Cancer Flashcards
What is basal cell carcinoma?
Most common type of cancer in the Western world
Related to exposure to sunlight
Clinically presents as a pearly white papulo-nodule or firm plaque
What is the aetiology of basal cell carcinoma?
Repetitive and frequent sun exposure, as ultraviolet radiation induces DNA damage in keratinocytes
What are the characteristics of basal cell carcinomas?
Slow-growth and local invasion
Initially a pearly, flesh-coloured papule with telangiectasia
May later ulcerate leaving a central ‘crater’
What sites are usually affected in basal cell carcinomas?
Sun-exposed sites, especially the head and neck account for the majority of lesions
What are the appropriate investigations for basal cell carcinoma?
Generally, if a BCC is suspected, a routine referral should be made on the 2WW
Biopsy for dermatohistopathology:
(diagnosis of a cancer is histological)
What are some of the management options for basal cell carcinoma?
Surgical removal
Curettage
Cryotherapy
Topical cream: imiquimod, fluorouracil
Radiotherapy
What is bladder cancer and who does it commonly affect?
The second most common urological cancer
It most commonly affects males aged between 50 and 80 years of age
What are the two types of bladder cancer?
- Urothelial (transitional cell) carcinoma
- Squamous cell carcinoma
What is the most common type of bladder cancer?
Urothelial carcinoma (previously termed transitional cell carcinoma)
>90%
What are the risk factors for urothelial carcinoma of the bladder?
- Smoking: most important risk factor in western countries
- Exposure to aniline dyes: for example working in the printing and textile industry e.g. 2-naphthylamine and benzidine
- Rubber manufacture
- Cyclophosphamide
What are the risk factors for squamous cell carcinoma of the bladder?
Schistosomiasis: causes chronic bladder inflammation
Smoking
What are the presenting symptoms of bladder cancer?
Most patients (85%) will present with painless, macroscopic haematuria
Others:
Recurrent UTIs
Dysuria: associated with aggressive bladder cancer
Voiding irritability
What are the appropriate investigations for bladder cancer?
Cystoscopy and biopsies or TURBT: this provides histological diagnosis and information relating to depth of invasion (for staging)
Others:
CT urogram = diagnostic and provides staging
Urinalysis
What is TURBT (in context of bladder cancer)?
Trans urethral resection of bladder tumour
What is the management of bladder cancer?
Superficial lesions: TURBT in isolation
Recurrences or higher grade/ risk on histology: intravesical chemotherapy
T2 disease: offered either surgery (radical cystectomy and ileal conduit) or radical radiotherapy
What is the staging of bladder cancer?
T0 = no evidence of tumour
T1 = Tumour invades sub epithelial connective tissue
T2a = Tumour invades superficial muscularis propria (inner half)
T2b = Tumour invades deep muscularis propria (outer half)
T3 = Tumour extends to perivesical fat
T4 = Tumor invades any of the following: prostatic stroma, seminal vesicles, uterus, vagina
a = Invasion of uterus, prostate or bowel
b = Invasion of pelvic sidewall or abdominal wall
Nodal and Metastasis
What is the prognosis of bladder cancer?
Depends on staging:
T1 = 90%
T2 = 60%
T3 = 35%
T4a = 10-25%
Any T, N1-N2 = 30%
What is breast cancer?
A malignancy originating in the breast(s) and nodal basins
What are some of the predisposing factors for breast cancer?
- BRCA1, BRCA2 genes - 40% lifetime risk of breast/ovarian cancer
- 1st degree relative premenopausal relative with breast cancer (e.g. mother)
- Nulliparity, 1st pregnancy > 30 yrs (twice risk of women having 1st child < 25 yrs)
- Oestrogen exposure: early menarche, late menopause
- COCP: (relative risk increase * 1.023/year of use), combined oral contraceptive use
- Past breast cancer
- Not breastfeeding
- Ionising radiation
- p53 gene mutations
- obesity
What is the epidemiology of breast cancer?
Breast cancer is the most common female malignancy
It is most commonly diagnosed in middle-aged or older women (median age at diagnosis is 62 years)
Women are affected 100x more than men
What are the presenting symptoms of breast cancer?
Breast mass (does not have to be a new mass)
Nipple discharge
Skin thickening
Retraction of the nipple
What are the signs of breast cancer on physical examination?
