are multiple postulated routes of metastasis to the pulmonary system including hematogenous and lymphatic routes with early or late dissemination. The vascularization of pulmonary metastases is variable and complex, often recruiting supply from bronchial and pulmonary origin. There are also many biochemical factors in the tumor microenvironment that play a key role in the development of lung metastases including vascular endothelial growth factor (VEGF), interleukin-8 (IL-8), very late antigen 4 (VLA-4) and intercellular adhesion molecule 1 (ICAM-1). Studies vary widely in reported rates of pulmonary metastases due to differences in clinical study design, however, it is commonly accepted that up to half of autopsies performed on patients who died of malignancy have pulmonary metastases. In a surgical series describing the incidence of primary cancer types with resected pulmonary metastases the most common sites were thyroid, colon, breast, genitourinary tract, skin, liver, breast, and adrenal glands.

Metastasis Initiation Precedes Detection of Primary Cancer-Analysis of Metastasis Growth in vivo in a Colorectal Cancer Test Case

Most cases of deaths from colorectal cancer (CRC) result from metastases, which are often still undetectable at disease detection time. Even so, in many cases, shedding is assumed to have taken place before that time. The dynamics of metastasis formation and growth are not well-established. This work aims to explore CRC lung metastasis growth rate and dynamics. We analyzed a test case of a metastatic CRC patient with four lung metastases, with data of four serial computed tomography (CT) scans measuring metastasis sizes while untreated. We fitted three mathematical growth models—exponential, logistic, and Gompertzian—to the CT measurements. For each metastasis, a best-fitted model was determined, tumor doubling time (TDT) was assessed, and metastasis inception time was extrapolated. Three of the metastases showed exponential growth, while the fourth showed logistic restraint of the growth. TDT was around 93 days. Predicted metastasis inception time was at least 4–5 years before the primary tumor diagnosis date, though they did not reach detectable sizes until at least 1 year after primary tumor resection. Our results support the exponential growth approximation for most of the metastases, at least for the clinically observed time period. Our analysis shows that metastases can be initiated before the primary tumor is detectable and implies that surgeries accelerate metastasis growth.

Cancer progression and the invisible phase of metastatic colonization

Metastatic dissemination occurs very early in the malignant progression of a cancer but the clinical manifestation of metastases often takes years. In recent decades, 5-year survival of patients with many solid cancers has increased due to earlier detection, local disease control and adjuvant therapies. As a consequence, we are confronted with an increase in late relapses as more antiproliferative cancer therapies prolong disease courses, raising questions about how cancer cells survive, evolve or stop growing and finally expand during periods of clinical latency. I argue here that the understanding of early metastasis formation, particularly of the currently invisible phase of metastatic colonization, will be essential for the next stage in adjuvant therapy development that reliably prevents metachronous metastasis.

Estimated Effect of COVID-19 Lockdown on Skin Tumor Size and Survival: An Exponential Growth Model

Background and objectives

Spain is in a situation of indefinite lockdown due to the ongoing coronavirus disease 2019 (COVID-19) pandemic. One of the consequences of this lockdown is delays in medical and surgical procedures for common diseases. The aim of this study was to model the impact on survival of tumor growth caused by such delays in patients with squamous cell carcinoma (SCC) and melanoma.

Material and methods

Multicenter, retrospective, observational cohort study. We constructed an exponential growth model for both SCC and melanoma to estimate tumor growth between patient-reported onset and surgical excision at different time points.

Results

Data from 200 patients with SCC of the head and neck and 1000 patients with cutaneous melanoma were included. An exponential growth curve was calculated for each tumor type and we estimated tumor size after 1, 2, and 3 months of potential surgical delay. The proportion of patients with T3 SCC (diameter > 4 cm or thickness > 6 mm) increased from 41.5% (83 patients) in the initial study group to an estimated 58.5%, 70.5%, and 72% after 1, 2, and 3 months of delay. Disease-specific survival at 2, 5, and 10 years in patients whose surgery was delayed by 3 months decreased by 6.2%, 8.2%, and 5.2%, respectively. The proportion of patients with ultrathick melanoma (> 6 mm) increased from 6.9% in the initial study group to 21.9%, 30.2%, and 30.2% at 1, 2, and 3 months. Five- and 10-year disease-specific survival both decreased by 14.4% in patients treated after a potential delay of 3 months.

Conclusions

In the absence of adequate diagnosis and treatment of SCC and melanoma in the current lockdown situation in Spain, we can expect to see to a considerable increase in large and thick SCCs and melanomas. Efforts must be taken to encourage self-examination and facilitate access to dermatologists in order to prevent further delays.

A Mathematical Model to Predict Diagnostic Periods for Secondary Distant Metastases in Patients with ER/PR/HER2/Ki-67 Subtypes of Breast Cancer

Previously, a consolidated mathematical model of primary tumor (PT) growth and secondary distant metastasis (sdMTS) growth in breast cancer (BC) (CoMPaS) was presented. The aim was to detect the diagnostic periods for visible sdMTS via CoMPaS in patients with different subtypes ER/PR/HER2/Ki-67 (Estrogen Receptor/Progesterone Receptor/Human Epidermal growth factor Receptor 2/Ki-67 marker) of breast cancer. CoMPaS is based on an exponential growth model and complementing formulas, and the model corresponds to the tumor-node-metastasis (TNM) staging system and BC subtypes (ER/PR/HER2/Ki-67). The CoMPaS model reflects (1) the subtypes of BC, such as ER/PR/HER2/Ki-67, and (2) the growth processes of the PT and sdMTSs in BC patients without or with lymph node metastases (MTSs) in accordance with the eighth edition American Joint Committee on Cancer prognostic staging system for breast cancer. CoMPaS correctly describes the growth of the PT in the ER/PR/HER2/Ki-67 subtypes of BC patients and helps to calculate the different diagnostic periods, depending on the tumor volume doubling time of sdMTS, when sdMTSs might appear. CoMPaS and the corresponding software tool can help (1) to start the early treatment of small sdMTSs in BC patients with different tumor subtypes (ER/PR/HER2/Ki-67), and (2) to consider the patient almost healthy if sdMTSs do not appear during the different diagnostic periods.

[Estimated Effect of COVID-19 Lockdown on Skin Tumor Size and Survival: An Exponential Growth Model]

Antecedentes y objetivos

La pandemia del coronavirus SARS-CoV-2 ha provocado un confinamiento indefinido. Una posible consecuencia de esta situación es un retraso en los procedimientos asistenciales de las enfermedades oncológicas. El objetivo de este estudio es estimar el hipotético impacto en la supervivencia que tendría el aumento del tamaño tanto para los carcinomas de células escamosas (CCE) como de los melanomas.

