Figure 2. Pre-processing of the survival data.

Star, number in the star, solid dot, and hollow dot represent tumor, tumor sequence number, death, and censored, respectively. Tumor 1 and 2 are non-synchronous MPMs, and tumor 3 and 4 are synchronous MPMs. Patient A is divided into three patients, the first one starts from the occurrence of tumor 1 and ends up at the occurrence of tumor 2; the second one starts from the occurrence of tumor 2 and ends up at the occurrence of tumor 3; the last one starts from the occurrence of tumor 3 and ends up until death. MPM, multiple primary cutaneous melanoma.