HDR brachytherapy for Non-Melanoma Skin cancers

1. INTERVENTIONAL RADIOTHERAPY
(BRACHYTHERAPY) IN NON-
MELANOMA SKIN CANCERS (NMSC)
Ali Bagheri M.D
Assistant Professor in Radiation Oncology & Interventional Radiotherapist
Brachytherapy Ward of Golestan Hospital
Department of Radiation Oncology
Ahvaz Jundishapur University of Medical Sciences

2. POSSIBLE INDICATIONS OF
RADIOTHERAPY IN NMSC
• Primary treatment of tumor after biopsy.
• Adjuvant treatment of excised lesions with close or
positive surgical margins.
• High risk of recurrence after surgery.
• Treatment of recurrent tumors.

3. EVIDENCE FOR DEFINITIVE
RADIOTHERAPY

4. SURGERY OR RT?
• The likelihood of cure is similar after surgery or
radiotherapy.
• Selection of one modality over another is based on:
• Function
• Cosmesis
• Age of the patient
• Convenience
• Cost
• Availability of appropriate RT equipment
• Wishes of the patient

5. SURGERY
• Free skin location
• These lesion usually are easily
excised with a good cosmetic
result and minimal
inconvenience.
• Young patients
• The late effects of irradiation
progress gradually with time and,
with very long-term follow-up,
may be associated with a
suboptimal cosmetic result
compared with resection and
reconstruction.
• Eyelid, external ear, or nose
location
• Resection may result in a
significant cosmetic deformity
and necessitate complex
reconstruction.
• Older patients
• Because of a limited life
expectancy and higher risk for
a perioperative complication.
RADIOTHERAPY
SELECTION OF TREATMENT
MODALITY

6. THE CONCEPT OF
INTERVENTIONAL
RADIOTHERAPY

7. PHYSICS OF
BRACHYTHERAPY
• Brachytherapy is derived from
the ancient Greek
word brachy with means
“short distance”.
• This technique consists of
placing sealed radioactive
sources very close to or in
contact with the tumor
tissue.
• Because the absorbed dose
falls off rapidly with
increasing distance from the
sources (thanks to the inverse
square law), high doses may
be delivered safely to a
localized target region over a
short time.
• This modality is the most
conformal type of radiation
therapy.

8. EQUIPMENT FOR HIGH DOSE
RATE (HDR) BRACHYTHERAPY
Remote After Loader
Radioactive HDR
Source (At the tip of
the cable)
Flexible Plastic
Catheter
• Remote after loaders are computer controlled robots that contain
the HDR radioactive source.
• Staff can remotely control the machine from a separate
observation room to deliver the HDR source through catheters to
the patient body.
• This ensures that healthcare professionals delivering treatment

9. 100%
50%
25%
10%
Isodose Line
Dose/Fraction
(Gy)
Total PD (Gy) Total BED (%)
PD Decrease
(%)
BED Decrease
(%)
100% 4 40 93.33 - -
50% 2 20 33.33 50 64
25% 1 10 13.33 75 86
10% 0.4 4 4.5 90 95
RADIOBIOLOGICADVANTAGEOF
BRACHYTHERAPY
For example if 40 Gy is
prescribed in 10 Fractions
(Physical Dose - PD) and
assuming an Alpha/Beta
ratio of 3 for calculating the
Biologic Equivalent Dose
(BED).

10. Lower Radiation
Doses to Nearby
Normal Tissues
Enables Safely
Delivering of High
Radiation Doses to
the Tumor in Each
Fraction
Shorter Total
Treatment Time
Less Tumor cell
Repopulation
During Treatment
Less Total Physical
Doses of Radiation
is Required for
Tumor Eradication
Higher
Biologic
Effect of
Radiation
STEEPDOSEGRADIENTIN
BRACHYTHERAPY

11. SURFACE (WITH THE AID
OF A CUSTOM MOLD) INTERSTITIAL
SKIN BRACHYTHERAPY TYPES

12. SURFACE BRACHYTHERAPY
(+CUSTOM MOLD)
• Brachytherapy catheters are
positioned in 2-5mm distance
above the skin using a custom
mold.
• Indication:
• Superficial lesions with maximum
target volume depth of 4-5 mm.
• The limiting factor of treatment
at greater depth is the resulting
higher skin- surface dose.
• Custom molds may be
constructed of different materials
such as thermoplastic masks and
polymethyl methacrylate.

13. HOW TO MEASURE THE LESION
THICKNESS?
High-frequency conventional ultrasound (In the range of 10-50 MHz)

15. INTERSTITIAL BRACHYTHERAPY
• For lesions with depth >=5mm,
the superficial approach should
not be used because of an
unacceptably high skin-surface
dose.
• In this technique the catheters are
implanted within the tumor
<=10mm apart in one or more
planes depending of the volume
to be covered.
• Implants are generally performed
under local anesthesia with a
nerve block and sedation if
necessary.

16. DEFINING THE TARGET
Gross Tumor
Volume (GTV)
Clinical Target
Volume (CTV)
Planning Target
volume (PTV)
• GTV: volume discernible by either
imaging or clinical observation.
• CTV: expansion of the GTV to
account for subclinical
microscopic disease.
• Based on minimal surgical
recommendations
• BCC: 5mm
• SCC: 7-10mm
• PTV: expansion of the CTV for
geometric uncertainty due to
setup variation.