History of breast mass: tenderness, change in size or character (in relation to menstrual cycle)
Nipple discharge: bloody is more classically associated with neoplasm
Overlying skin changes: Peau d’orange (dimpling of the skin), erythema, ulceration, retraction of nipple (Paget’s?)
Axillary lymphadenopathy: nodal involvement increases in proportion to the size of the tumour
What are the appropriate investigations for breast cancer?
Triple assessment:
1. Clinical examination
2. Imaging: an irregular spiculated mass, clustered microcalcifications, and linear branching calcifications
3. Core (needle) biopsy: histological findings confirming an invasive ductal carcinoma, invasive lobular carcinoma, medullary carcinoma, mucinous carcinoma, or metaplastic carcinoma
What are the different types of breast cancer?
Most breast cancers arise from duct tissue followed by lobular tissue, described as ductal or lobular carcinoma respectively
These can be further subdivided as to whether the cancer hasn’t spread beyond the local tissue (described as carcinoma-in-situ) or has spread (described as invasive)
1. Invasive ductal carcinoma (‘No Special Type (NST)’) = MOST COMMON
2. Invasive lobular carcinoma
3. Ductal carcinoma-in-situ (DCIS)
4. Lobular carcinoma-in-situ (LCIS)
What is Paget’s disease of the nipple?
An eczematoid change of the nipple associated with an underlying breast malignancy (retraction of the nipple)
Present in 1-2% of patients with breast cancer
In half of these patients, it is associated with an underlying mass lesion and 90% of such patients will have an invasive carcinoma
30% of patients without a mass lesion will still be found to have an underlying carcinoma
The remainder will have carcinoma in situ
What is the referral pathway for breast cancer?
2WW if:
1. Aged 30 and over and have an unexplained breast lump with or without pain or
2. Aged 50 and over with any of the following symptoms in one nipple only: discharge, retraction or other changes of concern
Consider 2WW if:
1. Skin changes that suggest breast cancer or
2. Aged 30 and over with an unexplained lump in the axilla
Non-urgent referral if: under 30 with an unexplained breast lump with or without pain
What are the management options for breast cancer?
Depends on the staging, tumour type and patient background
Ultimately patient’s choice!
Options include:
Surgery
Radiotherapy
Hormone therapy
Biological therapy
Chemotherapy
What surgical options are available for breast cancer?
Vast majority will be offered surgery
Mastectomy and wide local excision (2/3rds can be WLE)
Prior to surgery: presence/absence of axillary lymphadenopathy?
- if positive then they should have a sentinel node biopsy to assess the nodal burden
- if clinically palpable lymphadenopathy, axillary node clearance is indicated at primary surgery (this may lead to arm lymphedema and functional arm impairment)
What are the indications for a mastectomy and wide local excision?
Mastectomy:
Multifocal tumour
Central tumour
Large lesion in small breast
DCIS > 4cm
WLE:
Solitary lesion
Peripheral tumour
Small lesion in large breast
DCIS < 4cm
What should all women be offered if they have surgical management of breast cancer?
Regardless of type of surgical treatment, all women should be offered breast reconstruction to achieve a cosmetically suitable result
What radiotherapy options are available for breast cancer?
WLE: Whole breast radiotherapy is recommended after WLE (may reduce the risk of recurrence by around two-thirds)
Mastectomy: radiotherapy is offered for T3-T4 tumours and for those with four or more positive axillary nodes
What hormonal therapy options are available for breast cancer?
Adjuvant hormonal therapy is offered if tumours are positive for hormone receptors
Tamoxifen is still used in pre- and peri-menopausal women
In post-menopausal women, aromatase inhibitors such as anastrozole are used for this purpose (aromatisation accounts for the majority of oestrogen production in post-menopausal women and therefore anastrozole is used for ER +ve breast cancer in this group)
*Important side-effects of tamoxifen include an increased risk of endometrial cancer, VTE and menopausal symptoms
What chemotherapy options are available for breast cancer?
Cytotoxic therapy may be used either prior to surgery (‘neoadjuvanant’ chemotherapy) to downstage a primary lesion
Or
After surgery depending on the stage of the tumour e.g. if there is axillary node disease - FEC-D is used in this situation (5-fluorouracil, epirubicin, cyclophosphamide and docetaxel)
What biological therapies are available for breast cancer?
