radiotherapy planning for vulvar cancer 2D

1. RT planning for Vulvar cancer
By:Gebrekirstos H,MD ,COR-III
Moderator: Dr Wondemagegnhu T, Consultant
Oncologist
AAU –CHS,RT center
September 9, 2020

2. Out lines of presentation
• Introduction
• Anatomy
• Lymphatic spread
• Investigations
• Staging
• Indications
• Patient position, immobilization and simulation
• Target volume
• Field arrangement
• RT dose
• OAR
• Toxicities

3. Introduction
• Vulvar ca is rare(3-5% of all female genital
tract malignancies).
• Pts commonly present with early stage T1,T2,
N0 SCC, & is disease of elderly, mean age70
yrs.
• Due to rarity & diversity in presentation, few
physicians or smaller centers can build up
adequate expertise in treating this disease

4. Introduction
• In 1930s, radical vulvectomy & inguinofemoral
LND became standard Rx for SCC of the vulva
• Unilateral or bilateral inguino-femoral LND is
recommended if tumor invades >1 mm & is
chosen according to laterality of the primary.
• If groin nodes are involved at surgery, RT is
given to the inguino-femoral and pelvic LNs

5. Introduction
• This surgery, while providing a high probability
of cure, was associated with considerable
disfigurement &morbidity.
• LN met is the single most important
prognostic factor & results in 50 % reduction
in long-term survival.

6. Anatomy of the vulva
• The vulva consists of the mons pubis, labia majora,
labia minora, clitoris and Bartholin’s glands
• Most tumours of the vulva involve the labia majora.
• Vulvar malignancy originates from:
 70% -labia majora & minora,
 15% -clitoris
 5% -perineum & fourchette
 5% -prepuce Bartholin glands & urethra
 5%-too extensive to classify at presentation

8. Lymphatic spread
• Lymphatic drainage is specific to the location
of a vulvar lesion.
• Superficial inguinofemoral LNs are the 1st
echelon, followed by deep inguinofemoral LNs
• Well-lateralized lesions, met to ipsilateral
inguinofemoral LNs
• Occasionally there is direct spread to the
pelvic nodes via internal pudendal vessels.

9. Lymphatic spread
• PE alone is inaccurate to assess LN met
• Frequency of inguinal LNs met in surgically
staged pts ranges from 6-50%.
• GOG protocol 36, Homesley reported that
24% of the pts with cLN0, found to have LN
met on final pathology.

11. Lymphatic spread
• Inguinal LN met is strong predictor pelvic LN met.
• Homesley et al(GOG study ) in pts with ILN+,
incidence of pelvic LN met was 28%.
• Pelvic LN met is currently staged as IVB, but
¼-1/3 pts are potentially curable, & aggressive
local therapy is indicated.
• From MD Anderson series, 5-yrs OS with involved
pelvic LN was 43% with aggressive local therapy.

12. Investigation
• Examination of vagina, cervix, perianal skin &
anal canal is particular importance
in order to delineate the extent of disease
 to identify synchronous lesions(multicenteric
nature)
• Special attention to the inguinofemoral basin
• EUA , cystoscopy & proctoscopy as indicated
• HPV & PICT
• Pelvic MRI (aid in planning of Surgery or RT)

13. Investigation
• Clinically or radiographically detected inguinal
LNs may be evaluated with US-guided FNAC,
though –ve result does not rule out met
• Sensitivities of all available imaging modalities
are insufficient to omit surgical evaluation in
women with a high risk of nodal involvement.
• Sentinel node biopsy is being investigated &
results correlated with full inguino-femoral
LND

16. Indication of RT
• The introduction of RT(definitive or adjuvant)
setting was based on:
(1) better understanding of risk groups for local&
regional recurrence
(2) acknowledgment that RT is effective in the Rx of
SCC arising in other sites
(3) efforts to ↓ treatment morbidity compared
with that of radical surgery
(4) wish to improve outcomes in pts with advanced
disease

17. Indications
I) Adjuvant RT/CCRT(should be with in 6-8 wks of surgery)
-to primary
 positive margin(non candidate for re-resection)
 -LVSI
 -close margin(<8mm) classic indications
 -depth of invasion >5mm
 Groin involvement –is relative indication to the vulva
-to LN site
 cLN+
 two or more pLN+
 ECE
II) Definitive CCRT-
-assumed unresectable afeter RT
-not fit for surgery
-pt refusal surgery
III) Pre operative –locally advanced
IV) Palliative RT(bleeding, pain, discharge)
No role of RT for VIN, which represents a field change and is treated with surgery

18. Pt position, immobilization & simulation
• Pt is positioned supine with frog leg position
• “Frog-leg” position helps minimize dose to the
medial thigh and groin folds.
• Although this may be less important if IMRT
used.
• Advanced immobilization devices like alpha
cradle or vacuum cushion device can be
considered.

19. Pt position, immobilization & simulation

20. Pt position, immobilization & simulation
• CT/MR-based 3D planning is essential to establish
the location, extent & depth of the inguinal &
pelvic nodal basins, as well as the primary.
• Both IV & PO contrast should be used if possible
to identify vascular structures for nodal
contouring & bowel at risk.
• At the time of simulation, markers(wire) should
be placed on the primary, LNs, urethra, clitoris
,anus and scars to document the extent.

