Oral cancers: Depth of invasion. Why it matters?

Presentation of oral cancers. Beware of lymphatics!

It predicts the risk of nodal involvement and recurrence. My senior colleagues were not aware of its value and I remember seeing a lot of ipsilateral neck nodal recurrences in early oral cancers after interstitial brachytherapy. A N0 neck after the USG wasn’t good enough and the “sub cm” nodes are almost always suspicious for micro metastases. Possibly, the digital PET CT “might” improve but pathological neck dissection has been hailed as a gold standard. However, the pathological criteria also varies across several institutions. It depends on the pathologist too-how assiduously they are going to dissect and study the nodal areas! I am not yet aware of the concept of “micro-metastases” and there’s an urgent unmet need to improve on IHC, for example, here.

We keep a cut off a 4 mm in our clinical practise and especially for tongue, we also irradiate the contralateral tongue. We haven’t seen any long-term morbidity, but there are rare contralateral failures too. By treating the neck to around 45-54Gy, we hardly exceed the mean Parotid dose to 20Gy and keep the skin dose below 5 mm to prevent any long-term morbidity. Tongue is notorious for extensive cross-connecting lymphatics.

We treat bilateral IB to level IV nodes. IA is addressed only if it is reaching the tip/dissection/floor of mouth involvement. IIA elimination is a bad idea because bulk of nodal involvement happens there. Level IV is “controversial” but extended neck IMRT’s with larger fields has now been made possible- most LINAC’s easily open up to 30×30 or 40×40 field size. There’s hardly any hotspot, or they are mostly acceptable for the anterior field set-ups. I don’t think that this should be a cause for stating it as an overtreatment because failures are more difficult to deal with. (Poor surgical candidates and lack of effective salvage chemotherapy regimens)

Stock image- only for illustration.

I stumbled on an excellent paper earlier today and it was worth annotation/summary. It is a basic paper, devoid of fancy jargon and addresses a key component for decision-making.

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The annotations are in the embedded word file below:

I have highlighted the most important takeaways from the paper. I hope you find it useful! Please do share it widely.