Conventional RT and surgery
A number of large institutional series have shown excellent local control rates for tonsil cancers after conventional fractionated radiation alone (1.8-2Gy/fraction) of 80-90% for T1-2 lesions.r
The Danish RCT by Overgaard et al. 2003 of 5 vs 6 conventional treatments per week demonstrated that radiotherapy can be successfully accelerated.r These results were confirmed by the IAEA-ACC Study.r Five-year loco-regional control rates (70% vs 60%; p=0.0005) and primary tumour control (76% vs 64%; p=0.0001) were improved but not neck control.r
Figure 1.0. Locoregional control rates of 5 vs 6 conventional treatments per week.r
© Lancet 2003r
The incidence of HPV related oropharyneal SCC is increasing. These patients have a different epidemiological profile to HPV unrelated H&N SCC. HPV-positive tumours carry a better prognosis than HPV-negative tumours.rr This can be partially mitigated by their smoking history.r
Ang et al. (RTOG 0129) assessing 323 patients (63.8% of patients HPV positive tumours) with oropharyngeal cancer reported improved 3 year overall survival rates of 82.4% vs 57.1% (p<0.001) for HPV positive vs HPV negative tumours.r After adjustment for age, race, tumour and nodal stage, tobacco exposure and treatment assignment, these patients had a 58% reduction in the risk of death (HR 0.42; 95% CI, 0.27 to 0.66).
The phase III trial by Rischin et al. also demonstrated the prognostic significance of p16 and HPV status in patients treated with cisplatin-based chemoradiotherapy.r
Treatment de-escalation in HPV positive patients remains an active area of interest with several international trials underway, however, there is no evidence to currently support treatment de-escalation in these patients and this is not endorsed by this reference committee.
Unilateral treatment of the neck is the preferred treatment in patients with T1-2N1 (AJCC 7th edition, i.e. node negative or those with a solitary lymph node <3cm)r well-lateralised tonsillar tumours (i.e. no soft palate or base of tongue extension).r Unilateral treatment may be appropriate for, but should be used selectively in patients with: (1) <1cm extension of the tonsillar tumour onto either the soft palate or base of tongue; and/or (2) a single lymph node >3cm but <6cm, (AJCC 7th edition N2a)r or multiple small volume lymph nodes (AJCC 7th edition N2b)r. With the exception of the inclusion of N2b, this approach is endorsed by the ASTRO consensus guidelines.r
The decision of treating unilaterally should be made on anatomical staging and lateralisation, not on p16/HPV status.
The Princess Margaret Hospital recently updated their results of unilateral treatment in well lateralised tonsil tumours in the HPV era.r Unilateral treatment was administered to 102 patients, and HPV status was known in 96 (62 HPV+, 34 HPV-). Only 8 N2b patients were treated unilaterally and all had low volume disease (≤3 lymph node metastases). Only two patients from the unilateral group received concurrent chemotherapy. Contralateral neck failure occurred in only two patients, one HPV+ and HPV-, and both were successfully salvaged.
Other series similarly low rates of contralateral neck failure, and a contemporary review of published studies reporting unilateral treatment outcomes for oropharyngeal cancers reports low rates of contralateral neck failure, although selection bias in the N2+ group is highly likely and should be interpreted with caution.rr
Figure 2.0. Schematic diagram depicting “very-lateralized” primary suitable for consideration of ipsilateral radiation therapy.r