Measurement of growth rate of lung metastases in 21 patients with bone or soft-tissue sarcoma

Ultra-low-dose computed tomography and chest X-ray in follow-up of high-grade soft tissue sarcoma-a prospective comparative study

Ultra-low-dose computed tomography (ULD-CT) may combine the high sensitivity of conventional computed tomography (CT) in detecting sarcoma pulmonary metastasis, with a radiation dose in the same magnitude as chest X-ray (CXR). Fifty patients with non-metastatic high-grade soft tissue sarcoma treated with curative intention were recruited. Their follow-up involved both CXR and ULD-CT to evaluate their different sensitivity. Suspected findings were confirmed by conventional CT if necessary. Patients with isolated pulmonary metastases were treated with surgery or stereotactic body radiation therapy (SBRT) with curative intent if possible. The median effective dose from a single ULD-CT study was 0.27 mSv (range 0.12 to 0.89 mSv). Nine patients were diagnosed with asymptomatic lung metastases during the follow-up. Only three of them were visible in CXR and all nine in ULD-CT. CXR had therefore only a 33% sensitivity compared to ULD-CT. Four patients were operated, and one had SBRT to all pulmonary lesions. Eight of them, however, died of the disease. Two patients developed symptomatic metastatic recurrence involving extrapulmonary sites+/-the lungs between two imaging rounds. ULD-CT has higher sensitivity for the detection of sarcoma pulmonary metastasis than CXR, with a radiation dose considerably lower than conventional CT.Clinical trial registration: NCT05813808. 04-14-2023.

Evaluation of the stability and intratumoral delivery of foreign transgenes encoded by an oncolytic Foamy Virus vector

Foamy Viruses are cell cycle-dependent retroviruses capable of persisting unintegrated in quiescent cells until cell division occurs. This unique ability allows them to target slowly dividing human tumor cells which remains an unmet need in oncolytic virotherapy. We have previously reported the generation of oncolytic Foamy Virus (oFV) vector system and demonstrated its superiority over oncolytic Murine Leukemia Virus vectors in infecting slowly dividing cancer cells. In the present study we evaluated (i) the ability of oFV to carry foreign transgenes and (ii) the genetic stability of these vectors upon serial passage. The thymidine kinase (TK) and inducible caspase 9 (iCasp9) cDNAs could be detected in the oFV backbone for up to 3 in vitro passages. In vivo, GFP-, TK- and iCasp9- carrying oFV vectors propagated efficiently in subcutaneous xenograft glioblastoma tumors and drove transgene expression for up to 66 days. However, in vivo oFV vector spread eventually resulted in complete loss of the iCasp9 cDNA, minor loss of the TK cDNA and negligible loss of the GFP. Our results suggest that oFV is a promising gene delivery platform and that transgenes smaller than 1 kb might be most suitable for oFV arming.

Oncolytic Foamy Virus - generation and properties of a nonpathogenic replicating retroviral vector system that targets chronically proliferating cancer cells

Nonpathogenic retroviruses of the Spumaretrovirinae subfamily can persist long-term in the cytoplasm of infected cells, completing their lifecycle only after the nuclear membrane dissolves at the time of cell division. Since the targeting of slowly dividing cancer cells remains an unmet need in oncolytic virotherapy we constructed a replication competent Foamy Virus vector (oFV) from the genomes of two chimpanzee Simian Foamy Viruses (PAN1 and PAN2) and inserted a GFP transgene in place of the bel-2 open reading frame. oFV-GFP infected and propagated with slow kinetics in multiple human tumor cell lines, inducing a syncytial cytopathic effect. Infection of growth arrested MRC5 cells was not productive, but oFV genomes persisted in the cytoplasm and the productive viral lifecycle resumed when cell division was later restored. In vivo, the virus propagated extensively in intraperitoneal ovarian cancer xenografts, slowing tumor growth, significantly prolonging survival of the treated mice and sustaining GFP transgene expression for at least 45 days. Our data indicate that oFV is a promising new replication-competent viral and gene delivery platform for efficient targeting of the most fundamental trait of cancer cells, their ability to sustain chronic proliferation.Significance:The infectivity of certain retroviruses is limited to dividing cells, which makes them attractive tools for targeting cancer cell proliferation. Previously developed replication-competent gammaretroviral vectors spread efficiently in rapidly dividing cancer cells, but not in cancer cells that divide more slowly. In contrast to rapidly proliferating transplantable mouse tumors, slow proliferation is a hallmark of human cancers and may have contributed to the clinical failure of the preclinically promising Murine Leukemia Virus vector Toca511 which failed to show efficacy in a phase 3 clinical trial in patients with glioblastoma. The studies presented in our manuscript show that oncolytic Foamy Virus (oFV) vectors are capable of persisting unintegrated in quiescent cells and resuming their life cycle once the cells start dividing again. This property of oFVs, together with their lack of pathogenicity and their ability to catalyze the fusion of infected cancer cells, makes them an attractive platform for further investigation.

