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Radiotherapy

The role of radiotherapy in rectal cancer

Radiotherapy is frequently used in rectal cancer, unlike colon cancer where it is rarely used. The main goal is to shrink the tumor before surgery (neoadjuvant) to facilitate complete surgical resection and reduce the risk of local recurrence.

Neoadjuvant chemoradiotherapy

The standard treatment combines radiotherapy with chemotherapy (5-FU or capecitabine). This combination is more effective than radiotherapy alone in shrinking the tumor.

Long-course schedule (5-6 weeks)

  • Total dose: 45-50.4 Gy in 25-28 fractions
  • Schedule: one session per day, 5 days per week
  • Concurrent chemotherapy: daily oral capecitabine or intravenous 5-FU
  • Interval to surgery: 6-12 weeks (for maximum tumor response)

Short-course schedule (5 days)

  • Total dose: 25 Gy in 5 fractions
  • Schedule: one session per day, 5 consecutive days
  • No concurrent chemotherapy in the classic schedule
  • Variable interval: surgery 1-2 weeks later (Swedish schedule) or 6-8 weeks later (with consolidation chemotherapy)

Main indications

Neoadjuvant chemoradiotherapy is indicated for:

  • Locally advanced rectal cancer (T3-T4 or N+)
  • Mid and lower rectum tumors
  • Situations where shrinking the tumor may allow sphincter preservation
  • A circumferential resection margin (CRM) threatened on MRI

Total Neoadjuvant Therapy (TNT)

TNT is a modern approach in which all chemotherapy and radiotherapy are administered before surgery:

  • Induction chemotherapy (FOLFOX or CAPOX, 3-4 cycles) followed by chemoradiotherapy
  • OR chemoradiotherapy followed by consolidation chemotherapy
  • Total interval before surgery: 4-6 months

Advantages of TNT

  • Higher rate of pathological complete response (the tumor disappears completely)
  • Possibility of organ preservation (Watch & Wait strategy)
  • Better compliance with chemotherapy (administration before surgery is better tolerated)
  • Early systemic treatment of micrometastases

Side effects of pelvic radiotherapy

Acute effects (during and shortly after treatment)

  • Diarrhea and tenesmus — sensation of incomplete evacuation, urgency to defecate
  • Skin irritation in the irradiated area (radiation dermatitis)
  • Fatigue — the most common complaint
  • Radiation cystitis — bladder irritation, frequent urination
  • Nausea — especially when chemotherapy is combined

These effects are usually temporary and improve 2-4 weeks after radiotherapy ends.

Long-term effects

  • Sexual dysfunction — affects both men (erectile dysfunction) and women (vaginal dryness, dyspareunia)
  • Urinary disturbances — incontinence, urgency
  • Pelvic fibrosis — stiffening of pelvic tissues
  • Radiation enteritis — chronic inflammation of the small intestine
  • Sacral insufficiency fractures — rare but possible

Managing side effects

  • Adapted diet — avoid irritating foods (spicy, fatty, high-fiber)
  • Adequate hydration
  • Symptomatic medications — antidiarrheals (loperamide), antiemetics, analgesics
  • Skin care — moisturizing creams, avoid rubbing the irradiated area
  • Psychological support — to manage the emotional impact