Growth Rate of Soft Tissue Sarcomas: A Quantitative Study of 44 Local Recurrences

Predicting Tumor Volume Doubling Time and Progression-Free Survival in Untreated Patients from Patient-Derived-Xenograft (PDX) Models: A Translational Model-Based Approach

Tumor volume doubling time (TVDT) has been shown to be a potential surrogate marker of biological tumor activity. However, its availability in clinics is strongly limited due to ethical and practical reasons, as its assessment requires at least two subsequent tumor volume measurements in untreated patients. Here, a translational modeling framework to predict TVDT distributions in untreated cancer patient populations from tumor growth data in patient-derived xenograft (PDX) mice is proposed. Eleven solid cancer types were considered. For each of them, a set of tumor growth studies in PDX mice was selected and analyzed through a mathematical model to characterize the distribution of the exponential tumor growth rate in mice. Then, assuming an exponential growth of the tumor mass in humans, the growth rates were scaled from PDX mice to humans through an allometric scaling approach and used to predict TVDTs in untreated patients. A very good agreement was found between model predicted and clinically observed TVDTs, with 91% of the predicted TVDT medians fell within 1.5-fold of observations. Further, exploiting the intrinsic relationship between tumor growth dynamics and progression free survival (PFS), the exponential growth rates in humans were used to generate the expected PFS curves in absence of anticancer treatment. Predicted curves were extremely close to published PFS data from studies involving patient cohorts treated with supportive care or low effective therapies. The proposed approach shows promise as a potential tool to increase knowledge about TVDT in humans without the need of directly measuring tumor dimensions in untreated patients, and to predict PFS curves in untreated patients, that could fill the absence of placebo-controlled arms against which to compare treaded arms during clinical trials. However, further validation and refinement are needed to fully assess its effectiveness in this regard.

The Growth Rate in the Interpretation of the Natural History of Lung Cancer

The relationship between growth rate, expressed as doubling time (DT), of 110 lung cancers from randomly collected patients and patient age, sex, histological type, symptoms, smoking habits, size and lymph node involvement was studied. Median DT values of epidermoid carcinomas and adenocarcinomas were superimposable (98 and 99 days, respectively), but 15 % of adenocarcinomas had a DT of more than one year. Significant correlations were found with sex (slower growth rate in females) and symptoms (faster growth in symptomatic patients), but only for adenocarcinomas. The number of cigarettes smoked did not seem to affect the growth rate of lung cancers. There was no correlation between growth rate and tumor size or lymph node involvement.

Prognostic Significance of the Growth Rate of Breast Cancer: Preliminary Evaluation on the Follow-Up of 196 Breast Cancers

The doubling time (DT) of 196 consecutive breast cancers was studied by means of a double mammographic examination (average time between the 2 mammographies, 30 days) and calculated with the formula of exponential growth. On the basis of DT values the case series was divided into 3 groups of growth: fast (DT from 1 to 30 days), 31 cases (15.8 %), intermediate (DT from 31 to 90 days), 84 cases (42.9 %), slow (DT more than 90 days), 81 cases (41.3 %). No relationship was found between growth rate and size of tumor, or menopausal status of the patient. After mastectomy fast and slow cases were equally distributed in the N− and N+ groups, whereas for the intermediate cases the N−: N+ ratio was 1: 2. One hundred and thirty-four cases were followed for a period of 12 to 52 months. Evaluation was done on the basis of the subdivision into N− and N+, and the latter group into N+ (1–3) and N+ (> 3). For N− tumors the course of the disease was apparently not affected by the growth rate. However, the case of fast growing tumors showed a higher proportion of recurrences with respect to N+ slow growing tumors. This difference was even more noticeable the higher the number of involved lymph nodes, but not statistically significant. The course of slow growing tumors was identical in the N− and N+ groups, but all the N+ tumors were subjected to adjuvant chemotherapy.

Experimental model for locally recurring mammary tumors. Development, morphology, karyotype, growth kinetics, and experimental metastatic potential

A rat model was established for evaluating the biology of locally recurring mammary tumors after surgical resection of the primary tumor. Eight distinct cell lines were independently derived from primary tumors and local recurrences after surgical removal of 13762NF rat mammary adenocarcinoma clone MTF7(T20). In vivo tumor doubling times between the "parental" MTF7(T20) cell line, primary tumor-derived cell lines sc1 and sc3, and the local recurrence (LR) sublines varied after the inoculation of 10(6) tumor cells into the mammary fat pad of female Fischer 344 rats. Doubling times were shorter for LR3, and LR4, LR5, and LR6 than their primaries sc3 and MTF7(T20), respectively, and longer for LR1 and LR1a than their primary tumor sc1. The LR sublines varied considerably for their experimental metastatic potentials. Both increases and decreases in metastatic potential were seen compared to MTF7(T20), sc1, and sc3. Karyotype analysis by G-banding revealed the presence in the LR sublines of several marker chromosomes, previously identified in MTF7 at tissue cultures 11 and 35. Two new chromosome markers were identified: M54, shared by MTF7(T20), sc1, LR4, LR5 and LR6, and M55, shared by MTF7(T20), sc1, LR1, sc3, LR3, LR4, and LR6. These data indicate that local tumor regrowth after surgical excision of the primary tumor in this model most likely selects the growth of tumor cell subpopulations already present within the primary tumor. Differences in growth kinetics, karyotype, and metastatic potential between the parental MTF7(T20), primary tumors sc1 and sc3, and their LR sublines may reflect in vivo influences on the phenotypic diversity generated during the development of local mammary tumor recurrences after surgical treatment of the primary tumor.