Definition: Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.
Input: Abstract: Two hundred ninety-seven long-term photochemotherapy (PUVA)-treated patients from an original cohort of 418 subjects reported in 1980 were reevaluated in a second follow-up in order to determine the risk of tumor development under long-term PUVA. Within an observation period of up to 8 years (mean, 63.1 months) six patients with squamous cell carcinomas and three with basal cell carcinomas were observed. Eight of the nine tumor patients had been exposed to potential carcinogens such as arsenic and/or ionizing radiation prior to PUVA treatment. Five with squamous cell carcinomas were skin type I or II; in four of the six patients with squamous cell carcinomas the tumors were located on unexposed skin areas. The mean cumulative ultraviolet A (UVA) dose in three of the six squamous cell carcinoma patients was three times as high as that in the group of nontumor patients. The other three squamous cell carcinoma patients had lower mean doses than nontumor patients, as did the three patients with basal cell carcinomas. Although the cumulative UVA dose may eventually turn out to be relevant for PUVA carcinogenesis, our present data do not sufficiently substantiate a correlation between cumulative UVA dose and squamous cell carcinoma formation in PUVA-treated patients. This report confirms that previous exposure to carcinogens appears to be the most important factor for nonmelanoma skin tumor formation in long-term PUVA patients.

Nonmelanoma skin tumors in long-term photochemotherapy treatment of psoriasis. An 8-year follow-up study.