For low rectal adenocarcinoma that extends to the anus through the internal sphincter muscle, would you recommend neoadjuvant therapy in a patient who will undergo APR?

Yes, since the margin is positive and local recurrence rates are high for low rectal cancer patients such as this, they should be treated with neoadjuvant chemoradiation including the inguinals with IMRT.

Yes, caudal extension to the internal sphincter is typically considered T3. Even in the absence of external sphincter involvement, assessment of the intersphincteric space can be useful for assessing downstaging and for subsequent surgical considerations. And for the reasons Dr. @Dr. First Last ment...