Material y método

Estudio observacional retrospectivo de cohorte multicéntrico. Se desarrolló un modelo de crecimiento exponencial para cada tumor basado en el tiempo de evolución que refiere el paciente.

Resultados

Se incluyeron un total de 200 pacientes con CCE localizados en la cabeza y el cuello y 1.000 pacientes con melanoma cutáneo. Se calculó una curva de crecimiento exponencial para cada tumor y se estimó el tamaño del tumor tras 1, 2 y 3 meses tras el diagnóstico. En la muestra, los CCE mayores de 4 cm o > 6 mm de grosor (definidos como T3) pasaron de 83 (41,5%) en el grupo de estudio real a una estimación del 58,5, 70,5 y 72% tras 1, 2 y 3 meses de retraso quirúrgico estimado, respectivamente. Se estimó una disminución de la supervivencia específica de enfermedad (SEE) de un 6,2, 8,2 y 5,2% a los 2, 5 y 10 años, respectivamente, tras 3 meses de retraso. Para los melanomas ultragruesos (> 6 mm de Breslow) pasaron del 6,9% en el grupo de estudio al 21,9, 30,2 y 30,2% tras 1, 2 y 3 meses de demora. La SEE a los 5 y 10 años del grupo de estudio descendió un 14,4% en ambos tiempos.

Conclusiones

En ausencia de un adecuado diagnóstico y tratamiento de los pacientes con CCE y melanoma en la actual situación de confinamiento en España, podemos llegar a asistir a un considerable aumento de los casos de CCE y melanomas gruesos y de gran tamaño. Se deben fomentar los esfuerzos para promocionar la autoexploración y facilitar el acceso a los dermatólogos para no aumentar la demora de estos pacientes.

Cancer recurrence times from a branching process model

As cancer advances, cells often spread from the primary tumor to other parts of the body and form metastases. This is the main cause of cancer related mortality. Here we investigate a conceptually simple model of metastasis formation where metastatic lesions are initiated at a rate which depends on the size of the primary tumor. The evolution of each metastasis is described as an independent branching process. We assume that the primary tumor is resected at a given size and study the earliest time at which any metastasis reaches a minimal detectable size. The parameters of our model are estimated independently for breast, colorectal, headneck, lung and prostate cancers. We use these estimates to compare predictions from our model with values reported in clinical literature. For some cancer types, we find a remarkably wide range of resection sizes such that metastases are very likely to be present, but none of them are detectable. Our model predicts that only very early resections can prevent recurrence, and that small delays in the time of surgery can significantly increase the recurrence probability.

The majority of cancer related deaths are due to the development of secondary tumors called metastases. However, the dynamics of metastases establishment and growth and their relation with the primary tumor evolution are still not clear. A standard treatment starts with the resection of the primary tumor. At this time metastases may have already formed and still be too small to be detected. The presence of only undetectable metastases poses a challenge for deciding on the follow-up therapy. These small metastases could grow to a detectable size—thus leading to a recurrence of the disease—some time after surgery. We are interested in this time until cancer relapse. We present a mathematical model of metastases formation using tools from probability theory and estimate the model parameters for five different cancer types. Our predictions for the probability of visible metastases present at surgery and the mean time to relapse when no visible metastases are found at surgery are both in agreement with clinical data.

Prognostic significance of doubling time in patients undergoing radical surgery for metachronous peritoneal metastases of colorectal cancer

PURPOSE

The doubling times of tumor volume and tumor markers are associated with the prognosis of liver or lung metastases from colorectal cancer (CRC). However, no studies have assessed peritoneal metastases. Therefore, we aimed to elucidate the association between doubling time and the prognosis of patients who underwent radical surgery for metachronous peritoneal metastases of CRC.

METHODS

We calculated the tumor doubling times (TDT) of peritoneal metastases and serum carcinoembryonic antigen-doubling times (CEA-DT) in 33 consecutive patients who underwent radical surgery for metachronous peritoneal metastases between January 2006 and April 2017. The impact of short TDT and CEA-DT on overall survival (OS) and relapse-free survival (RFS) was retrospectively reviewed.

RESULTS

In long TDT (> 137 days) group, the 5-year OS rate was 74.1% and median OS time was 6.6 years. In long CEA-DT (> 102 days) group, the 5-year OS rate was 50.0% and median OS time was 5.6 years. Conversely, in short TDT (≤ 137 days) and CEA-DT (≤ 102 days) group, the 5-year OS rates and median OS times were both 0.0% and 3.2 years, respectively. In the multivariate analysis, short TDT was an independent risk factor for poor RFS (P = 0.006) and OS (P = 0.010). Similarly, short CEA-DT was also a poor risk factor for RFS (P < 0.001) and OS (P = 0.012).

CONCLUSIONS

Short TDT and CEA-DT are independent risk factors for poor OS and RFS after surgery for metachronous peritoneal metastases of CRC. TDT and CEA-DT should be considered when selecting candidates for surgical resection.

Estimation of Solid Tumor Doubling Times from Progression-Free Survival Plots Using a Novel Statistical Approach

Tumor doubling time can significantly affect the outcome of anticancer therapy, but it is very challenging to determine. Here, we present a statistical approach that extracts doubling times from progression-free survival (PFS) plots, which inherently contains information regarding the growth of solid tumors. Twelve cancers were investigated and multiple PFS plots were evaluated for each type. The PFS plot showing fastest tumor growth was deemed to best represent the inherent growth kinetics of the solid tumor, and selected for further analysis. The exponential tumor growth rates were extracted from each PFS plot, along with associated variabilities, which ultimately allowed for the estimation of solid tumor doubling times. The mean simulated doubling times for pancreatic cancer, melanoma, hepatocellular carcinoma (HCC), renal cell carcinoma, triple negative breast cancer, non-small cell lung cancer, hormone receptor positive (HR+) breast cancer, human epidermal growth factor receptor-2 positive (HER-2+) breast cancer, gastric cancer, glioblastoma multiforme, colorectal cancer, and prostate cancer were 5.06, 3.78, 3.06, 2.67, 2.38, 2.40, 4.31, 4.12, and 3.84 months, respectively. For all cancers, clinically reported doubling times were within the estimated ranges. For all cancers, except HCC, the growth rates were best characterized by a log-normal distribution. For HCC, the gamma distribution best described the data. The statistical approach presented here provides a qualified method for extracting tumor growth rates and doubling times from PFS plots. It also allows estimation of the distributional characteristics for tumor growth rates and doubling times in a given patient population.

