colorectal%20cancer
COLORECTAL CANCER
Colorectal cancer is a carcinoma arising from the luminal surface of the colon.
It is the 2nd most common cancer in women and third most common cancer in male worldwide. It commonly arises from adenomatous polyps.
It is strongly linked to age with 83% occurring in people ≥60 years old.
Rectal cancer is defined as cancerous lesions located within 12 cm of the anal verge.

Radiotherapy

Resectable Nonmetastatic Rectal Cancer

  • Associated with decreased rates of local recurrence for rectal cancer
  • Administration should include the tumor bed with 2 to 5-cm margin, mesorectum, internal iliac nodes and presacral nodes
    • External iliac nodes are included in T4 tumors involving anterior structures 
  • Risks include increased hematologic toxicities, radiation-induced injury

Preoperative versus Postoperative Radiation Therapy

  • Preoperative radiation therapy (along with chemotherapy) is recommended for those with stage II and III rectal cancer
    • Short-course RT may be an option for patients with T3N0 or T1-3N1-2 rectal CA
  • Advantages of preoperative radiation therapy include:
    • Increased rate of sphincter preservation
    • Increased sensitivity to radiation therapy of surgically-naive tissues
    • Avoiding radiation-induced injury that can arise from post-surgical adhesions
    • Increases the likelihood that an anastomosis with a healthy colon can be done
  • Disadvantage of preoperative radiation therapy is the possibility of overtreating early-stage tumors that do not require radiotherapy
  • Postoperative radiation therapy is recommended when stage I rectal cancer has been upstaged to stage II or III after pathologic review of the surgical specimen

Intraoperative Radiotherapy (IORT)

  • For patients with T4 tumors or recurrent cancers, or if margins are positive or very close
  • Involves direct exposures of tumors to radiation therapy intraoperatively while normal structures are removed from the field of treatment
  • Considered as an additional boost to facilitate surgery
  • If unavailable, brachytherapy and/or 10-120 Gy of radiation may be considered soon after resection, prior to adjuvant chemotherapy

Metastatic Colorectal Cancer

Arterial Radioembolization

  • While toxicity is relatively low, evidence supporting its use is still lacking
  • Alternative for highly-selected patients with predominantly hepatic metastases and with chemotherapy-resistant or refractory disease

External Beam Radiation Therapy (EBRT)

  • May be considered in highly selected cases where patients have limited number of liver or lung metastases or in symptomatic patients or in the setting of a clinical trial
  • Should not replace surgical resection
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