Linear mixed-effects models for estimation of pulmonary metastasis growth rate: implications for CT surveillance in patients with sarcoma

OBJECTIVES

Sarcoma patients often undergo surveillance chest CT for detection of pulmonary metastases. No data exist on the optimal surveillance interval for chest CT. The aim of this study was to estimate pulmonary metastasis growth rate in sarcoma patients.

METHODS

This was a retrospective review of 95 patients with pulmonary metastases (43 patients with histologically confirmed metastases and 52 with clinically diagnosed metastases) from sarcoma treated at an academic tertiary-care center between 01 January 2000 and 01 June 2019. Age, sex, primary tumor size, grade, subtype, size and volume of the pulmonary metastasis over successive chest CT scans were recorded. Two metastases per patient were chosen if possible. Multivariate linear mixed-effects models with random effects for each pulmonary metastasis and each patient were used to estimate pulmonary metastasis growth rate, evaluating the impact of patient age, tumor size, tumor grade, chemotherapy and tumor subtype. We estimated the pulmonary metastasis volume doubling time using these analyses.

RESULTS

Maximal primary tumor size at diagnosis (LRT statistic = 2.58, df = 2, p = 0.275), tumor grade (LRT statistic = 1.13, df = 2, p = 0.567), tumor type (LRT statistic = 7.59, df = 6, p = 0.269), and patient age at diagnosis (LRT statistic = 0.735, df = 2, p = 0.736) were not statistically significant predictors of pulmonary nodule growth from baseline values. Chemotherapy decreased the rate of pulmonary nodule growth from baseline (LRT statistic = 7.96, df = 2, p = 0.0187). 95% of untreated pulmonary metastases are expected to grow less than 6 mm in 6.4 months. There was significant intrapatient and interpatient variation in pulmonary metastasis growth rate. Pulmonary metastasis volume growth rate was best fit with an exponential model in time. The volume doubling time for pulmonary metastases assuming an exponential model in time was 143 days (95% CI (104, 231) days).

CONCLUSIONS

Assuming a 2 mm nodule is the smallest reliably detectable nodule by CT, the data suggest that an untreated pulmonary metastasis is expected to grow to 8 mm in 8.4 months (95% CI (4.9, 10.2) months). Tumor size, grade and sarcoma subtype did not significantly alter pulmonary metastasis growth rate. However, chemotherapy slowed the pulmonary metastasis growth rate.

ADVANCES IN KNOWLEDGE

CT surveillance intervals for pulmonary metastases can be estimated based on metastasis growth rate. There was significant variation in the pulmonary metastasis growth rate between metastases within patient and between patients. Pulmonary nodule volume growth followed an exponential model, linear in time.

(Neo)adjuvant chemotherapy and interdigitated split-course hyperfractionated radiation in high risk soft tissue sarcoma - Results from a large single-institution series

A single-institution series using a (neo)adjuvant chemotherapy and interdigitated hyperfractionated split-course radiation therapy (CRT) treatment protocol for soft tissue sarcoma was reviewed. Our specific aims were to study recurrence rates and long-term toxicity. Between 1998 and 2016, 89 patients with non-metastatic soft tissue sarcoma were treated with surgery combined with six courses of doxorubicin and ifosfamide and hyperfractionated radiation therapy (42-60 Gy/1.5 Gy twice daily). Patients were considered being at high risk if tumour malignancy grade was high and the tumour fulfilled at least two of the following criteria: size >8 cm, presence of necrosis or vascular invasion. The mean age of the patients was 50.7 years. With a median follow-up of 5.4 years for survivors, the local control rate was 81.4%. Six (7%) patients progressed during neoadjuvant CRT. Seven (8%) patients discontinued the treatment due to toxicity. Eighty-six patients were operated and three (3%) of these developed a long-term complication. The estimated metastasis-free survival was 47.6% and overall survival 53.0% at five years. The limb-salvage rate was 93%. The limb-salvage rate, local control and complication rates were good in these patients with high risk soft tissue sarcoma. Metastases-free survival and overall survival rates were less satisfactory, reflecting the aggressive nature of these tumours.