Organotypic three-dimensional cancer cell cultures mirror drug responses in vivo: lessons learned from the inhibition of EGFR signaling

Complex three-dimensional (3D) in vitro models that recapitulate human tumor biology are essential to understand the pathophysiology of the disease and to aid in the discovery of novel anti-cancer therapies. 3D organotypic cultures exhibit intercellular communication, nutrient and oxygen gradients, and cell polarity that is lacking in two-dimensional (2D) monolayer cultures. In the present study, we demonstrate that 2D and 3D cancer models exhibit different drug sensitivities towards both targeted inhibitors of EGFR signaling and broad acting cytotoxic agents. Changes in the kinase activities of ErbB family members and differential expression of apoptosis- and survival-associated genes before and after drug treatment may account for the differential drug sensitivities. Importantly, EGFR oncoprotein addiction was evident only in the 3D cultures mirroring the effect of EGFR inhibition in the clinic. Furthermore, targeted drug efficacy was strongly increased when incorporating cancer-associated fibroblasts into the 3D cultures. Taken together, we provide conclusive evidence that complex 3D cultures are more predictive of the clinical outcome than their 2D counterparts. In the future, 3D cultures will be instrumental for understanding the mode of action of drugs, identifying genotype-drug response relationships and developing patient-specific and personalized cancer treatments.

Chronology of gastrointestinal cancer

The “chronology of cancer” is a concept that describes the nature of cancers through the measure of time. The field extends from carcinogenesis to development, progression, and metastasis. Carcinogenesis is a multi-step process, which results from the accumulation of multiple genetic or epigenetic alterations. Various chronologies of gastrointestinal cancers have been reported for carcinogenesis caused by different risk factors. These chronologies are useful for developing cancer prevention strategies. The tumor growth rate is one of the most important factors in this field. Combining the factors of time and tumor growth enables us to estimate the time at which cancer or metastasis occurred, retrospectively, and to predict the survival of cancer patients, prospectively. It is noteworthy that these chronologies differ significantly among individual cases, even of cancers derived from the same organ. Thus, they are useful for individualization. We can apply the knowledge obtained in this field to the basic research and the diagnosis and treatment of cancers. The chronology of cancer is a classical but interesting field, which helps us consider and explore the essence of cancer. We review the topics related to the chronology of gastrointestinal cancer, ranging from carcinogenesis to metastasis.

Consequences of Referral Time and Volume Doubling Time in Inoperable Patients With Early Stage Lung Cancer

BACKGROUND

Inoperable patients with early stage lung cancer are referred late. The purpose was to calculate the referral time and the volume doubling time (VDT), and to investigate its consequence with regard to staging and survival in 117 inoperable patients with early stage lung cancer treated with stereotactic body radiotherapy.

MATERIALS AND METHODS

Tumor VDT was calculated using the modified Schwartz formula of exponential growth model and was on the basis of volumes measured on initial diagnostic computed tomography (CT) scans and the planning CT scan. VDT was defined as fast (<100 days), moderate (100-249 days), slow (250-399 days), and no growth (≥400 days). The referral time is the time between the diagnostic CT scan and the radiotherapy planning CT scan.

RESULTS

The median referral time was 86 days. The VDT was fast in 53 patients [45%] of tumors. No significant difference in VDT was found between different tumor or patient characteristics. Patients with T1 tumors that progressed to T2 had a significant worse median survival (P = .01). The overall survival at 5 years according to VDT was 21% for fast-growing tumors, 19% for moderate growth, 31% for slow, and 46% for no growth.

CONCLUSION

The median referral time was almost 3 months. VDT was considered as fast in almost half of tumors examined. This resulted in significant growth and upstaging in 35% of the tumors, with a significant worse survival if T1 tumors progressed to T2 tumors. Therefore, medically inoperable patients should also be offered a fast workup and referral.

Screening Mammography in a Public Hospital Serving Predominantly African-American Women: A Stage-Survival-Cost Model

BACKGROUND

Ethnic and socioeconomic disparities pervade breast cancer patterns and outcomes. Mammography guidelines reflect the difficulty in optimizing mortality reduction and cost-effectiveness, with controversy still surrounding the 2009 U.S. Preventive Services Task Force (USPSTF) recommendations. This study simulates USPSTF and American Cancer Society (ACS) guidelines' effects on stage, survival, and cost of treatment in an urban public hospital.

METHODS

Charts of 274 women diagnosed with stage I, II, or III breast cancer (2008-2010) were reviewed. Published tumor doubling times were used to predict size at diagnosis under simulated screening guidelines. Stage distributions under ACS and USPSTF guidelines were compared with those observed. Cohort survival for observed and hypothetical scenarios was estimated using national statistics. Treatment costs by stage, calculated from Georgia Medicaid claims data, were similarly applied.

RESULTS

Mean age at diagnosis was 56 years. African Americans predominated (82.5%), with 96% publically insured or uninsured. Simulated stages at diagnosis significantly favored ACS guidelines (43.1% stage 1/38.3% stage 2/9.9% stage 3 vs. USPSTF 23.0%/53.3 %/15.0%), as did 5-year survival and cost of treatment relative to both observed and USPSTF-predicted schema (p<.0001). Following USPSTF guidelines predicted lower survival and additional costs.

CONCLUSIONS

Following ACS guidelines seems to lead to earlier diagnosis for low-income African-American women and increase 5-year survival with lower overall and breast-specific costs. The data suggest that adjusting screening practices for lower socioeconomic status, ethnic minority women may prove essential in addressing cancer disparities.

Spatial heterogeneity in drug concentrations can facilitate the emergence of resistance to cancer therapy

Acquired resistance is one of the major barriers to successful cancer therapy. The development of resistance is commonly attributed to genetic heterogeneity. However, heterogeneity of drug penetration of the tumor microenvironment both on the microscopic level within solid tumors as well as on the macroscopic level across metastases may also contribute to acquired drug resistance. Here we use mathematical models to investigate the effect of drug heterogeneity on the probability of escape from treatment and the time to resistance. Specifically we address scenarios with sufficiently potent therapies that suppress growth of all preexisting genetic variants in the compartment with the highest possible drug concentration. To study the joint effect of drug heterogeneity, growth rate, and evolution of resistance, we analyze a multi-type stochastic branching process describing growth of cancer cells in multiple compartments with different drug concentrations and limited migration between compartments. We show that resistance is likely to arise first in the sanctuary compartment with poor drug penetrations and from there populate non-sanctuary compartments with high drug concentrations. Moreover, we show that only below a threshold rate of cell migration does spatial heterogeneity accelerate resistance evolution, otherwise deterring drug resistance with excessively high migration rates. Our results provide new insights into understanding why cancers tend to quickly become resistant, and that cell migration and the presence of sanctuary sites with little drug exposure are essential to this end.

