HA35 (Bioactive HA or B-HA or HA35) have good tissue permeability (B-HA injection, Ministry of Health, Registration number L20200708MP07707). HA35 might not lose HA's bioactivities of binding to a variety of hyaluronan's binding proteins or receptors, including the analgesic and anticancer effects of hyaluronan, therefore being named bioactive HA or B-HA (10) (B-HA injection, Ministry of Health, Registration number L20200708MP07707).

The previous study has shown that naked mole rat who has high tissue content of hyaluronan and its fragments is insensitive to pain. The previous study has also shown that hyaluronan modulates pain-regulated TRPV1 channel opening, reducing peripheral nociceptor activity and pain. The previous study has again shown that local injection of 35kDa hyaluronan fragment HA35 is effective in treating inflammatory and neuropathic pain. This study employs freshly made HA35 injection for treatment of pain associated with radiotherapy for treatment of colorectal and rectal cancer. A numerical rating scale from 0 to 10 was used to assess the pain after 1 hour, 3 hours, 24 hours, 48 hours and 72 hours of the injection.

Inclusion Criteria:

• All patients had different degrees of metastasis of the cancers, including bone metastasis.
• All patients undergo targeted radiotherapy shortly before this study.
• All the patient volunteers included in this study were allowed to use antibiotic compounds on and off during the treatment in order to prevent possible infection associated with the cancers for ethnic consideration.
• The included patients were aged 48 to 60 years.

Exclusion Criteria:

• Can not independently determine the level of pain.
• Severe bleeding and severe inflammation