LUNG CANCER IN DOGS

Maruf Minar

Laboratory of Surgery

College of Veterinary Medicine

CBNU

INTRODUCTION

Lung cancer in dogs: A potentially fatal diagnosis for a dog that can be devastating for the owner.

Lung cancer in dogs is almost always secondary in nature.

Most common in older, medium to large dogs.

TYPES OF LUNG CANCER There are 2 types of lung cancer diagnosed in

dogs:

Primary lung cancer Metastatic lung cancer

Primary lung cancer is defined as lung tumors originating in the lung tissue whereas secondary lung cancer originates elsewhere in the body such as limb bone, mouth or thyroid gland but spread to the lung via bloodstream.

LUNG CANCER

Primary Lung Tumor

CONT.

Metastatic Lung Cancer

CONT.

Primary lung tumors are almost always malignant and are usually carcinomas.

They usually present as large solitary mass visible in the lung on a chest x-ray.

Metastatic or secondary lung cancer are usually found in multiple, not as single mass.

ETIOLOGY

No straightforward etiology.

Non-lethal genetic mutations in the DNA can make changes in the regulation of cell death and replacement deviate from the normal.

Surrounding environment can be considered.

Secondary smoking from the smoker owners.

Asbestos can be a cause of a specific form of lung cancer called mesothelioma.

RISK FACTORS

Both male and female dogs are susceptible.

Increase risk associated with living in urban area.

Average age of diagnosis is 11 years.

Short-nosed dogs have twice the risk as medium or long-nosed dogs.

SYMPTOMS

Chronic coughing which may also produce phlegm or blood.

Exercise intolerance (lethargy).

Weight loss and loss of appetite.

Distressed breathing or shortness of breath.

Occasional lameness if the cancer spreads to the bone.

DIAGNOSIS History:

1. Duration of the disease.2. Surrounding environment.

Physical Examination:1. Abnormal or muffled lung sounds indicating

dyspnea.2. Enlarged lymph nodes or skin lesions.

CONT. Diagnostic tests:

1. Complete blood count

2. Biochemical profile (blood sugar, blood proteins, electrolytes.

3. Urinalysis

4. Chest radiographs: Single most important tool for preliminary diagnosis.

5. Fine needle aspirate of lung mass.

6. Bronchoscopy

7. Advanced imaging: CT and MRI.

TYPICAL FINDINGS ON RADIOGRAPHS

Primary lung tumors frequently found in the caudal lobe, usually single mass (unless spread).

Metastatic tumors are multiple and found in a variety of lung lobes.

CONT.

Left: single mass located in one of the lung lobes.

Right: Multiple round masses in the lungs representing metastatic forms of tumors.

CONT.

Lung lobe tumor (black arrows) in one of the caudal lung lobes.

CONT.

Pleural effusion resulting from lung tumor

CONT.

CT and MRI provide more accurate information on staging for resectability and detection of occult metastasis and hilar lymph node enlargement.

CLINICAL STAGINGPrimary Tumor

T-0 No evidence of neoplasia

T-1 Solitary lung tumor surrounded by lung or visceral pleura

T-2 Multiple lung tumors of various sizes

T-3 Lung tumor invading adjacent tissue

Node

N-0 No evidence of lymph node involvement

N-1 Bronchial lymph node involvement

N-2 Distant lymph node involvement

Metastasis

M-0 No evidence of metastasis

M-1 Evidence of distant metastasis with site specified

* 37-55% dogs have T-1 disease at surgery, 22-25% have lymph node metastasis and 8% have distant metastasis.

TREATMENT OPTIONS

Single lung lobe tumors are removed surgically.

Multiple lung lobe tumors are usually metastatic- cancer spread from another site and treated with chemotherapy.

SURGICAL CORRECTION OF SINGLE LUNG TUMORS

Each lung lobe can be removed separately.

Through an incision in the side of the chest (“Lateral thoracotomy”), just behind the forelimb.

Incision goes between the ribs, spreading apart and then brought back together once the lung lobe has been removed.

The vessels and bronchus to the lobe are either tied off with suture or with stapler.

CONT.

Median sternotomy for large tumors and inspection of other lung lobes.

LATERAL THORACOTOMY

• Animal in lateral recumbency

• 2cm caudal to the scapula– 4th or 5th intercostal

space

CONT.

Latissimus dorsi and pectoralis muscles are

incised parallel to the skin incision

CONT.

1. Inserting a finger deep latissimus dorsi, locate the 1st rib

and 5th rib

2. 5th rib is identified by the caudal insertion of the

scalenus muscle and the cranial origin of the external

abdominal oblique muscle. Incise either muscle

depending on the inercostal space to be entered

CONT.

• Incise serratus ventralis

muscle. Note branch of the

intercostal artery supplying

each belly of serratus ventralis• Incise intercostal muscles

midway

CONT.

• Bluntly puncturing the pleura and extending the incision with scissor dorsally to the tubercle of the rib and ventrally past the costochondral arch to the internal thoracic vessels

CONT.

• Unaffected lung lobes are packed out of the way with

moist laparotomy sponges

• Pulmonary vessels and the lobar bronchus are

identified

• Hilar dissection.

• Dissect pulmonary artery. Triple ligate with two

encircling sutures and one transfixation. Transect

between the two distal sutures.

CONT.

• Pulmonary vein approached on the ventral side of the

bronchus

• Two encircling and one transfixing ligatures. Transect the

vein

• The main bronchus dissected. Cross-clamped with two

pairs of non-crushing-type forceps. Transect

CONT.• Bronchus is sutured with interrupted

horizontal mattress suture (collapse

the bronchus)

• The bronchus is transected just distal

to these suture.

• The bronchial suture line is tested for

air leakage:

1. Flood the thorax with warm

saline

2. Ventilate the animal 25 to 30cm

H2O pressure

3. Additional suture may by placed

to close major leaks

CONT.

• A 2 inches lung lobe tumor in a caudal lung lobe. A black suture has been passed around the large artery to the lobe.

• The ribs have been spread apart to expose a lung lobe tumor in a middle lung lobe.

CONT.

• The stapler has been placed across the lung lobe to seal the end of the lobe.

• Appearance of the site after the lobe has been stapled off and removed (Black arrow).

CONT.

• Rib apposition

• Four cruciate, or four to six encircling suture placed

around the ribs, cranial and caudal to the thoracotomy

• Place traction of one or more of the suture while the

remaining sutures are tied

CONT.

• Placement of circumcostal suture will entrap intercostal

nerves

• Transcostal suture may lessen postoperative pain

CONT.

• Before closing the thoracotomy,

a thoracostomy drain is placed to

establish negative pressure in

the pleural space

• Reappose muscles separately

• Close subcutis and skin routinely

CONT.

The chest tube is used to remove excess fluid or air and to install a local anesthetic to block pain.

POSTOPERATIVE CARE

Monitor if hypoventilation, hypoxemia

occur

Pain control

Chest tubes are aspired frequently (every

2-4hours), and the amount of air is

quantitated

Chest tubes are generally removed in 24-

48 hours if air is not accumulating

PROGNOSIS

The prognosis is generally good for dogs with single primary lung tumor, small mass in the lungs that has not been spread to the lymph nodes or other tissue.

More than 50% are expected to survive 1 year after removal of mass.

THE END

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