Failure of cancer therapy is commonly attributed to the outgrowth of pre-existing resistant mutants already present prior to treatment, yet there is increasing evidence that the tumor microenvironment influences cell sensitivity to drugs and thus mediates the evolution of resistance during treatment. Here, we take into consideration important aspects of the tumor microenvironment, including spatial drug gradients and differential rates of cell proliferation. We show that the dependence of fitness on space together with cell migration facilitates the emergence of acquired resistance. Our analysis indicates that resistant cells that are selected for in compartments with high concentrations are likely to disseminate from sanctuary sites where they first acquire resistance preceding migration. The results suggest that it would be helpful to improve clinical outcomes by combining targeted therapy with anti-metastatic treatment aimed at constraining cell motility as well as by enhancing drug transportation and distribution throughout all metastatic compartments.

Analysis of virotherapy in solid tumor invasion

Cancer treatment is an inexact science despite traditional cancer therapies. The traditional cancer treatments have high levels of toxicity and relatively low efficacy. Current research and clinical trials have indicated that virotherapy, a procedure which uses replication-competent viruses to kill cancer cells, has less toxicity and a high efficacy. However, the interaction dynamics of the tumor host, the virus, and the immune response is poorly understood due to its complexity. We present a mathematical analysis of models that study tumor-immune-virus interactions in the form of differential equations with spatial effects. A stability analysis is presented and we obtained analytical traveling wave solutions. Numerical simulations were obtained using fourth order Runge-Kutta and Crank-Nicholson methods. We show that the use of viruses as a cancer treatment can reduce the tumor cell concentration to a very low cancer dormant steady state or possibly deplete all tumor cells in body tissue. The traveling waves indicated an exponential increase and decrease in the cytotoxic-T-lymphocytes (CTLs) density and tumor load in the long term respectively.

Mathematical model of brain tumour with glia-neuron interactions and chemotherapy treatment

In recent years, it became clear that a better understanding of the interactions among the main elements involved in the cancer network is necessary for the treatment of cancer and the suppression of cancer growth. In this work we propose a system of coupled differential equations that model brain tumour under treatment by chemotherapy, which considers interactions among the glial cells, the glioma, the neurons, and the chemotherapeutic agents. We study the conditions for the glioma growth to be eliminated, and identify values of the parameters for which the inhibition of the glioma growth is obtained with a minimal loss of healthy cells.

Tumor doubling time of renal cell carcinoma measured by CT

Introduction:

Increasing numbers of patients are now being incidentally detected with small-sized renal cell carcinoma (RCC). The natural history of small renal masses is not completely understood. Currently, there are no specific tumor markers to determine initial risk or progression to metastatic disease. Growth rate and tumor size are factors shown to be predictive of tumor biology. In this study, we attempted to examine the natural history of RCC and calculated the doubling times (DTs) of untreated RCC at the primary site.

Materials and Methods:

We retrospectively reviewed the records of all patients with RCC who had at least two measurements of the same tumor mass obtained on computed tomography (CT) imaging on two different dates (at least 6 months apart) during periods of non-treatment. The tumor volume was calculated at two points in time using images yielded by the CT imaging. The tumor DT was calculated using the following equation: DT = (T – T0) × log2/logV – logV0.

Results:

Twenty-two (13 male and nine female) patients with ages ranging from 32 to 71 years (mean 52.22 years) were included in the study. The initial maximum tumor diameter ranged from 2.8 to 6.8 cm (mean 3.93 cm) and the last maximum tumor diameter ranged from 3.2 to 7.8 cm (mean 4.39 cm). The DT for the entire population was 460.01 days (range 174-913 days).

Conclusions:

RCC is a diverse disease process, with the majority of lesions demonstrating malignant disorder. In our study, the DT for the patient population was 460.01 days (range 174-913 days).

Optimal timing of pulmonary metastasectomy--is a delayed operation beneficial or counterproductive?

INTRODUCTION

Pulmonary metastasectomy represents an established approach in the treatment of lung metastases related to several solid malignant tumors, promising the chance of long term survival. Regarding the proper timing of metastasectomy both operation promptly after diagnosis and delayed operation after an interval of 3 months are common practice.

MATERIALS AND METHODS

A systematic Medline search addressing the optimal timing of metastasectomy was performed. Since the search query "timing of metastasectomy" yields only a limited number of articles, the Medline search was expanded to include the main arguments for prompt metastasectomy ("metastases of metastasis", "growth rate of pulmonary metastases") and for delayed metastasectomy.

RESULTS

Based on the data available to date, there is no necessity to expedite the timing of the operation. On the other hand, there is no evidence that a delayed operation, for example after re-staging following an interval of 3 months, provides a benefit.

CONCLUSION

Therefore the timing of metastasectomy should only depend on the patient's requirements, such as general state of health and oncologic considerations, such as promising multimodal therapy concepts, extrathoracal tumor manifestations or oncologic type of the primary tumor. A delayed operation seems justified if the indication for resection is questionable due to a high risk of early multilocal recurrence.

Tumor growth dynamics: insights into evolutionary processes

Identifying the types of event that drive tumor evolution and progression is crucial for understanding cancer. We suggest that the analysis of tumor growth dynamics can provide a window into tumor biology and evolution by connecting them with the types of genetic change that have occurred. Although fundamentally important, the documentation of tumor growth kinetics is more sparse in the literature than is the molecular analysis of cells. Here, we provide a historical summary of tumor growth patterns and argue that they can be classified into five basic categories. We then illustrate how those categories can provide insights into events that drive tumor progression, by discussing a particular evolutionary model as an example and encouraging such analysis in a more general setting.

Aggressive treatment of patients with metastatic colorectal cancer increases survival: a scandinavian single-center experience

Background. We examined overall and disease-free survivals in a cohort of patients subjected to resection of liver metastasis from colorectal cancer (CRLM) in a 10-year period when new treatment strategies were implemented. Methods. Data from 239 consecutive patients selected for liver resection of CRLM during the period from 2002 to 2011 at a single center were used to estimate overall and disease-free survival. The results were assessed against new treatment strategies and established risk factors. Results. The 5-year cumulative overall and disease-free survivals were 46 and 24%. The overall survival was the same after reresection, independently of the number of prior resections and irrespectively of the location of the recurrent disease. The time intervals between each recurrence were similar (11 ± 1 months). Patients with high tumor load given neoadjuvant chemotherapy had comparable survival to those with less extensive disease without neoadjuvant chemotherapy. Positive resection margin or resectable extrahepatic disease did not affect overall survival. Conclusion. Our data support that one still, and perhaps to an even greater extent, should seek an aggressive therapeutic strategy to achieve resectable status for recurrent hepatic and extrahepatic metastases. The data should be viewed in the context of recent advances in the understanding of cancer biology and the metastatic process.

