Radiotherapy may have a role to play in both Stage I and Stage IIA/B seminoma.
Stage I Seminoma
Stage IA seminoma (with involvement of the testis only, and no lymphovascular or spermatic cord invasion) typically has a lymphatic drainage to the para-aortic (lumbar) nodes. About 15-20% of patients develop a relapse without further treatment. Radiotherapy offers an effective treatment to the highest risk area of relapse.
Patient Simulation and Setup
Position - Supine
Immobilisation - Wing board (arms) and a knee fix (legs).
Shielding - a clamshell shield should be used to protect the remaining testis. This has been shown to reduce dose to the testis, even when treatment is to the para-aortic nodes only.
Tattoos - at the level of the isocentre anteriorly and laterally
Planning
Clinical markup is not acceptable.
Field Based Planning
Older field based techniques used parallel opposed fields, with the isocentre at L2 midway between aorta and the inferior vena cava.
- The superior border is the space between T11 and T12
- The inferior border is the L5 and S1 disc space
- The ipsilateral border:
- For left sided testicular tumours, the left renal hilum is used; the other parts of the left kidney are shielded
- For right sided testicular tumours, the transverse processes of the lumbar vertebrae are used
- The contralateral border is the contralateral transverse processes from T11 to L5
These fields have been used for many years with proven benefits and are currently recommended by ESMO,
Volume Based Planning
There is minimal evidence on voluming of the para-aortic nodes, and even less as to the outcomes of voluming!
For stage I seminoma, the volumes to be contoured depend on the laterality of the seminoma.
For right testicular seminoma, the volumes to be contoured are:
- Paracaval nodes (aka right para-aortic nodes, right lumbar nodes)
- The space anterior to the psoas major, posterior to the peritoneum, lateral of the inferior vena cava and medial of the lateral border of psoas major.
- Pre-caval and pre-aortic nodes (aka pre-aortic nodes)
- The space anterior to the aorta/inferior vena cava, medial of their lateral boundaries, and posterior to the peritoneum / superior mesenteric artery.
- Interaortocaval nodes (aka 'interaortic' nodes)
- The volume bounded by the anterior borders of the inferior vena cava/aorta, laterally by their lateral borders, and posteriorly by the vertebral bodies of the spine.
For left testicular seminoma:
- Para-aortic nodes (aka left para-aortic nodes, left lumbar nodes)
- Pre-caval and pre-aortic nodes
- Interaortocaval nodes
- Left renal hilar nodes
Dose/Fractionation
20 Gy in 10 fractions is currently thought to be sufficient dose to eliminate microscopic disease in the para-aortic (lumbar) nodes.
Historically, doses of between 25 Gy / 15# and 35 Gy / 20 # have been used but do not seem to offer any benefit over 20 Gy / 10#
Treatment Toxicity
Early Effects
Most patients will develop:
- Fatigue
- Nausea (Grade 3 not uncommon)
- Manage with metoclopramide and ondansetron
- Diarrhoea
- Manage with diphenoxylate (Lomotil™)
- Mild skin reaction, perhaps with temporary epilation
- Patients should apply a non-metallic ointment to the treated skin
Cessation of treatment due to side effects is extremely rare.
Late Effects
The tissues of concern are:
- Skin
- The skin may develop telangiectasia or pigment changes rarely
- Upper Gastrointestinal
- There is an increased risk of gastro-oesophageal reflux disease and gastritis.
- Peptic ulcer is very rare with 20 Gy, but a large volume is treated
- Lower Gastrointestinal
- Very rare incidence of small bowel obstruction
- Cardiovascular
- Increased risk of death due to cardiac disease (doubled) after 15 years
- Possible risk of hypertension or renal disease due to renal artery stenosis
- Second malignancy
- Evidence of a twofold increase in second malignancy after seminoma treated with radiotherapy
- This is similar to the risk of chemotherapy
- The magnitude of this risk is unclear as patients have an increased risk of further malignancy because of their diagnosis regardless of treatment
- Second malignancies are dormant for at least 10 years before presenting
Stage II Seminoma
Radiotherapy is generally recommended for Stage IIA and IIB disease. Stage IIC disease is treated with chemotherapy according to the protocols for Stage III disease.
Aim of Treatment
Cure
- For Stage IIA disease, 5 year disease free survival is 95.3%
- For Stage IIB disease, 5 year disease free survival is 88.9%
Simulation
Immobilisation and marking up as per Stage I seminoma (above)
Planning
Clinical markup is not acceptable
Field Based Planning
Fields are 'dog-leg' or 'hockey stick' depending on which side of the Atlantic you are on
- Superior margin at T10-11
- Inferior margin at the superior border of the acetabulum
- Lateral margins of para-aortic fields along the transverse processes of thoracic/lumbar vertebrae
- The lateral margin of the iliac portion of the field follows an imaginary line from the lateral extent of the superior acetabulum to the lateral extent of the transverse process of L4
- The width of the iliac portion matches the width of the lumbar segment
Nodal disease is also covered with the field, with a 2 cm safety margin.
Volume Based Planning
There are no guidelines at all for voluming of Stage II seminoma. Dog leg fields are most commonly used.
GTV
The GTV includes all visible nodes on the CT scan.
CTV
The CTV includes the retroperitoneal nodal groups, the ipsilateral common/external iliac nodes, as well as a margin of 2 cm around the GTV
ITV
The ITV must take into account:
- Respiration (superior parts of the volume)
- Vessel pulsation (likely to be minimal)
PTV
The PTV includes a volume wide expansion of 0.5 - 0.7 cm to account for treatment setup errors
Dose/Fractionation
For Stage IIA disease, 30 Gy/15 # is commonly used. IIB disease may require dose up to 36 Gy/18#.
Treatment Toxicity
Toxicity is similar to the Stage I treatment, although the larger volume of treatment and higher dose results in an increased likelihood of both early and late toxicities.
