Radiotherapy pt.3

Question 1

What are different tumor volumes involved in radiotherapy planning?

Answer 1

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

Question 2

What does CTV represent?

Answer 2

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

Question 3

Rectal cancer treatment

Answer 3

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

Question 4

Microscopic cancer foci in lung cancer

Answer 4

• 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

Question 5

Microscopic cancer foci in rectal cancer

Answer 5

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

Question 6

Where does the rectum drain its lymph?

Answer 6

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

Question 7

What is planning target volume?

Answer 7

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

Question 8

What is image guided radiotherapy?

Answer 8

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

Question 9

What is portal imaging?

Answer 9

Displays the position of the fields in relation to the bone

Question 10

What do the CTV-PTV margins depend on?

Answer 10

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

Question 11

What is the treated volume?

Answer 11

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

Question 12

What do the dimensions of treated volume depend on?

Answer 12

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

Question 13

What is the irradiated volume?

Answer 13

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

Question 14

What imaging is used for rectal cancer staging?

Answer 14

MRI for tumor and local nodes

Question 15

What is considered curable and non curable for rectal cancer?

Answer 15

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

Question 16

What is the treatment for different stages of rectal cancer?

Answer 16

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

Question 17

What is total mesorectal excision?

Answer 17

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

Question 18

Radiotherapy modality for rectal cancer

Answer 18

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

Question 19

Locally advanced treatment for rectal cancer

Answer 19

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

Question 20

What is the mesorectum?

Answer 20

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

Question 21

Totality of total mesorectal excision in rectal cancer

Answer 21

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

Question 22

Where is local recurrence found in rectal cancer patients?

Answer 22

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

Question 23

Arteries supplying rectum

Answer 23

Superior, middle, and inferior rectal arteries

Question 24

When should inguinal nodes be removed in rectal cancer?

Answer 24

• 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

Question 25

Damage to pudendal nerve symptoms

Answer 25

Pain, sexual dysfunction, urinary dysfunction

Question 26

Risk of recurrence of rectal cancer in ischiorectal fossa

Answer 26

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

Question 27

Need for guidelines for radiation oncologists

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

what is the ischio-rectal fossa and its borders

Answer 30

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

Question 31

Where are ingiunal nodes found?

Answer 31

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

Question 32

What is the 5 year survival when N+ extra mesorectal

Answer 32

Around 40%

Question 33

What is the presacral space and its inclusion in surgery?

Answer 33

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

Question 34

What are lateral lymph nodes in rectum divided into?

Answer 34

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

Question 35

When are posterior lateral nodes included?

Answer 35

Include always in the CTV

Question 36

When are anterior lateral nodes included in resection?

Answer 36

Include in case of: Positive internal iliac nodes cT4 N2

Question 37

When should external iliac nodes be included in resection?

Answer 37

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