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