Discrepancies between primary tumor and metastasis: a literature review on clinically established biomarkers

The identification of predictive factors of response is critical for the development and appropriate use of anti-cancer agents. The evaluation of biomarkers is usually performed by analyzing the primary tumor tissues but this approach does not take into account potential discrepancies between primary tumor and secondary lesions. This review proposes to describe currently available data regarding differential expression of established biomarkers between primary tumor and matched metastasis. In light of recent data, the need of iterative biopsies in metastatic setting has been suggested but technical and methodological limits in such analyses should not be ignored and this strategy cannot be definitively validated. Complementary studies are still needed since the question of spatial and temporal variability of biomarkers in solid tumors is clearly a key issue in an era where personalized therapy is strongly advocated by clinicians, researchers and patients.

The aggressiveness of murine lymphomas selected in vivo by growth rate correlates with galectin-1 expression and response to cyclophosphamide

Although lymphomas account for almost half of blood-derived cancers that are diagnosed each year, the causes of new cases are poorly understood, as reflected by the relatively few risk factors established. Galectin-1, an immunoregulatory ß-galactoside-binding protein, has been widely associated with tumor-immune escape. The aim of the present work was to study the relationship between tumor growth rate, aggressiveness, and response to cyclophosphamide (Cy) therapy with regard to Gal-1 expression in murine T-cell lymphoma models. By means of a disruptive selection process for tumor growth rate, we generated two lymphoma variants from a parental T-cell lymphoma, which have unique characteristics in terms of tumor growth rate, spontaneous regression, metastatic capacity, Gal-1 expression and sensitivity to Cy therapy. Here, we show that Gal-1 expression strongly correlates with tumor growth rate, metastatic capacity and response to single-dose Cy therapy in T-cell lymphoma models; this association might have important consequences for evaluating prognosis and treatments of this type of tumors.

Viewing metastatic colorectal cancer as a curable chronic disease

Improved survival of colorectal cancer has been made over the last 3 decades; reasons may be attributed to early detection through screening, and better treatment options. Advancements in modern systemic chemotherapy for colorectal cancer include oxaliplatin-based and irinotecan-based combination and the introduction of biological agents such as bevacizumab and cetuximab. Systemic therapies need to be used in patients with high risk stage II and stage III colorectal cancer and in patients with metastatic disease. Evidence for liver resection and ablation, pulmonary metastasectomy and/or radiofrequency ablation, and cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy for metastasis to sites of the liver, lung, and peritoneum respectively are well established. The biggest challenge is to select the right patients for metastasectomy and to pursue metastatic disease as a chronic disease to ensure appropriate personalized therapy, pursue second-line therapies or repeat surgeries, and minimize toxicities of therapies.

Radiotherapy for hepatocellular carcinoma: systematic review of radiobiology and modeling projections indicate reconsideration of its use

BACKGROUND AND AIMS

External beam radiotherapy currently has a limited role in the treatment of hepatocellular carcinoma (HCC). The purpose of this article was to review available radiobiological data on HCC and normal liver and incorporate these data into radiobiological models that may be used to explain and improve treatment.

METHODS

Volume doubling times of HCC were described and used to demonstrate growth of HCC with time, assuming both exponential and logistic growth. Radiosensitivity of HCC was described and used to demonstrate the probability of uncomplicated tumor control as tumor size increases. The relationship between tolerance of liver to irradiation and volume irradiated was examined.

RESULTS

The median volume doubling time for untreated HCC was 130 days. HCC have a long period of subclinical growth. Radiosensitivity of HCC lies within the range of other tumors commonly treated with radiotherapy. When treating small volumes of normal liver, relatively high doses may be used with low risk of late radiation damage. There is a high probability of sterilizing subclinical disease and small HCC with tolerable radiation doses.

CONCLUSION

New radiobiological data, modeling, emerging clinical data and the advantages offered by standard external beam radiotherapy techniques suggest the need for reconsidering the use of radiotherapy and for new trials.

Quantitative analysis of tumor growth rate and changes in tumor marker level: specific growth rate versus doubling time

BACKGROUND

Doubling time (DT) of tumor volume has been widely used to estimate the growth rate of tumors. However, DT gives incorrect estimates of the average growth rate of tumors when the uncertainty of growth rate is considerable. Specific growth rate (SGR) is less affected by uncertainties and is a more relevant parameter. Optimized imaging techniques and prolonged interval between observations can reduce the uncertainty of growth rate estimation. DT is also used for defining changes in tumor marker level. The aim of this study was to compare DT and SGR as measures of growth rate when the uncertainty is negligible.

METHODS

Mathematical analysis and computer simulations were carried out assuming no uncertainty of growth rate estimation. Data from two previously published clinical studies were assessed by both variables.

RESULTS

Due to the non-linear relationship between DT and SGR, using these variables does not give similar results. The variation of DT is not uniformly indicating variations of the growth rate. DT largely overestimates the difference in growth rate of slowly growing tumors and underestimates the difference in growth rate of rapidly growing tumors. On the other hand, SGR uniformly indicates the difference between growth rates throughout all ranges. Quantitative analysis of clinical observations can lead to contradictory results depending on the variable used for growth rate.

CONCLUSION

The growth rate of tumor volume should be expressed by SGR, or percentage increase per unit time, regardless of the level of the uncertainty of growth rate estimation. This conclusion is also valid for changes in tumor marker level, whether it is correlated with the growth rate of tumor volume or not.

Parallel progression of primary tumours and metastases

Systemic cancer progression is accounted for in two basic models. The prevailing archetype places the engine of cancer progression within the primary tumour before metastatic dissemination of fully malignant cells. The second posits parallel, independent progression of metastases arising from early disseminated tumour cells. This Perspective draws together data from disease courses, tumour growth rates, autopsy studies, clinical trials and molecular genetic analyses of primary and disseminated tumour cells in support of the parallel progression model. Consideration of this model urges review of current diagnostic and therapeutic routines.

