Multiple independent primary cancers do not adversely affect survival of the lung cancer patient

Diagnosis of multiple independent primary cancers is increasing in many settings. Objectives of this study were to analyze clinical characteristics, organ location, and prognosis associated with the presentation of multiple independent primaries when a lung cancer is involved.

We analyzed all patients with a histology-proven diagnosis of lung cancer registered from January 1990 to December 2004 at the Tumor Registry of the Hospital del Mar, Barcelona. We compared 1686 patients presenting a lung cancer as unique primary versus 228 patients presenting a lung cancer and another independent primary. Cofactors included age, sex, smoking habit, lung cancer histology and stage, type and intention of treatment, organ location of the other cancer, and survival from the date of lung cancer diagnosis.

Seventy percent of the other cancers were tobacco-related. Independent risk factors of cancer multiplicity were smoking (OR: 3.99; 95% CI: 1.4-11.2), lung cancer stages I (OR: 1.84; 95% CI: 1.2-2.9) and II (OR: 3.25; 95% CI: 1.7-6.3), and older age (OR: 3.11; 95% CI: 1.9-5.1). Once adjusted by age and sex, the main determinant of survival was lung cancer stage rather than cancer multiplicity. However, patients with multiple cancers presented a slightly better survival than patients with a lung cancer as unique primary. When analyzed by subgroups, survival was higher in patients with the lung cancer first (HR: 0.44; 95% CI: 0.24-0.80), and in patients with the other cancer first (HR: 0.80; 95% CI: 0.65-0.99), but it was not different in the patients with a lung cancer and a synchronous other cancer (HR: 0.80; 95% CI: 0.52-1.15).

The risk of developing a second independent cancer was strongly associated with tobacco smoking. Cancer multiplicity was not associated with a worse prognosis. As a consequence, when a first primary tobacco-related cancer is treated with curative intention, patients should be closely followed up for an early diagnosis of a possible new independent cancer; and if diagnosed, treatment to cure should be considered as the first option.