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Hospital residence > Radiotherapy pt.3 > Flashcards

Radiotherapy pt.3 Flashcards

1
Q

What are different tumor volumes involved in radiotherapy planning?

A

GTV: Gross tumor volume (clinical)
CTV: Clinical tumor volume (clinical)
PTV: Planning target volume (geometric
Dosimetric volumes (Treated volume and irradiated volume)

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2
Q

What does CTV represent?

A

Represents the microscopic tumor cells, the volume where we are supposed to find the microscopic cells (depends on anatomy, pathology, and site of local recurrences) which can be found
- around the macroscopic tumor–> after surgical removal and pathology examination
- Draining lymph nodes–> Requires knowledge of anatomy and physiology
- Sites of local recurrence –> Follow up

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3
Q

Rectal cancer treatment

A

Preoperative RT+CT followed by surgery which includes total mesorectal excision

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4
Q

Microscopic cancer foci in lung cancer

A
  • In lung adenocarcinomas 35% of the miscroscopic foci is found in the area of 0.8 cm around the main disease (95% of microscopic tumoral cells)
  • In squamous lung tumors they are found in a range of 0.6cm, thus influencing the
    radiotherapy approach:
  • Squamous → 0.6 cm margin
  • Adenocarcinoma → ≥6 mm margin
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5
Q

Microscopic cancer foci in rectal cancer

A

Microscopic cancer foci are found in the mesorectum round 40% of cases and in the outter region of the mesorectom in 25% of cases
Distal tumor deposits in the mesorectal fat 3 cm from the cancer: 6.5%
80% of nodes at the level of the tumor

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6
Q

Where does the rectum drain its lymph?

A

70% Superior lymph Nodes (along the SRA to the inferior mesenteric nodes)
30% Lateral Lymph Nodes (internal Iliac, obturator)

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7
Q

What is planning target volume?

A

The volume that takes into account target movements:
- Patient Set up. positioning
- Tumor and Organ motion (e.g. breathing, bladder filling)

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8
Q

What is image guided radiotherapy?

A

Imaging devices mounted on the treatment machines to visualize:
- The Patient poisition (set-up)
- The TARGET/organ at risk position

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9
Q

What is portal imaging?

A

Displays the position of the fields in relation to the bone

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10
Q

What do the CTV-PTV margins depend on?

A

The CTV-PTV margins DEPENDS on:
- IGRT SYSTEM used and the
- FREQUENCY of imaging acquisition during treatment
- implemented CORRECTIONS

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11
Q

What is the treated volume?

A

Treated Volume (TV):
- Is volume of normal tissue surrounded by the prescribed (iso)dose
- TV > PTV

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12
Q

What do the dimensions of treated volume depend on?

A

The dimension of the TV depends on the RT technique used. The more the dose is shaped around the target the smaller the TV is

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13
Q

What is the irradiated volume?

A
  • The Volume surrounded by the 50% (iso)dose
  • Represents the normal tissue at risk of second tumor
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14
Q

What imaging is used for rectal cancer staging?

A

MRI for tumor and local nodes

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15
Q

What is considered curable and non curable for rectal cancer?

A
  • Stage 1-3 are curable (M0, no nodal involvement until stage 3)
  • Stage 4 is uncurable (Any T, Any N, M1a-b)
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16
Q

What is the treatment for different stages of rectal cancer?

A

Stage 1:: local excision
Stage 2: Surgery
Stage 3: neo RT- Surgery + CT (if high risk factors)
Stage 4: Chemo + Radiotherapy

17
Q

What is total mesorectal excision?

A

en bloc removal of the rectum together with the mesorectal fat column

18
Q

Radiotherapy modality for rectal cancer

A

Short course ((downstaging not needed)) of 25 GY (5Gy per day for 5 days) followed by immediate (2-3 days) surgery
or
Long course (downstaging needed) of 45-50 Gy (1.8-2Gy per day for 5 weeks) then delayed (6-8 weeks) surgery

19
Q

Locally advanced treatment for rectal cancer

A

Neoadjuvant radiotherapy followed by surgery followed by chemo(if risk factors are present)

20
Q

What is the mesorectum?

A

Fibrovascular fatty tissue containing lymphatic drainage and nodes surrounding posterior and lateral rectum enveloped by the mesorectal fascia

21
Q

Totality of total mesorectal excision in rectal cancer

A

Residual distal mesorectal fat in 50% of patients who underwent TME

22
Q

Where is local recurrence found in rectal cancer patients?

A

The majority of RL in the posterior lower 2/3 of the pelvis

23
Q

Arteries supplying rectum

A

Superior, middle, and inferior rectal arteries

24
Q

When should inguinal nodes be removed in rectal cancer?

A
  • Are not in the drainage of rectal cancer
  • Must be included in case of anal canal and anal sphincter infiltration or anterior organs infiltration (vagina, prostate)
  • Positive inguinal nodes
  • Massive invasion of external anal sphincter
  • cT4 with infiltration of the lower third of the vagina
25
Q

Damage to pudendal nerve symptoms

A

Pain, sexual dysfunction, urinary dysfunction

26
Q

Risk of recurrence of rectal cancer in ischiorectal fossa

A

LOW risk of recurrence in TME era:
Risk of LR 1%
Involved in 10% of patients with LR

Recurrences in IRF due to tumor spillage during inadequate dissection

27
Q

Need for guidelines for radiation oncologists

A

The use of guidelines and atlas for delineation Increases consistency between radiation oncologists

28
Q

What is the anterior wall of the ischiorectal fossa represented by?

A

The anterior wall is represented by the inferior fascia of urogenital diaphragm (dàiafram) and by the superficial transverse perineal muscle

29
Q

What is the posterior wall of the ischiorectal fascia represented by?

A

The posterior wall is represented mainly by the gluteus maximus and by sacrotuberous ligament

30
Q

what is the ischio-rectal fossa and its borders

A

Fatty triangular area bounded by the levator ani and the external anal sphincter medially
By the obturator internus muscle and the ischial tuberosity laterally
and the skin inferiorly

31
Q

Where are ingiunal nodes found?

A

In an area bounded posteriorly by triangle formed by ilio-psoas, pectineus, sartorius and abductor longus muscles

32
Q

What is the 5 year survival when N+ extra mesorectal

A

Around 40%

33
Q

What is the presacral space and its inclusion in surgery?

A

Virtual space which is included in the delineation of the mesorectum and the lateral lymph node subsite

The neuroforamina should not be included, unless there is direct infiltration or close proximity of the tumor

34
Q

What are lateral lymph nodes in rectum divided into?

A

POSTERIOR Lateral Nodes: Internal Iliac Nodes
ANTERIOR Lateral Nodes: Obturator Nodes

35
Q

When are posterior lateral nodes included?

A

Include always in the CTV

36
Q

When are anterior lateral nodes included in resection?

A

Include in case of:
Positive internal iliac nodes
cT4
N2

37
Q

When should external iliac nodes be included in resection?

A

Include in case of:
cT4
Positive anterior lateral lymph nodes (obturator nodes)

Hospital residence (8 decks)

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