Specific growth rate versus doubling time for quantitative characterization of tumor growth rate

Doubling time (DT) is widely used for quantification of tumor growth rate. DT is usually determined from two volume estimations with measurement time intervals comparable with or shorter than DT. Clinical data show that the frequency distribution of DT in patients is positively skewed, with some very long DT values compared with the average DT. Growth rate can also be quantified using specific growth rate (SGR; %/d), equal to ln2/DT. The aim of this work was to compare DT and SGR as growth rate variables. Growth rate calculations were computer simulated for a tumor with DT of 100 days, measurement time interval of 1 to 200 days, and volume estimation uncertainty of 5% to 20%. Growth rate variables were determined and compared for previously published clinical data. The study showed that DT is not a suitable variable for tumor growth rate because (a) for short measurement time intervals, or high volume uncertainties, mean DT can either overestimate or underestimate the average growth rate; (b) DT is not defined if the consecutively estimated volumes are equal; and (c) the asymmetrical frequency distribution of DT makes it unsuitable for common statistical testing. In contrast, mean SGR and its equivalent DT give the correct values for average growth rate, SGR is defined for all tumor volume changes, and it has a symmetrical frequency distribution. SGR is also more accurate to use when discussing, for example, growth fraction, cell loss rate, and growth rate heterogeneities within the tumor. SGR should thus be used, instead of DT, to quantify tumor growth rate.

Effect on tumour control of time interval between surgery and postoperative radiotherapy: an empirical approach using Monte Carlo simulation

In this work, a procedure, based on Monte Carlo techniques, to analyse the effect on the tumour control probability of the time interval between surgery and postoperative radiotherapy is presented. The approach includes the tumour growth as well as the survival of tumour cells undergoing fractionated radiotherapy. Both processes are described in terms of the binomial distribution. We have considered two different growth models, exponential and Gompertz, the parameters of which have been fixed to reproduce the clinical outcome corresponding to a retrospective study for patients with head and neck squamous cell carcinomas. In the cases analysed, we have not found significant differences between the results obtained for both growth models. The mean doubling times found for residual clonogens after surgery are less than 40 days. The rate of decrease in local control is around 0.09% per day of delay between surgery and radiotherapy and the corresponding time factor is about 0.11 Gy per day.

The pattern of breast cancer screening utilization and its consequences

BACKGROUND

The objective of this study was to describe the pattern of screening utilization and its consequences in terms of tumor size and time of tumor appearance of invasive breast carcinoma among a population of women who were examined at a large service screening/diagnostic program over the last decade.

METHODS

Utilization of mammography was assessed from a population of 59,899 women who received 196,891 mammograms at the Massachusetts General Hospital Breast Imaging Division from January 1, 1990 to March 1, 1999, among which 604 invasive breast tumors were found. Two hundred six invasive, clinically detected tumors also were seen during this period among women who had no record of a previous mammogram. Additional information was available on screening of women from March 1, 1999 to June 1, 2001.

RESULTS

Fifty percent of the women who used screening did not begin until the age of 50 years, although 25% of the invasive breast tumors were found in women age < 50 years. Relatively few of the women who used screening returned promptly for their annual examinations; by 1.5 years, only 50% had returned. Approximately 25% of the invasive breast tumors were found in women for whom there was no record of a previous screening mammogram, and these tumors were larger (median, 15 mm) than the screen-detected tumors (median, 10 mm). Approximately 30% of the 604 invasive breast tumors in the screening population were found on nonmammographic grounds, and they also were larger (median, 15 mm) than the screen-detected tumors (median, 10 mm). However, only 3% of these 604 tumors were found by nonmammographic criteria within 6 months of the previous negative examination, and only 12% were found within 1 year. By back calculating the likely size of each of these tumors at the time of the negative mammogram, it could be seen that most tumors probably emerged as larger, palpable masses not because they were missed at the previous negative mammogram, because most were too small then to have been detected, but because too much time had been allowed to pass.

CONCLUSIONS

Far too many women did not comply with the American Cancer Society recommendation of prompt annual screening from the age of 40 years. Consequently, almost 50% of the invasive tumors emerged as larger and, thus, potentially more lethal, palpable masses.

Tumour dormancy: findings and hypotheses from clinical research on breast cancer

Breast cancer metastatic development is commonly considered as resulting from continuous tumour growth from tumour seeding until clinical recurrence is documented. Continuous growth model inferences, however, fail to explain clinical findings concerning local recurrences, as well as the time-distribution of first treatment failure and mortality for patients undergoing mastectomy. The tumour dormancy hypothesis is considered to provide a more reasonable description of the natural history of breast cancer, while primary tumour removal is believed to be a potential perturbing factor for metastasis development. A new model of the natural history of operable breast cancer, incorporating tumour dormancy and starting signals from surgery for micrometastatic growth is proposed.

Growth rate of pancreatic adenocarcinoma: initial clinical experience

A better understanding of the growth rate of pancreatic carcinoma is important in determining its natural course and in evaluating the effects of treatment or prognosis. The authors studied the growth rate of pancreatic carcinoma and the relation between its tumor volume doubling time (TVDT) and host survival. Nine patients with pancreatic carcinoma who underwent serial examinations by helical computed tomography but no anticancer treatment during the observation period were included. The TVDTs were calculated by measuring the tumor size on the helical computed tomograms. The mean TVDT of the nine primary lesions of pancreatic carcinoma was 159 +/- 67 days (median, 144 days), and the range was 64 to 255 days. The correlation between TVDT and survival time was positive and significant (r = 0.793, p = 0.011). This preliminary study suggests that examination of TVDT may be useful in the clinical evaluation of prognosis for patients with pancreatic carcinoma in certain situations.

In vitro DNA synthesis in freshly separated human breast cancer cells assessed by tritiated thymidine incorporation assay: relationship to the long-term outcome of patients

BACKGROUND

Tumour growth rate has a significant effect on the clinical course of various malignancies. The present study was designed to assess whether in vitro DNA synthesis in freshly separated breast cancer cells is a useful marker in evaluating growth rates and in predicting the clinical outcome of patients.

METHODS

From 1982 to 1992, DNA synthesis was assessed by [3H]thymidine incorporation in 97 samples of primary lesions from 94 patients with breast cancer. The patients were followed for 5-15 years and their outcome was surveyed in January 1998.

RESULTS

The level of DNA synthesis did not correlate with the patients' age, clinical stage or expression of oestrogen receptor. However, it correlated significantly with the histological grade. In 89 patients, whose outcome was reported, the survival rate in the group with a high rate of DNA synthesis (log10c.p.m. 3.0 or more) was significantly lower than that in the low-level group; the 5- and 10-year survival rates were 84 and 74 per cent for the low synthesis group (n = 46), and 60 and 46 per cent for the high synthesis group (n = 43) respectively. This was also noted in patients with stage 1 or 2 cancers, for whom the 5- and 10-year survival rates were 100 and 90 per cent for the low synthesis group (n = 25), and 75 and 70 per cent for the high synthesis group (n= 35). Multivariate analysis supported this significant correlation for DNA synthesis in the prognosis of patients after mastectomy. Furthermore, the level of DNA synthesis was significantly higher in 18 patients who died from a recurrence within 3 years after operation than in 56 survivors, and the level of DNA synthesis also correlated significantly with the survival period in the 33 patients who died.

