Cancer cells on the move: in-transit melanoma metastases

This study explored the occurrence, characteristics, and survival outcomes of melanomas with in-transit metastasis.

An in-transit metastasis in melanoma refers to the spread of cancer cells through a lymph vessel to a nearby location. This can indicate a worse prognosis, as the melanoma could then spread to the lymph nodes and/or other areas of the body. Patients with Stage 3B disease (with in-transit metastasis but no lymph node involvement) have a 69% 5-year survival rate, compared to 46% for Stage 3C (with lymph node involvement). Patients with only a metastasis to the skin have a 60.1% 5-year survival rate, while for those with both skin and lymph node metastasis that rate is 36.3%.

Previous studies have found the occurrence of in-transit metastasis for melanoma patients to be 3.6%–7.0%. In order to determine prognosis for a patient, proper staging is essential, therefore a better understanding of in-transit metastasis is needed.

This study explored the occurrence, characteristics, and survival outcomes of melanoma patients with in-transit metastasis. This study examined the records of 505 melanoma patients with in-transit metastasis. The average follow-up times were 40.6 months from the original diagnosis and 14.5 months from the in-transit metastasis diagnosis. The average time from diagnosis to in-transit metastasis was 17.9 months.

Primary melanomas that occurred on the head or neck progressed to in-transit metastasis faster (average 11.2 months) than those on the limbs or trunk (18.6–19.2 months). At the time of in-transit metastasis diagnosis, 274 patients were restaged to Stage 3B melanoma, 183 were restaged to Stage 3C, and 48 were restaged to Stage 4 (spread to distant sites). For patients who underwent sentinel node biopsy (a biopsy of the lymph node nearest the original tumor), the rates of in-transit metastasis were 4.7% for those with a negative biopsy, and 21.6% for positive.

The average 5-year overall survival rate for those with in-transit metastasis was 36%, and the 10-year survival rate was 30%. For those patients without lymph node involvement the 5-year survival rate was 44.2%, compared to 19% for those with lymph node involvement. The 5-year melanoma-specific survival rate (a measure of death specifically due to melanoma) was 44.2% for those without ulceration of the melanoma (a breakdown of the skin surrounding the tumor), and 23% for those with ulceration.

Lymph node dissection (removal of lymph nodes) did not affect survival times in patients with in-transit metastasis.

This study concluded that in-transit metastasis indicates the progression of melanoma and is associated with more negative outcomes; therefore the diagnosis of in-transit metastasis in melanoma patients can assist in proper staging and prognosis.