Table 4.

Numbers needed to treat (NNT)

N patients	treatment	estimated loco-reg RR (examples)	n R	n treated R	cure rate R (n)	survival (n)	NNT
100	OP only	10%	10	10	50% (5)	95% (95)	21
100	postop RT	5%	0.5	0.5	50% (0.25)	99.75% (99.75)
100 – 10 M+	OP only	10%	10	10	50% (5)	85% (85)	21
100 – 10 M+	postop RT	5%	0.5	0.5	50% (0.25)	89.75% (89.75)
100	OP only	30%	30	30	50% (15)	85% (85)	8
100	postop RT	15%	5	5	50% (2.5)	97.5% (97.5)
100 – 20 M+	OP only	30%	30	30	50% (15)	65% (65)	8
100 – 20 M+	postop RT	15%	5	5	50% (2.5)	77.5% (77.5)

Estimated numbers needed to treat (NNT), calculated for two populations with an estimated risk for recurrence (RR) of 10% (white) or 30% (grey), respectively (RR of 5% in postoperative IMRT cohorts has been derived from the own postoperative IMRT pT1-2 -fraction [16]). The calculations were performed each with and without considering the distant metastasis (M+) fraction; the percentage of M+ was based on the observed M+ rate in the own IMRT population; with higher local-regional risk (e.g. 30%), the M+ rate is usually also expected increasing (e.g. ~20%). This data suggest the generous indication for postoperative IMRT in initial situations with estimated RR exceeding ~10–15%.

n treated R: number of treated recurrences (idealised value, as not all rHNC patients can undergo salvage treatment with curative intention [6,8,29]).