LWBK1006-20 LWW-Govindan-Review December 12, 2011 19:4
Chapter 20•Cancer of the Gastrointestinal Tract 277Answer 20.5.14. The answer is C.
This patient is potentially curable with an aggressive multidisciplinary
approach. Resection of all tumor sites with close surveillance certainly is
an option for this patient. However, the results of the recently published
study, EORTC 40983, showed an improvement in progression-free sur-
vival for patients treated with perioperative chemotherapy with resection.
Historically, cure rates of up to 35% have been observed even in patients
with metastatic disease, as long as all tumor sites are resected. Thus, pal-
liative chemotherapy would not be the best option for this patient. There
is currently no role for radiotherapy for this patient.Answer 20.5.15. The answer is A.
Over 80% of all colorectal tumors show evidence of chromosomal insta-
bility characterized by loss of heterozygosity at multiple tumor suppressor
loci including 5q, 17p, and 18q. The other 15% to 20% of sporadic col-
orectal tumors are characterized by MSI and in many cases the MSI is
due to silencing of the MMR gene MLH1 by hypermethylation. Patients
with MSI usually are more responsive to chemotherapy and have better
outcomes. However, they appear to be resistant to treatment with 5FU.Answer 20.5.16. The answer is A.
Patients with colorectal cancer who test positive for the KRAS muta-
tion are resistant to treatment with cetuximab. In addition, BRAF V600E
mutation is also associated with resistance to cetuximab.Answer 20.5.17. The answer is C.
Sequential single-agent therapies were compared to combination
chemotherapy regimens including FOLFOX and FOLFIRI in two ran-
domized phase III trials. Even though the overall median survival was
better with combination regimens, the difference was not statistically sig-
nificant. Therefore, not all patients with metastatic unresectable colorec-
tal cancer are candidates for combination chemotherapy. Adding panitu-
mumab to FOLFOX was shown to improve progression-free survival in
patients with metastatic colorectal cancer whose tumors tested positive
for the wild-type KRAS gene. FOLFOX and FOLFIRI are both equally
effective in the first-line setting. Bowel perforation and thromboembolic
events are well known but rare toxicities seen in patients treated with
bevacizumab.