Rectal Tropism: An Extremely Rare Case of Prostate Cancer Recurrence With Metastasis to the Rectum Postradical Prostatectomy

Abstract

Prostate cancer is the most common noncutaneous cancer affecting men in the United States. It is a slow-growing tumor that can be missed during the nascent phase. Prostate cancer commonly metastasizes to the bones and nearby lymph nodes. However, cases of metastatic prostate cancer to the rectum are exceptionally rare. Such metastases may cause obstructive or malabsorption symptoms similar to those observed in primary rectal carcinoma. We present a very rare case of prostate cancer recurrence with rectal metastasis in an elderly male with a history of castration-resistant prostate carcinoma status postradical prostatectomy.

Introduction

Prostate carcinoma is the second most common cancer affecting men in the West. ¹ This neoplasm commonly spreads to the regional lymph nodes, liver, lungs, and bones.^2,3 Rectal tropism of metastasis is extremely rare and poses a diagnostic challenge.^1,2,4 The proposed pathophysiology is via lymphatic spread, seeding during a transrectal biopsy, or local tissue invasion. ¹ Herein, we present an exceedingly rare case of prostate cancer with metastasis to the rectum in a geriatric male patient with a history of radical prostatectomy.

Case Report

A 77-year-old man with a medical history of hypertension and castration-resistant prostate carcinoma status postradical prostatectomy with bilateral lymph node dissection in 2001 presented to the emergency department (ED) with an 8-month history of progressively worsening watery, nonbloody diarrhea, malaise, and decreased oral intake. The patient reported 5 to 6 loose bowel movements per day and an unquantifiable weight loss. Diarrhea was not associated with food intake and persisted during episodes of fasting. He denied any abdominal pain, cramps, nausea, vomiting, fevers, chills, or any blood in the stool. He also reported bilateral leg swelling without chest pain, palpitations, shortness of breath, orthopnea, or paroxysmal nocturnal dyspnea.

On presentation, his hemodynamics were within normal limits. On physical examination, the patient appeared cachectic with temporal wasting. His abdomen was soft, nondistended, and nontender on palpation. Hyperactive bowel sounds were appreciated in all quadrants. On neurological examination, he displayed an unsteady gait; otherwise, cranial nerves were grossly intact. The remaining systems were unremarkable. Digital rectal examination revealed a palpable rectal mass and a rectal stricture, but no fresh blood or abscesses. Laboratory admission values were significant for pancytopenia, elevated prostate-specific antigen (PSA) levels, low testosterone levels, and normal carcinoembryonic antigen (CEA) (Table 1). Later in the day, the patient became hypoxic, raising concerns for pulmonary embolism. Computerized tomographic (CT) angiography of the chest yielded negative results. However, multiple pulmonary nodules and numerous osseous metastases were identified.

Table 1.

Showing Pertinent Admission Labs Compared to Normal Ranges.

Variable	Admission Labs	Reference range
White blood count	4.1 103/mm3	4.5-11.0 103/mm3
Hemoglobin	10.0	13.5-17.5 g/dL
CEA	17.2	0.0-10.0 ng/mL
Alkaline phosphatase	317	34-104 unit/L
Prostate-specific antigen (PSA)	>1500.00	≤3.99 ng/mL
Testosterone level	125	264-916 ng/dL

Given the patient’s chronic diarrhea and palpable rectal mass, there was a high index of suspicion for a colonic malignancy. The infectious stool workup (Clostridium difficile toxin and antigen, ova and parasite, Giardia, and cryptosporidium) was negative. The patient denied any family history of inflammatory bowel disease and the workup result was unremarkable. Following a review of the above workup and physical examination findings, a colonoscopy was performed, which revealed an extrinsic severe stenosis measuring 2 cm (in length) in the distal rectum. The colon was traversed after down-sizing to an EGD scope, and a partially obstructing large mass was found in the mid and distal rectum (Figure 1). The mass was circumferential and measured 15 cm long. The specimen was biopsied using a cold forceps for histological analysis.

Figure 1.

Endoscopic images showing severe stenosis of the distal rectum and a partially obstructing large mass in the mid and distal rectum.

We performed contrast-enhanced CT scan of the abdomen and pelvis for cancer staging, which showed severe confluent metastatic blastic osseous disease. Surgical pathology of the rectal mass revealed numerous malignant glands infiltrating the rectal mucosa (Figure 2). Tumor cells were positive for PSA and negative for the gastrointestinal marker caudal-type homeobox 2 (CDX2) (Figure 2), thus confirming metastatic prostatic carcinoma with rectal metastasis.