The most common type of biological therapy is trastuzumab (Herceptin)
It is only useful in the 20-25% of tumours that are HER2 positive.
*Trastuzumab cannot be used in patients with a history of heart disorders
What is the breast cancer screening pathway?
Mammogram offered to women between the ages of 50-70 years every 3 years
> 70 years women may still have mammograms but are ‘encouraged to make their own appointments’
What are central nervous system tumours?
Primary tumours arising from any of the brain tissue types
What is the most common type of brain tumour?
Metastatic brain cancer
Often multiple and not treatable with surgical intervention
Tumours that most commonly spread to the brain include:
- Lung (most common)
- Breast
- Bowel
- Skin (namely melanoma)
- Kidney
What is the most common primary brain tumour in adults?
Glioblastoma multiforme
What are the features of glioblastomas on imaging?
Solid tumours with central necrosis and a rim that enhances with contrast
Disruption of the blood-brain barrier and therefore are associated with vasogenic oedema
What are the histological features of glioblastomas?
Pleomorphic tumour cells border necrotic areas
What is the management and prognosis of glioblastomas?
Surgical with postoperative chemotherapy and/or radiotherapy Dexamethasone is used to treat the oedema
Prognosis is poor ~ 1 year
What are the second most common primary brain tumours?
Meningiomas
What are meningiomas?
Typically BENIGN, extrinsic tumours of the CNS
They arise from the arachnoid cap cells of the meninges and are typically located next to the dura
Cause symptoms by compression rather than invasion
What are the histological features of meningiomas?
Spindle cells in concentric whorls and calcified psammoma bodies
What is the management plan for a meningioma?
Investigation is with CT (will show contrast enhancement) and MRI
Treatment will involve either observation, radiotherapy or surgical resection
What is the most common primary brain tumour in children?
Astrocytoma
What are the common CNS tumours?
60% = Glioma and metastatic disease
20% = Meningioma
10% = Pituitary lesions
What are some of the common features of CNS tumours?
Headache or vomiting (raised intracranial pressure)
Epilepsy (focal or generalized)
Focal neurological deficits (dysphagia, hemiparesis, ataxia, visual field defects, cognitive impairment)
Personality change
How to symptoms of CNS tumours present depending on site of tumour?
Tumours arising in right temporal and frontal lobe may reach considerable size before becoming symptomatic
Whereas tumours in the speech and visual areas will typically produce early symptoms
What is the diagnostic investigation of choice for CNS tumours?
MRI scan - provide best resolution
What is the management plan for CNS tumours?
Usually surgery - even if tumour cannot be completely resected conditions such as rising ICP can be addressed with tumour debulking → survival and quality of life prolonged
Curative surgery can usually be undertaken with lesions such as meningiomas
*Gliomas have a marked propensity to invade normal brain and resection of these lesions is nearly always incomplete (hence poor prognosis)
What are vestibular schwannomas?
Previously termed acoustic neuroma
Benign tumour arising from the eighth cranial nerve (vestibulocochlear nerve)
Often seen in the cerebellopontine angle
It presents with hearing loss, facial nerve palsy (due to compression of the nearby facial nerve) and tinnitus
What are bilateral vestibular schwannomas associated with?
Neurofibromatosis type 2
What are cholangiocarcinomas?
Bile duct cancer
How can cholangiocarcinomas be divided?
On their location in the biliary tree:
1. Intrahepatic
2. Extrahepatic (perihilar or distal)
What is the main risk factor for cholangiocarcinoma?
Primary sclerosing cholangitis
What is Primary sclerosing cholangitis?
Biliary disease of unknown aetiology characterised by inflammation and fibrosis of intra and extra-hepatic bile ducts
Closely associated with Ulcerative Colitis
What are some other risk factors for Cholangiocarcinoma?
Age > 50 years
Cholangitis
Choledocholithiasis (gall stones)
Structural disorders of the biliary tract e.g. bile duct adenoma
Ulcerative colitis
Non-specific cirrhosis
Alcoholic liver disease
HIV
Hepatitis B and C
What are the features of cholangiocarcinoma?
Persistent biliary colic symptoms
Associated with anorexia, jaundice and weight loss
A palpable mass in the right upper quadrant (Courvoisier sign)
Periumbilical lymphadenopathy (Sister Mary Joseph nodes) and left supraclavicular adenopathy (Virchow node) may be seen
Obstructive jaundice = dark urine and pale stools
What is the triad seen in Acute Cholangitis?
