CHAPTER 1
Colon, Rectal, and
Anal Cancers
Steve Malangone, MSN, FNP-C, AOCNP®
Introduction
Colorectal adenocarcinoma is an epithelial-derived cancer that arises
from the colonic mucosa. More than 90% of colorectal cancers arise
from adenomatous polyps (Levin et al., 2008). On the cellular level, the
transformation of normal colonic mucosa to invasive cancer occurs over
a decade or longer, with an identified multistep progression from nor-
mal colonic mucosa to adenomatous polyp to invasive cancer (Sagiv et
al., 2006). This process is associated with defined, albeit heterogeneous,
genetic events (Pino & Chung, 2010). Once invasive biology occurs,
colorectal adenocarcinoma can invade both locally through direct inva-
sion and distantly through lymphatic and hematogenous spread.
The location of the tumor in the colorectum (see Figure 1-1) has
therapeutic and prognostic relevance. Tumors located in the rectum,
defined as below the peritoneal reflection (typically, the 12–15 cm above
the anal verge), are classified as rectal cancer, whereas tumors located
above the peritoneal reflection are classified as colon cancer (Kenig &
Richter, 2013). In comparison to colon cancer, rectal cancer is associated
with a relatively high rate of local recurrence, resulting in considerable
morbidity and mortality (Sauer et al., 2004). This critical distinction in
diagnosis is needed to identify a proper interprofessional management
strategy (see Preoperative Management).
Anal cancer represents a less common form of gastrointestinal malig-
nancy that arises from the epithelium of the anal canal. Anal cancers are
distinct from rectal cancers and perianal skin cancers in that they origi-
nate from the epithelium between the anorectal ring and the anal verge
(Czito, Ahmed, Kalady, & Eng, 2015). Anal cancer epidemiology, risk
factors, prognosis, and histology represent a distinct entity and are dis-
cussed in the following sections.
1
Copyright 2019 by Oncology Nursing Society. All rights reserved.
,2 Gastrointestinal Cancer Care for Oncology Nurses
Figure 1-1. Colorectal Cancer
Note. Image courtesy of Blausen Medical Communications, Inc., via Wikimedia Commons.
Retrieved from https://commons.wikimedia.org/wiki/File:Blausen_0246_ColorectalCancer
.png. Used under the Creative Commons Attribution 3.0 Unported (CC BY 3.0) license (https://
creativecommons.org/licenses/by/3.0/legalcode).
Incidence and Epidemiology
The lifetime risk of developing colorectal cancer in the United States
is estimated at 5% (Siegel, Miller, & Jemal, 2018). As the fourth most
frequently diagnosed cancer for both sexes combined, colorectal cancer
is a common malignancy, with 140,250 new cases estimated for 2018 in
the United States. It is also the second leading cause of cancer death for
both sexes combined (Siegel et al., 2018).
Colorectal cancer represents significant morbidity and mortality
globally. The estimated global incidence is 1.4 million new cases per
year, with approximately 694,000 deaths estimated annually (Torre et
al., 2015).
Overall, colorectal cancer incidence in the United States is declining.
Between 2005 and 2014, incidence declined 3% per year (Siegel et al.,
2018). This decrease is attributable to relative reduction in risk factors
and increased use of screening colonoscopy with removal of precancer-
ous polyps (Siegel, Ward, & Jemal, 2012).
In contrast, colorectal cancer incidence is rising among people
younger than age 50 in the United States. From the mid-1980s through
Copyright 2019 by Oncology Nursing Society. All rights reserved.
, Chapter 1. Colon, Rectal, and Anal Cancers 3
2013, colon and rectal cancer rates in adults aged 20–29 years and
40–54 years increased at an annual rate of 1%–2.4% and 0.5%–1.3%,
respectively. Rectal cancer in people younger than age 55 now repre-
sents one-third of all new diagnoses, with a disproportionately higher
increase of 3.2% annually from 1974 to 2013 in the 20–29-year age
group. The proportion of rectal cancer cases in people younger than
age 55 in the United States has doubled in the past three decades, from
14.6% to 29.2% (Siegel et al., 2017). Familial syndromes account for
approximately 20% of these cases while 80% are sporadic (Ahnen et
al., 2014). Young-onset colorectal cancers occur more frequently in the
distal colon and rectum and are more likely to be poorly differentiated,
have signet ring features, and present at advanced stages compared with
those diagnosed at a later onset (Ahnen et al., 2014).