CONCLUSION

The level of DNA synthesis in breast cancer was variable, and was independent of the clinical stage or oestrogen receptor status. However, a high level of DNA synthesis was a positive indicator of a high risk of recurrence after operation, especially for stage 1 or 2 breast cancer. In vitro DNA synthesis may account for some of the clinical characteristics of breast cancers.

Breast cancer: computer simulation method for estimating optimal intervals for screening

PURPOSE

To develop and evaluate a mathematic method that can be used to determine the optimal screening interval for detection of breast cancer prior to distant metastatic spread.

MATERIALS AND METHODS

A computer simulation was developed with the use of biologically based data from the literature on the rates of tumor growth and spread, which can be used to calculate the course of breast cancer growth and metastasis.

RESULTS

On the basis of the data available at this time, the results of the simulations suggested that a screening interval of 2 years would result in a 22% reduction in the rate of distant metastatic disease, an interval of 1 year would result in a 51% reduction, and an interval of 6 months would result in an 80% reduction.

CONCLUSION

These findings suggest that more frequent screening could dramatically reduce the death rate from breast cancer.

Estimate of tumor growth time for breast cancer local recurrences: rapid growth after wake-up?

To obtain an estimate of the subclinical tumor growth time (TGT) for breast cancer, a series of 31 patients with local recurrence as first event after mastectomy was evaluated. The recurrence diameter was measured, and the minimum growth rate (mGR) consistent with the sequence 'no detection at the preceding physical examination-->recurrence of diameter Dr' was obtained. The growth rate for uninterrupted exponential growth from surgery (GRu) was also calculated. mGR was significantly higher than GRu (p < 0.0001), and unrelated to the recurrence-free survival (RFS). Therefore, starting points of local recurrence growth curves had to be set at times variously delayed after mastectomy. The estimate of the delay lower limit (mD), which was obtained from mGR and GRu, showed a strong linear correlation with RFS (R = 0.984; p < 0.0001). From the regression equation, TGT for local recurrences could be estimated at 30+/-8 weeks or less. These findings support the concept that the lag time between surgical treatment of breast cancer and clinical evidence of local recurrence may be explained by a period of tumor dormancy followed by a tumor growing phase. The TGT estimate is remarkably shorter than previously believed and could considerably change the current picture of breast cancer history.

The impact of delayed diagnosis of lung cancer on the stage at the time of operation

OBJECTIVE

The purpose of this investigation was to study the correlation between diagnostic delay and the stage of the lung cancer at the time of operation. A second objective was to study differences in symptoms between the patients grouped according to stage.

METHODS

A total of 172 patients consecutively admitted for surgery between 1 January 1994 and 1 June 1995 at the Department of Thoracic and Cardiovascular Surgery of Rigshospitalet National Hospital of Denmark were included in the retrospective study. Two groups of patients were compared, one group with good prognosis (patients in Stages I and II) and one group with poor prognosis (patients in Stages III and IV). The time-spans studied were: (1) interval from the patient's perception of the first symptom to operation; and (2) the time from first contact with the healthcare-system to operation. The median delay between the patient-groups was compared using the Mann-Whitney U-test. To compare the symptoms which brought the patients in contact with the healthcare-system, the chi2-test was used.

RESULTS

In the time interval between appearance of the first symptom and operation, a significantly shorter median delay was found for patients with Stages I and II compared to Stages III and IV (P = 0.037). Concerning the interval from first contact with the healthcare system to operation a significantly shorter median delay was found for the group of patients in Stage I and II compared to the patients-group in Stage III and IV (P = 0.017). It was found that the cancer was an accidental finding, significantly more often in patients in Stages I or II compared to patients in Stages III or IV (P = 0.0002).

CONCLUSIONS

A few months delay before final treatment of a non-small-cell lung cancer seems to have an impact on the perioperative stage of the cancer, and thereby on the patients prognosis. A screening of asymptomatic risk-group patients will result in recognition of early lung cancer.

On the growth rates of human malignant tumors: implications for medical decision making

Testicular carcinomas, pediatric tumors, and some mesenchymal tumors are examples of rapidly proliferating cell populations, for which the tumor volume doubling time (TVDT) can be counted in days. Cancers from the breast, prostate, and colon are frequently slow-growing, displaying a TVDT of months or years. Irrespective of their growth rates, most human tumors have been found: to start from one single cell, to have a long subclinical period, to grow at constant rates for long periods of time, to start to metastasize often even before the primary is detected, and to have metastases that often grow at approximately the same rate as the primary tumor. The recognition of basic facts in tumor cell kinetics is essential in the evaluation of important present-day strategies in oncology. Among the facts emphasized in this review are: (1) Screening programs. Most tumors are several years old when detectable by present-day diagnostic methods. This makes the term "early detection" questionable. (2) Legal trials. The importance of so-called doctor's delay is often discussed, but the prognostic value of "early" detection is overestimated. (3) Analyses of clinical trials. Such analysis may be differentiated depending on the growth rates of the type of tumor studied. Furthermore, uncritical analysis of survival data may be misleading if the TVDT is not taken into consideration. (4) Analyses of epidemiological data. If causes of malignant tumors in humans are searched for, the time of exposure must be extended far back in the subject's history. (5) Risk estimations by insurance companies. For the majority of human cancers, the 5-year survival rate is not a valid measurement for cure. Thus, basic knowledge of tumor kinetics may have important implications for political health programs, legal trials, medical science, and insurance policies.

Monitoring tumour response

Monitoring response to treatment of tumours is an increasingly important aspect of cancer radiology for several reasons. Firstly, the incidence of cancer is increasing and, furthermore, there have been major advances in treatment which have resulted in a larger number of patients surviving with treated tumours. Equally important is that there have been enormous advances in imaging over the past two decades which now permit us to obtain highly sophisticated information on tumour morphology and function using a variety of different techniques. In this review emphasis is placed on strategies for imaging in the follow-up of cancer patients and the information derived from current imaging techniques is described with particular reference to CT and MRI.

Growth rate of lung metastases and S-phase fraction as determined by flow cytometry from the primary tumour in 25 patients with bone or soft-tissue sarcomas

A significant correlation (r = -0.48) was found between the logarithm of the S-phase fraction of the primary tumour (SPF) and the logarithm of the doubling time of lung metastases (T2). The estimated median cell loss factor was 88% (range 35-99%).