Fever, jaundice and right upper quadrant pain
What are the appropriate investigations for cholangiocarcinomas?
Raised CA 19-9 levels (often used for detecting cholangiocarcinoma in patients with PSC)
Bloods e.g. bilirubin, LFTs
Abdominal USS: intrahepatic cholangiocarcinoma may be seen as a mass lesion
ERCP: filling defect or area of narrowing will be seen if a tumour is present
What is the management plan for cholangiocarcinoma?
Surgical resection offers the only potential cure for early-stage disease
Chemotherapy may have a positive effect on overall survival of patients following resection of intrahepatic cholangiocarcinoma
Liver transplant is indicated in a small subset of patients
What is colorectal carcinoma?
- Malignancy of the large bowel
- The third most common type of cancer in the UK and the second most cause of cancer deaths
What is the aetiology of colorectal carcinoma?
Currently thought to be three types:
1. Sporadic (95%)
2. Hereditary non-polyposis colorectal carcinoma (HNPCC, 5%)
3. Familial adenomatous polyposis (FAP, <1%)
What are the most common risk factors for colorectal carcinoma?
- Age
- Genetics (even in sporadic cases, FH is important)
- Inflammatory bowel disease
- Lifestyle/ environmental factors
What is hereditary non-polyposis colorectal carcinoma (HNPCC)?
- An autosomal dominant condition: most common form of inherited colon cancer
- Around 90% of patients develop cancers, often of the proximal colon, which are usually poorly differentiated and highly aggressive
- At risk of other cancers: endometrial cancer
What is familial adenomatous polyposis (FAP)?
- A rare autosomal dominant condition which leads to the formation of hundreds of polyps by the age of 30-40 years
- Patients inevitably develop carcinoma
- It is due to a mutation in a tumour suppressor gene called adenomatous polyposis coli gene (APC), located on chromosome 5
- Also at risk from duodenal tumours
- A variant of FAP called Gardner’s syndrome can also feature osteomas of the skull and mandible, retinal pigmentation, thyroid carcinoma and epidermoid cysts on the skin
What are the common locations for colorectal carcinomas?
- Rectal: 40%
- Sigmoid: 30%
- Ascending colon and caecum: 15%
- Transverse colon: 10%
- Descending colon: 5%
What are the features of a left sided colon and rectum carcinoma?
- Change in bowel habit: increased frequency, looser stools
- Rectal bleeding or blood/mucous mixed in with stools
- Rectal masses may also present as tenesmus: sensation of incomplete emptying after defecation
What are the features of a right sided colon carcinoma?
Later presentation:
1. Symptoms of anaemia
2. Weight loss and non- specific malaise
2. More rarely, lower abdominal pain
How can colorectal carcinoma present in an emergency?
- 20% of cases
- Pain and distension caused by large bowel obstruction, haemorrhage or peritonitis as a result of perforation
What are the signs of colorectal carcinoma on examination?
- Left sided: abdominal mass, low-lying rectal tumours may be palpable on rectal examination
- Right sided: anaemia may be only sign
- Metastatic disease: hepatomegaly, shifting dullness of ascites
What are the referral guidelines for colorectal carcinoma for the 2 week pathway?
- Patients ≥ 40 years with unexplained weight loss AND abdominal pain
- Patients ≥ 50 years with unexplained rectal bleeding
- Patients ≥ 60 years with iron deficiency anaemia OR change in bowel habit
When else should a patient be referred to the 2WW pathway for colorectal carcinoma?
Tests show occult blood in their faeces (FIT)
When should a referral to the 2WW pathway be considered?
- There is a rectal or abdominal mass
- There is an unexplained anal mass or anal ulceration
- Patients < 50 years with rectal bleeding AND any of the following unexplained symptoms/findings:
a. abdominal pain
b. change in bowel habit
c. weight loss
d. iron deficiency anaemia
What is the faecal immunochemical test (FIT)?
National screening programme offering screening every 2 years to everyone aged 60 to 74 years in England (if over 74 years may request screening)
1. Eligible patients are sent the tests through the post
2. A type of faecal occult blood (FOB) test which uses antibodies that specifically recognise human haemoglobin (Hb)
3. Used to detect, and can quantify, the amount of human blood in a single stool sample
4. Patients with abnormal results are offered a colonoscopy
When is a FIT test recommended to patients outside of the screening programme?
