Interesting points here but there are several pertinent issues here:
1) Lymphatics extend from T11 to L4 but are concentrated at Renal Hila due to common embryological origin.
Primary landing site for right side is inter-aortocaval area at right hilum; for left side it is peri-aortic area at left hilum.
2) Invasion of epididymis and spermatic cord spreads to distal external iliac and obturator nodes. Scrotal violation leads to inguinal metastasis.
3) Seminoma is of three types:
a) Classical
b) Anaplastic
c) Spermatocytic.
The important clinical aspect of spermatocytic seminoma is that once orchiectomy has been done, it is curative.
Anaplastic variant presents in higher stage; but not a worse prognosis.
4) A negative FDG-PET alone has value in exclusion of the disease.
5) Stage I seminoma has 20% risk of occult disease.
6) Stage I includes all T sub stages; is node negative and barring IS, with negative serum markers.
7) Current recommendations have pooled in heterogeneous patients with mixed up histologies.
8) High risk factors include T > 4 cm and rete testis invasion.
After considering these facts, it becomes easy to analyze the existing data and the evidence cited.
I would only argue against the field reduction because if you look closely, bulk of patients had T<4 cm and there were no adverse factors in majority of them.
Hence it becomes imperative to consider the paper in the light of above evidence.
Long term results of irradiation (In the complete paper, they also have patients segregated by histology).
I quote selectively:
Based on the Radiation Therapy Oncology Group scoring criteria, acute toxicity was limited to grade I gastrointestinal (GI) toxicity in 25 patients (35%) and grade II GI toxicity in 7 patients (10%). Acute toxicity was not recorded in 4 patients (5%). The most frequent acute toxicities were nausea and vomiting (30 patients; 94%). Diarrhea occurred in 3 patients (10%) and epigastric discomfort in 1 patient (3%). These symptoms were self-limiting or well controlled with medication. At the time of this report, no late toxicity has been observed. There is no reported peptic ulcer disease or second malignancies within the treatment field.
Invidualized treatment for seminoma
The primary target coverage was dosimetric coverage of inferior vena cava and aorta (as mentioned in the lymph node spread).
I quote:
A 1.4cm expansion was generated in the anterior, lateral, inferior and superior directions around the combined aorta and IVC volume, and similarly for the renal vein except for no expansion laterally. A further 1cm expansion was added to generate the field margins.
One more question. Has any consideration been given to the pulsation of the vessels?
Hence, I would strongly suggest that field reduction should not be done given the risk of possible sparing of the disease. Current literature recommends 1.25 Gy per # and almost minimal long term outcomes.
Only and only if the pathology is favorable, should the field reduction be attempted (which means that you should have a blind faith in your pathologist).
