The ESTRO Breur Lecture 2010: Toward a tailored patient approach in rectal cancer

Downregulation of CEMIP enhances radiosensitivity by promoting DNA damage and apoptosis in colorectal cancer

Colorectal cancer (CRC) is the third leading malignancy worldwide in both new cases and deaths. Neoadjuvant radiotherapy is the standard preoperative regimens for locally advanced patients. However, approximately 50% of patients develop recurrence and metastasis after radiotherapy, which is largely due to the radiation resistance properties of the tumor, and the internal mechanism has not been elucidated. Here we found that CEMIP expression is up-regulated in a variety of tumor types, particularly in CRC. Public databases and clinical samples revealed that CEMIP expression is significantly higher in tumor tissues than in adjacent normal tissues in patients with locally advanced CRC who received neoadjuvant chemoradiotherapy, and it is closely related to the poor prognosis. Functional characterization uncovered that downregulation of CEMIP expression can enhance the radiosensitivity of CRC cells, which is confirmed to be achieved by promoting DNA damage and apoptosis. In vivo studies further verified that CEMIP knockdown can significantly improve the radiosensitivity of subcutaneously implanted colorectal tumors in mice, suggesting that CEMIP may be a radiation-resistant gene in CRC. Mechanistically, EGFR/PI3K/Akt signaling pathway is hypothesized to play a key role in CEMIP mediating radiation resistance. These results provide a potential new strategy targeting CEMIP gene for the comprehensive treatment of locally advanced CRC patients.

PSP1, a Phosphatidylserine-Recognizing Peptide, Is Useful for Visualizing Radiation-Induced Apoptosis in Colorectal Cancer In Vitro and In Vivo

Accurate and timely visualization of apoptotic status in response to radiation is necessary for deciding whether to continue radiation or change to another mode of treatment. This is especially critical in patients with colorectal cancer, which requires a delicate combination of surgery, radiation, and chemotherapy in order to achieve optimal outcome. In this study, we investigated the potential of phosphatidylserine-recognizing peptide 1 (PSP1) as an apoptosis-targeting probe, which identifies phosphatidylserine on cell surfaces. We first screened colon cancer cell lines for their sensitivity to radiation and selected two cell lines: HCT116 and HT29. Cell binding assay using fluorescence-activated cell sorting and optical imaging showed that HCT116 cells had better binding to PSP1 than HT29 cells. Thus, mouse xenograft model using HCT116 cells was generated and was topically irradiated with either single or fractionated dose of radiation followed by systemic administration of PSP1 for subsequent molecular optical imaging. We confirmed that the PSP1 probe was selectively bound to apoptosis-induced tumor in a radiation dose-dependent manner. We also observed that fractionated radiation regimen, which is recently being used in clinical situation, was more effective in inducing tumor apoptosis than corresponding single-dose radiation treatment. We then evaluated the correlation between tumor targeting of PSP1 and suppression effect of tumor development and found that tumor volume and fluorescence intensity were correlated before (correlation coefficient r² = 0.534) and after (r² = 0.848) radiation therapy. Our study shows that PSP1 peptide is an efficient index probe for deciding "go or no-go" for radiation therapy in colorectal cancer.

Standardized data collection to build prediction models in oncology: a prototype for rectal cancer

The advances in diagnostic and treatment technology are responsible for a remarkable transformation in the internal medicine concept with the establishment of a new idea of personalized medicine. Inter- and intra-patient tumor heterogeneity and the clinical outcome and/or treatment's toxicity's complexity, justify the effort to develop predictive models from decision support systems. However, the number of evaluated variables coming from multiple disciplines: oncology, computer science, bioinformatics, statistics, genomics, imaging, among others could be very large thus making traditional statistical analysis difficult to exploit. Automated data-mining processes and machine learning approaches can be a solution to organize the massive amount of data, trying to unravel important interaction. The purpose of this paper is to describe the strategy to collect and analyze data properly for decision support and introduce the concept of an 'umbrella protocol' within the framework of 'rapid learning healthcare'.

