He was treated with definitive RT alone using IMRT. The primary tumor received 70 Gy in 35 fractions. Entire larynx and low risk neck including bilateral levels III-IV, VI and superior mediastinum received 56 Gy during that time.

For subglottic involvement, always treat level VI and consider superior mediastinum (Eisbruch et al Sem Rad Onc 2002)
Always cover LN levels III-IV bilaterally, and add level II for advanced T stage or N+.
Definitive RT dose and coverage (extrapolated from 3D-CRT* in Paisley et al IJROBP 2002):

CTV70 = GTV + 5-10mm, carving out bone/air.
CTV60-63 = high risk elective, consider N+ neck plus one level above/below
CTV54-56* = low risk elective, including entire larynx (top thyroid notch to bottom cricoid), paraglottic and pre-epiglottic space, pyriform sinuses, vallecula, as well as first echelon nodes (see above).

*This patient received fiberoptic laryngoscopy and proximal esophagogastroduodenoscopy confirming no hypopharyngeal involvement

*Paisley et al treated 42 patients (T1-T4N0) with 50-52Gy/20 to primary and first echelon nodes (EQD2 55Gy). Nodal involvement is low for subglottic primaries so 54-56Gy to N0 neck is reasonable.

Distribution of larynx cancer:

supraglottic = 30-35%
glottic = 60-65%
subglottic = <3%

Subglottis:

Inferior boundary: lower border of cricoid cartilage

Superior booundary: 5mm below free edge of TVCs (controversial)

Per NCCN (1.2015), "Subglottic cancer is not discussed because it is so uncommon."
Largest study for subglottic cancer is from SEER (Marchiano et al Otolaryngol Head Neck Surg 2016) which showed patients present with advanced local (58% T3-T4) but not regional (75% are N0) or distant (95% are M0) disease. Still 5-yr DSS is only 55% regardless of surgery, RT or both.
General management:

Stage I-II: RT alone for larynx preservation
Stage III-IV: Surgery +/- post-op RT (esp N+)