Impact of tumor volume doubling time on post-metastatic survival in bone or soft-tissue sarcoma patients treated with metastasectomy and/or radiofrequency ablation of the lung

Metastasectomy represents the standard treatment for improving survival in patients with lung metastases (LMs) from bone (BS) or soft-tissue sarcoma (STS). Recently, radiofrequency ablation (RFA) of the LMs has been proved to be a useful option which can promise the similar effect to metastasectomy. The aim of this study was to determine prognostic factors, including tumor volume doubling time (TVDT), for post-metastatic survival in BS and STS patients treated with metastasectomy and/or RFA of the lung. Forty-eight patients with LMs were retrospectively reviewed. The mean age of the patients at the time of LMs was 56 years. The cohort comprised 27 male and 21 female patients. Eight of the 48 patients had LMs at the point of initial presentation. The mean follow-up period after commencing the treatment for LMs was 37 months. The mean maximum diameter of the initial LMs was 11 mm. The mean number of LMs was 4. The TVDT was calculated using a method originally described by Schwartz. At last follow-up, 5 patients had no evidence of disease, 3 patients were still alive with disease, and 32 patients had died of disease. The 3-year and 5-year post-metastatic survival rates were 32% and 16.8%, respectively. In a Cox univariate analysis, the size (P=0.04) and number of LMs (P<0.001), disease-free interval (P=0.04), curability of the initial LMs (P<0.001), and TVDT (P<0.001) were significantly identified as factors which affect prognosis. In the multivariate analysis, TVDT (P<0.001) and curability of the initial LMs (P<0.001) were confirmed as independent predictors of survival. There was a significant association between the number and curability of the initial LMs (P<0.001). In conclusion, metastasectomy and/or RFA of LMs is recommended for improving survival. However, TVDT and the curability of the LMs should be taken into consideration.

Oligometastasis as a predictor for occult disease

Oligometastasis can be defined as a state of limited metastases that is potentially amenable to ablative local therapy; the success of such therapy depends on whether or not additional occult metastases exist. A model is presented here to predict occult metastases given detectable oligometastases. Predictions were based on Bayes' theorem, in conjunction with descriptions of the statistical distributions for the sizes and numbers of hematogenous metastases. The background probability for occult metastases in individuals with oligometastases increased markedly with relatively minor increases in metastatic potential. With each additional metastasis detected the chance of further occult metastases increased. These latter increases were incremental and proportionately smaller with the more metastatic tumors. Long disease free intervals had a major effect to decrease in the probability of further occult disease. Demonstration of oligometastases depends heavily upon the sensitivity of radiological imaging techniques, where the proportion of detectable metastases relates to the position of the distribution of metastasis growth times with respect to the detection threshold. Given the limitations of radiological methods, and the possibility that the oligometastases detected may be the only disease, an aggressive approach appears indicated.

Clinical impact of the tumor volume doubling time on sarcoma patients with lung metastases

The volume doubling time (VDT) is an accurate and reproducible method for the quantitation of the rate and pattern of tumor growth in individual patients. The purpose of this study is to investigate the tumor VDT using chest CT in individual sarcoma patients with lung metastasis and to determine whether VDT is associated with survival after lung metastasis in bone and soft tissue sarcomas. Forty patients had measurable lung metastases in at least two sequential chest CT images taken at least 14 days apart. The VDT was calculated using the method originally described by Schwartz. The median and mean VDT in all 40 patients was 21.5 and 53 days, respectively. Similarly, the median and average VDT in 29 soft tissue sarcoma patients was 26 and 57 days, respectively. The median and mean VDT in 11 bone sarcoma patients was 13 and 42 days, respectively. The current univariate analysis revealed significantly poorer predictive values for VDT in all 40 sarcoma patients and 29 soft tissue sarcoma patients. A multivariate analysis showed the VDT to be an independent predictor of survival in 29 soft tissue sarcoma patients. These results suggest that patients with a shorter VDT and consequently a more rapid rate of tumor growth have a significantly lower chance for long term survival especially in soft tissue sarcoma. The patients with lung metastasis that have a longer VDT should therefore be considered for aggressive treatment even if the lesions are multiple and/or bilateral.

Lung lesion doubling times: values and variability based on method of volume determination

PURPOSE

To determine doubling times (DTs) of lung lesions based on volumetric measurements from thin-section CT imaging.

METHODS

Previously untreated patients with > or = two thin-section CT scans showing a focal lung lesion were identified. Lesion volumes were derived using direct volume measurements and volume calculations based on lesion area and diameter. Growth rates (GRs) were compared by tissue diagnosis and measurement technique.

RESULTS

54 lesions were evaluated including 8 benign lesions, 10 metastases, 3 lymphomas, 15 adenocarcinomas, 11 squamous carcinomas, and 7 miscellaneous lung cancers. Using direct volume measurements, median DTs were 453, 111, 15, 181, 139 and 137 days, respectively. Lung cancer DTs ranged from 23-2239 days. There were no significant differences in GRs among the different lesion types. There was considerable variability among GRs using different volume determination methods.