Sustaining Blood Lymphocyte Count during Preoperative Chemoradiotherapy as a Predictive Marker for Pathologic Complete Response in Locally Advanced Rectal Cancer

Purpose

The objective of this study was to explore the relationship between the circulating lymphocyte level during preoperative chemoradiotherapy (CRT) and pathologic complete response (pCR) in locally advanced rectal cancer.

Materials and Methods

From May 2010 to May 2013, 52 patients treated with preoperative CRT followed by surgery, were analysed. Patients received conventional fractionated radiotherapy (50-54 Gy) with fluorouracil-based chemotherapy. Surgical resection was performed at 4 to 8 weeks after the completion of preoperative CRT. Absolute blood lymphocyte counts and their relative percentage in total white blood cell counts were obtained from complete blood count tests performed prior to and after 4, 8, and 12 weeks of CRT. We analysed the association between achieving pCR and change in blood lymphocyte level during CRT, as well as clinical parameters.

Results

Among 52 patients, 14 (26.9%) had evidence of pCR. Sustaining the blood lymphocyte count during CRT (lymphocyte count at 4 weeks/baseline lymphocyte count > 0.35; odds ratio, 8.33; p=0.02) and initial carcinoembryonic antigen < 4.4 ng/mL (odds ratio, 6.71; p=0.03) were significantly associated with pCR in multivariate analyses.

Conclusion

Sustaining blood lymphocyte count during preoperative CRT was predictive for pCR in rectal cancer. Further studies are warranted to investigate the association between pathologic responses and circulating lymphocyte count with its subpopulation during preoperative CRT.

VATE: VAlidation of high TEchnology based on large database analysis by learning machine

SUMMARY 

The interaction between implementation of new technologies and different outcomes can allow a broad range of researches to be expanded. The purpose of this paper is to introduce the VAlidation of high TEchnology based on large database analysis by learning machine (VATE) project that aims to combine new technologies with outcomes related to rectal cancer in terms of tumor control and normal tissue sparing. Using automated computer bots and the knowledge for screening data it is possible to identify the factors that can mostly influence those outcomes. Population-based observational studies resulting from the linkage of different datasets will be conducted in order to develop predictive models that allow physicians to share decision with patients into a wider concept of tailored treatment.

FDG PET/CT for rectal carcinoma radiotherapy treatment planning: comparison of functional volume delineation algorithms and clinical challenges

PET/CT imaging could improve delineation of rectal carcinoma gross tumor volume (GTV) and reduce interobserver variability. The objective of this work was to compare various functional volume delineation algorithms. We enrolled 31 consecutive patients with locally advanced rectal carcinoma. The FDG PET/CT and the high dose CT (CTRT) were performed in the radiation treatment position. For each patient, the anatomical GTVRT was delineated based on the CTRT and compared to six different functional/metabolic GTVPET derived from two automatic segmentation approaches (FLAB and a gradient-based method); a relative threshold (45% of the SUVmax) and an absolute threshold (SUV &gt; 2.5), using two different commercially available software (Philips EBW4 and Segami OASIS). The spatial sizes and shapes of all volumes were compared using the conformity index (CI). All the delineated metabolic tumor volumes (MTVs) were significantly different. The MTVs were as follows (mean ± SD): GTVRT (40.6 ± 31.28ml); FLAB (21.36± 16.34 ml); the gradient-based method (18.97± 16.83ml); OASIS 45% (15.89 ± 12.68 ml); Philips 45% (14.52 ± 10.91 ml); OASIS 2.5 (41.6 2 ± 33.26 ml); Philips 2.5 (40 ± 31.27 ml). CI between these various volumes ranged from 0.40 to 0.90. The mean CI between the different MTVs and the GTVCT was &lt; 0.4. Finally, the DICOM transfer of MTVs led to additional volume variations. In conclusion, we observed large and statistically significant variations in tumor volume delineation according to the segmentation algorithms and the software products. The manipulation of PET/CT images and MTVs, such as the DICOM transfer to the Radiation Oncology Department, induced additional volume variations.