Mortality from colorectal cancer is decreasing in the United States.
Mortality decreased by 35% from 1990 to 2007 (Henley et al., 2015) and
by 50% from 1970 to 2015 (Siegel et al., 2018). This trend is attributable
to earlier detection and improved therapies (Jemal et al., 2011).
Anal cancer is a relatively uncommon malignancy, with 8,580 new
cases estimated for 2018 in the United States (Siegel et al., 2018). Despite
the rarity of anal cancer, the incidence has almost doubled in recent
years, from 1.2 cases per 100,000 per year during 1973–1996 to 2.2 cases
per 100,000 per year during 1997–2009 (Nelson, Levine, Bernstein,
Smith, & Lai, 2013). The increased rates result from increased risk fac-
tors, including infection with oncogenic human papillomavirus (HPV),
immunocompromised conditions, and smoking.
Etiology and Risk Factors
Modifiable and nonmodifiable risk factors contribute to the devel-
opment of colorectal adenocarcinoma. Several clearly defined familial
syndromes have been identified, the most common of which are famil-
ial adenomatous polyposis, hereditary nonpolyposis colorectal cancer
(also known as Lynch syndrome), Peutz-Jeghers syndrome, and juvenile
polyposis syndrome (Burt & Neklason, 2005; see Table 1-1).
The National Comprehensive Cancer Network® (NCCN®, 2018d) rec-
ommends that whenever possible, patients with a significant family his-
tory of colorectal or associated cancer, a known family history of familial
cancer syndrome, or a history of multiple cancer primaries be referred
to a genetic counselor. The purpose of this referral is for review of his-
tory, consideration of germline genetic testing, and provision of screen-
ing recommendations for patients and potentially affected family mem-
bers.
Copyright 2019 by Oncology Nursing Society. All rights reserved.
,
4
Table 1-1. Familial Syndromes Associated With Increased Risk for Colorectal Cancer
Lifetime Risk
of Developing Screening
Colorectal and Treatment
Syndrome Prevalence Clinical Features Cancer Genes Involved Recommendations
Familial < 1% of all > 10–20 polyps, often asso 100% in classic APC (adenomatous Referral to genetics;
adenomatous colorectal cases ciated with 100s to 1,000s FAP polyposis coli) referral to surgery for
polyposis (FAP) of colonic polyps; also asso MUTYH consideration of total
ciated with desmoid tumor, proctocolectomy
hepatoblastoma, and thyroid
cancer
Hereditary nonpoly 3%–5% of all Not associated with polypo 50%–80% (MLH1, Mismatch repair Referral to genetics
posis colorectal colorectal can sis; strong family history of MSH2) genes: MLH1,
cancer cer cases colorectal, endometrial, and 15%–20% (MSH6) MSH2, MSH6,
Gastrointestinal Cancer Care for Oncology Nurses
(Lynch syndrome) urothelial malignancy 10%–22% (PMS2) PMS2
Juvenile polyposis Rare; < 1% of all Autosomal dominant, strong 50% BMPR1A Referral to genetics
syndrome colorectal can family history, right-sided MADH4
cer cases hamartomatous polyps, rec
tal bleeding is common
Peutz-Jeghers Rare; < 1% of all Personal or family history 39% STK11 (LKB1) Referral to genetics
syndrome colorectal can of breast, colorectal, small
cer cases intestine, pancreatic, ovarian,
and lung cancers
Copyright 2019 by Oncology Nursing Society. All rights reserved.
Note. Based on information from Burt & Neklason, 2005; National Comprehensive Cancer Network, 2018c.
