The NIH have been testing Calendula for the past 30 years. They have found that it has a marked effect on the cancer cells and tumors, and especially good for recovery after conventional cancer treatments.

They did a tincture with alcohol, a double extraction of alcohol and water and a tea with flowers only. They found that the tincture and the double extraction has stronger properties than a tea alone. Since no alternative medicine had ever used roots for a cure they highly suggested that testing should be done on a root and flower extraction. They  did a tea that was treated with lasers to see if it increased the effectiveness and surprise it did. They did an extraction with Heptane which is used in various products such as engine fluid, glue, and cleaners for home and industrial use.

The extractions were tested and they were found to be anti-inflammatory, anti-edematous(helps with edema),anti-oxidant, anti-fungal, anti-bacterial, anti-viral,anti-HIV, immunostimulant, genoprotective( protects against genetic damage) and anti-metastatic. 

The extraction also contained active ingredients like metabolites, and Lutein, along with various,, flavanoids, terpenoids, carotenoids, amino acids and lipids.

The extractions were tested on breast, melanoma, leukemia, non small cell lung cancer, colon, central nervous system cancers, ovarian, renal, and prostrate cancer cells in mice. The administration of the extraction showed a slow down of growth of the cancer cells in all but two of the cancer cells tested. They found that within 24 hours that cell growth of cancer and tumors was significantly smaller than untreated cells and that after 48 hours it continued to kill cells. The best results were with Breast, Neck Head, and Skin cancers and tumors.

Testing also showed that Calendula is a great herb for follow up care after chemotherapy and radiation. It has a regenerative property on repairing skin cells, and protecting the genetic code in the cells. 

Based on this paper and its recommendations a Calendula tincture and salve are good options for Breast, Neck, Head and skin cancers. The salve is even better for cellular repair after chemo or radiation.