Dosimetric rationale and early experience at UFPTI of thoracic proton therapy and chemotherapy in limited-stage small cell lung cancer

Figures & data

Table I. Baseline characteristics and staging of the six patients undergoing treatment.

Patient	Age at diagnosis (years)	Overall treatment time (days)^α	FEVI (l)	Comorbidities	Zubrod PS pretreatment	TNM stage	Location of primary tumor	Disease Status
1	75.9	41	2.4	Diabetes, peripheral vascular disease, esophageal stenosis	1	T1aN0M0	Left upper lobe	Died at 40 months of a fall. Disease-free at time of death
2	72.2	51	3.2	Sleep apnea	0	T3N3Mx*	Right hilar tumor with mediastinal, subcarinal, and cervical nodes	Died at 7.1 months from progressive disease
3	52.3	42	1.2	None	0	T3NOMx^†	Central/left hilar tumor involving main bronchus	Died at 12.0 months from progressive disease
4	70.4	22	1.4	None	0	T3N2M0	Right lower lobe. Mediastinal lymph nodes	Local recurrence at 14 months
5	68.6	51	3.3	Atrial fibrillation, pulmonary fibrosis	0	T1bN2M0	Left hilar tumor, mediastinal and hilar lymph nodes	Alive and disease-free at 12 months
6	61.8	49	Not available	Breast cancer, diabetes	0	T1aN2M0	Right upper lobe and mediastinal lymph nodes	Alive and disease-free at 12 months

*Multiple cervical lymph nodes on positron emission tomography scan and suspicious lesion in 8th rib and left iliac wing.

^†Isolated liver lesion seen suspicious for metastatic disease however remained stable throughout induction chemotherapy so patient treated sequentially.

^αOverall treatment time from date of first day of thoracic radiation to end of thoracic radiation treatment.

Figure 1. Colorwash isodose distribution for a proton plan. Gross tumor volume (GTV; dark green line), clinical target volume (CTV; outer red line), and the spinal cord (light green line) are outlined. A provides an axial view, B provides a coronal view, and C provides a sagittal view.

Table II. Baseline and acute toxicity maximum grading by Common Terminology Criteria for Adverse Events for six patients undergoing radical radiation treatment (4 concurrent; 2 sequential).

	Baseline toxicity grade (n = 6)				Acute toxicity grade (< 90 days) (n = 6)
Toxicity	0	1	2	3+	0	1	2	3+
Performance status	1	5	0	0	1	5	0	0
Fatigue	2	3	1	0	0	3	3	0
Dermatitis	6	0	0	0	1	3	2	0
Esophagitis	6	0	0	0	2	0	4	0
Dysphagia	0	5	1	0	3	2	1	0
Nausea	4	2	0	0	3	2	1	0
Vomiting	5	1	0	0	4	0	2	0
Anorexia	5	1	0	0	5	0	1	0
Cough	1	5	0	0	0	5	1	0
Dyspnea	1	5	0	0	3	3	0	0
Hypoxia	6	0	0	0	5	0	1	0
Pneumonitis	6	0	0	0	0	6	0	0

Table III. Dosimetric comparison of IMRT to Protons for 6 patients.

	IMRT		Protons		Difference (IMRT-PT)
	Median	(Range)	Median	(Range)	Median	(Range)
Lung
Lung mean	18.6 Gy	(11.6–23.5)	12.3 Gy	(7–18.5)	5 Gy	(2.9–7.9)
V5	57%	(33–86)	35%	(19–62)	17%	(13–43)
V10	45%	(21–65)	31%	(17–54)	10%	(2–22)
V20	35%	(18–39)	25%	(14–33)	6%	(1–15)
V30	24%	(16–30)	18%	(10–26)	6%	(1–10)
V40	17%	(12–25)	13%	(7–20)	4%	(2–8)
V50	12%	(7–20)	10%	(4–15)	3%	(0–6)
V60	8%	(5–13)	7%	(3–12)	2%	((–1)–2)
Esophagus
Esophagus mean	19.7 Gy	(6–35.5)	18.1 Gy	(.8–36)	2.6 Gy	((–.5)–9.9)
V5	40%	(25–78)	37%	(5–61)	10%	(2–32)
V10	36%	(19–72)	34%	(2–54)	9%	(0–32)
V20	31%	(12–63)	31%	(1–57)	5%	((–1)–27)
V30	28%	(6–59)	27%	(0–54)	4%	(0–17)
V40	25%	(3–58)	24%	(0–52)	3%	(0–13)
V50	22%	(0–53)	20%	(0–47)	1%	(0–6)
V60	15%	(0–38)	14%	(0–36)	1%	((–1)–3)

V= volume of organ receiving X dose.