Table 3.

Risk of Stomach Cancer After HL in Relation to Procarbazine and Radiation Dose to Stomach

Characteristic		Cases (n = 89)		Controls (n = 190)		OR	95% CI‡	Pinteraction§
Radiation Dose (Gy)*	Procarbazine dose (mg/m2)†	No.	%‡	No.	%‡
All patients								< .001
< 25	< 5,600	25	29	94	52	1.0	Referent
≥ 25	< 5,600	23	26	41	23	2.8	1.3 to 6.4
< 25	≥ 5,600	14	16	44	24	1.2	0.5 to 2.7
≥ 25	≥ 5,600	25	29	2	1	77.5	14.7 to 1,452
Age at HL diagnosis < 30 years								.06
< 25	< 5,600	6	15	44	49	1.0	Referent
≥ 25	< 5,600	13	33	27	30	7.1	1.9 to 36.8‖
< 25	≥ 5,600	6	15	17	19	1.9	0.5 to 7.3
≥ 25	≥ 5,600	15	36	2	2	124	15.8 to 3,169
Age at HL diagnosis ≥ 30 years								.002
< 25	< 5,600	19	40	50	55	1.0	Referent
≥ 25	< 5,600	10	21	14	15	1.5	0.5 to 4.2‖
< 25	≥ 5,600	8	17	27	30	0.8	0.3 to 2.4
≥ 25	≥ 5,600	10	21	0	0	∞	8.8 to ∞
Age at stomach cancer diagnosis < 50 years								.13
< 25	< 5,600	5	13	44	50	1.0	Referent
≥ 25	< 5,600	13	33	26	30	8.6	2.3 to 43.9‖
< 25	≥ 5,600	7	18	16	18	2.9	0.8 to 11.6
≥ 25	≥ 5,600	15	38	2	2	151	17.6 to 4,264
Age at stomach cancer diagnosis ≥ 50 years								< .001
< 25	< 5,600	20	43	50	54	1.0	Referent
≥ 25	< 5,600	10	21	15	16	1.3	0.4 to 3.6‖
< 25	≥ 5,600	7	15	28	30	0.6	0.2 to 1.7
≥ 25	≥ 5,600	10	21	0	0	∞	8.9 to ∞
Interval from HL to stomach cancer < 15 years								.003
< 25	< 5,600	15	37	42	55	1.0	Referent
≥ 25	< 5,600	6	15	13	17	1.5	0.4 to 5.6‖
< 25	≥ 5,600	9	22	22	29	1.2	0.4 to 3.9
≥ 25	≥ 5,600	11	27	0	0	∞	10.0 to ∞
Interval from HL to stomach cancer ≥ 15 years								.02
< 25	< 5,600	10	22	52	50	1.0	Referent
≥ 25	< 5,600	17	37	28	27	4.2	1.4 to 14.1‖
< 25	≥ 5,600	5	11	22	21	1.2	0.3 to 4.2
≥ 25	≥ 5,600	14	30	2	2	67.0	10.5 to 1,407

Abbreviations: ABV, doxorubicin, bleomycin, vinblastine; BEACOPP, bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, prednisone; HL, Hodgkin lymphoma; OR, odds ratio.

^*Radiation dose was estimated to the specific site of the stomach tumor (matched location for controls).

^†Assuming a procarbazine dose of 1,400 mg/m² per cycle (14 days × 100 mg/m² per day), ≥ 5,600 mg/m² corresponds to ≥ four cycles of MOPP or MOPP-like regimens. Other protocols (eg, MOPP-ABV, BEACOPP) include a procarbazine dose of 700 mg/m² per cycle.

^‡ORs and 95% CIs were adjusted for receipt of any dacarbazine and unknown radiation dose. Patients with unknown radiation dose were excluded from percentages.

^§P_interaction between irradiation and procarbazine was calculated using a likelihood ratio test under the multiplicative model.

^‖Stomach cancer risk among patients who received radiation to stomach tumor site ≥ 25 Gy but procarbazine < 5,600 mg/m² was compared between patient subgroups using a likelihood ratio test. Age at HL diagnosis: OR < 30, 7.1 v OR ≥ 30, 1.5; P_homogeneity = .11. Age at stomach cancer diagnosis: OR < 50, 8.6 v OR ≥ 50, 1.3; P_homogeneity = .05. Interval from HL to stomach cancer: OR < 15, 4.2 v OR ≥ 15, 1.5; P_homogeneity = .30.