This study compares two standard radiotherapy approaches (short-course vs. long-course) given before surgery in patients with locally advanced rectal cancer. The goal is to see which treatment is more effective and better tolerated.

The SHOOL study is a single-institution, open-label, randomized prospective study designed to evaluate and compare two internationally accepted total neoadjuvant therapy (TNT) strategies in patients with locally advanced rectal cancer (LARC). These strategies differ primarily in their radiotherapy schedule and include:

Arm A: Short-course radiotherapy (SCRT; 25 Gy in 5 fractions over 1 week), followed by consolidation chemotherapy and surgery

Arm B: Long-course chemoradiotherapy (LCRT; 50.4 Gy in 28 fractions with concurrent Capecitabine over 5-5.5 weeks), followed by consolidation chemotherapy and surgery The study acronym "SHOOL" reflects the clinical dilemma of whether SHOrt-course Or Long-course radiotherapy offers better or more practical outcomes when delivered within a TNT framework.

This prospective study aims to explore how these two strategies compare in terms of tumour response (as measured by pathological complete response, pCR), toxicity, treatment compliance, feasibility, quality of life, and local recurrence rates at 3 and 5 years. Given that both arms represent evolving standards of care, this study is designed to generate real-world data that can guide institutional decision-making and inform future definitive trials.

Inclusion Criteria:

1. Histologically confirmed adenocarcinoma of the rectum
2. Locally advanced disease based on MRI including cT3-T4 and/or node positive disease (cN1 or N2)
3. Tumor located within 15 cm from the anal verge (confirmed by endoscopy or MRI)
4. ECOG performance status 0-2
5. Hemoglobin ≥ 9 g/dL
6. Absolute neutrophil count ≥ 1,500/mm³
7. Platelets ≥ 100,000/mm³
8. Total bilirubin ≤ 1.5 × ULN
9. Aspartate transaminase/Alanine transaminase ≤ 2.5 × ULN
10. Serum creatinine ≤ 1.5 × ULN or creatinine clearance ≥ 60 mL/min
11. Fit for neoadjuvant therapy and curative resection
12. Willing and able to provide written, informed consent
13. Baseline MRI and biopsy (even if done outside) must be reviewed and approved by the institutional radiology and pathology review board, requiring concurrence from two independent pathologists and two independent radiologists

Exclusion Criteria:

1. Metastatic disease at presentation (distant nodes, liver, lung, peritoneum, etc.)
2. Prior pelvic radiotherapy or systemic chemotherapy for rectal cancer
3. Presence of synchronous malignancies or previous malignancy within 5 years except: Treated basal cell or squamous cell carcinoma of the skin, In situ cervical cancer, Active uncontrolled infection
4. Known HIV infection with CD4 < 200 cells/μL, or active hepatitis B or C
5. Severe comorbid conditions precluding therapy (e.g., decompensated cardiac, hepatic, or renal disease)
6. Pregnant or breastfeeding women
7. Inability to comply with protocol requirements or follow-up schedule
8. Psychiatric illness or social situations that may limit compliance with study requirements

De-identified data sets will include participant demographics, baseline measures, intervention details, clinical outcomes, and adverse events recorded during the study.

IPD and supporting information will be available beginning six months after publication of the primary results or completion of the study, whichever is later. Data will remain accessible for five years from the start date of availability.

Qualified researchers who submit a methodologically sound research proposal will be able to access de-identified individual participant data underlying the main results, as well as supporting documents such as the study protocol and statistical analysis plan. Access will be granted through a secure data sharing portal, subject to data use agreements that ensure participant confidentiality and limit use to the specified research purpose