How would you manage a patient with stage I pure seminoma diagnosed incidentally after transscrotal orchiectomy?

For me, I would want to know the T stage and some other specifics about the case. The only option that I would not consider would be radiation therapy due to potential disruption of the usual dissemination paths. Surveillance with abdominal/pelvic CT scans would still be expected to catch relapse early using a standard surveillance protocol. Depending on the specifics of the tumor, the risk of relapse may be 30% or higher. Two doses of carboplatin reduces that risk to about 2% (when using carbo, I prefer two doses because a single cycle only lowers the relapse rate to 5% or 6%).  Carboplatin is extremely well tolerated in the short run but the risks of late complications (cardiovascular disease, secondary malignancies) are unknown. Platinum chemotherapy has been associated with an increased risk of leukemia and other cancers. Whether the doses used for stage I seminoma significantly elevate the risk of second cancers or other significant diseases remains unknown. Patients who relapse with stage 1 disease are treated with either radiation therapy or BEP, both of which have known late effects and complications, including an increased incidence of secondary malignancies, so choosing surveillance does not eliminate this concern. Balancing the risks/benefits of a possibly risky treatment now against possibly needing a proven-risky treatment later is not simple. What seems best to the clinician is not always what seems best to the patient.

Using a shared-decision-making approach,  I aim to include the patient in the decision-making process and, weighing the pros and cons of each option, make the decision that is best for that patient. For some, the peace of mind of 2% risk of relapse is worth the risk that two doses of carboplatin may result in late complications. A large majority of my patients prefer surveillance. 

It would not change my recommendation for observation.  My biggest objection to adjuvant carboplatin is that it isn't very good therapy and doesn't change the primary challenge of active surveillance which is the requirement for continued abdominal imaging.  I would observe this patient and watch the affected scrotum closely.  Overall I think he has a low chance of recurrence.

I would not change the recommendation for active surveillence as overall risk is still low and we know that active surveillence for stage 1 disease is preferred option to decrease risk of acute and long term complications and salvage rates are very high at recurrences