17. Patient Evaluation Defining the Target Volume
Choosing the appropriate
brachytherapy technique
Construction of a custom
mold or implanting the
catheters in the operating
room
CT Scan
Transferring the images to
the treatment planning
software
Treatment Planning Treatment Delivery
GENERAL SKIN
HDR
BRACHYTHERAPY
WORKFLOW

18. Orthovoltage RT
•Photoelectric effect
•For example in scalp or ear this leads to high
cartilage and bone doses
•Can be eliminated with heavy filtration
•No adjustment is available for curved surfaces
•Difficult to adjust penetration depth
•Results in high doses to deep normal tissues
•Lead skin collimation is required
•The construction of which can be messy and
uncomfortable for the patient
•Rarely available in radiation oncology departments
•Non-Invasive
Electrons
•Minimum field size: 4cm x 4cm
•When using this modality particularly in small fields,
output factors and percent depth dose (PDD)
measurements need to be performed.
•Challenging shielding
•Skin collimation with lead cutouts is required
•Large penumbra without skin collimation leads to
excessive normal tissue irradiation
•Beam constriction
•Results in more normal tissue irradiation because
larger field margin is required to cover the target
volume with 100% isodose line
•No adjustment for curved surfaces
•Difficult to adjust penetration depth
•High doses to deep tissues
•Bolus required
•To bring the 100% isodose line to the skin surface
•Lower Relative Biological Effectiveness (RBE)
compered to photons
•Higher doses are required to achieve the same
effect compared to photons
•Non-invasive
HDR Brachytherapy
•Lower doses to normal tissues. (Thanks to the
inverse square law)
•No Photoelectric effect
•Higher energy photons are used.
•Suitable for scalp or ear lesions
•Optimization (Thanks to stepping source
technology)
•Adjustment is available for curved surfaces (for
example fingers)
•Noninvasive in lesions with less than 5mm thickness
(Surface brachytherapy)
•Minimally invasive in thicker lesions (Interstitial
brachytherapy)
•Shorter treatment course (Hypofractionation and
acceleration)
•More convenient for the patient
WHY HDR BRACHYTHERAPY?

19. EVIDENCE FOR BRACHYTHERAPY

20. OUR EXPERIENCE

21. Pre-Treatment Catheter Implantation Treatment Plan (Axial)
1 week 1 Months 5 Months
9 Months
• History:
• 75 year old lady
• 1.5 cm right lower
eyelid lesion since
one year ago.
• Incisional biopsy
• Pathology:
Basosquamous
carcinoma
• Treatment:
• HDR interstitial
brachytherapy: 30 Gy
in 10 fractions twice
a day over 5 days.

22. Pre-Treatment Catheter Implantation Treatment Plan (Axial)
Treatment Plan (Sagittal) 1 Months 4 Months
6 Months
• History:
• 76 year old lady
• Ulcerated lesion on
lower lip since 6
months ago. (T3)
• Medically inoperable
• Incisional biopsy
• Pathology: SCC
• Treatment:
• HDR interstitial
brachytherapy: 40 Gy
in 10 fractions twice
a day over 5 days.

23. Pre-Treatment Debulking + Catheter Implantation Treatment Plan (Axial)
Treatment Plan (Sagittal) 1 Months 3 Months
• History:
• 22 year old male with history of xeroderma pigmentosum
• Painless skin nodule on the nose since 2 months ago
• Very rapid recurrence (within weeks) after two consecutive surgical
attempts
• Minimal response to chemotherapy
• Treatment:
• Gross tumor resection
• HDR interstitial
brachytherapy: 36 Gy in 12
fractions twice a day over 6
days.

24. Pre-Treatment Treatment Plan (Axial) Treatment Plan (Sagittal)
1 week 1.5 Months
• History:
• Ulcerated lesion on skin of the nose since 10 months
ago
• Incisional biopsy
• Pathology: Basosquamous carcinoma
• Treatment:
• HDR surface
brachytherapy + custom
mold: 40 Gy in 10 fractions
over 3.5 weeks.

25. THE ROLE OF BRACHYTHERAPY IN
THE SURGICAL MANAGEMENT OF
KELOIDS

26. ADJUVANT RADIATION THERAPY
• The recurrence rate is reportedly between 45% and
100% in cases treated with surgical excision alone.
• Combining surgical excision with adjuvant
radiotherapy can provide satisfactory results without
recurrence in up to 97% of cases.
• It is very important to initiate the treatment within 24
h of surgical resection.

27. EXCISION
IMPLANTATION OF
BRACHYTHERAPY CATHETER
BRACHYTHERAPY TECHNIQUE

28. ADVANTAGES OF BRACHYTHERAPY
OVER EXTERNAL BEAM RADIATION
THERAPY
• Direct visualization and placement of applicators into
the wound by the surgeon.
• Smaller clinical target volume (CTV) compared with
external beam radiation therapy → Less dose to
surrounding normal tissues → Lower risk of toxicity
including radiation induced malignancy