Identification of a microRNA expression signature for chemoradiosensitivity of colorectal cancer cells, involving miRNAs-320a, -224, -132 and let7g

BACKGROUND AND PURPOSE

Preoperative chemoradiotherapy (CRT) represents the standard treatment for locally advanced rectal cancer. Tumor response and progression vary considerably. MicroRNAs represent master regulators of gene expression, and may therefore contribute to this diversity.

MATERIAL AND METHODS

Genome-wide microRNA (miRNA) profiling was performed for 12 colorectal cancer (CRC) cell lines and an individual in vitro signature of chemoradiosensitivity was established. Functional relevance of selected miRNAs was established by transfecting miRNA-mimics into SW480 and SW837 cells. The prognostic value of selected miRNAs was assessed in 128 pretherapeutic patient biopsies.

RESULTS

Thirty-six miRNAs were identified to significantly correlate with sensitivity to CRT (Q < 0.05) including miR-320a and other miRNAs involved in the MAPK-, TGF- and Wnt-pathway. Transfection of selected miRNAs (let-7g, miR-132, miR-224, miR-320a) each induced a shift of sensitivity. High expression of let-7 g was associated with a good prognosis in rectal cancer patients (P = 0.03).

CONCLUSIONS

This is the first report of a miRNA expression signature for in vitro chemoradiosensitivity of CRC cell lines. Many of the identified miRNAs have not been linked to the response to CRT and may represent potential molecular targets to sensitize resistant cancers. If further validated, let7g expression may serve as predictive biomarker.

Early prediction of pathological response in locally advanced rectal cancer based on sequential 18F-FDG PET

BACKGROUND

The objectives of this study were to investigate the predictive value of sequential (18)F-FDG PET scans for pathological tumor response grade (TRG) after preoperative chemoradiotherapy (PCRT) in locally advanced rectal cancer (LARC) and the impact of partial volume effects correction (PVC).

METHODS

Twenty-eight LARC patients were included. Responders and non-responders status were determined in histopathology. PET indices [SUV max and mean, volume and total lesion glycolysis (TLG)] at baseline and their evolution after one and two weeks of PCRT were extracted by delineation of the PET images, with or without PVC. Their predictive value was investigated using Mann-Whitney-U tests and ROC analysis.

RESULTS

Within baseline parameters, only SUVmean was correlated with response. No evolution after one week was predictive of the response, whereas after two weeks all the parameters except volume were, the best prediction being obtained with TLG (AUC 0.79, sensitivity 63%, specificity 92%). PVC had no significant impact on these results.

CONCLUSION

Several PET indices at baseline and their evolution after two weeks of PCRT are good predictors of response in LARC, with or without PVC, whereas results after one week are suboptimal. Best predictor was TLG reduction after two weeks, although baseline SUVmean had smaller but similar predictive power.

Radiation dose-response model for locally advanced rectal cancer after preoperative chemoradiation therapy

PURPOSE

Preoperative chemoradiation therapy (CRT) is part of the standard treatment of locally advanced rectal cancers. Tumor regression at the time of operation is desirable, but not much is known about the relationship between radiation dose and tumor regression. In the present study we estimated radiation dose-response curves for various grades of tumor regression after preoperative CRT.

METHODS AND MATERIALS

A total of 222 patients, treated with consistent chemotherapy and radiation therapy techniques, were considered for the analysis. Radiation therapy consisted of a combination of external-beam radiation therapy and brachytherapy. Response at the time of operation was evaluated from the histopathologic specimen and graded on a 5-point scale (TRG1-5). The probability of achieving complete, major, and partial response was analyzed by ordinal logistic regression, and the effect of including clinical parameters in the model was examined. The radiation dose-response relationship for a specific grade of histopathologic tumor regression was parameterized in terms of the dose required for 50% response, D50,i, and the normalized dose-response gradient, γ50,i.