Time distribution of the recurrence risk for breast cancer patients undergoing mastectomy: further support about the concept of tumor dormancy

PURPOSE

To gather information on metastatic growth from the time-distribution of first treatment failure in breast cancer patients undergoing mastectomy alone.

METHODS

The risk of recurrence at a given time after surgery was studied utilizing the cause-specific hazard function. Recurrence was categorized as first treatment failure at any site, local-regional recurrence, distant metastases, and contralateral tumor. The risk distribution was assessed relative to tumor size, axillary lymph node involvement, and menopausal status.

RESULTS

A total of 1173 patients treated between 1964 and 1980 with mastectomy alone and no adjuvant therapy were studied. The hazard function for first failure presented an early peak at about 18 months after surgery, a second peak at about 60 months and then a tapered plateau-like tail extending up to 15 years. A similar risk pattern was detectable for both local recurrence and distant metastases, while the curve of contralateral breast tumors showed a near flat plateau. The risk of early local-regional and distant recurrences was much lower for tumors less than 2 cm in diameter than for larger tumors; the risk of late recurrence was similar for small and large primaries. Node-positive patients showed peaks four to five times higher than node-negative patients. Sub-dividing node-positive patients into 1-3 and > 3 node-positive subsets did not substantially change the general picture of tumor recurrence. The hazard functions for premenopausal and postmenopausal patients were virtually superimposable.

CONCLUSIONS

The multipeak hazard curve suggests that the process resulting in overt clinical metastases may have discrete features. Primary tumor size could affect in different ways early and late metastases, while axillary node status should be related to the risk level, not to the risk pattern, and menopausal status does not seem to significantly affect the hazard distribution. Moreover, contralateral breast tumors, occurring at constant risk throughout the time, should be considered as second primary cancers. These findings could be reasonably explained by a tumor dormancy hypothesis, which assumes that micrometastases may be in different biological steady states, most of which do not imply tumor growth. Tumor or microenvironment changes could induce metastatic growth after given mean transition times from surgery and originate a discrete pattern of the hazard function.

Rates of growth of human neoplasms: Part II

Part I of this study [Spratt JS, Meyer JS, Spratt JA: J Surg Oncol 60:137-146, 1995] reviewed the early reports of investigators, predominantly mathematical biologists and statisticians considering the mathematical laws that would describe the growth of a neoplasm. Included were cytokinetic measurements of the mitotic index, thymidine labeling index, bromodeoxy-uridine labeling index, and the relation of these indices to the potential tumor volume doubling time. The actual doubling time of benign and malignant colonic neoplasms were reported. This second part provides the cumulative observations on the actual doubling times of pulmonary metastases, primary pulmonary cancers, skeletal sarcomas, melanomas, a chemodectoma, tumors of maxillary antrum, testicular cancers, prostate cancer, and the relation between the accumulation of multiple primary cancers and growth rates. The most complete data set is for breast cancer concluding that the cancer growth curve is a decelerating curve with great natural variance. Understanding of the rates of growth of human cancers is essential for understanding the spectrum of cancer behavior observed clinically.

The effect of delay in treatment on local control by radiotherapy

PURPOSE

The objective of this study was to estimate the effect of delay in initiation of treatment on rates of local control by radiotherapy.

METHODS AND MATERIALS

A model of the effects of delay was developed based on the following assumptions: (a) that tumor growth rate is exponential, (b) that a predetermined radiotherapy regimen will kill the same fraction of clonogenic cells in a given tumor whether it is administered early or late, and (c) that the absolute number of cells surviving in a tumor is determined by Poisson statistics. Monte Carlo simulation was used to estimate the expected rate of decrease in local control associated with delay in a population of tumors, which was heterogeneous with respect to doubling time and initial volume. The model was applied to carcinoma of the tonsillar region.

RESULTS

It was shown that at some point in the evolution of every case, the probability of local control decreases sharply over a relatively short period of time. The maximum rate of decrease in the probability of local control occurs at the 37% local control level when it reaches 25.5% per tumor doubling time. When heterogeneity with respect to doubling time and stage was taken into account, it was estimated that the local control rate would decrease by approximately 10% per month in a typical series of patients with carcinoma of the tonsillar region.

CONCLUSIONS

It was concluded that delay in initiation of radiotherapy may be associated with a clinically important deterioration in local control rates. We recommend that waiting times for radiotherapy should be As Short As Reasonably Achievable (ASARA).

Rates of growth of human solid neoplasms: Part I

The purpose of this article is to consolidate data collected from a variety of sources that have permitted calculations of the rates of growth of human neoplasms. These sources include Fischel State Cancer Hospital (Columbia, MO); Mallinckrodt Institute of Radiology, (St. Louis, MO); Roentgen Diagnostic Institute, Allmanna Sjukhuset (Malmo, Sweden); University of Louisville (Louisville, Kentucky); University of Heidelberg (Heidelberg, Germany); and St. Luke's Hospital (St. Louis, MO). Included in the data are laboratory measurements of cell replication rates. All gross measurements were made either on imaging studies or with a centimeter scale for surface or palpable neoplasms. Data have been reported for breast and pulmonary cancers and metastases of many types, melanomas, skeletal sarcomas, benign and malignant colonic neoplasms, and isolated cases of less frequent neoplasms. Related cytokinetic measurements by tritriated thymidine labelling, bromodeoxyuridine labelling, S-phase fraction from DNA flow cytometric analysis, and mitotic indices are discussed. The various mathematical formulae applicable to the analysis of the collected data and the determination of rates and patterns of growth are included. Also considered are the clinical implications of these data and the importance of ever better knowledge on the cytokinetics of human cancer. Prior studies on the evolution of insight into this field are cited and discussed. The authors conclude that a more accurate quantification of the growth rates of human cancer is essential for understanding the biological variance of human cancers seen clinically.

Observations on the growth rate of renal cell carcinoma

We retrospectively reviewed the records of 18 patients to investigate the growth rate of renal cell carcinoma (RCC). Growth rates were calculated from two or more gross measurements of neoplastic foci in the kidney (6 cases) and lung (12 cases). RCCs in primary sites grew slowly and the tumor volume doubling time (DT) raged from 372 to 579 days (468 +/- 84.6). Pulmonary metastases present in 12 cases grew rapidly, with a DT ranging from 20 to 154 days (89.4 +/- 43.0). Tumors in both the kidney and lung were composed of cancer cells with equal proliferative activity, as determined by immunohistochemical analysis of argyrophilic nucleolar organizer regions and proliferating cell nuclear antigen activity. Thus, our results suggest that, in addition to the proliferative activity of cancer cells, the microenvironment of the specific region is an important determinant of the growth rate of cancer cells.