Role of Short-Course Radiotherapy in Rectal Cancer

Primary Indications and Technical Specifications

The European Society for Medical Oncology recommends short-course radiotherapy as a highly effective, convenient, and low-toxicity preoperative treatment option for locally advanced rectal cancer, reducing local recurrence rates, and should be followed by surgery within 1 week for immediate surgery or delayed 6-8 weeks for tumor downstaging 1, 2, 3
Short-course radiotherapy is specifically recommended for intermediate-risk rectal cancers, including most cT3 tumors without threatened mesorectal fascia, some cT4a tumors, N+ disease, and very low cT2 tumors where distance to mesorectal fascia is small 1, 2, 3
The Chinese guidelines specify that T3 tumors staged by endorectal ultrasound or MRI without requirement for sphincter preservation may receive short-course radiotherapy followed by surgery within 1 week 4
Short-course radiotherapy is also recommended for patients requiring rapid treatment, with a 1-week treatment schedule followed by immediate surgery, offering convenience and efficiency compared to 5-6 weeks of long-course chemoradiotherapy 1, 3
For elderly or medically unfit patients, 5×5 Gy with delayed surgery (8 weeks) is an appropriate alternative 1, 3

Short-course radiotherapy has advantages over long-course chemoradiotherapy, including being more convenient, simpler logistics, and proven equivalent local control when followed by immediate surgery 1, 2, 3
Long-course chemoradiotherapy is preferred for most locally advanced/non-resectable cases, delivering 45-50.4 Gy with concurrent 5-FU-based chemotherapy 1, 2, 3

The technical specifications for short-course radiotherapy include a dose of 25 Gy total, delivered as 5 Gy per fraction over 5 consecutive days, with a target volume that includes the tumor/tumor bed with a 2-5 cm margin, presacral lymph nodes, internal iliac lymph nodes, and obturator lymph nodes 1, 2, 3, 4
Short-course radiotherapy should not be used for very early tumors that require surgery alone, most locally advanced non-resectable cases, or patients requiring maximal tumor downstaging for organ preservation 1, 2, 3, 5

Preoperative treatment is always preferred over postoperative treatment due to superior efficacy and reduced toxicity 1, 2, 3, 6
Total mesorectal excision (TME) surgery is mandatory following radiotherapy to achieve optimal local control 1, 2, 3, 6

Deliver a total of 25 Gy in five consecutive daily fractions of 5 Gy each, without concurrent chemotherapy, for patients with resectable locally advanced disease 7.

Perform total mesorectal excision (TME) within 10 days (ideally 3–5 days) after the first radiation fraction to achieve rapid treatment completion and excellent local control 7.
For elderly (≥80 years) or medically unfit patients who cannot tolerate chemoradiotherapy, postpone surgery for 6–8 weeks after radiotherapy to allow tumor down‑staging comparable to long‑course regimens 7.

Indicated for intermediate‑risk tumors (cT3 without threatened mesorectal fascia on MRI), selected cT4a tumors with limited vaginal or peritoneal involvement, node‑positive (N+) disease within the intermediate‑risk group, and very low cT2 tumors where the distance to the mesorectal fascia is short 7.
Not recommended for most locally advanced or non‑resectable cases (cT3 with threatened/involved mesorectal fascia, cT4 with extensive organ involvement), patients requiring maximal down‑staging for sphincter preservation, or very early tumors (cT1‑2, N0) that can be treated with surgery alone 7.

Mandatory use of a high‑quality TME technique after any short‑course radiotherapy 7.
Aim for at least a 5 cm distal margin on the unfixed specimen and preserve the integrity of the mesorectal fascia to minimize local recurrence 7.
For low‑lying tumors requiring abdominoperineal excision, modify the technique to avoid a cone‑shaped resection that raises the risk of a positive circumferential resection margin 7.

Pre‑operative short‑course radiotherapy provides comparable local control with minimal toxicity when surgery is performed promptly 7.
Evidence indicates that pre‑operative short‑course radiotherapy may carry a higher 5‑year locoregional failure rate (≈10 %) than long‑course chemoradiotherapy (≈6 %) in settings where optimal local control is critical 7.

When short‑course radiotherapy is unsuitable, employ 45–50.4 Gy in 1.8–2 Gy fractions combined with 5‑FU‑based chemotherapy, followed by surgery 6–8 weeks later; this regimen yields superior tumor down‑staging and improved local control in high‑risk patients 7.