If patients have new symptoms but do not fit the 2WW referral criteria:
1. Patients ≥ 50 years with unexplained abdominal pain OR weight loss
2. Patients < 60 years with changes in their bowel habit OR iron deficiency anaemia
3. Patients ≥ 60 years who have anaemia even in the absence of iron deficiency
What is the investigation that all patients with suspected colorectal cancer receive?
Colonoscopy (alongside further blood tests and stool tests
What is the sign of colorectal carcinoma on barium enema?
Apple core stricture (stenosing annular carcinoma)
What are the staging investigations for colorectal carcinoma?
- CT of the chest/ abdomen and pelvis: may show colonic wall thickening, enlarged lymph nodes, liver metastases, ascites, lung secondaries
- The entire colon should have been evaluated with colonoscopy or CT colonography
- Patients whose tumours lie below the peritoneal reflection should have their mesorectum evaluated with MRI
What is the management of colorectal carcinoma?
MDT approach- nearly always treated with surgery:
1. Stents, surgical bypass and diversion stomas may all be used as palliative adjuncts
2. Resectional surgery is the only option for cure in patients with colon cancer
3. When a colonic cancer presents with an obstructing lesion; the options are to either stent it or resect
What is the management of rectal cancer?
Tumours located in the rectum can be surgically resected with either an anterior resection or an abdomino-perineal excision of rectum (APER), involvement of the cirumferential resection margin carries a high risk of disease recurrence
What are the types of resection for colorectal cancer depending on the site of the tumour?
- Caecal, ascending or proximal transverse colon:
a. Right hemicolectomy
b. Ileo-colic anastamosis - Distal transverse, descending colon:
a. Left hemicolectomy
b. Colo-colon anastamosis - Sigmoid colon:
a. High anterior resection
b. Colo-rectal anastamosis - Upper rectum:
a. Anterior resection (TME)
b. Colo-rectal anastamosis - Low rectum:
a. Anterior resection (Low TME) b. Colo-rectal anastamosis
(+/- Defunctioning stoma) - Anal verge:
a. Abdomino-perineal excision of rectu
b. No anastamosis needed
What is Hartmann’s procedure and when is it used in the management of colorectal carcinoma?
Defintion: when resection of the sigmoid colon is performed and an end colostomy is fashioned
Indication:
1. In an emergency setting where the bowel has perforated
2. The risk of an anastomosis is much greater, particularly when the anastomosis is colon-colon
3. In this situation, an end colostomy is often safer and can be reversed later
What is a colorectal resection?
- The only option for cure in patients with colon cancer
- Is tailored to the patient and the tumour location
- The lymphatic drainage of the colon follows the arterial supply and therefore most resections are tailored around the resection of particular lymphatic chains (e.g. ileo-colic pedicle for right sided tumours)
- Some patients may have confounding factors that will govern the choice of procedure, e.g. a tumour in a patient from a HNPCC family may be better served with a panproctocolectomy rather than segmental resection
What decision must be made following colorectal resection regarding restoration of continuity?
Anastamosis (surgical connection between two structures) or end stoma
What are the technical factors regarding anastamosis healing in colorectal resections?
Adequate blood supply, mucosal apposition and no tissue tension
In certain situations (e.g. surrounding sepsis, unstable patients, inexperienced surgeons) it may be better to opt for an end stoma
What are stomas?
Involve bringing the lumen or visceral contents onto the skin, most commonly the bowel
What stoma should be used for the right side of the abdomen, specifically the RIF?
- Ileostomy: can be loop or end depending on location
- Should be spouted so that their irritant contents are not in contact with the skin
- Output = liquid
What stoma should be used for the left side of the abdomen?
- Colostomy: end or loop, again depends on location and colonic segment used
- Should be flushed (no need for spouted because contents are less irritant)
- Output = solid
What is important regarding stoma siting?
- Will ultimately influence the patient’s ability to manage their stoma and the risk of leakage
- Leakage of stoma contents and subsequent maceration of the surrounding skin can rapidly progress into a spiralling loss of control of stoma contents
- Ideally, the site of the stoma should be discussed with the patient prior to surgery
What is Virchow’s triad?
- Venous stasis
- Vessel wall injury
- Blood hypercoagulability
What is deep vein thrombosis (DVT)?