RESULTS

A highly significant dose-response relationship was found (P=.002). For complete response (TRG1), the dose-response parameters were D50,TRG1=92.0 Gy (95% confidence interval [CI] 79.3-144.9 Gy), γ50,TRG1=0.982 (CI 0.533-1.429), and for major response (TRG1-2) D50,TRG1&2=72.1 Gy (CI 65.3-94.0 Gy), γ50,TRG1&2=0.770 (CI 0.338-1.201). Tumor size and N category both had a significant effect on the dose-response relationships.

CONCLUSIONS

This study demonstrated a significant dose-response relationship for tumor regression after preoperative CRT for locally advanced rectal cancer for tumor dose levels in the range of 50.4-70 Gy, which is higher than the dose range usually considered.

Prediction in rectal cancer

The treatment of rectal cancer largely depends on disease stage at diagnosis, based on which patients can be classified as low, intermediate, or high risk. Prognostic and predictive markers, specific to each risk category, can be applied for optimal risk classification and subsequent treatment allocation. These markers are either histopathological, determined with imaging, or have a biomolecular background. This review provides an overview of the current status of treatment options and the use of prognostic and predictive markers in each risk category. An effort was made to identify those markers that are currently lacking in, but have the potential to improve, the clinical decision process by discussing the data from recent studies aimed at the development of new prognostic and predictive markers. At this moment, none of the markers studied has been proven to be of significant, independent value, justifying implementation in daily clinical practice. However, recent developments in imaging techniques and biomolecular research do show great potential.

Circulating regulatory T cells of cancer patients receiving radiochemotherapy may be useful to individualize cancer treatment

BACKGROUND AND PURPOSE

Dendritic cells (DCs) and regulatory T cells (Treg) play a major role in anti-tumor immune response of cancer patients. We investigated the effect of radiochemotherapy on patients' blood immune cells and their predictive value for tumor response.

MATERIALS AND METHODS

DCs and Treg of colorectal cancer (CRC) or breast cancer (BC) patients were examined through multicolor flow cytometry before the beginning and after the first week of radiochemotherapy (RCT). DCs were stained for BDCA1 and BDCA2, Treg were stained for CD4, CD25, CD127 and FoxP3. IL-2, IL-10 and TNF-α plasma levels of CRC patients were also determined. We examined the interrelationship between immune cell count alterations, applied dose values, cytokine plasma levels as well as histopathological parameters.

RESULTS

DCs were increased in BC and CRC patients compared to healthy control individuals (HC). CRC patients had higher levels of Treg (59.0%) compared to BC patients (31.3%) and HC (27.0%). Treg of CRC (58.7% vs. 41.3% p<0.001) but not BC patients (31.3% vs. 38.8%, p=0.164) decreased distinctly after the first week of radiation therapy. Applied dose values and decrease of Treg correlated positively (r=0.216, p=0.054). We also found a positive correlation of IL-10 plasma levels and Treg levels (r=0.748, p=0.021). CRC patients with favorable tumor stage (<ypT3a) have higher levels of Treg after 5 days of RCT (49.4% vs. 34.0%, p=0.043).

CONCLUSION

Higher Treg levels are associated with favorable tumor stage. We hypothesize that a dramatic decrease of Treg after in vivo irradiation may be a good indicator for necessary dose adjustments in radiation therapy of CRC patients.

Response prediction in the multimodality therapy of locally advanced rectal cancer

SUMMARY Neoadjuvant therapies have been established in the multimodality treatment of locally advanced rectal cancer. Radiation with concurrent 5-fluorouracil-based chemotherapy followed by surgical resection is considered to be the standard of care in advanced rectal cancer. However, recent studies revealed that patients with complete histopathologic response seem to benefit most from neoadjuvant therapies. Consequently, predictive markers to allow individualization of multimodality therapy in locally advanced rectal cancer are mostly required to identify those who will benefit the most. Unfortunately, there is still an immense lack of factors for response assessment in patients with rectal cancer undergoing multimodality treatment. While conventional diagnostic tools lack sufficient accuracy to provide information for response assessment, newer techniques such as [18F]-fluorodeoxyglucose-PET and diffusion-weighted MRI show promising results. In addition, studies on molecular factors for response assessment in rectal cancer are encouraging but still do not provide a reliable instrument for utilization in clinical practice.