Figure 2.

Histopathological images showing numerous malignant glands infiltrating the rectal mucosa (top panels). Tumor cells are positive for PSA (bottom panels).

The patient’s diarrhea improved with loperamide treatment, and the diet was advanced as tolerated. The patient was discharged with instructions for follow-up with the colorectal surgeon and oncologist as outpatient. His presentation was consistent with prostate cancer with metastasis to the rectum, and he was being evaluated for hormone replacement therapy and palliative radiotherapy. One month after discharge, the patient was brought to the ED because of hypotension and unresponsiveness. Given the patient’s Eastern Cooperative Oncology Group (ECOG) performance status of 4, the family transitioned him to comfort care, and he died 2 days later.

Discussion

Prostate cancer is the second most common cause of cancer-related deaths in men in the United States of America. ⁴ It affects about 1 in 8 men during their lifetime. ³ Risk factors include advanced age, African American ethnicity, and a family history of prostate cancer.^3,4 Prostate cancer arises from mutations in the prostate gland cells, mainly in the p53 gene or Akt kinase signaling alterations. ⁵ While the progression of prostate cancer is generally predictable, there are instances where the diagnosis proves difficult. ³ Metastatic prostate carcinoma frequently spreads to the regional lymph nodes, bones, ³ the base of the bladder, ¹ and adrenal glands. ⁴ Uncommon metastasis locations have been reported in the literature, including the esophagus, stomach, liver, penis, and brain. ¹ Rectal involvement is very infrequent and a sign of poor prognosis. ³ The true incidence of rectal metastases is unknown.

The slow-growing nature of prostate cancer and the limitations of the PSA test often result in delayed diagnosis, and patients may present with metastatic symptoms.^3,6 With proximity to the bladder, prostatic cancer often manifests as dysuria, urinary urgency, urinary frequency, or nocturia. ⁵ Hematuria has also been reported in a few cases. ⁵ And due to its propensity to metastasize to the axial skeleton, prostate cancer can present as anemia secondary to bone marrow suppression. Soe et al ⁴ reported a rare case of metastatic prostate cancer manifesting as anemia of unknown etiology. The patient refused chemotherapy and pursued comfort care instead.

The spread of prostate cancer to the rectum is extremely rare. ⁵ The anatomical structure of the prostate gland and its relationship with the rectal wall provide 3 possible routes for prostate cancer to infiltrate the colorectal tissue.^3,4,6 Prostate cancer can infiltrate the colorectal tissue by infiltrating Denonvilliers’ fascia.^3,6 Pelvic lymph nodes also receive drainage from the prostate gland and the rectum, which provides another possible mechanism of cancer spread. ³ Seeding of cancer cells into the perirectal or rectal tissue during prostate biopsy is the third route. ³ Prostatic cancer spread to the rectum often presents as diarrhea, rectal bleeding, pruritus, or obstruction.^3-6 Almujarkesh et al ³ reported a unique case of large bowel obstruction due to metastatic prostate cancer.

It is crucial to distinguish between primary and metastatic colorectal lesions, especially in patients with a history of cancer at a different site.^1,4 Endoscopy with biopsy is the best diagnostic method. Primary colonic adenocarcinomas can be potentially curative through surgery and chemoradiation. ¹ On the contrary, the treatment of colonic metastasis depends on the primary site, patient desire, and quality of life and is mainly palliative.^1,4 Metastatic prostate cancer has a poor prognosis, with survival rates ranging from 1 to 3 years.^1,4,5 Our patient died after 8 months of symptoms and a month after diagnosis. Resection of metastases should be performed to improve the quality of life and prevent further complications. Palliative surgery interventions include abdominoperineal resection, pelvic exenteration, resection, and colostomy creation. ² Options for hormone-refractory prostate cancer include secondary hormonal treatment, antiandrogens, radiotherapy, and cytotoxic chemotherapy.^1,4,5 A multidisciplinary approach is essential for further management when a diagnosis is obtained and confirmed. ²

Conclusion

Prostate cancer is the second most common cancer affecting men in the United States of America. This cancer frequently spreads to the lungs, bones, liver, and regional lymph nodes. Prostate cancer recurrence with metastasis to the rectum is exceedingly rare and poses a diagnostic challenge. A multidisciplinary approach is essential for further management when a diagnosis is obtained and confirmed on histopathology.