Colon, Rectal, and
Anal Cancers
Steve Malangone, MSN, FNP-C, AOCNP®
Introduction
Colorectal adenocarcinoma is an epithelial-derived cancer that arises
from the colonic mucosa. More than 90% of colorectal cancers arise
from adenomatous polyps (Levin et al., 2008). On the cellular level, the
transformation of normal colonic mucosa to invasive cancer occurs over
a decade or longer, with an identified multistep progression from nor-
mal colonic mucosa to adenomatous polyp to invasive cancer (Sagiv et
al., 2006). This process is associated with defined, albeit heterogeneous,
genetic events (Pino & Chung, 2010). Once invasive biology occurs,
colorectal adenocarcinoma can invade both locally through direct inva-
sion and distantly through lymphatic and hematogenous spread.
The location of the tumor in the colorectum (see Figure 1-1) has
therapeutic and prognostic relevance. Tumors located in the rectum,
defined as below the peritoneal reflection (typically, the 12–15 cm above
the anal verge), are classified as rectal cancer, whereas tumors located
above the peritoneal reflection are classified as colon cancer (Kenig &
Richter, 2013). In comparison to colon cancer, rectal cancer is associated
with a relatively high rate of local recurrence, resulting in considerable
morbidity and mortality (Sauer et al., 2004). This critical distinction in
diagnosis is needed to identify a proper interprofessional management
strategy (see Preoperative Management).
Anal cancer represents a less common form of gastrointestinal malig-
nancy that arises from the epithelium of the anal canal. Anal cancers are
distinct from rectal cancers and perianal skin cancers in that they origi-
nate from the epithelium between the anorectal ring and the anal verge
(Czito, Ahmed, Kalady, & Eng, 2015). Anal cancer epidemiology, risk
factors, prognosis, and histology represent a distinct entity and are dis-
cussed in the following sections.
1
Copyright 2019 by Oncology Nursing Society. All rights reserved.
,2 Gastrointestinal Cancer Care for Oncology Nurses
Figure 1-1. Colorectal Cancer
Note. Image courtesy of Blausen Medical Communications, Inc., via Wikimedia Commons.
Retrieved from https://commons.wikimedia.org/wiki/File:Blausen_0246_ColorectalCancer
.png. Used under the Creative Commons Attribution 3.0 Unported (CC BY 3.0) license (https://
creativecommons.org/licenses/by/3.0/legalcode).
Incidence and Epidemiology
The lifetime risk of developing colorectal cancer in the United States
is estimated at 5% (Siegel, Miller, & Jemal, 2018). As the fourth most
frequently diagnosed cancer for both sexes combined, colorectal cancer
is a common malignancy, with 140,250 new cases estimated for 2018 in
the United States. It is also the second leading cause of cancer death for
both sexes combined (Siegel et al., 2018).
Colorectal cancer represents significant morbidity and mortality
globally. The estimated global incidence is 1.4 million new cases per
year, with approximately 694,000 deaths estimated annually (Torre et
al., 2015).
Overall, colorectal cancer incidence in the United States is declining.
Between 2005 and 2014, incidence declined 3% per year (Siegel et al.,
2018). This decrease is attributable to relative reduction in risk factors
and increased use of screening colonoscopy with removal of precancer-
ous polyps (Siegel, Ward, & Jemal, 2012).
In contrast, colorectal cancer incidence is rising among people
younger than age 50 in the United States. From the mid-1980s through
Copyright 2019 by Oncology Nursing Society. All rights reserved.
, Chapter 1. Colon, Rectal, and Anal Cancers 3
2013, colon and rectal cancer rates in adults aged 20–29 years and
40–54 years increased at an annual rate of 1%–2.4% and 0.5%–1.3%,
respectively. Rectal cancer in people younger than age 55 now repre-
sents one-third of all new diagnoses, with a disproportionately higher
increase of 3.2% annually from 1974 to 2013 in the 20–29-year age
group. The proportion of rectal cancer cases in people younger than
age 55 in the United States has doubled in the past three decades, from
14.6% to 29.2% (Siegel et al., 2017). Familial syndromes account for
approximately 20% of these cases while 80% are sporadic (Ahnen et
al., 2014). Young-onset colorectal cancers occur more frequently in the
distal colon and rectum and are more likely to be poorly differentiated,
have signet ring features, and present at advanced stages compared with
those diagnosed at a later onset (Ahnen et al., 2014).
