Villejuif, 12 March 2026

Colorectal cancer awareness month: from organoids to surgery, Gustave Roussy at the forefront of advances in colorectal cancers

Colorectal tumours are among the most common cancers in France, with approximately 47,500 cases diagnosed each year, making it the second most common cancer in women and the third in men, according to figures from the French National Cancer Institute. Gustave Roussy, through its digestive oncology committee and various research laboratories, is a leading institution in the fight against and research into colorectal cancers.

In most cases, colorectal cancers develop from a polyp, an initially benign lesion of the mucous membrane of the colon or rectum, which can gradually progress into a malignant tumour in the absence of screening and treatment. When detected at an early (localised) stage, this condition has a five-year survival rate of over 90%. However, low participation in the national screening programme and the absence of symptoms in the early stages of the disease delay diagnosis in many cases. Colorectal cancer, therefore, remains the third leading cause of cancer-related death in France, in both men and women.

To cure a growing number of patients, Gustave Roussy is involved in numerous research projects and clinical initiatives, all dedicated to curing more patients, more effectively. From the development of colon organoids, miniature tumour replicas used to test treatments in advance, to the performance of day-case colectomies, the Institute's teams are mobilised daily to challenge an ever-greater number of prognoses.

Organoids

The research team led by Fanny Jaulin at Gustave Roussy specialises in the biological modelling of colorectal cancers. This work is based on the use of organoids: tumour replicas cultivated in the laboratory from tumour cells taken directly from the patient, generally by biopsy. The tumour cells are then multiplied in the laboratory to create a tumour avatar specific to each patient.

These organoids are used to understand the mechanisms by which cancer cells invade surrounding tissue and their capacity to spread throughout the body to form metastases, the leading cause of cancer-related death. These avatars are also used to test the efficacy of different treatments in advance, to identify the most effective option for each patient. Researchers are not limited to standard treatments validated for colorectal cancer; they also extend their research to drugs used in other cancers, to determine whether they may prove effective for a given patient. This personalised medicine approach helps to tailor treatment to the unique biology of each tumour.

All these research initiatives are carried out within the RHU (Hospital-University Research) Organomic project, funded by the French National Research Agency. The first phase of this project has been completed successfully: it demonstrated the feasibility of the method within a clinical setting, meaning that the results of organoid tests can be transmitted to clinicians early enough to influence therapeutic decision-making. Of the 54 patients who benefited from this approach, 21% experienced clinical benefit following the use of organoids, despite having reached a therapeutic impasse. The second phase, currently underway, aims to extend the project to a broader population (150 patients), including people with colon or pancreatic cancer, to increase the reach and clinical benefits of organoids.

Day-case colectomy

A colectomy is a surgical procedure consisting of removing the portion of the colon affected by a tumour, to eliminate the colorectal cancer and prevent its progression. It is indicated for patients whose disease is localised and can be treated effectively through surgery.

One year ago, Gustave Roussy launched a day-case colectomy pathway — whereby the patient arrives in the morning and is discharged the same evening — demonstrating the Institute's capacity to offer innovative, safer, and less invasive surgical care for people with cancer. Post-surgical follow-up at home required the development of a dedicated application, featuring daily questionnaires completed by patients over five days (covering pain levels, diet, return of bowel function, and so on), along with dedicated nursing staff available to respond to any issues flagged through the application. These questionnaires are accompanied by two blood tests, taken one day and three days after the operation.

This pathway has been deemed safe. No significant increase in complications has been observed compared with conventional hospitalisation, and the timelines for managing any complications are comparable. Several benefits have been noted for patients, including faster recovery, reduced pain, and a positive psychological impact. This approach is not currently available to all patients: those with significant obesity or a high risk of complications are, for example, not eligible.

Also, in the field of surgery, Gustave Roussy acquired the da Vinci Single Port robotic surgery system in March 2025, which enables surgical procedures, including colectomies, to be performed through a single incision of 3 to 4 centimetres. This robot offers a minimally invasive approach, potentially associated with reduced post-operative pain. The Institute is among the first French centres to have acquired significant experience in "Single Port" colectomy.

Contact radiotherapy

The radiotherapy department at Gustave Roussy is equipped with the Papillon+ contact radiotherapy device. In patients presenting with a small rectal tumour, this device makes it possible to limit recourse to major, invasive surgery that might otherwise require the creation of a stoma.

Combined with chemoradiotherapy, contact radiotherapy is associated with a rectal preservation rate of up to 97% in patients with a tumour of three centimetres or less. By comparison, with the standard approach, chemoradiotherapy followed by external radiotherapy, this rate stands at approximately 63% in the same population, according to data from the OPERA study[1] after three years of follow-up.

To extend the application of contact radiotherapy to other rectal cancers, a randomised phase III clinical trial is currently underway at Gustave Roussy and other French centres. Entitled TRESOR, it is aimed at patients presenting with a rectal tumour measuring between 3.5 and 6 cm. The objective is to demonstrate the value of this approach in preserving the rectum in a larger patient population, with a view to expanding access to contact radiotherapy.