Multidimensional Study Designed to Develop a Methodological Framework Based on MRI Data to Predict Pathological Complete Response (pCR) in Patients With Locally Advanced Rectal Cancer After Neoadjuvant Treatment

Plain-language summary

Rectal cancer presents a significant global health challenge. Despite improvements in clinical outcomes, significant disparities persist across Europe. These differences are explained not only by the heterogeneity of risk factors and screening strategies, but also by variations in diagnostic and therapeutic approaches, which are highly dependent on medical imaging. Standard treatment for locally advanced rectal cancer based on staging MRI is neoadjuvant treatment (NAT), for tumour downsizing and downstaging, followed by total mesorectal excision. In a significant proportion of cases, radical surgery leads to substantial long-term complications like sexual and urinary dysfunction, fecal incontinence, and impairment in daily activities. Given that up to 42% of patients show complete tumor regression at pathology (i.e. pathological complete response pCR), to avoid unnecessary radical surgery, non-operative management has become an attractive alternative when there are no signs of viable tumour after NAT (i.e. clinical complete response cCR). Such patients are candidates for Watch-and-Wait (W\&W), an established active surveillance policy in specialized centers worldwide relying on clinical examination, endoscopy and MRI. On the other hand, W\&W carries a risk of local regrowth (persistence of microscopic residual disease despite apparent cCR). Even in expert hands, assessment of tumor response is not perfect and local regrowth based on current selection methods occurs in \~30% of cases. Although deferred surgery is a successful treatment with no apparent negative impact on local disease control, an increased rate of distant metastases has been recently reported. Therefore, there is a critical unmet clinical need to detect complete responses after NAT and avoid unnecessary surgery with its associated morbidity and quality of life impairment risks, while also improving sensitivity for residual microscopic disease that will result in local regrowth and associated reduced disease-free survival. Rectal cancer poses a burden not only on healthcare systems, but also on patient well-being. Patients frequently suffer from feelings of isolation and helplessness when faced with unpredicted disease-related situations, given the common difficulties to access high quality information and communicate with attending physicians. As such, there is a clear need to unburden healthcare facilities from unnecessary hospital visits, while improving patient outcomes, engagement, support and care.

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