Mortality from colorectal cancer is decreasing in the United States.
Mortality decreased by 35% from 1990 to 2007 (Henley et al., 2015) and
by 50% from 1970 to 2015 (Siegel et al., 2018). This trend is attributable
to earlier detection and improved therapies (Jemal et al., 2011).
Anal cancer is a relatively uncommon malignancy, with 8,580 new
cases estimated for 2018 in the United States (Siegel et al., 2018). Despite
the rarity of anal cancer, the incidence has almost doubled in recent
years, from 1.2 cases per 100,000 per year during 1973–1996 to 2.2 cases
per 100,000 per year during 1997–2009 (Nelson, Levine, Bernstein,
Smith, & Lai, 2013). The increased rates result from increased risk fac-
tors, including infection with oncogenic human papillomavirus (HPV),
immunocompromised conditions, and smoking.
Etiology and Risk Factors
Modifiable and nonmodifiable risk factors contribute to the devel-
opment of colorectal adenocarcinoma. Several clearly defined familial
syndromes have been identified, the most common of which are famil-
ial adenomatous polyposis, hereditary nonpolyposis colorectal cancer
(also known as Lynch syndrome), Peutz-Jeghers syndrome, and juvenile
polyposis syndrome (Burt & Neklason, 2005; see Table 1-1).
The National Comprehensive Cancer Network® (NCCN®, 2018d) rec-
ommends that whenever possible, patients with a significant family his-
tory of colorectal or associated cancer, a known family history of familial
cancer syndrome, or a history of multiple cancer primaries be referred
to a genetic counselor. The purpose of this referral is for review of his-
tory, consideration of germline genetic testing, and provision of screen-
ing recommendations for patients and potentially affected family mem-
bers.
Copyright 2019 by Oncology Nursing Society. All rights reserved.
,
4
Table 1-1. Familial Syndromes Associated With Increased Risk for Colorectal Cancer
Lifetime Risk
of Developing Screening
Colorectal and Treatment
Syndrome Prevalence Clinical Features Cancer Genes Involved Recommendations
Familial < 1% of all > 10–20 polyps, often asso 100% in classic APC (adenomatous Referral to genetics;
adenomatous colorectal cases ciated with 100s to 1,000s FAP polyposis coli) referral to surgery for
polyposis (FAP) of colonic polyps; also asso MUTYH consideration of total
ciated with desmoid tumor, proctocolectomy
hepatoblastoma, and thyroid
cancer
Hereditary nonpoly 3%–5% of all Not associated with polypo 50%–80% (MLH1, Mismatch repair Referral to genetics
posis colorectal colorectal can sis; strong family history of MSH2) genes: MLH1,
cancer cer cases colorectal, endometrial, and 15%–20% (MSH6) MSH2, MSH6,
Gastrointestinal Cancer Care for Oncology Nurses
(Lynch syndrome) urothelial malignancy 10%–22% (PMS2) PMS2
Juvenile polyposis Rare; < 1% of all Autosomal dominant, strong 50% BMPR1A Referral to genetics
syndrome colorectal can family history, right-sided MADH4
cer cases hamartomatous polyps, rec
tal bleeding is common
Peutz-Jeghers Rare; < 1% of all Personal or family history 39% STK11 (LKB1) Referral to genetics
syndrome colorectal can of breast, colorectal, small
cer cases intestine, pancreatic, ovarian,
and lung cancers
Copyright 2019 by Oncology Nursing Society. All rights reserved.
Note. Based on information from Burt & Neklason, 2005; National Comprehensive Cancer Network, 2018c.
