Guidelines and consensus

(Agent report, 2026-09-03. Reviewed by Kya at synthesis.)

Guidelines

• ESMO-EURACAN 2021 bone sarcoma CPG (Strauss, Ann Oncol; UCL Discovery author MS 10142480) VERBATIM: "For chordoma, preoperative core-needle biopsy is recommended, and the biopsy track needs to be included in the surgical resection. For skull base chordoma, preoperative biopsy is not recommended if the tumour cannot be reached easily or safely, or if there is a high risk of tumour cell seeding [V, C]." Brachyury "highly recommended [V, B]". PDC: brachyury+, INI1 loss; EZH2 inhibitors preliminary activity. ChT "inactive… not recommended [V, D]" for conventional. Particle therapy "treatment of choice [II, B]".
• Global Consensus on Primary Localized Chordoma, Radaelli/Stacchiotti/Gronchi, JAMA Oncol July 2026 (PMID 42424068), paywalled. Chordoma Foundation plain-language rendering (chordomafoundation.org/treatment-guidelines/new-diagnosis, accordion API 213125/213416) VERBATIM: "Biopsies in the skull base can be difficult and come with a risk of seeding. If your imaging strongly suggests chordoma, your doctors may recommend against having a biopsy before surgery. At experienced chordoma centers, testing a frozen sample during surgery can reliably rule out other conditions that would need different treatment. If your tumor does not have the usual chordoma appearance on scans or you may have poorly differentiated chordoma, a biopsy before surgery is recommended. If you have a biopsy, your surgeon should protect the nasal structures—such as the nasoseptal flap." Endoscopic seeding 1.1% vs transcranial 2.8-7.3%. RT alone "after a biopsy confirms the diagnosis". "Whenever possible, avoid having a biopsy outside of a referral center." PDC: "When PDC is confirmed, chemotherapy should be considered, possibly before surgery… response rates above 50%." PET at dx for PDC.
• Stacchiotti & Sommer Lancet Oncol 2015 (snippets only): "preoperative biopsy can be avoided in selected cases of suspected skull base chordoma if reaching the tumour site would be problematic or when the risk of unrecoverable seeding is felt to be high (V, C)".
• Stacchiotti 2017 recurrent chordoma (Ann Oncol, VERBATIM): "'Histological confirmation'… is needed when there is diagnostic uncertainty, or when there is the suspicion of tumor dedifferentiation (e.g. unusually fast growth)".
• NCCN patient guide 2026: biopsy confirms dx, at treating centre. Professional NCCN (snippet): needle biopsy not recommended for skull base (i.e. percutaneous), do at definitive centre.
• Chordoma Foundation diagnosis page VERBATIM: "definitive diagnosis can only be made by a pathologist"; skull base — "surgeon may opt for a biopsy during surgery" (frozen section); CF MAB: "chordoma patients under 35 years of age, or whose tumors are growing unusually fast, have their tumors tested for loss of INI1".
• NHS England PBT policy B01/P/d (adult skull base, Wayback): requires "appropriate and maximal safe resection", specialist unit, WHO PS 0-1, no mets, >=40% 5-yr survival expectation. No explicit "histology" word, but presupposes surgery. Snippet: centres won't accept without pre/post-op MRI.

Seeding

• Arnautovic & Al-Mefty 2001: 6/82 (7.3%) open era, 5/6 clival, mean age 34.
• Iloreta 2014 (PMC4242824): open 14/497 (2.8%); "Such contamination may occur… biopsy (needle or open), or during surgery".
• Fernandes Cabral/Gardner 2018: 2/173 EES (1.15%), aggressive biology.
• Barber/Gokaslan 2021 (PMC7961966): "diagnostic certainty requires histopathological evaluation. CT-guided needle biopsy… often recommended prior to definitive surgical intervention, as the differential… includes other entities for which treatment approaches may vary".
• NO published chordoma-specific biopsy-tract seeding rate for skull base found.
• Myneni 2025 Delphi: endoscopic endonasal whenever possible.

PDC

• Shih 2018 Mod Pathol: n=19, median age 11 (1-29); 53% skull base; brachyury 100%; worse OS; "should be treated aggressively with multimodality therapy".
• Harada 2024 Cureus: 32-yo male, clival PDC, cavernous sinus residual rapid growth, Ki-67 80%, died 7 months.
• Gounder 2026 Nat Commun tazemetostat basket: PDC 1/18 PR (6%).

  [Correction 7 Oct 2026: tazemetostat was withdrawn from all markets in March 2026 (Ipsen, after SYMPHONY-1 showed second blood cancers in 5.7% vs 0); trials and compassionate access stopped. PMID 42599162; research 12 A3. Read anything above or below about it as history, not an option.]

Synthesis

No guideline treats imaging as sufficient. Skull-base carve-out = get tissue AT resection (frozen section), not "treat without tissue"; conditional on typical imaging. Atypical imaging / possible PDC → 2026 consensus recommends biopsy BEFORE surgery (so PDC can get chemo first). The patient: atypical label, fast growth, age 33 (<35 trigger). Debate is only how/where — at an expert centre.