Clinical case 1

Yes, I would recommend to go ahead with OTC on her -- it is a consideration of whether she should have both ovaries removed or only one. I am not aware of anyone having taken out both ovaries worldwide -- this most likely reflects that OTC has been considered experimental and difficulties on estimating whether there will be any residual activity in the in situ ovary following chemo. But if the planned chemotherapy is strong and the probability of infertility is estimated to be very high (>90%) it may be discussed with the family.

Anyway, this is a perfect case for doing IVM alongside cortex freezing, she should have many immature oocytes.

No scans or reports to review and no pathology report, however, if this is a pelvic Ewings as they are assuming - then OTC from one ovary is certainly indicated. Preferably from the side nearest the tumour, indeed no harm in doing an oophorectomy from the ovary most likely to be within the irradiation field. It is important to examine a small part of the excised ovary for evidence of disease contamination (Sørensen et al. 2014).

Bilateral oophorectomy is not indicated, and I would try to avoid surgical exploration of the other ovary. The planned chemotherapy for Ewings sarcoma is usually high risk for POI - and local high dose radiotherapy to the primary and maybe to sites of metastatic involvement is usually indicated. An understanding of the dose to be received by the ovary furthest away from the radiation field allows an estimate of the age at which POI will occur. This is helpful for counselling the patient. (Kelsey TW et al 2022).

One further consideration is there may be a strong case for Proton radiotherapy rather than Photon radiotherapy if it is available as discussed in (Kelsey TW et al, 2022). For a general review and evidence-based guidelines see (Mulder et al, 2021).

References

1. Kelsey TW, et al. A predictive model of the effect of therapeutic radiation on the human ovary. PLoS One. 2022;17(11):e0277052. PMID: 36399448;
2. Mulder RL, et al; PanCareLIFE Consortium. Fertility preservation for female patients with childhood, adolescent, and young adult cancer: recommendations from the PanCareLIFE Consortium and the International Late Effects of Childhood Cancer Guideline Harmonization Group. Lancet Oncol. 2021;22(2):e45-e56. PMID: 33539753.
3. Sørensen SD, et al. Safety considerations for transplanting cryopreserved ovarian tissue to restore fertility in female patients who have recovered from Ewing's sarcoma. Future Oncol. 2014;10:277-83. PMID: 24490613.