107P - Tumor-stromal ratio in a new age fibroblast activated protein PET imaging as a biomarker for prediction of response to neoadjuvant chemoradiotherapy in carcinoma rectum

Background

Tumor stroma consists of a complex network of safeguards for tumor proliferation. Tumour stromal imaging using fibroblast-activated protein-tagged radionuclide provides a metabolic-radiological quantum of tumor stromal content. Tumors rich in stroma have been traditionally associated with poorer disease-free outcomes. Our study correlates between standard uptake values (SUV) in fibroblast imaging to tumor stromal ratio evaluated pathologically and the response to radiation therapy in locally advanced carcinoma rectum.

Methods

50 patients of carcinoma Rectum with all patients having undergone cancer associated Fibroblast PET CT scan prior to starting neoadjuvant chemoradiation. Tumors having SUV max > 10 were considered as High. Metabolic activity in tumor site was compared to Tumor stromal ratio and response to radiation was evaluated in histopathological report. Patients were classified into High TSR (<50% Stromal content) and Low Tumor Stroma Ratio (>50% Stromal content).

Results

7 patients who had complete pathological response all had high TSR and SUV mean 20.4. 34 patients had <50% residual disease 67% had high TSR and SUV mean 17.6 and 34% had low TSR and SUV mean of 21.44. 9 patients had >50% residual disease had 77% low TSR and high SUV mean 25.11(Range- 9.51-92.33). Patients with both Low TSR [ >50% stromal content] and SUV Max > 10 have poor pathological response compared to patients with low TSR. In the low stromal content irrespective of SUV the local control was good. Table: 107P

Conclusions

High Tumor Stromal Ratio showed better complete and partial response to neoadjuvant chemoradiation in locally advanced carcinoma rectum. Tumors with high stromal content were observed to have higher SUV values in fibroblast stromal imaging and the same were also more commonly associated with suboptimal response. The need for dose escalation for the same has to be explored for better tumor control.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.