Table 1.

Dosimetric predictors of xerostomia.

Investigator	Patients (n)/follow-up (mo)	Total prescribed target dose (Gy)*	“Functional” endpoints assessed	Dose–volume parameters
				Unstimulated	Stimulated
Blanco et al. (6), 2005	55/6; 29/12	50–71†	Stimulated saliva flow‡		Mean dose <25.8 Gy§
Eisbruch et al. (7), 1999	88/1–12	58–72	Saliva flow, stimulated and unstimulated	Mean dose ≤22–25 Gy¶ V15 <66% V30 <43% V45 <26%	Mean dose ≤25–26 Gy‖ V15 <67% V30 <45% V45 <24%
Li et al. (9), 2007	142/1–24	60–75	Saliva flow; stimulated and unstimulated#	Mean dose <25–30 Gy	Mean dose <25–30 Gy
Maes et al. (8), 2002	39/1–4	66–70**	SEF††; stimulated flow, 99mTc-pertechnetate scintigraphy		Mean dose ≤20 Gy‡‡

Abbreviations: V_x = percentage of gland volume receiving >x Gy; ^99mTc = technetium-99 m; SEF = salivary excretion fraction; RT = radiotherapy.

^*All ≈1.8–2.0 Gy/fraction.

^†1.5–1.8-Gy fractions in low-risk target volumes for intensity-modulated radiotherapy patients.

^‡Grade 4 xerostomia using subjective, objective, management, analytic (SOMA) method; ≤25% of pretreatment level defined as event.

^§Mean dose to single parotid gland to reduce stimulated salivary flow from that gland to <25% of pre-RT saliva.

^¶24 Gy at 1 and 3 months, 22 Gy at 6 months, and 25 Gy at 12 months; threshold dose defined as mean dose above which saliva production appeared to abruptly approach 0.

^‖26 Gy at 1, 3, and 6 months, 25 Gy at 12 months; threshold dose defined as mean dose above which saliva production appeared to abruptly approach 0.

^#Predictors defined as mean doses below which efficient function recovery occurs with time, returning to pre-RT levels by 24 months.

^**66–70 Gy to primary tumor and pathologic nodes; 50–70 Gy to tumor bed if postoperatively; 46–50 Gy to elective nodes.

^††SEF loss ≥50% defined as event.

^‡‡Corresponded to probability of 70% that SEF loss was <50%.