Would you recommend radiation therapy for an invasive adenocarcinoma of the sigmoid colon, moderately differentiated, 6cm in size, invading through the muscularis propria into pericolorectal tissue, with perineural and lymphovascular invasion, and 2 positive lymph nodes?

Radiation Therapy for Sigmoid Colon Adenocarcinoma with Lymph Node Involvement

Radiation therapy is not recommended for this case of sigmoid colon adenocarcinoma with lymph node involvement (pT3N1) as adjuvant chemotherapy alone is the standard of care.

Tumor Characteristics and Staging

• The patient has an invasive adenocarcinoma of the sigmoid colon, moderately differentiated, 6cm in size, with invasion through the muscularis propria into pericolorectal tissue (pT3) 1
• Perineural and lymphovascular invasion are present, which are high-risk features 1
• 2 lymph nodes are positive for carcinoma (N1) 1
• All resection margins are negative for carcinoma 1
• This represents a stage IIIA (pT3N1) colon cancer 1

Standard Treatment Recommendations

• For node-positive colon cancer (T1-3, N1-2, M0), adjuvant chemotherapy is the standard of care 1
• FOLFOX (preferred) or other options including FLOX, CapeOx, capecitabine, or 5-FU/leucovorin are recommended adjuvant regimens 1
• Radiation therapy is not routinely recommended for colon cancer, unlike rectal cancer 1, 2
• The NCCN guidelines specifically indicate that radiation therapy should be considered only for T4 tumors with penetration to fixed structures 1, 2

Rationale for Not Recommending Radiation

• Colon cancer and rectal cancer have different patterns of recurrence and different standard treatment approaches 1, 2
• The sigmoid colon, unlike the rectum, is largely intraperitoneal and mobile, making local recurrence less common than in rectal cancer 2
• Radiation therapy is a standard component of treatment for locally advanced rectal cancer but not for colon cancer 1, 3
• The patient's tumor does not have features that would specifically indicate a benefit from radiation therapy (such as T4 status with invasion into fixed structures or positive margins) 1, 2

High-Risk Features and Their Management

• Despite the presence of high-risk features (perineural and lymphovascular invasion), adjuvant chemotherapy rather than radiation is the standard approach 1
• These high-risk features increase the risk of systemic recurrence rather than local recurrence, making systemic therapy (chemotherapy) more appropriate 1
• For T3N0 tumors with high-risk features, NCCN guidelines recommend consideration of adjuvant chemotherapy; for node-positive disease, adjuvant chemotherapy is strongly recommended 1

Evidence on Radiation in Colon Cancer

• A study using the National Cancer Database found that adjuvant radiation was associated with improved overall survival only in patients with both pT4 and positive margins, which does not apply to this case 4
• Historical studies from the 1970s and 1980s suggested potential benefits of radiation for sigmoid colon cancer, but these have been superseded by more recent evidence and guidelines 5, 6
• Current guidelines from multiple organizations do not recommend routine use of radiation therapy for colon cancer 1, 2

Surveillance Recommendations

• History and physical examination every 3-6 months for 2 years, then every 6 months for a total of 5 years 1
• CEA testing every 3-6 months for 2 years, then every 6 months for a total of 5 years 1
• Annual chest/abdominal/pelvic CT for up to 5 years for patients at high risk for recurrence 1
• Colonoscopy in 1 year; if normal, repeat in 3 years, then every 5 years 1

In conclusion, for this patient with pT3N1 sigmoid colon adenocarcinoma with negative margins, adjuvant chemotherapy alone is the standard of care, and radiation therapy is not indicated based on current guidelines and evidence.