Formation of a thrombus within the deep veins (most commonly of the calf or thigh) which may result in impaired venous blood flow and consequent leg swelling and pain
What are the risk factors for DVT?
- Oral contraceptive pill
- Surgery
- Prolonged immobility
- Long bone fractures
- Obesity
- Pregnancy
- Dehydration
- Smoking
- Polycythaemia
- Anti-phospholipid syndrome
- Thrombophilia disorders (e.g. protein C deficiency)
- Active malignancy
What is the epidemiology for DVT?
Common, especially in hospitalised patients- yearly incidence of approximately 1 in every 1000 adults
What are the presenting symptoms of DVT?
- Asymptomatic or lower limb swelling or tenderness
- May present with signs/ symptoms of a pulmonary embolus (sudden onset dyspnoea, chest pain)
What are the signs of DVT on physical examination?
Examine for swelling, calf tenderness:
1. Severe leg oedema (usually unilateral)
2. Dilated superficial veins over foot and leg
3. Cyanosis (phlegmasia cerulea dolens) is rare
*Respiratory examination for signs of a pulmonary embolus: Sudden onset dyspnoea, cough, haemoptysis and pleuritic chest pain
What should be performed in any patient with suspected DVT?
A two-level DVT Wells score
What is the Two-level DVT Wells score?
- Active cancer (treatment ongoing, within 6 months, or palliative) = 1
- Paralysis, paresis or recent plaster immobilisation of the lower extremities= 1
- Recently bedridden for 3 days or more or major surgery within 12 weeks requiring general or regional anaesthesia = 1
- Localised tenderness along the distribution of the deep venous system = 1
- Entire leg swollen = 1
- Calf swelling at least 3 cm larger than asymptomatic side = 1
- Pitting oedema confined to the symptomatic leg = 1
- Collateral superficial veins (non-varicose) = 1
- Previously documented DVT = 1
- An alternative diagnosis is at least as likely as DVT = -2
How is the Two-level DVT Wells score interpreted for DVT likelihood?
DVT likely: 2 points or more
DVT unlikely: 1 point or less
What is the next step in management for a patient who scored 1 point or less on the two-level DVT Wells score?
DVT ‘unlikely’:
1. Perform a D dimer score within 4 hours
2. If not, interim therapeutic anticoagulation should be given until the result is available, but still performed within 24 hours
What should be the next step in management if a D dimer result is negative in a suspected DVT?
Then DVT is unlikely and alternative diagnoses should be considered
What should be the next step in management if a D dimer result is positive in a suspected DVT?
A proximal leg vein ultrasound scan should be carried out within 4 hours (if delayed then give interim therapeutic anticoagulation)
What are d-dimer tests in the investigation of DVTs?
- NICE recommend either a point-of-care (finger prick) or laboratory-based test
- Age-adjusted cut-offs should be used for patients > 50 years old
What is the next step in management for a patient who scored 2 points or more on the two-level DVT Wells score?
DVT is ‘likely’:
1. A proximal leg vein ultrasound scan should be carried out within 4 hours
2. If not, interim therapeutic anticoagulation should be given until the result is available, but still performed within 24 hours
What should be the next step in management if a proximal leg vein ultrasound is positive in a suspected DVT?
Then a diagnosis of DVT is made and anticoagulant treatment should start
What should be the next step in management if a proximal leg vein ultrasound is negative in a suspected DVT?
A D-dimer test should be arranged: a negative scan and negative D-dimer makes the diagnosis unlikely and alternative diagnoses should be considered
What should be the next step in management if a proximal leg vein ultrasound is negative in a suspected DVT but the D dimer is positive?
- Stop interim therapeutic anticoagulation
- Offer a repeat proximal leg vein ultrasound scan 6 to 8 days later
What is meant by interim therapeutic anticoagulation in suspected DVT?
Used to be LMWH, now a direct oral anticoagulant (DOAC) such as apixaban or rivaroxaban
What is the management of a confirmed DVT?
- NICE now advocate using a DOAC once a diagnosis is suspected, with this continued if the diagnosis is confirmed
- All patients should have anticoagulation for at least 3 months
- Then if the VTE was provoked, the treatment can be stopped
- If the VTE was unprovoked, then treatment is typically continued for up to 3 further months (i.e. 6 months in total)