CONCLUSIONS

Lung cancer doubling times showed a substantial range, and different volume determination methods gave considerably different DTs.

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.

Pulmonary metastases tumor doubling time: assessment by computed tomography

Growth rate is a prognostic factor for pulmonary metastases treatment. We used computed tomography (CT) to quantify tumor doubling time (Tdt) variation of pulmonary metastases in the same patient, from different histologies and sizes. We prospectively evaluated chest CTs of patients with pulmonary metastases under no cancer treatment. Tdt of 408 pulmonary nodules in 21 patients was determined. One hundred twenty-three (30%) remained unaltered, 44 (11%) had reduction, and 241 (59%) increased in size. Nodules that grew presented a mean Tdt of 118 +/- 134 days (range: 22-930 days). There was high intraindividual variability of mean Tdt with no difference between histologies. Smaller nodules presented greater tendency to grow, and lower Tdt. There is large variation in clinical behavior for pulmonary metastases in the same patient. Each nodule should be evaluated independently. Selection of a single nodule to evaluate metastatic disease behavior could influence the therapeutic decision.

Volumetric growth rate of stage I lung cancer prior to treatment: serial CT scanning

PURPOSE

To determine the range of growth rates of stage I lung cancers prior to treatment by using volumetric measurement at serial chest computed tomographic (CT) examinations.

MATERIALS AND METHODS

The study population comprised 50 patients who underwent two CT examinations at 25-day or greater intervals. Tumor craniocaudal length and cross-sectional diameters and perimeters were used to volumetrically model each tumor in three ways (spherical, elliptical, perimeter). Volumes were compared by determining Pearson correlation coefficients. By using these volumes, tumor doubling time was determined for each patient.

RESULTS

Volumes measured with all three methods were highly correlated. With the perimeter method, median doubling time was 181 days, with a very wide range. Eleven (22%) of 50 tumors had doubling times of 465 days or more. There was considerable overlap in doubling time between histologic subtypes. Assuming constant growth, only three (6%) of the 50 tumors would have been the size of a stage IA tumor for less than 1 year.

CONCLUSION

Comparison of tumor volumes at serial CT examinations reveals a very wide range of growth rates. Some tumors grow so slowly that biopsy is required to prove they are malignant.

The size distribution of human hematogenous metastases

The development of primary cancers and their subsequent metastases occur through a complex sequence of discrete steps. A hypothesis is proposed here whereby the time available for the growth of metastases is normally distributed, presumably as a consequence of the summation of multiple independently distributed time intervals from each of the steps and of the Central Limit Theorem. For exponentially growing metastases, the corresponding size distribution would be lognormal; Gompertzian growth would imply a modified (Gompertz-normal) distribution, where larger metastases would occur less frequently as a consequence of a decreased growth rate. These two size distributions were evaluated against 18 human autopsy cases where precise size measurements had been collected from over 3900 macroscopic hematogenous organ metastases. The lognormal distribution provided an approximate agreement. Its main deficiency was a tendency to over-represent metastases greater than 10 mm diameter. The Gompertz-normal distribution provided more stringent agreement, correcting for this over-representation. These observations supported the hypothesis of normally distributed growth times, and qualified the utility of the lognormal and Gompertz-normal distributions for the size distribution of metastases.

Does surgical removal of primary melanoma trigger growth of occult metastases? An analytical epidemiological approach

BACKGROUND

In several human tumor systems a potential role of surgical removal of the primary tumor upon metastatic tumor growth has been evaluated, as it has been in experimental models. The present study addresses the question of whether the removal of primary melanomas disinhibits growth of metastatic disease and results in more rapid progression.

METHODS

In a data set of 1224 primary cutaneous melanomas the risk of "thin" melanomas to develop metastases within 1 year was compared with the risk of matched pairs of "thick" melanomas to present metastases at the time of diagnosis. For this purpose, a pairwise matching procedure based on certain assumptions as to tumor volume and tumor doubling time has been applied.

RESULTS

When a long tumor doubling time is assumed (200, 400, or 800 days), the tumors removed seem to have a significantly higher risk of metastases to become clinically apparent within 1 year than the matched pairs of tumors to present metastatic disease at the time of diagnosis (chi-square < 0.01). When short tumor doubling time is assumed (50 or 100 days), the difference is not significant, but there also seems to be no benefit for the operated patients.

CONCLUSION

In the present data set there is evidence that surgery of primary melanoma may enhance tumor growth at metastatic sites.

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.

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%).