21. Pt position, immobilization & simulation
• Pts should be simulated and treated with
consistent bladder and rectal filling(i.e.,
comfortably full bladder and empty rectum).
• Bolus is often critical over the vulva & groins,
which may be applied at the time of simulation or
applied virtually at the time of treatment
• CT is especially useful for measuring depth of
lymph nodes when selecting electron beam
energies.

22. Target volume
• Best defined by physical exam & CT based
planning
• When nodal RT is indicated following surgery ,
CTV includes the remaining vulva, inguino-
femoral LN, distal external &internal iliac LNs.
• Inguinal, femoral and iliac blood vessels can
be used as surrogates for nodes & 7 mm
margin around vessels to define CTV-N.

24. Filed arrangement
• Post surgery -nodal
1) Superior: should not be lower than bottom of
sacro iliac joint or higher than L4/L5 junction.
-Sholud be extend as horizontal line at AIIS(anterior
inferior iliac spine)
• If pelvic LN met, it should be extended to the
L3/L4 interspace (2cm above the involved LN) to
cover the common iliac nodes
• In general, extend the node Rx volume one nodal
echelon proximal to the level of clinical involved,
if no major medical contraindications

25. Filed arrangement
2) Laterally:
a) For AP-include AIIS(ie, medial 2/3 of inguinal
ligament) or further if clips suggest more
lateral involvement.
b) PA field: 2 cm beyond the bony pelvis

26. Filed arrangement
3) Caudal border-intertrochanteric line of femur
or 1.5-2cm distal saphenofemoral junction.
• when RT to the LNs(inguinlal & pelvic), it is
wise to include the vulvar tumor bed
&adjacent perineal skin, so the lower border
should be 2cm distal to lower part of vulva
• because of the substantial risk of recurrence in
this area when midline shielding employed.

27. Filed arrangement
• Critical to the success of elective groin
irradiation is delivery of dose to appropriate
depth in tissue.
• Depth of deep femoral nodes is defined as the
depth of the femoral artery as it passes
beneath the inguinal ligament.
• This will be most accurately measured by CT

30. Field arrangement
• Pre surgery RT is considered if:
1) surgical margins are anticipated to be
inadequate
2) Initial surgery expected to compromise the
function of important tissues (anus, urethra,
clitoris, bladder)
3) Fixed, matted or ulcerated groin nodes
• In this histopathologic status of suspicious groin
should be assessed by FNA or excisional biopsy
before Rx

31. Field arrangement
• Target volume is determined in a similar
fashion to PORT, with exception of larger
pelvic node volume if the primary tumor
extends to involve :
middle or upper vagina
proximal urethra
bladder
rectum

32. Filed arrangement
• Techniques to ↓ dose to the femoral heads while
delivering an adequate dose to the inguinal nodes:
I) Use wide AP that includes pelvic & inguinal areas &
narrow PA covering only pelvis( spares femora heads)
• The photon fields are weighted equally, and the
inguinal dose is supplemented by separate AP electron
fields matched to the pelvic field
• Bolus material should be used to ensure adequate dose
to the superficial portions of the groin

33. Filed arrangement
II) wide AP & narrow PA,with a partial transmission
central block (in the AP field), (associated with high
rate of central recurrence in stage III& IV)
• The desired dose at a specified depth is delivered to
the inguinal nodes through the AP field.
• Advantages:
-Eliminates the dosimetric problems of photon/electron
field matching
-Decrease potential for daily setup variation
• Disadvantage:
-Difficult to design of a precise partial transmission block

35. Filed arrangement
• III) Matched AP/PA fields to include the primary &
pelvic nodes and treating the groins through
separate anterior electron fields.
• Advantage :
- relatively easy setup
• Disadvantage
-difficult to ensure an adequate dose at the match
line, particularly when the match line is over
gross disease.

37. Filed arrangement
• IV) Modified segmental boost technique using
multileaf collimators with a single-isocenter technique
& wide AP field to cover the vulva, pelvis, and groins &
narrow PA field to cover the vulva and pelvis.
• The supplemental anterior photon groin fields are
angled such that the central axis is coplanar with the
divergence from the PA field.
• The medial blocking of the groin fields is designed to
match the divergence from the PA field.
• This technique provides a more homogeneous dose
distribution & is easier to reproduce on a daily basis

40. RT doses
A) Vulvar primary
Post operative
I) Margin negative=45-50.4Gy
II) Close margin= 56-59.4Gy
III) Positive margin/microscopic residual=56-
65Gy
Definitive -60-70Gy

41. RT doses
• Nodal region
I) Uninvolved nodal region- 45-50.4Gy
II) Resected nodal region-50.4Gy
III) Resected nodal region with ECE-60-65 Gy
IV) Gross LN≤1cm-54Gy
V) Gross LN>1cm-65-70Gy

42. III) Palliative treatment
• Photon or electron therapy
20 Gy in 5 daily fractions given in 1 week.
30 Gy in 10 daily fractions given in 2 weeks.

43. Toxicity
• Vulvar skin reaction
• Urinary frequency and dysuria
• proctitis and diarrhoea
• Late vulval fibrosis and atrophy
• Lymphedema (occur in 30% pts when
inguinofemoral surgery & RT are combined
• Urethral stenosis as a late effect
• Femoral head necrosis -11% risk of necrosis at 5
yrs, if opposing AP/PA beams used in elderly pts

44. OAR

45. Thank you!
• Happy Ethiopian New year, 2013