Further to the above, the thick "rope" mucus is from damage over time to the salivary glands from chemo, and radiation, which causes xerostomia, dry mouth, which causes mucositus, a painful inflammation, and ulceration of the mucus lining, which occurs in 80 percent of patients. When chemo stops, the saliva will improve, but not always from radiation, and depends on the radiation dosage to the parotid gland if it was radiated, which produces about 60-65 percent saliva that is all watery saliva, 20-30 percent is by the submambular and 2-5 percent by sublingual glands both which produce a mixture of watery, and mostly thick saliva, which is yellowish, so you may see a color change in the mucus too. Radiation damage is mostly to the thin watery saliva (parotid gland) and thick mucus is less involved. When these glands start recovering, even if the parotid gland is fully damaged, usually after 26Gy, the others may start producing more saliva to compensate the loss.